Phase Change Materials in Battery Systems

As the world moves towards widespread adoption of electric vehicles and renewable energy sources, developing efficient and safe battery systems has become a pressing need. Lithium-ion batteries have emerged as the dominant battery chemistry for these applications due to their high energy density and long cycle life. However, lithium-ion batteries face persistent challenges with thermal management and safety.
Overheating can cause lithium-ion battery cells to degrade faster and in some cases lead to catastrophic failure through thermal runaway. This is where phase change materials (PCMs) can play a major role in regulating battery temperature and improving safety.

What are Phase Change Materials?

Phase change materials are substances with a high heat of fusion that can absorb and release large amounts of energy during phase transitions between solid and liquid states. The most common PCMs used in battery systems are paraffin waxes and fatty acids.
These materials melt at a desired temperature, absorbing heat in the process. When the ambient temperature drops, the PCM solidifies again, releasing the stored heat. This gives PCMs a built-in capability for passive thermal management through the absorption and release of latent heat during phase transitions.

PCMs can be integrated into battery systems in different ways.
Micro-encapsulated PCMs consist of small PCM droplets enclosed in a polymer shell and can be incorporated directly into battery cells.
Shape-stabilized PCMs use supporting materials like graphite foam or metal fins to provide structure for the PCM as it changes phase.
PCMs can also be implemented in macro-scale modules attached to battery surfaces or ventilation channels to manage heat at the full battery pack level.

Key Benefits of Using PCMs in Batteries

There are several important benefits PCMs offer for thermal management and safety in battery systems:

Passive thermal regulation
PCMs provide passive heating and cooling-capabilities to keep battery temperature within optimal operating range. This enhances battery lifecycle and reduces ageing effects.
Protecting against overheating
By absorbing excess heat during periods of high electrical loads or external high temperatures, PCMs prevent batteries from experiencing excessive internal temperatures and thermal runaway.
Smoothing temperature fluctuations
The high specific heat capacity of PCMs helps reduce temperature spikes within the battery during use, improving cell-to-cell thermal uniformity.
Enhancing safety
PCMs are non-toxic, non-flammable substances. This makes them inherently safer than some other battery cooling fluids, like oils or glycol mixtures.
Simplifying system design
PCMs allow batteries to operate safely with straightforward air cooling systems instead of more complex liquid cooling loops needed in many electric vehicles today.
Lightweight
Micro-encapsulated PCMs can be integrated into battery cells with minimal weight penalty. This helps maximize gravimetric energy density at the full battery pack level.
Compact
PCMs store large amounts of thermal energy in a small volume, preserving space within battery systems for optimal electrochemical cell stacking.

Quantifying the Impact of PCMs on Battery Performance

Our specialists have studied PCMs extensively to quantify their potential for improving battery thermal, safety, and lifetime performance. Thermal modelling provides insights into the dynamics of how PCMs absorb and release heat within battery systems during operation. Differential scanning calorimetry allows measuring PCM thermal properties like melting point, latent heat capacity, and phase transition temperatures. Accelerated ageing tests assess the impact of PCM thermal management strategies on extending battery lifespan by reducing time spent at elevated temperatures.

Physics-based models simulate internal current flow, electrochemical kinetics, and heat generation within battery cells coupled to PCM modules. These multi-physics models offer the most rigorous approach for design optimization of PCM enhanced battery systems. The models can be parameterized with different battery chemistries, PCM materials, cell sizes, operating conditions, and thermal management architectures. We can so identify optimal PCM solutions for a given battery application and quantify impacts on temperature profiles, charge/discharge performance, lifecycle, and safety margins.

Ongoing Research and Development

Several promising PCM materials and integration strategies have emerged from recent studies on lithium-ion, nickel-metal hydride, and lead-acid batteries:

Organic PCMs
Paraffin waxes, fatty acids, and sugar alcohols meet requirements for high latent heat and suitable phase change temperatures.
Inorganic PCMs
Salt hydrates and metals like aluminium or magnesium have potential for further improving heat storage capacity.
Encapsulation
Nano-scale encapsulation maintains PCM droplet geometry during phase changes to maximize heat transfer.
Porous media
Graphite foam or metal matrix structures give favourable shape-stabilization and thermal conductivity when filled with PCM.
Integrated cooling plates
Macro-scale PCM heat exchangers offer simple thermal regulation at the full battery pack level.

Takeaway

As battery technologies continue advancing to meet expanding demands, phase change materials (PCMs) present a promising thermal management solution. From smoothing temperature fluctuations to preventing catastrophic failures, PCMs offer a multifaceted approach for enhancing battery safety, lifetime, and performance. Ongoing research and development will further reveal the full potential of phase change materials to enable the widespread adoption of the next generation of batteries.

At CLOU, we're always one step ahead in energy storage innovation. Our advanced battery systems integrate the latest in thermal management technologies to ensure optimal performance and safety. Whether you're working on large-scale grid integration or reliable backup power, we have solutions designed for efficiency and longevity. Contact us for more information.