Precise phase control of CuSn alloys on carbon felt via active screen plasma for highly reversible zinc metal anodes

Three-dimensional carbon felt (3D CF) is a promising host architecture for Zn metal anodes, effectively mitigating dendrite growth and volume fluctuations in aqueous zinc-ion batteries (AZIBs). However, pristine CF exhibits poor zincophilicity and a severe hydrogen evolution reaction (HER), both of which significantly limit its practical application. Although metallic Cu coatings improve wettability and Sn coatings suppress HER, the phase-dependent behavior of CuSn alloys is crucial for balancing these effects but remains insufficiently investigated. Herein, we developed a novel active screen plasma (ASP) technique featuring a unique Cu/Sn wire array to deposit CuSn layers with precisely tunable composition and phase on 3D CF. This approach enables a systematic investigation of the correlation between the phase composition of CuSn alloys and their electrochemical performance.

The engineered CuSn-32-CF (Cu:Sn volume ratio = 3:2) with the Cu₆Sn₅ phase exhibited optimal zincophilicity—evidenced by the lowest Zn²⁺ nucleation overpotential (η_nu = 21.1 mV), a near-0° contact angle, and significantly suppressed HER. Consequently, the Zn deposited on CuSn-32-CF displayed a uniform, dense, and dendrite-free morphology. Symmetric cells fabricated with Zn@CuSn-32-CF exhibited exceptional cycling stability, maintaining stable operation for 400 h under conditions of 0.5 mA cm⁻² and 0.5 mAh cm⁻². Full cells assembled with Zn@CuSn-32-CF anodes and α-MnO₂ cathodes delivered a high specific capacity (300.1 mAh g⁻¹ at 0.2 A g⁻¹) and retained 82.8 % of their initial capacity after 2000 cycles at 2 A g⁻¹. This work proposes a facile and efficient ASP strategy for fabricating high-performance alloy-modified 3D Zn anodes via precise interfacial phase control.