Hierarchically nanostructured Co(OH)2/MXene/SiO2/n-docosane phase-change composites for enhancement of supercapacitor performance under in-situ thermal management

Electrochemical energy-storage devices usually suffer from performance deterioration at high operating temperatures due to exothermic redox reactions during the cyclic charge–discharge process. Aiming at addressing this crucial issue, we have developed a novel type of thermoregulatory electrode material based on the hierarchically nanostructured Co(OH)2/MXene/SiO2/n-docosane phase-change composite for enhancing electrochemical energy-storage performance of supercapacitors through in-situ thermal management. The resultant composite shows a regular spherical morphology and a layer-by-layer core-shell microstructure for the phase-change microcapsules anchored on MXene nanosheets, together with a well-defined nanostructured Co(OH)2 layer deposited on the surfaces of the microcapsules and nanosheets. Through a multilevel integration of phase change material (PCM) and electroactive materials in an electrode material, the microenvironmental temperature surrounding the working electrode can be regulated effectively, buffering the heat impact to supercapacitors at high temperature. The phase-change composite achieved a satisfactory latent heat capacity of over 130 J/g together with good thermal cycling stability for long-term use in thermal management of supercapacitors. Compared to conventional electrode material without a PCM, the thermoregulatory electrode material developed in the current work exhibits an increase in specific capacitance by 6.6% at 45 °C and in capacitance retention by 10.8% after 3000 charge-discharge cycles at 45 °C, suggesting better electrochemical energy storage performance and higher charge-discharge cycling stability at high operating temperature thanks to its in-situ thermal management effectiveness. This study provides a promising approach to developing high-performance electrode materials for supercapacitor application over a broad temperature range.