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

Herein, we demonstrate a new non-aqueous potassium-ion hybrid capacitor (KIC) using novel P3-K 0.45 Mn 0.5 Co 0.5 O 2 and commercial activated carbon (CAC) as the cathode and anode, respectively. A simple sol�gel method is used to synthesize the P3-K 0.45 Mn 0.5 Co 0.5 O 2 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-K 0.45 Mn 0.5 Co 0.5 O 2 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-K 0.45 Mn 0.5 Co 0.5 O 2 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 . © 2019 Elsevier B.V.