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 nextgeneration 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) (PVDFGCN) composite polymer electrolyte with high ionic conductivity of 6.9 x 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.

Automated summary

In this study, a GCNs-reinforced PVDFGCN composite polymer electrolyte with high ionic conductivity and low activation energy is proposed. The GCNs react with Li metal to form a Li3N-enriched SEI layer, effectively suppressing side reactions and ensuring rapid charge transfer. Moreover, the GCNs have a strong adsorption ability, enhancing the stability of the electrolyte. The electrolyte exhibits stable cycling for over 2200 hours.