K_0.5MnO₂@MWCNT@Super P Composite Electrode for Potassium-Ion Battery Cathode

With the development of energy storage, potassium ion batteries (PIBs) have gradually become a suitable substitute for lithium-ion batteries. Where the layered transition metal oxides cathode materials of potassium ion batteries have attracted much attention due to their high theoretical capacity, unique two-dimensional potassium ion diffusion channels, simple preparation and low cost. In this work, we designed a K_0.5MnO₂@MWCNT@Super P (KMP) composite electrode with P3-type layered structure as the cathode in PIBs through coprecipitation—high temperature sintering method. The SEM results show that the prepared KMP composite electrodes are secondary particles formed by three-dimensional network structures and particles through point–line contact and point–point contact. As a result, the composite electrode with a 7 : 2 : 1 weight ratio of K_0.5MnO₂, conductive carbon (Super-P: MWCNT = 1 : 1) and PVDF delivers a high initial discharge capacity of 112.7 mA h g^–1 at a current density of 20 mA g^–1 and 72.1 mA h g^–1 at 100 mA g^–1. And, it has a capacity retention of 44% at 100 mA g^–1 after 50 cycles. The results show that the unique three-dimensional network structure not only improves the conductivity of K_0.5MnO₂ material, but also effectively alleviates the volume change caused by K⁺ in the charging and discharging process. This study provides a new way to develop layered cathode materials for high energy density potassium ion batteries.