<p>Battery energy storage systems (BESSs) require insulation materials capable of simultaneously dissipating heat and maintaining reliable electrical insulation under high electric fields and elevated temperatures. Conventional polymeric insulation materials exhibit this excellent dielectric strength and processing characteristics, but they possess low thermal conductivity, ranging from 0.1 to 0.6&#xa0;W&#xa0;m⁻¹&#xa0;K⁻¹, which minimizes their potential for thermal management in battery modules. Thermally conductive dielectric polymer composites (TCDPCs) have therefore emerged as promising materials for BESS thermal management. Among the various nanofiller systems investigated, two-dimensional (2D) insulating nanofillers have attracted increasing attention because their high aspect ratio and layered structures facilitate efficient phonon transport while preserving electrical insulation. This review discusses the TCDPCs filled with 2D insulating nanofiller systems for thermal management in BESS applications. The representative 2D insulating nanofiller systems, such as hexagonal boron nitride, aluminum nitride nanosheets, mica, layered silicates, and oxide nanosheets, are discussed in terms of their nanofiller structures and thermal conductivity properties. The relationships between nanofiller structures, interlayer engineering, insulating material reliability, and thermal conductivity properties are critically examined. The challenges faced in the TCDPCs are also discussed in this review. The emerging nanofiller systems, such as hybrid nanofiller materials, multiple-layered configurations, and scalable processing techniques, are emphasized to improve the reliability of the thermal resistance materials for the next-generation BESS.</p> Graphical Abstract <p></p>