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

MoSe 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 MoSe 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 MoSe 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 with a high retention ratio of 99.1% can be maintained after 1000 cycles at 1 A g, which is superior to the previous reports of MoSe nanosheets. The presented strategy is ingenious, offering an effective guidance to designing advanced electrodes to be applied in rechargeable batteries with a long lifespan.