Description:FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patent Rules, 2003
COMPLETE SPECIFICATION
(See sections 10 & rule 13)
1. TITLE OF THE INVENTION
POSITIVE ELECTRODE FOR SODIUM ION BATTERY AND PREPARATION METHOD OF THE SAME
2. APPLICANT (S)
NAME NATIONALITY ADDRESS
INDIGENOUS ENERGY STORAGE TECHNOLOGIES PVT. LTD. IN I-10, 2nd Floor, Tides Business Incubator, IIT Roorkee, Roorkee-247667, Uttarakhand, India.
3. PREAMBLE TO THE DESCRIPTION
COMPLETE SPECIFICATION

The following specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF INVENTION:
[001] The present invention relates to the field of sodium ion battery. The present invention in particular relates to a positive electrode material using an innovative aqueous binder for a sodium-ion battery, and a producing method and use thereof.
DESCRIPTION OF THE RELATED ART:
[002] Sodium-ion batteries are gaining attention as a promising alternative to lithium-ion batteries due to the abundance and cost-effectiveness of sodium, which is widely available as NaCl in water bodies and various parts of the Earth. This invention aims to develop a sustainable and high-performance positive electrode slurry for sodium-ion batteries as Na-ion batteries are composed of four basic components: two electrodes (anode and cathode), separator, and electrolyte. The electrode manufacturing process involves coating of slurry on metallic substrate, known as the current collector. This slurry consists of active material particles, conductive additives (CA), binder (BA), and a solvent. The preparation of the slurry is a critical step as it directly impacts the morphology, mechanic al performance of the electrodes and, consequently, the performance of the battery. The mixing conditions during slurry preparation play a significant role. The choice of solvent used in the slurry also influences the mixing process. Slurries can be categorized as either aqueous-based or organic solvent-based. N-Methyl-2-pyrrolidone (NMP) is a commonly used organic solvent in Na-ion batteries.
[003] Reference may be made to the following:
[004] IN Publication No. 4680/CHENP/2010 relates to a positive electrode active material and a method for producing an olivine-type phosphate. The positive electrode active material comprises an olivine-type phosphate represented by the following formula (I), wherein the maximum peak in an X-ray diffraction pattern obtained using a CuKa ray is the peak of the (031) plane of the olivine-type phosphate and the half-value width of the peak is 1.5° or less,: AaMbPO4 (I), wherein A represents one or more elements selected from among alkali metals; M represents one or more elements selected from among transition metals; a is from 0.5 to 1.5; and b is from 0.5 to 1.5.
[005] IN Publication No. 4864/CHENP/2010 relates to a positive electrode active material that can suppress the necessity of performing sieving and is suitable for use in secondary batteries, particularly sodium secondary batteries.
[006] IN Publication No. 35/CHENP/2011 relates to a transition metal phosphate and a production process thereof, a positive electrode, and a sodium secondary battery. The transition metal phosphate contains sodium (Na), phosphorus (P) and a transition metal element and having a BET specific surface area of 1 m/g to 50 m^/g. The process for producing a transition metal phosphate comprises steps and: a step of bringing a phosphorus (P) source, a sodium (Na) source, an M source (M is one or more transition metal elements) and water into contact with each other, and obtaining a liquid material thereby, and a step of separating water from the liquid material and obtaining a transition metal phosphate thereby.
[007] IN Publication No. 1461/DELNP/2014 relates to a sodium battery comprising a positive electrode containing a positive electrode active material, a negative electrode, an electrolyte, a positive electrode current collector and a negative electrode current collector, wherein the positive electrode active material for a sodium battery, has a crystal structure belonging to the space group Pn21a and is represented by the general formula below: NaxMy(AO4)z(P2O7)w M is at least one selected from the group consisting of manganese, cobalt, and nickel; A is at least one selected from the group consisting of silicon, phosphorus, and sulfur; x satisfies the condition 4 = x = 2, y satisfies the condition 4 = y = 1, z satisfies the condition 4 = z = 1, w satisfies the condition w = 1.
[008] IN Publication No. 202117030953 relates to a positive electrode active material and a preparation method therefor, and a sodium-ion battery and a device comprising same. The positive electrode active material satisfies the following chemical formula: Na0.67MnxAyBzO2±d.
[009] Publication No. CN115863565 provides a sodium ion battery positive electrode mixed material, a pole piece, slurry and a preparation method. The sodium ion battery positive electrode mixed material comprises a binder, a conductive additive and a sodium ion battery active material, wherein the binder is SEBS (styrene-ethylene-butylene-styrene) rubber.
[010] Publication No. CN115784325 discloses a preparation method of a sodium-ion battery positive electrode material suitable for energy storage application. The general formula of the sodium-ion battery positive electrode material is Na < x > Ni < a > M < b > N < c > O < 2 >, in the formula, M is at least one of Cu, Mn, Al, Co, Mg and Zn, N is at least one of Zr, Ti, Ba, Mo, Nb, La and Sr, x is greater than or equal to 0.9 and less than or equal to 2.0, a is greater than 0 and less than or equal to 1.0, b is greater than 0 and less than or equal to 1.0, c is greater than 0 and less than or equal to 0.1, and a + b + c = 1.
[011] Publication No. CN115799469 discloses sodium-ion battery positive electrode slurry and a preparation method thereof, a positive plate and a sodium-ion battery. The preparation method of the sodium-ion battery positive electrode slurry comprises the following steps: mixing N-methyl pyrrolidone, cholesteryl dodecyl carbonate and a weakly acidic substance to obtain a solution; mixing the obtained solution with a binder to obtain a glue solution; mixing the obtained glue solution with a conductive agent to obtain a conductive adhesive; and mixing the obtained conductive adhesive with a sodium-containing layered transition metal oxide to obtain the sodium-ion battery positive electrode slurry.
[012] Publication No. CN115663179 relates to sodium-ion battery positive electrode slurry, a positive electrode plate, a battery and a preparation method. According to the sodium ion battery positive electrode slurry provided by the invention, sodium iron phosphate is used as a positive electrode active material and is matched with the sodium supplementing agent, and sodium ions consumed for forming a solid electrolyte membrane are supplemented in the step of the first formation process; the invalid sodium ions are embedded into the negative electrode and cannot be separated in the subsequent circulation process, so that the energy density and the first coulombic efficiency of the sodium-ion battery are remarkably improved; due to the fact that a strong alkaline solution can be generated after the sodium ferrite is added, the alkalinity of the positive electrode slurry is improved, the viscosity of the slurry is too high, the agglomeration phenomenon is serious, and the later pole piece processing performance is greatly influenced, the organic acid is added to neutralize alkalinity, and the problems are avoided; and meanwhile, a large amount of gas can be generated in the sodium supplementing process, and the inventor completely exhausts the gas generated in the sodium supplementing process through specific formation and aging processes and ensures that the risk of gas generation does not exist in subsequent circulation.
[013] Publication No. CN115611258 discloses a preparation method of a sodium ion battery positive electrode material Na3Fe2(PO4)P2O7, and belongs to the technical field of sodium ion battery positive electrode materials, the method comprises the following steps: weighing FePO4, sodium phosphate, a supplementary iron source and a carbon source for later use, with the molar ratio of sodium element to iron element to phosphorus element being 3: 2: 3; dissolving sodium phosphate salt in deionized water to form an aqueous solution with the concentration of 0.1-1.5 mol/L; uniformly mixing FePO4, a supplementary iron source and a carbon source with the mass fraction of 30-80%, then adding the aqueous solution obtained in the step mixing, then sanding by using a sand mill until the particle size is 0.1-2 microns, and then adding the residual carbon source; carrying out spray drying on the sanded slurry to obtain precursor particles; and sintering the precursor particles in an inert atmosphere to obtain the Na3Fe2(PO4)P2O7powder.
[014] Publication No. CN115513462 discloses a method for optimizing a sodium ion positive electrode material neutralizing additive and an addition amount, the optimization method comprises the following steps: 1, assembling a plurality of groups of sodium ion batteries with different types of neutralizing acids; 2, forming each group of sodium ion batteries by using a high-precision battery test system; 3, carrying out alternating current impedance test by adopting an electrochemical workstation; 4, forming the data to obtain gram capacity exertion and first discharge efficiency of different power failure of each group, removing a maximum value and a minimum value from the power failure data of each group, removing abnormal data, and averaging the rest data; the Na < + > diffusion coefficient is calculated through impedance fitting data, the ohmic internal resistance and the charge transfer internal resistance are obtained, the type selection and the adding amount of the neutralizing additive can be rapidly determined according to sodium ion battery positive electrode materials produced by different manufacturers, the processing performance of the slurry is improved and meanwhile the electrochemical performance is guaranteed.
[015] Publication No. CN115395013 discloses a preparation method of a double-ion sodium battery positive electrode material, which comprises the following steps: uniformly mixing commercial graphite, acetylene black and polyvinylidene fluoride, adding N-methyl pyrrolidone to adjust to viscous active substance slurry, coating an aluminum sheet with the viscous active substance slurry, and drying to obtain a working electrode; assembling a graphite sodium half-cell by taking metal sodium as a counter electrode, dissolving a mixed solution of EC, DMC and EMC with NaClO4 in an electrolyte and taking glass fiber GF/D as a diaphragm; a half cell is subjected to electrochemical pretreatment under the conditions that the voltage window is 0.1-1.8 V and the current density is 10 mA g < 1 >, a graphite electrode coated with a pre-constructed SEI film is obtained after charging and discharging are conducted five times, the electrode shows excellent electrochemical performance when used as a double-ion sodium battery positive electrode, the SEI film on the surface of the electrode is uniform, stable and compact, interface side reactions are effectively reduced, the service life of the electrode is prolonged, and the service life of the electrode is prolonged.
[016] Publication No. CN115275159 provides a battery positive electrode material, a sodium ion battery and electric equipment. The sodium content of one side, close to a particle internal region, in a particle external region of the battery positive electrode material is greater than the sodium content of the particle surface; the particle internal area refers to an area from the particle center to 90% of the radius in the direction from the particle center to the particle surface; the particle outer region refers to a region within a range from 90% of the radius to the particle surface.
[017] Publication No. CN115275205 discloses a sodium ion battery positive electrode slurry, and a preparation method and an application thereof. The sodium-ion battery positive electrode slurry comprises a positive electrode active material and a solvent, the positive electrode active material comprises a positive electrode active material, a positive electrode conductive agent and a positive electrode binder, and the sodium-ion battery positive electrode slurry further comprises a first additive and a second additive; the first additive comprises organic acid, the second additive comprises sodium ions, and the second additive and the first additive form a pH buffer system.
[018] Publication No. CN115241432 discloses a sodium ion battery positive electrode sodium supplementing method which comprises the following steps: S1, mixing a positive electrode sodium supplementing agent with a solvent A, and fully sanding and dispersing in a sand mill to obtain slurry B; s2, mixing ferrous sulfate and sodium sulfate through deionized water, then adding a conductive agent, stirring and uniformly mixing to obtain slurry A, then mixing the slurry A with the slurry B, and then carrying out spray granulation to obtain a positive electrode material precursor; and S3, calcining the positive electrode material precursor in a nitrogen atmosphere to obtain the positive electrode material NaxFey(SO4)z with the composite sodium supplementing agent.
[019] Publication No. CN217624792 discloses a sodium ion battery positive electrode slurry transfer temporary storage device which comprises a bottom plate and a stirring barrel fixed at the top of the bottom plate, a top plate is fixed above the stirring barrel, a fixed shell is fixed at the bottom of the top plate, a stirring shaft is rotatably arranged on the fixed shell in a penetrating manner, and a rack is fixed at the top of the fixed shell. A driving motor is fixed at the top of the inner wall of the rack.
[020] Publication No. CN115132987 discloses a preparation method of a multi-layer coated sodium ion battery positive electrode material, which comprises the following steps: S1, uniformly mixing transition metal oxide particles and polyanion compound particles in a first dispersion medium to obtain first slurry; performing spray drying on the first slurry to obtain first particles; s2, uniformly mixing the first particles and an organic carbon source in a second dispersion medium to obtain second slurry; performing spray drying on the second slurry to obtain second particles; and S3, carbonizing the second particles in an inert atmosphere to obtain the multi-layer coated sodium ion battery positive electrode material.
[021] Publication No. CN115117302 discloses a preparation method of aqueous positive electrode slurry of a sodium-ion battery, a pole piece and the sodium-ion battery. The preparation method comprises the following steps: S1, material preparation; S2, material mixing; and S3, parameter adjustment. The preparation method of the aqueous positive electrode slurry of the sodium-ion battery has the characteristics of low cost, excellent electrochemical performance, good stability and simple process.
[022] Publication No. CN115084522 discloses a sodium ion battery positive electrode slurry additive, and relates to the field of battery positive electrode materials, and the sodium ion battery positive electrode slurry additive comprises 30-80 wt% of carboxylic ester, 10-50 wt% of organic acid, and 10-50 wt% of unsaturated fatty acid.
[023] Publication No. CN115084484 relates to a sodium-ion battery positive electrode material as well as a preparation method and application thereof. The preparation method of the sodium ion battery positive electrode material comprises the following steps: (A) grinding a mixture of sodium borohydride and ferromanganese hydroxide to obtain first slurry, and performing spray drying and calcination on the first slurry to obtain a first calcined material; and (B) grinding a mixture of the first calcined material, a carbon source, a vanadium source, sodium bicarbonate and water to obtain second slurry, and sequentially carrying out spray drying, calcination, crushing, screening and iron removal on the second slurry to obtain the sodium ion battery positive electrode material.
[024] Publication No. CN114695893 relates to positive electrode slurry in particular to sodium ion positive electrode slurry and a preparation method thereof. The sodium ion positive electrode slurry comprises the following raw materials in parts by weight: 90-95.5 parts of a sodium ion positive electrode material, 0.1-1 part of a dispersing agent and 0.1-2 parts of organic weak acid, the dispersing agent is sodium polyepoxysuccinate; the organic weak acid is selected from one or more of oxalic acid, malic acid, gluconic acid, lauric acid, n-decanoic acid and palmitic acid.
[025] Publication No. CN114613946 discloses a manufacturing method of a sodium ion battery electrode plate and a semi-solid sodium ion battery. The method comprises the following steps: adding ethylene glycol monobutyl ether into a reaction kettle, adding a free radical initiator into an acrylate monomer mixture, uniformly dissolving, and dripping into the reaction kettle; a polymer electrolyte is prepared by taking a high polymer material as a framework material and embedding sodium salt; dissolving the polymer electrolyte in a reaction kettle, heating, drying, vacuumizing and removing a reaction solvent in sequence to obtain an ionic conductive polymer; preparing a shell by using an ionic conductive polymer, and wrapping an electrode material to form a core-shell material; a step in which a thickener powder containing a core-shell material is sieved to obtain a sieved portion of the thickener powder, and a water-based electrode slurry is prepared by mixing an electrode active material, a water-based binder, the sieved portion, and a water-based medium; and carrying out hot rolling treatment on the coated pole piece to obtain the electrode pole piece, so that the first reversible capacity of the semi-solid battery is higher.
[026] Publication No. CN114497521 provides sodium ion battery positive electrode slurry and a preparation method thereof. In order to solve the problems of poor battery consistency, poor dispersity, agglomeration of small-particle-size particles, influence on battery performance and the like caused by easy wetting and gelling of the existing sodium-ion battery positive electrode material in the homogenizing process, the invention provides the sodium-ion battery positive electrode slurry and the preparation method thereof.
[027] Publication No. CN114400303 discloses positive electrode slurry for a sodium-ion battery. The positive electrode slurry comprises a main material, a conductive auxiliary material is provided; an adhesive auxiliary material is arranged; having a solvent; wherein the main material is sodium manganate or sodium ferric phosphate; wherein the conductive auxiliary material is one of carbon black, graphene and conductive graphite; wherein the adhesive auxiliary material is polyvinylidene fluoride; wherein the solvent is NMP.
[028] Publication No. CN114122311 discloses a preparation method of a Na2FePO4F/C positive electrode active material, which comprises the following steps: dispersing iron phosphate, organic acid sodium, a sodium source and a fluorine source in water, and carrying out mechanical activation modification to obtain slurry; the organic acid sodium is at least one of sodium dicarboxylate with the carbon number of 2-10, sodium polycarboxylate and hydroxyl-containing sodium carboxylate; the molar ratio of the iron phosphate to the organic acid sodium is (2-10): 1; (2) carrying out spray drying treatment on the slurry to obtain a precursor; and (3) carrying out calcination treatment on the precursor, so as to obtain the Na2FePO4F/C positive electrode active material.
[029] Publication No. CN113972358 discloses a preparation process and device of a sodium ion battery positive electrode material. The preparation process comprises two steps, namely, preparing a positive electrode active material and preparing a positive plate roll material; the device comprises a machine base, a diaphragm discharging device, a positive electrode roll material winding device, a slurry discharging device, a slurry flattening mechanism, a drying device and a rim charge cutting device; and a hot air-drying assembly and a hot-pressing roller compaction drying assembly are arranged in the drying device.
[030] Publication No. CN113437261 discloses a Prussian blue positive plate, a sodium ion battery and a preparation method. The preparation method of the Prussian blue positive plate comprises the following steps: dissolving a binder in a solvent to form a glue solution; adding a Prussian blue positive electrode active material and a conductive agent into the glue solution, and uniformly mixing to obtain positive electrode slurry; coating and drying the positive electrode slurry to obtain a Prussian blue positive electrode plate; wherein the mass ratio of the Prussian blue positive electrode active material to the conductive agent to the binder is (7-8): (1-2): 1.
[031] Publication No. CN110165208 discloses a preparation method of a layered nickel-based positive electrode material for a sodium ion battery. The Ni-Co-Mn ternary hydroxide and LiOH.H2O are taken to be ground and mixed and then cooled and ground again after primary sintering, and a ternary layered nickel-based positive electrode material is obtained through secondary sintering; the ternary layered nickel-based positive electrode material, a carbon black conductive agent and a polyvinylidene fluoride binder are added to N, N-dimethyl pyrrolidone to be stirred to form slurry; the slurry is dried and thermally rolled so as to prepare a lithium ion battery positive electrode sheet to be assembled into a lithium ion battery; the lithium ion battery is charged at the constant current to remove lithium ions from the structure framework of the battery positive electrode sheet, and the battery positive electrode sheet is taken out; the sodium ion battery is formed by assembling the battery positive electrode sheet, a metal sodium counter electrode and an electrolyte; and constant current discharging of the sodium ion battery enables the sodium ions to be embedded in the structure framework of the battery positive electrode sheet so as to prepare the sodium ion positive electrode material.
[032] Publication No. CN108539141 provides a preparation method of ternary layered positive electrode material for a sodium ion battery. The preparation method comprises the following steps: mixing sodium carbonate, manganese monoxide, ferrous oxide and nickel oxide according to a given ratio, adding deionized water, preparing the mixture slurry with a solid content of 30 to 45 percent, ball milling, obtaining a uniformly-mixed raw material with small particles, obtaining a precursor in an atomizing manner, wherein the precursor consists of spherical particles formed by clustering small particles, calcining the spherical particles at high temperature, preserving the heat for a given time, cooling, and obtaining the needed NaMn1-x-yFexNiyO2(x is greater than 0 and less than 0.5, and y is greater than 0 and less than 0.5) positive electrode material.
[033] Publication No. CN108336334 provides a preparation method of a high-performance sodium-ion battery cathode material. The method comprises the following steps of mixing sodium carbonate, manganic oxide and titanium dioxide, adding an obtained mixture into a ball milling tank, adding absolute ethyl alcohol, then performing ball milling, tableting and calcining in a ball mill for 20 to 25h, cooling to room temperature, performing tabletting again, calcining at 730 to 780 deg c to obtain an active material Na4Mn4Ti5O18; then adding the active material, a conductive agent Ketjen Black (KB) and an aqueous solution of a binding agent sodium carboxy methylcellulose (CMC) into the ball milling tank, adding water and performing ball milling for 3 to 5h, so as to prepare slurry; then coating a current collector Alfoil with the slurry to prepare an electrode sheet, performing vacuum drying to obtain the high-performance sodium-ion battery cathode material.
[034] Publication No. CN106602071 provides positive electrode slurry for a sodium ion battery and a preparation method for the positive electrode slurry, and applicable to slurry preparation for the positive electrode material of the sodium ion battery with a high pH value.
[035] Publication No. WO2022160534 discloses a sodium-ion battery positive electrode material, a preparation method therefor and the use thereof. The chemical composition of the sodium-ion battery positive electrode material is NaxNiyM1-yO2@conductive carbon, wherein 0.5 = x = 1, 0.1 = y = 0.5, M is selected from at least one of Mn, Fe, Zn, Ag, Zr, Mo, Nb, Cu, Cr and Ti, and the conductive carbon is selected from at least one of graphene, carbon nanotubes, a conductive carbon black and acetylene black; the content of the conductive carbon in the sodium-ion battery positive electrode material is 1-10 wt%; the specific surface area of the sodium-ion battery positive electrode material is 0.3-1.2 m2/g; and/or the D50 particle size of the sodium-ion battery positive electrode material is 5-30 nm.
[036] However, NMP poses challenges as it is flammable and toxic, requiring the implementation of recovery systems to mitigate environmental hazards. On the other hand, aqueous-based slurries use water as the solvent, eliminating the drawbacks associated with organic solvents and providing a more cost-effective option. Carboxymethyl cellulose (CMC) is often used as a substitute for PVDF in aqueous systems due to its lower cost. However, the use of aqueous slurries requires extra care due to strong hydrogen bonding, which can lead to particle agglomeration. Aqueous slurries also exhibit higher surface tension, which can impact the wetting ability of the slurry on the current collector. To address this, a co-solvent can be added to reduce the surface tension. However, the high surface tension of aqueous slurries may result in electrode cracking issues during the drying process. To enhance the adhesivity of the slurry and achieve desirable surface tension and contact angle characteristics, a modification can be made to the binder.
[037] The sodium-based positive electrode of high energy density, is required for producing a sodium-ion battery of specific capacity, high energy density exhibiting excellent cycle characteristics and high-speed charging/discharging performance with low internal resistance.
[038] In order to overcome above listed prior art, the present invention aims to provide a positive electrode material design for a Na-ion battery having better electrochemical performance.
[039] Present invention provides preparation of a sodium-ion battery positive electrode, emphasizing the slurry composition, its application onto a collector foil, subsequent drying and the optimization of electrode thickness, porosity, and tortuosity. It modifies the binder using the suitable additives to get better adhesivity and wettability of slurry. The additive changes the viscosity of the binder and results in suitable surface tension and contact angle of slurry on the current collector. The peel strength of the positive electrode has been altered due to the binder modification.
[040] A wide range of binders, including sodium alginate, chitosan, lithium and sodium salts of carboxymethyl cellulose (CMC-Na and CMC-Li), polyvinyl alcohol (PVA), Guar gum (GG), and gelatin has been introduced. These binders offer alkali resistance and oxidation resistance, ensuring stability during slurry preparation.
OBJECTS OF THE INVENTION:
[041] The principal object of the present invention is to provide a positive electrode material for a sodium-ion battery having better electrochemical performance and the method of producing the same.
[042] Another object of the present invention is to provide a sodium-based positive electrode of high energy density, which is required for producing a sodium-ion battery of specific capacity, high energy density exhibiting excellent cycle characteristics and high-speed charging/discharging performance with low internal resistance.
[043] Yet another object of the present invention is to provide the method of preparing high-capacity positive electrode including the slurry preparation process, and electrode construction.
[044] Still another object of the present invention is to provide provide a system and method for a positive electrode material for a sodium-ion battery, and a producing method and use thereof.
SUMMARY OF THE INVENTION:
[045] The present invention relates to a positive electrode material for a Na-ion battery having better electrochemical performance. In preferred aspects, the present invention provides a positive electrode active material slurry with improved dispersibility and adhesion properties to strongly adhere the electrode active material to a current collector, thereby maintaining excellent electrode properties.
[046] In addition, the present invention provides a preparation method for an electrode material slurry by varying every constituent. The active material ratio varies from 80 to 95%, with the additives varying from 0 to 15%, and the binder ratio is 5 to 20%.
[047] The positive electrode material slurry comprising: a sodium based active material, the binder is chosen cone or group out of the sodium alginate (SA), chitosan, lithium and sodium salts of carboxymethyl cellulose (CMC-Na, and CMC-Li), polyvinyl alcohol (PVA), Guar gum (GG), CMC/styrene-butadiene rubber (SBR) couples, and gelatin further, the conductive additive is selected from acetylene black (AC), super P (SUPERP), and carbon black (C45). The positive electrode includes the slurry preparation process, electrode construction, and performance evaluation of the high-capacity positive electrode.
[048] The positive electrode has low electrode resistance, high electrode strength, high electrolytic solution permeability, high energy density, and good high-speed charging/discharging performance.
[049] The positive electrode material slurry comprising: a sodium based active material, the binder is chosen one or group out of the sodium alginate (SA), chitosan, lithium and sodium salts of carboxymethyl cellulose (CMC-Na, and CMC-Li), polyvinyl alcohol (PVA), Guar gum (GG), CMC/styrene-butadiene rubber (SBR) couples, and gelatin further, the conductive additive is selected from acetylene black (AC), super P (SUPERP), and carbon black (C45) with the active material one from the layered transition metal oxides, phosphates, or silicates, NASICON structure, Prussian blue etc.
[050] Accordingly, the slurry comprises a clustered complex consisting of the binder and conductive additives, which reduces the overall surface area of complex and ensures adhesion properties with the current collector even when using a small amount of binder. The improved wettability of the slurry leads to uniform and better coating on the current collector, and minimizing the surface area of the complex using a solvent maintains adhesion properties with the current collector.
[051] The positive electrode slurry is used to form sodium-ion batteries with high specific capacity, excellent cycle stability, and good rate capability. The sodium-based active material used in the positive electrode slurry is derived from abundant sodium resources, ensuring cost-effectiveness and reduced environmental impact.
[052] The sodium-ion battery produced with the sodium-based positive electrode slurry has potential applications in renewable energy systems, electric vehicles, and smart grid technology.
[053] By utilizing abundant sodium resources and minimizing the use of harmful materials, this invention offers a more sustainable approach to producing high-performance sodium-ion batteries. The resulting positive electrode slurry and preparation method provide not only technical advantages over conventional technology but also contribute to the advancement of sustainable and environmentally friendly technologies.
BREIF DESCRIPTION OF THE INVENTION
[054] It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered for limiting of its scope, for the invention may admit to other equally effective embodiments.
[055] Fig 1. Shows (a) Contact angle measurement diagram, (b) Contact angle values, (c) Surface tension measurement of pendant drop and (d) Surface tension plot with volume and time of cathode slurry with composition AM: CMC-A: CA; 80:10:10.
[056] Fig. 2 shows (a) Contact angle measurement diagram, (b) Contact angle values, (c) Surface tension measurement of pendant drop and (d) Surface tension plot with volume and time of cathode slurry with composition AM: CMC-B:CA; 80:10:10 (37 8A).
[057] Fig. 3 shows (a) Contact angle measurement diagram, (b) Contact angle values, (c) Surface tension measurement of pendant drop and (d) Surface tension plot with volume and time of cathode slurry with composition AM: CMC-C:CA; 80:10:10.
[058] Fig. 4 shows the peel test of the slurries.
[059] Fig. 5 shows the variation of the surface tension, contact angle and peel strength of slurry respective electrode.
[060] Fig. 6 shows Initial Storage Properties of electrode with slurry given in example 1, 2 and 3.
DETAILED DESCRIPTION OF THE INVENTION:
[061] The present invention provides a positive electrode material for Na-ion battery having better electrochemical performance. In preferred aspects, the present invention provides a positive electrode active material slurry with improved dispersibility and adhesion properties to strongly adhere the electrode active material to a current collector, thereby maintaining excellent electrode properties. The positive electrode slurry with improved dispersibility and adhesion properties ensures the strong adhesion of the electrode with the current collector, thereby maintaining excellent electrode properties.
[062] The slurry is a fluid mixture comprising a solid content of active material, binder, and conductive additives in a liquid solvent. The present invention also provides a method for preparing the electrode active material slurry by varying the constituent ratios. The active material ratio ranges from 80% to 95%, while the additive ratio ranges from 0% to 15%, and the binder ratio ranges from 5% to 20%. The positive electrode active material slurry includes a Sodium material selected one out of layered transition metal oxides, phosphates, or silicates, NASICON structure, Prussian blue etc., the binder is chosen one or group out of the sodium alginate (SA), chitosan, lithium and sodium salts of carboxymethyl cellulose (CMC-Na, and CMC-Li), polyvinyl alcohol (PVA), Guar gum (GG), CMC/styrene-butadiene rubber (SBR) couples, and gelatin further and a conductive additive selected from acetylene black (AC), super P (SUPERP), and carbon black (C45). The positive electrode design includes the slurry preparation process, characterization of the slurry, electrode construction, and performance evaluation of the high-capacity positive electrode.
[063] The present invention provides a solution to the challenge of achieving high energy density in sodium-ion batteries by proposing a positive electrode material design. The invention offers a positive electrode slurry with improved wettability characteristics ensuring strong electrode-current collector adhesion and excellent electrode properties.
[064] The positive electrode material slurry comprises a solid content of active material, binder, and conductive additives in a solvent. The active material is a sodium-based material selected from layered transition metal oxides, phosphates, or silicates, NASICON structure.
[065] The binder is chosen one or group out of the sodium alginate (SA), chitosan, lithium and sodium salts of carboxymethyl cellulose (CMC-Na, and CMC-Li), polyvinyl alcohol (PVA), Guar gum (GG), CMC/styrene-butadiene rubber (SBR) couples, and gelatine while the conductive additive is selected from one or combination out of acetylene black (AC), super P (SUPERP), or carbon black (C45).
[066] The method of preparing the electrode slurry involves varying the constituent ratios, with the active material ratio ranging from 80% to 95%, the additive ratio ranging from 0% to 15%, and the binder ratio ranging from 5% to 20%. The resulting positive electrode slurry exhibits improved wettability characteristics, excellent dispersibility, and adhesion properties for the positive electrode of sodium ion battery. The positive electrode design includes slurry preparation, characterization of the slurry, electrode construction, and performance evaluation of the high-capacity positive electrode. The objective of the present invention is to provide a sodium-based positive electrode of high energy density, essential for producing a sodium-ion battery with exceptional cycle characteristics and high-speed charging/discharging performance. The prepared slurry comprising the active material, binder and conductive additives which must satisfy the desired wettability characteristics that are determined with the help of sessile drop test. The resultant mixture is then used to form a positive electrode for a sodium battery by coating it on the current collector and calendaring.
[067] Preparation of slurry:
[068] The method for producing a composition for preparing the positive electrode slurry for the sodium battery involves the composition of active material (AM), binder and conductive additives (CA). The active material can be selected one out layered transition metal oxides, phosphates, or silicates, NASICON structure, Prussian blue etc.. The content of Sodium material in the positive electrode slurry must be in the range of 80 to 90%. The addition of the binder must be in the range of 5 to 20%, and the binder can be from one or group out of the sodium alginate (SA), chitosan, lithium and sodium salts of carboxymethyl cellulose (CMC-Na, and CMC-Li), polyvinyl alcohol (PVA), Guar gum (GG), CMC/styrene-butadiene rubber (SBR) couples, and gelatine. Additionally, the conductive additives must be added in the range of 0 to 15%, and they can be one or a mixture of the following: AC, C45, or SuperP. The particle size or density of each conductive additive is specific to the additive. After adding the conductive additives, the mixture must be stirred for a specific time at a specific RPM. The optimal range of each parameter is crucial to ensure the best performance of the positive electrode material. The specific surface area and tap density of Sodium material electrochemical performance of the sodium ion battery. The content of Sodium material in the positive electrode slurry affects the battery's capacity and cycle life. The addition of the binder is essential to enhance the mechanical strength and adhesion of the positive electrode slurry. The binder's density determines its ability to hold the particles together and its effect on the electrode's conductivity. The binder and conductive additives have crucial role in the formation of the slurry as they govern the rheological properties of the slurry. The contact angle and surface tension to understand the wettability which has been extensively optimized. The contact angle of the slurry is useful to understand the wettability of the slurry. It should be in the range of 40 to 70º. Moreover, the conductive additives are crucial in enhancing the electrode's electrical conductivity and improving the battery's performance. The particle size or density of each conductive additive affects the electrode's packing density, electrical conductivity, and electrochemical performance. Therefore, it is crucial to optimize the content and particle size or density of the conductive additives to achieve the best performance of the positive electrode material.
[069] Preparation of positive electrode:
[070] The slurry formed of the with the content of active material in the range of 70 to 90%. The addition of the binder must be in the range of 2 to 15%, and the binder can be taken one or group out of the sodium alginate (SA), chitosan, lithium and sodium salts of carboxymethyl cellulose (CMC-Na, and CMC-Li), polyvinyl alcohol (PVA), Guar gum (GG), CMC/styrene-butadiene rubber (SBR) couples, and gelatine. Additionally, the conductive additives must be added in the range of 0 to 15%, and they can be one or a mixture of the following: AC, C45, or SuperP.
[071] The preparation of the positive electrode follows the steps as given below-
[072] a. Coating of the slurry:
[073] A positive electrode for a sodium-ion battery can be prepared by applying the positive electrode slurry to a collector foil. This can be done using any known technique, such as doctor blading, bar coating, or a similar method. Various materials can be used as the collector for the sodium-ion battery, including copper foil, aluminium foil, stainless steel foil, nickel foil, titanium foil, alloys of these metals, or a carbon sheet. Aluminium foil is preferred due to its strength, electrochemical stability, and cost-effectiveness. The thickness of the collector foil used in the sodium-ion battery is not limited, but it should not be too thin as this could reduce the strength of the collector foil and cause problems with handling during application of the composition. Conversely, if the thickness is too large, it will increase the ratio by mass (or volume) of the collector foil to the components of the battery, reducing the energy density of the battery. In addition, the positive electrode may harden during battery production, making it difficult to wind. Therefore, the thickness of the collector foil is preferably between 12 to 25µm.
[074] b. Calendaring of electrode:
[075] After the composition is applied to the collector foil, the resulting electrode is dried using any known technique and then subjected to a moulding process, the drying temperature range 80 to 140 ? for the time 12 hr. After the composition is applied to the collector foil for the sodium-ion battery, the resulting electrode is moulded using a known technique such as calendaring to achieve the desired porosity, tortuosity, thickness and density. Porosity and tortuosity are both important factors to consider in the electrode after calendaring for optimal battery performance. After calendaring, the porosity of the electrode material sheet can be reduced, which can decrease the amount of available space for the electrolyte ions to interact with the active material, leading to a decrease in battery performance. However, a certain level of tortuosity can be beneficial in reducing electrode degradation and improving the overall cycling stability of the battery. Therefore, it is important to balance the porosity and tortuosity of the positive electrode after calendaring for optimal battery performance by carefully controlling the calendaring process parameters using the optimal value of the pressure or the thickness between 0.1 to 0.12 mm. There are no particular limitations on the thickness of the electrode material sheet, as it varies depending on the desired shape of the resulting battery. However, the thickness is generally regulated to between 15 to 35µm.
[076] Table 1: Shows the parameters of wettability and electrochemical performance:

[077] The invention will be more fully understood from the following examples. These examples are to be constructed as illustrative of the invention and not limitative thereof:
[078] Example 1
[079] The positive electrode material for Na-ion batteries was prepared using the following method:
[080] Preparation of CMC Solution:
[081] A predetermined quantity of CMC powder was added to a suitable container or beaker. DI Water was added to the CMC powder in the container, considering the desired concentration and consistency of the binder solution.
[082] Addition of Additive: After the CMC powder was fully dissolved, 10 wt% of IPA was introduced into the solution. (Hereafter will be referred as CMC A).
[083] Stirring Process: The entire solution, comprising CMC, additive, and water, was subjected to continuous stirring using a magnetic stirrer for 10 to 14 hours.
[084] Wettability measurement: The contact angle of the CMC A is in the range 57 to 65º with the surface tension 45 to 47 mN/m.
[085] A mixture of active material (Na3V1.63Al0.2Mn0.12Ti0.1(PO4)3), binder CMC A and conducting additive (Super P) was prepared with a mass ratio of 80:10:10, this combination can be named as “37 8A” for convenience. The mixture was homogenized in a planetary ball mill for 20 to 60 minutes at a speed of 300 to 600 RPM to achieve a uniform mixture.
[086] The contact angle and surface tension of the prepared CMC A resulted in the contact angle and surface tension of the AM: CMC A: CA in the range 57 to 60º and 28 to 32mN/m respectively as shown in the Fig.1. Which shows the better wettability of slurry A.
[087] The mixture was coated onto an aluminium foil using a doctor blade with a speed of 0.016m/s and dried in a vacuum oven at 80 to 135°C for 12 hours, resulting in a positive electrode film on the aluminium-based current collector. The thickness of the coated film was ~32±3µm.
[088] To achieve the desired porosity and tortuosity, the coated electrode underwent a calendaring process at a temperature of 80°C, applying a speed of a stress of 1000MPa.
[089] The table presented the performance evaluation of the positive electrode using the 80:10:10 ratio of active material: CMC A: CA for Na-ion batteries in this example.
[090] The peel test was done where the electrode was of the length 80mm with the thickness of 12mm. The peel test was with the 180º angle of opposite force. The average peel force is 1.029N as seen in the Fig.4 that results in the average peel strength of 85N/m.
[091] EXAMPLE 2
[092] A positive electrode material for Na-ion batteries was prepared using the following method:
[093] Preparation of CMC Solution:
[094] A predetermined quantity of CMC powder was added to a suitable container or beaker. Water was added to the CMC powder in the container, considering the desired concentration and consistency of the binder solution.
[095] Addition of Additive: After the CMC powder was fully dissolved, 8 wt% of IPA was introduced into the solution. (Hereafter will be referred as CMC B).
[096] Stirring Process: The entire solution, comprising CMC, additive, and water, was subjected to continuous stirring using a magnetic stirrer for 10 to 14 hours.
[097] Wettability measurement: The contact angle of the CMC B is in the range 64 to 68º with the surface tension 43 to 46mN/m.
[098] A mixture of active material (Na3V1.63Al0.2Mn0.12Ti0.1(PO4)3), binder CMC B and conducting additive (Super P) was prepared with a mass ratio of 80:10:10, this combination can be named as “37 8B” for convenience. The mixture was homogenized in a planetary ball mill for 20 to 60 minutes at a speed of 300 to 600 RPM to achieve a uniform mixture.
[099] The contact angle and surface tension of the prepared CMC B resulted in the contact angle and surface tension of the AM: CMC B: CA in the range 53 to 56? and 32 to 35mN/m respectively as shown Fig. 2. Which shows the better wettability of slurry B.
[100] The mixture was coated onto an aluminium foil using a doctor blade with a speed of 0.016m/s and dried in a vacuum oven at 80 to 134°C for 12 to14 hours, resulting in a positive electrode film on the aluminium-based current collector. The thickness of the coated film was ~32±3µm.
[101] To achieve the desired porosity and tortuosity, the coated electrode underwent a calendaring process at a temperature of 80°C, applying a stress of 1000MPa.
[102] The table presented the performance evaluation of the positive electrode using the 80:10:10 ratio of active material: CMC B: CA for Na-ion batteries in this example. The mechanical properties like peel test also revealed the better adhesive properties.
[103] The peel test was where the electrode was of the length 80mm with the thickness of 12mm. The peel test was with the 180º angle of opposite force. The average peel force is 0.781N as seen in the Fig.4 that results in the average peel strength of 65N/m.
[104] EXAMPLE 3
[105] The positive electrode material for Na-ion batteries was prepared using the following method:
[106] Preparation of CMC Solution:
[107] A predetermined quantity of CMC powder was added to a suitable container or beaker. Water was added to the CMC powder in the container, considering the desired concentration and consistency of the binder solution.
[108] Addition of Additive: After the CMC powder was fully dissolved, 5 wt% of IPA was introduced into the solution. (Hereafter will be referred as CMC C).
[109] Stirring Process: The entire solution, comprising CMC, additive, and water, was subjected to continuous stirring using a magnetic stirrer for 10 to 14 hours.
[110] Wettability measurement: The contact angle of the CMC C is in the range 70 to 73º with the surface tension 67 to 71 mN/m.
[111] A mixture of active material (Na3V1.63Al0.2Mn0.12Ti0.1(PO4)3), binder CMC C and conducting additive (Super P) was prepared with a mass ratio of 80:10:10, this combination can be named as “37 8C” for convenience. The mixture was homogenized in a planetary ball mill for 20 to 60 minutes at a speed of 300 to 600 RPM to achieve a uniform mixture.
[112] The contact angle and surface tension of the prepared CMC C resulted in the contact angle and surface tension of the AM: CMC C: CA in the range 50 to 54º and 35 to 40mN/m respectively as shown Fig.3. Which shows the better wettability of slurry C.
[113] The mixture was coated onto an aluminium foil using a doctor blade with a speed of 0.016m/s and dried in a vacuum oven at 80 to 135°C for 12 to 14 hours, resulting in a positive electrode film on the aluminium-based current collector. The thickness of the coated film was ~32±3µm.
[114] To achieve the desired porosity and tortuosity, the coated electrode underwent a calendaring process at a temperature of 80°C, a stress of 1000 MPa.
[115] The table presented the performance evaluation of the positive electrode using the 80:10:10 ratio of active material: CMC C: CA for Na-ion batteries in this example. The mechanical properties like peel test also revealed the better adhesive properties.
[116] The peel test was done where the electrode was of the length 80mm with the thickness of 12mm. The peel test was with the 180º angle of opposite force. The average peel force is 0.59N as seen in the Fig.4 that results in the average peel strength of 49.16N/m.
[117] Thus, the positive electrode slurry prepared using the binder CMC A, CMC B and CMC C have shown the better wettability that further shows the promising performance as positive electrode. The table 1 shows the properties and electrochemical of the slurry with the electrode prepared using the same.
[118] Thus, key aspect of the method for modifying the adhesivity/wettability of a binder solution to develop positive electrodes for sodium-ion batteries. This addition of special additives improves the performance and stability of the aqueous positive electrode slurry. The optimized ratio of Binder and its additives is selected in the based on the contact angel and surface tension of the binder. The viscosity of binder is also observed to get better adhesivity of positive electrode material on current collector. The binders consisting the specified additives are required to have surface tensions in the range of 35 to 72mN/m and contact angles in the range of 40 to 70 degrees on the surface of an aluminum-based current collector. This precise control of surface properties contributes to the improved adhesivity and coating uniformity of the electrode.
[119] The binder modification with the particular volume ratio with additives helps in getting better range of contact angles (40 to 70 degrees) and reduced surface tensions (ranging from 28 to 70 mN/m) on the surface of the aluminum-based current collector. This emphasizes the importance of optimizing the wetting properties of the slurry on the current collector. A minimum average peel strength of =4N/m is introduced for the electrode, which emphasizes the importance of strong adhesion between the electrode and current collector. This requirement ensures reliable electrode assembly and enhances the overall quality and durability of the sodium-ion battery. Thus, better capacity retention and cyclability, charge discharge efficiency is achieved.
[120] Numerous modifications and adaptations of the system 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 true spirit and scope of this invention.
, Claims:WE CLAIM:
1. A method for modifying the adhesivity/wettability of a binder solution to develop positive electrode for sodium ion battery, comprising:
a. Selecting a binder composition for the positive electrode in a sodium-ion battery, wherein the binder is one out of sodium alginate (SA), chitosan, lithium and sodium salts of carboxymethyl cellulose (CMC-Na, and CMC-Li), polyvinyl alcohol (PVA), Guar gum (GG), CMC/styrene-butadiene rubber (SBR) couples, and gelatine dissolved in DI water.
b. Incorporating specific additives into the binder to enhance its adhesivity.
c. Adjusting the amount of binder and additives to optimize the electrode's electrochemical properties based on active material type, binder type, and processing conditions.
2. The method of claim 1, wherein the specific additives are selected from a group consisting of Ethyl alcohol, iso-propyl alcohol and n-propyl alcohol.
3. The method of claim 1 or 2, wherein the modified binder solution is stirred for the time of 8 to 12 to hours to ensure proper dispersion of the additives and homogeneity of the modified binder solution where in additive to sodium alginate (SA), chitosan, lithium and sodium salts of carboxymethyl cellulose (CMC-Na, and CMC-Li), polyvinyl alcohol (PVA), Guar gum (GG), CMC/styrene-butadiene rubber (SBR) couples, and gelatine weight ratio should be in the range of 0.1% to 20%.
4. The method of claim 1 to 3, where in the developed binders using the additives as according to the claim 2 should have the surface tension in the range 35 to 72mN/m with the contact angle in the range 40 to 70º on the surface of based current collector made up of one or combination aluminum, cooper.
5. A sodium-ion battery positive electrode slurry comprising an improved cathode slurry composition with active material, developed binder (refer claim 4), and conductive additives in the ratio of 70-90:15-2:15-8.
6. The electrode slurry as of claim 5, whereas the active materials is Polyanion compounds include orthophosphates such as Na3-aLiaV2-u-v-w-x-y-zAluMnvTiwMgxNiyFez(PO4)3@C(T)g derived from sol-gel synthesis procedure, where C is the carbon, T is the individual or combination of MWCNTs/rGO/MoS2/MXene and g = wt % vary from 0 to 5 wt.% of rest the composite sample and its synthesis process, here a, u, v, w, x, y and z are mole % wherein a is = 0 and = 10, u is = 10 and = 50, v = 0 and =20, x, y, z = 0 and =15, NaFePO4, Na3V2(PO4)3, NaTi2(PO4)3, NaVOPO4, pyrophosphates such as NaVP2O7, Na2VOP2O7, Na3.12Fe2.44(P2O7)2, Na7V3(P2O7)4, (MoO2)2P2O7, fluorophosphates like Na3(VO1-xPO4)2F1+2x, Na4NiP2O7F2, Na7Fe7(PO4)6F3, Na3Ti2P2O10F, silicates for e.g. Na2MSiO4, sulfates such as Na2+2xM2-x(SO4)3, M2(SO4)3, NaMSO4F, Na2Mn3(SO4)4, Na[Cu2(OH)(H2O)(SO4)2], NaFe(SO4)2, Na3Fe(SO4)2F2, and even mixed polyanion-type compounds Na3M(PO4)(CO3), Na4M3(PO4)2(P2O7), Na7V4(P2O7)4(PO4), NaFe2(PO4)(SO4)2, where M stands for transition metals such as Fe, Co, Ni, and Mn. On the other hand, Prussian blue analogues (PBAs) with common chemical formula similar to perovskite-type three-cubic dimensional network structure i.e. Na2M[M'(CN)6] (M, M'=Fe, Co, Mn, Ni, Cu, Zn etc.), Layered-structured sodium cathodes i.e O-type such as NaxCoO2 and P-type like Na2/3[Fe1/2Mn1/2]O2.
7. The sodium ion battery positive electrode slurry of claim 5-6, wherein the modified slurry exhibits enhanced adhesivity with contact angles on the current collector in the range of 40 to 70º, and reduced surface tensions ranging from 28 to 70mN/m.
8. The sodium ion battery positive electrode slurry of claim 7, whereas peel strength of the electrode the average value of =4N/m.
9. The positive electrode material of claim 1 to 8 exhibits a suitable adhesivity, which could be a prospective cathode material for sodium ion battery in the voltage range of 2.0 V to 4.2 V (±0.3 V).
10. The positive electrode material of claim 1 to 9 whereas delivered high capacity and stability vs Sodium metal (Na/Na+) in the voltage range of 2.0 V - 4.2V (±0.2 V). Thus, the invention could lead to the low cost synthesis of positive electrode fabrication for Sodium ion batteries (SIBs).