# Multifunctional and Flexible Phase Change Composites for Dual‐Mode Thermal Management of Lithium‐Ion Batteries

## TL;DR

Flexible phase change composites are developed to manage heat in lithium-ion batteries, offering both heating and cooling functions for improved performance and safety.

## Contribution

Development of multifunctional, flexible phase change composites with dual-mode thermal regulation for lithium-ion batteries.

## Key findings

- PCCs enable Joule heating at 22.5°C/min to prevent lithium plating in cold conditions.
- PCCs provide passive cooling and maintain LIB operating temperature across high power outputs.
- Integration of carbon nanofillers increases thermal conductivity by 240%.

## Abstract

Phase change materials (PCMs) are highly renowned for their substantial latent heat capacity, enabling efficient thermal management in applications such as buildings, wearable devices, and lithium‐ion batteries (LIBs). However, conventional PCMs suffer from mechanical rigidity, leakage, and low thermal conductivity. In this study, multifunctional, flexible, and leakage‐proof phase change composites (PCCs) are developed to overcome these limitations and enable dual‐mode thermal regulation for all‐climate LIBs. The PCCs provide Joule heating (22.5 °C min−1) under subzero conditions to prevent lithium plating and restore capacity. Simultaneously, they deliver passive cooling to optimise the operating temperature of LIBs, acrosspower output scenarios (2C and 3C). The performance is further supported and validated through COMSOL simulations, which shed light on PCCs’ phase change behaviour, the working temperature, and the heat distribution of LIBs. The integration of carbon nanofillers significantly enhances thermal conductivity by 240% while maintaining structural integrity. Additionally, the PCCs can function as overheating switches and temperature sensors (7.2%/°C at 40–45 °C) through a positive temperature coefficient (PTC) effect. Featuring low thickness (≈550 µm), leakage proof, and mechanical flexibility, these PCCs present a promising solution for advanced thermal management for safer and more efficient LIB operation.

This study develops flexible, leakage‐proof phase change composites with dual‐mode thermal management for lithium‐ion batteries. The composites offer Joule heating, passive cooling, and temperature sensing. Simulations validate their performance and provide insights into material optimisation. Combining mechanical flexibility with intelligent thermal management, these materials are well‐suited for next‐generation batteries, flexible electronics, and wearable technologies.