Built-In Electric Field Effects Tailoring Solvation Sheath and Desolvation Processes of Solvated Zn2+ Toward Stable Aqueous Rocking-Chair Zinc-Ion Batteries

Currently, although some progress has been made in infancy-stage rocking-chair aqueous zinc-ion batteries (AZIBs), more discussions have focused only on the different electrochemical performances displayed by different material types rather than the intrinsic ion transport migration electrochemistry. Herein, we for the first time delve into the mechanism of tailoring the solvation sheath and desolvation processes at the electrode/electrolyte interfaces to enhance the structural stabilities in the deep discharge states. In this work, the TiO₂ front interfaces are induced on electrochemically active but unstable TiSe₂ host materials to construct unique TiO₂/TiSe₂–C heterointerfaces. According to X-ray absorption near edge structure (XANES), differential electrochemical mass spectrometry (DEMS), and electrochemical quartz crystal microbalance (EQCM), the intercalated species are transformed from [Zn(H₂O)₆]²⁺ to [Zn(H₂O)₂]²⁺ due to the built-in electric fields (BEFs) effects, further accelerating the ion transfer kinetics. Furthermore, owing to the absence of high-energy desolvation solvents released from desolvation processes, hydrogen evolution reaction (HER) energy barriers, Ti–Se bond strength, and structural stabilities are significantly improved, and the initial CE and HER overpotentials of the TiO₂/TiSe₂–C heterointerfaces increased from 13.76% to 84.7%, and from 1.04 to 1.30 V, respectively, and the H₂ precipitation current density even at −1.3 V decreased by 73.2%. This work provides valuable insights into the complex interface electrochemical mechanism of tailoring the solvation sheath and desolvation processes toward rocking-chair zinc-ion batteries.