Investigation of graphite intercalation compounds of some transition metal chlorides as the cathodematerials for lithium rechargeable battery

某些过渡金属氯化物的石墨层间化合物(GIC)具有刚性的层状结构和较高的电子导电性。为了将过渡金属氯化物GIC应用于锂二次电池正极材料中，研究了过渡金属氯化物GIC中锂的电化学嵌入。研究了第一级五氯化钽GIC在1MLiClO4/碳酸亚丙酯电解液中的电化学锂行为。在放电开始时，证实了从第一阶段到更高阶段的降解，这表明Ta物种从主体材料中脱嵌。在主体材料或电解液中的五价钽物种被认为被还原到较低的氧化态。这些结果表明，氯化钽的GIC不适合作为锂二次电池的正极材料。然而，有人建议，锂可以插入到含有过渡金属的较高阶段的GIC中，这些过渡金属可以在不破坏层状结构的情况下采取各种价态。

Graphite intercalation compounds (GIC) of some transition metal chlorides have rigid layered structures and high electronic conductivity. In this study, electrochemical insertion of lithium into the GICs of some transition metal chlorides was investigated in order to apply the GICs to the cathode materials for lithium secondary batteries.The electrochemical lithiation behavior of a 1 st stage GIC of tantalum pentachloride, C_<20>TaCl_5, was investigated in 1 M LiClO_4/propylene carbonate electrolyte. The degradation of the stage number from 1 st to higher stages was confirmed at the beginning of the discharge, indicating that the deintercalation of tantalum species from the host material occurred. The pentavalent tantalum species, which is in the host material or in the electrolyte, were considered to be reduced to the lower oxidation states. On the other hand, the charge was impossible.These results showed that the GICs of tantalum chloride are not suit able for cathode materials for lithium secondary batteries. However, it was suggested that lithium can be inserted into the higher stage GICs containing the transition metals which can take various valence states without destruction of the layered structures.