# US 8,771,873 B2 · Lithium secondary battery and method of manufacturing the same

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- Number: US 8,771,873 B2
- Document ID: US8771873B2
- Status: Granted
- Kind: B2
- Application number: 11/771,552
- Filed: 2007-06-29
- Published: 2008-05-29
- Granted: 2014-07-08
- Earliest claimed: 2006-06-30
- Assignees: Sanyo Electric Co., Ltd.
- Applicants: Atsushi Fukui; Hiroshi Minami; Mariko Torimae; Yasuyuki Kusumoto
- Inventors: Atsushi Fukui; Hiroshi Minami; Mariko Torimae; Yasuyuki Kusumoto
- Web page: https://patentgrep.com/patent/US8771873B2

## CPC

- H01M 4/134: Electrodes based on metals, Si or alloys
- H01M 4/0404: {by coating on electrode collectors}
- H01M 4/38: of elements or alloys
- H01M 4/505: of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
- H01M 4/525: of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
- H01M 4/587: for inserting or intercalating light metals
- H01M 4/622: {being polymers}
- H01M 4/625: {Carbon or graphite}
- H01M 4/64: Carriers or collectors
- H01M 4/661: {Metal or alloys, e.g. alloy coatings (H01M4/669 take precedence)}
- H01M 2004/027: {Negative electrodes}
- Y02E 60/10: Energy storage using batteries
- H01M: PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

A lithium secondary battery includes an electrode assembly having a positive electrode (1), a negative electrode (2) having a negative electrode current collector and a negative electrode active material layer formed on a surface of the negative electrode current collector and composed of a binder and negative electrode active material particles containing silicon and/or a silicon alloy, and a separator (3) interposed between the electrodes. The electrode assembly is impregnated with a non-aqueous electrolyte. The binder contains a polyimide resin represented by the following chemical formula (1): where R contains at least a benzene ring, and n is within the range of from 10 to 100,000, and the negative electrode active material particles have an average particle size of 5 μm or greater.

## Claims

### Claim 1

A lithium secondary battery comprising:
a positive electrode;
a negative electrode comprising a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector, the negative electrode active material layer comprising a binder and negative electrode active material particles containing silicon particles and/or silicon alloy particles;
a separator interposed between the electrodes; and
an electrode assembly comprising the positive electrode, the negative electrode, and the separator; and
a non-aqueous electrolyte impregnated in the electrode assembly, wherein
the binder contains a polyimide resin represented by the following chemical formula (1):
where R in the chemical formula (1) is a functional group represented by the following chemical formula (2) or (3):
and n is within the range of from 10 to 100,000; and
the silicon particles and the silicon alloy particles have an average particle size of 5-25 μm.

### Claim 2 (depends on 1)

The lithium secondary battery according to claim 1, wherein the polyimide resin represented by the chemical formula (1) has a molecular weight of 1000-100,000.

### Claim 3 (depends on 1)

The lithium secondary battery according to claim 1, wherein the negative electrode current collector has a surface roughness Ra of 0.2-2 μm.

### Claim 4 (depends on 1)

The lithium secondary battery according to claim 1, wherein the negative electrode current collector is selected from the group consisting of a copper foil, a copper alloy foil, a metal foil having a copper layer formed on its surface, and a metal foil having a copper alloy layer formed on its surface.

### Claim 5 (depends on 1)

The lithium secondary battery according to claim 1, wherein the positive electrode contains a positive electrode active material comprising a lithium-transition metal composite oxide.

### Claim 6 (depends on 5)

The lithium secondary battery according to claim 5, wherein the lithium-transition metal composite oxide is a lithium-transition metal composite oxide represented by the chemical formula LiaNixMnyCozO2, wherein 0≦a≦1, x+y+z=1, 0≦x≦1, 0≦y≦1, and 0≦z≦1.

### Claim 7 (depends on 6)

The lithium secondary battery according to claim 6, wherein the theoretical electrical capacity ratio of the positive electrode to the negative electrode is 0.4-1.2.

### Claim 8 (depends on 1)

The lithium secondary battery according to claim 1, wherein the silicon particles and the silicon alloy particles have a crystallite size of 1-100 nm.

### Claim 9 (depends on 8)

The lithium secondary battery according to claim 8, wherein the silicon particles and the silicon alloy particles are prepared by thermally decomposing or thermally reducing a material containing a silane compound.

### Claim 10 (depends on 9)

The lithium secondary battery according to claim 9, wherein the silicon particles and/or the silicon alloy particles are prepared by pulverizing an ingot of silicon and/or an ingot of a silicon alloy that is/are prepared by thermally decomposing or thermally reducing a material containing a silane compound, and classifying the pulverized material.

### Claim 11 (depends on 9)

The lithium secondary battery according to claim 9, wherein the silane compound is monosilane and/or trichlorosilane.

### Claim 12 (depends on 1)

The lithium secondary battery according to claim 1, wherein the negative electrode active material layer contains 3 weight % to 20 weight %, based on the weight of the negative electrode active material, of graphite powder having an average particle size of from 3 μm to 15 μm.

### Claim 13 (depends on 1)

The lithium secondary battery according to claim 1, wherein the negative electrode active material particles comprise silicon particles having a purity of 95-99 weight %.