3D Porous Tin Created by Tuning the Redox Potential Acts as an Advanced Electrode for Sodium‐Ion Batteries

Abstract Sodium‐ion batteries (SIBs) have attracted significant research interest for large‐scale electric energy storage. However, anodes with good rate capability and long cycle life are still lacking. Here, a three‐dimensional (3D) porous Sn on Cu foil (Sn/Cu) is prepared by tuning the redox potential of Cu + /Cu with a ligand of thiourea to trigger the replacement reaction between Cu and Sn 2+ . The as‐synthesized Sn/Cu is used as an integrated porous electrode and can be directly applied as an advanced freestanding electrode for SIBs. Such a unique structure can efficiently relieve the strain caused by sodiation/desodiation and benefit penetration of the electrolyte and diffusion of Na + . This is a merit of its large reversible capacity of about 700 mAh g −1 at 2500 mA g −1 for 400 cycles. A full battery of Sn/Cu//Na 3 (VO 0.5 ) 2 (PO 4 ) 3 F 2 is constructed, which presents a high energy density of 311.7 Wh kg −1 and long lifespan of 200 cycles. This facile synthesis strategy and good electrochemical performance will encourage more investigations into structure design of functional materials.