DESC:FIELD

The present disclosure relates to a freestanding monolithic protected lithium cassette anode for a Lithium metal-based secondary electrochemical cell and a method for its fabrication as a cassette. More specifically, the present disclosure relates to a replaceable monolithic protected lithium cassette anode for electrochemical energy storage devices such as lithium metal-based all-solid-state rechargeable battery systems, Lithium metal/Sulphur (Li-S) batteries and Li-air rechargeable batteries, and lithium-air semi fuel cells.

DEFINITION

As used in the present disclosure, the following terms are generally intended to have the meaning as set forth below, except to the extent that the context in which they are used indicates otherwise.

“Electrochemical cell” refers to a device that consists of two basic electrodes, a positive electrode (cathode) and a negative electrode (anode), along with an electrolyte. The chemical reactions that occur in the cell facilitate the conversion of chemical energy into electrical energy.

“Monolithic protected lithium cassette anode” refers to a “layered anode architecture”, wherein several layers of conducting and protective materials are used to form the anode according to the teachings of the present invention, wherein these layers may be of same dimension or of different dimensions, hereinafter called as monolithic PLC.

“Lithium Ion Conducting Glass-Ceramics (LICGC)” refers to a solid-state electrolyte which is used as a separator in an electrochemical system (a solid-state battery for instance) namely LICGC™ AG-01 (Ohara Inc, Japan). The LICGC consists of a NASICON type crystal structure whose solid solution composition is known to be (Li1+x+3zAlx(Ti,Ge)2-xSi3zP3-zO15), where 2 > x > 0 and 2 > z > 0 that imparts unique properties to the LICGC such as high lithium-ion conductivity of the order of 3x10-4 S/cm at 25 °C, water resistance, acid resistance, dust and grease repellency, stability in air, bending strength of 140 N/mm2, Knoop hardness of Hk 590, specific gravity of 3.05, and coefficient of thermal expansion of 10-7/K. [Ref: https://www.ohara-inc.co.jp/en/product/electronics/dl/OHARA%20Presentation%20140203.pdf]

Li1+x AlxTi2–x(PO4)3 (where 0.0=x =1.0) (LATP) is yet another NASICON-type solid electrolyte. The ionic conductivity of a typical LATP composition Li1.3Al0.3Ti1.7(PO4)3 falls within a range of 1 to 5x10-4 S/cm at room temperature [Ref: Aono, H. Ionic conductivity of the lithium titanium phosphate Li1+x AlxTi2–x(PO4)3, M=Al, Sc, Y, and La) systems. J. Electrochem. Soc. 1989, 136, 590–591.]

BACKGROUND

The background information herein below relates to the present disclosure but is not necessarily prior art.

A basic electrochemical battery cell usually includes two oppositely charged electrodes separated by a separator material sandwiched between these electrodes. One of these two electrodes is often referred to as a counter electrode of the other. In the context of Li-ion rechargeable cells, it is customary to denote the cathode as a positive electrode and the anode as a negative electrode.

The evolution of rechargeable battery types and their composition from generation one to generation four is illustrated as a prior art (100) in Fig. 1 of the accompanying drawings and provided herein below Table 1.

Table 1: Evolution of Lithium containing rechargeable battery types
Generation First (101) Second (102) Third (103) Fourth (104)
Anode a thick metallic lithium (Li) (1011) graphitic carbon (1021) included a silicon (Si) composite (1031) ultra-thin lithium (Li) metal (1041)
Cathode titanium disulfide (TiS2) cathode (1013) LiCoO2; (LiFePO4/C); lithium nickel cobalt manganese oxide (LiNixCoyMn(1-x-y)O2) for e.g. NMC333 (154.8 mAh/g between 2.8-4.25V), NMC532 (166.9 mAh/g between 2.8-4.25), NMC 622 (175.8 mAh/g between 2.8-4.25V) and NMC811 (203.4 mAh/g at 4.3V) (1023) NMC (NCM) – lithium nickel cobalt manganese oxide (LiNiCoMnO2);

lithium nickel cobalt aluminium oxide (LiNiCoAlO2) (1033)

nickel-rich NMC or Sulphur (S) (1043)

Separator micro-porous separator (polypropylene) (1012) micro-porous polypropylene (PP) or polyethylene (PE) (1022) Micro-porous polypropylene (PP) or polyethylene (PE) (1032)

Micro-porous polypropylene (PP) or polyethylene (PE) (1042)
Energy Density 100 - 200 Wh/kg and 200 - 300 Wh/L 200 - 250 Wh/kg and 600 Wh/L 250 - 300 Wh/kg and 700 Wh/L

400 - 500 Wh/kg and 1200 Wh/L

A modern lithium-ion battery consists of two electrodes, typically lithium cobalt oxide (LiCoO2) cathode and graphite (C6) anode. The anode and cathode of the lithium-ion battery are separated by a microporous separator soaked in a nonaqueous (aprotic) organic liquid electrolyte containing lithium salt, namely LiPF6, in a mixture of ethylene carbonate (EC) as a primary solvent and at least one linear carbonate selected from dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC) as co-solvents along with an additive (for instance, vinylene carbonate). During the charging of the lithium-ion battery, Li-ions move from the LiCoO2 lattice structure to the anode side to form lithiated graphite (LiC6), whose potential is the closest to that of Li metal (i.e. ~200mV, which is less than that of Li metal). During the discharging of the lithium-ion battery, these ions move back to the LixCoO2 host lattice framework, while electrons are released to the external circuit. The following electrochemical reactions occur during charge/discharge reactions in Li-ion cells:

LiCoO2 Li1-xCoO2 + xLi+ + xe- (reaction at cathode side)

C6+ xLi++xe- LixC6 (reaction at anode side)

LiCoO2 is known to exhibit high oxidation potential i.e. greater than 4.1 V vs Li+/Li with a nominal cell voltage of 3.6V yielding attractive energy and power densities:

Specific energy in the range of 100-265 Wh/kg;

Energy density between 250-693Wh/L;

Specific power ranges from ~250- ~340W/kg.

In general, the source of Li+ ions emanates from lithiated transition metal oxides containing 3d transition metals. These metal oxides are generally referred to as LiM'O2 where M' = Mn, Ni, Co, and Fe. Owing to the involvement of intercalation/deintercalation of Li+ ions during electrochemical reactions involving charge and discharge between cathode (positive electrode) and anode (negative electrode), these Li-Ion cells (or battery) were originally known as rocking-chair or shuttle-cock batteries. First commercialized in Japan in 1991, these batteries have revolutionized the modern electronics world since then. Later, these cells are given a brand name called Li-Ion rechargeable cells. Ever since, these cells are used to power almost all types of portable electronic gadgets, in electric vehicles (EVs) and are now growing popularity for military and aerospace applications.

Nevertheless, use of lithium metal anode was the most preferred choice during the 1970s to 1980s for its high-energy advantage (next to hydrogen) despite its high reactivity and dendrites issues. Although Lithium metal anode possesses a very high theoretical capacity of 3860 mAh/g, rechargeable batteries made of Li metal anodes suffer from dendrite growth and low Coulombic efficiency (CE) (CE = charge output/charge input), hampering their commercialization of rechargeable batteries employing Li metal anodes. Capacity loss and safety hazards of rechargeable batteries made of Li metal anode were prominently due to the formation of in-active (‘dead’) Lithium (Li) at the OCV (open circuit potential) owing to electrochemically formed Li+ compounds at the solid electrolyte interface (SEI) and the formation of electrically isolated unreacted metallic Li. SEI is a passivation layer formed on the surface of lithium anode material occurred due to the spontaneous decomposition of electrolyte on assembling the cell with non-aqueous aprotic Li+ electrolyte.

Unfortunately, employing lithium metal as the anode created a variety of issues such as lithium corrosion, which led to dendrite formation (2002) and large volume changes, resulting in a low cycling stability of a few hundreds of cycles. The dendritic growth (2002) at lithium anode (2001) in lithium secondary batteries is illustrated as a prior-art in Fig. 2 of the accompanying drawings. Lithium metal (2001) is the lightest metal and possess high specific capacity (3860 mAhg-1) and an extremely low electrode potential (-3.04 V vs. Standard Hydrogen Electrode), rendering it an ideal anode material for high-voltage and high-energy batteries. However, the electrochemical potential of Li+/Li lies above the lowest unoccupied molecular orbital (LUMO) of practically known non-aqueous electrolytes, leading to continuous electrolyte reduction unless a passivating solid electrolyte interface (SEI) is formed. The SEI layer is susceptible to damage and repairs non-uniformly on the surface of lithium metal owing to the large volume changes and high reactivity of lithium metal, leading to dendrite growth, which could cause the cell to short-circuit and catch fire. Such an incident had caused the total recall of lithium metal batteries by Moli Energy (Canada) after several fire accidents.

The use of Li+ conducting solid electrolyte as a separator as well as an electrolyte in the form of a solid substrate creating the solid electrolyte interface (SEI) (3001) through artificial layering (3003) before forming a two-electrode cell against a cathode (Li/LTMO) (LTMO – Lithiated transition metal oxides) is illustrated in Fig. 3 of the accompanying drawings.

Two types of rechargeable lithium batteries hitherto known are: non-aqueous and solid-state. A majority of research effort has been devoted to the non-aqueous battery in the past three decades. A different category of rechargeable lithium battery namely Li-air consists of a lithium anode, a lithium-ion conducting solid electrolyte and a porous carbonaceous air cathode, i.e., a gas diffusion layer (GDL). The so-called Li-air battery is expected to mitigate fire and explosion problems due to non-aqueous electrolytes.

An alternative rechargeable aqueous lithium battery is known in the art that consists of a lithium metal anode, a porous cathode and an aqueous electrolyte separated from the lithium anode by a water-stable lithium-ion-conducting solid electrolyte.

The major disadvantages of the aqueous system are:

it does not exhibit the capacity for high power density and extended deep cycling; and

the energy density of the rechargeable aqueous Li-air battery is lower than that of the non-aqueous counterpart.

The major disadvantages of non-aqueous systems are:

decomposition of the electrolyte;

clogging of the porous air cathode by the insoluble discharge product of Li2O2 and contamination by moisture from the air; and

low practical capacity, low round-trip energy efficiency and air purification.

The major disadvantages of using bare elemental lithium as an anode are:

dendritic growth of Li during charging, which poses a huge threat for battery safety (explosion reported due to bare elemental lithium metal used as anode in secondary lithium cells);

long-term stability issues of the anode due to humidity, and hence the stability issues with the battery; and

inappropriate composition of non-aqueous electrolytes.

Therefore, the present inventors realized that there is a necessity to overcome the above challenges and develop a simple, low-cost lithium anode which is replaceable and can be used for Li-anode based batteries, and to provide enhanced energy storage and sustained power for automotive propulsion systems such as electric vehicles (EVs) and any other mission equipment that mitigates the drawbacks mentioned hereinabove.

Thus the present disclosure provides a monolithic PLC anode which comprises a lithium-ion conducting solid electrolyte substrate, an ionically conducting buffer layer (another class of Li+ conducting solid electrolyte), which is found by the present inventors to be stable on contact with Lithium metal deposited onto the substrate (which is otherwise found to be unstable in contact with lithium metal directly), a layer of metallic lithium (Li) deposited on the buffer layer, and a protective layer of metal deposited in such a way that the metallic layer envelops all the three-layers beneath i.e. the Li metal layer, the buffer layer and the substrate, making it a monolithic free-standing cassette. The monolithic PLC anode optionally further comprises a layer of water-stable enamel paint, preferably acrylic nail polish deposited on the protective layer of metal, wherein the layer of water-stable enamel paint acts as a metallic current collector in the monolithic PLC. The layer of water-stable enamel paint is provided only when the monolithic PLC anode is used in conjunction with aqueous electrolyte.

United States Patent No. 9130198 discloses a protected anode architecture having ionically conductive protective membrane architectures, which in conjunction with seal structures and anode backplanes, enclose an active metal anode inside the interior of an anode compartment.

JP2020024920A discloses a foil anode and a protective metallic layer by which the foil is coated, wherein the metal in the foil and the metal in the protective layer are of different electrochemical potentials.

PCT Application 2020/0184900 discloses an anode for a lithium secondary battery having a protective layer, wherein the protective layer contains a 3D structure composed of metal and lithium nitride in order to induce uniform ionic conductivity and electrical conductivity on the surface of the negative electrode.

United States Patent No. 6911280 discloses an anode for a battery having a composition comprising lithium or other alkali or alkaline earth metal layer having a surface coated with an ion conducting protective layer covalently bonded to the metal layer surface, which protects the lithium metal from further chemical reaction.

Chinese Patent Application No. 110828778 discloses a sandwich anode structure including a negative current collector, negative electrode active layer, primary protective layer, lithium-containing metal and a secondary protective layer, wherein the negative electrode active layer is arranged above the negative current collector, the lithium-containing metal layer is positioned between the primary protective layer and the secondary protective layer, the secondary protective layer is positioned above the primary protective layer, and the primary protective layer is positioned on the negative active layer.

US Patent Application No. 2020/0168876 discloses a lithium anode with a protective architecture, wherein the protective architecture includes a first lithium ion conducting separator layer which comprises a lithium ion conducting anolyte; and a second substantially impervious lithium ion conducting layer that prevents the lithium anode from deleterious reaction in direct contact with the seawater of the cathode.

OBJECTS

Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows.

An object of the present disclosure is to ameliorate one or more problems of the prior art or to at least provide a useful alternative.

Another objective of the present disclosure is to provide a replaceable lithium anode particularly for all solid-state lithium secondary cells (batteries), Li-air primary and/or secondary batteries and in general for any Lithium-based energy storage systems.

Yet another object of the present disclosure is to provide an electrochemical cell that can be easily fabricated.

A further objective of the present disclosure is to provide replaceable lithium anode for Li-air batteries or Li-air semi fuel cells or Li secondary batteries employing organic and aqueous electrolyte on the hybrid system in which air cathode is separated by Li ion-conducting solid-state membrane.

Still another objective of the present disclosure is to provide an electrochemical closed-loop architecture that allows continuous operation of Li-air battery or Li-air semi fuel cells (primary) or Li secondary batteries as a plug-n-drive system, as well as continuously replenishing aqueous electrolyte hybrid system by convenient replacement of monolithic PLC anode.

Yet another objective of the present disclosure is to provide monolithic PLC anode-based Li-air batteries or Li-air semi fuel cells or Li secondary batteries for enhanced energy storage to provide the sustained power for automotive propulsion systems such as electric vehicles (EVs) and any other mission equipment.

Still another objective of the present disclosure is to provide a lithium anode for Li metal anode based batteries that do not cause any dendritic growth of Li during electrochemical cycling.

Another objective of the present disclosure is to provide a lithium anode for use in Li-air batteries or Li-air semi fuel cells or Li secondary batteries that do not get affected by high humidity conditions as well as temperature conditions.

Yet another objective of the present disclosure is to provide monolithic PLC anode-based Li-air batteries or Li-air semi fuel cells or Li secondary batteries that endures extreme conditions of humidity and temperature required for certain applications such as space programmes.

Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.

SUMMARY

The present disclosure provides a replaceable monolithic PLC anode for all solid-state lithium secondary cells (batteries), Li-air primary and/or secondary batteries and in general for any Lithium-based energy storage systems.

The present disclosure further provides a process for producing a monolithic PLC anode. The process comprises the steps of providing a lithium ion conducting solid electrolyte substrate; depositing an ionically conducting buffer layer on the lithium ion conducting solid electrolyte substrate; depositing a lithium (Li) metal layer on the buffer layer; depositing a protective layer of metal, which envelops all the three-layers beneath i.e. the Li metal layer, the buffer layer and the top surface of the substrate.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The present disclosure will now be described with the help of the accompanying drawings, in which:

Figure 1 (Prior Art) illustrates the evolution of rechargeable Li battery from generation 1 to generation 4;

Figure 2 (Prior Art) illustrates dendritic growth at lithium anode in lithium rechargeable batteries during plating of lithium;

Figure 3 (Prior Art) illustrates a solid electrolyte interface (SEI) in Li-ion batteries;

Figure 3A (Prior Art) demonstrates the experimental data of stability of Ohara’s LICGC™ when it was exposed to flame;

Figure 4 (Present Invention) illustrates suppression of dendrites by making a monolithic three-layer free-standing stack structure comprised of Cu/Li3PO4/LICGC/Cathode;

Figure 5 illustrates a layered arrangement of the monolithic PLC anode of the present disclosure;

Figure 5A illustrates a side view of the layered arrangement of the monolithic PLC anode;

Figure 5B illustrates a placement of the monolithic PLC anode of Figure 5A in a Li-air semi fuel cell (primary) in operation, where the free-standing anode is used for the plug-n-drive system proposed for EV applications;

Figure 6 illustrates a conceptual arrangement of the monolithic anode of Figure 5A in a hybrid electrolytic (nonaqueous/aqueous) Li-air semi fuel cell (primary) set up according to an embodiment of the present disclosure;

Figure 7 illustrates the deposited Li3PO4 on the solid substrate employing PLD according to an embodiment of the present disclosure;

Figure 7A illustrates the set-up for deposition of lithium metal layer onto Li3PO4;

Figure 7B illustrates the layer of lithium metal deposited onto Li3PO4;

Figure 7C illustrates deposited copper (Cu) layer enveloping vertically layered stack-structure covering all-three layers beneath making a complete cassette-like single free-standing monolithic plate;

Figure 8A illustrates picture of a just fabricated monolithic PLC anode (i) square, (ii) spherical;

Figure 8B illustrates a picture of a fabricated monolithic PLC anode after 24 hours of exposure in an ambient air atmosphere at room temperature;

Figure 8C illustrates a picture of a fabricated monolithic PLC anode after 90 days of storage in an ambient air atmosphere at room temperature;

Figure 8D illustrates laser optic images of a fabricated monolithic PLC anode;

Figure 8E illustrates a graphical representation of lithium (Li) plating-stripping reaction characteristics of monolithic PLC anode in an aqueous 1.5M LiCl solution; the copper layer is temporarily painted with enamel paint (example, nail polish) to avoid alkaline dissolution;

Figure 9 is the real time application of monolithic PLC anode based Li-air cell powering digital alarm clock; and

Figure 10 is a conceptual design of a versatile autonomous charge station employing a hybrid solar-monolithic PLC anode based Li-air secondary battery for electric vehicles.

LIST OF REFERENCE NUMERALS USED IN DETAILED DESCRIPTION AND DRAWING

100 - prior art

101 - first generation Lithium battery

102 - second generation rechargeable battery

103 - third generation rechargeable battery

104 - fourth generation rechargeable battery

1011 - thick metallic lithium anode

1021 - graphitic carbon anode

1031 - silicon composite anode

1041 - ultra-thin lithium metal anode

1012- micro-porous separator (polypropylene)

1022 - micro-porous polypropylene (PP) or polyethylene (PE)

1032 - micro-porous polypropylene (PP) or polyethylene (PE)

1042 - micro-porous polypropylene (PP) or polyethylene (PE)

1013 - titanium disulfide (TiS2) cathode

1023 - cathode (LCO, LFP, NMC)

1033 - cathode (NMC, NCA)

1043 - cathode (High Ni-NMC, S)

200 - dendrites formation onto lithium metal anode

201- lithium metal anode

202 - dendrites formation

300 - solid electrolyte interface (SEI) in Li-ion batteries

301 - solid electrolyte interface (SEI)

302 - spontaneous solid electrolyte interface (SEI)

303 - artificial solid electrolyte interface (SEI)

304 - electrolyte

305 - Li anode

400 - monolithic three-layer free-standing stack structure

401 - copper current collector

402 - lithium metal anode

403 - solid electrolyte membrane/ separator

404 - cathode

405 - aluminium current collector

406 - dendrites formation

500 - monolithic PLC anode

501a - solid substrate

502a - layer of lithium phosphate (Li3PO4) – as ionically conducting buffer layer

503a - layer of lithium (Li) metal

504a - copper (Cu) metal protective layer

501b - monolithic PLC anode

502b - non-aqueous electrolyte

503b - Li+ Ceramic solid electrolyte

504 b - aqueous electrolyte

505b - air cathode

506b - gas diffusion layer and air flow

507b - load

600 - hybrid semi fuel cell

601 - monolithic PLC anode

602- an organic electrolyte

603- lithium conducting solid state membrane

604 - aqueous electrolyte

605 - GDL (porous) air cathode

700 - schematic of deposited Li3PO4 on the solid substrate

701 - Li-ion conducting solid substrate

701a - diameter of solid substrate

702 - Li3PO4 layer

702a - width of Li3PO4 layer

702b - deposited Li3PO4 layer

703 - Bell Jar to deposit Lithium metal on Li3PO4 coated substrate

703a - width of lithium metal layer

703b - deposited lithium metal layer

704 - Tungsten boat

705 - lithium metal to be deposited

706 - set-up for deposition of lithium metal layer onto Li3PO4

707 - Copper (Cu) metal protective layer

800 - laser optic images of a fabricated monolithic anode

801 - Ohara LICGC™ ceramic solid electrolyte (250µm) substrate

802 - Li3PO4 (2µm) buffer solid electrolyte layer

803 - Lithium metal thin film (4µm)

804 - copper cover deposited to cover over the three layer deposits as protector

805 - region between lithium thin layer to Li3PO4 buffer layer

806 - boundary between lithium metal thin film (black) to Li3PO4 buffer layer

807 - region between Ohara substrate to copper coverage over Li3PO4 buffer layer

808 - region from Li3PO4 buffer layer through copper coverage over three layers to LICGC™ substrate to copper coverage over

1000 – solar monolithic PLC anode hybrid power module

1001 - side view of removable protected lithium cassette

1002 - monolithic PLC anode based power module (Li-air battery) or semi fuel-cell

1021 - monolithic PLC anode in a Li-air semi fuel cell

1022 - DC

1023 - EMS

1003 - DC

1004 - terminals

1005 - DC/DC convertor

1006 - DC/AC inverter

1007 - grid synchronized controller

1008 - DC/DC convertor

1009 - MPPT

1010 - solar photovoltaic

DETAILED DESCRIPTION

Embodiments, of the present disclosure, will now be described with reference to the accompanying drawing.

Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.

The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are open-ended transitional phrases and therefore specify the presence of stated features, integers, steps, operations, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The particular order of steps disclosed in the method and process of the present disclosure is not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.

A basic electrochemical battery cell usually includes two oppositely-charged electrodes, separated by a separator material sandwiched between these electrodes. One of these two electrodes is often referred to as a counter electrode of the other. In the context of Li-ion rechargeable cells, it is customary to denote cathode as a positive electrode and anode as a negative electrode.

Lithium metal (2001) is the lightest metal and possesses a high specific capacity (3860mAhg-1) and an extremely low electrode potential (-3.04 V vs. Standard Hydrogen Electrode), rendering it an ideal anode material for high-voltage and high-energy batteries. However, the major disadvantages of using bare elemental lithium as an anode are:

dendritic growth of Li during charging, which poses a huge threat for battery safety (explosion reported due to bare elemental lithium metal used as anode in secondary lithium cells);

long-term stability issues of the Li anode due to humidity, and hence the stability issues with the battery; and

NASICON-type solid electrolyte is unstable in direct contact with lithium metal because Li+ diffusion changes the lattice structure of LICGC?, which makes it inferior and modifies the pathway for Li+ conduction under solid-state conditions at room temperature.

The present disclosure envisages a free-standing monolithic PLC anode for Li-air battery or Li-air semi fuel cells or Li secondary batteries.

In an aspect, the present disclosure provides a monolithic PLC anode (500). The anode comprises:

a lithium-ion conducting solid electrolyte substrate (501a);

an ionically conducting buffer layer (502a) deposited onto the substrate (501a);

a layer of metallic lithium (Li) (503a) deposited on the buffer layer (502a); and

a protective layer of metal (504a) deposited in an enveloping manner covering the metallic Li layer (503a), the buffer layer (502a), and the top surface of the substrate (501a) forming a cap-like structure on the top of the substrate (501a).

In an embodiment, lithium ion conducting solid electrolyte substrate (501a) is made of a material represented by formula (Li1+x+3zAlx(Ti,Ge)2-xSi3zP3-zO15), where 2 >x> 0 and 2>z> 0.

In an embodiment, lithium ion conducting solid electrolyte substrate is made of lithium ion conducting glass ceramic substance. The lithium ion conducting solid electrolyte substrate (501a) is in any one shape selected from circular, square and rectangle, preferably the shape is circular. One of the two sides of the lithium ion conducting solid electrolyte substrate (501a) is configured to act as a separator between monolithic PLC anode and a cathode. Further, the lithium ion conducting solid electrolyte substrate is made of lithium ion conducting glass ceramics. The thickness of lithium ion conducting solid electrolyte substrate (501a) is in the range of 100µm to 250µm (±20µm); both polished and clean. In an exemplary embodiment, thickness of lithium ion conducting solid electrolyte substrate (501a) is in the range of 100 µm to 250 µm (±20µm). When the shape of the substrate is circular, the diameter of the substrate preferably is about 2 inches; when the shape of the substrate is square, the length of a side of the substrate is about 2 inches; and when the shape of the substrate is rectangular, the length of the substrate is about 2.1 inches to 3 inches, and the breadth is about 2 inches.

In accordance with the present disclosure, an ionically (Li+) conducting buffer layer (502a) of a pre-determined thickness reduces the overall loss of ion conductivity across the buffer layer (502a) and the lithium ion conducting solid electrolyte substrate (501a).

The material of the buffer layer (502a) is at least one or the combination thereof in the following group of metal oxides: Li2O, B2O3, WO3, SiO2, P2O5, Li2O, Li3PO4, Al2O3, V2O5, GeO, Li2S, P2S5, Li2Ti3O7, Li3N, ßLiAlSiO4 and ZnO.

.In a preferred embodiment, the buffer layer is made from lithium phosphate (Li3PO4).

The pre-determined thickness of the buffer layer (502a) is in the range of 0.1 µm to 4 µm. In an exemplary embodiment, the thickness of the buffer layer (502a) is in the range of 2 µm to 3 µm (±0.5µm). Further, in a preferred embodiment, the thickness of the buffer layer (502a) is 2 µm (±0.5µm).

The thickness of the lithium metal layer (503a), while is not particularly limited, and depends on the specific application, typically can be as thin as 0.5 µm to about 5 mm or higher. In an exemplary embodiment, the thickness of the lithium metal layer (503a) is in the range of 3 µm to 6 µm. Further, in a preferred embodiment, the thickness of the lithium metal layer (503a) is about 4 µm.

The material of the protective layer of metal (504a) is at least one selected from the group consisting of Cu, Ni, Al, Au and Pt. The aim of the protective layer is primarily to avoid the exposure of Li metal layer (503a). In an exemplary embodiment, the protective layer of metal is made of Cu. The thickness of the protective layer of metal (504a) is in the range of 2 µm to 15 µm. In a preferred embodiment, the thickness of the protective layer of metal (504a) is in the range of 6 µm to 12 µm. In a further preferred embodiment, thickness of the protective layer of metal (504a) is in the range of 8 µm to 10 µm.

In accordance with an aspect of the present disclosure, the protective layer of metal is further provided with a layer of water stable enamel paint. When the monolithic PLC anode is used with aqueous electrolytes, the enamel paint prevents the metal layer from dissolution. In an exemplary embodiment, the water stable enamel paint is an acrylic nail polish.

In another aspect of the present disclosure, the total surface area of the buffer layer (502a) is less than the total surface area of the substrate (501a), and the total surface area of the metallic lithium (Li) layer (503a) is less than the total surface area of the buffer layer (502a).

In a further aspect of the present disclosure, the distance between the boundary of the substrate (501a) and the boundary of the buffer layer (502a) is equal in all sides around the buffer layer (502a), and the distance between the boundary of the buffer layer (502a) and the boundary of the metallic lithium (Li) layer (503a) is equal in all sides around the metallic lithium (Li) layer (503a).

The monolithic PLC anode (500) of the present disclosure is of replaceable type, which makes it well suitable for use in electrochemical energy storage devices such as lithium secondary batteries, Li-air rechargeable battery, Li-air semi fuel cells, Li-air cell and in general for any lithium-based energy storage systems.

In another aspect, the present disclosure provides a method for producing a monolithic PLC anode. The method comprises of the following steps:

providing a lithium ion conducting solid electrolyte substrate;

depositing an ionically conducting buffer layer on lithium ion conducting solid electrolyte substrate to obtain a first layer;

depositing lithium (Li) metal layer on the first layer to obtain a second layer; and

depositing a protective metal layer enveloping all the three-layers beneath i.e. the Li metal layer, the buffer layer and the substrate.

In accordance with an aspect of the present disclosure, the method further comprises a step of depositing a layer of water stable enamel paint on the protective layer of metal. The enamel paint layer is solely meant to avoid atmospheric surface attack in to the metallic layer as well as to prevent dissolution of metallic layer when using aqueous electrolytes. In an exemplary embodiment, the water stable enamel paint is acrylic nail polish.

The material of ionically conducting buffer layer is at least one selected from the group consisting ofLi2O, Li3PO4, Al2O3, V2O5, GeO2, Li2S, P2S5, Li2Ti3O7, Li3N, ßLiAlSiO4 and ZnO but preferably Li3PO4, and P2O5. In a preferred embodiment, the buffer layer is made from lithium phosphate (Li3PO4).

In another embodiment, the protective layer of metal is at least one selected from the group consisting of Cu, Ni, Al, Au and Pt.

In a preferred embodiment, the protective layer of metal is Copper (Cu).

In accordance with the present disclosure, the buffer layer is deposited on lithium ion conducting solid electrolyte substrate by at least one of the methods selected from the group consisting of pulse laser deposition (PLD), atomic layer deposition (ALD), metal organic chemical vapour deposition (MOCVD), additive manufacturing (AM), radio frequency (RF) sputtering, DC sputtering and ion beam assisted deposition (IBAD).

In accordance with the present disclosure, the lithium metal layer is deposited on the ionically conducting buffer layer by at least one of the methods selected from the group consisting of thermal evaporation, electro-deposition, atomic layer deposition (ALD), and magnetic sputtering.

In accordance with the present disclosure, the protective layer of metal is deposited on the lithium metal layer by at least one of the methods selected from the group consisting of thermal evaporation, electro-deposition, magnetic sputtering and atomic layer deposition (ALD).

In accordance with the present disclosure, thickness of the lithium ion conducting solid electrolyte substrate, the buffer layer, the lithium metal layer and the protective layer of metal is in the range of 100 µm to 250 µm, 0.1 µm to 4 µm, 0.5 µm to 5 mm and 2 µm to 15 µm respectively. The monolithic PLC can be fabricated with different or similar dimensions for all the layers. Fig 5 illustrates a preferred embodiment of the invention, where the substrate, the buffer layer, and the Lithium metal layer are of different dimensions with the protective metal layer covering all the three layers.

In another aspect, the present disclosure provides an electrochemical cell system. The system comprises:

a monolithic PLC anode (500) comprising

a lithium ion conducting solid electrolyte substrate (501a);

a buffer layer (502a) deposited on the substrate (501a);

a layer of metallic lithium (Li) (503a) deposited on the buffer layer (502a); and

a protective layer of metal (504a) deposited on the lithium metal layer (503a);

a cathode (605);

wherein the monolithic PLC anode is in ionic communication with the cathode via the lithium ion conducting solid electrolyte substrate.

The material of the buffer layer is at least one selected from the group consisting of Li2O, Li3PO4, Al2O3, V2O5, GeO2, Li2S, P2S5, Li2Ti3O7, Li3N, ßLiAlSiO4 and ZnO. In a preferred embodiment, the electrochemical buffer layer is made from lithium phosphate (Li3PO4).

The protective layer of metal is at least one selected from the group consisting of Cu, Ni and Al. In a preferred embodiment, the protective layer of metal is Cu.

Preferably, the solid electrolyte substrate (LICGCTM) is made of a proprietary combination of Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2 having a general formula (Li1+x+3zAlx(Ti,Ge)2-xSi3zP3-zO15) where 2 >x> 0 and 2>z> 0.

Preferably, the material of cathode is at least one selected from the group consisting of lithium cobalt oxide (LiCoO2), lithium iron phosphate (LiFePO4), lithium nickel cobalt manganese oxide represented by formula Li[NixMnyCo(1-x-y)]O2, where 0= x=1 and 0= y=1, Lithium Nickel Cobalt Aluminium Oxide (LiNiCoAlO2), Lithium nickel manganese oxide (LNMO) (LiNi0.5Mn1.5O4), LiFePO4/Carbon nanocomposite, dilithium manganese orthosilicate (LMS) Li2MnSiO4, air (oxygen), sulphur.

In another aspect, the present disclosure provides a hybrid electrochemical cell system. The system comprises:

a monolithic PLC anode (500), the anode comprising:

a lithium ion conducting solid electrolyte substrate (501a);

an ionically conducting buffer layer (502a) deposited on the substrate (501a);

a layer of metallic lithium (Li) (503a) deposited on the buffer layer (502a); and

a protective layer of metal (504a) deposited down to the substrate overlapping all the layers beneath as an umbrella covering.

a cathode; and

an electrolyte, wherein the electrolyte is at least one selected from the group consisting of aqueous acidic, aqueous alkaline, non-aqueous aprotic and lithium conducting solid electrolyte substrate;

wherein the monolithic PLC anode is in ionic communication with the electrolyte, and the electrolyte is in ionic communication with the cathode.

In accordance with present disclosure, the hybrid electrochemical cell forms one of the following cells: a Li-air rechargeable cell (or battery), Li-air semi fuel cell (or battery), and a Li metal rechargeable cell.

The all-solid-state lithium metal secondary cell using a monolithic protected lithium cassette anode of the present disclosure can be fabricated having the following electrochemical couples but not limited to:

Cu/PLC/NMC333 (LiNi0.33Mn0.33Co0.33O2)/Al

Cu/PLC/NMC532 (LiNi0•5Mn0•3Co0.2O2)/Al

Cu/PLC/NMC622 (LiNi0.6Mn0.2Co0.2O2)/Al

Cu/PLC/NMC811 (LiNi0.8Mn0.1Co0.1O2)/Al

Cu/PLC/LiNiCoAlO2 (NCA)/Al

Cu/PLC/LiNi0.5Mn1.5 O4/Al

Cu/PLC/LiFePO4/Al

Cu/PLC/Li2MnSiO4/Al

Cu/PLC/air(oxygen)/Al

Cu/PLC/sulphur/Ni

Cu/PLC/LiNi0.5Mn1.5O4/Al

Cu/PLC/LiCoPO4/Al

In an embodiment, the architecture of the monolithic PLC anode comprises a well-engineered three-layer structure with a typical circular dimension and pre-optimized thickness of a stack comprising of LICGCTM plate/ Li3PO4/lithium metal/copper accomplished via combined PLD and thermal evaporation technique as appropriate. Firstly, a layer of lithium phosphate (Li3PO4) is deposited on the LICGCTM solid electrolyte substrate as a buffer layer to prevent lithium metal directly reacting with the substrate (as the reaction with the substrate poses severe instability towards lithium metal and undesirably affects the Li+ conductivity). Secondly, a layer of elemental lithium (Li) deposited on the Li3PO4 buffer layer with the help of appropriate Stainless Steel masks. Finally, in order to accomplish a complete protective envelope, copper (Cu) metal deposition is done over the three vertically stacked-structure covering all-the three layers down to the top surface of the substrate rendering a complete cassette-like free-standing monolithic plate (Fig. 5A).

In order to achieve effective adherence of Li3PO4 deposition on the solid substrate, it is preferable to have a solid substrate that shows a high degree of Li+ conductivity at room temperature, highly resistant to chemicals and heat, effectively prevents Li dendrite penetration, has a very good intrinsic porosity for good adherence of Li3PO4 deposition, and is dust and grease repellent.

The above properties of the solid substrate can be achieved by making a correct composition of the solid electrolytes.

In one of the examples of the present disclosure, the solid electrolyte (substrate) is a Lithium-Ion Conducting Glass-Ceramics sold as LICGC™, available from Ohara Inc., Japan.

Without departing from the teachings of the present invention, for production of the monolithic PLC anode and its layered architecture for enhanced efficiency, the solid substrate used was the above said LICGC™). The choice of Ohara’s LICGC™ was due to the following factors:

LICGC™ exhibits high Lithium-Ion Conductivity of the order of 1 to 4 x 10-4 S/cm at room temperature with unit Li+ mobility;

LICGC™ possesses excellent chemical resistance such as to water, mild acid that may have an enormous influence on the conductivity of Li+;

LICGC™ is stable in air and water, it is a complete solid-state electrolyte, exhibits very good heat resistance up to 600oC, and also effectively prevents Li dendrite penetration;

due to the intrinsic porosity of LICGC™, its adherence characteristics are very good and hence the Li3PO4 coating on LICGC™ adhered effectively; and

LICGC™ is dust and grease repellent.

LiCGCTM is stable at >5 V, whereas the liquid electrolytes are not stable beyond 4.4V versus Li+/Li. Hence PLC has the advantage of improving the operating potential window of the device upto 5V when coupled with cathodes such as LiNi0.5Mn1.5O4 and LiCoPO4.

As shown in Fig. 3A (prior art), thermogravimetric analysis and differential thermal analysis demonstrate the stability of LICGC™ to be stable up to 600°C. As the operating temperature of lithium-containing batteries is expected to operate within-20°C to +55°C, the glass-ceramic utilized in the present invention is highly thermally stable and avoids any failure due to thermal runaway problems in the energy storage devices.

Fig. 4 represents the present invention employing Li+ conducting LICGC? as the substrate as well as a separator for lithium metal anode and LTMO or air cathode (Gas diffusion layer, for instance) for making viable and safe Li secondary batteries.

In an embodiment, any solid electrolytes substrate such as the ones called LATP and (LICGC?) are employable as well. The present invention uses a lithium-stable Li+ conducting electrolyte namely Li3PO4 as a thin buffer layer between the Lithium metal anode and LATP solid electrolyte. The embodiment describes the fact that to make use of LATP against lithium metal anode, there can be a buffer layer in between LATP preventing Li from reacting with LATP lattice. Thus, the present invention uses another Li stable solid electrolyte namely Li3PO4 whose Li+ ionic conductivity is one to three orders of magnitude compared to LATP. However, use of this buffer layer with definitive thickness is to help overcome overall loss of ion conductivity across LATP/Li3PO4 layers. Further, whenever battery applications involving aqueous electrolyte in conjunction with lithium metal anodes, the present invention protects the lithium anode from directly reacting with aqueous electrolytes e.g. Li-air battery where a solid-state air-permeable porous carbonaceous matrix, the so-called gas diffusion layer (GDL) allowing O2 cathode or lithium secondary battery where the cathode being lithium transition metal oxide (Fig 4). In the present invention, LATP type substrate acts as a water-stable and Li ion-permeable solid electrolyte membrane with high lithium-ion conductivity and excellent mechanical properties between Li anode and cathode in Li-air, Li secondary batteries and Li-air (full or Semi) fuel cells.

In another aspect, the present disclosure provides a stand-alone solar power module for autonomous charge stations for EVs, wherein a versatile autonomous charge station employs a hybrid solar-monolithic anode based Li-air secondary battery for charging the electric vehicles.

Fig. 5 illustrates the layered arrangement of the monolithic PLC anode, according to a preferred embodiment of the present disclosure. The monolithic PLC anode (500) primarily has four layers i.e. the solid substrate (501a); a layer of lithium phosphate (Li3PO4) (502a) deposited on the solid substrate; a layer of lithium (Li) metal (503a) deposited on the Li3PO4 layer, and copper (Cu) metal protective layer (504a) deposited on the three layers (501a-503a).

Fig. 5A illustrates a side view of the layered arrangement of the free-standing monolithic PLC anode of Fig. 5.

As shown in Fig. 5B, the monolithic PLC anode (501b) is arranged in a Li-air semi fuel cell. In Li-air semi fuel cell (nothing but the primary Li-air cell), an non-aqueous electrolyte (502b), the ceramic solid electrolyte membrane (503b), an aqueous electrolyte (504b), the air cathode (505b) called Gas Diffusion Layer (GDL, 506b), and load (507b) are shown as in Fig 5B.

In one of the embodiments, an arrangement of the monolithic PLC anode in a Li-air semi fuel hybrid cells set up is provided. Fig 6 illustrates an embodiment of the present invention where the monolithic PLC anode is employed instead of lithium metal anode and hence makes the Li-secondary batteries feasible to be workable in the aqueous electrolyte media. As shown in Fig. 6, the structure of Li-air hybrid semi fuel cell (600) stalk, which includes the monolithic PLC anode (601) of the present disclosure, an organic non-aqueous electrolyte (602), a lithium conducting solid-state membrane (603), aqueous electrolyte (604), and then the GDL (porous) Air cathode (605).

EXPERIMENTAL DETAILS

The present disclosure will now be explained in further detail by the following examples. These examples are illustrative of certain embodiments of the invention without limiting the scope of the present invention.

Example 1: Production of monolithic PLC anode

Fig. 7 illustrates the deposited Li3PO4 (702) on the solid substrate (701). The diameter (701a) of the solid substrate is 19 mm, whereas the width (702a) of the deposition of Li3PO4 is 13 mm.

Step 1: Deposition of Li3PO4 on cleaned Ohara glass-ceramic (LICGCTM)

Circular Ohara LICGCTM solid substrate was taken. Li3PO4 was deposited on the Ohara LICGCTM solid substrate by Pulse Laser Deposition (PLD) technique. The parameters employed for deposition are as below:

O2 pressure maintained inside the chamber = 2 to 3.5 ×10-4Pa;

elapsed time = 4 h;

laser distance = 60-70 mm;

laser power = 150mJ/10 Hz;

rate of deposition = 500 nm/h at room temperature in a vacuum; and

thickness of Li3PO4 deposition layer = 2 µm.

The PLD deposition of the buffer layer Li3PO4 was done onto LICGC™ (1 sq. inch and 250 µm thick, supplied by Ohara Inc, Japan used as received and in another reproducing experiment, the as-received plate was cut into a circular shape of 50.8 mm (2 inches) diameter using a diamond cutter) solid substrate.

To deposit Li3PO4, PLD target was prepared in the first place using pure Li3PO4 polycrystalline powder as-received (98% pure powder). Thus, the target pellet was prepared using a 10 mm pelletising mold made of die steel and the cold-pressed pellet was subjected to an isostatic compression before the pellet was loaded into the PLD chamber. Once the conditions are maintained, a laser source was energized to ablate the target pellet. An ArF excimer laser operating at a wavelength of 193 nm set at 150 mJ at the laser exit was employed. Nevertheless, it was assumed to have diminished to ~100 mJ on reaching the target surface owing to reflection and attenuation by the optical window inside the vacuum chamber. The laser was focused on the target pellet with an irradiation area (spot size) of ~0.015 cm2; thus, the laser energy impinged onto the target was estimated to be about 5 J/cm2. The Li3PO4 buffer layer was grown in a vacuum chamber with a base pressure of4×10-3 Pa in a different oxygen pressure values from 0.1 to 10 Pa at room temperature. The target to substrate (LICGC™) distance was set at ~20-30 mm. The growth condition of the Li3PO4 buffer layer consisted of 75,000 to 80,000 laser shots with a repetition rate of 5 Hz.

Step 2: Deposition of lithium metal layer onto Li3PO4 employing the thermal evaporation process

The active lithium metallic layer was deposited onto Li3PO4 employing the thermal evaporation process. The typical quantity of Lithium disc to be utilized for deposition was placed over a tungsten boat. The elapsed time was maintained for about 40 min with intermittent deposition at an average applied current of 24.5 A; double coating (to ensure sufficient lithium is deposited as active layer electrode) to get the 11x11 mm coating area of Li on Li3PO4;

Lithium metal was melted in a pressurized bell jar with a temperature difference (?T) between the tungsten boat and the substrate to be 6000C. The current applied to melt the lithium was kept at 20A for 30min; and the pressure in the bell jar was maintained at 4x10-3 Pa.

Utmost care was exercised to ensure the slow deposition of lithium layer within the SS mask containing Li3PO4 regime. The process yielded the final thickness of the lithium layer to be ~ 4 µm. The latter value is indicative and for exemplary purpose only. The loading content of lithium metal deposition differs and is customizable depending on the cell/battery capacity required for the end-user application. During the thermal evaporation process, intermittent deposition over two hours is important so as to avoid overheating of LICGC™ and to prevent progressively deposited lithium from melting.

The experimental set up is illustrated in Fig. 7a. It shows the solid substrate (701), thermal evaporation bell jar (703), tungsten boat (704), and the deposited lithium layer (705).

Fig. 7b illustrates the layer of lithium metal deposited onto Li3PO4. The Lithium metal deposition layer (705) has a width (705a) of 11mm, and a thickness of 4 µm.

Step 3: Deposition of Cu protective layer

Deposition of Cu protective layer (Cu foil procured from Delker Corp,USA; thickness of Cu foil used was 0.02 mm) was done employing the thermal evaporation process using stainless steel (SS315L) square spacer.

Before the loading of the copper foil inside the thermal evaporation chamber, the foil was cleaned in methanol in a sonicator for 30 min; wherein the quantity used was 300 mg.

Cu deposit layer serves a dual purpose: Offers complete protection of the three layers preventing lithium being exposed in adverse conditions (Humidity, Air exposure etc) as well as it serves the purpose of being the current collector which is the customary practice in lithium-ion cell fabrication industry-standard where anode slurry is coated onto the thin copper foil.

Copper metal was melted in a pressurized bell jar by maintaining a temperature gradient between the tungsten boat and the substrate to be around 6000C.

The current applied to melt copper was 20 to 33 A with a gradual increase.

On getting the copper in molten stage, the current was maintained at 33-35A for 10 min with the shutter closed (which is placed between target and tungsten crucible containing molten copper).

The current was then again reduced to 25 A, and maintained for of about 15 min. Later, the current was again increased to 33 A, and maintained for ~10 min. To obtain the uniform deposition of copper, steps 4 to 7 are repeated for one hour.

To allow the entire process to take place completely, the pressure maintained inside the bell jar was 4x10-3 Pa.

These steps ensured the slow deposition of copper to take place without any pinholes on the deposit and thus yielded the final thickness of the deposit to be about 8 to 10µm.

Fig. 7C illustrates deposited Copper (Cu) protective layer (706) over the lithium layer/Li3PO4/LICGCTM (701, 702, and 705).

Evaluation of the monolithic PLC anode

As shown in Fig. 8A to Fig. 8C, the produced monolithic PLC anode is exposed to ambient air and humid atmosphere for 90 days and is found to be unaffected by air and moisture owing to the presence of pin hold free protective Cu layer deposited on top. Electrochemical cell testing and laser imaging proved the safe presence of lithium as exemplified elsewhere in this art. This demonstrates the air and humidity stability of the fabricated monolithic PLC and its potential applications as a promising lithium anode and can be used in both aqueous and non-aqueous electrolytes for Li-air semi fuel cells. Importantly, monolithic PLC facilitates a standalone all-solid-state rechargeable lithium metal batteries (secondary) [once abandoned after a major fire accident in Moli Energy, Canada in early 1990] giving a renewed life for making promising all-solid-state Lithium metal secondary batteries; this invention makes way for a new comeback for lithium metal batteries employing the monolithic PLC, a fully protected lithium metal/solid electrolyte free-standing cassette in the name of the monolithic cassette as described in the embodiment of the present disclosure.

Circularly shaped monolithic PLC anode is shown in Fig. 8A(b) which shows the reproducible version of monolithic PLC anode in any shape and size with the same procedure disclosed elsewhere in the embodiment in the present art.

The laser optic images of the monolithic PLC anode are shown in Fig. 8D. The laser optic images show the microscopic view of the monolithic PLC. Five regions are identified to show how the invention provides a free-standing lithium anode in the form of a cassette:

the region between lithium layer to Li3PO4 buffer layer;

the boundary between lithium metal thin film (black color) to Li3PO4 buffer layer;

region between LICGC™ substrate to copper coverage over Li3PO4 buffer layer and lithium metal layer;

the region from Li3PO4 buffer layer through copper envelope over three layers down to the top surface of LICGC™ substrate .

As shown in Fig. 8E, the lithium plating and stripping electrochemical characteristics of monolithic PLC is studied at room temperature, in aqueous electrolyte (1.5M LiCl) solution versus platinum counter electrode at a scan rate of 5mV/s to prove as to how the vulnerable lithium is made compatible with aqueous electrolyte owing to the present invention, that is PLC. To avoid, copper dissolution in aqueous media, enamel paint was brush coated onto the copper envelope. A conductive wire was soldered from copper as a current collector (connected to the working electrode probe) during the above electrochemical experiment.

The plating-stripping cyclic voltammograms(CV) are found to overlap without much hysteresis – an electrochemical signature indicating the stripping (discharge)/plating (charge) reaction of lithium metal. The reaction is performed in an electrochemical set up having a protective lithium cassette as anode as working electrode and a platinum (Pt) foil as a counter electrode. The CV plot demonstrates the deposition of Li metal on Pt and dissolution of Li+ ions into the solution occurring in steady-state at room temperature. The plating-stripping experiment on monolithic PLC demonstrates the availability of lithium for electrochemical reactions via LICGC™ which acts as a separator (bottom side) as well as a solid electrolyte.

In the case of Fig. 5B, the replaceable monolithic PLC anode helps to work as a source for current as in secondary batteries. Thus, it enables a plug-and-drive proposition plausible as the lithium metal reacts readily in an electrochemical couple such as the one proposed below using the concept of oxygen (in the air) as air cathode in a cell or battery. To avoid corrosion of Cu protective layer in aqueous electrolyte (1.5M LiCl), the protective lithium cassette is masked by a colourless acrylic nail polish and a small portion is covered by gold paint as a current collector from copper foil or soldered a wire while using monolithic PLC in conjunction with aqueous electrolyte. Thus, it is evident that the monolithic PLC anode of the present disclosure compatible with aqueous electrolytes as well. However, this invention as described in the embodiment is primarily meant for All-Solid-State Lithium Secondary Cells (Batteries).

Example 2: monolithic PLC anode based Li-air cell powering digital alarm clock

Monolithic PLC anode based Li-air cell was made and was used to power the digital alarm clock. Monolothic PLC based Li-air cell provided the required voltage to run the alarm clock (Fig 9).

Example 3: Solar-monolithic PLC hybrid semi fuel cell-powered versatile autonomous charge station for electric vehicles

As shown in Fig. 10, conceptually a hybrid power module comprised of solar PV and monolithic PLC enabled Li-air battery or Li-air semi fuel cells was designed. An autonomous charge station for Electric Vehicles (EVs) was designed by incorporating the above-mentioned monolithic PLC anode-based power module in the main on-board power source via DC/DC converter. The produced electrical energy from solar PV is quickly buffered (absorbed) electrically in a rechargeable all-solid state lithium cell employing monolithic PLC anode within the power module for later use. Necessary power converters were employed to boost DC level via designated DC/DC converters and the excess energy will be shared on the gridline via multi-level DC/AC inverters.

technical advancements AND ECONOMIC SIGNIFICANCE

The present disclosure described herein above has several technical advantages including, but not limited to, the realization of a monolithic PLC anode that:

prevents Li dendrite penetration – a challenging concern for the lithium battery world;

is stable in air, water and exhibits excellent heat resistance. All these properties are considered extremely desirable in Lithium metal secondary batteries – a much sought after technology for battery world. It imparts a new revolution to the EV era;

can be utilized in vast applications (domestic electronic applications, power tools, space, electric mobility etc);

can be utilized in aqueous and non-aqueous electrolytes for Li-air semi fuel cells thus makes it being versatile;

the provided electrochemical closed-loop architecture allows continuous operation of Li-air semi-fuel cells (primary) with convenient replacement of monolithic PLC anode, and/or rechargeable Li-air cells (secondary) does not suffer from active lithium loss as the monolithic PLC anode is protected enough by a buffer layer of Li3PO4;

the substrate on which lithium is deposited being ceramic and is highly heat resistant and stable up to 600°C accompanied by its mechanical integrity;

is safe for use in space and electric vehicle (EV) propulsion as the failure of energy storage devices due to thermal runaway problems can be completely avoided;

monolithic PLC anode is directly usable in all-solid state secondary lithium cells thus made lithium’s advantage to make a comeback for vast applications (domestic electronic applications, power tools, space, electric mobility etc);

with the use of monolithic PLC anode, electrochemical closed-loop architecture is provided that allows continuous operation of Li-air semi fuel cells (primary) by means of convenient replacement of monolithic PLC anode, and/or rechargeable Li-air cells (secondary) – a kind of plug-n-use/drive as the case may be;

as the monolithic PLC anode is protected enough by a buffer layer of Li3PO4, it does not suffer from active lithium loss;

the substrate on which lithium is deposited being ceramic and is highly heat resistant and stable up to 6000C accompanied by mechanical integrity, failure of energy storage devices due to thermal runaway problems can be completely avoided thereby enhancing the safety of using this monolithic PLC anode in space and electric vehicle (EV) propulsion;

since Cu deposition acts as a protective layer burying the three-layer stack of Li/Li3PO4/LICGC) underneath as well as the current collector on the Lithium layer of the monolithic PLC, the CuO formed due to oxidation of Cu passivates the surface of the monolithic PLC anode prevents from further reacting with the atmosphere and hence the reactive lithium remains intact within the cassette itself;

alternatively covering the Cu protective layer by transparent acrylic nail polish and a small area covered by gold paint as a current collector, both Cu corrosion into CuO and Li reacting with aqueous electrolytes can be avoided as demonstrated in this specification; and

since the monolithic PLC anode can be replaced-off from a shelf in charging stations analogous to gasoline fuel, it is a suitable candidate for Li-air semi-fuel cells (primary) that can conveniently and efficiently power electric and hybrid electric vehicles and other space missions, a portable power source in rockets and to power such electrochemical cells on-demand in space and/or in other planetary landing missions (moon, Mars, and beyond).

Cu/PLC/LiNi0.5Mn1.5O4/Al and Cu/PLC/LiCoPO4/Al couples possess 5V cathode and monolithic PLC anode is stable at >5 V, whereas the liquid electrolytes are not stable beyond 4.4V versus Li+/Li. Hence monolithic PLC anode has the advantage of improving the operating potential window of the device upto 5V.

The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as not to unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

The foregoing description of the specific embodiments so fully revealed the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.

Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.

The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.

While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation. For example, the same methodology can be adapted to monolithic protected Sodium cassette (monolithic PSC) as well. Analogously, for any metal anode in metal-air batteries, protection of the metal anode (e.g. Aluminium, Zinc etc) can be achieved by coating inherently conducting polymers.
,CLAIMS:1. A monolithic protected lithium cassette (PLC) anode (500), said anode comprising:

a lithium ion conducting solid electrolyte substrate (501a) having a top surface and a bottom surface;

an ionically conducting buffer layer (502a) deposited on the top surface of said substrate (501a);

a layer of metallic lithium (Li) (503a) deposited on said buffer layer (502a); and

a protective layer of metal (504a) deposited in an enveloping manner covering the metallic Li layer (503a), the buffer layer (502a), and the top surface of the substrate (501a).

2. The monolithic PLC anode (500) as claimed in claim 1, wherein said lithium ion conducting solid electrolyte substrate (501a) is made of a material represented by the formula Li1+x+y Alx(Ti,Ge)2-xSiy P3-yO12, wherein 2 >x > 0 and 1 >y >0.

3. The monolithic PLC anode (500) as claimed in claim 1, wherein said lithium ion conducting solid electrolyte substrate is made of lithium ion conducting glass ceramics.

4. The monolithic PLC anode (500) as claimed in claim 1, wherein the material of said buffer layer (502a) is at least one selected from the group consisting of Li2O, Li3PO4, Al2O3, V2O5, GeO2, Li2S, P2S5, Li2Ti3O7, Li3N, ßLiAlSiO4 and ZnO, preferably lithium phosphate (Li3PO4).

5. The monolithic PLC anode (500) as claimed in claim 1, wherein the material of said protective layer of metal (504a) is at least one selected from the group consisting of Cu, Ni, Au, Pt and Al, preferably Cu.

6. The monolithic PLC anode (500) as claimed in claim 1, wherein said ionically conducting buffer layer (502a) of a pre-determined thickness reduces the overall loss of ion conductivity across said buffer layer (502a) and said lithium ion conducting solid electrolyte substrate (501a).

7. The monolithic PLC anode (500) as claimed in claim 1, wherein the protective layer of metal (504a) is covered with a layer of water stable enamel paint.

8. The monolithic PLC anode (500) as claimed in claim 1, wherein said lithium ion conducting solid electrolyte substrate (501a) is in at least one shape selected from spherical, square and rectangle.

9. The monolithic PLC anode (500) as claimed in claim 1, wherein said lithium ion conducting solid electrolyte substrate (501a) is configured to act as separator between said monolithic PLC anode and a cathode.

10. The monolithic PLC anode (500) as claimed in claim 1, wherein the thickness of said lithium ion conducting solid electrolyte substrate (501a) is in the range of 50 µm to 1000 µm, preferably in the range of 100 µm to 250 µm.

11. The monolithic PLC anode (500) as claimed in claim 6, wherein the pre-determined thickness of said buffer layer (502a) is in the range of 0.1 µm to 4 µm, preferably in the range of 2 µm to 3 µm, more preferably about 2 µm.

12. The monolithic PLC anode (500) as claimed in claim 1, wherein the thickness of said lithium metal layer (503a) is in the range of 0.5 µm to 5mm..

13. The monolithic PLC anode (500) as claimed in claim 1, wherein the thickness of said protective layer of metal (504a) is in the range of 2 µm to 15 µm, preferably in the range of 6 µm to 12 µm, more preferably in the range of 8 µm to 10 µm.

14. The monolithic PLC anode (500) as claimed in claim 1 is of replaceable type for use in electrochemical energy storage devices such as lithium secondary batteries, lithium air rechargeable battery, lithium air semi fuel cells and lithium air cell.

15. The monolithic PLC anode (500) as claimed in claim 1, wherein the total surface area of the buffer layer (502a) is less than the total surface area of the substrate (501a), and the total surface area of the metallic lithium (Li) layer (503a) is less than the total surface area of the buffer layer (502a).

16. The monolithic PLC anode (500) as claimed in claim 1, wherein the distance between the boundary of the substrate (501a) and the boundary of the buffer layer (502a) is equal in all sides around the buffer layer (502a), and the distance between the boundary of the buffer layer (502a) and the boundary of the metallic lithium (Li) layer (503a) is equal in all sides around the metallic lithium (Li) layer (503a).

17. A method for producing a monolithic protected lithium cassette (PLC) anode, said method comprises:

providing a lithium ion conducting solid electrolyte substrate having a top surface and a bottom surface;

depositing an ionically conducting buffer layer on the top surface of said lithium ion conducting solid electrolyte substrate to obtain a first layer;

depositing a lithium (Li) metal layer on said first layer to obtain a second layer; and

depositing a protective layer of metal in an enveloping manner covering the second layer, the first layer, and the top surface of the substrate to obtain said monolithic PLC anode.

18. The method as claimed in claim 17, wherein the material of said buffer layer is at least one selected from the group consisting of Li2O, Li3PO4, Al2O3, V2O5, GeO2, Li2S, P2S5, Li2Ti3O7, Li3N, ßLiAlSiO4 and ZnO, preferably lithium phosphate (Li3PO4).

19. The method as claimed in claim 17, wherein the material of said protective layer of metal is at least one selected from the group consisting of Cu, Ni, Au, Pt and Al, preferably Cu.

20. The method as claimed in claim 17, wherein said buffer layer is deposited on said lithium ion conducting solid electrolyte substrate by at least one method selected from the group consisting of pulse laser deposition (PLD), atomic layer deposition (ALD), metal organic chemical vapour deposition (MOCVD), additive manufacturing (AM), radio frequency (RF) sputtering, DC sputtering and ion beam assisted deposition (IBAD).

21. The method as claimed in claim 17, wherein said lithium metal layer is deposited on said first layer by at least one method selected from the group consisting of thermal evaporation, electro-deposition, atomic layer deposition (ALD), and magnetic sputtering.

22. The method as claimed in claim 17, wherein said protective layer of metal is deposited on said second layer by at least one method selected from the group consisting of thermal evaporation, electro-deposition, magnetic sputtering and atomic layer deposition (ALD).

23. The method as claimed in claim 17, wherein the thickness of the lithium ion conducting solid electrolyte substrate, the buffer layer, the lithium metal layer, and the protective layer of metal is in the range of 100 µm to 250 µm, 0.1 µm to 4 µm, 0.5 µm to 5 mm and 2 µm to 15 µm respectively.

24. An electrochemical cell system, said system comprising:

a monolithic protected lithium cassette (PLC) anode (500), said anode containing

a lithium ion conducting solid electrolyte substrate (501a) having a top surface and a bottom surface;

an ionically conducting buffer layer (502a) deposited on the top surface of said substrate (501a);

a layer of metallic lithium (Li) (503a) deposited on said buffer layer (502a); and

a protective layer of metal (504a) deposited in an enveloping manner covering the metallic Li layer (503a), the buffer layer (502a), and the top surface of the substrate (501a); and

a cathode;

wherein the monolithic PLC anode is in ionic communication with said cathode via said lithium ion conducting solid electrolyte substrate.

25. The electrochemical cell system as claimed in claim 24, wherein the material of said buffer layer (502a) is at least one selected from the group consisting of Li2O, Li3PO4, Al2O3, V2O5, GeO2, Li2S, P2S5, Li2Ti3O7, Li3N, ßLiAlSiO4, and ZnO.

26. The electrochemical cell system as claimed in claim 24, wherein the material of said protective layer of metal (504a) is at least one selected from the group consisting of Cu, Ni, Au, Pt and Al, preferably Cu.

27. The electrochemical cell system as claimed in claim 24, wherein said lithium ion conducting solid electrolyte substrate is made of a material represented by the formula Li1+x+3zAlx(Ti,Ge)2-xSi3zP3-zO12, wherein 0 < x < 2 and 0< z < 2.

28. The electrochemical cell system as claimed in claim 24, wherein said lithium ion conducting solid electrolyte substrate is made of lithium ion conducting glass ceramics.

29. The electrochemical cell system as claimed in claim 24, wherein material of said cathode is at least one selected from the group consisting of lithium cobalt oxide (LiCoO2), lithium iron phosphate (LiFePO4), lithium cobalt phosphate (LiCoPO4), lithium nickel cobalt manganese oxide represented by formula Li[NixMnyCo(1-x-y)]O2,wherein 0= x=1 and 0= y=1, Lithium Nickel Cobalt Aluminium Oxide (LiNiCoAlO2), Lithium nickel manganese oxide (LNMO) (LiNi0.5Mn1.5O4), LiFePO4/Carbon nanocomposite, dilithium manganese orthosilicate (LMS) (Li2MnSiO4), air (oxygen), and sulphur.

30. The electrochemical cell system as claimed in claim 24, wherein the total surface area of the buffer layer (502a) is less than the total surface area of the substrate (501a), and the total surface area of the metallic lithium (Li) layer (503a) is less than the total surface area of the buffer layer (502a).

31. The electrochemical cell system as claimed in claim 24, wherein the distance between the boundary of the substrate (501a) and the boundary of the buffer layer (502a) is equal in all sides around the buffer layer (502a), and the distance between the boundary of the buffer layer (502a) and the boundary of the metallic lithium (Li) layer (503a) is equal in all sides around the metallic lithium (Li) layer (503a).

32. A hybrid electrochemical cell system, said system comprising:

a monolithic protected lithium cassette (PLC) anode (500), said anode comprising:

a lithium ion conducting solid electrolyte substrate (501a) having a top surface and a bottom surface;

an ionically conducting buffer layer (502a) deposited on the top surface of said substrate (501a);

a layer of metallic lithium (Li) (503a) deposited on said buffer layer (502a); and

a protective layer of metal (504a) deposited in an enveloping manner covering the metallic Li layer (503a), the buffer layer (502a), and the top surface of the substrate (501a);

a cathode; and

an electrolyte, wherein said electrolyte is at least one selected from the group consisting of an aqueous acidic electrolyte, an aqueous alkaline electrolyte, and a non-aqueous aprotic electrolyte;

wherein the monolithic PLC anode is in ionic communication with said cathode via at least one of said electrolytes.

33. The hybrid electrochemical cell system as claimed in claim 32, wherein the material of said buffer layer (502a) is at least one selected from the group consisting of Li2O, Li3PO4, Al2O3, V2O5, GeO2, Li2S, P2S5, Li2Ti3O7, Li3N, ßLiAlSiO4 and ZnO, preferably lithium phosphate (Li3PO4).

34. The hybrid electrochemical cell system as claimed in claim 32, wherein the material of said protective layer of metal (504a) is at least one selected from the group consisting of Cu, Ni, Pt, Au and Al, preferably Cu.

35. The hybrid electrochemical cell system as claimed in claim 32, wherein said solid electrolyte substrate is made of a material represented by the formula Li1+x+3zAlx(Ti,Ge)2-xSi3zP3-zO12, wherein 0 < x < 2 and 0 < z < 2.

36. The hybrid electrochemical cell system as claimed in claim 32, wherein said lithium ion conducting solid electrolyte substrate is made of lithium ion conducting glass ceramics (LICGC).

37. The hybrid electrochemical cell system as claimed in claim 32, wherein said cathode is made of at least one material selected from the group consisting of lithium cobalt oxide (LiCoO2), lithium iron phosphate (LiFePO4), lithium cobalt phosphate (LiCoPO4), lithium nickel cobalt manganese oxide represented by formula Li[NixMnyCo(1-x-y)]O2, wherein 0= x=1 and 0= y=1, Lithium Nickel Cobalt Aluminium Oxide (LiNiCoAlO2), Lithium nickel manganese oxide (LNMO) (LiNi0.5Mn1.5 O4), LiFePO4/Carbon nanocomposite, dilithium manganese orthosilicate (LMS) (Li2MnSiO4), air (oxygen) and sulphur.

38. The hybrid electrochemical cell system as claimed in claim 32 forms at least one of a lithium air rechargeable battery, a lithium air semi fuel cell, and a lithium metal-based all solid state battery.

39. The electrochemical cell system as claimed in claim 32, wherein the total surface area of the buffer layer (502a) is less than the total surface area of the substrate (501a), and the total surface area of the metallic lithium (Li) layer (503a) is less than the total surface area of the buffer layer (502a).

40. The electrochemical cell system as claimed in claim 32, wherein the distance between the boundary of the substrate (501a) and the boundary of the buffer layer (502a) is equal in all sides around the buffer layer (502a), and the distance between the boundary of the buffer layer (502a) and the boundary of the metallic lithium (Li) layer (503a) is equal in all sides around the metallic lithium (Li) layer (503a).