A Free‐Standing, Lightweight Lithium Anode Enabling High‐Energy Solid‐State Lithium‐Metal Batteries

Abstract Limiting the amount of lithium (Li) metal anode is critical for achieving high‐energy density in solid‐state Li‐metal full cells. However, the inherently low mechanical properties of bare Li metal limit the fabrication of freestanding ultrathin films. Herein, a free‐standing, lightweight, and robust Li‐limited anode with a thickness of 25 µm is designed to enable high‐energy‐density solid‐state full cells. This Li‐limited anode is fabricated by evaporating a controlled amount of Li metal on cellulose fiber matrix coated with silver (Ag) nanoparticles, denoted as cellulose@Ag/limited Li (CALL). Notably, CALL exhibits an extra low nucleation overpotential (2.2 mV) in the solid polymer electrolyte based Li symmetric cells and demonstrates stable cycling for over 300 h at 0.2 mA cm −2 . Coupled with the high‐mass‐loading LiNi 0.8 Mn 0.1 Co 0.1 O 2 cathode, the solid‐state Li‐metal full cells present an initial specific capacity of 200 mAh g −1 and sustain stable cycling over 100 cycles. The pouch cell delivers a high energy density of 401.1 Wh kg −1 . Furthermore, the in situ Li deposition observation and in situ stress monitoring reveal the uniform strain distribution in CALL, underpinning its superior electrochemical performance. This work proposes a simple yet effective method for fabricating ultrathin Li films, advancing the development of high‐energy‐density solid‐state Li‐metal full cells.