Disordered rock salt materials and methods of forming same

Abstract

A composition useful in making a cathode consists of a disordered rock salt and an acid-treated carbon. The composition can be made by milling an acid-treated carbon with a disordered rock salt in water to form a mixture wherein the disordered rock salt has a disordered rock salt average primary particle size of at most 400 nm and the acid-treated carbon has an acid-treated carbon average primary particle size of less than the disordered rock salt primary particle size, the water is removed and the mixture is agglomerated to form secondary particles having a secondary particle average particle size of at least 1 micron to 20 microns. The acid-treated carbon is treated with an inorganic acid, such as concentrated nitric acid.

Description

Technical Field

[0001] This invention belongs to the field of battery technology. Background Technology

[0002] Lithium metal oxides have been used to formulate cathode materials for lithium-ion batteries. Cathodes are derived from several basic crystal structure types, such as spinel, olivine, and layered oxide structures. Layered oxide structures include lithium-excess structures, where additional lithium is present in the structure.

[0003] Recently, attention has focused on disordered rock salt structures, such as those formed from specific lithium metal oxides. One such compound is represented by the following formula: Where M is a divalent or trivalent cation, it has shown promise as a class of transition metal oxides for use as cathodes in lithium-ion batteries. Compounds of formula (1) are considered disordered rock salts, in which random atomic arrangements of lithium and transition metal ions are packed in a close-packed cubic structure. These disordered rock salt compositions offer the ability to contain up to 3 lithium atoms per molecular unit, which is more than conventional excess lithium layered materials. Formula (1) can be converted and represented as Li x M y N z O w .

[0004] Disordered rock salt structures are attractive cathode materials for next-generation lithium-ion batteries because they exhibit higher specific energy density (e.g., higher theoretical energy density) compared to state-of-the-art cathode materials such as layered lithium metal oxide structures. For example, some disordered rock salt structure materials have a theoretical gravimetric energy density of approximately 1120 Wh / kg, while LiMn₂O₄ active materials have a theoretical gravimetric energy density of approximately 492 Wh / kg. 1.5 Ni 0.5 The theoretical gravimetric energy density of O4 is approximately 691 Wh / kg. This energy density is particularly attractive when using lower-cost raw materials as components of the disordered rock salt structure (such as manganese). Therefore, disordered rock salt materials can achieve relatively high energy densities at relatively low material costs. To achieve comparable energy densities, known cathode materials require higher-cost raw materials, such as cobalt or nickel.

[0005] The challenge of disordered rock salt materials lies in their relatively poor electrical conductivity. It has been described that reducing the particle size of disordered rock salt by grinding and then re-aggregating the ground particles can improve conductivity by shortening electron and ion transport paths (US Patent Publication No. 2022 / 0059816). Further improvements may be expected to enhance the electronic conductivity and performance of batteries containing disordered rock salt.

[0006] Accordingly, it is desirable to provide a disordered rock salt that can be ideally processed with carbon powder and into which the resulting disordered rock salt composition is mixed with carbon. Summary of the Invention

[0007] We have discovered that by acid-treating carbon and mixing it with DR powder, it is possible to improve DR compositions consisting of disordered rock salt (DR) and carbon, thereby forming a composition of acid-treated powder and primary DR particles. This composition can then be agglomerated by any suitable method, such as spray drying, to form secondary particles of DR and acid-treated carbon. Acid treatment has been found to lead to improved uniform distribution of carbon and enhanced battery performance compared to batteries using DR mixed with untreated carbon powder.

[0008] An example is a composition consisting of DR particles and acid-treated carbon particles.

[0009] Another example is a method of forming a composition comprising: grinding acid-treated carbon with disordered rock salt in water to form a mixture, wherein the average primary particle size of the disordered rock salt is at most 400 nm, and the average primary particle size of the acid-treated carbon is smaller than that of the disordered rock salt; removing water and agglomerating the mixture to form secondary particles, said secondary particles having an average particle size of at least 1 micrometer to 20 micrometers. The acid-treated carbon is formed by immersing carbon powder in an inorganic acid (a high concentration of inorganic acid dissolved in water, e.g., at least 30% by weight of inorganic acid dissolved in water), typically at high temperatures (e.g., above 30°C to the boiling point of the inorganic acid).

[0010] When a specified component is the majority, it means more than 50 mol% or (as readily understood from the context) to substantially all of the component (99% or less). That is, the majority of the specified component is present in an amount greater than 50% to 99%, 90%, 80%, 70%, or 60% of the component. When a specified component is a minority, it is present in an amount less than 50% to about 1%, with the remainder being the majority of the specified component.

[0011] The composition comprises disordered rock salt and acid-treated carbon. DR typically has a cation consisting of lithium and at least one other metal, and an anion consisting of oxygen and optionally fluorine and one or more of phosphorus, sulfur, and nitrogen. Ideally, oxygen is all or the majority of the anions, with a minority consisting of F and one or more of P, S, and N. Fluorine is the majority of two or more of F, S, P, and N. Illustratively, it is desirable that the F / (P, S, and N) ratio is at least 1 to 100, 50, 25, 10, 5, or 2.

[0012] The composition can be used in primary and secondary lithium-ion batteries. The composition can be used with any suitable electrolyte, separator, and anode (such as those known in the art). Attached Figure Description

[0013] Figure 1 This is a secondary electron micrograph (SEM) of the secondary particles of this invention.

[0014] Figure 2 This is a SEM and energy-dispersive X-ray (EDX) image showing the uniform distribution of carbon in the secondary particles of the present invention.

[0015] Figure 3 This is the X-ray diffraction pattern of the secondary particles exposed to annealing according to the present invention.

[0016] Figure 4 This is a graph showing the weight loss and heat flow during the heating of the secondary particles in this invention.

[0017] Figure 5 This is a SEM image of the secondary particles of this invention.

[0018] Figure 6 This is a SEM and energy-dispersive X-ray (EDX) image showing the uniform distribution of carbon in the secondary particles of the present invention.

[0019] Figure 7 These are the X-ray diffraction patterns of the unannealed and annealed secondary particles of this invention.

[0020] Figure 8 This is a graph showing the weight loss and heat flow during the heating of the secondary particles in this invention.

[0021] Figure 9 This is a SEM image of secondary particles not present in this invention.

[0022] Figure 10 This is a SEM and energy-dispersive X-ray (EDX) spectrum showing the non-uniform distribution of carbon in the secondary particles of this invention. Detailed Implementation

[0023] The following definitions apply to some aspects described with respect to certain embodiments of the invention. These definitions are also open to extension. Each term is further explained and illustrated by description, drawings, and examples. Any interpretation of the terms in this specification should be considered in light of the complete description, figures, and examples provided herein.

[0024] The singular terms “a,” “an,” and “the” include the plural unless the context explicitly specifies otherwise. Thus, for example, a reference to one object can contain multiple objects unless the context explicitly specifies otherwise.

[0025] The rate “C” refers to (depending on the context) a fraction or multiple of the discharge current relative to the “1 C” current value (at which value a battery (in a substantially fully charged state) will be substantially fully discharged within one hour), or a fraction or multiple of the charge current relative to the “1 C” current value (at which value a battery (in a substantially fully discharged state) will be substantially fully charged within one hour).

[0026] In a range where certain battery characteristics vary with temperature, these characteristics are specified at 30 degrees Celsius, unless the context clearly dictates otherwise.

[0027] The ranges presented herein include their endpoints. Thus, for example, the range 1 to 3 includes the values 1 and 3 as well as intermediate values.

[0028] Compositions and morphologies (such as structures) can be used to formulate electrodes of an electrochemical cell unit composed of the composition. More specifically, the composition can be used to form a cathode. A lithium-ion battery includes an electrolyte formulation in which the concentration of the lithium salt is suitable for conducting lithium ions between the cathode and the anode through the electrolyte formulation during discharge and charge operations.

[0029] In a disordered rock salt, both lithium and transition metals occupy a cubic close-packed lattice of octahedral positions. In an electrochemical reaction, lithium diffusion occurs by lithium jumping from one octahedral position via an intermediate tetrahedral position to another octahedral position. The lithium in the intermediate tetrahedral position is the activated state in lithium diffusion. The activated tetrahedral lithium ions share faces with the following four octahedral positions: (i) the position previously occupied by the lithium ion itself; (ii) the vacancy into which the lithium ion will enter; (iii and iv) two positions that can be occupied by lithium, transition metal, or vacancy.

[0030] The composition can be a disordered rock salt (DR) that includes a substance having the following formula: Li x M’ y M z O 2-(a+b) F a Z b where 1.0 < x < 1.75; 0 ≤ y < 0.55; 0.1 < z < 1; 0 ≤ (a + b) < 1.5; (b ≥ 0) M' is one of Ti, Ta, Zr, W, Nb, or Mo; M is one or more of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Zr, Y, Mo, Ru, Rh, Sn, Bi, and Sb; Z is one or more of P, N, and S. Other dopants may also be included, such as dopants that replace Li, such as Na and Mg, which can be present in any useful amount, but typically up to about 10 mol% or 5 mol% to 0.01 mol% of such dopants present in lithium and DR.

[0031] The amounts of F and Z can be the majority or minority of anions (i.e., O, F, and one or more of P, S, and N). Illustratively, (a+b) can be 0.05 to 1.5, 1, 0.95, 0.8, 0.7, or 0.5. A value of 0.05 to 0.25 for a may be desirable. Z can be any combination of P, N, and S, or, if present, just one of them. When two or more are present, the ratio between P, N, and S can be any useful ratio, depending on the property sought. For example, the presence of S may be necessary when a reduction in redox potential is required. It may also be desirable for S to constitute the majority of the P, S, and N present in the composition.

[0032] DR may have any desired Li of 1 or more, but the desired Li, as indicated by x, is at least 1.1, 1.15, 1.2 to 1.65, 1.5 or 1.4.

[0033] The cation of DR can be the described metal, but ideally, at least one metal, such as that represented by M, is composed of one or more of Ti, Mn, Fe, Co, V, Cr, Ni, and Cu. It may be desirable for M to be composed of Ti and Mn. The composition may be illustratively a composition in which M' is composed of Nb. When Nb is present, it may be desirable for M to be composed of Mn. Illustratively, M' can be Nb and M can be Mn. When Nb and Mn are present or not present with other metals, they may be present in an Mn / Nb ratio of 1 or 2 to 200, 150, 100, 75, 50, 25, or 10 on a molar basis.

[0034] DR can be manufactured by any suitable method, such as methods known in the art for manufacturing disordered rock salt. Exemplary methods are described in U.S. Patents 10,280,092 and 10,978,706 and ACS Appl Mater Interfaces. October 2, 2019; 11(39):35777-35787, each of which is incorporated herein by reference.

[0035] By way of example, the composition ideally consists of clusters of micrometer-sized particles or aggregates of submicrometer-sized particles. Micrometer-sized clusters are also referred to herein as secondary particles. Secondary particles preferably have a micrometer-scale average particle size (e.g., diameter), such as between 1 micrometer and 20 micrometers. The secondary particles consist of DR primary particles and acid-treated carbon particles. The terms “primary” and “secondary” indicate that the primary particles form prior to the secondary particles, which are aggregates of the primary particles. The DR primary particles have a nanometer-scale average particle size (e.g., equivalent spherical diameter), such as less than 400 or 300 nanometers. The acid-treated carbon particles (primary particles) are similar in size, but ideally, their primary size is smaller than the DR primary particle size. Submicrometer primary particles of disordered rock salt material provide the desired conductivity, while micrometer-sized secondary particles of disordered rock salt material produce high electrode energy density.

[0036] By way of example, acid-treated carbon can be produced by immersing carbon powder in an inorganic acid for a period of time to adequately acidify the carbon black, thereby improving, for example, the uniform distribution and coating of the DR primary particles during agglomeration of DR primary particles and carbon particles. Typically, the inorganic acid is present in water in an amount of at least 10%, 20%, 30%, 50%, 60%, or any practically feasible amount, such as commonly referred to fuming inorganic acids. The inorganic acid can be any suitable inorganic acid, such as those known in the art (e.g., phosphoric acid, nitric acid, HCl, sulfuric acid), with nitric acid being particularly useful (e.g., concentrated nitric acid of about 70% by weight).

[0037] Immersion of the carbon can last for any suitable soaking time to achieve acid treatment, typically from at least 5, 15, or 30 minutes to 24, 12, or 6 hours, and can be carried out with agitation. The immersion can also ideally be carried out at high temperatures (e.g., above about 30°C to the boiling point of the inorganic acid in water). After immersion in the inorganic acid, the carbon is typically washed with neutral water (pH about 7) until the wash water is at a neutral pH. The acid-treated carbon can be stored in an atmosphere that maintains acidification and does not adsorb unwanted adsorbates (e.g., inert gases, dry air, nitrogen, or combinations thereof).

[0038] The carbon used to manufacture acid-treated carbon particles can be any useful carbon powder that can be used to manufacture batteries, and can include, for example, carbon black, carbon nanotubes, graphene, graphite, carbon fibers, and acetylene black. In illustrative terms, the carbon particles are carbon black powder, which can be standard, conductive, or non-conductive. The carbon can consist of primary particles that are chemically bonded to form secondary particles (e.g., carbon black) and are referred to as structured inorganic powders, or the primary particles may have no other chemical bonds besides hydrogen bonds or van der Waals forces (e.g., carbon nanotubes). Particle size can be determined as described above. Carbon black can have any useful oil absorption value (ASTM D-2414-09). For example, the oil absorption value (OAN) of carbon black should generally be from about 40, 50, or 60 to 250, 200, or 175 ml per 100 grams. Specific surface area (ISO 9277:2010) can be any useful one and is generally at least 10 m². 2 / g、20 m 2 / g or 50 m 2 / g to any actual surface area, 1000 m² 2 / g、500 m 2 / g、300 m 2 / g or 200 m 2 / g.

[0039] The carbon black may be standard carbon black that has not undergone any special treatment to make it non-conductive. Standard carbon black is carbon black that has not undergone any special surface treatment or oxidation. Alternatively, one or more conductive carbon blacks may be used alone or in combination with standard carbon black. Conductive carbon black is generally considered to have a carbon purity of at least 97%, but preferably a purity of 99% or higher, 100 or higher OAN, and 120 μm. 2 / g or higher specific surface area. Examples of standard carbon blacks include RAVEN 790, RAVEN 450, RAVEN 500, RAVEN 430, RAVEN 420 and RAVEN 410 carbon blacks purchased from Colombia, as well as carbon blacks purchased from Cabot Corporation under the trademarks VULCAN, PROPEL, REGAL, STERLING and SPHERON.

[0040] By way of example, the secondary particles of DR and acid-treated carbon can be carbon black, carbon nanotubes, graphene, graphite, carbon fibers, and acetylene black, wherein the acid-treated carbon particles are milled to make their primary average particle size the same as or smaller than that of the primary average particle size of DR. The DR powder and acid-treated carbon particles are milled by any suitable method. By way of example, they are milled in deionized water in their respective desired amounts (e.g., from 1%, 2%, 3%, 4%, or 5% to 35%, 30%, 25%, or 20% by volume or weight of carbon in the composition “Carbon and DR”) to create a suspension. Milling can be performed via a micromedia mill. A micromedia mill can include concentric cylinders, wherein abrasive media are present in an annular gap between the cylinders. The abrasive media break down the precursors in the suspension as the cylinders rotate relative to each other, thereby producing small primary particles of nanoscale size. The micromedia mill can also be designed to form particles of uniform size such that the size of all primary precursor particles is substantially the same within a specified range. The average particle size of the primary particles discharged from the mill may not exceed 400 nanometers (nm). The average primary particle size of each of the DR and acid-treated carbons must not exceed 200 nm, 100 nm, or be smaller than any practically feasible size, such as greater than about 25 nm. Ideally, the average size of the primary acid-treated carbon is smaller than the average size of the DR primary particles. An example of a suitable micromedia mill is a laboratory bead mill, such as the Buhler PML2 product, a trademark of the Buhler Group. The particle size can be determined by any suitable method, such as those known in the art, including laser diffraction and photomicrography.

[0041] After grinding, moisture is removed to agglomerate the DR and acid-treated carbon particles together, thus forming a composition. Secondary particles can be formed by any useful method, and exemplarily by spray drying. Ideally, the average size of the secondary particles is from about 1 or 2 micrometers to 20, 15, or 10 micrometers. For example, spray drying can be performed using a small spray dryer, such as the Buchi B-290 model, a trademark of Buchi.

[0042] The composition can be used to form a cathode by any suitable method, such as those known in the art. For example, secondary particles of DR and acid-treated carbon particles can be mixed with a binder, such as a polymer that can be used to manufacture a cathode (e.g., polyfluoropolymers such as polyvinylidene fluoride) and one or more solvents to form a slurry. Non-limiting examples of one or more solvents can be aprotic polar solvents, such as methyl-2-pyrrolidone (NMP). The slurry can then be deposited on a metal current collector (e.g., stainless steel, copper, or any suitable conductive metal sheet), and the solvent can be removed to form a cathode.

[0043] In one embodiment, the composition of DR particles and acid-treated particles can be further annealed to a certain temperature in an inert atmosphere (e.g., inert gas) or air, which can improve the performance of the battery thus produced. Inventively, the temperature can be from about 150°C or 200°C to 450°C, 400°C, or 350°C. The further annealing time can be from 5, 10, or 15 minutes to 24, 18, 12, or 6 hours.

[0044] The cathode of the composition can be used in a rechargeable lithium-ion battery cell. The battery cell includes a cathode, anode, separator, and electrolyte. The battery or battery cell can be formed in any suitable atmosphere, such as those common in the art. For example, a high-purity argon atmosphere can be used to limit any undesirable contamination from substances present in the atmosphere.

[0045] Example Example 1. A composition comprising a mixture of disordered rock salt particles and acid-treated carbon particles.

[0046] Example 2. The composition as described in Example 1, wherein the mixture comprises agglomerated disordered rock salt particles and secondary particles of acid-treated carbon particles.

[0047] Example 3. The composition as described in Example 1 or 2, wherein the average particle size of the disordered rock salt particles is at most 400 nm.

[0048] Example 4. The composition as described in any one of Examples 1 to 3, wherein the average particle size of the acid-treated carbon particles is at most 400 nm.

[0049] Example 5. The composition as described in any one of Examples 1 to 4, wherein the size of the acid-treated carbon particles is smaller than the size of the disordered rock salt particles.

[0050] Example 6. The composition as described in any one of Examples 1 to 5, wherein the acid-treated carbon particles consist of acid-treated carbon black, carbon nanotubes, graphene, graphite, carbon fibers, and acetylene black.

[0051] Example 7. The composition of any one of claims 1 to 6, wherein the acid-treated carbon particles are composed of acid-treated conductive carbon black, the conductive carbon black having a surface area of ​​at least 30 m². 2 / g and the oil absorption is at most about 10 ml / g.

[0052] Example 8. The composition of claim 7, wherein the surface area of ​​the conductive carbon black is at least 50 m². 2 / g and the oil absorption value is up to 500 ml / g.

[0053] Example 9. The composition as described in any one of Examples 1 to 8, wherein the acid-treated carbon particles are present in an amount of 1% to 35% by volume of the composition.

[0054] Example 10. The composition as described in any of the foregoing examples, wherein the disordered rock salt is represented by the following: Li x M' y M z O 2-(a+b) F a Z b Among them, 1.0 <x<1.75;0≤y<0.55;0.1<z<1;0≤(a+b)<0.7;(b> 0) M' is one of Ti, Ta, Zr, W, Nb or Mo; M is one or more of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Zr, Y, Mo, Ru, Rh and Sb; and Z is one or more of P, N and S.

[0055] Example 11. The composition as described in Example 10, wherein M is composed of one or more of Ti, Mn, Fe, Co, V, Cr, Ni and Cu.

[0056] Example 12. A battery electrode comprising the composition described in any one of Examples 1 to 10.

[0057] Example 13. A method of forming a composition, comprising: (i) Acid-treated carbon and disordered rock salt are ground in water to form a mixture, wherein the disordered rock salt has an average primary particle size of up to 400 nm, and the acid-treated carbon has an average primary particle size smaller than that of the disordered rock salt. (ii) Remove the water and agglomerate the mixture to form secondary particles, the secondary particles having an average particle size of at least 1 micrometer to 20 micrometers.

[0058] Example 14. The method of Example 13, wherein the acid-treated carbon is formed by an acid treatment method comprising immersing carbon powder in an inorganic acid at a high temperature.

[0059] Example 15. The method as described in Example 14, wherein the high temperature is at least 30°C higher than the boiling point of the inorganic acid.

[0060] Example 16. The method as described in Example 14 or 15, wherein the concentration of the inorganic acid in water is at least 30% by weight.

[0061] Example 17. The method as described in Example 16, wherein the concentration of the inorganic acid is at least 50% by weight.

[0062] Example 18. The method of any one of claims 14 to 17, wherein the inorganic acid is concentrated nitric acid.

[0063] Example 19. The method of any one of claims 13 to 18, wherein the removal and the agglomeration are carried out by spray drying.

[0064] Example 20. The method of any one of Examples 14 to 19, wherein the acid treatment method comprises separating the acid-treated carbon from the inorganic acid and washing with neutral water until a neutral pH is reached.

[0065] Example 21. The method of any one of Examples 14 to 20, wherein the toner comprises one or more of carbon black, carbon nanotubes, graphene, graphite, carbon fiber and acetylene black.

[0066] Example 22. The method as described in Example 21, wherein the carbon powder is composed of carbon black, and the carbon black is conductive carbon black.

[0067] Example 23. The method as described in Example 22, wherein the surface area of ​​the conductive carbon black is at least 30 m². 2 / g and the oil absorption value is up to 200 ml / 100 g.

[0068] Example 24. The method as described in any one of Examples 13 to 23, wherein after the water is removed and the particles are agglomerated, the secondary particles are annealed at a temperature of 150°C to 350°C.

[0069] Example 25. The method as described in Example 24, wherein the annealing is carried out in an inert atmosphere for a period of 1 to 24 hours.

[0070] Example The disordered rock salt was synthesized via a conventional solid-state reaction, such as the reaction described in U.S. Patent Publication No. 2022 / 0059816. Typically, stoichiometric amounts of precursors (Mn₂O₃, TiO₂, Nb₂O₅, Li₂CO₃, and LiF) are mixed in deionized water to prepare a suspension (35 wt% solids), which is then ball-milled using a planetary ball mill to reduce the particle size (<300 nm) and obtain a homogeneous mixture of all precursors. The mixture is dried in air at 100°C for 12 h, and then annealed at 700°C for 12 h and 900°C for 20 min under an argon or nitrogen flow (20 L / h) to obtain the disordered rock salt used in each of the examples and comparative examples herein.

[0071] Example A: Acid-treated Super C65 carbon black purchased from MSE Supplies The preparation of hydrophilic carbon was carried out by connecting a Liebig condenser to the center connector of a 500 mL round-bottom flask with flowing cold water to prevent solvent evaporation. The top of the condenser was sealed with a sealing film to prevent NO2 escape. 5 g of carbon (Super C65, MSE Supplies) was added to a 500 mL three-necked round-bottom flask equipped with an oval stir bar, followed by 300 mL of concentrated HNO3 (70% nitric acid ACS reagent, Sigma Aldrich). The flask was placed in a silicone oil bath at 60 °C and then slowly heated to 90 °C, ensuring the solution did not boil. The solution was then stirred at 90 °C for 16 hours. Stirring was then stopped, allowing the carbon black to precipitate to the bottom of the flask. The supernatant acid was then decanted by pouring or pipetting. The remaining carbon black suspension was added to a 1 L beaker containing approximately 600 mL of DI water and stirred. The flask was rinsed three times with DI water and added to the 1 L beaker. The carbon black was allowed to precipitate, and the water was decanted. Repeat this step until the decanted water reaches a neutral pH. Centrifuge the remaining solution and remove the supernatant. Place the centrifuge tubes containing the treated carbon in a vacuum oven at 80°C and dry for 24 hours. Store the final acid-treated carbon in an argon-filled glove box.

[0072] Appropriate amounts of DR and acid-treated carbon (2-10% by weight) were wet-milled in water at a solid content of 10% using various milling energies (250, 500 kWh / T) and a bead size of 0.3 mm. The resulting slurry was spray-dried (slurry flow rate 3 ml / min, temperature 80-90 °C, gas flow rate 740 L / h) to obtain carbon-coated DR particles with a primary particle size of 50-300 nm and a secondary particle size of 1-5 μm. The resulting powder was post-annealed under argon at different temperatures such as 150 °C, 250 °C, and 350 °C for 12 hours, and electrochemical tests were performed.

[0073] Example B: Acid-treated carbon nanotubes The acid treatment method for commercially available carbon nanotubes is the same as that for Super C65 carbon black.

[0074] Comparative Example B: Secondary particles and batteries can be manufactured using the same carbon nanotubes without acid treatment, in the same manner as in the embodiments described above.

[0075] The battery cells were assembled in a glove box filled with high-purity argon (M-Braun, O2 and humidity content <0.1ppm). The cathode was prepared by mixing carbon-coated disordered rock salt powder with poly(vinylidene fluoride) (Sigma Aldrich) and 1-methyl-2-pyrrolidone (Sigma Aldrich), depositing the resulting slurry onto a stainless steel current collector, and drying it to form a composite cathode film. For the anode, thin lithium foil was cut to the desired size. Each battery cell comprised a composite cathode film, a polypropylene separator, and a lithium foil anode. An electrolyte (1.0M LiPF6 in EC / EMC (1:2 v / v)) containing lithium hexafluorophosphate was used. The battery cells were sealed and cycled at 30°C at a C / 20 formation rate and a C / 3 cycling rate between 1.5–4.6V, where 1C = 300 mAh / g. For full cell testing, graphite anodes were used, and the cells were cycled at 30°C at a C / 20 formation rate and a C / 3 cycle rate between 2-4.45 or 2-4.55V.

[0076] The spray-dried Super C65 spherical particles containing secondary particles have an average diameter of approximately 2 micrometers and are composed of primary nanoparticles ranging from 100 to 300 nm, such as... Figure 1 As shown in the scanning electron microscope (SEM). From Figure 2 The energy-dispersive X-ray (EDX) elemental mapping shown reveals a uniform distribution of C65 carbon within the DR secondary particles (red dots).

[0077] The carbon-coated DR was post-annealed under argon at different temperatures such as 150, 250, and 350 °C for 12 hours to remove residual impurities and adsorbed water. The phase purity of the synthesized samples was analyzed by X-ray diffraction (XRD). All three samples annealed at different temperatures showed corresponding phase purity. Fm3m Diffraction peaks of the disordered rock salt structure of the space group. In the XRD pattern of the sample annealed at 150℃, 2Θ = 30-35. o There was a small peak nearby, which became undetectable as the annealing temperature increased. Increasing the annealing temperature also caused the XRD peaks to become significantly sharper, indicating improved crystallinity. Figure 3 As shown.

[0078] Thermogravimetric analysis (TGA) was performed on the secondary particles to detect weight changes with temperature. Two weight losses were observed on the TGA curve. The first weight loss (approximately 6 wt%) likely corresponds to the release of adsorbed water and the decomposition of the impurity phase, while the second weight loss (approximately 7 wt%) corresponds to carbon oxidation and exothermic generation, such as... Figure 4 As shown.

[0079] Electrochemical performance was tested within a voltage window of 1.5–4.6 V. The initial capacity (C / 20), CE, and total resistance of Super 65 samples containing secondary particles annealed at different temperatures are shown below. The optimal post-annealing temperature was 250 °C, at which the initial capacity and CE were highest.

[0080] Table 1

[0081] Acid-functionalized multi-walled CNTs were used to produce DR containing 4 wt% carbon secondary particles. A lower milling energy (250 kWh / T) was used compared to previous experiments. Figure 5 Secondary particles are shown. Figure 6 A uniform distribution of carbon was observed. CNTs were also observed across secondary granular particles treated with DR acid. The prepared sample exhibited sharp XRD diffraction peaks, indicating good crystallinity. No observable changes were observed in the diffraction pattern after annealing at 250°C. Figure 7 As shown, two weight losses were observed in the TGA curve. The first weight loss (approximately 6 wt%) likely corresponds to the release of adsorbed water and the decomposition of the impurity phase, while the second weight loss (approximately 4 wt%) likely corresponds to carbon oxidation and exothermic generation, such as... Figure 8 As shown in Table 2, the electrochemical performance was tested within a voltage window of 2–4.5 V. The samples post-annealed at 250 °C showed improved Cy1 discharge capacity compared to the synthesized samples.

[0082] DR containing approximately 7% carbon secondary particles was produced using untreated multi-walled CNTs. Figure 9 The secondary particles after annealing at 400°C for 6 hours are shown. As can be seen from this figure, the particles are unlike those in Example B (…). Figure 5 and Figure 6 It is so uniformly spherical. Figure 10 The example shown is the same as that of embodiment B. Figure 6 Compared to the inhomogeneity of carbon, Table 2 shows the battery performance of the battery with a cathode and the battery manufactured in the same manner as in Example B, where it is obvious that the performance is lower than that of Example B, and the performance of Example B is lower than that of Example A. These comparative Examples B show impurity phases not seen in Example B in their X-ray diffraction patterns (not shown).

[0083] Table 2

Claims

1. A composition comprising a mixture of disordered rock salt particles and acid-treated carbon particles.

2. The composition of claim 1, wherein the mixture comprises agglomerated disordered rock salt particles and secondary particles of acid-treated carbon particles.

3. The composition of claim 2, wherein the average particle size of the disordered rock salt particles is at most 400 nm.

4. The composition of claim 2, wherein the average particle size of the acid-treated carbon particles is at most 400 nm.

5. The composition of claim 4, wherein the size of the acid-treated carbon particles is smaller than the size of the disordered rock salt particles.

6. The composition of claim 5, wherein the acid-treated carbon particles are composed of acid-treated carbon black, carbon nanotubes, graphene, graphite, carbon fibers, and acetylene black.

7. The composition of claim 6, wherein the acid-treated carbon particles are composed of acid-treated conductive carbon black, the conductive carbon black having a surface area of ​​at least 30 m². 2 / g and the oil absorption is at most about 10 ml / g.

8. The composition of claim 7, wherein the surface area of ​​the conductive carbon black is at least 50 μm. 2 / g and the oil absorption value is up to 500 ml / g.

9. The composition of claim 1, wherein the acid-treated carbon particles are present in an amount of 1% to 35% by volume of the composition.

10. The composition according to any one of the preceding claims, wherein the disordered rock salt is represented by the following: Li x M' y M z O 2-(a+b) F a Z b Among them, 1.0 <x<1.75;0≤y<0.55;0.1<z<1;0≤(a+b)<0.7;(b> 0) M' is one of Ti, Ta, Zr, W, Nb or Mo; M is one or more of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Zr, Y, Mo, Ru, Rh and Sb; and Z is one or more of P, N and S.

11. The composition of claim 10, wherein M is composed of one or more of Ti, Mn, Fe, Co, V, Cr, Ni and Cu.

12. A battery electrode comprising the composition of claim 10.

13. A method of forming a composition, comprising: (i) Acid-treated carbon and disordered rock salt are ground in water to form a mixture, wherein the disordered rock salt has an average primary particle size of up to 400 nm, and the acid-treated carbon has an average primary particle size smaller than that of the disordered rock salt. (ii) Remove the water and agglomerate the mixture to form secondary particles, the secondary particles having an average particle size of at least 1 micrometer to 20 micrometers.

14. The method of claim 13, wherein the acid-treated carbon is formed by an acid treatment method comprising immersing carbon powder in an inorganic acid at a high temperature.

15. The method of claim 14, wherein the high temperature is at least 30°C higher than the boiling point of the inorganic acid.

16. The method of claim 15, wherein the concentration of the inorganic acid in water is at least 30% by weight.

17. The method of claim 16, wherein the concentration of the inorganic acid is at least 50% by weight.

18. The method of claim 13, wherein the inorganic acid is concentrated nitric acid.

19. The method of claim 13, wherein the removal and the agglomeration are performed by spray drying.

20. The method of claim 14, wherein the acid treatment method comprises separating the acid-treated carbon from the inorganic acid and washing with neutral water until a neutral pH is achieved.

21. The method of claim 14, wherein the toner is composed of one or more of carbon black, carbon nanotubes, graphene, graphite, carbon fiber, and acetylene black.

22. The method of claim 21, wherein the carbon powder is composed of carbon black, and the carbon black is conductive carbon black.

23. The method of claim 22, wherein the surface area of ​​the conductive carbon black is at least 30 m². 2 / g and the oil absorption value is up to 200 ml / 100 g.

24. The method of any one of claims 13 to 23, wherein after the water is removed and the particles are agglomerated, the secondary particles are annealed at a temperature of 150°C to 350°C.

25. The method of claim 24, wherein the annealing is carried out in an inert atmosphere for a period of 1 to 24 hours.

Images