Coprecipitation Prepared High‐Performance Anode Material KMnF3 for Lithium‐Ion Capacitors

Abstract

Exploring better electrochemical energy storage devices is a great challenge. Lithium‐ion capacitors have attracted much attention because they combine the advantages of Li‐ion batteries and supercapacitors, but the mismatch between the kinetics and capacity of the cathode and anode is still an extraordinary gap. In order to address this issue, a cubic‐phase perovskite fluoride KMnF3 via a simple and safe coprecipitation way is synthesized. The KMnF3 electrode exhibits a cubic‐phase structure and a pseudocapacitive kinetics by X‐ray diffractometer and cyclic voltammetry. The high specific capacity (189 mAh g−1 at 0.1 A g−1 for 500 cycles) and fast pseudocapacitive control dynamics (at the sweep speed of 0.2 mV s−1, the pseudocapacitance ratio is 62.12%) can be demonstrated in half cell, while the b‐value is up to 0.95. Further assembled with activate carbon to form lithium‐ion capacitors (LICs), KMnF3//AC delivers high energy density (24 Wh kg−1), high power density (3900 kW kg−1), and long cycle life over 4000 cycles. The findings shed lights on developing advanced electrode materials for high‐performance electrochemical LICs.