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Negative electrode material for nonaqueous secondary cells, negative electrode for nonaqueous secondary cells, and nonaqueous secondary cell

a secondary cell and negative electrode technology, applied in the field of negative electrode material for nonaqueous secondary cells, can solve the problems of short circuit of two electrodes, deterioration of cycle performance, and deterioration of high-rate charging/discharging characteristics, etc., to achieve excellent cycle performance, small charging/discharging irreversible capacity, excellent high-rate charging/discharging characteristics

Inactive Publication Date: 2009-08-27
MITSUBISHI CHEM CORP +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The resulting negative electrode exhibits reduced initial charging / discharging irreversible capacity, improved high-rate charging / discharging characteristics, and excellent cycle performance, enabling stable and efficient production of nonaqueous secondary batteries with enhanced capacity maintenance after 200 cycles.

Problems solved by technology

However, metal electrodes have problems in that when charge and discharge are repeated, lithium is deposited on electrodes dendritically and, finally, two electrodes are short-circuited.
However, there are problems in that since graphite is a flat crystal, graphite tends to be oriented parallel to the current collector in the electrode and, thereby, a high-rate charging / discharging characteristics tends to deteriorate; and since the expansion of the electrode in the charging / discharging cycle is significant, a cycle performances tends to deteriorate.
However, the graphite granulated particles described in this patent document have problems in that the performance as a negative electrode material for a lithium ion secondary battery, in particular, a reduction of the irreversible capacity and an improvement of the cycle performances are not always adequate.
If graphitization of the graphite granulated particles excessively proceeds, there is a tendency of the characteristic, in particular the liquid immersion property, in the preparation of secondary battery to become inadequate.
If amorphous portions are large, there is a problem in that it is hard to press.
When the pressing is performed forcedly and crushing occurs, the loss is increased, and it is difficult to produce a high-capacity cell.

Method used

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  • Negative electrode material for nonaqueous secondary cells, negative electrode for nonaqueous secondary cells, and nonaqueous secondary cell
  • Negative electrode material for nonaqueous secondary cells, negative electrode for nonaqueous secondary cells, and nonaqueous secondary cell

Examples

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Effect test

example 1

[0168]An amorphous carbon material (needle coke) was subjected to coarse crushing, and was further pulverized with a fine grinding mill (“Sample Mill” produced by Hosokawa Micron Corporation). Coarse particles were removed with a sieve having an opening of 45 μm, so that carbonaceous particles having a median diameter of 12.2 μm, a minimum particle size of 1.5 μm, a maximum particle size of 68 μm, and an average circularity of 0.80 were produced.

[0169]The resulting carbonaceous particles and a binder pitch having a softening point of 88° C. were mixed in a weight ratio of 100:34. The resulting mixture was put into a kneader having a masticator type agitating blade heated to 128° C. in advance and kneading was performed for 20 minutes.

[0170]The kneaded product, which had been kneaded adequately, was filled in a mold of a mold pressing machine preheated to 108° C. in advance, and was stood for 5 minutes. After the temperature of the kneaded product was stabilized, a plunger was pushed...

example 2

[0184]An amorphous carbon material containing less than 0.1 percent by weight of volatile matter was subjected to coarse crushing, and was further pulverized with a fine grinding mill (“Sample Mill” produced by Hosokawa Micron Corporation). Coarse particles were removed with a sieve having an opening of 45 μm, so that carbonaceous particles having a median diameter of 9.0 μm, a minimum particle size of 0.6 μm, a maximum particle size of 51.5 μm, and an average circularity of 0.80 were produced.

[0185]The resulting carbonaceous particles and a binder pitch having a softening point of 88° C. were mixed in a weight ratio of 100:34, and 30 parts by weight of graphitization catalyst (Fe2O3) was added relative to 100 parts by weight of the mixture. The resulting mixture was put into a kneader having a masticator type agitating blade heated to 128° C. in advance and kneading was performed for 20 minutes. In a manner similar to that in Example 1, molding, removal of VM, graphitization, pulve...

example 3

[0188]Natural graphite having a median diameter of 13.7 μm, a minimum particle size of 5.1 μm, and a maximum particle size of 51.5 μm and a binder pitch having a softening point of 88° C. were mixed in a weight ratio of 100:30. The resulting mixture was put into a kneader having a masticator type agitating blade heated to 128° C. in advance and kneading was performed for 20 minutes.

[0189]The kneaded product, which had been kneaded adequately, was filled in a mold of a mold pressing machine preheated to 108° C. in advance, and was stood for 5 minutes. After the temperature of the kneaded product was stabilized, a plunger was pushed, and molding was performed by applying a pressure of 5 kgf / cm2 (0.20 MPa). This pressure was maintained for 1 minute, and the movement was stopped. After the pressure reduction was completed, a molded product was taken out.

[0190]The resulting molded product was put into a metal saggar, which was a heat-resistant container, and gaps were filled with graphit...

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Abstract

A negative electrode material for a nonaqueous secondary battery capable of realizing a nonaqueous secondary battery having a small charging / discharging irreversible capacity at an initial cycle, exhibiting an excellent high-rate charging / discharging characteristics and an excellent cycle performances, and having no electrodeposition problem is provided. The main component of the material is graphite particles. The median diameter of the graphite particles is 5 μm or more, and 40 μm or less in the volume-basis particle size distribution based on the laser diffraction / scattering particle size distribution measurement. The tapping density of the negative electrode material is 0.7 g / cm3 or more. The specific surface area measured by a BET method is 0.2 m2 / g or more, and 8 m2 / g or less. When an electrode is produced from the negative electrode material by a predetermined method for manufacturing an electrode, and the surface of the resulting electrode is measured with a laser shape measurement microscope, the skewness (Rsk) prescribed by JIS B 0601 of the surface roughness curve is −1.7 or more, and 0 or less.

Description

TECHNICAL FIELD[0001]The present invention relates to a negative electrode material to be used for a nonaqueous secondary battery, a negative electrode including this negative electrode material, and a nonaqueous secondary battery including this negative electrode.BACKGROUND ART[0002]In recent years, as electronic apparatuses have been miniaturized, demands for high-capacity secondary batteries have been increased. In particular, nonaqueous secondary batteries exhibiting a higher energy density as compared with those of nickel-cadmium cells and nickel metal-hydride batteries have been noted. Heretofore, metals, graphite, and the like have been studied as negative electrode active materials of nonaqueous secondary batteries. However, metal electrodes have problems in that when charge and discharge are repeated, lithium is deposited on electrodes dendritically and, finally, two electrodes are short-circuited. Therefore, carbon materials, in particular, graphite, have been noted becaus...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): H01M4/58H01M4/1393H01M4/587H01M10/0525
CPCH01M4/0404H01M4/0409H01M4/0435Y02E60/122H01M4/587H01M10/0525H01M2004/021H01M4/1393Y02E60/10H01M4/58H01M4/02H01M10/05
Inventor ONISHI, NOBUYUKISATOH, HIDEHARUYAMAGUCHI, KEITA
Owner MITSUBISHI CHEM CORP
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