Thermal stability and performance studies of LiCo1/3Ni1/3Mn1/3O2 with phosphazene additives for Li-ion batteries

Phosphazene derivatives as flame retardant (FR) additives were investigated to evaluate their thermal stability and performance in Li-ion batteries. Hexamethoxy-cyclo-tri-phosphazene (HMTP) and hexaethoxy-cyclo-tri-phosphazene (HETP) were added to the electrolytes of the test cells. Thermal stability and the performance influenced by the additives were evaluated using cathodes prepared with LiCo1/3Ni1/3Mn1/3O2. Concentration dependence on FR properties, rate capabilities, and cycle life was analyzed. The additives formed a surface layer on the cathode. The layer on the cathode reduced electrochemical reaction resistance, which improved the performance of the cells. Optimization studies show that HETP has better FR properties than does HMTP.