Development of high-performance Li batteries with autonomic thermal regulation of their performance by encapsulated nanosized phase change materi

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Phase change materials (PCMs) are an efficient group of materials for use in thermal management without the need for an external thermal regulation system. PCMs take advantage of latent heat to store and release thermal energy when a phase change occurs due to a change in temperature to the surroundings. PCMs have been previously applied to building materials and some electronics to sustain temperatures during operation as well as extensive use in the solar energy sector. In this project, inorganic salt hydrates (AxBy.n(H2O)) and metals with low melting points will be used as solid-liquid PCMs to automatically regulate the internal temperature of a lithium-ion battery. Currently, external cooling systems are used to prevent lithium ion batteries from reaching dangerous temperature (above 60C) preventing thermal runaway. There have been limited attempts to use PCMs in external cooling systems to sustain working temperatures between 25 and 30C which would be optimal for Li-ion batteries.Inorganic PCMs have double the heat storage capacity per unit volume and are also cheaper in comparison to their organic counter parts; making them an ideal candidate for investigation. Latent heat is absorbed when the salt hydrates undergo a phase change losing part or all of their waters. Latent heat is then released when the salt hydrate is recrystalised. There are issues with using inorganic PCMs: change of volume during phase change, poor thermal conductivity, supercooling and corrosive properties. Additives, such as nucleating agents can be used to reduce supercooling. For the other draw backs, encapsulation methods can be applied. Encapsulation can be useful to protect the PCM and the container from leaking as well as additional functionality, such as increased thermal conductivity, being applied to the shell. Nanosized core shell PCMs have a greater surface to volume ratio and so are extremely efficient for heat transfer.The aim of this project is to use nanosized encapsulated core shell inorganic PCMs to maintain the internal temperature of a lithium ion battery. The encapsulated PCMs will be inserted directly into the battery to maintain heat. The objective of the project would be to use encapsulated PCMs to regulate the internal temperature of a battery between 25-30C to optimise performance. If successful, it is hoped the encapsulated PCMs would reduce the need for external cooling systems that add additional mass and strain to current battery systems making them more efficient.