Nec Corporation

Suguru Tamai

Hitoshi Ishikawa

Daisuke Kawasaki

Noboru Yoshida

Ikiko Shimanuki

Kazuhiko Inoue

Shin Serizawa

Takashi Ohtsuka

Shinya Sudo

The purpose of one embodiment of the present invention is to provide a lithium ion secondary battery which has improved cycle characteristics and the negative electrode of which comprises a silicon oxide. The present invention relates to a lithium ion secondary battery comprising a silicon oxide and an electrolyte solution comprising a fluorinated acid anhydride.

Lithium ion secondary battery

Deterioration in cycle characteristics and battery swelling are improved. The lithium ion secondary battery of the present invention is characterized in comprising an electrolyte solution comprising a multifunctional monomer comprising two or more epoxy groups and a negative electrode comprising a binder comprising a polymer comprising a monomer unit comprising a functional group selected from the group consisting of &#x2014;OH, &#x2014;OM, &#x2014;COOH, &#x2014;COOM and &#x2014;COOCH, wherein M is a metal element, and n is an integer of 1 to 5.

An object of the present invention is to provide a lithium ion secondary battery having a high energy density and improved cycle characteristics. The present invention is related to an electrode for a power storage device comprising a negative electrode mixture layer comprising: (a) a negative electrode active material (-) comprising 1% or more of a material comprising Si as a constituent element; (b) a first polymer (-) coating the negative electrode active material and comprising vinylidene fluoride as a monomer unit; and (c) a negative electrode binder (-) comprising a second polymer that has a molecular weight of 80,000 or more and comprises at least one monomer unit selected from the group consisting of acrylic acid, acrylate salt, methacrylic acid, and methacrylate salt.

Electrode for power storage device and method for producing same

A purpose of one embodiment of the present invention is to provide a lithium ion secondary battery which has improved cycle characteristics and comprises a Si material in the negative electrode. The lithium ion secondary battery according to the present invention comprises a negative electrode comprising a negative electrode active material, a positive electrode comprising a positive electrode active material and an electrolyte solution, wherein the negative electrode active material comprises a Si material, and a ratio (Ia/Ib) of a peak intensity (Ia) at 290 eV to a peak intensity (Ib) at 285 eV is 0.7 or more in a C1s spectrum obtained by surface analysis of the negative electrode by X-ray photoelectron spectroscopy.

When the particle size of a silicon material used for a negative electrode active material are small, a large surface area thereof easily causes a side reaction between the active material and an electrolyte solvent to occur, and the cycle characteristics of a lithium ion secondary battery decrease. In order to improve the cycle characteristics, a lithium ion secondary battery according to the present invention is characterized in comprising a negative electrode comprising a material comprising silicon as a constituent element and a polyacrylic acid, and an electrolyte solution comprising a fluoroethylene carbonate, wherein the 50% particle size of the material comprising silicon as a constituent element is 2 &#x3bc;m or less.

Provided is a lithium ion secondary battery that has improved cycle characteristics and employs a silicon material as a negative electrode active material. The lithium ion secondary battery according to the present invention comprises a negative electrode comprising at least a copolymer and a material comprising silicon as a constituent element, wherein the copolymer comprises a monomer unit based on an ethylenically unsaturated carboxylic acid alkali metal salt and a monomer unit based on an aromatic vinyl and the copolymer comprises an alkali metal constituting the alkali metal salt in an amount of 1000 mass ppm or more.

A negative electrode active material constituting a lithium ion secondary battery having high energy density and excellent cycle characteristics, and a negative electrode and a lithium ion secondary battery comprising the same are provided. The present invention relates to a negative electrode active material comprising graphite particles and crystalline silicon particles, wherein a median diameter of the crystalline silicon particles is 0.7 &#x3bc;m or less, and a weight ratio of the crystalline silicon particles to the total weight of the graphite particles and the crystalline silicon particles is 1 wt % or more and 25 wt % or less.

Negative electrode active material and lithium ion secondary battery using the same

A lithium ion secondary battery excellent in cycle characteristics, comprising a high capacity negative electrode comprising a metal and/or a metal oxide as an active material is provided. The present invention relates to a lithium ion secondary battery comprising a positive electrode, a negative electrode, and an electrolyte solution, wherein the negative electrode comprises (a) a carbon material that can absorb and desorb lithium ions; at least one selected from the group consisting of (b) lithium metal and metals that can be alloyed with lithium and (c) metal oxides that can absorb and desorb lithium ions; and a polyacrylic acid, and the electrolyte solution comprises at least one disulfonic acid ester.

Growing community of inventors

Tokyo, Japan

Suguru Tamai