Kabushiki Kaisha Toyota Chuo Kenkyusho

Akihiko Koiwai

Tohru Shiga

Kensuke Takechi

Yoshitsugu Kojima

Satoru Yamamoto

Nobuaki Suzuki

Shigehiro Kawauchi

A lithium secondary battery exhibiting very high safety, which is ensured by restraining both the generation of flammable gas caused by the decomposition of an electrolyte, and the emission of oxygen from a positive active material even during overcharging. The lithium secondary battery includes a positive electrode of which an active material is a lithium transition metal composite oxide, a negative electrode of which an active material is a carbon material, and a nonaqueous electrolyte containing an organic solvent in which a lithium salt is dissolved. The nonaqueous electrolyte contains at least one kind of conductive polymer-forming monomers which have an alkyl group and is electrochemically polymerizable on the positive electrode within a battery operation voltage, and at least one kind of film-forming agents which electrochemically decompose within the battery operation voltage to form films on a surface of the negative electrode.

Lithium secondary battery

A nonaqueous electrolytic solution for a battery, which contains a supporting electrolyte which reacts with water to produce an acid; and a complex-forming compound which forms an inert complex by reacting with water and a supporting electrolyte to prevent acid generation.

Nonaqueous electrolytic solution for battery and nonaqueous electrolytic

A negative electrode material capable of absorbing and desorbing lithium is comprised of a mixture of coke and graphite. The amount of graphite in the mixture is near to that which induces percolation transition. Preferably, the amount of graphite in the mixture is 2 to 37 wt % relative to the total amount of the coke and graphite. The coke may be prepared by heating raw coke from oil or coal at 500 to 900.degree. C. The coke may be 0.06 or more in the atomic ratio of hydrogen to carbon and 0.003 or more in the atomic ratio of oxygen to carbon. The graphite may be 0.5 .mu.m to 30 .mu.m in a mean particle size. Lithium secondary batteries comprising the negative electrodes have a large discharge capacity.

Growing community of inventors

Aichi, Japan

Akihiko Koiwai