Novel Cathode Materials Based on Organic Couples for Lithium Batteries

ABSTRACTThe electrochemical reduction of the oxocarbons: squarate, croconate and especially rhodizonate lithium salts have been studied in all solid state lithium batteries. Lithium rhodizonate cells were tested on cycling in the 1.5 – 3.5 V potential range The reduction of lithium rhodizonate occurs in two waves of two electrons. The number of electrons transferred in reduction on the first cycle was around 3.5 based on a capacity of 515 mA.h.g−1 and a discharge depth of 87 %. This process is quite reversible but we observed a fast decline of the capacity on cycling. This loss of capacity may be attributed to residual water in the salt. The reduction of the lithium croconate occurs at a potential of 1.8 V in a quasi-irreversible process. We could not observe the reduction of lithium squarate which occurs in the potential range where the lithium is inserted in carbon black. We also report an investigation on rhodizonate salts of transition metals. The best results, in term of capacity, on the 1.5 – 3.5 V potential range, were obtained with copper rhodizonate which exhibits a capacity of 579 mA.h.g−1 on the first discharge.