A Four‐Electron‐Transfer Robust Small‐Molecule Organic Anode for Low‐Strain Potassium Storage

Potassium‐ion batteries (PIBs) are promising for large‐scale energy storage owing to abundant potassium resources. However, their development is constrained by the lack of high‐capacity and durable anodes capable of accommodating the large‐radius K + . Herein, a small‐molecule organic compound, 2,2′‐bipyridine‐4,4′‐dicarboxylic acid (BDA), is presented as a promising anode for PIBs. The cooperative multielectron redox activity of the carbonyl and imine moieties affords a high reversible capacity, while the conjugated framework and dense molecular packing strengthen the structural stability. Consequently, BDA delivers a specific capacity of 398 mAh g −1 at 100 mA g −1 and retains 186 mAh g −1 after 1000 cycles at 1000 mA g −1 . Combined in situ / ex situ characterizations and theoretical calculations reveal that pristine BDA undergoes an irreversible deprotonation/potassiation during the initial discharge, generating an activated K 2 BDA phase. The subsequent reversible K‐storage is dominated by the carbonyl and imine sites, and involves only minor lattice variation, which accounts for the low volume fluctuation and outstanding cycling stability. In addition, an all‐organic PIB assembled with a pre‐potassiated BDA anode and a PTCDA cathode delivers a high energy density of 174 Wh kg −1 (based on the mass of both electrodes). This study establishes a viable small‐molecule organic anode for high‐performance PIBs.