In-Cavity Lithium Deposition Enabled by Carbon Framework-Integrated Separator for Stable Low-Pressure Cycling

Practical implementation of Li metal anodes has been hindered by non-uniform, dendritic growth of Li, which causes continuous side reactions, internal short-circuiting, and early cell failure. Although applying external pressure has been reported to promote dense Li plating to some extent, the practical application of this approach remains limited. Herein, a carbon framework-integrated separator to regulate the plating-stripping behavior of Li at reduced external pressure is proposed. To ensure both high porosity and mechanical integrity, carbon nanofibers (CNFs) are employed as a model material for realizing the framework-integrated separator structure. CNFs are electrophoretically deposited onto the separator to achieve a uniform and mechanically robust layer, while preserving the intrinsic porous structure of the separator. Combined experimental and computational studies show that when assembled with a Li metal anode, the carbon framework-integrated separator enables kinetics-controlled "in-cavity" deposition, effectively guiding dense Li plating and accommodating plating-induced volume changes. As a result, a high-voltage (4.25 V) and high-capacity (4.0 mAh cm^-2) full cell exhibits stable cycling under low external pressure (0.26 MPa). This work provides a promising strategy for designing functional separators to realize practical high-energy-density Li metal batteries.