Tailoring solvation sheath and desolvation processes of weakly solvated Zn2+ through heterointerfaces built-in electric field effects for ultra-stable aqueous zinc batteries

Solvated zinc ions are prone to undergo desolvation at the electrode/electrolyte interfaces, and unstable H 2 O molecules within the solvated sheaths tend to trigger hydrogen evolution reaction (HER), further accelerating interfaces decay. Herein, we propose for the first time a novel strategy to enhance the interfacial stabilities by in-situ dynamic reconstruction of weakly solvated Zn 2+ during the desolvation processes at heterointerfaces. Theoretical calculations indicate that, due to built-in electric field effects (BEFs), the plating/stripping mechanism shifts from [Zn(H 2 O) 6 ] 2+ to [Zn(H 2 O) 5 (SO 4 ) 2- ] 2+ without additional electrolyte additives, reducing the solvation ability of H 2 O, enhancing the competitive coordination of SO 4 2− , essentially eliminating the undesirable side effects of anodes. Hence, symmetric cells can operate stably for 3000 ​h (51.7-times increase in cycle life), and the full cells can operate stably for 5000 cycles (51.5-times increase in cycle life). This study provides valuable insights into the critical design of weakly solvated Zn 2+ and desolvation processes at heterointerfaces. Herein, we propose for the first time a novel strategy to enhance the interfacial stabilities by in-situ dynamic reconstruction of weakly solvated Zn 2+ during the desolvation processes at heterointerfaces. Due to built-in electric field effects (BEFs), the plating/stripping mechanism shifts from [Zn(H 2 O) 6 ] 2+ to [Zn(H 2 O) 5 (SO 4 ) 2- ] 2+ without additional electrolyte additives, reducing the solvation ability of H 2 O, enhancing the competitive coordination of SO 4 2− , essentially eliminating the undesirable side effects of anodes. • Driven by the Built-in Electric Fields (BEFs), the plating/stripping mechanism is transformed from [Zn(H 2 O) 6 ] 2+ to weakly solvated [Zn(H 2 O) 5 (SO 4 ) 2- ] 2+ without the addition of extra electrolyte additives, further reducing the solvation capabilities of H 2 O, enhancing the competitive coordination capacity of SO 4 2− , and eliminating the undesirable anodic side-effects. • Owing to the heterointerfaces engineering, the structural stabilities are significantly enhanced. Therefore, DFHI-Zn//DFHI-Zn symmetric cells can cycle stably for 3000 ​h (51.7-times increase in cycle life), and DFHI-Zn//I 2 @C full cells can cycle stably for 5000 cycles (51.5-times increase in cycle life). • DFHI-Zn also far outperform the Bare Zn in terms of voltage polarisation and cycle life during high-current charging and discharging (20 ​mA ​cm −2 ). Moreover, the hydrogen Gibbs free energy (Δ G H∗ ) of DFHI-Zn is −1.22 ​eV, which is much lower than that of bare Zn (−0.95 ​eV), thus suppressing the hydrogen evolution reaction (HER) side reactions at the zinc metal anodes. • Due to the charge redistribution, the heterointerfaces induced solvation recombination of internal BEFs and [Zn(H 2 O) 5 (SO 4 ) 2- ] 2+ accelerates the ion diffusion kinetics and reduces the ion diffusion barriers, leading to swift charge transfer kinetics.