U.S. patent application 20190273295 (applicant Anhui Xinen Technology Co. Ltd., Anqing Anhui, China):
"Disclosed is a technique for managing the temperature of rechargeable cells. An energy storage device can include a plurality of rechargeable cells disposed within a housing and a material disposed within the housing so as to completely surround each of the rechargeable cells in a particular plane. The material can have a thermal characteristic such that the material remains a solid upon absorbing heat from the rechargeable cells by changing a crystal lattice structure. Intrinsic latent heat properties of the material result in absorption or release of heat to maintain a temperature of a rechargeable cell within a pre-defined temperature range. A regenerative mechanism including a heat pump coil can restore the material to a lower energy crystal lattice structure."