Integrated thermal management strategies for electric vehicles: a system-level review of battery cooling, heat pump technologies, PCM integration, and cold-climate performance

Abstract The transition toward sustainable transportation has intensified the need for advanced thermal management solutions to ensure the safety, performance, and energy efficiency of electric vehicles under diverse operating and environmental conditions. This review systematically examines recent developments in battery thermal management systems, encompassing air and liquid cooling, hybrid and phase change material-based strategies, as well as refrigerant-driven and heat pump integrated architectures. Comparative assessment of experimental and simulation-based studies indicates that liquid cooling systems can reduce peak battery temperature by approximately 15–30% relative to conventional air cooling approaches, while advanced cold plate designs improve temperature uniformity, maintaining cell-to-cell temperature differences below 5 °C. Hybrid liquid phase change material configurations provide additional benefits by suppressing transient thermal spikes and enhancing thermal buffering, thereby contributing to improved thermal stability and extended battery lifespan. The review further highlights the influence of refrigerant selection and heat pump integration on overall system efficiency. Low global warming potential refrigerants, including R1234yf, R290, and R744, enable environmentally sustainable operation, with reported enhancements in cooling or heating performance of up to 10–25%, depending on system design and operating conditions. In cold climates, battery preheating strategies based on positive temperature coefficient elements, waste heat recovery, and model predictive control significantly improve low-temperature performance, reducing preheating time by 40–55% and auxiliary energy consumption by 15–30% compared to conventional resistive heating. By synthesizing quantitative performance metrics across cooling, heating, refrigerant, and control domains, this review provides a unified framework for evaluating BTMS technologies and identifying trade-offs related to efficiency, safety, and sustainability. The findings underscore hybrid cooling architectures, low-GWP refrigerants, and intelligent control strategies as key enablers for next-generation EV thermal management systems capable of reliable operation across extreme climates with minimized energy and environmental impacts.