Method for manufacturing negative electrode materials to improve the safety of lithium-ion batteries

Abstract

This invention provides a method for improving the safety of lithium-ion batteries. [Solution] A process of heating heavy oil to produce green coke (A), a process of raising the temperature to 850°C to 900°C at a first heating rate and maintaining it for 4 hours or more to obtain a carbon-containing material from the green coke (B), and crushing and classifying the carbon-containing material to obtain a particle size distribution D 50 Particle size is 8μm~12μm and particle size distribution D 10 The process includes (C) obtaining a carbon-containing powder having a particle size of 1 μm to 8 μm, (D) raising the temperature to 1030°C to 1220°C at a second heating rate and maintaining it for 4 hours or more to obtain carbon powder, (E) adding 4% by weight or more of asphalt to the carbon powder, then raising the temperature to 1030°C to 1220°C at a third heating rate and maintaining it for 5 hours or more to obtain asphalt-modified soft carbon, and (F) adding soft carbon to graphite in a weight ratio of 1:1 to 39 to obtain a first negative electrode material.

Claims

1. The process of heating heavy oil to produce raw coke (A), Step (B) involves heating the green coke to 850°C to 900°C at a first heating rate of 3°C / min to 5°C / min and maintaining the temperature for 4 hours or more to obtain a carbon-containing material. The carbon-containing material is crushed, and the crushed carbon-containing material is classified to obtain the particle size distribution D ５０ Particle size is 8 μm to 12 μm and particle size distribution D １０ Step (C) to obtain a carbon-containing powder having a particle size of 1 μm to 8 μm, Step (D) involves heating the carbon-containing powder to obtain carbon powder by raising the temperature to 1030°C to 1220°C at a second heating rate of 3°C / min to 10°C / min and maintaining the temperature for 4 hours or more, Step (E) involves adding 4% by weight or more of asphalt relative to the carbon powder, then heating the carbon powder with the added asphalt to 1030°C to 1220°C at a third heating rate of 0.90°C / min to 1.25°C / min and maintaining the temperature for 5 hours or more to obtain soft carbon of asphalt modification. The weight ratio of the soft carbon to graphite is 1:1 to 39, and the process (F) involves adding the soft carbon to the graphite to make a first negative electrode material. Methods to improve the safety of lithium-ion batteries, including [specific examples of such methods].

2. In step (C) above, the crushed carbon-containing material is classified to determine the particle size distribution D ５０ is 8 μm to 12 μm, particle size distribution D １０ Particle size is 2 μm to 6 μm and particle size distribution D ９０ A method for improving the safety of a lithium-ion battery according to claim 1, wherein a carbon-containing powder having a particle size of 16 μm to 18 μm is obtained, and in step (F), the weight ratio of the soft carbon to the graphite is 1:1 to 39, and the soft carbon is added to the graphite to form a second negative electrode material.

3. A method for improving the safety of a lithium-ion battery according to claim 1, wherein in step (D), the carbon-containing powder is heated to 1180°C to 1220°C at the second heating rate; in step (E), the carbon powder to which asphalt has been added is heated to 1180°C to 1220°C at the third heating rate; and in step (F), the soft carbon is added to the graphite in a weight ratio of 1:1 to 39 to form a third negative electrode material.

4. A method for improving the safety of a lithium-ion battery according to any one of claims 1 to 3, wherein in step (F), the weight ratio of the soft carbon to the graphite is 1:7 / 3 to 39.

5. A method for improving the safety of a lithium-ion battery according to any one of claims 1 to 3, wherein the negative electrode obtained in step (F) consists of a first negative electrode material, a second negative electrode material, or a third negative electrode material, has a discharge capacity retention rate of 65% or more at a discharge current of 6C, and an alternating current internal battery impedance (ACIR) of 31.0 mΩ or less.

6. A method for improving the safety of a lithium-ion battery according to any one of claims 1 to 3, wherein the negative electrode obtained in step (F) is made of a first negative electrode material, a second negative electrode material, or a third negative electrode material, has a temperature rise of less than 30°C at a charging current of 5C and a temperature rise of less than 33°C at a discharge current of 5C.

7. In step (F) above, if the weight ratio of the soft carbon to the graphite is 1:1, the negative electrode made of the second negative electrode material has a temperature rise of less than 11°C at a charging current of 5C and a temperature rise of less than 13°C at a discharge current of 5C, a method for improving the safety of a lithium-ion battery according to claim 2.

8. In step (F) above, if the weight ratio of the soft carbon to the graphite is 1:7 / 3, the negative electrode made of the third negative electrode material in a soft pack battery cell with a capacity of 36 Ah has a temperature rise of less than 2.1°C at a charging current of 1C and a temperature rise of less than 3.3°C at a discharge current of 1C, a method for improving the safety of a lithium-ion battery according to claim 3.

9. A method for improving the safety of a lithium-ion battery according to any one of claims 1 to 3, wherein, in step (F), the weight ratio of the soft carbon to the graphite is 1:1, and the negative electrode made of the first negative electrode material, the second negative electrode material, or the third negative electrode material obtained in step (F) has a temperature rise of less than 7.2°C at a charging current of 3C.

10. A method for improving the safety of a lithium-ion battery according to any one of claims 1 to 3, wherein in step (F), the first negative electrode material, the second negative electrode material, or the third negative electrode material further comprises an adhesive and conductive carbon black.

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