Preparation method of alkali-treated graphite negative electrode material for lithium ion battery and battery

Abstract

According to the preparation method, graphite is subjected to alkali treatment, a lithium hydroxide solution is adopted during alkali treatment, and then high-temperature etching treatment is carried out, so that on one hand, a hole structure is constructed on the surface of the graphite, an additional channel is provided for transmission of lithium ions, and on the other hand, the surface of the graphite is coated with the lithium hydroxide solution; the performance of the graphite negative electrode under the rapid charging condition is remarkably improved, the graphite negative electrode can better meet the requirement of modern electronic equipment for rapid charging, powerful technical support is provided for performance optimization of a lithium ion battery, on the one hand, the graphite is treated with the lithium hydroxide solution, a-C-O-Li functional group can be generated on the surface of the graphite, and the performance of the graphite negative electrode is improved. And the process can effectively reduce the subsequent lithium salt decomposition degree, so that the initial coulombic efficiency of the material is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery materials technology, and in particular to a method for preparing alkali-treated graphite anode materials for lithium-ion batteries and a battery thereof. Background Technology

[0002] With the continuous advancement of technology, lithium-ion batteries, as a highly efficient energy storage technology, have been widely used in portable electronic devices and electric vehicles. However, with the increasing demand for fast charging and high energy-power density, traditional lithium-ion battery technology faces many challenges. Especially in fast charging applications, graphite, as one of the main anode materials for lithium-ion batteries, has become a research hotspot due to its abundant reserves, low cost, stable electrochemical performance, and high theoretical specific capacity (372 mAh / g).

[0003] While the application of graphite anodes in lithium-ion batteries is relatively mature, they have significant limitations in fast-charging applications. Typically, lithium ions can only intercalate through narrow interlayers of graphite, resulting in a longer transport path and slower diffusion rate. This not only limits the battery's fast-charging performance but can also lead to the formation of lithium dendrites, reducing the battery's cycle stability and potentially causing safety issues such as internal short circuits, overheating, fires, or even explosions.

[0004] Therefore, providing additional channels for lithium ions will help shorten their transport path and accelerate their diffusion rate, thereby significantly improving the battery's fast-charging performance. Simultaneously, these additional channels can effectively disperse the insertion and extraction points of lithium ions, reducing the risk of lithium dendrite formation and enhancing the battery's cycle stability and safety.

[0005] Furthermore, alkaline substances can promote oxidation reactions on the graphite surface, leading to the formation of oxygen-containing functional groups. These oxygen-containing functional groups preferentially interact with lithium ions, thereby forming a Li₂CO₃-rich SEI film. Li₂CO₃ not only has high electrical conductivity but also good mechanical stability. Therefore, the optimized interface film can also enable lithium ions to be inserted and extracted more uniformly during high-rate charge and discharge processes, further improving the overall performance and lifespan of the battery.

[0006] In existing literature, when preparing graphite anode materials for lithium-ion batteries, alkaline solutions such as potassium hydroxide are used to etch the graphite materials. However, this method has a technical problem of low initial coulombic efficiency when applied to lithium-ion batteries. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for preparing alkaline-treated graphite anode material for lithium-ion batteries and a battery that improves the first coulombic efficiency and capacity retention of the material.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A method for preparing an alkali-treated graphite anode material for lithium-ion batteries includes the following steps: S1, graphite powder and alkaline solution are mixed, stirred evenly, filtered and dried to obtain precipitate, wherein the alkaline solution is lithium hydroxide solution; S2, place the precipitate at 400℃ Etching process at 800℃ under a protective atmosphere 1 The process takes 12 hours to form pores on the graphite surface and pre-lithiate the graphite. After washing and drying, the alkali-treated graphite anode material is obtained.

[0009] As a further improvement to the above technical solution: In step S1, the concentration of the lithium hydroxide solution is 7-10 mol / L.

[0010] In step S1, the stirring temperature is 40~80℃, and the stirring time is 3 minutes. 12h.

[0011] In step S1, the drying temperature is 60-120℃ and the time is 6-24h.

[0012] In step S2, the pores are nanoscale pores.

[0013] In step S2, the size of the hole is 0.01-2 μm.

[0014] In step S2, the washing is repeated multiple times until the pH of the washing solution is neutral.

[0015] In step S2, the drying temperature is 60-120℃ and the time is 6-24h.

[0016] The drying temperature in steps S1 and S2 is 60-120 ℃. This is because if the drying temperature of graphite in air is too high, above 150 ℃, it begins to slowly oxidize at the edges, increasing the specific surface area and the number of oxygen-containing functional groups (-OH, -COOH). Above 200 ℃, the oxidation rate increases with increasing temperature, resulting in significant mass loss and decreased electrical conductivity. Therefore, even with just drying, prolonged exposure to air at excessively high temperatures will over-oxidize the graphite.

[0017] An alkali-treated graphite anode material for lithium-ion batteries is prepared according to the aforementioned preparation method, and the surface of the alkali-treated graphite anode material for lithium-ion batteries has nanoscale pores.

[0018] A lithium-ion battery includes a lithium-ion battery-grade graphite anode material prepared by the aforementioned method and treated with an alkali. Compared with the prior art, the advantages of this invention are: This invention discloses a method for preparing alkali-treated graphite anode material for lithium-ion batteries. The method involves alkali-treating graphite with a lithium hydroxide solution followed by high-temperature etching. This process creates a porous structure on the graphite surface, providing additional channels for lithium-ion transport and significantly improving the performance of the graphite anode under fast-charging conditions. This allows the anode to better meet the fast-charging requirements of modern electronic devices, providing strong technical support for optimizing the performance of lithium-ion batteries. Furthermore, the lithium hydroxide solution treatment generates -CO-Li functional groups on the graphite surface, achieving pre-lithiation of the graphite. This process effectively reduces the degree of subsequent lithium salt decomposition, thereby significantly improving the material's initial coulombic efficiency.

[0019] The lithium-ion battery of the present invention includes a method for preparing an alkali-treated graphite anode material for lithium-ion batteries, which has the aforementioned advantages, including higher energy density, better cycle stability and faster charge and discharge performance, and can meet the demand for high-performance lithium-ion batteries in modern electronic devices and electric vehicles. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of alkali treatment of graphite anodes to form a porous structure on their surface.

[0021] Figure 2 This is a SEM image of the alkali-treated graphite anode material from Example 1.

[0022] Figure 3 The graphite half-cell assembled in Example 1 is shown as the first charge-discharge curve at 0.1C.

[0023] Figure 4 The electrochemical performance of the graphite half-cell assembled in Example 1 and Comparative Example 2 at 8C is shown.

[0024] Figure 5 This is a SEM image of the alkali-treated graphite anode material in Comparative Example 2. Detailed Implementation

[0025] The present invention will be further described in detail below. Unless otherwise specified, the instruments or materials used in the present invention are commercially available.

[0026] Example 1: like Figure 1 As shown, a method for preparing an alkali-treated graphite anode material according to this embodiment includes the following steps: A1. Weigh 5 grams of graphite and mix it with 100 ml of 7 M LiOH solution. Place the mixture in a constant temperature environment of 60°C and stir continuously for 12 hours. Filter to separate the precipitate and dry it in a vacuum oven at 80°C for 12 hours.

[0027] A2. The dried powder was transferred to a tube furnace and heated to 800°C at a rate of 5°C / min under a nitrogen atmosphere, and held for 1 hour for etching. After etching, the powder was repeatedly washed with deionized water until the pH of the solution reached neutral. The washed product was then dried in a vacuum oven at 80°C for 12 hours to obtain the target product.

[0028] The SEM image of the alkali-treated graphite anode material in this embodiment is shown below. Figure 2 As shown, SEM observation revealed that uniformly distributed micropores formed on the graphite surface, with an intact overall structure and good pore connectivity (e.g., Figure 2 ).

[0029] The application of an alkali-treated graphite anode material in a lithium-ion battery according to this embodiment includes the following steps: under anhydrous and oxygen-free conditions, lithium hexafluorophosphate (LiPF6) is dissolved as a lithium salt in a mixed solvent of ethylene carbonate (EC) and dimethyl carbonate (DMC) (v(EC):v(DMC)=3:7) to obtain an electrolyte (LB010) with a LiPF6 concentration of 1 M. Using LB010 as the electrolyte, the alkali-treated graphite anode material (the alkali-treated graphite anode material is loaded on the current collector) of this embodiment is used as the anode to assemble a graphite half-cell.

[0030] Tests showed that the graphite half-cell in this embodiment achieved an initial charge-discharge efficiency of 89.2% at 0.1C (e.g., ...). Figure 3 After 300 cycles at 1C, the capacity retention is 85%; at 8C, the capacity retention is 81% at 0.1C (e.g., Figure 4 ).

[0031] Example 2: This embodiment provides a method for preparing an alkali-treated graphite anode material, comprising the following steps: A1. Weigh 5 grams of graphite and mix it with 100 ml of 8 M LiOH solution. Place the mixture in a constant temperature environment of 60°C and stir continuously for 12 hours. Filter to separate the precipitate and dry it in a vacuum oven at 80°C for 12 hours.

[0032] A2. The dried powder was transferred to a tube furnace and heated to 800°C at a rate of 5°C / min under a nitrogen atmosphere, and held for 1 hour for etching. After etching, the powder was repeatedly washed with deionized water until the pH of the solution reached neutral. The washed product was then dried in a vacuum oven at 80°C for 12 hours to obtain the target product.

[0033] The application of an alkali-treated graphite anode material in a lithium-ion battery according to this embodiment includes the following steps: Under anhydrous and oxygen-free conditions, using LB010 from Example 1 as the electrolyte and the alkali-treated graphite anode material of this embodiment as the anode, assembling a graphite half-cell. Tests showed that the graphite half-cell in this embodiment achieved an initial charge-discharge efficiency of 85.4% at 0.1 C, and retained 86% of its capacity after 300 cycles at 1C. The capacity retention at 8C was 83% at 0.1C.

[0034] Example 3: This embodiment provides a method for preparing an alkali-treated graphite anode material, comprising the following steps: A1. Weigh 5 grams of graphite and mix it with 100 ml of a 7 M LiOH solution. Place the mixture in a constant temperature environment at 60°C and stir continuously for 12 hours. Filter to separate the precipitate and dry it in a vacuum oven at 80°C for 12 hours.

[0035] A2. The dried powder was transferred to a tube furnace and heated to 600°C at a rate of 5°C / min under a nitrogen atmosphere, and held for 1 hour for etching. After etching, the powder was repeatedly washed with deionized water until the pH of the solution reached neutral. The washed product was then dried in a vacuum oven at 80°C for 12 hours to obtain the target product.

[0036] The application of an alkali-treated graphite anode material in a lithium-ion battery according to this embodiment includes the following steps: Under anhydrous and oxygen-free conditions, using LB010 from Example 1 as the electrolyte and the alkali-treated graphite anode material of this embodiment as the anode, assembling a graphite half-cell. Tests showed that the graphite half-cell in this embodiment had an initial charge-discharge efficiency of 86.8% at 0.1 C, and a capacity retention of 77% after 300 cycles at 1C. The capacity retention at 8C was 75% at 0.1C.

[0037] Example 4: This embodiment provides a method for preparing an alkali-treated graphite anode material, comprising the following steps: A1. Weigh 5 grams of graphite and mix it with 100 ml of a 7 M LiOH solution. Place the mixture in a constant temperature environment at 60°C and stir continuously for 12 hours. Filter to separate the precipitate and dry it in a vacuum oven at 80°C for 12 hours.

[0038] A2. The dried powder was transferred to a tube furnace and heated to 600°C at a rate of 5°C / min under a nitrogen atmosphere, and held for 3 hours for etching. After etching, the powder was repeatedly washed with deionized water until the pH of the solution reached neutral. The washed product was then dried in a vacuum oven at 80°C for 12 hours to obtain the target product.

[0039] The application of an alkali-treated graphite anode material in a lithium-ion battery according to this embodiment includes the following steps: Under anhydrous and oxygen-free conditions, using LB010 from Example 1 as the electrolyte and the alkali-treated graphite anode material of this embodiment as the anode, assembling a graphite half-cell. Tests showed that the graphite half-cell in this embodiment had an initial charge-discharge efficiency of 85.9% at 0.1 C, and a capacity retention of 79% after 300 cycles at 1C. The capacity retention at 8C was 74% at 0.1C.

[0040] Comparative Example 1: This comparative example describes a method for preparing an alkali-treated graphite anode material, comprising the following steps: A1. Weigh 5 grams of graphite and mix it with 100 ml of 8 M KOH solution. Place the mixture in a constant temperature environment of 60°C and stir continuously for 12 hours. Filter to separate the precipitate and dry it in a vacuum oven at 80°C for 12 hours.

[0041] A2. The dried powder was transferred to a tube furnace and heated to 800°C at a rate of 5°C / min under a nitrogen atmosphere, and held for 1 hour for etching. After etching, the powder was repeatedly washed with deionized water until the pH of the solution reached neutral. The washed product was then dried in a vacuum oven at 80°C for 12 hours to obtain the target product.

[0042] The application of an alkali-treated graphite anode material in a lithium-ion battery according to this comparative example includes the following steps: Under anhydrous and oxygen-free conditions, using LB010 from Example 1 as the electrolyte and the alkali-treated graphite anode material of this comparative example as the anode, assembling a graphite half-cell. Testing showed that the graphite half-cell in this comparative example achieved an initial charge-discharge efficiency of 82.5% at 0.1 C, and after 300 cycles at 1 C, retained 68% of its capacity, with a 28% capacity retention at 0.1 C at 4 C. SEM observation revealed significant corrosion marks on the graphite surface, with some areas exhibiting a loose structure. While increasing the KOH concentration can significantly increase the specific surface area and porosity, excessively high concentrations can damage the graphite surface structure, reducing its mechanical strength and cycle stability.

[0043] Comparative Example 2: This comparative example describes a method for preparing an alkali-treated graphite anode material, comprising the following steps: A1. Weigh 5 grams of graphite and mix it with 100 ml of a 7 M LiOH solution. Place the mixture in a constant temperature environment at 60°C and stir continuously for 12 hours. Filter to separate the precipitate and dry it in a vacuum oven at 80°C for 12 hours.

[0044] A2. The dried powder was transferred to a tube furnace and heated to 800°C at a rate of 5°C / min under a nitrogen atmosphere, and held for 0.5 hours for etching. After etching, the powder was repeatedly washed with deionized water until the pH of the solution reached neutral. The washed product was then dried in a vacuum oven at 80°C for 12 hours to obtain the target product.

[0045] The application of an alkali-treated graphite anode material in a lithium-ion battery according to this comparative example includes the following steps: under anhydrous and oxygen-free conditions, using LB010 from Example 1 as the electrolyte and the alkali-treated graphite anode material of this comparative example as the anode, a graphite half-cell is assembled.

[0046] Tests showed that the graphite half-cell in this comparative example achieved an initial charge-discharge efficiency of 81.9% at 0.1 C, and retained 75% of its capacity after 300 cycles at 1C. The capacity retention at 8C was 62% at 0.1C (e.g., ...). Figure 4 (As shown).

[0047] The SEM images of the alkali-treated graphite anode material in this comparative example are shown below. Figure 5 As shown, the graphite surface has few and uneven pores, with some areas lacking a clear pore structure. Shortening the etching time leads to insufficient pore structure formation. This directly affects lithium-ion diffusion efficiency and fast-charging performance, while also reducing cycle stability.

[0048] Comparative Example 3: This comparative example describes a method for preparing an alkali-treated graphite anode material, comprising the following steps: A1. Weigh 5 grams of graphite and mix it with 100 ml of a 7 M LiOH solution. Place the mixture in a constant temperature environment of 60°C and stir continuously for 12 hours. Filter to separate the precipitate and dry it in a vacuum oven at 80°C for 12 hours.

[0049] A2. The dried powder was transferred to a tube furnace and heated to 300°C at a rate of 5°C / min under a nitrogen atmosphere, and held for 1 hour for etching. After etching, the powder was repeatedly washed with deionized water until the pH of the solution reached neutral. The washed product was then dried in a vacuum oven at 80°C for 12 hours to obtain the target product.

[0050] The application of an alkali-treated graphite anode material in a lithium-ion battery according to this comparative example includes the following steps: Under anhydrous and oxygen-free conditions, using LB010 from Example 1 as the electrolyte and the alkali-treated graphite anode material of this comparative example as the anode, assembling a graphite half-cell. Testing showed that the graphite half-cell in this comparative example achieved an initial charge-discharge efficiency of 83.2% at 0.1 C, and retained 62% of its capacity after 300 cycles at 1 C. The capacity retention at 8 C was 55% at 0.1 C. SEM observation revealed very few and unevenly distributed pores on the graphite surface, with some areas showing almost no pore structure. This indicates that lowering the etching temperature to 300℃ significantly reduced fast-charging performance and also noticeably worsened cycle stability. This suggests that an etching temperature of 500℃ is insufficient to form an effective pore structure, which is detrimental to improving the electrochemical performance of graphite.

[0051] Table 1. Battery capacity and capacity retention under different conditions in Examples 1-4 and Comparative Examples 1-3.

[0052] Treating graphite with an alkaline LiOH solution generates -CO-Li functional groups on its surface, achieving pre-lithiation of the graphite. This process effectively reduces the degree of subsequent lithium salt decomposition, thereby significantly improving the material's initial coulombic efficiency. Simultaneously, pre-lithiation treatment helps improve the battery's capacity retention.

[0053] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the scope of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the present invention, should fall within the protection scope of the present invention.

Claims

1. A method for preparing an alkali-treated graphite anode material for lithium ion batteries, characterized by: The method comprises the following steps: S1, mixing graphite powder and an alkaline solution, stirring uniformly, filtering and drying to obtain a precipitate, wherein the alkaline solution is a lithium hydroxide solution; S2, the precipitate is placed at 400°C 800°C temperature, etching treatment 1 under the protection of a protective atmosphere 12h, to form holes on the surface of the graphite and pre-lithiate the graphite, and after washing and drying, an alkali-treated graphite negative electrode material is obtained.

2. The production method according to claim 1, characterized by: In step S1, the concentration of the lithium hydroxide solution is 7-10 mol / L.

3. The method of claim 1, wherein: In step S1, the temperature of the stirring is 40-80°C, and the stirring time is 3 12h.

4. The method of claim 1, wherein: In step S1, the drying temperature is 60-120°C, and the drying time is 6-24h.

5. The method of claim 1, wherein: In step S2, the holes are nanoscale holes.

6. The method of claim 5, wherein: In step S2, the size of the holes is 0.01-2 μm.

7. The method of claim 1, wherein: In step S2, the washing is performed for multiple times until the pH value of the washing liquid is neutral.

8. The method of claim 1, wherein: In step S2, the drying temperature is 60-120°C, and the drying time is 6-24h.

9. An alkali treated graphite anode material for lithium ion batteries, characterized by: The alkali-treated graphite negative electrode material for lithium ion batteries is prepared according to the preparation method in any one of claims 1-8, and the alkali-treated graphite negative electrode material has nanoscale holes on the surface.

10. A lithium-ion battery, characterized by: The alkali-treated graphite negative electrode material for lithium ion batteries is prepared according to the preparation method in any one of claims 1-8.

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