Functionalizing separator for dual application in liquid and solid-state lithium metal batteries: Achieving stable cycling from − 20 °C to 60 °C

Inhomogeneous lithium deposition and dendrite growth severely restrict the achievable energy density of both solid-state and liquid lithium metal batteries (LMBs). While the application of functional separator materials can effectively mitigate these issues, existing research predominantly focuses on either liquid or solid-state batteries, with limited dual application in both systems. Herein, in this work, an Al 2 O 3 @bacterial cellulose (Al 2 O 3 @BC) separator is proposed to realize the dual application from liquid to a wide-temperature range of solid-state LMBs. X-ray Photoelectron Spectroscopy (XPS) and High-Resolution Transmission Electron Microscope (HRTEM) analyses revealed that the an in-situ formed Li-Al-O protective layer on the lithium metal surface facilitated the uniform diffusion and nucleation of lithium ions (Li + ). Consequently, both liquid and polyethylene oxide (PEO)-based solid-state lithium-symmetric batteries assembled with Al 2 O 3 @BC can operate for over 2000 h at a current density/ capacity of 0.1 mA cm −2 / 0.1 mAh cm −2 . The NCM523 full cell with Al 2 O 3 @BC delivers 150.3 mAh g −1 at 0.2C after 120 cycles. More importantly, the ionic conductivity (4.63 × 10 −4 S cm −1 ) in solid-state batteries is also significantly promoted, and the LFP full cells demonstrating stable cycling across a broad temperature range of − 20 °C to 60 °C.