Hydroxyl-rich single-ion conductors enable solid hybrid polymer electrolytes with excellent compatibility for dendrite-free lithium metal batteries

Polyethylene oxide (PEO) based solid polymer electrolytes (SPEs) are promising candidates for constructing the safety and high-performance of lithium metal batteries (LMBs). However, a number of obstacles have limited its further application, such as low ionic conductivity , undesired mechanical properties , and low lithium-ion transference number ( t Li + $t_{{\text{Li}}^{+}}$ ). Herein, a hydroxyl-rich single conductor polymer (lithium sulfonated polyvinyl alcohol , SPVA-Li) was introduced as a polymeric filler into PEO SPEs network via a simple and scalable solution casting method to fabricate the composite SPEs. The hydrogen bond interactions between SPVA-Li and PEO enable the polymer chains to be more disordered that effectively suppress PEO crystallization, endowing the SPVA-Li SPEs with high ionic conductivity (1.76 × 10 −4  S cm −1 ) and t Li + $t_{{\text{Li}}^{+}}$ (0.59) at 60 °C. Moreover, such cross-linking structures also can significantly improve the mechanical strength and thermal stability of the SPVA-Li SPEs. These performances are all superior to the PEO SPEs. Thus, based on the composite SPEs, Li/Li symmetric cells run for 400 h without any short circuits, and the LiFePO 4 /Li batteries also can be stably operated for 100 cycles at 0.2 and 0.5 C rates, respectively. These merits enable the SPVA-Li SPEs to be very promising for developing high-performance LMBs.