Sanyo Electric Co., Ltd.

Toshio Yanagida

Maruo Kamino

Hiroshi Minami

Taizou Sunano

Atsushi Fukui

Toshiyuki Nohma

Yasuhiro Yamauchi

Naoya Nakanishi

Takuya Sunagawa

Yoshinobu Okumura

Shouichirou Sawa

A nonaqueous secondary batteryof the invention has an active material compound layerdeposed over at least one face of a collectormade of metal foil and is equipped with a positive electrodehaving a portionin a part of which metal is exposed. The positive electrodetogether with the exposed-metal portionfaces a negative electrodethrough an interposed separator, and on that part of the exposed-metal portionthat faces the negative electrodethrough the interposed separatorthere is formed a protective layermade of a material whose electronic conductivity is lower than that of the metal and which moreover is non-insulative. With such nonaqueous secondary battery, should part of an electrode pierce the separator and contact with the other electrode, the battery will be gently discharged, thereby averting abnormal heat generation by the battery and additionally enabling the battery's abnormality to be sensed by the equipment via the fall in battery voltage. Thus, there is provided a nonaqueous secondary battery of excellent safety that can prevent abnormal heat generation due to a short circuit caused by burr, powder or the like piercing the separator.

Nonaqueous secondary battery

A lithium secondary battery having high capacity and good charge-discharge cycle performance is provided. The lithium secondary battery includes a negative electrode () containing silicon as a negative electrode active material, a positive electrode () containing a positive electrode active material, and a non-aqueous electrolyte. The positive electrode active material is a lithium-transition metal composite oxide including a layered structure represented by the chemical formula LiNiMnCoO, where a, x, y, and z satisfy the expressions: 0&#x2266;a&#x2266;1.3, x+y+z=1, 0&#x3c;x, 0&#x2266;y&#x2266;0.5, and 0&#x2266;z.), and the theoretical electrical capacity ratio of the positive electrode to the negative electrode (positive electrode/negative electrode) is 1.2 or less.

Lithium secondary battery

Charge-discharge cycle performance is improved in a lithium secondary battery that adopts a thin film made of silicon or a silicon alloy as its negative electrode active material and has a wound electrode structure. The lithium secondary battery includes: a negative electrode having a current collector and a thin film made of silicon or a silicon alloy as a negative electrode active material, the thin film provided on the current collector; a positive electrode; a separator; the positive and negative electrodes being overlapped with the separator interposed therebetween, and the positive and negative electrodes and the separator being wound around to form an electrode assembly; a non-aqueous electrolyte; and a battery case accommodating the electrode assembly. The ratio of theoretical capacity per unit area of the negative electrode to charge capacity per unit area of the positive electrode is within the range of from 1.9 to 4.4.

Growing community of inventors

Tokushima, Japan

Toshio Yanagida