Rational Design of Sulfur-Doped Three-Dimensional Ti3C2Tx MXene/ZnS Heterostructure as Multifunctional Protective Layer for Dendrite-Free Zinc-Ion Batteries

Owing to its high theoretical capacity, appropriate working potential, abundant resource, intrinsic safety, and low cost, zinc (Zn) metal is regarded as one of the most promising anode candidates for aqueous batteries. However, the hazards caused by dendrite growth and side reactions impede its practical applications. Herein, to solve these problems, a protective heterogeneous layer composed of electronic conductive sulfur-doped three-dimensional (3D) MXene and ionic conductive ZnS on Zn anode is designed and constructed. The sulfur doping and the creation of a 3D structure on MXene are simultaneously achieved during the generation of ZnS. The sulfur-doped 3D MXene can effectively homogenize distribution of electric field, decrease local current density, and alleviate volume change. The ZnS can inhibit side reactions, promote uniform Zn2+ distribution, and accelerate Zn2+ migration. Consequently, a stable and dendrite-free Zn anode is achieved with notable cycling stability up to 1600 h and rate performance. The relationship between structure of protective layer and performance of Zn anode is also probed. With the protected Zn anode and freestanding sulfur-doped 3D MXene@MnO2 cathode, a high-energy, long cycling life, and high-rate full cell is obtained. This work may provide a direction for the design of practical Zn anodes and other metal-based battery systems.