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.