Exploring the electrochemical performance of copper-doped cobalt–manganese phosphates for potential supercapattery applications

Abstract

The significant electrochemical performance in terms of both specific energy and power delivered via hybrid energy storage devices (supercapattery) has raised their versatile worth but electrodes with flashing electrochemical conduct are still craved for better performance. In this work, binary and ternary metal phosphates based on copper, cobalt, and manganese were synthesized by a sonochemical method. Then, the compositions of copper and cobalt were optimized in ternary metal phosphates. The structural studies and morphological aspects of synthesized materials were scrutinized by X-ray diffraction and scanning electron microscopy. Furthermore, the electrochemical characterizations were performed in three- and two-cell configurations. The sample with equal compositions of copper and cobalt (50/50) demonstrates the highest specific capacity of 340 C g⁻¹ at a current density of 0.5 A g⁻¹ among all. This optimized composition was utilized as a positive electrode material in a supercapattery device that reveals a high specific capacity of 247 C g⁻¹. The real device exhibits an excellent energy density of 55 W h kg⁻¹ while delivering a power density of 800 W kg⁻¹. Furthermore, the device was able to provide an outstanding specific power of 6400 W kg⁻¹ while still exhibiting a specific energy of 19 W h kg⁻¹. The stability potential of the device was tested for 2500 continuous charge and discharge cycles at 8 A g⁻¹. Excellent capacitive retention of 90% was obtained, which expresses outstanding cyclic stability of the real device. A theoretical study was performed to investigate the capacitance and diffusion-controlled contribution in the device performance using Dunn's model. The maximum diffusion-controlled contribution of 85% was found at 3 mV s⁻¹ scan rate. The study demonstrates the utilization of ternary metal phosphates as self-supported electrode materials for potential energy storage applications.