Application of a clustered countercurrent-flow micro-channel reactor in the preparation of KMnF3 perovskite for asymmetric supercapacitors.

Abstract

A clustered countercurrent-flow micro-channel reactor (C-CFMCR) with adjustable magnification times was constructed for the preparation of KMnF3 perovskite fluoride by a co-precipitation process, in which the concentrations and feed rates of reactants were precisely controlled. Benefitting from the enhanced micromixing efficiency of the microreactor, the KMnF3 particles prepared in C-CFMCR were smaller and less aggregated than those produced with traditional stirred reactors (STR). The prepared KMnF3 was applied as the electrode material in supercapacitors, and the electrochemical measurements showed that the KMnF3 obtained under optimal conditions had a discharge specific capacitance of ∼442 F g−1 at a current density of 1 A g−1, with a decline of ∼5.4% after 5000 charge–discharge cycles in an aqueous electrolyte of 2 M KOH. It was also found that the morphologies and electrochemical performances of the prepared KMnF3 particles changed accordingly with the micromixing efficiencies of C-CFMCR, which can be adjusted by the reactor structure and operating conditions. An asymmetric supercapacitor assembled with the KMnF3 and activated carbon exhibited an energy density of 13.1 W h kg−1 at a power density of 386.3 W kg−1, with eminent capacitance retention of ∼81.2% after 5000 cycles. In addition, only a slight amplification effect of C-CFMCR on the co-precipitation process was noticed, indicating that the C-CFMCR is a promising technology for the massive and controllable production of KMnF3 particles as well as other ultrafine particles.