Supercapacitor, Lithium-Ion Combo Improves Energy Storage
Research demonstrates the energy-efficiency benefits of hybrid power systems combining supercapacitors and lithium-ion batteries.
Energy storage is evolving rapidly, with an increasing focus on enhancing efficiency and longevity in various high-power applications. Two fundamental components are lithium-ion batteries and supercapacitors, each with its own operating principles and benefits.
A supercapacitor. Image used courtesy of Skeleton Technologies
Recently, researchers in Germany investigated the potential of hybrid systems using batteries and supercapacitors working in tandem.
Supercapacitors vs. Batteries
Supercapacitors and lithium-ion batteries have unique properties and applications, but both are pivotal components in modern energy storage. In the power electronics field, it’s essential to understand how they work, their differences, and the scenarios where one might be preferable.
Diagram of a supercapacitor versus a lithium polymer battery. Image used courtesy of Farhan et al.
Supercapacitors store energy through a physical process, whereas batteries rely on chemical reactions. Supercapacitors comprise two electrodes immersed in an electrolyte separated by an ion-permeable membrane. When voltage is applied, ions in the electrolyte accumulate on the surface of the electrodes, creating an electrostatic field that stores energy. This mechanism allows for rapid charging and discharging, as it does not involve slow chemical reactions. For this reason, supercapacitors excel in delivering quick bursts of energy, making them ideal for applications requiring immediate power delivery, such as power grid stabilization or regenerative braking systems in vehicles.
Lithium-ion batteries, on the other hand, operate on a chemical principle. They consist of an anode (often made of graphite), a cathode (typically a lithium metal oxide), and an electrolyte. The electrolyte permits lithium ions to move between the electrodes. During discharge, lithium ions pass through the electrolyte from the anode to the cathode while electrons flow through the external circuit, providing electric power. The reverse occurs during charging. Lithium-ion batteries are celebrated for their high-energy density and ability to store substantial energy in a relatively small, light package. This attribute makes them suitable for applications where sustained energy delivery is crucial, such as in portable electronics, electric vehicles, and backup power systems.
The R&D Project: A Convergence of Technologies
In 2020, a consortium led by Skeleton Technologies, in collaboration with AVL Deutschland GmbH and the Fraunhofer Institute for Energy Economics and Energy System Technology, initiated a research project named SuKoBa. The project aimed to explore and quantify the benefits of combining lithium-ion batteries and supercapacitors. Researchers sought to develop tools and methods for designing and optimizing hybrid storage systems, particularly for high-power applications where traditional battery systems were less feasible.
The consortium's approach hinged on two pillars: a software toolbox and a physical demonstrator. The software toolbox was designed to determine the most cost-effective and long-lasting combination of supercapacitors and lithium-ion batteries for any given application and operational scenario. This toolbox, combined with real-life data from the scalable demonstrator, provided insights into the optimal integration of these two technologies.
One of the most compelling findings of the SuKoBa project was the significant improvement in system lifespan and overall efficiency when supercapacitors were integrated with lithium-ion batteries. For instance, adding supercapacitors in high-power applications like mining trucks led to a more than 20% extension in battery life at competitive system costs. The team accredits this to a reduction in electrical and thermal losses associated with the hybrid system, resulting in better energy storage efficiency.
Mining truck using a hybrid of supercapacitor and lithium-ion batteries. Image used courtesy of Skeleton
The project also demonstrated that hybrid systems are particularly beneficial in applications involving energy recuperation, like regenerative braking, where they effectively manage high peak power requirements. The economic efficiency assessment considered the improved lifespan and the costs of battery systems and supercapacitors. The results indicated that mining trucks gained the most, with an expense distribution of approximately 90% for lithium-ion batteries and 10% for supercapacitors in the hybrid system.
Future of Supercapacitor/Lithium-Ion Hybrids
The success of the SuKoBa project provides a blueprint for the future of hybrid energy storage systems. By effectively marrying lithium-ion batteries with supercapacitors, this initiative paves the way for more efficient, durable, and cost-effective energy storage solutions. As the technology progresses, it promises significant improvement in energy storage across an array of applications, from automotive to industrial machinery.