Regulating Solvation Structure and Hydrogen‐Bond Network via L‐Malic Acid Additive for High‐Performance Aqueous Nickel‐Iodine Batteries

ABSTRACT Novel aqueous nickel‐ion batteries (NIBs) emerge as a promising candidate for advanced energy storage due to high theoretical capacity of Ni (913 mA h g −1 and 8136 mA h cm −3 ). However, the practical deployment of NIBs is mainly hindered by large battery polarization, easy passivation, and low Coulombic efficiency, the uncertain solvation structure and strong polarizing ability of Ni 2 + lead to sluggish desolvation and severe electrode‐electrolyte incompatibility, which aggravate passivation and efficiency loss. Herein, we introduce L‐malic acid (MA) as an electrolyte additive to reconstruct electrolyte hydrogen‐bond network environment. Combined characterization and computational simulations demonstrate that MA effectively modulates the primary solvation sheath of Ni 2+ and suppresses water activity. These modifications significantly enhanced anode interface compatibility, mitigated parasitic passivation and corrosion, and markedly improved Ni 2+ transport kinetics. Consequently, the symmetric cell achieves lower overpotential (396→237 mV) and exceptional cycling stability exceeding 2800/1700 h at 0.1/0.2 mA cm −2 . Furthermore, MA‐mediated modulation of iodine conversion kinetics; the Ni‐I 2 full cell exhibits a high specific capacity of 296 mA h g −1 at 0.5 A g −1 and retains stable performance over 1000 cycles at 1 A g −1 . This study proposes a new strategy for electrolyte design aimed at developing advanced NIBs.