Fluorinated positive electrode material and preparation method and application thereof

Abstract

The invention belongs to the technical field of batteries, and relates to a fluorinated positive electrode material and a preparation method and application thereof. According to the preparation method, a substance which can be decomposed by heating to generate fluorine-containing gas is taken as a fluorine source, the fluorine source on the surface of the positive electrode material is subjected to thermal decomposition to generate the fluorine-containing gas, the fluorine-containing gas and oxide in the positive electrode material are subjected to gas-solid interface passivation reaction, uniform fluorination on the surface of the positive electrode material is realized, and the fluorinated positive electrode material is obtained. The fluorinated positive electrode material prepared by adopting a double-temperature-zone tubular furnace effectively solves the problem of interface incompatibility of an oxide positive electrode in a liquid-state battery and a solid-state battery, and realizes double improvement of battery capacity and stability; meanwhile, a tail gas absorption link is arranged, potential hazards of gas products to human bodies and the environment are eliminated, and the green production concept is met.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, and relates to a fluorinated cathode material, its preparation method, and its application. Background Technology

[0002] Oxide cathode materials, with their advantages of high operating voltage, high theoretical capacity, and ease of large-scale preparation, have always been a core candidate cathode material for high-energy-density rechargeable batteries. However, regardless of whether the rechargeable battery is organic-liquid or inorganic-solid system, oxide cathodes and electrolytes face significant interfacial challenges: on the one hand, residual alkali on their surface easily triggers interfacial side reactions and high interfacial impedance, accelerating battery capacity loss and increasing the risk of thermal runaway; on the other hand, during charge-discharge processes, especially during high-voltage cycling, phenomena such as transition metal dissolution, lattice oxygen release, and interfacial reactions with the electrolyte further exacerbate electrolyte decomposition and cathode structure degradation, leading to rapid battery performance decline. These interfacial problems severely restrict the development and large-scale application of high-energy-density rechargeable batteries. Therefore, improving the interfacial stability between oxide cathode materials and electrolytes is an urgent need for developing practical, long-life, high-energy-density rechargeable batteries.

[0003] Patent CN117913237A discloses a fluorine-coated cathode material, its preparation method, and its application. The method involves mechanically mixing a fluoride with a conductive polymer to obtain a fluorine-containing conductive polymer, then mechanically mixing this polymer with a high-nickel cathode material and heat-treating it to obtain a fluorine-coated high-nickel cathode material. This strategy can effectively improve the air stability of the high-nickel cathode, suppress transition metal dissolution, and thus improve its electrochemical performance and cycle life in liquid batteries. However, the mechanical mixing method used in this patent is difficult to guarantee uniform dispersion and sufficient contact of the materials. This not only fails to produce a pure fluorine-containing conductive polymer but may also lead to uneven fluorine coating on the cathode material surface, affecting the modification effect. The preparation process involves multiple steps, including cathode washing, two-step mechanical mixing, and calcination, making the process complex and unsuitable for large-scale industrial application. Furthermore, the fluorine-containing conductive polymer coated by this method only has electronic conductivity but poor ionic conductivity. Therefore, the fluorine coating prepared by this method is not conducive to ion transport between the cathode material and the solid electrolyte, resulting in high interfacial resistance and low capacity in the solid-state battery.

[0004] Patent CN117219744A discloses a fluorine-coated cathode material and its preparation method. This method utilizes a porous additive to ball-mill and mix fluoride and cathode material, followed by sintering to achieve a fluorine coating with controllable surface thickness. This design reduces the negative impact of surface coating on cathode capacity and impedance, and also inhibits electrolyte corrosion of the cathode, thereby extending battery cycle life. However, this method has significant drawbacks: First, the initial sintering temperature is as high as 840℃ or more, which can easily lead to structural mixing of the cathode material; second, the preparation involves ball milling, sieving, and secondary sintering, making the process complex and unsuitable for large-scale, efficient production; third, the ball milling process makes it difficult to ensure the uniformity of the fluorine coating on the cathode particle surface, potentially affecting the modification effect; furthermore, the feasibility of this fluorine coating strategy in solving the cathode / electrolyte interface problem in solid-state batteries requires further verification.

[0005] Patent CN119230815A discloses a modified lithium-rich manganese-based cathode material, its preparation method, and its application. The method involves impregnating the lithium-rich manganese-based cathode material with an aqueous solution of a fluorocarbon surfactant, followed by high-temperature sintering to obtain a fluorine-doped lithium-rich manganese-based cathode material. This enhances the surface stability of the cathode and improves the rate performance and cycle stability of the material. However, this method has significant limitations: firstly, large-scale production would generate a large amount of wastewater, which is inconsistent with the concept of green production; secondly, aqueous solution treatment easily leads to lithium loss, and immersion in the solution can damage the structure and performance of other air-sensitive cathode materials, requiring subsequent lithium replenishment heat treatment, which increases lithium usage and cost and limits its versatility; thirdly, the high-temperature sintering temperature reaches as high as 900℃, which may also damage the bulk structure of the cathode material; and fourthly, whether this modification method can solve the interface problem of lithium-rich manganese-based cathode materials in solid-state batteries still needs further verification.

[0006] Patent CN119965270A discloses a cathode material, its preparation method, and its application. The method involves mixing the cathode material with an organic solution containing fluorine and boron sources, followed by distillation and heat treatment to obtain a cathode material with a fluorine-boron double coating. This significantly improves the interfacial compatibility between the cathode and the sulfide solid electrolyte, allowing the high specific energy advantage of the high-voltage cathode material to be effectively released in room-temperature sulfide-based solid-state batteries. However, this preparation method involves complex processes such as organic solution mixing, solvent distillation and recovery, and post-heat treatment, resulting in high material costs and cumbersome procedures. Furthermore, the fluorine and boron-containing lithium / sodium salts on the cathode material surface are highly hygroscopic, significantly increasing the requirements for controlling the material storage environment. The aforementioned lithium / sodium salts are readily soluble in the electrolyte in liquid batteries, limiting the applicability of this modification strategy to solid-state batteries and severely restricting its application scenarios.

[0007] It is evident that existing patents related to surface coating of cathode materials suffer from the following significant shortcomings: limited applicability, complex preparation processes, difficulty in controlling the uniformity of the coating, environmentally unfriendly preparation methods, high costs for large-scale production, and excessively high heat treatment temperatures in some methods. These shortcomings severely limit the large-scale application of cathode materials in high-energy-density secondary batteries. Therefore, developing a cathode material modification method that can significantly enhance cathode / interface stability, conforms to green production principles, and has a simple and universally applicable preparation process is of great significance for accelerating the development of next-generation high-energy-density secondary batteries. Summary of the Invention

[0008] In view of the shortcomings of existing technical solutions, the present invention aims to provide a fluorinated cathode material, its preparation method and application.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a fluorinated cathode material involves using a substance that can decompose upon heating to produce fluorine-containing gas as a fluorine source. The fluorine source on the surface of the cathode material undergoes thermal decomposition to produce fluorine-containing gas, which then reacts with oxides in the cathode material to passivate the gas-solid interface, thereby achieving uniform fluorination on the surface of the cathode material and obtaining the fluorinated cathode material.

[0010] The fluorinated cathode material obtained by the above method consists of an oxide cathode core, a fluorine-doped oxide cathode shell, and a dense amorphous lithium fluoride (or sodium fluoride, potassium fluoride) surface coating; the fluorinated cathode material also has high structural stability, high cathode / electrolyte interface ionic conductivity, excellent air stability and thermal stability.

[0011] Furthermore, in a dual-temperature zone tubular furnace, the fluorine source decomposes upon heating to produce fluorine-containing gas. This fluorine-containing gas diffuses along with the carrier gas to the surface of the cathode material and undergoes a gas-solid interface reaction with the cathode material, thereby achieving uniform fluorination on the surface of the cathode material.

[0012] Furthermore, the fluorine source and the oxide cathode material are placed in temperature zones one and two of a dual-temperature zone tube furnace, respectively. Then, an inert carrier gas is continuously introduced from one end of temperature zone one of the dual-temperature zone tube furnace at a flow rate of 10–200 mL / min. The heating power supplies of temperature zones one and two are started in sequence, so that the fluorine source decomposes upon heating to produce fluorine-containing gas. The fluorine-containing gas diffuses with the carrier gas to the surface of the cathode material in temperature zone two, where it undergoes a gas-solid interface passivation reaction with the oxide in the cathode material, thereby achieving uniform fluorination of the cathode material surface and obtaining a fluorinated cathode material.

[0013] The mass ratio of the fluorine source to the positive electrode material is 1-50:100; wherein the fluorine source is a substance that can decompose to produce fluorine-containing gas when heated.

[0014] The substance that can decompose upon heating to produce fluorine-containing gas is one or more of the following: ammonium hexafluorophosphate, sodium hexafluorophosphate, lithium hexafluorophosphate, potassium hexafluorophosphate, cesium hexafluorophosphate, ammonium tetrafluoroborate, sodium tetrafluoroborate, lithium tetrafluoroborate, diazo tetrafluoroborate, and potassium tetrafluoroborate.

[0015] The heating temperature of the first temperature zone is the thermal decomposition temperature of the fluorine source, and the heating rate is 1–10 °C / min. The heating temperature of the second temperature zone is 50–300℃, and the heating rate is 1–10℃ / min; The constant temperature heating time for temperature zone one and temperature zone two is 1–20 hours.

[0016] The positive electrode material is Li oxide. x M y O2 (0<x<2, 0<y≤1), Na x M y O2 (0 < x <2, 0<y≤1) or K x M y O2 (0 < x <2, 0<y≤1); where M is a metal or metalloid element other than Group 1 in the periodic table.

[0017] Furthermore, cathode materials include, but are not limited to, LiCoO2, LiMnO2, LiNiO2, LiMn2O4, Li2MnO3, and LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2, LiNi 0.8 Mn 0.1 Co 0.1 O2, LiNi 0.9 Mn 0.05 Co 0.05 O2, LiMn 1.5 Ni 0.5 O4, Li 1.2 Mn 0.6 Ni 0.2 O2, Li 1.15 Ni 0.377 Mn 0.473 O2, Li 1.2 Mn 0.4 Ti 0.4 O2, Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2, Na2Mn3O7, NaLi 0.1 Ni 0.35 Mn 0.3 Ti 0.25 O2, NaNi1 / 3 Fe 1 / 3 Mn 1 / 3 O2, NaNi 0.5 Mn 0.5 O2, Na 0.75 [Li 0.25 Mn 0.75 O2, Na 0.7 Ni 0.2 Co 0.2 Mn 0.6 O2, Na 0.67 Mn 0.67 Ni 0.33 O2, Na 0.6 [Li 0.2 Mn 0.8 O2, K 0.45 MnO2, K 0.5 MnO2, K 0.59 Mn 0.67 Ni 0.33 O2, K 0.6 CoO2, K 0.7 Mn 0.7 Ni 0.3 One or more of O2.

[0018] The exhaust gas after the reaction is discharged and recovered after passing through an absorption device; wherein, the exhaust gas is absorbed by an alkaline solution, and if the exhaust gas contains ammonia, it is absorbed by an alkaline solution and then treated by an acidic solution.

[0019] The alkaline solution includes, but is not limited to, sodium hydroxide solution, sodium carbonate solution, and calcium hydroxide solution, and the concentration of the alkaline solution is 0.1–30%; the acidic solution used includes, but is not limited to, hydrochloric acid solution and sulfuric acid solution, and the concentration of the acidic solution is 0.5–20%.

[0020] A fluorinated cathode material is prepared by the method described above, and the resulting oxide cathode material with uniformly fluorinated surface is prepared by the method described above.

[0021] An application of the fluorinated cathode material, specifically its use in the preparation of composite cathode materials for solid-state or liquid batteries.

[0022] The fluorinated cathode material is a lithium battery (or sodium battery, potassium battery) cathode material with surface fluorination modification, and is suitable for composite cathode materials of sulfide or halide-based solid lithium batteries (or sodium batteries, potassium batteries) and composite cathode materials of liquid lithium batteries (or sodium batteries, potassium batteries).

[0023] The solid-state battery composite cathode material is prepared by mixing the fluorinated cathode material, solid electrolyte, and conductive agent.

[0024] The liquid battery composite positive electrode sheet is prepared by mixing the fluorinated positive electrode material, binder, and conductive agent.

[0025] The solid electrolyte is a sulfide electrolyte Li. x M y S z Na x M y S z 、 K x M y S z and halide electrolyte Li x M y X z (X = Cl, Br, etc.), Na x M y X z (X = Cl, Br, etc.), K x M y X z (X = Cl, Br, etc.), sulfide electrolytes include but are not limited to Li6PS5Cl, Li6PS5Br, Li6PS5I, and Li7P3S. 11 Li7PS6, Li 6.35 P 0.65 Si 0.35 S5Br, Li 6.6 P 0.4 Ge 0.6 S5I, Li 3.25 Ge 0.25 P 0.75 S4, Li7Ge3PS 12 Li4GeS4, Li4SnS4, Li 11 AlP2S 12 Li 10 GeP2S 12 Li 10 SnP2S 12 Li 10 SiP2S 12 , 80Li2S·20P2S5, 75Li2S·25P2S5, 70Li2S·30P2S5, 60Li2S·40P2S5, β-Li3PS4–LZNO, β-Li3P S4–Al2O3, β-Li3PS4–SiO2, β-Li3PS4–LLZO, Na3PS4, Na4P2S7, Na3SbS4, Na3AlS4, Na3BS3, Na 11 Sn2PS 12K3SbS4, K3PS4, and halide electrolytes including but not limited to Li3YCl6, Li3InCl6, Li2ZrCl6, Li3YCl3Br3, and Li3YCl 4.5 Br 1.5 , Li2FeCl4, Li2MnCl4, Li6FeCl8, Li6VCl8, Li3HoBr6, Li3ScCl6, Li3LaCl6, Li3SmCl6, Li3ZrCl4O 1.5 , NaTaCl6, Na2ZrCl6, Na3InCl6, NaAlCl4, K3YCl6, K3InCl6.

[0026] The conductive agent is selected from one or more of acetylene black, conductive carbon black (Super P), Ketjen black, vapor-grown carbon fiber (VGCF), carbon nanotubes (CNT), and graphene.

[0027] The adhesive is selected from one or more of polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polytetrafluoroethylene (PTFE), polyimide (PI), polyamide-imide (PAI), and sodium alginate (SA).

[0028] The solid-state battery composite cathode material containing fluorinated cathode material is used to prepare all-solid-state batteries based on sulfide or halide electrolytes. The fluorinated cathode material is used to prepare liquid batteries based on liquid electrolytes.

[0029] Advantages of this invention: The fluorinated cathode material, its preparation method, and its application involved in this invention have significant advantages over previous modification strategies: (1) The fluorinated cathode material simultaneously possesses high structural stability and ionic conductivity at the cathode material / electrolyte interface, exhibiting excellent interfacial stability and low interfacial impedance in both liquid and solid-state batteries. This effectively suppresses interfacial side reactions between the cathode material and the electrolyte, achieving a synergistic improvement in reversibility capacity and cycle stability. (2) The surface uniform fluorination effect based on gas-solid reaction is superior to solid-solid / solid-liquid reaction. Its preparation method achieves uniform fluorination of the cathode surface through the gas-solid interfacial reaction between fluorine-containing gas and oxide cathode material. (3) No water or organic solvents are used, and there is no problem of lithium and transition metal leaching. (4) At the same time, a tail gas absorption stage is introduced to eliminate the potential harm of gaseous products to the human body and the environment.

[0030] This method effectively overcomes the problems of limited application scenarios, complex preparation processes, difficulty in controlling coating uniformity, poor environmental performance, high cost of large-scale production, and excessively high heat treatment temperature in previous technologies. It has the advantages of simple process, low cost of large-scale production, wide applicability, green environmental protection, and uniform fluorination with controllable thickness. Electrochemical test results show that vapor-phase fluorination modification of the cathode surface can significantly enhance the interfacial stability between oxide cathode materials (including layered lithium-rich manganese-based, high-nickel ternary, spinel lithium nickel manganese oxide, lithium cobalt oxide, sodium nickel iron manganese, and sodium nickel manganese oxide) and liquid battery electrolytes and solid-state battery sulfide / halide electrolytes, thereby allowing the high energy density advantage of oxide cathode materials to be fully utilized in secondary batteries.

[0031] This invention relates to a fluorinated cathode material, its preparation method, and its application. The fluorinated cathode material is a surface-modified oxide cathode material suitable for liquid and solid-state batteries. The preparation method employs a gas-solid interface passivation reaction fluorination method: fluorine-containing gas generated from the decomposition of a fluorine source undergoes a gas-solid interface passivation reaction with the oxide cathode, achieving uniform fluorination of the cathode surface. Combined with a tail gas absorption stage, the fluorine-containing gas can be treated in a green manner. During the reaction, the acidic fluorine-containing gas undergoes a fluorination substitution reaction with the alkaline oxide cathode, forming strong metal-fluorine bonds on its surface lattice, significantly enhancing surface structural stability and effectively suppressing cathode / electrolyte interface side reactions, transition metal dissolution, and lattice oxygen release. On the other hand, it undergoes a fluorination substitution reaction with residual alkali on the cathode surface (such as lithium carbonate, lithium hydroxide, sodium carbonate, potassium carbonate, etc.) to generate lithium fluoride (or sodium fluoride, potassium fluoride). This not only accelerates lithium / sodium / potassium ion transport at the cathode interface, protects the cathode structure, and suppresses interface side reactions, but also eliminates the problems of high interfacial impedance and strong reactivity with the electrolyte caused by residual alkali on the surface. Therefore, when the fluorinated cathode material is matched with liquid or solid electrolyte, it still has excellent interface stability even at high charging cut-off voltage, which can simultaneously ensure the high energy density and long cycle life of the battery. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of a dual-temperature zone tube furnace for preparing fluorinated cathode materials, provided in an embodiment of the present invention.

[0033] Figure 2 The images shown are scanning electron microscope (SEM) images and corresponding elemental distribution diagrams of the fluorinated cathode material described in Example 1 of this invention.

[0034] Figure 3 The first charge and discharge specific capacity-voltage curves of the solid-state lithium batteries obtained in Example 1 and Comparative Example 1 provided for embodiments of the present invention.

[0035] Figure 4 A comparison chart of the rate performance of solid-state lithium batteries obtained in Example 1 and Comparative Example 1, provided as embodiments of the present invention.

[0036] Figure 5 A comparison chart of the cycle performance of solid-state lithium batteries obtained in Example 1 and Comparative Example 1, provided as embodiments of the present invention. Detailed Implementation

[0037] The following examples further illustrate specific embodiments of the present invention. It should be noted that the specific embodiments described herein are merely for illustration and explanation and are not intended to limit the scope of the present invention.

[0038] This invention uses a dual-temperature zone tubular furnace to prepare fluorinated cathode materials, which effectively solves the interface incompatibility problem faced by oxide cathodes in liquid and solid batteries, achieving a dual improvement in battery capacity and stability. At the same time, it sets up an exhaust gas absorption stage to eliminate the potential harm of gaseous products to human health and the environment, which is in line with the concept of green production.

[0039] In the temperature control process of this invention, the first heating zone aims to induce the thermal decomposition of the fluorine source, while the second heating zone aims to accelerate the passivation reaction at the gas-solid interface, while avoiding damage to the cathode bulk structure. This method has advantages such as simple process, low cost for large-scale production, wide applicability, environmental friendliness, and uniform fluorination with controllable thickness. It can achieve controllable and uniform surface fluorination of oxide cathode materials, thereby significantly improving their interfacial stability and electrochemical performance in liquid and solid-state batteries.

[0040] Example 1: like Figure 1 As shown, 1g of sodium hexafluorophosphate and 50g of positive electrode material powder Li 1.2 Mn 0.6 Ni 0.2 O2 was evenly distributed in quartz boats in temperature zones one and two, respectively. Argon gas was continuously introduced from one end of temperature zone one in the dual-temperature zone tubular furnace at a flow rate of 20 mL / min, flowing sequentially through temperature zones one, temperature zone two, and the tail gas absorption of a 15% sodium carbonate solution before being discharged. The heating power supplies for temperature zones one and two were started sequentially. In temperature zone one, the temperature was increased to 200°C at a heating rate of 1°C / min and then held at that temperature for 8 hours to allow sodium hexafluorophosphate to pyrolyze and produce fluorine-containing gas. The fluorine-containing gas diffused into temperature zone two with the carrier gas. In temperature zone two, the temperature was increased to 80°C at a heating rate of 5°C / min and then held at that temperature for 8 hours to allow the cathode material powder to undergo a gas-solid interface reaction with the fluorine-containing gas, thus obtaining a cathode material with a uniformly fluorinated surface (see...). Figure 2 ).

[0041] from Figure 2 It can be seen that fluorine is uniformly distributed on the surface of the fluorinated cathode material particles, confirming the successful implementation of the gas-solid interface passivation reaction fluorination strategy.

[0042] Weigh 0.7g of the fluorinated cathode material obtained above, add it to a mortar with 0.3g of sulfide electrolyte Li6PS5Cl and 0.03g of conductive agent VGCF, and manually grind and mix thoroughly to obtain sulfide-based solid lithium battery composite cathode material.

[0043] Weigh 0.8g of the fluorinated positive electrode material obtained above, mix it evenly with 0.1g of binder CMC and 0.1g of conductive agent acetylene black, use 1-methyl-2-pyrrolidone (NMP) as solvent, and obtain liquid lithium battery composite positive electrode sheet by stirring, coating, drying, rolling and stamping.

[0044] Example 2: 2g of lithium tetrafluoroborate and 50g of positive electrode material powder LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2 secondary microspheres were uniformly spread in quartz boats in temperature zones one and two, respectively. Argon gas was continuously introduced from one end of temperature zone one in the dual-temperature zone tubular furnace at a flow rate of 30 mL / min, flowing sequentially through temperature zone one, temperature zone two, and the tail gas of the 15% sodium carbonate solution before being discharged. The heating power supplies for temperature zones one and two were started sequentially. In temperature zone one, the temperature was heated to 275°C at a heating rate of 2°C / min and held at that temperature for 6 hours, so that lithium tetrafluoroborate could be pyrolyzed to produce fluorine-containing gas. The fluorine-containing gas diffused into temperature zone two with the carrier gas. In temperature zone two, the cathode material powder was heated to 70°C at a heating rate of 3°C / min and held at that temperature for 6 hours, so that the cathode material powder and the fluorine-containing gas could undergo a gas-solid interface reaction, thus obtaining a cathode material with a uniformly fluorinated surface.

[0045] Weigh 0.7g of the fluorinated cathode material obtained above, add it to a mortar with 0.3g of halide electrolyte Li3InCl6 and 0.03g of conductive agent CNT, and manually grind and mix thoroughly to obtain halide-based solid lithium battery composite cathode material.

[0046] Weigh 0.8g of the fluorinated positive electrode material obtained above, mix it evenly with 0.1g of binder PVDF and 0.1g of conductive agent Super P, use 1-methyl-2-pyrrolidone (NMP) as solvent, and obtain liquid lithium battery composite positive electrode sheet by stirring, coating, drying, rolling and stamping.

[0047] Example 3: 2.5 g of lithium hexafluorophosphate and 50 g of positive electrode material powder LiCoO2 were uniformly spread in quartz boats in temperature zones one and two, respectively. Nitrogen gas was continuously introduced from one end of temperature zone one in the dual-temperature zone tubular furnace at a flow rate of 35 mL / min, and then passed through temperature zone one, temperature zone two, and a saturated calcium hydroxide solution (0.17%) before being absorbed by the tail gas and discharged. The heating power supplies for temperature zones one and two were started sequentially. In temperature zone one, the temperature was heated to 185°C at a heating rate of 1°C / min and held at that temperature for 8 hours to allow the lithium hexafluorophosphate to pyrolyze and generate fluorine-containing gas. The fluorine-containing gas diffused into temperature zone two with the carrier gas. In temperature zone two, the temperature was heated to 70°C at a heating rate of 5°C / min and held at that temperature for 8 hours to allow the positive electrode material powder to undergo a gas-solid interface reaction with the fluorine-containing gas, thus obtaining a positive electrode material with a uniformly fluorinated surface.

[0048] Weigh 0.7g of the fluorinated cathode material obtained above, and mix it with 0.3g of the sulfide electrolyte Li7P3S. 11 Add to a mortar and grind thoroughly by hand to obtain sulfide-based solid-state lithium battery composite cathode material.

[0049] Weigh 0.8g of the fluorinated positive electrode material obtained above, mix it evenly with 0.1g of binder PVDF and 0.1g of conductive agent Super P, use 1-methyl-2-pyrrolidone (NMP) as solvent, and obtain liquid lithium battery composite positive electrode sheet by stirring, coating, drying, rolling and stamping.

[0050] Example 4: 0.5g of sodium hexafluorophosphate and 50g of positive electrode material powder LiNi 0.5 Mn 1.5 O4 was evenly spread in the quartz boats of temperature zones one and two, respectively. Argon gas was continuously introduced from one end of temperature zone one of the dual-temperature zone tubular furnace at a flow rate of 20 mL / min, and flowed sequentially through temperature zone one, temperature zone two, and a saturated calcium hydroxide solution (0.17%). The tail gas was absorbed and then discharged. The heating power supplies of temperature zones one and two were started sequentially. Sodium hexafluorophosphate in temperature zone one was heated to 200℃ at a heating rate of 2℃ / min and held at the temperature for 6 hours to allow the sodium hexafluorophosphate to pyrolyze and produce fluorine-containing gas. The fluorine-containing gas diffused into temperature zone two with the carrier gas. Temperature zone two was heated to 60℃ at a heating rate of 3℃ / min and held at the temperature for 6 hours to allow the cathode material powder to undergo a gas-solid interface reaction with the fluorine-containing gas, thus obtaining a cathode material with a uniformly fluorinated surface.

[0051] Weigh 0.6g of the obtained fluorinated cathode material and mix it with 0.4g of the halide electrolyte Li3YCl. 4.5 Br 1.5 0.03g of conductive agent VGCF was added to a mortar and manually ground and mixed thoroughly to obtain a halide-based solid-state lithium battery composite cathode material.

[0052] Weigh 0.8g of the fluorinated positive electrode material obtained above, mix it evenly with 0.1g of binder PVDF and 0.1g of conductive agent CNT, use 1-methyl-2-pyrrolidone (NMP) as solvent, and obtain liquid lithium battery composite positive electrode sheet by stirring, coating, drying, rolling and stamping.

[0053] Example 5: 3 g of lithium hexafluorophosphate and 50 g of positive electrode material powder NaNi were mixed. 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 was evenly distributed in the quartz boats of temperature zones one and two, respectively. Nitrogen gas was continuously introduced from one end of temperature zone one of the dual-temperature zone tubular furnace at a flow rate of 25 mL / min, and then passed through temperature zone one, temperature zone two, and the tail gas absorption of 10% sodium hydroxide solution before being discharged. Then, the heating power supplies of temperature zone one and temperature zone two were started in sequence. Temperature zone one was heated to 185°C at a heating rate of 2°C / min and held at the temperature for 10 hours to allow lithium hexafluorophosphate to pyrolyze and generate fluorine-containing gas. The fluorine-containing gas diffused into temperature zone two with the carrier gas. Temperature zone two was heated to 60°C at a heating rate of 2°C / min and held at the temperature for 10 hours to allow the cathode material powder to undergo a gas-solid interface reaction with the fluorine-containing gas, thus obtaining a cathode material with a uniformly fluorinated surface.

[0054] Weigh 0.6g of the fluorinated cathode material obtained above, add it to a mortar with 0.4g of sulfide electrolyte Na3SbS4 and 0.03g of conductive agent VGCF, and manually grind and mix thoroughly to obtain sulfide-based solid sodium battery composite cathode material.

[0055] Weigh 0.8g of the fluorinated positive electrode material obtained above, mix it evenly with 0.1g of binder SA and 0.1g of conductive agent Ketjen black, use 1-methyl-2-pyrrolidone (NMP) as solvent, and obtain a liquid sodium battery composite positive electrode sheet by stirring, coating, drying, rolling and stamping.

[0056] Example 6: 2 g of sodium tetrafluoroborate and 50 g of positive electrode material powder NaNi were mixed. 0.5 Mn 0.5 O2 was evenly distributed in the quartz boats of temperature zones one and two, respectively. Argon gas was continuously introduced from one end of temperature zone one of the dual-temperature zone tubular furnace at a flow rate of 20 mL / min, and then passed through temperature zone one, temperature zone two, and the tail gas of 10% sodium hydroxide solution before being discharged. Then, the heating power supplies of temperature zone one and temperature zone two were started in sequence. Temperature zone one was heated to 200℃ at a heating rate of 1℃ / min and held at the temperature for 12 hours, so that sodium tetrafluoroborate could be pyrolyzed to produce fluorine-containing gas. The fluorine-containing gas diffused into temperature zone two with the carrier gas. Temperature zone two was heated to 80℃ at a heating rate of 5℃ / min and held at the temperature for 12 hours, so that the cathode material powder and the fluorine-containing gas could undergo a gas-solid interface reaction, thus obtaining a cathode material with uniform surface fluorination.

[0057] Weigh 0.6g of the fluorinated cathode material obtained above, add it to a mortar with 0.4g of halide electrolyte NaTaCl6 and 0.03g of conductive agent CNT, and manually grind and mix thoroughly to obtain halide-based solid sodium battery composite cathode material.

[0058] Weigh 0.8g of the fluorinated positive electrode material obtained above, mix it evenly with 0.1g of binder PVDF and 0.1g of conductive agent acetylene black, use 1-methyl-2-pyrrolidone (NMP) as solvent, and obtain a liquid sodium battery composite positive electrode sheet by stirring, coating, drying, rolling and stamping.

[0059] Comparative Example 1: Weigh 0.7g of positive electrode material Li 1.2 Mn 0.6 Ni 0.2 O2, along with 0.3g of sulfide electrolyte Li6PS5Cl and 0.03g of conductive agent VGCF, were added to a mortar and manually ground and mixed thoroughly to obtain a sulfide-based solid-state lithium battery composite cathode material.

[0060] Weigh 0.8g of positive electrode material Li 1.2 Mn 0.6 Ni 0.2 O2 is uniformly mixed with 0.1g of binder CMC and 0.1g of conductive agent acetylene black, and 1-methyl-2-pyrrolidone (NMP) is used as solvent. The mixture is stirred, coated, dried, rolled and stamped to obtain a liquid lithium battery composite positive electrode sheet.

[0061] Comparative Example 2: Weigh 0.7g of positive electrode material LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2, along with 0.3g of halide electrolyte Li3InCl6 and 0.03g of conductive agent CNT, were added to a mortar and manually ground and mixed thoroughly to obtain a halide-based solid-state lithium battery composite cathode material.

[0062] Weigh 0.8g of positive electrode material LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2 is uniformly mixed with 0.1g of binder PVDF and 0.1g of conductive agent Super P, and 1-methyl-2-pyrrolidone (NMP) is used as solvent. The mixture is stirred, coated, dried, rolled and stamped to obtain a liquid lithium battery composite positive electrode sheet.

[0063] Comparative Example 3: Weigh out 0.7g of positive electrode material LiCoO2 and 0.3g of sulfide electrolyte Li7P3S. 11 Add to a mortar and grind thoroughly by hand to obtain sulfide-based solid-state lithium battery composite cathode material.

[0064] Weigh 0.8g of positive electrode material LiCoO2, mix it evenly with 0.1g of binder PVDF and 0.1g of conductive agent Super P, use 1-methyl-2-pyrrolidone (NMP) as solvent, and obtain liquid lithium battery composite positive electrode sheet by stirring, coating, drying, rolling and stamping.

[0065] Comparative Example 4: Weigh 0.6g of positive electrode material LiNi 0.5 Mn 1.5 O4, with 0.4g of halide electrolyte Li3YCl 4.5 Br 1.5 0.03g of conductive agent VGCF was added to a mortar and manually ground and mixed thoroughly to obtain a halide-based solid-state lithium battery composite cathode material.

[0066] Weigh 0.8g of positive electrode material LiNi 0.5 Mn 1.5 O4 is uniformly mixed with 0.1g of binder PVDF and 0.1g of conductive agent CNT, and 1-methyl-2-pyrrolidone (NMP) is used as solvent. The mixture is stirred, coated, dried, rolled and stamped to obtain a liquid lithium battery composite positive electrode sheet.

[0067] Comparative Example 5: Weigh 0.6g of the positive electrode material NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, along with 0.4g of sulfide electrolyte Na3SbS4 and 0.03g of conductive agent VGCF, were added to a mortar and manually ground and mixed thoroughly to obtain a sulfide-based solid sodium battery composite cathode material.

[0068] Weigh 0.8g of the positive electrode material NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 is uniformly mixed with 0.1g of binder SA and 0.1g of conductive agent Ketjen black, and 1-methyl-2-pyrrolidone (NMP) is used as solvent. The mixture is stirred, coated, dried, rolled and stamped to obtain a liquid sodium battery composite positive electrode sheet.

[0069] Comparative Example 6: Weigh 0.6g of the positive electrode material NaNi 0.5 Mn 0.5 O2, along with 0.4g of halide electrolyte NaTaCl6 and 0.03g of conductive agent CNT, were added to a mortar and manually ground and mixed thoroughly to obtain a halide-based solid sodium battery composite cathode material.

[0070] Weigh 0.8g of the positive electrode material NaNi 0.5 Mn 0.5O2 is uniformly mixed with 0.1g of binder PVDF and 0.1g of conductive agent acetylene black, and 1-methyl-2-pyrrolidone (NMP) is used as solvent. The mixture is stirred, coated, dried, rolled and stamped to obtain a liquid sodium battery composite positive electrode sheet.

[0071] Comparative Example 7: Fluorine coating of the cathode material was performed using the optimal battery performance conditions described in patent CN117219744A. 50g of cathode material powder Li... 1.2 Mn 0.6 Ni 0.2 O2 and 0.2 wt% LiF were ball-milled for 4 hours at a speed of 300 r / min to obtain mixture 1. Mixture 1 was then manually shaken to mix with 30 wt% porous alumina (200 µm particle size) to obtain mixture 2. Mixture 2 was placed in an atmosphere with an oxygen content of 80 vol% and sintered at 950 °C for 8 hours. After removing the porous alumina by sieving, sintered material 1 was obtained. Finally, sintered material 1 was placed in an atmosphere with an oxygen content of 5 vol% and sintered at 450 °C for 2 hours. After sieving, fluorine-coated cathode material was obtained.

[0072] Weigh 0.7g of the fluorine-coated cathode material obtained above, add it to a mortar with 0.3g of sulfide electrolyte Li6PS5Cl and 0.03g of conductive agent VGCF, and manually grind and mix thoroughly to obtain sulfide-based solid lithium battery composite cathode material.

[0073] Weigh 0.8g of the fluorine-coated positive electrode material obtained above, mix it evenly with 0.1g of binder CMC and 0.1g of conductive agent acetylene black, use 1-methyl-2-pyrrolidone (NMP) as solvent, and obtain liquid lithium battery composite positive electrode sheet by stirring, coating, drying, rolling and stamping.

[0074] All-solid-state battery and liquid battery assembly and electrochemical performance testing: All-solid-state battery assembly was carried out in a glove box specifically designed for solid-state batteries, filled with an argon atmosphere (water content ≤0.1ppm, oxygen content ≤0.1ppm). (1) Weigh 80 mg of sulfide electrolyte powder and place it into the inner cavity of the solid-state battery mold. Cold press once at 350 MPa to obtain the electrolyte layer. Weigh 10 mg of the sulfide-based solid-state lithium battery composite cathode material obtained in the above embodiments or comparative examples and evenly spread it on one side of the electrolyte layer in the solid-state battery mold. Cold press once at 600 MPa to obtain the composite cathode layer. Finally, place φ10 indium sheet (100 µm thick), φ3 lithium sheet (50 µm thick), and φ10 copper foam (300 µm thick) sequentially on the other side of the electrolyte layer in the solid-state battery mold. After sealing, cold press once at 200 MPa to obtain the sulfide-based all-solid-state lithium battery. Similarly, place 40 mg of Na... 15 Sn4 alloy was sealed and then cold-pressed once under a pressure of 200 MPa to obtain a sulfide-based all-solid-state sodium battery.

[0075] (2) Weigh 40 mg of sulfide electrolyte powder and 40 mg of halide electrolyte powder sequentially and place them into the inner cavity of the solid-state battery mold. Cold press once at 350 MPa to obtain a sulfide-halide bilayer electrolyte layer. Weigh 10 mg of the halide-based solid-state lithium battery composite cathode material obtained in the above embodiments or comparative examples and evenly spread it on one side of the halide electrolyte layer in the solid-state battery mold. Cold press once at 600 MPa to obtain a composite cathode layer. Finally, place a φ10 indium sheet (100 µm thick), a φ3 lithium sheet (50 µm thick), and a φ10 copper foam (300 µm thick) sequentially on one side of the sulfide electrolyte layer in the solid-state battery mold. After sealing, cold press once at 200 MPa to obtain a halide-based all-solid-state lithium battery. Similarly, place 40 mg of Na... 15 Sn4 alloy was sealed and then cold-pressed once under a pressure of 200 MPa to obtain a halide-based all-solid-state sodium battery.

[0076] Liquid batteries are assembled in a glove box specifically designed for liquid batteries, filled with an argon atmosphere (water content ≤ 0.1 ppm, oxygen content ≤ 0.1 ppm). (1) Using lithium metal as the counter electrode, PP three-layer microporous membrane as the separator, and 1 mol / L LiPF6|EC:DEC (1:1) as the electrolyte, the liquid lithium battery composite positive electrode sheet containing the fluorinated positive electrode material prepared in each example or comparative example was used as the working electrode; in the CR2032 coin cell, the liquid lithium battery was assembled in the order of counter electrode, separator, electrolyte and working electrode.

[0077] (2) Using metallic sodium as the counter electrode and reference electrode, glass fiber (Whatman) as the separator, and electrolyte as 1 mol / L NaClO4|EC:DEC (1:1:1), the liquid sodium battery composite positive electrode sheet containing the fluorinated positive electrode material prepared in each example or comparative example is used as the working electrode; in the CR2032 coin cell, the liquid sodium battery is assembled in the order of counter electrode, separator, electrolyte and working electrode.

[0078] The all-solid-state lithium / sodium batteries obtained above were placed in a 30°C constant temperature chamber for 3 hours, and the liquid lithium / sodium batteries were placed in a 30°C constant temperature chamber for 6 hours. Then, electrochemical charge-discharge tests were performed on them using the Wuhan Landian testing system.

[0079] Example 1: Obtaining the cathode material Li 1.2 Mn 0.6 Ni 0.2 The voltage range for O2 charge / discharge testing is 2.0~4.8V (vs. Li). + / Li), 1C = 200 mA / g.

[0080] Example 2: Obtaining the cathode material LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 The voltage range for O2 charge / discharge testing is 2.7~4.7V (vs. Li). + / Li), 1C = 200 mA / g.

[0081] Example 3 shows that the voltage range for charge-discharge testing of the positive electrode material LiCoO2 is 2.8~4.7V (vs. Li). + / Li), 1C = 140 mA / g.

[0082] Example 4: Obtaining the cathode material LiNi 0.5 Mn 1.5 The voltage range for O2 charge / discharge testing is 3.0~5.1V (vs. Li). + / Li), 1C = 140 mA / g.

[0083] Example 5: Obtaining the cathode material NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 The voltage range for O2 charge / discharge testing is 2.0~4.3V (vs. Na). + / Na), 1C = 240 mA / g.

[0084] Example 6: Obtaining the cathode material NaNi 0.5 Mn 0.5 The voltage range for O2 charge / discharge testing is 2.0~4.3V (vs. Na).+ / Na), 1C = 240 mA / g.

[0085] The electrochemical test results for solid-state and liquid batteries are shown in Tables 1 and 2, respectively, presenting comparative data on the initial discharge capacity, coulombic efficiency, and capacity retention at room temperature for Examples 1-6 and Comparative Examples 1-7. It is evident that the gas-solid interface passivation reaction fluorination strategy proposed in this invention, through uniform surface fluorination of the oxide cathode material, can significantly suppress problems such as cathode / electrolyte interface side reactions, transition metal dissolution, and lattice oxygen release, thereby greatly improving the reversible capacity and cycle stability of the oxide cathode in both liquid and solid-state batteries, and exhibits high versatility.

[0086] Table 1 Electrochemical performance of solid-state batteries obtained in Examples 1-6 and Comparative Examples 1-7

[0087] Table 2 Electrochemical performance of the liquid batteries obtained in Examples 1-6 and Comparative Examples 1-7

[0088] The electrochemical test results for solid-state and liquid batteries are shown in Tables 1 and 2, respectively, presenting comparative data on the initial discharge capacity, coulombic efficiency, and capacity retention at room temperature for Examples 1-6 and Comparative Examples 1-7. It is evident that the gas-solid interface passivation reaction fluorination strategy proposed in this invention, through uniform surface fluorination of the oxide cathode material, can significantly suppress side reactions at the cathode / electrolyte interface, transition metal dissolution, and lattice oxygen release, thereby greatly improving the reversible capacity and cycle stability of the oxide cathode in both liquid and solid-state batteries. Furthermore, it exhibits high versatility and is superior to existing modification strategies.

[0089] Furthermore, the first charge and discharge specific capacity-voltage curves, rate performance comparison, and cycle performance comparison of the solid-state lithium batteries obtained from Embodiment 1 and Comparative Example 1 of this invention are presented. Figures 3-5 It can be seen that the fluorinated lithium-rich manganese-based cathode material prepared by the preparation method of the present invention exhibits a reversible capacity close to that of a liquid battery in a room temperature sulfide solid-state battery, demonstrating excellent rate performance and cycle stability.

Claims

1. A method for preparing a fluorinated cathode material, characterized in that: Using a substance that can decompose upon heating to produce fluorine-containing gas as a fluorine source, the fluorine source on the surface of the cathode material undergoes thermal decomposition to produce fluorine-containing gas, which then reacts with the oxides in the cathode material to passivate the gas-solid interface, thereby achieving uniform fluorination on the surface of the cathode material and obtaining a fluorinated cathode material.

2. The method for preparing the fluorinated cathode material according to claim 1, characterized in that: In a dual-temperature zone tubular furnace, the fluorine source decomposes upon heating to produce fluorine-containing gas. The fluorine-containing gas diffuses with the carrier gas to the surface of the cathode material and undergoes a gas-solid interface passivation reaction with the cathode material, thereby achieving uniform fluorination on the surface of the cathode material.

3. The method for preparing the fluorinated cathode material according to claim 1 or 2, characterized in that: The fluorine source and the oxide cathode material are placed in temperature zone one and temperature zone two of a dual-temperature zone tube furnace, respectively. Then, an inert carrier gas is continuously introduced from one end of temperature zone one of the dual-temperature zone tube furnace at a flow rate of 10–200 mL / min. The heating power supplies of temperature zone one and temperature zone two are started in sequence, so that the fluorine source decomposes upon heating to produce fluorine-containing gas. The fluorine-containing gas diffuses with the carrier gas to the surface of the cathode material in temperature zone two, where it undergoes a gas-solid interface passivation reaction with the oxide in the cathode material, thereby achieving uniform fluorination of the cathode material surface and obtaining a fluorinated cathode material.

4. The method for preparing the fluorinated cathode material according to claim 1, characterized in that: The mass ratio of the fluorine source to the positive electrode material is 1-50:100; wherein the fluorine source is a substance that can decompose to produce fluorine-containing gas when heated.

5. The method for preparing the fluorinated cathode material according to claim 4, characterized in that: The substance that can decompose upon heating to produce fluorine-containing gas is one or more of the following: ammonium hexafluorophosphate, sodium hexafluorophosphate, lithium hexafluorophosphate, potassium hexafluorophosphate, cesium hexafluorophosphate, ammonium tetrafluoroborate, sodium tetrafluoroborate, lithium tetrafluoroborate, diazo tetrafluoroborate, and potassium tetrafluoroborate.

6. The method for preparing the fluorinated cathode material according to claim 3, characterized in that: The heating temperature of the first temperature zone is the thermal decomposition temperature of the fluorine source, and the heating rate is 1–10 °C / min. The heating temperature of the second temperature zone is 50–300℃, and the heating rate is 1–10℃ / min; The constant temperature heating time for temperature zone one and temperature zone two is 1–20 hours.

7. The method for preparing the fluorinated cathode material according to any one of claims 1-3, characterized in that: The positive electrode material is Li oxide. x M y O2 (0<x<2, 0<y≤1), Na x M y O2 (0 < x <2, 0<y≤1) or K x M y O2 (0 < x <2, 0<y≤1); where M is a metal or metalloid element other than Group 1 in the periodic table.

8. The method for preparing the fluorinated cathode material according to any one of claims 1-3, characterized in that: The exhaust gas after the reaction is discharged and recovered after passing through an absorption device; wherein, the exhaust gas is absorbed by an alkaline solution, and if the exhaust gas contains ammonia, it is absorbed by an alkaline solution and then treated by an acidic solution.

9. A method for preparing a fluorinated cathode material according to claim 1, characterized in that: The oxide cathode material with uniformly fluorinated surface obtained by the method described in claim 1.

10. An application of the fluorinated cathode material according to claim 9, characterized in that: The application of the fluorinated cathode material in the preparation of composite cathode materials for solid or liquid batteries.

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