CuO Nanoplates for High‐Performance Potassium‐Ion Batteries

Potassium-ion batteries (KIBs) are promising alternatives to lithium-ion batteries because of the abundance and low cost of K. However, an important challenge faced by KIBs is the search for high-capacity materials that can hold large-diameter K ions. Herein, copper oxide (CuO) nanoplates are synthesized as high-performance anode materials for KIBs. CuO nanoplates with a thickness of ≈20 nm afford a large electrode-electrolyte contact interface and short K+ ion diffusion distance. As a consequence, a reversible capacity of 342.5 mAh g-1 is delivered by the as-prepared CuO nanoplate electrode at 0.2 A g-1 . Even after 100 cycles at a high current density of 1.0 A g-1 , the capacity of the electrode remains over 206 mAh g-1 , which is among the best values for KIB anodes reported in the literature. Moreover, a conversion reaction occurs at the CuO anode. Cu nanoparticles form during the first potassiation process and reoxidize to Cu2 O during the depotassiation process. Thereafter, the conversion reaction proceeds between the as-formed Cu2 O and Cu, yielding a reversible theoretical capacity of 374 mAh g-1 . Considering their low cost, easy preparation, and environmental benignity, CuO nanoplates are promising KIB anode materials.