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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.

New era heteroatom-doped carbons, relying on different biomass residues, play a rising role in contemporary carbon energy storage technology. Herein, an abundant waste of viticulture industry – vine shoots (VS) was carbonized and examined as electrode material for supercapacitors with non-conventional aqueous electrolyte. Biochar obtained by pre-carbonization treatment of vine shoots (at 300 °C) is impregnated with ZnCl2 at 600 °C (ACvs600) and 700 °C (ACvs700), to synthesize carbon with developed specific surface area, close to 1500 m2 g−1. The high specific capacitance of ACvs is achieved in Al-based electrolyte, which allows working voltage of 1.8 V ACvs700/Al2(SO4)3/ACvs700 cell delivers the energy density of 24 Wh kg−1 at 1 A g−1, which is higher than one measured in typical Na2SO4 (∼16 Wh kg−1) and H2SO4 electrolyte (∼11 Wh kg−1). By using Trasatti&Dunn surface charge distribution models, the reallocation of inner vs. outer charge in Al-based electrolyte is found to be different from that in H2SO4 electrolyte. The nature of the interaction between pristine/defective graphene and hydrated Al3+ ion is examined by Density Functional Theory (DFT) and discussed. Gathered experimental and theoretical data open novel perspectives for using carbon in more sustainable energy storage devices.

International audience; Rechargeable magnesium batteries are gaining a lot of interest due to promising electrochemical features, which, at least in theory, are comparable than those of Li-ion batteries. Such performance metrics can be achieved by using thin metal foils or high-capacity alloys coupled with suitable electrolytes enabling a high Coulombic efficiency and use of a high energy density cathode materials. All three components significantly influence electrochemical characteristics and energy density of rechargeable magnesium batteries. Although there are many reports showing progress in the cyclability and stability of different systems, only few cathode materials promise possible commercialization. Remaining issues with efficiency, magnesium anode processing and electrolyte compatibility with cell housing are preventing faster development of technology with high possible impact on the future battery landscape. In the given perspective paper a critical overview on electrolytes, anode materials and three different classes of cathode materials is reported. Different rechargeable magnesium battery configurations were assumed and their dependence of volumetric energy densities on gravimetric energy densities are provided assuming realistic conditions with optimized electrode thicknesses and loadings, electrode porosity and optimized electrolyte quantity. Although calculated values are attractive, further experimental steps are needed in order to prove these numbers on the lab-scale and small prototype cells.

Herein a novel solvothermal synthesis approach for preparing poly(hydrobenzoquinonyl-benzoquinonyl sulfide) polymer (PHBQS) using sulfur and hydroquinone is presented. We investigate and compare electrochemical activity of this polymer as a cathode in Li and Mg battery systems. In the Li system we retain more than 160 mAh/g after 340 cycles, while in the Mg system a discharge voltage of approximately 2.0 V vs. Mg is achieved. This represents a significant increase in working voltage of Mg organic battery over majority of previously reported Mg organic batteries. The maximum specific capacity of 158 mAh/g is achieved in MgCl2-Mg(TFSI)2 tetraglyme:1,3-dioxolane electrolyte. Keywords: Organic battery, Mg battery, Mg(TFSI)2, Solvothermal synthesis

Based on careful analysis of nine papers by different research groups, we show, for the first time, that in LiFePO4-based cathode materials the electrode resistance depends solely on the mean particle size. The effect of carbon coating is marginal, it suffices that each LiFePO4 particle is point-contacted with a reasonable number of carbon black particles usually added in the course of electrode preparation. We present a simple but general theoretical model that consistently explains this unexpected result. The main reason for the relatively small importance of carbon coatings is the fact that the ionic conductivity (ca. 10−11–10−10 S cm−1 at RT) is much smaller than the electronic (>10−9 S cm−1 at RT). The present finding could be of significant importance not only for further optimization of LiFePO4 cathodes, but also for preparation of other cathode materials in which the ionic conductivity is much lower than the electronic. Keywords: LiFePO4, Particle size, Carbon coating, Wiring, Electrode resistance, Transport kinetics

Recently, preparation and preliminary testing of Li2FeSiO4, a representative of a new class of Li storage materials, has been reported [A. Nyten, A. Abouimrane, M. Armand, T. Gustaffson, J.O. Thomas, Electrochem. Commun. 7 (2005) 156]. In the present paper, we report preparation of another material from this class: Li2MnSiO4. To the best of our knowledge, the existence of this compound has not been reported so far. Similarly as in the case of the LiMPO4 materials family (M = Fe, Mn), the Mn analogue shows considerably poorer electrochemical performance. Quite unexpectedly, however, the Mn analogue shows a better stability, especially under harsh conditions. This property appears to be crucial for determination of detailed structural features of this class of materials. The obtained structure reveals partial occupation of alternate tetrahedral sites by Li and Mn, thus implying a high ionic conductivity of these materials. The poor electrochemical performance is most likely due to poor electron wiring. Keywords: Lithium-ion battery, Manganese silicate, Iron silicate, Cathode material, Crystal structure

A composite powder Li2FeSiO4/C is synthesized through a solid state reaction at 750 °C. The Rietveld crystal structure refinement is done in the monoclinic P21/n space group. It is found that the crystal structure is prone to “antisite” defect where small part of iron ion occupies exclusively Li(2) crystallographic position, of two different lithium tetrahedral positions (Li(1) and Li(2)). This finding is also confirmed by Mössbauer spectroscopy study: the sextet evidenced in the Mössbauer spectrum is assigned to the iron ions positioned at the Li(2) sites. A bond-valence energy landscape calculation is used to predict the conduction pathways of lithium ions. The calculations suggest that Li conductivity is two-dimensional in the (101) plane. Upon galvanostatic cyclings the structure starts to rearrange to inverse βII polymorph. Published version: [https://technorep.tmf.bg.ac.rs/handle/123456789/5787] This is the peer-reviewed version of the following article: Jugović D, Milović M, Ivanovski VN, Avdeev M, Dominko R, Jokić B, Uskoković D. Structural study of monoclinic Li2FeSiO4 by X-ray diffraction and Mössbauer spectroscopy. in Journal of Power Sources. 2014;265:75-80. [https://doi.org/10.1016/j.jpowsour.2014.04.121]