Rigid-flexible S-VNs@PAN Janus separator with engineered nanochannels for stable lithium metal batteries

Lithium metal batteries (LMBs) hold great promise for next-generation energy storage, yet their practical implementation is hindered by uneven Li + flux distribution and unstable lithium deposition induced by conventional separators. Herein, we report a rigid-flexible Janus separator by integrating size-engineered small vermiculite nanosheets (S-VNs) with an electrospun polyacrylonitrile (PAN) scaffold. Through ion exchange, exfoliation, and high-pressure homogenization, S-VNs with reduced lateral dimensions are constructed to form accessible interlayer nanochannels and a negatively charged inorganic interface. The S-VNs layer simultaneously shortens ion-transport pathways, regulates anion migration through electrostatic interactions, and homogenizes Li + flux at the electrode/separator interface. Benefiting from this integrated ion-regulating architecture, the S-VNs@PAN separator exhibits enhanced Li + transport selectivity ( t L i + = 0.76 ± 0.02), improved ionic conductivity (1.636 ± 0.013 mS cm −1 ), and excellent thermal dimensional stability. Consequently, Li||Li symmetric cells enabled by the S-VNs@PAN separator achieve stable cycling over 1600 h with suppressed polarization growth, while LiFePO 4 ||Li full cells maintain improved reversibility during long-term cycling compared with PAN and commercial Celgard separators. This work highlights the importance of nanosheet dimension engineering in constructing functional separator interfaces and provides a rational strategy for stabilizing lithium metal batteries.