Why Are Lithium-Ion Batteries And Supercapacitors Combined? Optimize Hess For Power & Longevity

The fundamental driver for combining lithium-ion batteries and supercapacitors in a Hybrid Energy Storage System (HESS) is the need to bridge the gap between long-term energy capacity and immediate power delivery. While lithium-ion batteries are excellent at storing large amounts of energy for extended use, supercapacitors excel at releasing energy rapidly. By integrating both, engineers create a system that can sustain long runtimes while simultaneously satisfying the intense, instantaneous power demands of dynamic loads like electric motors.

The core value of this hybrid architecture lies in its complementary nature: the battery acts as a deep reservoir for endurance, while the supercapacitor functions as a high-speed buffer to handle power spikes, effectively shielding the battery from stress.

Leveraging Complementary Physics

To understand why this combination is effective, one must look at the distinct physical characteristics of each component.

The Role of High Energy Density

Lithium-ion batteries provide the system with high energy density.

This property is responsible for the system's endurance, allowing it to supply energy over a long duration. The battery is the "marathon runner" of the pair, ensuring the application remains operational for extended periods without recharging.

The Role of High Power Density

Supercapacitors provide the system with high power density.

Unlike batteries, which release energy steadily, supercapacitors can discharge and recharge rapidly. This makes them the ideal "sprinter," capable of handling sudden, intense bursts of current that would otherwise overwhelm a standalone battery.

Solving the Dynamic Load Challenge

In practical applications, such as those involving Brushless DC (BLDC) motors, power needs are rarely constant.

Handling Startup and Acceleration

Motors require significantly more power during startup and acceleration than they do during steady operation.

The hybrid system routes these instantaneous high-current demands to the supercapacitor. This ensures the motor gets the immediate power it needs to accelerate without causing a voltage sag or performance drop in the main energy supply.

Protecting Battery Health

Drawing high currents directly from a lithium-ion battery can be detrimental to its internal chemistry.

By offloading peak loads to the supercapacitor, the HESS configuration acts as a protective buffer. This significantly mitigates the impact of high currents on the battery cells, thereby preserving their capacity and extending the overall lifespan of the battery pack.

Understanding the System Trade-offs

While a hybrid system offers superior performance, it is designed to overcome specific limitations inherent in single-source energy storage.

The Limits of Standalone Batteries

Relying solely on lithium-ion batteries for high-power applications often results in oversized, inefficient systems. To handle peak currents without a supercapacitor, the battery pack would typically need to be much larger than necessary just to meet the power requirement, leading to wasted weight and volume.

The Limits of Standalone Supercapacitors

Conversely, a system relying only on supercapacitors would lack endurance. While they can deliver massive power, they cannot store enough energy to sustain operations for practical lengths of time, making them unsuitable as a primary energy source.

Making the Right Choice for Your Design

When designing a power system, the decision to implement a HESS depends on the specific profile of your load.

If your primary focus is steady-state endurance: Prioritize the lithium-ion component to maximize energy density for long-term supply, using the supercapacitor only if minor fluctuations exist.
If your primary focus is dynamic performance: Leverage the supercapacitor's high power density to handle frequent startups, aggressive acceleration, or pulsed loads without degrading the main battery.

Ultimately, combining these technologies allows you to decouple energy requirements from power requirements, ensuring both peak performance and maximum component longevity.

Summary Table:

Feature	Lithium-ion Battery	Supercapacitor	Role in HESS
Energy Density	High	Low	Provides long-term endurance
Power Density	Low	High	Handles rapid current bursts
Cycle Life	Moderate	Excellent	Absorbs stress to extend system life
Response Time	Slower	Instantaneous	Smooths out dynamic load spikes

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References

Zeynep Tüfek, Emrah Çetin. Investigation of the Power System Including PV, Super Capacitor and Lithium‐Ion Storage Technologies Under BLDC Motor Load. DOI: 10.1002/bte2.20240064

This article is also based on technical information from Kintek Press Knowledge Base .