Sodium-Storage Performance of K⁺-Intercalated Na_<i>x</i>Cu_0.2Mn_0.8O₂

Abstract

This work proposes a method to prepare a K+-intercalated P2-NaxCu0.2Mn0.8O2 cathode material for sodium-ion batteries. By calcining a P3-KxCu0.2Mn0.8O2 in a Na+ rich environment, a K+-intercalated NaxCu0.2Mn0.8O2 cathode with a stable P2 phase and high K+ content can be obtained. The intercalation of K+ enlarges the interlayer distance and improves the diffusion of Na+, thus enhancing the sodium-storage performance of the material. High capacity (155.1 mAh g–1 at 1 C), high rate performance (71.2 mAh g–1 at 10 C), and good stability (78.18% after 200 cycles at 1 C) can be achieved. It is found that K+ can be well-preserved inside the material during the cycling process. Hence, the enhancement caused by K+ is more evident than other similar materials prepared by conventional methods during the charge and discharge cycles.