Conversion pseudocapacitance-contributing and robust hetero-nanostructural perovskite KCo0.54Mn0.46F3 nanocrystals anchored on graphene nanosheets anodes for advanced lithium-ion capacitor, battery and their hybrids

Lithium-ion capacitors (LICs) and lithium-ion batteries (LIBs) have drawn particular interest as renewable and green energy storage devices. However, the behavior of LICs and LIBs is largely limited by the sluggish kinetics and inferior cycling stability of conventional insertion and alloying-type anodes. In this work, we demonstrate novel pseudocapacitive conversion-type and robust hetero-nanostructural cobalt–manganese perovskite fluorides/reduced graphene oxides (KCMF(3 : 2)/rGO) anodes with superior kinetics and stability for advanced LICs, LIBs and their hybrids (LIC/Bs). The KCMF(3 : 2)/rGO candidate composed of stoichiometric KCo0.54Mn0.46F3 and approximately 11 wt% rGO exhibits superior performance to the solvothermally synthesized pure KCMF(3 : 2) and U-KCMF(3 : 2)/rGO composites without ball-milling treatment, which largely benefits from the conversion pseudocapacitance characteristics and strong synergistic effect of the robust perovskite fluorides/graphene hetero-nanostructures. A typical pseudocapacitive conversion reaction mechanism for the perovskite KCMF(3 : 2) anode can be deduced by various ex situ characterizations and electrochemical techniques. The designed LIBs, LICs and LIC/Bs with the KCMF(3 : 2)/rGO as the anode and activated carbon (AC), LiFePO4 (LFP) and AC/LFP(1 : 3) as cathodes respectively show remarkable performance in a broad temperature range. This work provides new insight of pseudocapacitive conversion-type and robust hetero-nanostructural electrode materials for advanced lithium-ion energy storage and will have a significant impact on the development of high-performance energy storage devices.