THE LI1+XMN2O4/C ROCKING-CHAIR SYSTEM - A REVIEW

The new emerging rechargeable battery technology, called ''rocking-chair'' or ''Li-ion'', that uses an intercalation compound for both the positive and negative electrodes is safer than the battery technology using pure Li metal. In this paper we review our study of the Li-ion type battery based on the spinel Li1+xMn2O4 positive electrode and the negative carbon electrode. First we give a brief history of rocking-chair batteries, followed by a description of how to select and optimize intercalation materials for such a type of cell and then we present the main findings which allowed us to bring this battery system from concept to realization. Among the main findings are: (1) the use of the second Li intercalation plateau of the spinel as a Li reservoir; (2) the discovery of a new electrolyte composition resistant against oxidation up to 5 V; and (3) the ability to reversibly intercalate 0.9 Li ions into graphite at high rate with a small reversible loss. Based on these findings, AA research prototype cells with enhanced safety characteristics were constructed. We report on the performance of these cells, compare our results with existing or emerging battery technologies such as NiCd or Ni metal hydrides, respectively, and discuss problems inherent to the Li-ion technology.