Unveiling high-voltage organic cathodes via carbazole-dihydrophenazine conjugation for next-generation lithium dual-ion batteries

Organic redox-active compounds have shown immense potential in advancing battery technology, yet conventional organic cathodes still struggle with low capacities and insufficient output voltages. Here, we design a p-type organic polymer cathode based on poly[5-(3-(9H-carbazol-9-yl)phenyl)-5,10-dihydrophenazine] (p-CZPDPZ), in which the conjugation of carbazole (CZ) and dihydrophenazine (DPZ) units through Buchwald-Hartwig C-N cross-coupling reaction leads to a remarkable average potential of 3.45 V, a peak specific capacity of 197mAh g⁻¹, and an impressive energy density of 680 Wh kg⁻¹. The expanded π-conjugated architecture in p-CZPDPZ enables efficient electron density dilution and single-electron stabilization through whole-skeleton delocalization during redox processes, contributing to an exceptional lifespan of 4.8 months with a long-term cycling stability exceeding 1600 cycles. Characterizations and theoretical calculations confirm that p-CZPDPZ can stably and reversibly store BF₄^- for charge compensation. The constructed Li-based dual-ion full batteries (LDIBs) assembled with graphite anode and p-CZPDPZ cathode exhibit a peak discharge capacity of 185 mAh g⁻¹ and an energy density of up to 596 Wh kg⁻¹ with over 1400 cycles. This study provides a novel framework for designing high-performance organic cathode materials through molecular conjugation strategy, offering substantial potential for advancing next-generation lithium dual-ion batteries.