Bond-Engineered MoSe2 Nanosheets with Expanded Layers and an Enriched 1T Phase for Highly Efficient Na+ Storage

MoSe2 has attracted significant interest for Na+ storage due to its large interlayer distance, favorable band gap structure, and satisfying theoretical specific capacity. Nevertheless, the poor conductivity and large volume stress/strain always lead to poor cycle stability and limited rate capability. Herein, the P-Se bond and phase engineering strategies are proposed to enhance the stability of MoSe2 with the assistance of carbon compositing. Systematical characterizations confirm that the presence of a strong P-Se bond can ensure the good structural stability and enlarge the layer distance of the MoSe2 anode. 1T phase-enriched composition endows excellent conductivity and thus fast Na+ transport kinetics. Additionally, the combination of carbon contributes to the improvement of electron conductivity, further enhancing the reversible Na+ storage and cyclic stability. Consequently, an ultrastable reversible specific capacity of 347.8 mAh g-1 with a high retention ratio of 99.1% can be maintained after 1000 cycles at 1 A g-1, which is superior to the previous reports of MoSe2 nanosheets. The presented strategy is ingenious, offering an effective guidance to designing advanced electrodes to be applied in rechargeable batteries with a long lifespan.