Macrocyclic molecular engineering enables high-energy and durable organic electrode for lithium-ion batteries

Abstract

Organic electrode materials are promising candidates for lithium-ion batteries, but their practical adoption is constrained by the persistent trade-off between capacity and cycling stability. While small-molecule organic compounds deliver high capacities yet suffer from dissolution, covalent organic frameworks enhance stability at the expense of active-site accessibility. Here, we introduce a macrocyclic molecular design synergizing framework-like robustness with small-molecule redox efficiency. The designed hexagonal monocyclic benzoquinone integrates a π-conjugated core with densely packed electroactive moieties (carbonyl, imine, and hydroxyl), enabling a high theoretical capacity of 812 mAh g−1. As a positive electrode, it achieves near-theoretical capacity (806 mAh g−1 at 0.05 A g−1) with a high specific energy of 1507 Wh kgHPBQ−1, while maintaining 81% capacity after 1000 cycles at 5 A g−1. Mechanistic studies explore a potential 36-electron transfer mechanism per macrocyclic unit during initial discharge, followed by irreversible hydroxyl-to-carbonyl conversion upon charging, which generates a phenanthrenequinone-based macrocycle capable of reversible 48-electron transfer per macrocyclic unit in subsequent cycles. This molecular architecture has the potential to overcome the longstanding capacity-stability trade-off in organic electrodes. Organic electrode materials face a persistent capacity–stability trade-off. Here, authors design a macrocycle combining covalent organic framework-like robustness with small-molecule redox efficiency, which renders a capacity of 806 mAh g−1 at 50 mA g−1 and retains 81% capacity after 1000 cycles at 5 A g−1.