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TITLE Development of Lithium-ion Battery Iron-related Cathode Material Production Technology
(Joint Program to Promote Technological Development with the Private Sectors)
in Mitsui Engineering & Shipbuilding Co., Ltd.

A new type of cathode material, LiFePO4, which is found to be suitable to hybrid electric vehicle lithium-ion battery applications, has developed since 2002 in terms of eliminating CO2 generation. The main results of tests carried out in 2003 are summarized below, and our participation in this program was terminated in 2003:

1. A novel production process for ultra-fine perticles of modified LiFePO4 cathode material with other metal elements, on which a thin layer of conductive carbon uniformly deposited (several nm in thickness) in order to improve electro-conductivity and Li+ ion transportation, has been established. A lithium-ion battery using a cathode material carbon-deposited and modified by another metal element demonstrated a very good cycle performance similar to that of a conventional LiCoO2 cathode, along with the same capacity, and good enough rate capability that was maintained at a discharge rate as high as 5C (= a rate at which the whole capacity was discharged for 1/5h).

2. Technologies for bulk production of the LiFePO4 cathode material carbon-deposited and modifified by another metal element were established, through development of a series of batch processes including preparation of the precursor and calcinations.

3. Technologies for production of test cells of a laminated-type lithium-ion battery comprising a coated thin film of the developed LiFePO4 cathode, and evaluation of their performance were acquired, in order to develop a renewal cathode with higher performance and control its properties.