Regulating microstructures of soft carbon anodes by terminations of Ti3C2Tx MXene toward fast and stable sodium storage

Abstract Soft carbon features low-cost and high-carbon-yield advantages but possesses highly graphitized structures at high pyrolysis temperatures, limiting its application as anode for the sodium (Na) storage technologies. Herein, a novel strategy is devised to retard the high-temperature graphitization and regulate the microstructure of pitch by the terminations of Ti3C2Tx MXene. The abundant and easily releasable terminations influence the cross-linking degree of precursor by consuming the intrinsic hydrogen, realizing a carbon structural transformation from ordered to disordered. Benefiting from the disordered graphitic structure and large d002-spacing, the insertion-dominated Na storage capability of pitch is inspired with a threefold increase in specific capacity. In addition, a series of “TiC-oriented carbon” structrues favoring fast Na storage kinetics are constructed to elaborate the correlation of Na storage behavior dependence on the carbon structural evolution. This strategy is expected to be extended to other soft carbon precursors and help improve the understanding of Na storage mechanism in disordered carbon.