High performance of symmetric micro supercapacitors based on silicon nanowires using N-methyl-N-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide as electrolyte

This work describes the development and performance of a symmetric microsupercapacitor made of nanostructured electrodes based on silicon nanowires (SiNWs) deposited using chemical vapor deposition (CVD) on silicon substrates. The performance of the SiNWs micro-supercapacitor employing an aprotic ionic liquid (N-methyl-N-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide) (PYR13TFSI) as an electrolyte was able to deliver a maximal power density of 182 mW cm-2 and a specific energy of 190 µJ cm-2 operating at a wide cell voltage of 4V with a quasi-ideal capacitive behaviour. The lifetime of the device exhibited a remarkable electrochemical stability retaining 75 % of the initial capacitance after several million galvanostatic charge-discharge cycles at a high current density of 1 mA cm-2. Furthermore, a coulombic efficiency of approximately 99 % was obtained after galvanostatic cycling test without structural degradation on the morphology of SiNWs

High frequency response of adenine-derived carbon in aqueous electrochemical capacitor

Electrochemical capacitors are attractive power sources, especially when they are able to operate at high frequency (high current regime). In order to meet this requirement their constituents should be made of high conductivity materials with a suitable porosity. In this study, enhanced power and simultaneously high capacitance (120 F g−1 at 1 Hz or 10 A g−1) electrode material obtained from carbonized adenine precursor is presented. A micro/mesoporous character of the carbon with optimal pore size ratio and high surface area was proven by the physicochemical characterization. The beneficial pore structure and morphology resembling highly conductive carbon black, together with a significant nitrogen content (5.5%) allow for high frequency response of aqueous capacitor to be obtained. The carbon/carbon symmetric capacitor (in 1 mol L−1 Li2SO4) has been tested to the voltage of 1.5 V. The cyclic voltammetry indicates a good electrochemical response even at high scan rate (50 mV s−1). The cyclability of the capacitor is comparable to the one operating with commercial carbon (YP50F). The adenine-based capacitor is especially favourable for stationary applications requiring high power.Partners acknowledge M-ERA.NET network, MCIN/AEI/10.13039/501100011033 (Ref. PCI2019–103637), CIBER-BBN, ICTS ‘‘NANBIOSIS’’, ICTS ELECMI node "Laboratorio de Microscopias Avanzadas", National Science Centre, Poland (2018/30/Z/ST4/00901), and Ministrstvo za izobraževanje, znanost in šport for financial support and the grant of Ministry of Science and Higher Education in Poland, no. 0911/SBAD/2101. A.V., B.T., E.T. and R.D. additionally acknowledge financial support from the Slovenian Research Agency (ARRS) research core funding P2–0393.Peer reviewe

Hybrid aqueous capacitors with improved energy/power performance

This work reports on a high-voltage, hybrid capacitor involving two separate redox reactions. Aqueous solutions of Mg(NO3)2 and KI have been used for negative and positive electrode, respectively. Adjusting pH=2 for electrode (+) with KI solution and modifying Mg(NO3)2 solution to pH=9 for negative side play a crucial role for a stable long-term operation of capacitor at enhanced voltage. A benefit from such a construction is a pseudocapacitive contribution from hydrogen sorption reaction on the negative electrode and high iodine/iodide activity on the positive electrode, enhancing the energy with no remarkable impact on the power profile. Proposed solution allows a high voltage (1.8 V) to be reached and thereby high power and energy performance (~20 W h/kg at 1 kW/kg) to be obtained. High long-term stability has been confirmed by floating and galvanostatic tests

Supercapacitors: materials, systems and applications

Written by an international group of leading experts from both academia and industry, this is the first comprehensive book on the topic for 10 years. Taking into account the commercial interest in these systems and the scientific and technological developments over the past decade, all important materials and systems are covered, with several chapters devoted to topics of direct industrial relevance.The book starts by providing an introduction to the general principles of electrochemistry, the properties of electrochemical capacitors, and electrochemical characterization techniques. Ther

Comparative Study of Two Protic Ionic Liquids as Electrolyte for Electrical Double-Layer Capacitors

International audienceThis study describes preparation, characterization, application of two protic ionic liquids (PILs), Pyrrolidinium bis(trifluoromethanesulfonyl)imide ([Pyrr][TFSI]) and Diisoproyl-ethyl-ammonium bis(trifluoromethanesulfonyl)imide ([DIPEA][TFSI]),as electrolyte for supercapacitors. Their modelisation by Density Functional Theory shows that their most evident difference is the Cosmo Volume, and the structure dissymmetry of their cation. Physicochemical and electrochemical properties are discussed according to the cation structure. Ionic conductivity increases with temperature up to 8.4 and 17.3 mS cm−1 at 80°C while viscosity decreases to 20 and 12 mPa s, at 70°C for [DIPEA][TFSI] and [Pyrr][TFSI], respectively. Ionicity was then studied using the Walden diagram, showing that they are good ILs. Their behavior was then evaluated as electrolytes for supercapacitor, on activated carbon electrodes by cyclic voltammetry, galvanostatic cycling and Electrochemical Impedance Spectroscopy. Depending on the nature of binder used in electrodes preparation, a difference of wettability was observed. [Pyrr][TFSI] displays a better diffusivity on the electrode allowing good cycling capacitance (120 F g−1), whereas [DIPEA][TFSI] allows higher voltage (ΔE = 2 V) and specific energy. According to the results, the cation nature is a decisive parameter on PILs electrochemical behavior for supercapacitor systems