Solid ionic conductors are actively sought for their potential application in electrochemical devices, particularly lithium batteries. We have found high ionic conductivity for a large variety of salts dissolved in the highly polar medium based on the plastic-crystal form of succinonitrile (N[triple bond]C[bond]CH(2)[bond]CH(2)[bond]C[triple bond]N). Its high diffusivity, plasticity and solvating power allowed the preparation of a large number of materials with high ionic conductivity, reaching values of 3 mS cm(-1) at 25 degrees C (two orders of magnitude above polymers). Their ease of preparation and processing allowed us to study the influence of the solute on ionic conduction within this medium. Comparisons revealed a dichotomy between plastic crystals and conventional polymer media. The usefulness of these new, easily processed electrolytes was asserted in electrochemical tests with lithium intercalation electrodes.
A new class of selenium and selenium-sulfur (Se(x)S(y))-based cathode materials for room temperature lithium and sodium batteries is reported. The structural mechanisms for Li/Na insertion in these electrodes were investigated using pair distribution function (PDF) analysis. Not only does the Se electrode show promising electrochemical performance with both Li and Na anodes, but the additional potential for mixed Se(x)S(y) systems allows for tunable electrodes, combining the high capacities of S-rich systems with the high electrical conductivity of the d-electron containing Se. Unlike the widely studied Li/S system, both Se and Se(x)S(y) can be cycled to high voltages (up to 4.6 V) without failure. Their high densities and voltage output offer greater volumetric energy densities than S-based batteries, opening possibilities for new energy storage systems that can enable electric vehicles and smart grids.
Electrical energy storage for transportation has gone beyond the limit of converntional lithium ion batteries currently. New material or new battery system development is an alternative approach to achieve the goal of new high-energy storage system with energy densities 5 times or more greater. A series of SeSx-carbon (x = 0-7) composite materials has been prepared and evaluated as the positive electrodes in secondary lithium cells with ether-based electrolyte. In situ synchrotron high-energy X-ray diffraction was utilized to investigate the crystalline phase transition during cell cycling. Complementary, in situ Se K-edge X-ray absorption near edge structure analysis was used to track the evolution of the Se valence state for both crystalline and noncrystalline phases, including amorphous and electrolyte-dissolved phases in the (de)lithiation process. On the basis of these results, a mechanism for the (de)lithiation process is proposed, where Se is reduced to the polyselenides, Li2Sen (n ≥ 4), Li2Se2, and Li2Se sequentially during the lithiation and Li2Se is oxidized to Se through Li2Sen (n ≥ 4) during the delithiation. In addition, X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy demonstrated the reversibility of the Li/Se system in ether-based electrolyte and the presence of side products in the carbonate-based electrolytes. For Li/SeS2 and Li/SeS7 cells, Li2Se and Li2S are the discharged products with the presence of Se only as the crystalline phase in the end of charge.
The sodium battery has the potential to be the next generation rechargeable system which utilizes cheaper and more abundant sodium material but affords nearly the same power as lithium batteries. One of the key barriers for the sodium battery is the lack of stable anode materials which can insert sodium ions reversibly at relatively low potential. This contribution reports the sodium insertion in a series of organic carboxylate based materials: (C
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.