Synthesis of multicarboxylate salts of perylene diimide and their performance and mechanism investigation as organic anode materials for lithium-ion batteries

The pursuit of advanced lithium-ion battery (LIB) electrode materials with high energy density, sustainability, and low cost has driven research into organic compounds. Perylene diimide (PDI)-based derivatives are promising due to their rigid conjugated π-frameworks and multiple redox sites. Conjugated carboxylates demonstrate high specific capacities and stable working potentials. However, PDI-based materials exhibit low specific capacities, while conjugated carboxylates suffer from poor cycling stability caused by unstable solid electrolyte interphase (SEI) layers. Herein, we synthesized a multicarboxylate salt-functionalized PDI derivative, PDI-8COOLi, via amide bond functionalizationusing3,4,9,10-tetracarboxylic anhydride. This strategy preserved PDI's conjugated structure and charge transport capability while reducing electrolyte solubility through salt-forming effects. PDI-8COOLi showed high thermal stability (80.96%mass retention at 500°C) and insolubility in 1:1:1 VEC/VEMC/VDEC electrolytes. PDI-8COOLi delivered a high specific capacity of 764.5 mAh g⁻¹ with 77.4% capacity retention after 150 cycles. Theoretical capacities (1309 mAhg⁻¹)exceeded graphite's limit. This work provides a new paradigm for designing high-performance and mechanistic organic anodes.