Roles of Anion and Cation Doping in g-C₃N₄ as Artificial SEI for Regulating Interfacial Zn²⁺ Deposition in Aqueous...

Aqueous zinc-ion batteries are promising for their inherent safety, low cost, and environmental friendliness. However, their performance is limited by dendrite growth, hydrogen evolution, and interfacial instability from uncontrolled Zn²⁺ deposition. Although graphitic carbon nitride (g-C₃N₄) has been explored as an artificial solid electrolyte interphase (ASEI), its limited active sites and sluggish Zn²⁺ transport restrict long-term stability. More importantly, the roles of different doping types in regulating interfacial Zn²⁺ behavior remain unclear. Herein, anion (O) and cation (K) are doped into g-C₃N₄ to construct model ASEI layers for elucidating their respective roles in interfacial regulation. Combined experimental characterizations and theoretical calculations reveal that cation doping (KCN) decreases Zn²⁺ diffusion barrier, thereby facilitating Zn²⁺ transport across the interphase. In contrast, anion doping (OCN) induces strong electrostatic interaction and enhances Zn²⁺ adsorption affinity, leading to improved zincophilicity and synergistically ion transport. These distinct interfacial interactions result in markedly different Zn deposition behaviors, where anion doping enables more uniform nucleation and suppressed dendrite growth. Consequently, the OCN@Zn anode exhibits enhanced cycling stability. This work clarifies the roles of anion and cation doping in regulating interfacial Zn²⁺ deposition from the perspectives of ion transport and interfacial nucleation, and provides mechanistic insights and design guidelines for constructing high-efficiency ASEI layers via heteroatom engineering.