Controllable preparation of ultrafine KMnF3 perovskite by combining micro-channel reactor and microwave-ultrasonic assistance

Abstract

In this study, a microwave-ultrasonic assisted countercurrent-flow micro-channel reactor (CFMCR M-U) method was designed to prepare KMnF3 perovskite fluoride as supercapacitor electrode material through a co-precipitation process, in which multiple parameters were precisely controlled and their effects on the material synthesis were investigated. Benefited from the excellent micromixing efficiency of both the microwave-ultrasonic assistance and the microreactor, the KMnF3 particles prepared by the CFMCR M-U method were much smaller (∼120 nm) with a more uniform particle size distribution and less aggregated than those produced without the assistance of microwave-ultrasonic, leading to a more superior electrochemical performance. The KMnF3 synthesized under the optimal CFMCR M-U conditions had an initial specific capacity of 406.00 C·g−1 at a current density of 1 A·g−1. After 2500 charge-discharge cycles at a current density of 5 A·g−1, the KMnF3 particles had a retention rate of 92.21% of the initial specific capacity. For KMnF3//AC (active carbon) asymmetric supercapacitor, 123.9% of the initial specific capacitance remained after 5000 charge-discharge cycles. Therefore, it showed that CFMCR M-U method is a very promising technology for the controlled production of ultrafine KMnF3 particles and other products.