Nanoflaky nickel-hydroxide-decorated phase-change microcapsules as smart electrode materials with thermal self-regulation function for supercapacitor application

A nanoflaky nickel-hydroxide-decorated phase-change microcapsule system [designated as Ni(OH)2-SiO2-MEPCM] was designed as a smart electrode material for supercapacitor application. This system was constructed through microencapsulating n-docosane core into a silica shell via emulsion-templated interfacial polycondensation, followed by fabricating a nanoflaky Ni(OH)2 layer on the surface of silica shell through structure-directed interfacial precipitation. Such a combination of phase-change microcapsules and electrochemically active material makes the Ni(OH)2-SiO2-MEPCM synchronously implement thermal self-regulation and electrochemical energy storage. The Ni(OH)2-SiO2-MEPCM shows a perfect core-shell structured morphology and well-defined nanoflaky surface microstructure. The Ni(OH)2-SiO2-MEPCM not only possesses a good temperature regulation capability with a latent-heat capacity of around 140 J/g but also exhibits an excellent thermal cycle stability and good high-temperature shape stability. Most importantly, compared to traditional electrode materials, the Ni(OH)2-SiO2-MEPCM can perform effective thermal self-regulation to regulate the micro-ambient temperature by its n-docosane core when used as an electrode material for supercapacitors, leading to improved electrochemical performance and good long-term cycle stability with capacitance retention of 86.2% after 3000 charge-discharge cycles at a high ambient temperature of 50 °C. All of these features indicate that the Ni(OH)2-SiO2-MEPCM developed by this work has great potential as a smart electrode material for electrochemical energy-storage applications.