Regulating lithium deposition via bifunctional regular-random cross-linking network solid polymer electrolyte for Li metal batteries

Abstract

The low coulombic efficiency and poor cycle performance deriving from uncontrolled growth of dendrites have caused a serious obstacle to the practical application of lithium metal. Herein we propose a bifunctional regular-random dual cross-linking network solid polymer electrolyte (RRa-SPE) for dendrite-free all-solid-state lithium metal batteries. Under the synergistic effect of regular polymerization skeleton and random cross-linking network, the RRa-SPE effectively regulates the lithium deposition and facilitates the generation of a highly homogeneous and robust solid-electrolyte interphase (SEI) layer on lithium metal. Besides, this RRa-SPE shows benign ionic conductivity of 4.36 × 10−4 S cm−1 (at 30 °C), high lithium ion transference number of 0.76 and enhanced mechanical strength. The Li/RRa-SPE/Li symmetric cell maintains low and stable voltage polarization (0.15 V) after circulating for 1200 h at 0.5 mA cm−2. Improved LiFePO4/RRa-SPE/Li cell exhibits excellent rate capability and prominent cycle performance with a capacity retention of 99.6% after 240 cycles at 0.5 C at 30 °C.