HIgh POwer Asymmetric SuperCAPacitor in organic electrolyte – HIPASCAP
Nowadays, improving the energy efficiency of systems is an important objective for reducing fossil fuel consumption and CO2 emissions. Electrochemical energy storage systems are able to take an important part in this strategy, allowing lost energy to be recovered and further delivered on demand. Two types of electrochemical energy storage devices are available: accumulators and electric double-layer capacitors (EDLCs). Accumulators have a high energy density but a low power density, whereas EDLCs are able to deliver a high power, but their energy density is relatively low. Moreover, in Europe, the electrolyte for EDLCs is based on acetonitrile, which is highly flammable and noxious. For these reasons, strategies must be found for developing more performing systems satisfying the criteria of societal acceptability. Based on previous works of one of the partners (CRMD), the idea of the HIPASCAP project is to develop an industrial model of hybrid capacitor able to outperform the presently commercialized EDLCs in terms of energy density while keeping similar power density and cycle life. The hybrid capacitor combines lithium-ion battery type and electric double-layer materials for the negative and positive electrodes, respectively, while using alkycarbonates as electrolyte. Such a system is able to display twice the capacitance of an EDLC and a larger voltage; consequently, it results in a higher energy density than an EDLC, while being safer. The HIPASCAP multidisciplinary project involves 3 academic partners (CRMD, IS2M, CIME) and 2 industrial partners (TIMCAL and Batscap). The academic partners are internationaly recognized for their expertise in carbon materials, carbon electrochemistry and electrolytes. TIMCAL is a world-wide leader for carbon black and graphite products for batteries, supercapacitors and fuel cells. Batscap is specialized in the production and commercialization of high performance supercapacitors. One important task of the project will be to select electrode materials and electrolytes which allow high power density and cycle life to be withstood for fulfilling the requirements imposed by the supercapacitors producer (Batscap). In order to reach these objectives, special graphites will be developed by TIMCAL and IS2M for the negative electrode, activated carbons will be designed by IS2M and CRMD for the positive electrode, whereas electrolytes including lithium salts dissolved in alkyl carbonates and specific additives will be developed by CIME in order to improve the electrochemical performance, cycling ability and durability of the cells. Two kinds of cells will be developed: i) laboratory-type coffee-bag cells which will allow the optimized components (electrode materials, electrolyte, separator) to be implemented in a system mimicking the industrial ones; ii) small industrial demonstration cells allowing the real performance of this new type of device to be established. The expected results are to obtain better energy density than symmetric EDLCs while keeping the same power density and cycle life. The targets are one order of magnitude gain on energy density (both volumetric and gravimetric) and a reduced cost (less than 0.01€/F for large volumes). As the new system will use alkylcarbonates, we expect that the HIPASCAP project will have very positive impacts on the point of view of environment and security, while offering high energy efficiency.
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