Ultrafine ZnS Nanoparticles in the Nitrogen-Doped Carbon Matrix for Long-Life and High-Stable Potassium-Ion Batteries.

Potassium-ion batteries (KIBs) have attracted researchers' widespread attention because of the luxuriant reserves of potassium salts and their low cost. Nevertheless, the absence of suitable electrode materials with a stable electrochemical property is a crucial issue, which seriously hampers the practical applications of KIBs. Herein, a scalable anode material consisting of ultrafine ZnS nanoparticles encapsulated in three-dimensional (3D) carbon nanosheets is explored for KIBs. This hierarchical anode is obtained via a simple and universal sol-gel method combined with a typical solid-phase sulfidation route. The special structure of this anode facilitates good contact with electrolytes and has enough voids to buffer the large volumetric stress changing during K+ insertion/extraction. Thus, the 3D ZnS@C electrode exhibitsour stable cycling performance (230 mAh g-1 over 2300 cycles at 1.0 A g-1) and superior rate capability. The kinetic analysis indicates that a ZnS@C anode with considerable pesoudecapactive contribution benefits a fast potassium/depotassium process. Detailed ex-situ and in-situ measurements reveal that this ZnS@C anode combines reversible conversion and alloying-type reactions. This rationally designed ZnS@C material is highly applicable for KIBs, and the current route opens an avenue for the development of highly stable K+ storage materials.