Uniform lithium deposition and enhanced stability in lithium metal batteries enabled by a flexible, ultrathin, and lithophilic SnS2@nanocellulose interlayer.

Abstract

Lithium metal is recognized as a leading candidate for anodes in next-generation high-energy-density batteries. However, challenges such as Li dendrite growth and instability of the solid electrolyte interface (SEI) persist. Conventional artificial interface construction via coating often diminished effectiveness due to binders reducing activity. Herein, this study utilized nanofibrillar cellulose as a one-dimensional template to construct a nanocellulose-based flexible, ultrathin (≈1 μm), lithophilic SnS₂ nanopaper as an interlayer for separators. This innovative interlayer possesses self-supporting properties and mechanical flexibility while eliminating the need for activity-reducing binders. The uniform mesoporous structure of nanocellulose substrate ensures consistent lithium-ion flux, enhancing electrochemical stability. Within this framework, SnS₂ spontaneously forms a continuous SEI layer on the lithium anode surface, primarily consisting of Li₂S and Li₇Sn₂. This SEI layer, distinguished by its high ionic conductivity and excellent lithophilicity, significantly reduces nucleation overpotential and facilitates homogeneous lithium plating and stripping. Therefore, symmetric cells equipped with the SnS₂ nanopaper interlayer demonstrate exceptional durability, sustaining operation for over 1400 h at 1 mA cm^-2 with a capacity of 1 mAh cm^-2. Additionally, Li||LiFePO₄ cells exhibit remarkable cycling stability and rate performance. This work demonstrates the efficacy of the multifunctional interlayer in SEI modulation and dendritic growth inhibition.