Weak Dipole Effect Customized Zinc Ion‐Rich Protective Layer for Lean‐Electrolyte Zinc Metal Batteries

Abstract The industrial development of Zn‐ion batteries requires high performance even with lean‐electrolyte. Nevertheless, lean‐electrolyte can exacerbate concentration polarization at the interface of electrode/electrolyte, leading to significant Zn corrosion and battery failure. Here, a stable Zn ion‐rich protective layer (TMAO‐Zn) is constructed by a unique zwitterion structure of trimethylamine N‐oxide (TMAO). The TMAO is characterized by the direct connection between positive and negative charges (N + ‐O − ) with minimal dipole moment, which renders weak dipole interactions to form the TMAO‐Zn layer with Zn 2+ , thereby reducing concentration polarization and promoting the rapid and uniform deposition of Zn 2+ . Furthermore, the O of TMAO‐Zn exhibits the higher electrophilic index, indicating a stronger propensity for stable hydrogen bond interactions with active free water in the inner Helmholtz layer (IHL), thereby mitigating corrosion under extreme conditions of low electrolyte‐to‐capacity ratio (E/C ratio). Consequently, the symmetrical Zn battery with TMAO‐Zn enables stable cycling for over 250 h with lean‐electrolyte of 15 µL mA h −1 . Additionally, Zn/I₂ pouch battery with a low E/C ratio of 21.2 µL mA h −1 provides ultra‐high stable specific capacity of 96 mA h for over 250 cycles (capacity retention rate of 98.3%). This study offers a new concept to propel the practical application of Zn batteries with lean‐electrolyte.