Air‐Stable Organic Metal Reservoirs: Extended Conjugation Enabled Multielectron Redox‐Based Cathode Crystals for Lithium‐Ion Batteries

Air‐stable organic crystal‐based metal‐ion batteries (MIBs) working in conventional electrolyte concentrations are important for cost‐effective renewable energy storage. In the dearth of such stable “organic metal reservoirs,” a family of porphyrin‐fused extended conjugated sulfonamide compounds (ECSA) has been demonstrated for MIBs of lithium‐ion batteries (LIBs). ECSA forms a class of metalloporphyrins (M 4 ZnSOTAPP) having different metal ion possibilities (M = Li + /Na + /K + ) with four redox meso‐positions. The discharge voltage of Li 4 ZnSOTAPP crystal‐based LIB is found to be 2.5 V versus Li/Li + , in line with the theoretical calculations having a theoretical capacity of ~100 mAh g −1 for a cell constructed in practically relevant conditions having 1 M electrolyte. Further to the demonstration of stable performance of Li 4 ZnSOTAPP in LIB (~77% capacity retention at 1000 cycles), its optical activity, crystal structure, and the charge–discharge mechanism have been unraveled. Combined experimental and computational analyses suggest that the sulfonamide groups serve as the primary redox‐active centers for lithium‐ion storage, while the extended porphyrin‐fused conjugated framework facilitates charge delocalization during cycling. Demonstration of K 4 ZnSOTAPP crystals further establishes the avenue for π‐extended structures based beyond Li organic batteries.