Layer-by-layer hetero-carbon modifying ZnS nanocubes anode with improved long-term life for sodium-ion batteries

Zinc sulfide (ZnS) anode has gripped much focus in face of the various candidates for sodium-ion batteries (SIBs) because of its high capacity, abundant resource as well as environmental friendliness. Nevertheless, the structural collapse of ZnS and the dissolution of polysulfides will irreversibly lead to inferior Na-storage properties. Herein, layer-by-layer hetero-carbon modifying ZnS nanocubes anode (ZnS@NDC) composite has been rationally designed and prepared using pre-carbonized ZIF-8 as a matrix framework, C3N4 and polypyrrole as the coated carbon sources. The initial carbon layer derived from C3N4 can change the surface properties of ZnS nanocubes improving the electronic affinities and provide sufficient buffer matrix successfully inhibiting the agglomeration of ZnS nanocubes. The second carbon layer derived from polypyrrole can improve the ionic diffusion and electronic conductivity owing to the high conductivity and strong charge storage capacity of polypyrrole, as well as further accommodate volume expansion of the ZnS nanocubes. Synergistic effects of layer-by-layer hetero-carbon modifying can also refrain from dissolution of polysulfides improving the structural stability and electrochemical kinetics. When denoted as the anode for SIBs, ZnS@NDC electrode displays admirable long-term life stability and rate capability with capacities of 518.6 mA h g−1 at 1.5 A g−1 after 1000 cycles and 192.4 mA h g−1 at 10 A g−1, respectively. The idea of synthetic ZnS@NDC material supply experimental basis for the farther development of Na-storage devices and provide an innovative way for the synthesis of other metal compounds based on layer-by-layer construction.