Lithium-ion secondary battery

摘要

The purpose of the present invention is to provide a lithium-ion secondary battery with small internal resistance, excellent load characteristics and low reduction in capacitance due to repeated discharge and charge.;The lithium-ion secondary battery of the present invention attaining the above purpose comprises a positive electrode, negative electrode and electrolyte; said positive electrode and negative electrode are configured by binding an active material layer, including an electrode active material and a binder, to a collector; the binder used for at least one of the positive electrode or negative electrode includes polymer particles; and the polymer particles satisfy the following properties:
swelling degree in the electrolyte of a sheet-like molded body, obtained by pressure molding of only the polymer particles, is 5 to 50%, and lithium ion conductivity of the sheet-like molded body swollen by the electrolyte is 1×10−4 S·cm or more.

主权项

1. A lithium-ion secondary battery comprising a positive electrode, a negative electrode and an electrolyte, said positive electrode and negative electrode being configured by binding an active material layer, including an electrode active material and a binder, to a collector, wherein
the binder used for at least one of the positive electrode or negative electrode includes polymer particles comprising a cross-linked nitrile group containing polymer composed of a copolymer of at least a nitrile group containing monomer and a monomer having a carbon-carbon double bond and an epoxy group, or a cross-linked polymer having a polyalkylene oxide chain in its main chain composed of a copolymer of at least a monomer containing an epoxy and a monomer having a carbon-carbon double bond and an epoxy group, and wherein the polymer particles satisfy the following properties: swelling degree of a sheet-like molded body, which is obtained by pressure molding of only the polymer particles, in an organic electrolyte obtained by dissolving a lithium salt into carbonates, is 5 to 50% as an increase in length, and lithium ion conductivity of the polymer particles swollen by the organic electrolyte is 1×10−4 S·cm or more, and when the nitrile group is present, the ratio of nitrile group containing monomer unit in the polymer is 30 to 95 wt %.