Bulk‐Phase Grain Boundaries Regulation Enables Highly Reversible Zn Anodes for Rechargeable Aqueous Zn‐Ion Batteries

Dendrites and side reactions of Zn anodes severely restrict the application of aqueous Zn‐based batteries for grid‐scale energy storage. While surface/interface modification strategies have shown some progress in improving Zn anode reversibility, they still fall short in addressing the overall regulation and intrinsic mechanisms from the bulk‐phase perspective. Herein, a bulk‐phase composite Zn/CNTs anodes fabricated by a powder‐metallurgy‐based strategy is introduced. Benefiting from the regulation of grain boundary engineering on local electric conductivity, electric field distributions, and Zn atom absorption energy, the Zn/CNTs anodes effectively suppress dendrite growth and enhance corrosion resistance during Zn stripping/plating cycles. Symmetrical cells equipped with Zn/CNT4 anodes exhibit extended cycling stability with minimal voltage hysteresis (only 22 mV). Furthermore, the full cells incorporating Zn/CNT4 with commercial MnO2 demonstrate superior rate performance and specific capacitance retention after 500 h cycling. This breakthrough opens up new avenues for optimizing metallic anodes at the bulk phase level using powder metallurgy, enabling scalable manufacturing processes, and providing valuable insights for various metal anode systems. Distinctly different from the traditional surface/interface modification for the Zn anodes, this work provides a groundbreaking regulation perspective to achieve highly reversible zinc anode from bulk‐phase grain boundary optimization. Benefiting from grain boundary regulation with highly conductive CNTs, the bulk‐phase composite Zn/CNTs anodes exhibit substantial suppression of dendrite growth and enhanced corrosion resistance during Zn stripping/plating processes.