for tomorrow's society. [1][2][3] For this purpose, however, the battery technology itself must become sustainable as well. A great step forward toward this highly desirable goal would be the replacement of currently utilized inorganic electrode compounds, which commonly require energy-intensive synthesis methods and relatively rare metals, by eco-efficient organic lithium storage materials, ideally using biomass as precursors. [4] While this general concept has been proposed as early as the development of the first commercial lithium-based battery, [5] it was basically the work of Armand, Poizot, Tarascon, and co-workers, [6][7][8] reporting the reversible electrochemical activity of conjugated carbonyl functionalities, which triggered a continuously rising interest in studying macromolecular and polymeric compounds as lithium, and-due to their great versatility-sodium battery electrode materials. [9][10][11] In addition to their high availability, low cost, and environmental friendliness, organic active materials offer the distinguished advantage of tailorable lithium reaction potentials and capacities by carefully designing the molecular architecture. [9][10][11][12][13] In particular, the presence of planarly delocalized π-electrons, following the incorporation of phenyl groups in the units interconnecting the electrochemically active carbonyl functions, results in improved achievable capacities and Organic active materials are currently considered to be the most promising technology for the realization of fully sustainable secondary batteries. However, the understanding of the underlying reaction mechanisms is still at its beginning. In this paper, an in-depth investigation of tetra-lithium perylene-3,4,9,10-tetracarboxylate as a lithium-ion anode model compound is presented, which can be easily synthesized from commercially available 3,4,9,10-perylene-tetracarboxylic-dianhydride. The results reveal that the lithium uptake is limited to two lithium ions per molecule along a two-phase equilibrium potential within an operational voltage range down to 0.1 V. Below the corresponding potential plateau at 1.1 V the origin of the extra capacity is solely related to the presence of large amounts of conductive carbon. Based on these findings, optimized electrode composites with increased active material ratios of up to 95 wt% and a total active material mass loading of about 12.0 mg cm −2 , that is, remarkably augmented areal capacities (≈1.2 mAh cm −2 ), using percolating carbon nanotubes as electron conductor and environment-friendly, fluorine-free aqueous binders, are developed. In addition to the more than tenfold increase in areal capacity, these optimized electrode compositions show enhanced first cycle coulombic efficiencies, thus providing a great leap forward toward their commercial exploitation.
Sulfidation of pure and metal-doped ZnO nanostructure sorbents (M 0.03 Zn 0.97 O, M = Fe, Co, Ni, Cu) was studied in order to clarify the effect of metal on the transformation kinetics at 200À350 °C. The solids were prepared by coprecipitation from metal nitrate solution followed by calcination at 400 °C. Reaction with H 2 S was studied by thermal gravimetric analysis (TGA) using a gas mixture containing 0.2 vol % H 2 S in equimolar H 2 ÀN 2 . It was found that at 350 °C the TGA sulfidation profiles of all studied samples are similar, with the interface reaction being the main rate-determining step. After lowering the temperature to 250 °C the transformation of Cu 0.03 Zn 0.97 O continues to be controlled by the interface reaction with only a slightly decreased rate. In contrast, for all other samples the diffusion resistance appears, provoking a significant drop of their transformation rates. This finding shows that during sulfidation of Cu-doped ZnO the diffusion is faster than for all other sorbents. The same effect was observed for the sample prepared by impregnation of ZnO powder and containing supported Cu species. In order to understand the origin of this effect, the sulfided sorbents were characterized by XRD and N 2 physisorption, and no correlation was found between the sulfidation rate and textural properties of formed sulfides. This result indicates that sulfur transport during sulfidation occurs by solid state rather than gas phase diffusion. Also XPS has shown that Cu 2 SÀZnS solid solution is formed during sulfidation of the Cu-doped solids. We thus suggest that diffusion enhancement in the presence of copper is brought about by sulfur vacancies created through charge compensation of Cu þ replacing Zn 2þ .
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