STABILITY OF LITHIUM ION SPINEL CELLS. PT.3. IMPROVED LIFE OF CHARGED CELLS

Irreversible capacity losses in lithium ion manganese spinel cells during 60 C storage were investigated in the charged state and a mechanism proposed based on acid generation to explain the origin of irreversible loss. Various approaches such as surface, structural, electrode formulation, and electrolyte modification were applied to address the instability issue. Based on an understanding of the mechanism, a method of coating the spinel surface with a carbonate layer was developed to minimise the detrimental effect of acid generation in cells. As a result, irreversible losses were reduced from > 70% after 4 weeks of storage at 60 C to about 20%. 23 refs.