Dendrite-free lithium metal battery enabled by mesoporous silica host layer mediated cellulose/PVDF Janus separator

The commercialization of lithium metal batteries (LMBs) is encountering significant challenges due to the electrolyte incompatibility and poor mechanical properties of polyolefin separators, as well as the hazardous growth of lithium dendrites at the anode. Simultaneously, the development of safe and environmentally-friendly separators has become a central focus in rechargeable battery technology. In this study, we introduce a novel Janus separator (CP@SiO₂), featuring a composite structure with cellulose paper (CP) as the base layer and electrospun polyvinylidene fluoride (PVDF) nanofibers as the top layer. The nanofibers are uniformly coated with mesoporous SiO₂ nanoparticles through hydrogen bonding. The CP@SiO₂ separator leverages its three-dimensional lithium-ion channels and rigid ceramic particles to enhance electrolyte retention and stabilize lithium metal anodes (LMA). Shielded by this separator, LMA exhibits an impressive cycling performance, enduring a current density of 2 mA cm^-2 for 350 h without short-circuiting, effectively doubling the cycle life compared to conventional PP separators. Furthermore, the Li/LiFePO₄ cell utilizing the CP@SiO₂ separator demonstrates a high capacity of 101 mAh·g^-1 at 5C, with 90 % capacity retention after 1000 cycles. This outstanding electrochemical performance is attributed to the compatible anode/separator interface and the effective inhibition of lithium dendrite growth. The research presented in this work capitalizes on a synergistic configuration design, offering a promising pathway towards the development of high-safety and advanced lithium-ion separators.