Synergistic Electrode and Electrolyte Polarities Lead to Outstanding Organic Potassium‐based Batteries

Organic materials are promising as battery electrodes due to their flexible design, low cost, and sustainability. Although high electrolyte concentrations are known to suppress organic cathode dissolution, the organic cathode solubility depends on the interplay between the electrode and electrolyte polarities, which remains unexplored. Here, we elucidate the delicate interplay of electrode and electrolyte polarities to achieve stable cycling of organic cathode. Notably, we demonstrate that the solubility of low‐polar organic cathodes initially increases and subsequently decreases in electrolytes with increasing polarity. In contrast, high‐polar organic cathodes display increasing solubility in electrolytes with increasing polarity. When the polarities of the organic cathodes and the electrolyte are tuned, the batteries show high‐capacity retention and Coulombic efficiency. For example, polyaniline||potassiated graphite (KC8) pouch cells deliver 2500 cycles with an average Coulombic efficiency of 99.85%. These new insights into low‐ and high‐polar organic cathode behavior in electrolytes lay a theoretical foundation for designing new organic battery electrodes and optimizing their electrolyte formulation.