Highly Efficient Spatially–Temporally Synchronized Construction of Robust Li₃PO₄-rich Solid–Electrolyte Interphases in Aqueous Li-ion Batteries

Solid electrolyte interphase (SEI) makes the electrochemical window of aqueous electrolytes beyond the thermodynamics limitation of water. However, achieving the energetic and robust SEI is more challenging in aqueous electrolytes because the low SEI formation efficiency (SFE) only contributed from anion-reduced products, and the low SEI formation quality (SFQ) negatively impacted by the hydrogen evolution, resulting in a high Li loss to compensate for SEI formation. Herein, we propose a highly efficient strategy to construct Spatially-Temporally Synchronized (STS) robust SEI by the involvement of synergistic chemical precipitation-electrochemical reduction. In this case, a robust Li₃PO₄-rich SEI enables intelligent inherent growth at the active site of the hydrogen by the chemical capture of the OH⁻ stemmed from the HER to trigger the ionization balance of dihydrogen phosphate (H₂PO₄⁻) shift to insoluble solid Li₃PO₄. It is worth highlighting that the Li₃PO₄ formation does not extra-consume lithium derived from the cathode but makes good use of the product of HER (OH⁻), prompting the SEI to achieve 100 % SFE and pushing the HER potential into −1.8 V vs. Ag/AgCl. This energetic and robust SEI offers a new way to achieve anion/concentration-independent interfacial chemistry for the aqueous batteries.