Engineering the Catalytic Superlattices for Highly Reversible Sodium-Ion Storage with A high Compositional Conversion Degree

A major obstacle of transition metal disulfides in sodium-ion batteries is compositional irreversible conversion, leading to fast capacity decay. Here, we propose to engineer a catalytic superlattice structure for achieving a record-high compositional reversible conversion degree (approximate to 100 %). The superlattice is constructed by alternately stacking MoS2 layers and nitrogen/oxygen co-doped reduced graphene oxide-supported single-atom metal layers (MoS2/M-ONG SL, M=Fe, Co, Ni, Cu, Zn) with 100 % MoS2/M-ONG interfaces, in which the metal atoms bridge the two layers through S-M-O chemical bonds. Using MoS2/Co-ONG SL as a model, the unique superlattice structure shows excellent electron and Na+ transport properties during discharge and charge. Moreover, the Co-ONG boosts Na2S adsorption and decomposition by forming Co-3d and S-3p hybridization. As a result, the MoS2/Co-ONG SL shows a high compositional reversible conversion degree(approximate to 100 %), as proven by a series of in-/ex situ spectroscopic analyses. As a result, the MoS2/Co-ONG SL exhibits a stable cycling stability of 300.7 mAh g-1 after 2000 cycles at 2 A g-1, with an ultrasmall capacity decay rate of 0.41 % per 100 cycles. This work offers a noteworthy perspective on the design and fabrication of conversion-type materials, emphasizing the crucial role of interface engineering in achieving excellent bidirectional reaction kinetics.