The widespread application of liquid immersion cooling in battery thermal management systems has made the long-term stability of cooling fluids a critical determinant of system safety and reliability. However, current research predominantly focuses on intrinsic fluid degradation or interactions with external components, while lacking systematic evaluation methods for fluid stability under perturbations induced by key battery materials. Consequently, an experimental platform and evaluation framework are needed to guide fluid selection and system reliability analysis by characterizing the stability of cooling fluids under multi-material disturbances.

An integrated experimental platform comprising pretreatment, accelerated aging, performance testing, and multidimensional evaluation was constructed. The investigation focused on three representative immersion cooling fluids: silicone oil (SO), mineral oil (MO), and synthetic ester (SE). Crucially, key materials from sodium-ion batteries, including aluminum foil, polypropylene separators, hard carbon anodes, layered oxide cathodes, and polyanion cathodes, were introduced as perturbation factors. Controlled liquid–solid contact systems were established and subjected to accelerated aging at 100 ℃ for 500 h to strengthen material-induced interactions and accurately assess relative stability, thereby revealing long-term compatibility issues within a shortened timeframe. After aging, the chemical, rheological, thermal, and electrical properties of the fluids were characterized through measurements of acid value, viscosity, thermal conductivity, dielectric loss, and volume resistivity, with each indicator reflecting a distinct aspect of fluid degradation. A multi-index evaluation matrix was then formulated based on performance deviations from blank-aged samples, and the entropy-weighted TOPSIS method was applied to comprehensively rank fluid stability.

Experimental results demonstrate that battery materials considerably perturb cooling fluid properties, with varying sensitivities across indicators. Acid value and dielectric properties exhibited the most pronounced responses to material interactions. Specifically, following high-temperature aging, the acid value of SO surged from 0.0122 mg KOH/g to 0.0562 mg KOH/g—an over 4.6-fold increase—whereas SE maintained superior chemical stability with minimal fluctuation. Viscosity variations were highly system-dependent: MO displayed substantial variation, decreasing by up to 36.2% under aluminum contact, while SE remained rheologically stable. Thermal conductivity showed negligible change across all systems, indicating relative insensitivity to material disturbances. Conversely, dielectric properties were markedly affected. For example, increased dielectric loss and diminished volume resistivity were observed across all fluids, with MO exhibiting the most severe electrical degradation. Comprehensive TOPSIS analysis confirmed that SE experienced the smallest performance deviation, thereby delivering optimal stability under multi-material perturbations.

The developed experimental platform facilitates a controlled investigation of cooling fluid stability under battery material perturbations. This approach yields an integrated methodology spanning experimental design, data acquisition, and multi-index evaluation, forming a coherent research framework. Findings confirm that material-induced interactions substantially degrade fluid properties and that a multiparameter fusion approach can effectively differentiate stability discrepancies. By emphasizing the performance retention capability of fluids in complex contact environments, this methodology provides a robust experimental foundation for cooling fluid selection and reliability assessments in immersion cooling systems. Furthermore, the platform’s inherent modularity and scalability support comparative studies across diverse cooling media and material systems, serving as a valuable tool for methodological advancement, experimental teaching, and experimental analysis in the fields of new energy safety and thermal management. This work advances safer, more reliable battery immersion cooling solutions.