Energy Storage Systems: ECs

Energy storage systems provide a wide array of technological approaches to managing our power supply in order to create a more resilient energy infrastructure and bring cost savings to utilities and consumers. There are different energy storage categories currently being deployed as pumped hydropower, thermal, mechanical, electrochemical, and electrostatic storage.

Advances in technology and materials have greatly increased the reliability, output, and density of modern battery systems, and economies of scale have dramatically reduced the associated cost. Continued innovation has created new technologies like electrochemical capacitors that can be charged and discharged simultaneously and instantly and provide an almost unlimited operational lifespan.

Electrochemical capacitors (ECs) have attracted research interest worldwide because of their potential applications as energy storage devices in many fields. This type of electrochemical devices has considerably higher specific powers and longer cycle lifetimes compared to most rechargeable batteries, such as lead-acid, nickel-metal hydride, and Li-ion batteries. ECs have also appealed to considerable interest because of the ever-increasing demands of electric vehicles, portable electronic devices, and power sources for memory backup, and due to environmental concerns. This type of renewable energy systems is predicted to increase, boosting even further the growth of the market.

Markets and applications for electrochemical capacitors are growing rapidly and applications related to electricity grid will be part of that growth. During the period 2021-2028, the ECs market is expected to develop at a CAGR of 23.9%, according to the forecasts of different consultancy firms. The ECs market was valued at USD 5.02 billion in 2021 and is expected to reach USD 22.50 billion by the end of 2028.

Current commercial ECs production is focused on symmetrical construction methods using active carbon electrodes and flammable electrolytes. There is a deep need for new energy storage devices along with new chemistries and new materials to empower them. The research is moving forward to hybrid systems. The market is demanding new hybrid solutions that are sustainable, competitive, and safe. At this point, hybrid ECs offering an asymmetric construction method and seeking the best specific power versus specific energy response.

Fig. 1 Ragone plot illustrating the performances of specific power vs specific energy for different electrical energy-storage technologies. Times shown in the plot are the discharge time, obtained by dividing the energy density by the power density. Y. Shao, M. F. El-Kady, J. Sun, Y. Li, Q. Zhang, M. Zhu, H. Wang, B. Dunn, and R. B. Kaner, Design and Mechanisms of Asymmetric Supercapacitors, Chem. Rev. (2018).

The penetration of ECs will help to improve the current state of the art devices in the Ragone plot offering better energy versus power profiles. Ragone plot illustrating the performances of specific power versus specific energy for different electrical energy storage technologies. Times shown in the plot are the discharge time, obtained by dividing the energy density by the power density.

Nowadays, ECs are found in Micro-Smart Grids, covering peaks of Energy demands, elevators or cranes, where energy is required in a short space of time (great alternative for power demands), and in Automated Guided Vehicle (AGV)/Rail Guided Vehicle (RGV) among some industrial applications. Kinetic energy recovery systems (KERS) or start-and-stop solutions are also an ideal application for ECs in electric vehicles.

Also, electrochemical capacitor technologies can be used as a stand-alone secondary energy storage device or complementing batteries to increase their lifetime. These energy storage devices will further facilitate a switch to electrified transport, of great interest in countries with high levels of air pollution because the emission of polluting gases from electric vehicles is zero at the point of use.

There is a great dependency of lithium-ion technology, that correlates with a remarkable dependency on lithium as a raw material and organic electrolytes. The redesign of the cell architecture (hybrid ECs) is essential to drive both competitiveness and sustainability, while increasing the energy density.

Fig. 2 Comparative performance of High Power between current LiB and future Pseudocapacitors (hybrid electrochemical capacitors).

Different prospective electric applications, particularly electric vehicles, will require ECs. Even in the midst of the epidemic, electric vehicles have outperformed all industry predictions, growing by 40% year over year. Automakers sold 6.6 million plug-in vehicles in 2021, more than double the 3 million sold in 2020, and more than triple the 2.2 million sold in 2019, according to the IEA. Conventional car sales, on the other hand, have reached an all-time low, with global economic declines of 16% in 2021.

The active material can be considered as the most important component of the electrode, as its surface is responsible for the actual energy storage in the device. Novel materials such as graphene are needed to raise the energy density of electrochemical capacitors so that they can compete with batteries in energy price (€/kWh) in new application areas. Commercially available ECs have a high energy cost of approximately 4500 €/kWh while Lithium-ion batteries have an energy cost of 100–150 €/kWh depending on the exact cell chemistry.

The performance of graphene is better than other materials as activated carbons, graphitic carbons, or nanotube carbons.  Gnanomat has designed a family of hybrid nanomaterials that have shown more than a remarkable capacitance performance versus current market standard electrode materials due to the pseudocapacitance contribution by the metal oxide nanoparticles in combination with graphene and other carbon-based materials.

Gnanomat´s highly sustainable, safety and eco-friendly advanced materials emerge as perfect candidates to manufacture electrodes, capable of offering the most appropriate balance between energy density and power density in energy storage systems, solving costs, and performance issues. Besides, our technology has proved its industrial viability for manufacturing our nanomaterials at pre-industrial scale.

Pic. 1 Gnanomat electrochemical capacitor cells.

Our last technology developments in this field focus on asymmetric construction methods where one electrode is an activated carbon material with a high surface area and the other is a Gnanomat hybrid material with a pseudocapacitance contribution. In demonstration already conducted we have seen higher capacitance than can be achieved traditionally and the use of non-organic electrolytes will facilitate far higher levels of safety in operation.

Fig. 3 Specific capacitance of different Gnanomat hybrid nanomaterials compared to an activated carbon market standard electrode.

Key players in the supercapacitor market have moved onto digital technologies to support the next generation of electric infrastructure. Additionally, many new start-ups continue to work in new areas of efficiency, safety, digital connectivity, integration of new materials to promise rapid advancements of supercapacitor technology, and Gnanomat becomes your partner of choice to bring new materials and new supercapacitors to the industrial market.