An in-situ synergistic enhancement strategy from g-C3N4 and PDOL composite solid electrolyte on the interface stability of solid-state lithium battery

The interface stability of lithium metal anode/electrolyte has been an important problem hindering the development of solid-state lithium batteries. In this work, we proposed to in-situ recombine poly(1,3-dioxolane) (PDOL) with g-C3N4 to improve the ion transport ability of PDOL solid electrolyte and simultaneously improve the electrolyte/electrode interface stability. The composite solid electrolyte with a thickness of about 23 μm exhibits good electrochemical performances when the introduced g-C3N4 mass is 0.3 wt% of PDOL. The ionic conductivity of the solid electrolyte is enhanced from 3.16 × 10−4 S/cm to 4.14 × 10−4 S/cm, the ion migration number increases from 0.32 to 0.45, and the electrochemical window widens from 4.6 V to 4.8 V under the modulation of g-C3N4. The stability of Li metal anode was significantly improved owing to the introduction of g-C3N4 in the composite solid electrolyte, the assembled lithium-symmetric cells and NCM622/Li cells exhibites more stable cycling performances than those assembled with pure PDOL electrolyte. The solid NCM622/Li cell with PDOL/g-C3N4 composite solid electrolyte can be cycled for 200 times at 0.3 C with a capacity retention of 21 % higher compared with the cell with pure PDOL solid electrolyte. This composite solid electrolyte can also be directly used as artificial SEI film on the lithium metal surface via in-situ polymarization, which further confirmed that the interface stability of lithium anode and electrolyte was enhanced by the synergistic effect of PDOL and g-C3N4 bicomponents.