In situ construction of Li3N-enriched interface enabling ultra-stable solid-state LiNi0.8Co0.1Mn0.1O2/lithium metal batteries

Solid polymer electrolytes (SPEs) are considered as the most promising solid-state electrolytes for next-generation lithium (Li) batteries with high safety and electrochemical performance. Whereas the interfacial side reactions between SPEs and Li metal anode hinder the development of SPEs in solid-state lithium metal batteries (SLMBs). Herein, we propose a g-C3N4 nanosheets (GCNs) reinforced poly(vinylidene fluoride) (PVDF-GCN) composite polymer electrolyte with high ionic conductivity of 6.9 × 10−4 S cm−1 and low activation energy (0.192 eV). The GCNs react with Li metal to in situ produce a Li3N-enriched SEI during cycling, which significantly suppresses the continuous side reactions and ensures rapid charge-transfer between PVDF-GCN SPEs and Li metal anode. In addition, the GCNs present a strong adsorption ability to the residual N, N-dimethylformamide molecule, which greatly enhances the electrochemical stability of PVDF-GCN SPEs. As a result, the Li symmetrical cell stably cycled over 2200 h. Moreover, the SLMBs using LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode achieve excellent cycling stability for more than 1700 cycles at 1 C and a high discharge capacity of 108 mAh g−1 at 5 C. This work provides novel insights into the construction of a stable SPEs/Li interface for long lifespan SLMBs.