Elucidating the Li-Ion Battery Performance Benefits Enabled by Multifunctional Separators

The dissolution of transition metal ions from positive electrodes and loss of (both electroactive and transport) Li + ions seriously impair the durability of lithium ion batteries. We show herein that the improvement in the cycle life of lithium manganate spinel-graphite cells effected by multifunctional separators results from smaller interfacial resistances at both positive and negative electrodes, that can in turn be traced back to thinner, more uniform, and chemically different surface films, due to lessened parasitic reactions and a decreased accumulation of parasitic reaction products at electrode surfaces, as evidenced by HR-SEM, FIB-SEM, EDX, 19 F MAS NMR, and ICP-OES data.