ELECTROCHEMICAL PERFORMANCE AND CHEMICAL-PROPERTIES OF OXIDIC CATHODEMATERIALS FOR 4 V RECHARGEABLE LI-ION BATTERIES

The systems Li1-xMn2-xO4-delta acid Li1-xNi1+xO2 were studied as oxidi c cathode materials for 4 V rechargeable Li-ion cells. From a comparis on of the results it follows that the spinel system can be subdivided into three regions: in region I (0 less than or equal to x < 0.05) the electrochemical performance is unsatisfying due to a large volume red uction of about 7.5%, inducing stress, multiphase materials and capaci ty fading. Region II (0.05 less than or similar to x less than or simi lar to 0.2) contains the best cathode material with a composition near x = 0.1. The spinel framework is stable against Li extraction. In reg ion III (0.2 less than or equal to x less than or equal to 1/3) the ca pacity is too low for an application in the 4 V region. In the system Li1-xNi1+xO2 the highest capacity is observed for LiNiO2 with x = 0. E xperimental difficulties during material synthesis were overcome by su ppression of the decomposition of LiNiO2 into Li1-xNi1+xO2, Li2O and O -2. (C) 1998 Elsevier Science S.A. All rights reserved.