Electrochemical performance and chemical properties of oxidic cathode materials for 4V rechargeable Li-ion batteries

摘要

The systems Li{sub}(1+x)Mn{sub}(2-x)O{sub}(4-δ) and Li{sub}(1-x)Ni{sub}(1+x)O{sub}2 were studied as oxidic cathode materials for 4 V rechargeable Li-ion cells. From a comparison of the results it follows that the spinel system can be subdividedinto three regions: in region I (0≤x < 0.05) the electrochemical performance is unsatisfying due to a large volume reduction of about 7.5%, inducing stress, multiphase materials and capacity fading. Region II(0.05≤x≤0.2) contains the best cathodematerial with a composition near x = 0.1. The spinel framework is stable against Li extraction. In region III(0.2≤x≤1/3) the capacity is too low for an application in the 4 V region. In the system Li{sub}(1-x)Ni{sub}(1+x)O{sub}2 the highest capacity isobserved for LiNiO{sub}2 with x = 0. Experimental difficulties during material synthesis were overcome by suppression of the decomposition of LiNiO{sub}2 into Li{sub}(1-x)Ni{sub}(1+x)O{sub}2, Li{sub}2O and O{sub}2.