N, P Codoped Hollow Carbon Nanospheres Decorated with MoSe 2 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 2 nanosheets onto N, P codoped hollow carbon nanospheres (MoSe 2 /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 2 /NP-HCNS can broaden the interlayer spacing of MoSe 2 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 2 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 2 /NP-HCNS anode exhibits a high reversible capacity of 239.9 mA h g -1 at 0.1 A g -1 after 200 cycles and an ultralong cycling life of 161.1 mA h g -1 at 1 A g -1 for a long period of 1000 cycles. This nanoengineering method opens up new insights into the development of promising anode materials for KIBs.