Integrated Solid Sodium Metal Battery with Reinforced Polymer Electrolyte and Presodiated 3D InSb@Cu Anode

Solid polymer electrolytes (SPEs) are a promising solution for solid‐state sodium metal batteries (SSMBs) due to their molecular tunability, non‐leakage properties, and ease of processing, but suffer from low room‐temperature (RT) ionic conductivity, poor mechanical strength, and inherent sodium (Na) anode interfacial incompatibility. In this study, an integrated SSMB configuration is introduced by pairing an ultrathin, self‐polymerized SPE membrane with the porous 3D InSb@Cu substrate. The Poly(DOL)‐based (PDOL) SPE is reinforced by aluminum trifluoromethanesulfonate (Al(CF 3 SO 3 ) 3 )‐anchored bacterial cellulose (BC), designated as ABC‐PDOL, achieving superior mechanical strength (15.21 MPa), high ionic conductivity (1.8×10 −4 S cm −1 at 30 °C), and enhanced Na + transference (0.67). Additionally, the InSb@Cu substrate provides abundant Na–In/Na–Sb sodiophilic sites, enabling dendrite‐free Na deposition up to 6 mAh cm −2 and interfacial compatibility with ABC–PDOL electrolyte even under a high current density of 1.4 mA cm −2 . When assembled into a layer‐stacked pouch cell, the 3D Na‐InSb@Cu|ABC–PDOL|Na 3 V 2 (PO 4 ) 3 configuration demonstrates robust cycling stability within a wide temperature range (25–80 °C) as well as the rate behavior up to 5 C. Operando XRD‐EIS‐DRT characterization further confirms the reversible lattice evolution of the cathode and enhanced Na + diffusion kinetics at the 3D alloy/SPE interface, highlighting the feasibility of the proposed SSMB design.