Regulating microstructures of soft carbon anodes by terminations of Ti3C2T 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 Ti 3 C 2 T x 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 d 002 -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” structures 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. Pitch-derived soft carbon processes a major challenge of high-temperature graphitization, limiting it as the promising anode for Na storage. The terminations of Ti 3 C 2 T x MXene are utilized for retarding the graphitization and regulating the microstructure. The structural transformation from PP1400 to TiC@C-3 toggles the Na storage mechanism switch of soft carbon from “adsorption” to “adsorption–insertion”, thus achieving high specific capacity. • Retarding the high-temperature graphitization of pitch by the terminations of Ti 3 C 2 T x MXene. • Opening the insertion-dominated sodium storage capability of pitch-derived carbon. • Probing the sodium storage mechanism in disordered carbon.