Research progress on nanofluids for battery thermal management

As climate change worsens, it is becoming increasingly important to effectively harness and store energy from non-fossil fuels to reduce greenhouse gas emissions. The increasing adoption of various rechargeable batteries is being driven by advancements in non-fossil energy, the development of energy storage technology, and electrification in technological fields such as electric vehicles, photovoltaic thermal energy storage, and aerospace technology. However, the compact size of batteries leads to a significant increase in their internal energy density and temperature. Elevated heat flux and temperature not only limit battery performance but also reduce lifespan and pose safety risks to battery systems. The occurrence of thermal runaway under extreme conditions is a concern as it can result in battery combustion or even explosion. Thus, the implementation of efficient battery thermal management systems is essential. Besides traditional methods such as air cooling, phase change materials, and liquid cooling, in recent years, various novel thermal management technologies, including heat pipes, nanoparticle-enhanced phase change materials, and nanofluids, have been extensively explored. Among these emerging technologies, nanofluid battery thermal management systems have garnered attention due to their significant impact, minimal additional energy consumption, and cost-effectiveness compared with alternative approaches. These systems utilize nanofluids, which are liquids with uniformly dispersed nanoparticles. Nanoparticles can contain oxides such as alumina and titanium dioxide, metals such as silver and copper, and carbon-based materials such as carbon nanotube and nanodiamond. The application of nanoparticles results in an improvement in the thermal conductivity of fluids. Moreover, nanoparticles can also supply extra nuclei, improve surface wettability, and delay bubble coalescence while boiling. Thus, nanofluids can enhance heat transfer in both single-phase and two-phase flows. Given the enhancement of heat transfer, nanofluids exhibit significant potential in battery thermal management. Herein, a systematic review of the research progress on nanofluid battery thermal management systems is presented. First, the structure, working principle, and demands of battery thermal management are given. Afterward, the concept and classification of nanofluids are introduced. Subsequently, the fundamental properties of nanofluids, such as stability, viscosity, thermal conductivity, and electrical conductivity, are elucidated. The article further discusses the current research progress on nanofluid-based battery thermal management systems applied in lithium batteries, fuel cells, and photovoltaic batteries. Finally, some notable challenges associated with nanofluid battery thermal management systems and some future development directions on numerical and experimental research and industrial applications are outlined.