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Negative Electrode Active Material For Nonaqueous Electrolyte Secondary Batteries

a secondary battery and active material technology, applied in the direction of active material electrodes, cell components, electrical equipment, etc., can solve the problems of low electron conductivity, silicon-based active materials, and active materials that have already reached the theoretical limit in terms of capacity, so as to promote the capacity of batteries and increase the cycle characteristics of batteries. , the effect of high reactivity

Inactive Publication Date: 2017-12-07
MITSUI MINING & SMELTING CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention proposes a negative electrode active material for nonaqueous electrolyte secondary batteries that contains silicon. This material has high reactivity and can enhance the cycle characteristics of the battery. However, the particles can aggregate and decrease fluidity, which can lead to decreased strength of the electrode and deterioration of the active material. The present invention controls the amount of water present on the surface of the particles to a specific range. This prevents aggregation, increases the binding strength to the binder, and further improves the cycle characteristics of the battery.

Problems solved by technology

Currently, most of the negative electrodes of commercially available batteries use graphite as the negative electrode active material; however, this active material has already reached the theoretical limit in terms of capacity, and it is now necessary to develop new negative electrode active materials.
However, on the other hand, silicon-based active materials have a problem that electron conductivity is not so high compared with graphite.
Also, since silicon-based active materials undergo large volumetric changes caused by insertion and desorption of lithium ions, silicon-based active materials also have a problem that detachment from the active material layer is likely to occur as charging and discharging are repeated, consequently deterioration of cycles or reduction of energy density occurs, the battery performance is decreased, and safety of the battery is decreased.

Method used

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  • Negative Electrode Active Material For Nonaqueous Electrolyte Secondary Batteries
  • Negative Electrode Active Material For Nonaqueous Electrolyte Secondary Batteries
  • Negative Electrode Active Material For Nonaqueous Electrolyte Secondary Batteries

Examples

Experimental program
Comparison scheme
Effect test

examples 2 to 7

[0126]Negative electrode active materials were obtained in the same manner as in Example 1, except that the proportion of nitrogen and air of the atmosphere at the time of jet mill pulverization was changed, and also, the degree of pulverization was changed. The D50 and the amount of water / CS of these materials are presented in the following Table 1.

[0127]Furthermore, negative electrodes were obtained in the same manner as in Example 1, except that at the time of preparing the negative electrode mixture, the mixing mass ratio of the fine silicon powder and graphite was changed to fine silicon powder:graphite=50:50 in Examples 2 and 3, and to fine silicon powder:graphite=10:90 in Examples 4 to 7.

example 8

[0128](1) Production of Negative Electrode Active Material

[0129]An ingot of silicon (Si) was heated to melt, and the molten liquid that had been heated to 1600° C. was subjected to a micronization treatment by a steam explosion atomization method using the apparatus described in FIG. 2 of WO 01 / 081033. At this time, the inner diameter of the cylindrical mixing nozzle 2 was set to 2.0 mm, and the amount of the coolant circulating in the mixing nozzle was set to 100 L / min. Water at room temperature was used as the coolant. A molten liquid of silicon was dropped (free-fall dropping) into the mixing nozzle 2 in an amount of 13 g each. The cooling rate at this time was estimated to be 106 K / s to 108 K / s according to the estimation method described above.

[0130]The powder obtained by the steam explosion atomization was subjected to jet mill pulverization in a nitrogen atmosphere, and thus a negative electrode active material (D50: 2.5 μm) was obtained. The amount of water / CS at that time w...

example 9

[0136]Boron was added to an ingot of silicon (Si), and the ingot was heated to melt. The molten liquid that had been heated to 1600° C. was subjected to steam explosion atomization in the same manner as in Example 8. The solid solubilized amount of boron was adjusted to 2 parts by mass relative to 100 parts by mass of silicon.

[0137]Thereafter, a heat treatment was carried out for retaining the product temperature at 950° C. for one hour, and then jet mill pulverization was carried out in a nitrogen atmosphere. Thus, a negative electrode active material (D50: 2.6 μm) was obtained. The amount of water / CS at that time was 5 ppm / CS, and the results are presented in Table 1.

[0138]The preparation of the negative electrode mixture and the application and heating treatment of the negative electrode mixture were carried out in the same manner as in Example 8, and thus a negative electrode was obtained.

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Abstract

Provided is a novel method of preparing a negative electrode for nonaqueous electrolyte secondary batteries, which contains silicon and is capable of improving cycle characteristics and is also capable of suppressing aggregation of active material particles in a slurry. After formation of a molten liquid by any one of methods (i) to described in the specification, the molten liquid is micronized by atomization or liquid quenching, thereby forming a micronized active material in the form of powder, and the micronized active material is pulverized and classified in a nitrogen atmosphere in which air is present in an amount of less than 1%, and the balance is composed of nitrogen, to thereby adjust the particle size of the micronized active material.

Description

TECHNICAL FIELD[0001]The present invention relates to a negative electrode active material that can be used in nonaqueous electrolyte secondary batteries such as lithium secondary batteries.BACKGROUND ART[0002]A negative electrode for nonaqueous electrolyte secondary batteries is generally produced by mixing particles of an active material formed from a material into which lithium ions can be inserted by charging, with a binder, a conductive material and a solvent, applying the mixture thus obtained on the surface of a current collector, drying the mixture to form a coating film, and further subjecting the coating film to press processing.[0003]In recent years, along with the development in applications such as electric vehicles and smart phones, there is an increasing demand for capacity increase and lengthening of the service life of batteries. Currently, most of the negative electrodes of commercially available batteries use graphite as the negative electrode active material; how...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): H01M4/134H01M4/38H01M4/62H01M4/02H01M10/052
CPCH01M10/052H01M2004/027H01M4/622H01M2004/021H01M4/386H01M4/134H01M4/38H01M2300/0017Y02E60/10H01M4/62H01M10/05
Inventor INOUE, DAISUKEKAGEI, SHINYATODOROV, YANKO MARINOV
Owner MITSUI MINING & SMELTING CO LTD
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