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

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, the Na-ion storage capability of copper sulfide is significantly improved via incorporating an alloy-based Sn element. However, this process is accompanied with the sacrifice of structural stability due to the high Na-ion uptake. Subsequently, to maintain the high Na-ion storage capacity, and concurrently improve the cycling and rate capabilities, a Zn substitution strategy (taking partial Sn sites) is carried out, which could significantly promote the Na-ion diffusion/reaction kinetics and relieve the mechanical strain-stress within the crystal framework. The synergetic Sn incorporation and Zn substitution endow the 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. This article is protected by copyright. All rights reserved.