Sanyo Electric Co., Ltd.

Na Wang

Shinji Kasamatsu

Yoshio Kato

A non-aqueous electrolyte secondary battery having a long cycle life and generates a small amount of gas during, for example, storage in a charged state. A negative electrode in a non-aqueous electrolyte secondary battery according to an exemplary embodiment includes a negative electrode current collector and a negative electrode mixture layer formed on the negative electrode current collector. The negative electrode mixture layer contains a water-soluble polymer and a negative electrode active material containing a silicon-based active material. The water-soluble polymer contains 0.30 mol/100 g or more and 0.40 mol/100 g or less of an acrylic acid monomer unit and 10mol/100 g or more and 10mol/100 g or less of a tetrafunctional (meth)acrylate monomer unit. An aqueous solution containing 1% by mass of the polymer in terms of solid content has a viscosity of 0.05 Pa&#xb7;s or higher and 0.70 Pa&#xb7;s or lower.

Non-aqueous electrolyte secondary battery

Gas evolution during the high-temperature storage of a non-aqueous electrolyte secondary battery is suppressed to improve the high-temperature storage characteristics of the non-aqueous electrolyte secondary battery. A negative electrode for a non-aqueous electrolyte secondary battery contains silicon-containing particles and graphite particles. A covering layer is disposed on each of the graphite particles. The covering layer contains a first covering material and a second covering material, the first covering material containing particles that can be made to swell with a non-aqueous electrolytic solution, the second covering material containing a water-soluble polymer material. The first covering material is disposed on a surface of each of the graphite particles. The mass ratio of the second covering material to the first covering material is higher than 1.

Negative electrode for non-aqueous electrolyte secondary battery

A non-aqueous electrolyte secondary battery including a silicon material as a negative electrode active material has good discharge rate characteristics. A negative electrode according to an exemplary embodiment includes a negative-electrode current collector and a negative-electrode mixture layer formed on the current collector. The negative-electrode mixture layer contains graphite and a silicon material. A first region that extends from the surface of the mixture layer remote from the negative-electrode current collector in the thickness direction of the negative-electrode mixture layer and has a thickness equal to 40% of the thickness of the mixture layer contains a larger amount of the silicon material than a second region that extends from the surface of the mixture layer adjacent to the negative-electrode current collector and has a thickness equal to 40% of the thickness of the mixture layer. The first region has a lower density than the second region.

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Osaka, Japan

Na Wang