Preparation Of Azobenzene Phase Change Composites For Photothermal Storage

Using phase change materials（PCMs）for energy storage is an important method to achieve efficient energy storage and application of renewable energy.The change of environment temperature can drive the phase transition of PCMs to realize the energy storage and release.However,due to the limitations of their own structure,organic phase change materials have the problems of low energy density and difficult to control the phase change temperature,which makes them face great challenges in long-term storage and controlled heat release,hindering the application in the field of phase change energy storage.In view of the above problems,three kinds of long-chain azobenzene compounds with photoinduced photo-induced reversible solid-to-liquid transitions performance have been designed and synthesized successfully.Then it is compounded with phase change materials to obtain azobenzene phase change composite materials（Azo@Tde）with different azobenzene mole doping ratio.By the change of crystallization temperature of Azo@Tde before and after UV light（365 nm）charging,subcooling is introduced to help carry out the photo controlled thermal release of Azo@Tde at low temperature.This paper shows that Azo@Tde has great potential in controllable energy storage and release.The results show that the crystallization temperature of Azo@Tde can reach-6.7℃and the supercooling degree can reach 8.8℃,which shows that Azo@Tde has the controllable heat release performance at low temperature.By integration of photoisomerization and photo-induced phase change,the energy density of Azo@Tde could reach up to 207.5 J·g^-1,which proves that Azo@Tde has good energy storage capacity.The infrared thermal imager tracks the temperature change of the thermal release of photothermal energy storage device fabricated using Azo@Tde excited by blue light（420 nm）at low temperature.The results show that the temperature can be raised from-0.3℃to 3.7℃because of the heat release of Azo@Tde.This result successfully demonstrates the feasibility of light controlled heat release.In addition,with the help of this ring device,a micro thermal management system with optical control,recyclability and positioning is constructed to prove that the composite material enables solid-state photothermal recycling,which has guiding significance for the future energy application of energy storage materials in the deep space and other day night alternate extreme environment.