Long-life superlithiation of few-layered covalent organic nanosheets via graphene quantum dots/carbon nanotube stabilized three-dimensional architecture

Abstract

Organic electrodes have aroused growing interest by virtue of their molecular diversity, environmental friendliness, and operation safety. However, sluggish lithium diffusion kinetics, dissolution in the organic electrolyte, poor electrical conductivity and low reversible capacities are the bottlenecks compared to their inorganic counterparts. Herein, we report a new type of exfoliated covalent organic nanosheet (E-CON) based composite electrode with large reversible capacities for lithium organic batteries based on intriguing new lithium storage sites of CC and higher utilization efficiency of CN redox sites compared to its bulk counterpart. The surface modification of the E-CONs by carboxyl-functionalized graphene quantum dots (GQDs) and carbon nanotubes can ensure long cycle life of the electrode due to the facilitated transfer of charge or lithium and prevent restacking of E-CONs. The E-CON based composite electrode exhibits an extremely large reversible capacity of 1386 mA h g⁻¹ (1687 mA h g⁻¹ based on E-CON contribution in the composite) after 300 cycles at 100 mA g⁻¹ with good high-rate capability. The lithium storage mechanism is determined to be one lithium ion per CN and two lithium ions per CC group from five hyper-conjugated benzene rings.