Carbon Quantum Dot Modified Reduced Graphene Oxide Framework for Improved Alkali Metal Ion Storage Performance

Abstract

Organic materials with redox-active oxygen functional groups have attracted great attention as electrode materials for alkali-ion storage due to their earth-abundant constituents, structural tunability, and enhanced energy storage properties. Therefore, the development of advanced carbon nanostructures is highly desirable for improving the electrochemical performance of organic electrodes. While nanoscale carbon materials like carbon quantum dots (CQDs) have been identified as promising candidates for a variety of applications such as sensing, catalysis, drug delivery...etc., their utilization in electrochemical energy storage remains challenging with limited investigations. Herein, a hybrid carbon framework consisting of reduced graphene oxide (rGO) and carbon quantum dots is developed via a simple one-pot solvothermal reduction method, and a systematic study is conducted to investigate its redox mechanism and electrochemical properties with Li-, Na-, and K-ions. With the incorporation of carbon quantum dots, the hybrid rGO-CQD cathode exhibited much improved charge storage performance. In particular, the Li-ion cell delivered impressive reversible capacity (257 mAh g-1 at 50 mA g-1), rate capability (111 mAh g-1 at 1 A g-1) and cycling stability (79% capacity retention after 10,000 cycles). The charge storage behavior of various alkali-ions was also confirmed by density functional theory calculations. Furthermore, our calculations uncovered the CQD structure-electrochemical reactivity relationships, which could pave the way for the tailoring of CQD species to achieve optimal alkali-ion storage.