Synergetic Sn Incorporation‐Zn Substitution in Copper‐Based Sulfides Enabling Superior Na‐Ion Storage

Abstract Transition‐metal sulfides have been regarded as perspective anode candidates for high‐energy Na‐ion batteries. Their application, however, is precluded severely by either low charge storage or huge volumetric change along with sluggish reaction kinetics. Herein, an effective synergetic Sn incorporation‐Zn substitution strategy is proposed based on copper‐based sulfides. First, Na‐ion storage capability of copper sulfide is significantly improved via incorporating an alloy‐based Sn element. However, this process is accompanied by sacrifice of structural stability due to the high Na‐ion uptake. Subsequently, to maintain the high Na‐ion storage capacity, and concurrently improve cycling and rate capabilities, a Zn substitution strategy (taking partial Sn sites) is carried out, which could significantly promote Na‐ion diffusion/reaction kinetics and relieve mechanical strain–stress within the crystal framework. The synergetic Sn incorporation and Zn substitution endow copper‐based sulfides with high specific capacity (≈560 mAh g −1 at 0.5 A g −1 ), ultrastable cyclability (80 k cycles with ≈100% capacity retention), superior rate capability up to 200 A g −1 , and ultrafast charging feature (≈4 s per charging with ≈190 mAh g −1 input). This work provides in‐depth insights for developing superior anode materials via synergetic multi‐cation incorporation/substitution, aiming at solving their intrinsic issues of either low specific capacity or poor cyclability.