Lithium-ion batteries are becoming increasingly important in everyday life with an increase in the number of electric vehicles on the road. This has led to safety and lifetime concerns, which has been linked to the temperature that cells reach during operation with an ideal operational temperature of 20-30 °C. Outside of this optimal range, damaging cell processes occur that lead to loss in performance. At low temperatures slow intercalation kinetics can lead to lithium plating at the negative electrode which could lead to the short circuiting of the cell. At higher temperatures, a whole host of degradation processes are accelerated, such as dissolution of transition metals, breakdown of the solid electrolyte interphase, and stored lithium leaching from the graphitic electrode. These effects can severely damage the cell, limiting the cycle life and, in extreme cases, lead to thermal runaway, uncontrollable overheating, and eventually potential explosion. During operation, especially during abuse conditions such as fast charge or discharge, Li-ion cells generate heat through ohmic resistances and polarization resulting in increased internal temperatures. There have been attempts to reduce the heat production of Li-ion cells, however these methods have an impact on cost and functionality of the cells. To prevent the temperature of the cell becoming an issue, battery packs in electric vehicles (EVs) are installed with a battery thermal management system (BTMS). BTMSs are divided into three categories: active, passive and hybrid. Active BTMS, the most common BTMS currently in use, pump either air or liquid around the battery pack to remove the heat from the cells. To pump fluid, active BTMS require energy input from the battery pack to power the pumping system, with liquid being the most efficient active medium. Chen et al. demonstrated the same temperature reduction of a single cell using both liquid and air systems, requiring 0.15 mW and 115 mW of input energy, respectively. Another issue with current active BTMS is uneven temperature distribution. To prevent uneven aging of cells there should no more than a 5 °C temperature difference between cells within a battery pack. This is a particular problem in forced air cooling where, without proper space configuration of the cells, it has previously been reported a temperature gradient of 11 °C can be achived. Active BTMS are also generally heavy, reducing the gravimetric energy density of the battery pack and can have complex manufacturing processes raising their costs. Passive BTMSs do not require any additional energy input to function making them of interest as an improvement on current active BTMS designs. Passive systems have been shown to be up to 23% more efficient than liquid based systems and 15% more efficient than air based cooling methods. A class of materials that has been considered for a passive BTMS are phase change materials (PCMs). Organic PCMs have the ability to store over 200 J•g -1 for example, octadecane can store 220 J•g -1 , of latent heat during phase change which is stored and then released on the reverse phase change and as such has generate particular interest for BTMS. PCMs have been considered for BTMS for some time, however issues remain over integration.