Controlled Presodiation of Sodium‐Ion Cathode via Electron Cloud Engineering

Chemical presodiation offers a promising pathway to compensate sodium deficiency in cathode and anode materials, thereby enhancing the usable energy density of sodium‐ion batteries. This approach is particularly critical for P2‐ and tunnel‐type cathodes, such as Na 0.44 MnO 2 , where the as‐synthesized materials typically exhibit a 50%–60% sodium deficiency. However, conventional presodiation reagents possess excessively high reductive potential, often leading to oversodiation, structural degradation, and compromised electrode reversibility. Here, we report a rational electron‐cloud engineering strategy to precisely control the sodium chemical potential of presodiation agents. Guided by Hückel's rule, we demonstrate that tailoring π‐conjugation size and introducing electron‐withdrawing groups enables the adjustment of sodium chemical potential via a balance of conjugative and inductive effects. We identify 1‐indanone as an optimal presodiation reagent, capable of delivering sodium to Na 0.44 MnO 2 cathodes without any oversodiation. The resulting electrodes exhibit fully restored sodium inventories, an unprecedented first‐cycle Coulombic efficiency of ∼100%, and improved capacity retention over 350 cycles compared to untreated controls. Our findings establish a versatile framework for controlling sodium delivery in chemical presodiation, providing a new avenue for the design of next‐generation sodium‐ion batteries with enhanced stability and performance.