FIELD OF INVENTION
[001] The present subject matter described herein, relates to sodium doped cathode material for a lithium ion battery. More particularly, to a sodium salt doped Lithium Ferro Phosphate (LFP) or lithium-rich manganese (NMC) based cathode material for a lithium ion battery and method of preparation thereof.
BACKGROUND AND PRIOR ART AND PROBLEM IN PRIOR ART
[002] Since the invention of lead-acid batteries in 1859, the research community have been looking for a high energy density, long cycle life of the battery. Sony, Japan developed to study the rocking chair battery, which became a milestone in the history of the battery.
[003] In the era of rapid development of Li-ion batteries that have an unmatchable combination of high energy and power density, making the Li-ion technology a choice for portable electronics, power tools, and hybrid/full electric vehicles. If electric vehicles (EVs) replace the majority of gasoline powered transportation, Li- ion batteries will significantly reduce greenhouse gas emissions. The high energy efficiency of Li-ion batteries may also allow their use in various electric grid applications, including improving the quality of energy harvested from wind, solar, geo-thermal and other renewable sources, thus contributing to their more widespread use and building an energy-sustainable economy. Therefore Li-ion batteries are of intense interest in the recent years.
[004] Since the introduction of lithium-ion battery, the specific capacity of cathode material is always lower than the graphite anode which has capability to store more li-ions while charging. Various research has been

carried out to improve its specific capacity in order to enhance the specific energy density of cathode material in order to utilize the anode’s capacity.
[005] Li-ion batteries have certain fundamental advantages over other chemistries. Firstly, Li has the lowest reduction potential of any element, allowing Li based batteries to have the highest possible cell potential. Also, Li is the third lightest element and has one of the smallest ionic radii of any single charged ion. These factors allow Li-based batteries to have high gravimetric and volumetric capacity and power density. Finally, although multivalent cations allow for higher charge capacity per ion, the additional charge significantly reduces their mobility. Given that ionic diffusion in the solid electrodes is often the rate-limiting factor for battery power performance, this presents an enormous hurdle for the development of such alternative synthesis methods.
[006] As most of the current commercial cathode materials are developed by doping of electrochemically inactive elements such as Mg, Al, and Mn and that resulted in enhancement in electrochemical performance of full battery cell. Much research has focused on the development of the LiNi1-xCoxO2 (NC)2–10 cathode due to its high capacity (~275 mAh/g) and favourable operating cell voltage (4.3 V vs. Li/Li+), which is within the voltage stability window of current liquid electrolytes. Significant efforts are made on improving structural stability by doping with small amounts of electrochemically inactive elements such as Aluminium (Al). One of the most promising compositions that emerged is Li1Ni0.8Co0.15Al0.05O2 (NCA), currently in widespread commercial use. This intercalation material exhibits solid solution behaviour during the extraction of lithium.
[007] Using sodium as a doping agent for LMO battery has been well documented in Guo et al. [1] and resulted in the oxidation of Mn3+ ions to Mn4+ ion in order to electrochemically stabilize the spinel type material using small amount of Na. The cathode was synthesized by the sol-gel

technique keeping the weight ratio of Li: Mn as 1.05:2. The resulting phase was Li1.05Mn2O4 with small concentrations of Na doped into the host structure. The synthesized pristine and sodium substituted material displays the cubic spinel structure. There are 3 major sites where the Na of the doped sample can appear, mainly the tetrahedral 8(a) site, the octahedral 16(d) site utilized by Mn ions and then the octahedral 16(c) sites, which actively play the role in Li diffusion during cycling. The reported positions where the Na occupied was the tetrahedral (8a) sites and caused the Lithium to shift to the octahedral (16d) sites and in process replacing the Mn ions. It is reported that the capacity of Li1.05Mn2O4 decreases with increasing concentration of Na doped into the structure. This capacity fading can be attributed to the conversion of Mn3+ to Mn4+ due to Na’s doping in the manganese spinel structure. As previously stated with increasing amounts of Na incorporated into crystal structure of the material, the Mn in the octahedral (16d) sites gets replaced by the Li ions arriving from the tetrahedral (8a) sites. This will result in the oxidation of Mn3+ ions to Mn4+ ion in order to electrochemically stabilize the spinel material.
[008] Dong et al. [2] worked on Na-substituted Li2xNaxMnO3 (x = 0.00, 0.02, 0.05, 0.10, 0.15 and 0.20) cathode material synthesized through the solid-state reaction. The Li1.9Na0.1MnO3 cathode material shows improved rate performance and cyclic stability compared to the pristine material (Li1.9Na0.1MnO3). It shows a capacity of ~181 mAh/g at 0.1C rate, with a capacity retention of 99.3% after 45 cycles. Even at an increased C-rate (0.5C), the capacity is stable at ~158 mAh/g with retention of 98.6% for 100 cycles.
[009] Okamoto [3] reported O2 evolution during Li-ion extraction, which causes a loss in volume and deforms the crystal structure thereby impeding cyclability of Li2MnO3. The incorporation of Na in the structure of LMO resulting in Li1.9Na0.1MnO3 cathode material successfully limits

oxygen evolution during the charging process by stabilizing the structure. It is however to be noted that excessive Na content in the host structure has resulted in the formation of Na2Mn3O7 phase which destabilizes the crystal structure and unit cell shrinkages and thus negatively impacting Li-ion diffusion and cyclability.
[0010] The synthesis route of LiMPO4 is generally solid-state or sol-gel reaction [4-7]. Specifically, the effects of Na-doping and Na/V co-doping in LiFePO4 have been studied by Yin et al. [4] and Yang et al. [7], respectively, and their findings complement each other. The Na-doped Li1xNaxFePO4/C system studied by Yin et al. [4] reports that doping in 0 ≤ x ≤ 0.05 worth of Na that a ratio of 0.03 Na was optimal. It is reported that the smaller ratios of Na would provide a negligent change in the lattice size, and the system does not experience an improved Li-ion diffusion pathway. However, the upper limit of the ratio at 0.05 Na produced counter- productive results.
[0011] Patent Publication No. CN105895887B discloses a method for
multi-element doping in lithium ion battery’s cathode materials to
enhance the electronic conductivity electrodes. This invention describe the
method of preparation of LixAaMbPOyNnSm material. In this formulae,
A Ti, Zr, Al, V, one or more of Cr and W ; M is Fe, Co, one or more of
Mn and
Ni ; 0.8≤x≤1.2 ; 0≤a≤0.1 ; 0≤b≤1.1 ; 3≤y≤4 ; 0≤n≤0.2 ; 0≤m≤0.2.In metallic element position containing transition metal cation and in oxygen place doped nitrogen or element sulphur, the cell parameter of phosphate cathode material can be changed simultaneously in the present invention, improves transmission speed of the lithium ion in lattice, improves ionic conductivity ; Phosphate electronic structure can be changed simultaneously, improve electronic conductivity. The experimental results showed that the electronic conductivity of multi-element doping

phosphate cathode material is 10 -6~10- 4s/m. No coin cells or full cell data for electrochemical performance not reported in this patent.
[0012] Patent Publication No. CN111048775A discloses an in-situ sodium-doping modification method for improving lithium storage performance of a ternary cathode material, which uses CH3COONa is Na source, stirring and mixing with NCM622 (NMC type) precursor of nickelic ternary positive electrode material in absolute ethyl alcohol, directly drying the obtained material at high temperature, and then mixing the obtained material with excessive LiOH & H2. Grinding and mixing O, and then calcining the mixed material at high temperature to obtain Na+And (4) doping.
[0013] Patent Publication No. CN110797527A provides a preparation method of a modified lithium-rich manganese-based oxide anode material, which comprises the steps of mixing and stirring a nickel-cobalt-manganese precursor after pre-sintering, an alkali metal salt and a lithium source in a solvent, drying and calcining to obtain the modified lithium-rich manganese-based oxide anode material.
OBJECTS OF THE INVENTION
[0014] It is therefore the object of the invention to overcome the aforementioned and other drawbacks in prior art.
[0015] The principal objective of the present invention is to provide for sodium doped cathode materials for a lithium ion battery.
[0016] Another object of the present invention is to develop a method for the preparation of high-energy lithium ion battery cathode material Lithium Ferro Phosphate or Lithium Nickel Manganese Cobalt by small amount of “Na” doping through hydrothermal/solvo-thermal/solid state synthesis process.
[0017] These and other objects and advantages of the present subject matter would be apparent to a person skilled in the art after

consideration of the following detailed description taken into consideration with accompanying drawings in which preferred embodiments of the present subject matter are illustrated.
SUMMARY OF THE INVENTION
[0018] One or more drawbacks of the conventional technology based on existing apparatus and processes are overcome, and additional advantages are provided through a novel sodium doped cathode material for a lithium ion battery comprising of doping of sodium element in the Lithium Ferro Phosphate or Lithium Nickel Manganese Cobalt type cathode materials in enhancing Li ion diffusion.
[0019] Additional features and advantages are realized through the technicalities of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered to be a part of the claimed disclosure.
[0020] In an embodiment of the present subject matter, the sodium doped cathode material for a lithium ion battery comprises sodium salt doped LFP or lithium-rich manganese having general formula
LixNa1-xFePO4 or LixNa1- xNi0.2Mn0.2CO0.6O2 wherein x is equal to or
greater than 0.98.
[0021] In another embodiment of the present subject matter, the sodium salt is one selected from Na2CO3, NaCOOCH3 and NaNO3. [0022] In another embodiment of the present subject matter, the doped quantity of sodium elements is in the range 0.1-2%.
[0023] In another embodiment of the present subject matter, a method of preparing sodium doped cathode material for a lithium ion battery comprising preparing ingredient materials in a predefined stoichiometric range; mixing homogenously samples of lithium, nickel, manganese, ferrous and cobalt for preparing a solid- state material; and mixing the samples with a solvent. The doping quantity of sodium is in the range of 0.1% to 2%.Further, the mixing of samples

with a solvent is carried out using solvo-thermal process. The mixing of
samples is carried out in a ball miller through solid-state synthesis process.
[0024] It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined to form a further embodiment of the disclosure.
[0025] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.
DETAILED DESCRIPTION
[0026] The detailed description of various exemplary embodiments of the disclosure is described herein with reference to the accompanying drawings. It should be noted that the embodiments are described herein in such details as to clearly communicate the disclosure. However, the amount of details provided herein are not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the present disclosure as defined by the appended claims.
[0027] It is also to be understood that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the present disclosure. Moreover, all statements herein reciting principles, aspects, and embodiments of the present disclosure, as well as specific examples, are intended to encompass equivalents thereof.
[0028] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a",” “an” and “the” are intended to include the plural forms as well, unless the context clearly

indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes” and/or “including,” when used herein, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups thereof.
[0029] It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may, in fact, be executed concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved.
[0030] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, e.g., those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
[0031] The present disclosure discloses a novel sodium doped cathode material for a lithium ion battery comprising of doping of sodium element in the Lithium Ferro Phosphate or Lithium Nickel Manganese Cobalt type or similar cathode materials in enhancing Li ion diffusion.
[0032] In accordance with an embodiment of the present subject matter, the sodium doped cathode material for a lithium ion battery comprises sodium salt doped LFP or lithium-rich manganese having general formula wherein x is equal to or greater than 0.98. The sodium salt is one selected from Na2CO3, NaCOOCH3 and NaNO3 and the doped quantity of sodium elements is in the range 0.1-2%.

[0033] In another embodiment of the present subject matter, a method of preparing sodium doped cathode material in Lithium Ferro Phosphate or Lithium Nickel Manganese Cobalt for a lithium ion battery using Solvo-thermal/Solid-state synthesis process is disclosed. The method comprising preparing samples of lithium, nickel, manganese, ferrous and cobalt in a pre-determined stoichiometric quantity, mixing homogenously the samples of lithium, nickel, manganese, ferrous and cobalt in a ball miller through solid-state synthesis process for preparing a solid- state material and mixing the samples with a solvent in solvo-thermal process. [0034] These and other advantages of the present subject matter would be described in greater detail with reference to the following figures. It should be noted that the description merely illustrates the principles of the present subject matter. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described herein, embody the principles of the present subject matter and are included within its scope.
PREFFERED EMBODIMENT:
[0035] In the preferred embodiment, a method of preparing sodium doped cathode material for a lithium ion battery comprising steps of preparing ingredient materials in a predefined stoichiometric range, mixing homogenously samples of lithium, nickel, manganese, ferrous and cobalt for preparing a solid- state material and mixing the samples with a solvent. doping quantity of sodium is in the range of 0.1% to 2%. The mixing of samples with a solvent is carried out using solvo-thermal process. The mixing of samples is carried out in a ball miller through solid-state synthesis process.
TECHNICAL ADVANTAGES:
[0036] There is a significant improvement in the “Li” ion diffusion due to doping of “Na” in small quantity (< 0.1%). Na doping enables the changes in the morphology of particles that significantly improve the

electrochemical performance. Some of lithium ion cathode chemistry showed that excellent rate capacity and cycle stability due to its ac facet morphology, larger lattice parameter.
[0037] It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should

be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B.”
[0038] It will be further appreciated that functions or structures of a plurality of components or steps may be combined into a single component or step, or the functions or structures of one-step or component may be split among plural steps or components. The present invention contemplates all of these combinations. Unless stated otherwise, dimensions and geometries of the various structures depicted herein are not intended to be restrictive of the invention, and other dimensions or geometries are possible. In addition, while a feature of the present invention may have been described in the context of only one of the illustrated embodiments, such feature may be combined with one or more other features of other embodiments, for any given application. It will also be appreciated from the above that the fabrication of the unique structures herein and the operation thereof also constitute methods in accordance with the present invention. The present invention also encompasses intermediate and end products resulting from the practice of the methods herein. The use of “comprising” or “including” also contemplates embodiments that “consist essentially of” or “consist of” the recited feature.
[0039] Although embodiments for the present subject matter have been described in language specific to structural features, it is to be understood that the present subject matter is not necessarily limited to the specific features described. Rather, the specific features and methods are disclosed as embodiments for the present subject matter. Numerous modifications and adaptations of the system/component of the present invention will be apparent to those skilled in the art, and thus it is intended by the appended claims to cover all such modifications and adaptations, which fall within the scope of the present subject matter.

We Claim:
1. A sodium doped cathode material for a lithium ion battery, the material comprises sodium salt doped Lithium Ferro Phosphate (LFP) having general formula LixNa1-xFePO4 where x=0.98-0.99.
2. A sodium doped cathode material for a lithium ion battery, the material comprises sodium salt doped lithium-rich manganese (NMC) having general formula LixNa1- xNi0.8Mn0.2CO0.2O2 where x=0.98-0.99.
3. The sodium doped cathode material for a lithium ion battery as claimed in claim 1 or 2, wherein sodium salt includes Na2CO3, NaCOOCH3 and NaNO3.
4. A method of preparing sodium doped cathode material for a lithium ion battery, the method comprising:
preparing ingredient materials in a predefined
stoichiometric range;
mixing homogenously samples of lithium, nickel, manganese, ferrous and cobalt for preparing a solid- state material; and
mixing the samples with a solvent.
6. The method of preparing sodium doped cathode material for a lithium ion battery as claimed in claim 6, wherein doping quantity of sodium is in the range of 0.1% to 2%.
7. The method in of preparing sodium doped cathode material for a lithium ion battery as claimed in claim 6, wherein mixing of samples with a solvent is carried out using solvo-thermal process.
8. The method in of preparing sodium doped cathode material for a
lithium ion battery as claimed in claim 6, wherein mixing of samples is
carried out in a ball miller through solid-state synthesis process.