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Ionic Liquid-based Hybrid Power Supercapacitors

The ILHYPOS project aims at developing green, safe, powerful and high-energy hybrid supercapacitors for application as peak power smoothing and energy recuperation devices in fuel-cell (PEM) powered electric vehicles and in small energy production plants (such as CHPs).

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The demand for clean energy is rapidly expanding worldwide and one of the most promising solutions is non-polluting energy production by fuel cells. Supercapacitors (SCs), due to their capability to deliver high specific power in a few seconds, are considered as electrical energy storage devices for smoothing the short-time power burst required in transport and stationary applications of fuel cells. Commercial SCs are double-layer carbon SCs (DLCS) which make use of electrolyte solutions consisting of a salt dissolved in an organic solvent, which permits relatively high operating voltages (around 2.5 V). The main drawback with these SCs is that the organic solvents do not often fulfil the requirements of environmental compatibility and safety for vapour generation, flammability and explosions. This is the case for DLCSs with acetonitrile-based electrolytes, which are the most common high-voltage DLCSs on the market. The high vapour pressure of these electrolytes requires a careful and expensive thermal control. Temperatures above 40°C, normal in fuel-cell vehicles and CHP (combined heat and power) systems, may cause the degradation of present SCs in terms of performance and safety. The volatility of organic solvents increases sharply with temperature, making SCs potentially unsafe beyond 50-60°C and, generally, non-environmentally friendly with the presence of polluting chemicals.


The hybrid SCs to be developed in ILHYPOS are based on the use of ionic liquids as electrolytes and on a novel hybrid configuration using electronic conducting polymers (ECPs) as positive electrodes. Ionic liquids are excellent ionic conductors, virtually non-volatile and thermally stable up to 300°C, with a high working voltage (in excess of 5 V). These properties make ionic liquids excellent candidates as electrolytes in SCs with improved performances: specific energy and power of about 15 Wh/kg and 7 kW/kg can be reached.

The objectives identified to overcome the limitations of present SCs, by searching for materials suitable for ionic liquid-based SCs, are:

  1. synthesis of ionic liquids with improved properties (ionic conductivity, electrochemical, chemical and thermal stabilities) at low temperatures (down to -20°C), as well as at 60°C and above
  2. synthesis of ECPs optimised for the use as positive electrodes
  3. identification of high surface area carbons (e.g. activated and aerogel) optimised for the use as negative electrodes
  4. investigation of the electrochemical performance of current collectors. Surface treatments will be developed onto the Aluminium current collectors to decrease the series resistance.
Finally, ILHYPOS SCs do not contain polluting chemicals, largely used in present SC (organic electrolytes substituted by ‘green’ ionic liquids), thus making them highly innovative products.

Example of foil production equipment
Example of foil production equipment

Description of work

The project structure logically streamlines and cross-links all the activities related to material R&D, material and cell component scale-up preparation, and design and prototype construction up to final application-specific testing in order to integrate expertise and equipment better, and to reach the project objectives efficiently and timely.

During Phase 1 (Electrode Materials R&D), academic and basic research organisations work on the optimisation of the electrode and electrolyte materials, significantly improving on the overall technical performances of each single component with respect to the present state of the art. With Phase 2 (Development and Production of SC Materials), the focus will be on the scale-up processes for optimising the material production. In Phase 3 (Application Requirements and Full-scale Prototype Production), a specific application study will be performed by two end users in collaboration with a research organisation as a hybrid vehicle configuration investigator, and, based on these studies, hybrid SC components will be designed and assembled in the final prototypes. In Phase 4 (Application Testing), testing procedures will be developed and used to verify the performance of the prototype experimentally with the respect to the project targets, which are competitive with present SC performance.


The expected results and deliverables from the ILHYPOS project are manifold and various in natures: scientific, technological and market-oriented with social and economical impacts. To reach the planned targets, the ILHYPOS participants will:

  • prepare ionic liquids in large amounts, demonstrated at a level of 50/100 grams and extended to the level of at least 2 kg per batch
  • prepare ECPs in large amounts, demonstrated at a level of 50/80 grams and extended to the level of at least 2 kg per batch
  • prepare electrodes in large amounts, demonstrated at a level of 1-10 cm² and extended to the level of at least 1 m² per batch
  • develop the LAMCAP® technology (soft-packaged laminated SCs), which should improve the performance of the hybrid SCs greatly (specific energy and power)
  • compare the performances obtained with the requirements for fuel-cell vehicles and CHP applications.

The ILHYPOS achievements will favour:

  • the positioning of Europe as a leader in the new field of high voltage and environmentally safe SCs and leadership in the field of ionic liquids
  • the relief from more polluting chemicals largely used in present SCs (organic electrolytes substituted by ‘green’ ionic liquids)
  • a green future based on hydrogen and fuel cells, by favouring a larger and faster introduction of cleaner vehicles, and small and more efficient delocalised power generation systems.
Synthesis route of low-temperature ionic liquids
Synthesis route of low-temperature ionic liquids