N, P Codoped Hollow Carbon Nanospheres Decorated with MoSe Ultrathin Nanosheets for Efficient Potassium-Ion Storage.

Potassium-ion batteries (KIBs) are gradually being considered as an alternative for lithium-ion batteries because of their non-negligible advantages such as abundance and low expenditure of K, as well as higher electrochemical potential than another alternative─sodium-ion batteries. Nevertheless, when the electrode materials are inserted and extracted with large-sized K ions, the tremendous volume change will cause the collapse of the microstructures of electrodes and make the charging/discharging process irreversible, thus disapproving their extended application. In response to this, we put forward a feasible strategy to realize the in situ assembly of layered MoSe nanosheets onto N, P codoped hollow carbon nanospheres (MoSe/NP-HCNSs) through thermal annealing and heteroatom doping strategies, and the resulting nanoengineered material can function well as an anode for KIBs. This cleverly designed nanostructure of MoSe/NP-HCNS can broaden the interlayer spacing of MoSe to boost the efficiency of the insertion/extraction of K ions and also can accommodate large volume change-caused mechanical strain, facilitate electrolyte penetration, and prevent the aggregation of MoSe nanosheets. This synthetic method generates abundant defects to increase the amounts of active sites, as well as conductivity. The hierarchical nanostructure can effectively increase the proportion of pseudo-capacitance and promote interfacial electronic transfer and K diffusion, thus imparting great electrochemical performance. The MoSe/NP-HCNS anode exhibits a high reversible capacity of 239.9 mA h g at 0.1 A g after 200 cycles and an ultralong cycling life of 161.1 mA h g at 1 A g for a long period of 1000 cycles. This nanoengineering method opens up new insights into the development of promising anode materials for KIBs.