High-Performance Potassium-Ion Batteries with Robust Stability Based on N/S-Codoped Hollow Carbon Nanocubes.

Currently, a big challenge for the practical use of potassium-ion batteries (PIBs) is their intrinsically poor cycling stability, due to the relatively large radius of K+ and sluggish kinetics for intercalation/deintercalation. Here we report the scalable fabrication of N/S-codoped hollow carbon nanocubes (NSHCCs), which have the potential as an electrode for advanced PIBs with robust stability. Their discharge and charge specific capacities are ∼560 mA h g-1 and 310 mA h g-1 at a current density of 50 mA g-1, respectively. Meanwhile, they exhibit 100% specific capacity retention after 620 cycles over 9 months at a low current density of 50 mA g-1, which is state-of-the-art among carbon materials. Moreover, they demonstrate nearly no sacrifice in specific capacities with 99.9% retention after 3000 cycles over 4 months under a high current density of 1000 mA g-1, superior to most carbon analogues for potassium storage previously reported. The improved electrochemical performance of NSHCC can be mainly attributed to the unique hollow carbon nanocubes with incorporated N and S dopants, which can expand the carbon layer spacing, facilitate K+ adsorption, and relieve the volume change during the intercalation/deintercalation of K+ ions.