Lithium ion battery negative electrode material, preparation method thereof and lithium ion battery

Abstract

The application relates to a lithium ion battery negative electrode material and a preparation method thereof and a lithium ion battery. The negative electrode material is a core-shell structure, the negative electrode material is prepared by mixing silicon monoxide and lithium alloy Li x M, the shell comprises a plurality of nano M particles, and the material of the core comprises M and Li x MO y . The method is to heat treat silicon monoxide and lithium alloy, such as lithium-silicon alloy, after mixing, the liquefied lithium alloy is wrapped on the surface of the silicon monoxide, lithium in the lithium alloy reacts with the silicon monoxide to form a core-shell structure with M and Li x MO y in the inside and the residual element M in the lithium alloy in the outside. The method is not only simple in operation, but also can effectively prevent the internal pre-lithiated silicon monoxide component from contacting the air environment, improve the stability of the material, and the residual element M shell can also participate in the electrochemical cycle process as a battery active substance, thereby improving the capacity and the first coulomb efficiency of the silicon monoxide.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, and specifically relates to a silicon-oxygen anode material for lithium-ion batteries, its preparation method, and lithium-ion batteries. Background Technology

[0002] Lithium-ion batteries, as a type of rechargeable battery, possess high specific energy, long cycle life, and a wide operating temperature range, making them widely used in energy storage, new energy vehicles, and portable electronic devices. Silicon suboxide, as a negative electrode material for lithium-ion rechargeable batteries, offers lower cost, better cycle stability, higher discharge specific capacity, and a lower charge / discharge plateau, making it considered the preferred next-generation lithium-ion battery negative electrode material.

[0003] However, during the first charge of a lithium-ion battery, the silicon dioxide in the silicon suboxide reacts with lithium ions to form electrochemically inert Li₂SiO₃ and Li₄SiO₄, significantly consuming lithium ions and causing irreversible lithium loss, which in turn leads to performance degradation of the lithium-ion battery. The main solution is to pre-introduce additional lithium ions into the battery to compensate for this lithium loss (pre-lithiation). Existing pre-lithiation technologies use highly chemically active lithium metal powder or thin films, applied by spraying and rolling, to contact the silicon suboxide electrode. The lithium metal reacts with the silicon suboxide to form lithium silicate and lithium-silicon alloys for pre-lithiation. These methods not only have high equipment requirements and significant safety risks, but the resulting lithium-silicon alloys are also highly chemically reactive, easily reacting with air and water in the environment, affecting battery performance. Therefore, there is an urgent need to develop a pre-lithiation method that is simple to operate and produces stable pre-lithiation products. Summary of the Invention

[0004] This invention provides a lithium-ion battery anode material that is easy to operate and produces stable pre-lithiation products, along with its preparation method and applications, in order to solve the aforementioned technical problems.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A lithium-ion battery anode material, wherein the anode material has a core-shell structure, and the anode material is a lithium alloy of silicon suboxide and lithium. x The shell, obtained by heat treatment after mixing M, comprises several nano-sized M particles, and the core material comprises M and Li. x MO y .

[0007] Preferably, the lithium alloy Li x The M in M ​​represents silicon, tin, germanium, antimony, or magnesium.

[0008] The method for preparing the negative electrode material includes the following steps:

[0009] The silica powder and lithium alloy powder are stirred and mixed in a mixer to obtain a uniform mixed powder A;

[0010] The mixed powder A is heat-treated in an inert atmosphere at 600℃-1800℃ to obtain the negative electrode material.

[0011] Preferably, the lithium alloy is one or a mixture of two or more of the following: lithium-silicon alloy, lithium-tin alloy, lithium-germanium alloy, lithium-antimony alloy, or lithium-magnesium alloy.

[0012] Preferably, the mass ratio of the silicon suboxide powder to the lithium alloy powder is 99:1-60:40.

[0013] Preferably, the mixed powder A is heat-treated in an inert atmosphere at 600°C-1200°C for 0.1-8 hours.

[0014] Preferably, the inert atmosphere is one or a mixture of argon or helium.

[0015] Preferably, the inert atmosphere is vented at a rate of 50-200 mL / min.

[0016] Preferably, the particle size d of the silica powder is... 50 The range is 0.1-20 μm.

[0017] A lithium-ion battery comprising the aforementioned negative electrode material.

[0018] The reaction principle of this invention is as follows: First, lithium alloy powder is mixed with silicon suboxide. Then, the mixed sample is heated to a specified temperature in an inert atmosphere at normal pressure. Utilizing the property that lithium alloy powder, such as lithium-silicon alloy, liquefies at high temperatures, the liquid lithium-silicon alloy coats the surface of the silicon suboxide. Simultaneously, the liquid lithium-silicon alloy reacts with the internal silicon suboxide to form a core-shell structured pre-lithiation composite material. This process achieves uniform lithiation while introducing an additional silicon coating layer, which not only prevents the internal pre-lithiation products from directly contacting the environment, improving stability, but also allows the material to participate in battery charging and discharging, increasing the discharge specific capacity. The reaction equation is as follows:

[0019]

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] This method for preparing pre-lithiated silicon suboxide anode material uses silicon suboxide as the battery anode material. After mixing with a lithium-silicon alloy and then heat-treating, the amorphous silicon suboxide in the silicon suboxide is consumed in advance and fully reacted to generate a stable lithium silicate phase, forming a Si / Si / Li structure. x SiO yDue to the pre-formation of an irreversible stable phase, the active lithium effectively extracts and inserts during the first charge-discharge cycle of the half-cell, resulting in a high initial coulombic efficiency for the anode material. At the same time, at high temperatures, a silicon alloy coats the material surface to form a coating layer. This coating layer not only acts as an active material, providing additional capacity, but also isolates the internal lithium silicate from direct contact with the outside environment, improving the stability of the material. Attached Figure Description

[0022] Figure 1 SiO x Flowchart of the reaction between lithium and silicon alloys;

[0023] Figure 2 For (a) commercial SiO x (b) SEM images of the product of Example 2;

[0024] Figure 3 For (a, b) commercial SiO x TEM images of the products of Example 2 (c, d);

[0025] Figure 4 For commercial SiO x XRD patterns of the product from Example 2;

[0026] Figure 5 The first charge-discharge curves of the final product prepared in Example 2 and the initial commercial silicon suboxide are shown.

[0027] Figure 6 The XRD pattern (a) and the first charge-discharge curve (b) of the final product B-2 prepared in Example 3 are shown.

[0028] Figure 7 The XRD pattern (a) and the first charge-discharge curve (b) of the final product B-3 prepared in Example 4 are shown.

[0029] Figure 8 The XRD pattern (a) and the first charge-discharge curve (b) of the final product B-4 prepared in Example 5 are shown.

[0030] Figure 9 The XRD pattern of the final product C-1 prepared in this comparative example is given. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0032] Example 1

[0033] This invention provides a negative electrode material, wherein the negative electrode material is a lithium alloy of silicon suboxide and lithium Li. x The anode material is obtained by heat treatment after mixing M. It has a core-shell structure, where the shell comprises several nano-sized M particles, and the core material includes M and Li. x MO y The lithium alloy Li x In the case of M, M represents silicon, tin, germanium, antimony, or magnesium. For example... Figure 1 As shown, taking lithium-silicon alloy as an example, its shell consists of several nano-sized silicon particles, and the core material includes Si and Li. x SiO y .

[0034] Example 2

[0035] This embodiment provides a method for preparing the negative electrode material, including the following steps:

[0036] Step (1): Take a certain amount of commercial silicon suboxide powder and lithium silicon alloy powder, put them into a mixer in a mass ratio of 80:20, the mixer speed is 200 rpm, the mixing time is 2 hours, and the silicon suboxide and lithium silicon alloy are mixed to obtain powder A with uniform composition.

[0037] Step (2): Take 10g of powder A obtained in step (1) and place it in a stainless steel crucible for heat treatment. The atmosphere is high-purity argon gas. The duration is the entire heating process and the entire cooling process. The heating rate is 5°C / min. The heat treatment temperature is 800°C. The holding time is 2 hours. The calcination pressure is atmospheric pressure. After calcination, the final product B-1, namely the pre-lithiated silicon suboxide anode material, can be obtained.

[0038] In the fabrication of lithium-ion button batteries, the above-prepared negative electrode material is mixed with PAA (binder) and acetylene (conductive agent) in a mass ratio of 8:1:1. A liquid electrode slurry is prepared using DMF as a solvent and coated onto the surface of copper foil. Then, a lithium metal sheet is used as the counter electrode, EC:DEC = 1:1, and 1M LiPF6 is used as the electrolyte to assemble the battery.

[0039] Example 3

[0040] This embodiment provides a method for preparing the negative electrode material, including the following steps:

[0041] Step (1): Take a certain amount of commercial silicon suboxide powder and lithium silicon alloy powder, put them into a mixer in a mass ratio of 90:10, the mixer speed is 200 rpm, the mixing time is 2 hours, and the silicon suboxide and lithium silicon alloy are mixed to obtain powder A with uniform composition.

[0042] Step (2): Take 10g of powder A obtained in step (1) and place it in a stainless steel crucible for heat treatment. The atmosphere is high-purity argon gas. The duration is the entire heating process and the entire cooling process. The heating rate is 5°C / min. The heat treatment temperature is 800°C. The holding time is 2 hours. The calcination pressure is atmospheric pressure. After calcination, the final product B-2, namely the pre-lithiated silicon suboxide anode material, can be obtained.

[0043] In the fabrication of lithium-ion button batteries, the above-prepared negative electrode material is mixed with PAA (binder) and acetylene (conductive agent) in a mass ratio of 8:1:1. A liquid electrode slurry is prepared using DMF as a solvent and coated onto the surface of copper foil. Then, a lithium metal sheet is used as the counter electrode, EC:DEC = 1:1, and 1M LiPF6 is used as the electrolyte to assemble the battery.

[0044] Example 4

[0045] This embodiment provides a method for preparing the negative electrode material, including the following steps:

[0046] Step (1): Take a certain amount of commercial silicon suboxide powder and lithium silicon alloy powder, put them into a mixer in a mass ratio of 70:30, the mixer speed is 200 rpm, the mixing time is 2 hours, and the silicon suboxide and lithium silicon alloy are mixed to obtain powder A with uniform composition.

[0047] Step (2): Take 10g of powder A obtained in step (1) and place it in a stainless steel crucible for heat treatment. The atmosphere is high-purity argon gas. The duration is the entire heating process and the entire cooling process. The heating rate is 5°C / min. The heat treatment temperature is 800°C. The holding time is 2 hours. The calcination pressure is atmospheric pressure. After calcination, the final product B-3, namely the pre-lithiated silicon suboxide anode material, can be obtained.

[0048] In the fabrication of lithium-ion button batteries, the above-prepared negative electrode material is mixed with PAA (binder) and acetylene (conductive agent) in a mass ratio of 8:1:1. A liquid electrode slurry is prepared using DMF as a solvent and coated onto the surface of copper foil. Then, a lithium metal sheet is used as the counter electrode, EC:DEC = 1:1, and 1M LiPF6 is used as the electrolyte to assemble the battery.

[0049] Example 5

[0050] This embodiment provides a method for preparing the negative electrode material, including the following steps:

[0051] Step (1): Take a certain amount of commercial silicon suboxide powder and lithium silicon alloy powder, put them into a mixer in a mass ratio of 80:20, the mixer speed is 200 rpm, the mixing time is 2 hours, and the silicon suboxide and lithium silicon alloy are mixed to obtain powder A with uniform composition.

[0052] Step (2): Take 10g of powder A obtained in step (1) and place it in a stainless steel crucible for heat treatment. The atmosphere is high-purity argon gas. The duration is the entire heating process and the entire cooling process. The heating rate is 5°C / min. The heat treatment temperature is 600°C. The holding time is 2 hours. The calcination pressure is atmospheric pressure. After calcination, the final product B-4, namely the pre-lithiated silicon suboxide anode material, can be obtained.

[0053] In the fabrication of lithium-ion button batteries, the above-prepared negative electrode material is mixed with PAA (binder) and acetylene (conductive agent) in a mass ratio of 8:1:1. A liquid electrode slurry is prepared using DMF as a solvent and coated onto the surface of copper foil. Then, a lithium metal sheet is used as the counter electrode, EC:DEC = 1:1, and 1M LiPF6 is used as the electrolyte to assemble the battery.

[0054] Example 6

[0055] This embodiment provides a method for preparing the negative electrode material, including the following steps:

[0056] Step (1): Take a certain amount of commercial silicon suboxide powder and lithium tin alloy powder, put them into a mixer in a mass ratio of 80:20, the mixer speed is 200 rpm, the mixing time is 2 hours, and the silicon suboxide and lithium tin alloy are mixed to obtain powder A with uniform composition.

[0057] Step (2): Take 10g of powder A obtained in step (1) and place it in a stainless steel crucible for heat treatment. The atmosphere is high-purity argon gas. The duration is the entire heating process and the entire cooling process. The heating rate is 5°C / min. The heat treatment temperature is 800°C. The holding time is 2 hours. The calcination pressure is atmospheric pressure. After calcination, the final product B-5, namely the pre-lithiated silicon suboxide anode material, can be obtained.

[0058] In the fabrication of lithium-ion button batteries, the above-prepared negative electrode material is mixed with PAA (binder) and acetylene (conductive agent) in a mass ratio of 8:1:1. A liquid electrode slurry is prepared using DMF as a solvent and coated onto the surface of copper foil. Then, a lithium metal sheet is used as the counter electrode, EC:DEC = 1:1, and 1M LiPF6 is used as the electrolyte to assemble the battery.

[0059] Example 7

[0060] This embodiment provides a method for preparing the negative electrode material, including the following steps:

[0061] Step (1): Take a certain amount of commercial silicon suboxide powder and lithium antimony alloy powder, put them into a mixer in a mass ratio of 80:20, the mixer speed is 200 rpm, the mixing time is 2 hours, and the silicon suboxide and lithium antimony alloy are mixed to obtain powder A with uniform composition.

[0062] Step (2): Take 10g of powder A obtained in step (1) and place it in a stainless steel crucible for heat treatment. The atmosphere is high-purity argon gas. The duration is the entire heating process and the entire cooling process. The heating rate is 5°C / min. The heat treatment temperature is 800°C. The holding time is 2 hours. The calcination pressure is atmospheric pressure. After calcination, the final product B-6, namely the pre-lithiated silicon suboxide anode material, can be obtained.

[0063] Example 8

[0064] This embodiment provides a method for preparing the negative electrode material, including the following steps:

[0065] Step (1): Take a certain amount of commercial silicon suboxide powder and lithium germanium alloy powder, put them into a mixer in a mass ratio of 80:20, the mixer speed is 200 rpm, and the mixing time is 2 hours to mix silicon suboxide and lithium silicon alloy to obtain powder A with uniform composition.

[0066] Step (2): Take 10g of powder A obtained in step (1) and place it in a stainless steel crucible for heat treatment. The atmosphere is high-purity argon gas. The duration is the entire heating process and the entire cooling process. The heating rate is 5°C / min. The heat treatment temperature is 800°C. The holding time is 2 hours. The calcination pressure is atmospheric pressure. After calcination, the final product B-7, namely the pre-lithiated silicon suboxide anode material, can be obtained.

[0067] In the fabrication of lithium-ion button batteries, the above-prepared negative electrode material is mixed with PAA (binder) and acetylene (conductive agent) in a mass ratio of 8:1:1. A liquid electrode slurry is prepared using DMF as a solvent and coated onto the surface of copper foil. Then, a lithium metal sheet is used as the counter electrode, EC:DEC = 1:1, and 1M LiPF6 is used as the electrolyte to assemble the battery.

[0068] Comparative Example 1

[0069] This comparative example provides a method for preparing a negative electrode material, including the following steps:

[0070] Step (1): Take a certain amount of commercial silicon suboxide powder and lithium silicon alloy powder, put them into a mixer in a mass ratio of 70:30, the mixer speed is 200 rpm, the mixing time is 2 hours, and the silicon suboxide and lithium silicon alloy are mixed to obtain powder A with uniform composition.

[0071] Step (2): Take 10g of powder A obtained in step (1) and place it in a stainless steel crucible for heat treatment. The atmosphere is high-purity argon gas. The duration is the entire heating process and the entire cooling process. The heating rate is 5°C / min. The heat treatment temperature is 200°C. The holding time is 2 hours. The calcination pressure is atmospheric pressure. After calcination, the final product C-1, namely the pre-lithiated silicon suboxide anode material, can be obtained.

[0072] In the fabrication of lithium-ion button batteries, the above-prepared negative electrode material is mixed with PAA (binder) and acetylene (conductive agent) in a mass ratio of 8:1:1. A liquid electrode slurry is prepared using DMF as a solvent and coated onto the surface of copper foil. Then, a lithium metal sheet is used as the counter electrode, EC:DEC = 1:1, and 1M LiPF6 is used as the electrolyte to assemble the battery.

[0073] In Example 2 above, commercial SiO x SEM images of the product from Example 2 are shown in Figures 2(a) and (b), and TEM images are shown in Figure 2(a). Figure 3 (a)-(d), XRD patterns as follows Figure 4 As shown in the figure. SEM results indicate that commercial SiO2... x With Li x After the high-temperature reaction, the material size remained within the range of 2-10 μm, but the surface size was also within the range of 2-10 μm. The surface became rough due to the deposition of a layer of nano-silicon particles. TEM results showed that after the high-temperature reaction of commercial silicon suboxide with lithium-silicon alloy, the surface was covered with a layer of nano-silicon particles. XRD results indicated that after calcination of commercial silicon suboxide and lithium-silicon alloy powders, a multiphase material containing Si and Li₂SiO₃ was formed.

[0074] Figure 5 The final product B-1 of Example 2 and commercially available SiO x The first charge-discharge curves show that after pre-lithiation treatment, the charging capacity of the material increased from 1355 mAh / g to 1593 mAh / g, and the first coulombic efficiency also increased from 63% to 89%.

[0075] Figure 6 The XRD pattern (a) and charge-discharge curve (b) of the final product B-2 prepared in Example 3 are shown in Example 3. The XRD results indicate that commercial SiO2... x After talking with Li x After Si was mixed and calcined, a multiphase material containing Si, Li₂SiO₃, and Li₂Si₂O₅ was formed. Charge-discharge curves showed that its initial charge capacity was 1279 mAh / g, and its coulombic efficiency was 85%.

[0076] Figure 7The XRD pattern (a) and charge-discharge curve (b) of the final product B-3 prepared in Example 4 are shown. The XRD results indicate that commercial SiO2... x After talking with Li x After Si was mixed and calcined, a multiphase material containing Si and Li4SiO4 was formed. The charge-discharge curve results showed that its initial charge capacity was 1806 mAh / g and its coulombic efficiency was 82%.

[0077] Figure 8 The XRD pattern (a) and charge-discharge curve (b) of the final product B-4 prepared in Example 5 are shown. The XRD results indicate that commercial SiO2... x After talking with Li x After Si was mixed and calcined, a multiphase material containing Si and Li2SiO3 was formed, with a composition similar to that of Example 2. Charge-discharge curves showed that its initial charge capacity was 1556 mAh / g and its coulombic efficiency was 86%.

[0078] Figure 9 The XRD pattern of the final product C-1 obtained in this comparative example is shown. XRD results indicate that commercial SiO2... x With Li x After calcination at 100℃ for 2 hours, the Si mixture still exhibits strong Li... 3.75 The diffraction peaks of Si and the relatively weak diffraction peaks of SiO indicate that SiO x With Li x Si did not react completely at 100℃. The preparation method of this invention is simple to operate, low in cost, safe in preparation process and without the generation of toxic substances, and the product has high water and oxygen stability, which is conducive to large-scale industrial production.

[0079] The above embodiments are merely illustrative examples and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations; therefore, any obvious variations or modifications derived therefrom remain within the scope of protection of this invention.

Claims

1. A method for preparing a lithium-ion battery anode material, characterized in that, Includes the following steps: The silica powder and lithium alloy powder are stirred and mixed in a mixer to obtain a uniform mixed powder A; The mixed powder A is heat-treated in an inert atmosphere at a temperature of 600℃-1800℃ to obtain the negative electrode material. The negative electrode material has a core-shell structure, and the negative electrode material is a lithium alloy of silicon suboxide and Li. x The shell, obtained by heat treatment after mixing M, comprises several nano-sized M particles, and the core material comprises M and Li. x MO y .

2. The preparation method according to claim 1, characterized in that, The lithium alloy Li x The M in M ​​represents silicon, tin, germanium, antimony, or magnesium.

3. The preparation method according to claim 1, characterized in that, The lithium alloy is one or a mixture of two or more of the following: lithium-silicon alloy, lithium-tin alloy, lithium-germanium alloy, lithium-antimony alloy, or lithium-magnesium alloy.

4. The preparation method according to claim 1, characterized in that, The mass ratio of the silicon suboxide powder to the lithium alloy powder is 99:1-60:

40.

5. The preparation method according to claim 1, characterized in that, The mixed powder A is heat-treated in an inert atmosphere at 600℃-1200℃ for 0.1-8 hours.

6. The preparation method according to claim 1, characterized in that, The inert atmosphere is one or a mixture of argon or helium.

7. The preparation method according to claim 6, characterized in that, The inert atmosphere is vented at a rate of 50-200 mL / min.

8. The preparation method according to claim 1, characterized in that, The particle size d of the silica powder 50 The range is 0.1-20 μm.

9. A lithium-ion battery, characterized in that, Including the negative electrode material prepared by the preparation method as described in claim 1 or 2.

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