Constructing a multi-functional polymer network for ultra-stable and safe Li-metal batteries

The practical application of lithium (Li) metal electrodes is impeded by Li dendrite growth and unstable solid electrolyte interphase (SEI). Herein, a multi-grafting polymer network, poly(dimethyl siloxane)-g-[poly(poly (ethylene glycol) methyl ether methacrylate)-r-sodium poly(p-styrene sulfonate)] (PPS), is chemically synthesized from reversible addition-fragmentation chain transfer (RAFT) polymerization. With integrated stretchability, ionic conductivity, and mechanical robustness, it serves a dual role to stabilize the Li electrode. As artificial SEI layer, the PPS enables superior electrochemical performance in half cells, symmetric cells, and full cells (PPS@Li/LiFePO4, capacity retention of >70% after 600 cycles). Utilized as solid polymer electrolyte (SPE), the all-solid-state Li/SPE/LiFePO4 full cell delivers excellent cycling performance with an unprecedented capacity retention of 90% over 1,700 cycles at 0.5 C and 81% over 1,000 cycles at 1.0 C. With high-voltage LiNi0.8Mn0.1Co0.1O2 (NMC811) as cathode, the Li/SPE/NMC811 cell exhibits an initial discharge capacity of 162.2 mAh g-1 with a capacity retention of 72% after 200 cycles. The assembled solid-state Li/SPE/LiFePO4 pouch cell with SPE exhibits stable cycling performance over 200 cycles with a capacity retention of 75% and still operates well even after curling, folding, and cutting, demonstrating great potential for achieving ultra-safe and high energy density batteries.

Automated summary

A polymer network called PPS is synthesized and utilized as an artificial solid electrolyte interphase (SEI) layer to stabilize lithium metal electrodes. It shows excellent electrochemical performance and cycling stability in various cell configurations.