Improved discharge characteristics of tunnel-containing manganese oxide electrodes for rechargeable lithium battery applications

摘要

Li{sub}xMnO{sub}2 made from Na{sub}(0.44)MnO{sub}2 has an unusual tunnel structure that allows ion insertion processes to occur with minimal strain. It cycles very reversibly at an average voltage of about 3.2 vs. Li without undergoing phase conversion. The stability of this material makes it a promising candidate for use in electric vehicle applications, which not only have severe cost constraints, but also require long cycle life and abuse-tolerance. In practical lithium cells, however, the demonstrated capacity is typically less than the predicted 200 mAh/g for Li{sub}xMnO{sub}2 cathode materials. Attrition-milling of conventionally-made Li{sub}xMnO{sub}2 and glycine-nitrate combustion synthesis have been used to produce powders with average particle size below 1 μm, improved rate capability, and a 15% improvement in utilization. Up to 55% of the Mn in Li{sub}xMnO{sub}2 with the Na{sub}(0.44)MnO{sub}2 structure can also be replaced with Ti. Ti-doped analogs have modified discharge characteristics, with some exhibiting better utilization between set voltage limits than the parent compound.