Resolving the Zincophilicity-Desolvation Dilemma of Electrolyte Additives via Molecular Engineering for Achieving High-Rate Zinc Anodes with Minimized Polarization

Abstract

Zincophilic additives have been widely applied to stabilize Zn metal anodes owing to their efficacy in regulating Zn²⁺ diffusion. However, their high zincophilicity causes elevated desolvation barriers, contributing to increased polarization and reduced stability, particularly under high-current conditions. Herein, a novel molecular engineering approach is proposed that integrates steric hindrance and H-bond interactions to promote the desolvation of zincophilic additives, thereby achieving high-rate Zn anodes with minimized polarization. As a proof-of-concept, N,N-di-(2-picolyl)ethylenediamine (NDPA), a zincophilic additive comprising potent Zn²⁺ chelating sites and a polar amino tail group is designed. NDPA boasts four solvation sites, which not only contribute exceptional zincophilicity, effectively regulating Zn²⁺ diffusion but also exhibit significant steric hindrance, reducing the number of solvation H₂O molecules, and lowering dehydration energy. Additionally, NDPA's free amino groups form H-bonds with H₂O molecules, facilitating the dissociation of coordinated additives. Consequently, at a high current density of 20 mA cm⁻², the addition of NDPA to Zn||Zn symmetric cell improves their lifespan from 37 h to over 2000 h and reduces polarization voltage from 137 to 82 mV. This work presents a novel strategy to overcome the zincophilicity-desolvation dilemma of electrolyte additives for developing durable and high-rate zinc anodes.