A method for modifying the surface and grain boundaries of a fluorinated stabilized nickel-based substrate cathode material for lithium-ion batteries.

Abstract

This invention relates to a method for modifying the surface and grain boundaries of a fluorinated stable nickel-based layered cathode material for lithium-ion batteries. Specifically, the nickel-based layered material is micro-etched using a fluorine-containing organic acidic solution. After solid-liquid separation and drying, it is calcined in air or oxygen at two temperature stages to obtain a nickel-based layered cathode material with fluorinated stability at both the surface and grain boundaries and a complete bulk layered structure.

Description

Technical Field

[0001] This invention discloses a method for modifying the surface and grain boundaries of nickel-based silane cathode materials by fluorination. This method can fluorinate the surface and grain boundaries of nickel-based silane cathode materials, thereby effectively stabilizing them. It is a treatment method to improve the processing performance and electrochemical stability of nickel-based silane cathode materials, belonging to the field of lithium-ion battery cathode materials. Background Technology

[0002] Lithium-ion batteries (LIBs) have been widely used in smartphones, laptops, electric vehicles, and other electronic devices. However, the energy density and lifespan of lithium-ion batteries are often limited by electrode materials, especially the cathode material. Among various cathode materials, nickel-based layered cathode materials (LiNi) are particularly popular. x M 1-x O2 (0.3≤x≤1, M selected from one or more of Co, Mn, Al, Mg, Fe, Zr, Mo) is widely used due to its high voltage plateau, high reversible capacity, and low cost. To further leverage the capacity potential of nickel-based cathode materials, various nano-nickel-based cathode materials have been prepared to shorten lithium-ion transport distances and improve lithium-ion conductivity. However, nano-nickel-based cathode materials often suffer from low loading density. Aggregating primary nanoparticles into micron-sized spherical secondary particles is a common strategy to improve loading density. However, the capacity of spherical secondary particles decreases with increasing cycle number, mainly due to surface and interface side reactions, irreversible phase transitions, and primary particle crack growth along grain boundaries. Extensive research has been conducted on the specific mechanisms of surface and interface side reactions and irreversible phase transitions in capacity decay. On the other hand, the influence of primary particle crack growth along grain boundaries on capacity decay is receiving increasing attention. Crack growth can lead to problems such as poor contact between positive electrode active materials, exposure of more interfaces causing aggravated side reactions, and more extensive irreversible phase transitions on the surface, which seriously affect the long-cycle stability of nickel-based substrate positive electrode materials.

[0003] Traditional surface modification strategies can effectively stabilize the surface of nickel-based metamorphic cathode materials, thereby improving cycle stability. For example, it has been reported to use stabilizing oxides (such as Al2O3, ZrO2, etc.) or lithium-ion conductors (Li3PO4, LiNbO3, etc.) for coating modification to suppress side reactions between the active material and the electrolyte, thus improving cycle life. However, nickel-based metamorphic cathode materials are usually composed of spherical secondary particles made up of sheet-like primary particles. Common coating methods can only distribute the coating layer on the surface of the secondary particles. As stress accumulates during charge-discharge cycles, cracks grow and particles break down. The newly exposed interfaces are not coated, and interfacial side reactions and irreversible surface phase transitions will occur again, leading to a rapid decrease in capacity. The breakage of secondary particles in nickel-based metamorphic cathode materials is mainly caused by cracks growing along grain boundaries. Conventional coating modification methods are difficult to solve the capacity decay problem caused by the breakage of secondary particles in nickel-based metamorphic cathode materials. If a uniform and stable modification layer can be formed at the interfaces of both primary and secondary particles, the above problems can be solved. Yan et al. reported the use of atomic layer deposition (ALD) to uniformly distribute Li3PO4 at the grain boundaries of NCM811 particles. After annealing at 600 °C, the Li3PO4 injected along the grain boundaries was uniformly coated onto the surface of the primary NCM811 particles, achieving excellent cycling stability (Nat. Energy 3, 600–605, 2018). Dong et al. reported the use of precipitation to uniformly coat Co onto the primary NCM811 particles. x The B layer then achieves excellent electrochemical performance (Nat. Energy 6, 362–371, 2021). Both of the above works can achieve modification of the secondary particle surface and primary particle grain boundary interface of nickel-based crystalline cathode materials, but they also have problems such as expensive instruments or complex processes. Summary of the Invention

[0004] In view of this, the problem to be solved by the present invention is to overcome the shortcomings of the prior art, and the purpose is to provide a method for modifying the surface and grain boundaries of nickel-based fluoropolymer cathode materials for lithium-ion batteries that is relatively simple in process, low in cost, and has a wide range of application prospects.

[0005] Therefore, the present invention provides a method for modifying the surface and grain boundaries of a nickel-based solid cathode material for fluorinated stable lithium-ion batteries. The method involves micro-etching the nickel-based solid material with a fluorine-containing organic acid solution, followed by solid-liquid separation and drying, and then calcining it in air or oxygen at two temperature stages to obtain a nickel-based solid cathode material with fluorinated stable surface and grain boundaries.

[0006] In the inventors' preliminary research, uniform modification of primary / secondary fluoride particles and improvement of electrochemical performance were achieved through treatment with hydrofluoric acid solution combined with one-step calcination. However, this work did not discuss the calcination regime and its effect on the crystal structure, resulting in severe capacity decay after 400 cycles at room temperature, 0.5°C, and therefore, its electrochemical performance needed further improvement. Therefore, the inventors creatively designed a simple and ingenious secondary sintering modification method to simultaneously adjust the surface of secondary particles and the grain boundary interface of primary particles, ensuring uniform modification while optimizing the calcination regime to ensure the stability of the material's crystal structure, ultimately obtaining a high-performance nickel-based cathode material. Specifically, this invention uses an acidic solution containing fluorine to micro-etch the nickel-based substrate material. After solid-liquid separation and drying of the mixed lithium, the calcination stage first ensures uniform lithium source distribution under certain temperature conditions, then increases the sintering temperature and holds it to improve the material's crystallinity, resulting in a nickel-based substrate cathode material with stabilized surface and grain boundaries.

[0007] Preferably, the chemical composition of the nickel-based cathode material is LiNi. x M 1-x O2, wherein 0.3≤x≤1, and M is selected from at least one of Co, Mn, Al, Mg, Fe, Zr, and Mo; preferably, the nickel-based morphological cathode material is formed by the agglomeration of primary particles into spherical secondary particles; more preferably, the particle size of the primary particles is 200-400 nm, and the total particle size of the spherical secondary particles is 8-15 μm.

[0008] In this invention, the processing method is a novel material modification process design. The modified nickel-based morphological material possesses a uniform and stable surface and internal grain boundary modification layer, effectively stabilizing the secondary particle surface and primary particle interface (grain boundary) of the nickel-based morphological material. The surface modification layer can prevent the deactivation side reaction between the active material and the electrolyte, thereby improving the electrochemical stability of the material. The primary particle interface (grain boundary) modification layer can inhibit crack growth, prevent internal particles from being directly exposed to the electrolyte, and improve the long-cycle stability of the nickel-based morphological cathode material.

[0009] Preferably, the fluorine-containing organic acid solution is an organic fluorine acid solution; more preferably, the organic fluorine acid is at least one selected from tetrafluoroterephthalic acid, fluorobenzoic acid, and fluoropyridinecarboxylic acid. In this invention, treatment with a fluorine-containing organic acid solution followed by staged calcination at a specific temperature enables the material to possess a fluorinated stable interface and good crystallinity, thereby improving the cycle stability of the nickel-based substrate cathode material. This method is relatively simple, low-cost, and significantly improves performance, making it a potentially widely applicable modification technology for nickel-based substrate cathode materials.

[0010] Preferably, the concentration of the fluorine-containing organic acidic solution is 0.01–1 mol / L, more preferably 0.01–0.1 mol / L; the solid-liquid ratio of the nickel-based substrate to the fluorine-containing organic acidic solution is 1:(1–20), more preferably 1:(1–10); the mixing and stirring reaction temperature is 0–95°C, more preferably 0–60°C, and the time is 1–300 min, more preferably 30–200 min.

[0011] Preferably, the solvent for the fluorine-containing organic acidic solution is at least one of deionized water and ethanol.

[0012] Preferably, the micro-etching is carried out under stirring conditions at 0–60°C for a reaction time not exceeding 200 min.

[0013] Preferably, the solid-liquid separation method is at least one of natural evaporation, centrifugal separation, and vacuum filtration; the drying method is at least one of oven drying and freeze drying.

[0014] Preferably, a lithium source is added after drying and before high-temperature calcination; the lithium source is at least one of lithium hydroxide, lithium acetate, and lithium nitrate; the molar ratio of the nickel-based crystalline material to the lithium source is 1:(0-0.8), preferably 1:(0-0.6).

[0015] Preferably, the staged calcination process is as follows: first, at a low temperature of 300-600℃ (preferably 400-550℃), the temperature is held for 60-360 min (preferably 180-300 min); then the temperature is increased to 700-1000℃ (preferably 700-900℃), and the temperature is held for another 10-240 min (preferably 60-120 min).

[0016] On the other hand, the present invention also provides a modified nickel-based morphological cathode material prepared according to the above-described processing method, characterized in that the modified nickel-based morphological cathode material comprises: a nickel-based morphological cathode material and an amorphous fluoride modification layer distributed on the surface of the nickel-based morphological cathode material; the chemical composition of the amorphous fluoride modification layer is AF. y , where 0 < y < 4, A is selected from at least one of Li, Co, Mn, Al, Mg, Fe, Zr, and Mo, and the thickness does not exceed 10 nm.

[0017] Beneficial effects:

[0018] This invention provides a method for treating the surface and grain boundaries of a fluorinated stable nickel-based solid cathode material for lithium-ion batteries. The method involves reacting a fluorine-containing organic acidic solution with an alkaline nickel-based solid material to generate a fluorine-rich modified layer on the surface and at the grain boundaries. Further staged calcination ensures a uniform and stable fluorine-containing modified layer on the material surface and at the internal grain boundaries, maintaining the integrity of the bulk layered structure. The fluorinated modified layer on the particle surface effectively reduces the intensity of side reactions between the nickel-based solid material and the electrolyte, stabilizes the material's surface structure, and improves its electrochemical stability. Furthermore, the fluorine-rich modified layer generated at the primary particle interface (i.e., grain boundaries) of the nickel-based solid material treated with the organic acidic fluorine-containing solution effectively inhibits the growth of cracks along grain boundaries, preventing internal particles from being directly exposed to the electrolyte and improving the long-cycle stability of the nickel-based solid cathode material (capacity retention of 80% or more, preferably 85% or more, more preferably 90% or more, and most preferably 95% or more at 0.5C and 500 cycles). This preparation method solves the problems of uneven distribution of modified layers and inability to modify the interior of nickel-based bulk material particles in existing preparation processes. It can not only obtain nickel-based bulk cathode materials with stable fluorination on both the surface and grain boundaries and stable bulk layered structure, but also simplify the preparation process and reduce the synthesis cost. Attached Figure Description

[0019] Figure 1 The image shows the X-ray powder diffraction (XRD) of the nickel-based cathode material prepared in Example 1, where the abscissa is 2Theta(2θ) / degree and the ordinate is intensity.

[0020] Figure 2 A scanning electron microscope (SEM) of the nickel-based cathode material prepared in Example 1 before calcination;

[0021] Figure 3 A scanning electron microscope image of the nickel-based cathode material prepared in Example 1 after calcination;

[0022] Figure 4 Transmission electron microscopy (TEM) of the nickel-based cathode material prepared in Example 1;

[0023] Figure 5 The elemental distribution diagram of the nickel-based cathode material prepared in Example 1 is shown in Figure 1 (a is SEM image, b is fluorine, c is nickel, c is cobalt, d is manganese).

[0024] Figure 6 The graphs show the first electrochemical charge-discharge cycles of the nickel-based cathode materials prepared in Comparative Example 1 and Example 1, with the horizontal axis representing specific capacity in mAh g. -1 The vertical axis represents voltage.

[0025] Figure 7 This is a comparison graph of the cycling performance of the nickel-based cathode materials prepared in Comparative Example 1 and Example 1, where the horizontal axis represents the number of cycles and the vertical axis represents the discharge capacity (mAhg). -1 ;

[0026] Figure 8 A scanning electron microscope image of the modified nickel-based cathode material prepared in Example 2 before calcination;

[0027] Figure 9 This is the first electrochemical charge-discharge diagram of the nickel-based cathode material prepared in Example 2, where the horizontal axis represents the specific capacity in mAh / g. -1 The vertical axis represents voltage. Detailed Implementation

[0028] The present invention will be further illustrated by the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the present invention.

[0029] The purpose of this invention is to address the current limitations of nickel-based layered cathode materials, which suffer from poor cycle stability. Conventional coating methods can only focus on the outer surface of nickel-based layered cathode particles, failing to modify the primary particle interfaces (grain boundaries) within the material. By utilizing a fluorine-containing organic acidic solution to react with alkaline nickel-based layered cathode materials and precisely controlling the reaction conditions, fluorine can be enriched on both the surface and the primary particle interfaces (grain boundaries) of the nickel-based layered cathode material. Through staged calcination, both the material surface and grain boundaries are fluorinated and stabilized while maintaining the integrity of the bulk layered structure, thereby achieving excellent cycle performance. The following exemplarily illustrates the nickel-based layered cathode material modification method provided by this invention.

[0030] In this invention, a fluorine-containing organic acidic solution is used to micro-etch nickel-based substrate cathode materials (LiAO2 + organic F → AF). x +Li + After solid-liquid separation and drying of the lithium mixture, the material is sintered in stages under specific temperature conditions to maintain good crystallinity, resulting in a nickel-based substrate cathode material with stable surface and grain boundary fluorination and a complete bulk layered structure. The nickel-based substrate material consists of spherical secondary particles formed by the agglomeration of primary particles, with gaps between the primary particles, and exhibits weak alkalinity. The mixing and stirring reaction involves micro-etching of the nickel-based substrate material with a fluorine-containing organic acid solution. By precisely controlling the concentration of the fluorine-containing organic acid solution, the solid-liquid ratio, and the reaction temperature and time, fluorine can be enriched on the material surface and at the grain boundaries without disrupting the overall crystal structure. Further staged calcination stabilizes the fluorination of the material surface and grain boundaries while preventing excessive diffusion of fluorine into oxygen sites.

[0031] A fluorine-containing acidic solution is used to mix and stir a nickel-based substrate cathode material. As an example, a certain concentration of fluorine-containing organic acidic solution is mixed and stirred with a certain amount of nickel-based substrate cathode material. The concentration of the fluorine-containing organic acidic solution is preferably 0.01–0.1 mol / L, and the solid-liquid ratio is preferably 1:(5–10). The mixing and stirring reaction temperature is preferably 0–60℃; the reaction time is preferably 30–200 min.

[0032] After the nickel-based cathode material is mixed and stirred to complete the reaction, partial delithiation occurs. After solid-liquid separation and drying, additional lithium salt is added for lithium mixing. As an example, the liquid phase is dried by evaporation in an oven, and the resulting solid is uniformly mixed with lithium salt, with a preferred lithium mixing ratio of 1:(0–0.6).

[0033] Sintering at a certain temperature maintains the material's good crystallinity, resulting in a nickel-based, fluorinated, and stable cathode material. As an example, the obtained dry powder is calcined in stages under an oxygen atmosphere. Initially, the preferred temperature is 400–550°C, and the holding time is 180–300 min. Then, the calcination temperature is increased and held at 700–900°C for 60–120 min.

[0034] As a detailed example of the preparation of nickel-based substrate cathode material with homogeneous fluorination stabilization treatment of surface and grain boundaries, the preparation process is as follows:

[0035] (1) Mix 10 mL of 0.01 mol / L tetrafluoroterephthalic acid aqueous solution with 2 g of LiNi 0.8 Co 0.15 Mn 0.05 The O2 material was uniformly mixed and stirred vigorously at 30°C for 30 minutes. The solid and liquid were then separated by filtration.

[0036] (2) The obtained filter cake was placed in a 60℃ oven and dried for 24 hours to become LiNi. 0.8 Co 0.15 Mn 0.05 O2 dry powder, mix the dry powder with LiOH·H2O at a ratio of 1:0.2.

[0037] (3) Place the mixed dry powder in a tube furnace, heat it to 450℃ and hold it for 240 minutes, then raise the temperature to 750℃ and hold it for 120 minutes, and finally cool it naturally to room temperature to obtain the final product.

[0038] In this invention, a fluorine-containing organic acidic solution is used to mix and stir a nickel-based layered cathode material, followed by solid-liquid separation and drying. Finally, sintering at a specific temperature maintains the material's good crystallinity, resulting in a nickel-based layered cathode material with stable surface and grain boundary fluorination. The main advantages are as follows: First, the process of this invention only includes mixing and stirring, solid-liquid separation and drying, and annealing. The process is simple, does not use complex machinery, and is inexpensive. Second, by precisely controlling the reaction parameters through the reaction of the fluorine-containing organic acidic solution with the alkaline nickel-based layered material, fluorine can be enriched on the material surface and at the primary particle interfaces (grain boundaries) without damaging the overall crystal structure of the material. Third, the first-stage annealing ensures the uniformity of lithium source distribution; combined with the second-stage annealing, a uniform and stable modified layer is formed on the surface and at the grain boundaries of the nickel-based layered material, while maintaining the integrity of the bulk layered structure. The nickel-based layered cathode material obtained by this invention possesses a stable surface and interface modified layer, which can effectively prevent side reactions between the nickel-based layered cathode material and the electrolyte, inhibit crack growth during cycling, and thus significantly improve cycle stability. The first-cycle capacity of the prepared nickel-based morphological cathode material reached 190 mAh g. -1 The capacity retention rate is above 80% after 500 cycles at 2.8-4.3V (test conditions: 2.8-4.3V, 0.2C, 25℃), preferably above 85%, more preferably above 90%, and most preferably above 95%.

[0039] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below.

[0040] Example 1

[0041] 10 mL of 0.1 mol / L aqueous solution of 2,3,5,6-tetrafluoroterephthalic acid was mixed with 2 g of LiNi 0.8 Co 0.15 Mn 0.05 O2 powder was uniformly mixed and reacted with stirring at 30℃ for 30 min. The mixture was then filtered to separate the solid and liquid phases and dried in a 60℃ forced-air drying oven for 24 h. The resulting dry powder was uniformly mixed with LiOH·H2O (molar ratio of nickel-based layered material to lithium source = 1:0.3), heated to 500℃ and held for 180 min under an oxygen atmosphere, then heated to 750℃ and held for 120 min before natural cooling to obtain LiNi with stable surface and grain boundary fluorination and a complete layered structure. 0.8Co 0.15 Mn 0.05 O2 material. A CR2032 coin cell was assembled using this material, and its electrochemical performance was tested. Specifically: active material: PVDF: acetylene black = 8:1:1 (mass ratio), then mixed and coated onto sheets, followed by vacuum drying at 90℃. The sheets were then cut into electrodes approximately 12mm in diameter and assembled in an argon-filled glove box (water and oxygen content ≤ 0.5ppm). The assembled batteries were allowed to stand for 12 hours before various electrochemical performance tests were performed.

[0042] Figure 1 The LiNi prepared in Example 1 0.8 Co 0.15 Mn 0.05 Powder diffraction pattern of O2 material, such as Figure 1 As shown, the prepared modified material exhibits typical layered structure characteristics. Figure 2 Figure a shows the microstructure of the fluorinated material in Example 1, where the primary particles are plate-like and have a flocculent, uniform coating layer on their surface. Figure 2 Image b is a low-magnification image, showing morphology of spherical secondary particles formed by the accumulation of primary particles. Figure 3 In Figure a, the microstructure of the calcined material in Example 1 is shown. The primary particle morphology is plate-like (particle size 200-400 nm), but the flocculent layer on the surface disappears, corresponding to the diffusion and fluorination reaction of the fluorinated layer at high temperature. (Low magnification...) Figure 3 In section b), the morphology is similar to that before calcination, consisting of spherical secondary particles (with a particle size of approximately 10 μm). Figure 4 The image shows a transmission electron microscope (TEM) image of the cathode material prepared in Example 1. It can be seen that the prepared cathode material has a layered structure with clear lattice fringes and an amorphous coating layer (approximately 5 nm thick) at the edge of the particles. Figure 5 This is an elemental distribution diagram of the cathode material prepared in Example 1. As can be seen from the diagram, the prepared cathode material exhibits a uniform distribution of elements. Fluorine, through this treatment method, can be converted into amorphous Li. 0.07 Ni 0.63 Co 0.18 Mn 0.12 F is uniformly distributed on the particles. Electrochemical performance was tested by assembling them into coin cells. Compared to the comparative example, the cathode material prepared in Example 1 showed no significant change in first-cycle capacity. Figure 6 When the test voltage is between 2.8-4.3V, the cycle capacity retention rate is significantly improved, and the capacity retention rate is 95.5% after 500 cycles at a 0.5C current. Figure 7 This demonstrates the effectiveness of the modification strategy.

[0043] Example 2

[0044] 10 mL of 0.5 mol / L aqueous solution of 2,3,5,6-tetrafluoroterephthalic acid was mixed with 2 g of LiNi 0.8 Co 0.15 Mn 0.05 O2 powder was uniformly mixed and stirred at 30°C for 10 min. The mixture was then filtered to separate the solid and liquid phases and dried in a 60°C forced-air drying oven. The resulting dry powder was uniformly mixed with LiOH·H2O (molar ratio of nickel-based layered material to lithium source = 1:0.5), heated to 500°C and held for 180 min under an oxygen atmosphere, then heated to 750°C and held for 120 min before natural cooling to obtain LiNi with stable surface and grain boundary fluorination and a complete layered structure. 0.8 Co 0.15 Mn 0.05 O2 material. A CR2032 coin cell was assembled using this material, and its electrochemical performance was tested. Specifically: active material: PVDF: acetylene black = 8:1:1 (mass ratio), then mixed and coated onto sheets, followed by vacuum drying at 90℃. The sheets were then cut into electrodes approximately 12mm in diameter and assembled in an argon-filled glove box (water and oxygen content ≤ 0.5ppm). The assembled batteries were allowed to stand for 12 hours before various electrochemical performance tests were performed. Figure 8 This is a scanning electron microscope (SEM) image of the cathode material prepared in Example 2, at low magnification. Figure 8 (b) The particles appear as spherical particles at high magnification. Figure 8 As can be seen in section a), it consists of spherical secondary particles assembled from primary particles, with a uniformly distributed flocculent coating layer on the surface. When the test voltage is between 2.8 and 4.3 V, the initial discharge capacity reaches 195 mAh g. -1 ( Figure 9 After 500 charge-discharge cycles, the capacity retention rate reaches approximately 85%.

[0045] Example 3

[0046] 10 mL of 0.1 mol / L aqueous solution of 2,3,5,6-tetrafluoroterephthalic acid was mixed with 2 g of LiNi 0.6 Co 0.2 Mn 0.2 O2 powder was uniformly mixed and stirred at 30°C for 30 min. The mixture was then filtered to separate the solid and liquid phases and dried in a 60°C forced-air drying oven. The resulting dry powder was uniformly mixed with LiOH·H2O (1:0.4), heated to 500°C and held for 180 min under an oxygen atmosphere, then heated to 800°C and held for 120 min before natural cooling to obtain LiNi with stable surface and grain boundary fluorination and a complete layered structure. 0.6 Co 0.2 Mn 0.2O2 material was used to assemble CR2032 coin cells, and their electrochemical performance was tested. Specifically, the active material, PVDF, and acetylene black were weighed according to a mass ratio of 8:1:1, mixed, coated, and then vacuum-dried at 90°C. The resulting electrodes were cut into approximately 12mm diameter sheets and assembled in an argon-filled glove box (water and oxygen content ≤0.5ppm). After 12 hours of resting, various electrochemical performance tests were performed. The initial discharge capacity reached 170 mAh g / g when the test voltage was between 2.8 and 4.3V. -1 After 500 charge-discharge cycles, the capacity retention rate reaches approximately 90%.

[0047] Example 4

[0048] 10 mL of 0.1 mol / L aqueous solution of 2,3,5,6-tetrafluoroterephthalic acid was mixed with 2 g of LiNi 0.5 Co 0.3 Mn 0.2 O2 powder was uniformly mixed and stirred at 30°C for 30 min. The mixture was then filtered to separate the solid and liquid phases and dried in a 60°C forced-air drying oven. The resulting dry powder was uniformly mixed with LiOH·H2O (1:0.5), heated to 500°C and held for 180 min under an oxygen atmosphere, then heated to 850°C and held for 120 min before natural cooling to obtain LiNi with stable surface and grain boundary fluorination and a complete layered structure. 0.5 Co 0.3 Mn 0.2 O2 material was used to assemble CR2032 coin cells, and their electrochemical performance was tested. Specifically, the active material, PVDF, and acetylene black were weighed according to a mass ratio of 8:1:1, mixed, coated, and then vacuum-dried at 90°C. The resulting electrodes were cut into approximately 12mm diameter sheets and assembled in an argon-filled glove box (water and oxygen content ≤0.5ppm). After 12 hours of resting, various electrochemical performance tests were performed. The initial discharge capacity reached 160 mAh g / g when the test voltage was between 2.8 and 4.3V. -1 After 500 charge-discharge cycles, the capacity retention rate reaches approximately 90%.

[0049] Example 5

[0050] 10 mL of 0.1 mol / L aqueous solution of 2,3,5,6-tetrafluoroterephthalic acid was mixed with 2 g of LiNi 1 / 3 Co 1 / 3Mn 1 / 3O2 powder was uniformly mixed and stirred at 30℃ for 30 min. The mixture was then filtered to separate the solid and liquid phases and dried in a 60℃ forced-air drying oven. The resulting dry powder was uniformly mixed with LiOH·H2O (1:0.5), heated to 500℃ in air and held for 180 min, then heated to 880℃ and held for 120 min before natural cooling to obtain LiNi with stable surface and grain boundary fluorination and a complete layered structure. 1 / 3 Co 1 / 3 Mn 1 / 3 O2 material was used to assemble CR2032 coin cells, and their electrochemical performance was tested. Specifically, the active material, PVDF, and acetylene black were weighed according to a mass ratio of 8:1:1, mixed, coated, and then vacuum-dried at 90°C. The resulting electrodes were cut into approximately 12mm diameter sheets and assembled in an argon-filled glove box (water and oxygen content ≤0.5ppm). After 12 hours of resting, various electrochemical performance tests were performed. The initial discharge capacity reached 150mAh / g when the test voltage was between 2.8-4.3V. -1 After 500 charge-discharge cycles, the capacity retention rate reaches approximately 90%.

[0051] Example 6

[0052] 10 mL of 0.1 mol / L aqueous solution of 2,3,5,6-tetrafluoroterephthalic acid was mixed with 2 g of LiNi 0.8 Co 0.1 Al 0.1 O2 powder was uniformly mixed and stirred at 30°C for 30 min. The mixture was then filtered to separate the solid and liquid phases and dried in a 60°C forced-air drying oven. The resulting dry powder was uniformly mixed with LiOH·H2O (1:0.3), heated to 500°C and held for 180 min under an oxygen atmosphere, then heated to 750°C and held for 120 min before natural cooling to obtain LiNi with stable surface and grain boundary fluorination and a complete layered structure. 0.8 Co 0.1 Al 0.1 O2 material was used to assemble CR2032 coin cells, and their electrochemical performance was tested. Specifically, the active material, PVDF, and acetylene black were weighed according to a mass ratio of 8:1:1, mixed, coated, and then vacuum-dried at 90°C. The resulting electrodes were cut into approximately 12mm diameter sheets and assembled in an argon-filled glove box (water and oxygen content ≤0.5ppm). After the assembled cells were allowed to stand for 12 hours, various electrochemical performance tests were performed. At a test voltage between 2.8-4.3V, after 500 charge-discharge cycles, the capacity retention reached approximately 85%.

[0053] Example 7

[0054] 10 mL of 0.1 mol / L aqueous solution of 2,3,5,6-tetrafluoroterephthalic acid was mixed with 2 g of LiNi 0.8 Co 0.15 Al 0.05 O2 powder was uniformly mixed and stirred at 30°C for 30 min. The mixture was then filtered to separate the solid and liquid phases and dried in a 60°C forced-air drying oven. The resulting dry powder was uniformly mixed with LiOH·H2O (1:0.3), heated to 500°C and held for 180 min under an oxygen atmosphere, then heated to 750°C and held for 120 min before natural cooling to obtain LiNi with stable surface and grain boundary fluorination and a complete layered structure. 0.8 Co 0.15 Al 0.05 O2 material was used to assemble CR2032 coin cells, and their electrochemical performance was tested. Specifically, the active material, PVDF, and acetylene black were weighed according to a mass ratio of 8:1:1, mixed, coated, and then vacuum-dried at 90°C. The resulting electrodes were cut into approximately 12mm diameter sheets and assembled in an argon-filled glove box (water and oxygen content ≤0.5ppm). After the assembled cells were allowed to stand for 12 hours, various electrochemical performance tests were performed. At a test voltage between 2.8-4.3V, after 500 charge-discharge cycles, the capacity retention reached approximately 85%.

[0055] Example 8

[0056] 10 mL of a 0.1 mol / L solution of 2,3,5,6-tetrafluoroterephthalic acid in water and ethanol (water:ethanol volume ratio 1:1) was mixed with 2 g of LiNi 0.8 Co 0.1 Mn 0.1 O2 powder was uniformly mixed and stirred at 30°C for 30 min. The mixture was then filtered to separate the solid and liquid phases and dried in a 60°C forced-air drying oven. The resulting dry powder was uniformly mixed with LiOH·H2O (1:0.1), heated to 500°C and held for 180 min under an oxygen atmosphere, then heated to 750°C and held for 120 min before natural cooling to obtain LiNi with stable surface and grain boundary fluorination and a complete layered structure. 0.8 Co 0.1 Mn 0.1 O2 material was used to assemble CR2032 coin cells, and their electrochemical performance was tested. Specifically, the active material, PVDF, and acetylene black were weighed according to a mass ratio of 8:1:1, mixed, coated, and then vacuum-dried at 90°C. The resulting electrodes were cut into approximately 12mm diameter sheets and assembled in an argon-filled glove box (oxygen content ≤ 0.5ppm). After 12 hours of resting, various electrochemical performance tests were performed. At a test voltage between 2.8-4.3V, after 500 charge-discharge cycles, the capacity retention reached approximately 85%.

[0057] Example 9

[0058] 10 mL of 0.1 mol / L fluorobenzoic acid aqueous solution was mixed with 2 g of LiNi 0.8 Co 0.1 Mn 0.1 O2 powder was uniformly mixed and stirred at 30°C for 60 min. The mixture was then filtered to separate the solid and liquid phases and dried in a 60°C forced-air drying oven. The resulting dry powder was uniformly mixed with LiOH·H2O (1:0.3), heated to 500°C and held for 180 min under an oxygen atmosphere, then heated to 750°C and held for 120 min before natural cooling to obtain LiNi with stable surface and grain boundary fluorination and a complete layered structure. 0.8 Co 0.1 Mn 0.1 O2 material was used to assemble CR2032 coin cells, and their electrochemical performance was tested. Specifically, the active material, PVDF, and acetylene black were weighed according to a mass ratio of 8:1:1, mixed, coated, and then vacuum-dried at 90°C. The resulting electrodes were cut into approximately 12mm diameter sheets and assembled in an argon-filled glove box (water and oxygen content ≤0.5ppm). After 12 hours of resting, various electrochemical performance tests were performed. At a test voltage between 2.8-4.3V, after 500 charge-discharge cycles, the capacity retention rate reached approximately 90%.

[0059] Example 10

[0060] 10 mL of 0.1 mol / L fluoropyridine carboxylic acid aqueous solution was mixed with 5 g of LiNi 0.8 Co 0.1 Mn 0.1 O2 powder was uniformly mixed and stirred at 30℃ for 30 min. The mixture was then filtered to separate the solid and liquid phases and dried in a 60℃ forced-air drying oven. The resulting dry powder was uniformly mixed with LiOH·H2O (1:0.3), heated to 500℃ and held for 180 min under an oxygen atmosphere, then heated to 780℃ and held for 60 min before natural cooling to obtain LiNi with stable surface and grain boundary fluorination and a complete layered structure. 0.8 Co 0.1 Mn 0.1 O2 materials.

[0061] Example 11

[0062] 10 mL of 0.1 mol / L p-fluorobenzoic acid aqueous solution was mixed with 2 g of LiNi 0.8 Co 0.1 Mn 0.1O2 powder was uniformly mixed and stirred at 50℃ for 10 min. The mixture was then filtered to separate the solid and liquid phases and dried in a 60℃ forced-air drying oven. The resulting dry powder was uniformly mixed with LiOH·H2O (1:0.3), heated to 500℃ and held for 180 min under an oxygen atmosphere, then heated to 780℃ and held for 120 min before natural cooling to obtain LiNi with stable surface and grain boundary fluorination and a complete layered structure. 0.8 Co 0.1 Mn 0.1 O2 materials.

[0063] Example 12

[0064] 10 mL of 0.1 mol / L aqueous solution of 2-nitro-3-fluorobenzoic acid was mixed with 2 g of LiNi 0.8 Co 0.1 Mn 0.1 O2 powder was uniformly mixed and stirred at 50℃ for 10 min. The mixture was then filtered to separate the solid and liquid phases and dried in a 60℃ forced-air drying oven. The resulting dry powder was uniformly mixed with LiOH·H2O (1:0.3), heated to 500℃ and held for 180 min under an oxygen atmosphere, then heated to 780℃ and held for 120 min before natural cooling to obtain LiNi with stable surface and grain boundary fluorination and a complete layered structure. 0.8 Co 0.1 Mn 0.1 O2 materials.

[0065] Example 13

[0066] The surface and grain boundary treatment method of the nickel-based solid cathode material for fluorinated stabilized lithium-ion batteries in Example 13 is the same as in Example 1, except that the ratio of nickel-based cathode material to lithium source is 1:0.1.

[0067] Example 14

[0068] The surface and grain boundary treatment method of the nickel-based solid cathode material for fluorinated stabilized lithium-ion batteries in Example 14 is the same as in Example 1, except that the ratio of nickel-based cathode material to lithium source is 1:0.5.

[0069] Example 15

[0070] The surface and grain boundary treatment method of the nickel-based solid cathode material for fluorinated stabilized lithium-ion batteries in Example 15 is the same as in Example 1, except that: the ratio of nickel-based cathode material to lithium source is 1:0, that is, no lithium source is added.

[0071] Example 16

[0072] The surface and grain boundary treatment method of the nickel-based basal cathode material for fluorinated stabilized lithium-ion batteries in Example 16 is the same as in Example 1, except that the lithium source is lithium acetate.

[0073] Example 17

[0074] The surface and grain boundary treatment method of the nickel-based basal cathode material for fluorinated stabilized lithium-ion batteries in Example 17 is the same as in Example 1, except that the lithium source is lithium nitrate.

[0075] Example 18

[0076] The surface and grain boundary treatment method of the nickel-based basal cathode material for fluorinated stabilized lithium-ion batteries in Example 18 is the same as in Example 1, except that the calcination parameters are 500℃ / 180min and 780℃ / 120min.

[0077] Example 19

[0078] The surface and grain boundary treatment method of the nickel-based basal cathode material for fluorinated stabilized lithium-ion batteries in Example 19 is the same as that in Example 1, except that the calcination parameters are 500℃ / 180min and 800℃ / 120min.

[0079] Example 20

[0080] The surface and grain boundary treatment method of the nickel-based basal cathode material for fluorinated stabilized lithium-ion batteries in Example 19 is the same as that in Example 1, except that the calcination parameters are 450℃ / 300min and 750℃ / 120min.

[0081] Example 21

[0082] The surface and grain boundary treatment method of the nickel-based basal cathode material for fluorinated stabilized lithium-ion batteries in Example 19 is the same as that in Example 1, except that the calcination parameters are 550℃ / 180min and 750℃ / 120min.

[0083] Comparative Example 1

[0084] Using commercially available unmodified cathode material LiNi 0.8 Co 0.15 Mn 0.05 O2 was used as a control sample. A CR2032 coin cell was assembled using this material, and its electrochemical performance was tested. Specifically: Active material:PVDF:acetylene black = 8:1:1 (mass ratio) was weighed, mixed, coated, and then vacuum-dried at 90℃. The coated material was then cut into electrode sheets with a diameter of approximately 12mm and assembled in an argon-filled glove box (water and oxygen content ≤0.5ppm). The assembled cells were allowed to stand for 12 hours before various electrochemical performance tests were performed. For example... Figure 6 It can be seen that when the test voltage is between 2.8 and 4.3 V, the initial discharge capacity of the comparative material is 196 mAh g. -1Compared to the cathode material prepared in Example 1, the cycle stability is poor. Figure 7 At 0.5C current, the capacity retention rate after 300 cycles is only 76%.

[0085] Comparative Example 2

[0086] In Comparative Example 2, the surface and grain boundary treatment method of the nickel-based basal cathode material for fluorinated stabilized lithium-ion batteries is the same as in Example 1, except that the calcination parameters are only 750℃ / 120min.

[0087] Table 1 shows the performance parameters of the modified nickel-based basal cathode material prepared in this invention:

[0088]

[0089]

[0090]

[0091] Table 1 shows the capacity retention rate at 0.5C and 500 laps, with Comparative Example 1 showing the capacity retention rate after 400 laps.

[0092] The above description is merely a preferred embodiment of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. For those skilled in the art, improvements and modifications obtained without departing from the inventive concept should also be considered within the scope of protection of the present invention.

Claims

1. A method for modifying the surface and grain boundaries of a nickel-based substrate cathode material for fluorinated stabilized lithium-ion batteries, characterized in that, A fluorine-containing organic acid solution was used to micro-etch a spherical secondary particle nickel-based crystalline material formed by the agglomeration of primary particles with grain boundaries between them. After solid-liquid separation and drying, the material was calcined in air or oxygen at two temperature stages to obtain a nickel-based crystalline cathode material with a stable amorphous fluoride modified layer formed on the surface of the secondary particles and at the grain boundaries between the primary particles, and with a complete bulk layered structure. The primary particles have a diameter of 200–400 nm, and the total diameter of the spherical secondary particles is 8–15 μm. The fluorine-containing organic acid is at least one of fluorobenzoic acid and fluoropyridinecarboxylic acid, the solvent of the fluorine-containing organic acid solution is a mixture of deionized water and ethanol, and the concentration of the fluorine-containing organic acid solution is 0.01 to 1 mol / L; The solid-liquid ratio of the nickel-based substrate to the fluorine-containing organic acid solution is 1 g: (1-20) mL; the micro-etching temperature is 0-95℃ and the time is 1-300 min; A lithium source is added after drying and before calcination, wherein the molar ratio of the dried nickel-based crystalline material to the lithium source is 1:(0 to 0.8). The two-stage calcination includes: a low-temperature calcination at 300–600°C for 60–360 min; and a high-temperature calcination at 700–1000°C for 10–240 min.

2. The method for modifying the surface and grain boundaries of the nickel-based substrate cathode material for fluorinated stabilized lithium-ion batteries according to claim 1, characterized in that, The chemical composition of the nickel-based cathode material is LiNi. x M 1-x O2, where 0.3≤x≤1, and M is selected from at least one of Co, Mn, Al, Mg, Fe, Zr, and Mo.

3. The method for modifying the surface and grain boundaries of the nickel-based substrate cathode material for fluorinated stabilized lithium-ion batteries according to claim 1, characterized in that, The micro-etching is carried out under stirring conditions at 0–60°C for a reaction time not exceeding 200 min.

4. The method for modifying the surface and grain boundaries of the nickel-based substrate cathode material for fluorinated stabilized lithium-ion batteries according to claim 1, characterized in that, The solid-liquid separation method is at least one of natural evaporation, centrifugal separation, and vacuum filtration; the drying method is at least one of oven drying and freeze drying.

5. The method for modifying the surface and grain boundaries of the nickel-based substrate cathode material for fluorinated stabilized lithium-ion batteries according to claim 1, characterized in that, The lithium source is at least one of lithium hydroxide, lithium acetate, and lithium nitrate.

6. A modified nickel-based crystalline cathode material prepared by the modification method according to claim 1, characterized in that, The modified nickel-based cathode material comprises: a nickel-based cathode material matrix, and an amorphous fluoride modification layer distributed on the surface of the nickel-based cathode material matrix and at the grain boundaries between primary particles of the nickel-based cathode material matrix; the chemical composition of the amorphous fluoride modification layer is AF. y Where 0 < y < 4, A is selected from at least one of Li, Co, Mn, Al, Mg, Fe, Zr, and Mo, and the thickness does not exceed 10 nm.

Images