Configurational Entropy Engineering in Electrolyte Solvation Sheaths for Durable Aqueous Zinc‐Ion Batteries

ABSTRACT

The stability of metal anodes in aqueous batteries is governed by the solvation environment of charge carriers, yet electrolyte design remains largely empirical. Here we establish a thermodynamic framework for electrolyte engineering based on the principle that maximizing configurational entropy within the solvation sheath thermodynamically favors water‐lean coordination structures. Using Zn ²⁺ as a model system, we demonstrate that strategic combination of solvents with complementary donor numbers (DN) and dielectric constants (ε), specifically DMSO (high DN, high ε) and DMAc (moderate DN, moderate‐ε with N‐donor functionality), creates a diverse ensemble of solvation configurations, increasing configurational entropy by ΔS ≈ X J mol ⁻¹ K ⁻¹ (validated by ITC). This entropy gain lowers the Gibbs free energy of water‐deficient solvation complexes by ΔG ≈ Y kJ mol ⁻¹ , fundamentally suppressing water activity. Concurrently, the orthogonal decomposition chemistries of DMSO and DMAc generate a gradient solid‐electrolyte interphase with organic‐rich outer and inorganic‐rich inner layers. The resulting Zn anodes achieve exceptional durability (>3100 h at 1 mA cm ⁻² ) and enable pouch cells retaining 60.2% capacity after 480 cycles. This entropy‐centric design principle transforms electrolyte engineering from trial‐and‐error to thermodynamically guided materials discovery, with implications beyond zinc batteries to other metal anodes facing similar solvation challenges.