Thermal management strategies for lithium-ion batteries in electric vehicles: A comprehensive review of nanofluid-based battery thermal management systems

• Recent studies in nanofluids preparation and stability are comprehensively reviewed. • Liquid BTMS optimisation involves structural, nanofluid and flow control parameters. • Effects of nanofluid type and concentration on BTMS performance are discussed. • Nanofluids demonstrated 2.9-30.5% thermal improvement compared to base fluids. • Research gaps for Nanofluid-Based BTMSs are identified. Electric vehicles have recently experienced rapid growth in battery heat generation rates due to increasing commercial demands for faster vehicle speeds and higher charging rates. This growth intensified the importance of innovative thermal management strategies to ensure safe and efficient vehicle operation. This paper aims to comprehensively review and discuss recent research investigating nanofluid battery thermal management systems (BTMS). Nanofluids are proposed as promising coolants as they possess enhanced thermal performance owing to their higher thermal conductivity compared to conventional fluids. Studies investigating nanofluid BTMSs can be divided into experimental and numerical studies investigating the effects of varying base fluid, nanoparticle type and concentration on thermal performance and pumping power. The overall trend of the reviewed studies displays an improvement in thermal performance with the increase of nanoparticles concentration, coupled with higher pumping power due to the higher viscosity values resulting in higher friction, with reviewed studies demonstrating nanofluids BTMS thermal improvements in the range of 2.9 – 30.5% with pressure drop increase in the range of 14 – 70% compared to the base fluid. The most commonly investigated types of nanoparticles are aluminium oxide (Al 2 O 3 ), copper oxide (CuO), and silver oxide (AgO), with concentrations in the range of 0.1 – 5%. The review highlighted the lack of long-term stability investigation and hybrid nanofluid BTMS studies in addition to studies evaluating the economic and environmental effects of utilising nanofluids in liquid BTMSs.