Gs Yuasa International Ltd.

Mariko Kohmoto

Toshiyuki Nukuda

Tokuo Inamasu

Toru Tabuchi

Hiroe Nakagawa

Akihiro Fujii

Yoshinobu Yasunaga

Yuta Kashiwa

Yukiko Fujino

Yohei Shibata

Takashi Egawa

Tokuo Inamatsu

The positive active material is a positive active material for a lithium secondary battery, including a lithium transition metal compound that has an olivine crystal structure and contains at least Ni, Fe, and Mn as transition metal elements, wherein when the sum of mole atoms of Ni, Fe, and Mn of transition metal elements contained in the lithium transition metal compound is expressed as 1, and the mole atomic ratios of Ni, Fe, and Mn are represented by a, b, and c (a+b+c=1, a&#x3e;0, b&#x3e;0, c&#x3e;0), respectively, the following is satisfied: 0.85&#x2266;c&#x2266;0.92 and 0.3&#x2266;a/(a+b)&#x2266;0.9.

Positive active material for lithium secondary battery and lithium secondary battery

It is an object of the present invention to provide a positive electrode material having a large ratio of the discharge capacity around 4 V to the total discharge capacity including the discharge capacity at 4V or lower while making the discharge capacity around 4 V sufficient, for the purpose of providing a lithium secondary battery using a lithium transition metal phosphate compound excellent in thermal stability, utilizing the discharge potential around 4V (vs. Li/Li) that is higher than the discharge potential of LiFePO, and being advantageous with respect to the detection of the end of discharge state, and a lithium secondary battery using the same. The present invention uses a positive active material for a lithium secondary battery containing a lithium transition metal phosphate compound represented by LiMnFeCoPO(0.1&#x2266;x&#x2266;0.2, 0&#x3c;y&#x2266;0.2).

Positive active material for lithium secondary battery, and lithium secondary battery

The invention provides a polyanion-based positive active material which can improve storage stability (especially, high temperature storage stability), charge and discharge cycle performance and the like of a lithium secondary battery, and a lithium secondary battery using the same. The positive active material for a lithium ion secondary battery contains lithium iron cobalt phosphate represented by the general formula: LiFeCoPO(0&#x3c;x&#x2266;0.019, 0&#x2266;y&#x2266;1.2). By using the positive active material for a lithium secondary battery, high temperature storage stability and charge and discharge cycle performance can be improved in comparison with a case where LiFePOcontaining no Co is used. By using the positive active material, a lithium ion secondary battery can be suitable for applications in fields of electric automobiles and industrial batteries in which long lives, high capacities, and high output powers are required.

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Kyoto, Japan

Mariko Kohmoto