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[en] Herein, a new and facile synthesis of a tin-carbon nanocomposite and its electrochemical characterization is presented. Tin nanoparticles were embedded in micron-sized carbonaceous particles, thus successfully preventing the aggregation of tin nanoparticles and buffering the occurring volume strain, which accompanies the reversible (de-)alloying process. Such active material presents specific capacities of around 440 and 390 mAh g−1 for applied specific currents of 0.1 and 0.2 A g−1, respectively, as lithium-ion anode using environmentally friendly and cost-efficient carboxymethyl cellulose as binder. Even more remarkably, at very high specific currents of 2, 5, and 10 A g−1, electrodes based on this composite still offer specific capacities of about 280, 240, and 187 mAh g−1, respectively. In addition, this tin-carbon nanocomposite appears highly promising as anode material for sodium-ion batteries, showing very stable cycling performance in a suitable potential range, and specific capacities of more than 180, 150, 130, and 90 mAh g−1 for an applied specific current of 12.2, 122, 244, and 610 mA g−1, respectively, thus highlighting the high versatility of this composite active material for both Li-ion and Na-ion battery technologies
[en] Highlights: • Mn silicate hollow spheres are enclosed in reduced graphene oxide (rGO). • Manganese silicates provide advantageous de-/lithiation potentials with regard to energy density. • Mn silicate hollow spheres remain unaltered even after 350 full dis-/charge cycles. • The incorporation of rGO enhances the achievable capacity and rate capability. - Abstract: Herein is presented a new composite material consisting of nanostructured Mn silicate hollow spheres enclosed in a matrix of reduced graphene oxide (rGO), synthesized via a facile and low-cost hydrothermal method. The hollow structure provides free space to accommodate the volume expansion occurring upon lithiation, while the rGO facilitates the electron transport, thus enhancing the lithiation kinetics. Remarkably, the composite provides a continuously increasing reversible capacity up to ca. 1300 mAh g−1 after 350 cycles. This increase in capacity is ascribed in part to the steadily rising fraction of Mn2+/Mn3+ being oxidized to Mn4+ as well as the reversible formation of the solid electrolyte interphase. The particle morphology, in fact, remains unaltered, as evidenced by ex situ scanning electron microscopy – even after 350 cycles. Additionally, the implementation of manganese as transition metal for the reversible conversion reaction appears advantageous with regard to the overall electrochemical performance and the relatively lower lithiation potential.
[en] In an attempt to realize sodium-ion batteries with enhanced safety, we report herein the utilization of ionic liquid (IL)-based electrolytes for cycling nanoparticulate anatase TiO_2 as sodium-ion anode material. The use of the IL-based electrolyte results in the highly stable cycling performance of anatase TiO_2-based electrodes, providing an initial specific capacity of 159 mAh g"−"1 when applying a specific current of 33.5 mA g"−"1, and still 155 mAh g"−"1 after 80 full (dis-)charge cycles. Moreover, a very promising rate performance is obtained with specific capacities of 108 and 78 mAh g"−"1 for specific currents of 335 and 670 mA g"−"1, respectively. Indeed, the excellent electrochemical performance, and high coulombic efficiency, as well as the electrochemical impedance spectroscopy results indicate the highly beneficial impact of the IL-based electrolyte on the formation of a stabilized solid electrolyte interphase (SEI).
[en] ABSTRACT: Electrolyte compositions based on LiTFSI dissolved in fluorinated linear and cyclic carbonates were characterized regarding their transport and thermal properties, viscosity, solvation ability, electrochemical stability towards oxidation, as well as their ability to inhibit the aluminum current collector corrosion. As a result of the thorough investigation, different binary mixtures were prepared, which offer beneficial properties in terms of aluminum current collector protection and provide optimized transport properties. The use of LiTFSI as electrolyte salt rather than the state-of-the-art lithium salt, LiPF_6, enables substantial improvements with respect to safety, while maintaining high performance liquid electrolyte