Integrated design of multifunctional all-in-one polymer electrolyte membranes with 3D crosslinking networks toward high-performance lithium metal batteries

Gel polymer electrolytes (GPEs) are highly worthwhile for constructing high-energy-density lithium metal bat-teries (LMBs) because of their good flexibility and manufacturability. But, it is still challenging to prepare GPEs with excellent electrochemical performance, good flame retardancy, and good compatibility with electrodes for safe and dendrite-free LMBs application. Herein, a well-designed GPE with three-dimensional (3D) crosslinking network containing -C---N and -PO(OC2H5)2 functional groups (3D-ADCL) with synergistic effect is prepared via thermal-initiated in-situ polymerization. Concretely, the -PO(OC2H5)2 segment enhances the flame resistance of polymer electrolyte, and the -C---N segment grants improved Li-ion conductivity. In addition, the 3D crosslinking networks in the whole LMBs are incredibly favorable for improving the physical stability of both polymer electrolyte membrane/electrode bulks and electrolyte/electrode interface. Furthermore, the 3D-ADCL-based polymer electrolyte (3D-ADCL-PE) demonstrates an enhanced Li-ion transference number (tLi+) of 0.58 because the -C---N groups possess strong coordination with Li-ion and electrostatic repulsion with PF6- anion. It is also confirmed that the -C---N group can enable the formation of stable Li3N-rich solid electrolyte interphase (SEI) and high-quality cathode electrolyte interphase (CEI) layers to inhibit Li dendrite growth and stabilize the LiFePO4 cathode, respectively. Consequently, the 3D-ADCL-PE based LiFePO4/Li cells exhibit a remarkable ca-pacity of 106.4 mA h g- 1 at 6 C-rate with a high capacity retention of 90.3% after long 1000 cycles.