The shell composition and microstructure of microencapsulated phase-change materials (MPCMs) are of vital significance for achieving high thermal and mechanical properties. Herein, a new type of MPCM with double-walled shells (melamine-formaldehyde (MF) resin/carbon nanotube (CNT)-poly(4-styrenesulfonic acid) sodium (PSS)) was developed through a facile layer-by-layer (LbL) self-assembly technique using prefabricated MF resin-encapsulated n-octadecane as the template. The CNTs were well dispersed and highly interconnected in the shell, which greatly enhanced the temperature response and thermal stability of MPCMs. Furthermore, the incorporation of 3.34 wt% CNTs resulted in an average hardness and Young's modulus of MPCMs, respectively, 3.3 and 1.3 times greater than those of microcapsules without CNTs. The double-walled MPCMs exhibited good potential for application in the field of thermal energy storage.

The application of thermal energy storage with phase change materials (PCMs) for energy efficiency of buildings grew rapidly in the last few years. In this research, octadecane paraffin was served as a PCM, and a structural concrete with the function of indoor temperature control was developed by using a macro-encapsulated PCM hollow steel ball (HSB). The macro-encapsulated PCM-HSB was prepared by incorporation of octadecane into HSBs through vacuum impregnation. Test results showed that the maximum percentage of octadecane carried by HSBs was 80.3% by mass. The macro-encapsulated PCM-HSB has a latent heat storage capacity as high as 200.5 J/g. The compressive strength of concrete with macro-encapsulated PCM-HSB at 28 days ranged from 22 to 40 MPa. The indoor thermal performance test revealed that concrete with macro-encapsulated octadecane-HSB was capable of reducing the peak indoor air temperature and the fluctuation of indoor temperature. It can be very effective in transferring the heating and cooling loads away from the peak demand times.

With the ongoing advance of flexible energy storage products for commercial portable electronics application, the fundamental comprehension of the temperature-dependence for supercapacitors is in urgent demand. Although polypyrrole (PPy) has been extensively employed as electrodes for supercapacitor systems, their electrochemical response to extreme thermal environments is rarely discussed. In this work, PPy was rationally constructed on the surface of carbon cloth (CC) as electrodes and a type of high-performance flexible symmetric supercapacitor was assembled with a PVA-H₃PO₄ gel electrolyte. The electrochemical performance of the supercapacitors was systematically investigated at various surrounding temperatures from 0 °C to 60 °C using cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy measurements. The results demonstrated that the areal specific capacitance of the CC/PPy supercapacitor at 0.5 mA cm⁻² increased from 52.91 mF cm⁻² to 75.08 mF cm⁻² and the internal resistance fell by 71.4% when the operating temperature rose from 0 °C to 60 °C. Moreover, cycling stability dropped and the self-discharge behavior accelerated in the supercapacitors with the gradual increase in the external temperature. This study provides a fundamental understanding of the temperature-dependent pseudocapacitive performance of PPy-based flexible supercapacitors, which gives a valuable reference for energy storage system applications.