Rational Construction of Yolk-Shell Bimetal-Modified Quinonyl-Rich Covalent Organic Polymers with Ultralong Lithium-Storage Mechanism

Covalent organic polymers are attracting more and more attention for energy storage devices due to their lightweight, molecular viable design, stable structure, and environmental benignity. However, low charge-carrier mobility of pristine covalent organic materials is the main drawback for their application in lithium-ion batteries. Herein, a yolk-shell bimetal-modified quinonyl-rich covalent organic material, Co@2AQ-MnO2, has been designed and synthesized by in situ loading of petal-like nanosized MnO2 and coordinating with Co centers, with the aim to improve the charge conductivity of the covalent organic polymer and activate its Li-storage sites. As investigated by in situ FT-IR, ex situ XPS, and electrochemical probing, the quinonyl-rich structure provides abundant redox sites (carbonyl groups and pi electrons from the benzene ring) for lithium reaction, and the introduction of two types of metallic species promotes the charge transfer and facilitates more efficient usage of active energy-storage sites in Co@2AQ-MnO2. Thus, the Co@2AQ-MnO2 electrode exhibits good cycling performance with large reversible capacity and excellent rate performance (1534.4 mA h g(-1) after 200 cycles at 100 mA g(-1) and 596.0 mA h g(-1) after 1000 cycles at 1000 mA g(-1)).

Automated summary

Covalent organic polymers are promising materials for energy storage due to their lightweight, stable structure, and environmentally-friendly properties. However, their low charge-carrier mobility has hindered their application in lithium-ion batteries. In this study, a yolk-shell bimetal-modified quinonyl-rich covalent organic material, Co@2AQ-MnO2, was designed and synthesized to improve the charge conductivity and activate the Li-storage sites. The electrode exhibited good cycling performance and high reversible capacity, demonstrating the potential of Co@2AQ-MnO2 for energy storage applications.