Negative electrode of lithium ionic secondary battery and battery thereof

A secondary battery and lithium ion technology, applied in secondary batteries, battery electrodes, active material electrodes, etc., can solve the problems of increasing the specific surface area of ​​graphite, reducing the reversible capacity and capacity of graphite, destroying the structure of graphite, etc., and achieve high current discharge The effect of excellent performance

Active Publication Date: 2009-06-10
BYD CO LTD
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  • Abstract
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  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, this improvement is still not applicable to the application of larger current rate characteristics (10C, 15C, 20C rate, where 1C is the design capacity), while reducing graphite particles will increase the specific surface area of ​​graphite, but also partially destroy graphite structure, thereby reducing the reversible capacity and capacity of graphite

Method used

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  • Negative electrode of lithium ionic secondary battery and battery thereof

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0024] 2 kilograms of natural graphite with an average particle size of 1.0 microns, a corrected value of d002 between crystallite layers, and a specific surface area of ​​13.6 square meters per gram is the first graphite; The natural graphite with a correction value of 0.3364 nanometers and a specific surface area of ​​4.5 square meters per gram is the second graphite; after mixing the two, add 50 g of phase deposited carbon fiber (VGCF) and mix thoroughly. Graphite A is obtained.

[0025] 970 grams of graphite A and 30 grams of styrene-butadiene rubber (SBR) were mixed. Add 1500 ml of water and stir evenly to make negative electrode slurry, apply it evenly on both sides of 12 micron copper foil with a pulper, heat and dry under vacuum at 125°C for 1 hour, roll, and cut into pieces to obtain 790mm (length) × 57.5 mm (width)×85 μm (thickness) negative electrode, each negative electrode contains 5.1-5.2 grams of graphite to obtain the negative electrode A1.

Embodiment 2

[0027] The coating agent is petroleum pitch, and the first graphite and the second graphite are respectively coated to obtain the coated first graphite and the coated second graphite, wherein the coated graphite is exactly the same as the graphite used in the example 1 . The coating agent petroleum pitch is dissolved in the solvent toluene in a certain proportion, and the total amount of petroleum pitch and graphite is mixed in a weight percentage of 100:8, of which graphite is 100, petroleum pitch is 8, and then cracked under inert gas conditions at 1100°C to cladding.

[0028] 2 kilograms of coated first graphite with an average particle size of 1.0 microns, a corrected value of d002 of the crystallite interlayer distance of 0.3375 nanometers, and a specific surface area of ​​10.5 square meters per gram after coating; 8 kilograms of coated first graphite with an average particle size of 9.5 microns, Coated second graphite with a corrected value of d002 of crystallite layer ...

Embodiment 3-4

[0037] According to the method for coating lithium ion secondary battery negative electrode active material according to the method of embodiment 1, the difference is that the particle diameter of the graphite value that is coated is D 50 , interlayer distance d002 value of crystallite, specific surface area, the relative weight ratio between graphite, the ratio of conductive agent to the total weight of graphite, see Table 1 for details.

[0038] Table 1

[0039]

[0040] The weight ratio of the second graphite to the first graphite 80：20 80：20 70：30 95：5

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Abstract

The invention provides a lithium ion secondary cell cathode and a cell. The lithium ion secondary cell cathode comprises a conductive agent, graphite, a caking agent and a current collecting body; the graphite is formed by mixing first graphite and second graphite by weight percentage of 5-30 to 95-70; the average particle diameter of the first graphite is between 0.5 and 2 mu m; the average particle diameter of the second graphite is between 4 and 12 mu m, wherein the graphite is coated-type graphite coated with a coating agent; and the coating agent is 1 to 20 weight percent of gross weight of the graphite. The average particle diameter of the first coated-type graphite is between 0.8 and 2.3 mu m; and the average particle diameter of the second coated-type graphite is between 5 and 13 mu m. The provided cathode has excellent large-current discharging performance and is in particular suitable for application of a power cell.

Description

technical field [0001] The invention relates to the field of lithium ion secondary batteries. Background technique [0002] Carbon materials are negative electrode active materials for lithium-ion secondary batteries, and are suitable for the extraction / intercalation of lithium ions. Among them, graphite has good conductivity, high crystallinity, and good layered structure. The reversible charge and discharge capacity can reach more than 300 milliampere hours / gram (mAh / g), which is close to LiC formed by lithium in carbon materials. 6 The theoretical specific capacity is 372mAh / g, and the de / intercalation reaction or de / intercalation capacity of lithium in graphite mainly occurs between 0 volts and 0.25 volts (corresponding to Li + / Li), has a good charge and discharge platform. [0003] Although the lithium-ion secondary battery has very obvious advantages, it has poor rate characteristics and safety performance problems. At present, there are still certain limitations i...

Claims

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Application Information

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IPC IPC(8): H01M4/02H01M4/58H01M4/62H01M10/40H01M4/133H01M10/0525
CPCY02E60/12Y02E60/10
Inventor 姜俊刚李科张建飞刘卫平
Owner BYD CO LTD
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