Fully exposed (101) plane endowing CoSe anode with fast and stable potassium storage

Transition-metal selenides, especially cobalt selenides (CoSe), are widely regarded as a promising anode for potassium-ion batteries (KIBs) due to their high theoretical capacity and good electrical conductivity. However, CoSe easily suffers from a substantial volume change upon repeated cycling, leading to a fast capacity decay and poor cycling stability. Herein, a dual-carbon confined CoSe is successfully designed by using metal-organic frameworks as raw materials. Various characterizations disclose that the introduction of the extra carbon phase is conducive to the growth of (101) plane of CoSe, and based on this, rationally regulating carbonization temperature can further promote the exposure of (101) plane. Such fully exposed (101) plane not only provides sufficient active surface to uptake K-ions, but also favors the accommodation of electrode structure fluctuation, accounting for a high capacity and prolonged cycle lifespan. As a result, the optimized sample (denoted as 750 degrees C-NC@CoSe/NC) delivers 392.5 mAh g-1 at 0.5 A g-1, accompanied by an excellent cycling stability over 400 cycles with 196.7 mAh g-1 at a high current density of 1 A g-1. This work is expected to offer effective guidance for constructing advanced CoSe anode toward KIBs.