Synergistic Modulation of HOMO Energy Level and Electronic Structure in Phthalates Anodes Active Materials Enables High-Performance of Li-Ion Batteries.

Abstract

This study employs molecular engineering to modulate HOMO levels and electronic structures, designing high-performance phthalate-based anodes (ZnPA, CaPA, CuPA) to address challenges like limited capacity and poor cycling in organic lithium-ion batteries. CuPA delivers 749 mAh g^-1after 100 cycles at 0.1 A g^-1and retains 200 mAh g^-1after 2500 cycles at 1 A g^-1. ZnPA achieves 650 mAh g^-1at 0.1 A g^-1and maintains 200 mAh g^-1after 1500 cycles at 1 A g^-1. CaPA shows increased capacity at higher current (197 mAh g^-1at 1 A g^-1) due to (100) plane expansion. Redox mechanisms differ: CuPA and ZnPA carbonyl group facilitates lithium storage by a reversible enolization reaction, while the activated benzene ring exhibits redox activity for reversible lithiation/delithiation, with Cu²⁺ irreversibly reducing to Cu⁺, while Zn²⁺ remains stable. CaPA enables efficient lithium storage by the reversible intercalation and deintercalation of lithium ions on its (100) crystallographic plane. Full cells with LiFePO₄ exhibit excellent performance: CuPA||LFP and ZnPA||LFP retain over 50% capacity after 1000 cycles; CaPA||LFP shows outstanding rate capability (103 mAh g^-1at 4C). This work demonstrates that molecular structural engineering is an effective strategy for enhancing organic electrode materials.