Superior potassium-ion hybrid capacitor based on novel P3-type layered K0.45Mn0.5Co0.5O2 as high capacity cathode

Abstract

Herein, we demonstrate a new non-aqueous potassium-ion hybrid capacitor (KIC) using novel P3-K0.45Mn0.5Co0.5O2 and commercial activated carbon (CAC) as the cathode and anode, respectively. A simple sol–gel method is used to synthesize the P3-K0.45Mn0.5Co0.5O2 cathode nanoplatelets. The structural and morphological studies are performed using various characterization techniques, and their electrochemical performances are studied in half-cell configurations against metallic K. The P3-K0.45Mn0.5Co0.5O2 nanoplatelets can reversibly host K+ ions delivering a high capacity of 140 mAh g−1 in the wide voltage window of 1.2–3.9 V. Exhibiting smooth voltage profiles, it offers reasonable rate capability and cyclability, retaining over 80% capacity after 50 cycles. Involving a two-phase (P3–O3) redox mechanism, P3-K0.45Mn0.5Co0.5O2 forms robust cathode material for potassium-ion batteries. With Activated Carbon, the capacitor could provide very high energy and power densities of 43 Wh kg−1 and 30 kW kg−1, respectively, in the voltage range of 0–3.0 V. Even at a 3-s charge–discharge rate (10 A g−1), an energy density of 14.5 Wh kg−1 could be retained (corresponding to a power of 15 kW kg−1). Also it could retain 88% of its energy density with a substantially high stability up to 30,000 cycles at 10 A g−1.