Exfoliated Triazine‐Based Covalent Organic Nanosheets with Multielectron Redox for High‐Performance Lithium Organic Batteries

TLDR

Next‑generation lithium‑ion batteries demand environmentally friendly electrodes with long cycle life and high energy density, and organic compounds offer chemical richness and cost benefits but suffer from low capacity and poor cycle life due to hydrophobic dissolution and limited electronic conductivity. The authors exfoliate triazine‑based covalent organic nanosheets and composite them with carbon nanotubes, creating thin‑layered 2D structures that activate more functional groups for lithium storage and enhance redox site utilization, with the lithium‑storage mechanism involving 11‑ and 16‑electron redox reactions linked to triazine, piperazine, benzene, C≡N, and NH₂ groups. The resulting material delivers reversible capacities exceeding 1000 mAh g⁻¹ after 250 cycles, rivaling high‑capacity inorganic electrodes.

Abstract

Abstract The development of the next‐generation lithium ion battery requires environmental‐friendly electrode materials with long cycle life and high energy density. Organic compounds are a promising potential source of electrode materials for lithium ion batteries due to their advantages of chemical richness at the molecular level, cost benefit, and environmental friendliness, but they suffer from low capacity and dissatisfactory cycle life mainly due to hydrophobic dissolution in organic electrolytes and poor electronic conductivity. In this work, two types of triazine‐based covalent organic nanosheets (CONs) are exfoliated and composited with carbon nanotubes. The thin‐layered 2D structure for the exfoliated CONs can activate more functional groups for lithium storage and boost the utilization efficiency of redox sites compared to its bulk counterpart. Large reversible capacities of above 1000 mAh g −1 can be achieved after 250 cycles, which is comparable to high‐capacity inorganic electrodes. Moreover, the lithium‐storage mechanism is determined to be an intriguing 11 and 16 electron redox reaction, associated with the organic groups (unusual triazine ring, piperazine ring, and benzene ring, and common CN, NH groups).