Ion-Permselective Polyphenylene Sulfide-Based Solid-State Separator for High Voltage LiNi0.5Mn1.5O4 Battery

The decomposition of commonly used commercial electrolytes under high voltage and the continuous side reactions at the graphite anode make the rapid capacity decay of LiNi0.5Mn1.5O4(LNMO)/graphite full cell during cycling. In this work, we adopt ion-permselective polyphenylene sulfide-based solid state separator (PPS-SSS) for LNMO batteries, PPS-SSS can effectively prevent the proton diffusion, block the HF generated on the LNMO cathode from attacking the anode SEI layer, and mitigate the Mn2+ transfer. The PPS-SSS with anodic polyethylene (PE) protection (PE-PPS-CSSS) significantly improved the cycling performance of LNMO batteries. In the LNMO/Li half-cell system, 93% capacity retention rate can be achieved after 140 cycles at 0.5 C, and in the LNMO/graphite full-cell system, 85% of the initial capacity can be maintained after 100 cycles. Moreover, flight secondary ion mass spectrometry (TOF-SIMS) and X-ray photoelectron spectroscopy (XPS) are applied to explore the interfacial reactions of LNMO/graphite batteries and reveal the key mechanism for the stable cycling using PPS-SSS.