Composite cathode material for lithium ion cell and preparing method thereof

Abstract

The invention relates to a lithium ion battery composite cathode material and a preparation method thereof, which belongs to the technical field of lithium ion battery. The invention aims at improving the cycle performance of silicon cathode material at the same time when keeping the high ratio volume of lithium ion battery silicon cathode material. The proposal of the invention is that silica-based material coated by disordered carbon is treated with surface modification processing by utilizing lithium salt, namely, the lithium salt is coated on the surface of Si / G / DC (silicon / graphite / disordered carbon) to be prepared into the composite cathode material, therefore, the lithium-embedding and removing depth of the silicon can be effectively controlled, and the material is the lithium ion battery composite cathode material which has high specific capacity and good cyclical stability; furthermore, the material is safe and pollution-free, and presents higher thermal stability in various lithium salt electrolytes and solvents.

Description

technical field

[0001] The invention relates to a negative electrode material of a lithium ion battery and a preparation method thereof, belonging to the technical field of lithium ion batteries. technical background

[0002] Compared with traditional secondary batteries, lithium-ion batteries have the advantages of high open circuit voltage, high energy density, long service life, no memory effect, no pollution, and small self-discharge, and are more and more widely used. The current commercial lithium-ion battery anode materials include graphite, acetylene black, microbead carbon, petroleum coke, pyrolysis polymer, pyrolysis carbon, etc. The volume change of carbon-based materials is very small during the lithium intercalation and extraction process, and has excellent cycle stability, but the charge-discharge specific capacity of carbon-based negative electrode materials is low, and the theoretical capacity is 372mAh / g, and it has been developed to be close to the theoreti...

Examples

Embodiment 1

[0023] The preparation method of the composite negative electrode material of lithium ion battery, comprises the following steps:

[0024] 1) Preparation of disordered carbon-coated composite silicon-based materials, Si / G / DC:

[0025] Add 1.2g of nano-silica powder with an average particle size of 50nm and 2.8g of natural graphite into trichlorethylene dissolved with 4g of pitch, the ball-to-material ratio is 15:1, and ball mill at a speed of 250 rpm for 18 hours under the protection of argon. , after ball milling, stir at 70°C until dry;

[0026] Under the protection of argon, it was treated at 1000 °C for 2 h, and then naturally cooled to room temperature. Among them, the flow rate of Ar gas is 100ml / min, and the heating rate is 5°C / min, and the disordered carbon-coated Si / G / DC material is made. The Si / G / DC material is ground and sieved with a 300-mesh standard sieve for later use.

[0027] 2) Li 2 ZrO 3 Preparation of coated Si / G / DC materials: Li 2 ZrO 3 The precurso...

Embodiment 2

[0036] Its preparation process is with embodiment 1, difference is that Li 2 ZrO 3 The coating amount is 1%. The electrode preparation method, electrode composition and testing method are the same as in Example 1. Figure 4 It is the cycle performance curve of the composite negative electrode material in this example. The initial discharge capacity is 552mAh / g. The capacity increases in the first 20 cycles, but the capacity decays rapidly after 30 cycles. After 75 cycles, lithium intercalation The capacity is 311mAh / g.

Embodiment 3

[0038] Its preparation process is with embodiment 1, difference is that Li 2 ZrO 3 The coating amount is 3%. The electrode preparation method, electrode composition and testing method are the same as in Example 1. 3% Li 2 ZrO 3 The first reversible capacity of the coating material is 331mAh / g. The lithium intercalation depth of the material is too shallow, which greatly affects the specific capacity, and can no longer show the characteristics of high specific capacity of silicon-containing materials.

technical field

[0001] The invention relates to a negative electrode material of a lithium ion battery and a preparation method thereof, belonging to the technical field of lithium ion batteries. technical background

[0002] Compared with traditional secondary batteries, lithium-ion batteries have the advantages of high open circuit voltage, high energy density, long service life, no memory effect, no pollution, and small self-discharge, and are more and more widely used. The current commercial lithium-ion battery anode materials include graphite, acetylene black, microbead carbon, petroleum coke, pyrolysis polymer, pyrolysis carbon, etc. The volume change of carbon-based materials is very small during the lithium intercalation and extraction process, and has excellent cycle stability, but the charge-discharge specific capacity of carbon-based negative electrode materials is low, and the theoretical capacity is 372mAh / g, and it has been developed to be close to the theoreti...

Examples

Embodiment 1

[0023] The preparation method of the composite negative electrode material of lithium ion battery, comprises the following steps:

[0024] 1) Preparation of disordered carbon-coated composite silicon-based materials, Si / G / DC:

[0025] Add 1.2g of nano-silica powder with an average particle size of 50nm and 2.8g of natural graphite into trichlorethylene dissolved with 4g of pitch, the ball-to-material ratio is 15:1, and ball mill at a speed of 250 rpm for 18 hours under the protection of argon. , after ball milling, stir at 70°C until dry;

[0026] Under the protection of argon, it was treated at 1000 °C for 2 h, and then naturally cooled to room temperature. Among them, the flow rate of Ar gas is 100ml / min, and the heating rate is 5°C / min, and the disordered carbon-coated Si / G / DC material is made. The Si / G / DC material is ground and sieved with a 300-mesh standard sieve for later use.

[0027] 2) Li 2 ZrO 3 Preparation of coated Si / G / DC materials: Li 2 ZrO 3 The precurso...

Embodiment 2

[0036] Its preparation process is with embodiment 1, difference is that Li 2 ZrO 3 The coating amount is 1%. The electrode preparation method, electrode composition and testing method are the same as in Example 1. Figure 4 It is the cycle performance curve of the composite negative electrode material in this example. The initial discharge capacity is 552mAh / g. The capacity increases in the first 20 cycles, but the capacity decays rapidly after 30 cycles. After 75 cycles, lithium intercalation The capacity is 311mAh / g.

Embodiment 3

[0038] Its preparation process is with embodiment 1, difference is that Li 2 ZrO 3 The coating amount is 3%. The electrode preparation method, electrode composition and testing method are the same as in Example 1. 3% Li 2 ZrO 3 The first reversible capacity of the coating material is 331mAh / g. The lithium intercalation depth of the material is too shallow, which greatly affects the specific capacity, and can no longer show the characteristics of high specific capacity of silicon-containing materials.

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