Mxene Ti3C2 generated TiO2 nanoparticles in situ and uniformly embedded in rGO sheets as high stable anodes for potassium ion batteries

Ti3C2/TiO2/rGO nanosheets were synthesized as anode materials for potassium ion batteries (KIBs) using modified Hummers, freeze drying, and thermal reduction in this paper. Layered Ti3C2 /TiO2/rGO nanosheets were synthesized by in-situ formation of rGO and TiO2 nanoparticles between Ti3C2 layers. As one of the most important members of MXenes family, Ti3C2 exhibits unique electronic characteristics, high specific surface area, strong electrical conductivity and chemically active surface, which can enhance electrode capacity. There are three ways to increase electrode conductivity and capacity: Firstly, rGO is applied as the substrate for the inlaying of TiO2 and Ti3C2 nanoparticles and nanosheets. Secondly, rGO may also buffer electrode volume changes during charging and discharging processes. In addition, the enormous surface area of rGO makes Ti3C2 and TiO2 nanoparticles dispersion well, and Ti3C2 and TiO2 nanoparticles can well separate rGO nanoparticles and prevent them from stacking up again. The synergistic effect of the three can efficiently relieve the stress and provide a rapid transport pathway between electrons and ions. The flake structure of Ti3C2/TiO2/rGO is advantageous to the stability of SEI film, which makes the material maintain good activity during charge and discharge process, and significantly increases its electrochemical perfor-mance. Therefore, Ti3C2/TiO2/rGO electrode has a high reversible capacity of 349.2 mAhg-1 after 200 cycles of 100 mAg-1 current, and a high stable capacity of 229.3 mAhg-1 after 500 cycles of 500 mAg-1 current, and has exceptional rate performance. The structure of Ti3C2/TiO2/rGO composite remains stable after 500 cycles, and no agglomeration occurs. The detailed reaction mechanism of Ti3C2/TiO2/rGO electrode as KIBs anode was analyzed by SEM, XRD, Raman, TGA, FT-IR, BET, TEM, XPS, EDS, CV, EX-situ XRD, ex-situ TEM, and so on. Therefore, it can be concluded that the Ti3C2/TiO2/rGO composite is an appropriate anode material for KIBs.(c) 2022 Elsevier B.V. All rights reserved.