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Dual electrolyte systems based on APC electrolyte mixed with either LiCl or LiTFSI are compared in a hybrid Mg/Li4Ti5O12 battery. Their comparison points to the detrimental effect of TFSI− anions on the battery performance through increase of polarization for Mg stripping and subsequent capacity fade. The effect is further explored through the study of Mg deposition/stripping in a dual electrolyte system and its comparison with conventional Mg electrolyte. Again, the detrimental effect of TFSI− anions is confirmed through the increase of polarization and decrease of the Coulombic efficiency, while Cl− anions have a minor beneficial effect on both. We hypothesize that the passivation of Mg metal in TFSI− anions containing electrolytes is the likely cause. Keywords: Dual electrolyte, TFSI− and Cl− anion, Hybrid Mg/Li4Ti5O12 battery, Mg deposition/stripping

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

A modified 4-electrode Swagelok cell is proposed as an in situ analytical tool for the detection of soluble polysulphides in the electrolyte during lithium sulphur battery operation. Besides the standard Swagelok configuration, this cell has two additional perpendicular electrodes (wires) placed between two separators. Soluble polysulphides in the electrolyte are reduced on the nickel wire and the cumulative charge in the potential range between 2.25 V and 1.5 V versus platinum is used for the quantitative analysis. The proposed cell can be used as an effective and a reliable in situ analytical tool which can significantly help in studying how different solvents, salts, additives and electrode architectures impact the stability of the lithium–sulphur battery, hence the set up of foundation to design better electrolytes and/or additives. Keywords: Lithium sulphur battery, Polysulphides, Reduction, Cyclovoltammetry, in situ multi-electrode cell

To enhance the high-rate capability (up to 120 C, 20 A/g) of nanoparticulate TiO2 (anatase) formed by thermal treatment of protonated TiO2 nanotubes, we used two types of additives: RuO2 as an electron-conductive material [Y.-G. Guo, Y.-S. Hu, W. Sigle, J. Maier, Adv. Mater. 19 (2007) 2087] and silica as a suppressant of particle growth during heat treatment. We show systematically that both additives, when used separately, improve the high-rate performance of anatase by 25–55 mA h/g at 60 C. The combined use of both additives in a total amount of merely 2.5 wt.% leads to an improvement of more than 70 mA h/g at 60 C. The underlying mechanisms for these significant effects are briefly discussed. Keywords: Anatase, TiO2, Rate performance, Wiring, RuO2, SiO2

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

Pure Na2Ti6O13 phase was successfully prepared from partially washed (Na,H)TiO nanotubes and used as an insertion material for lithium ions. Results show that the structure can accommodate upto 3 mol of lithium per 1 mol of Na2Ti6O13. Accommodation of 0.5 mol of lithium per one titanium atom corresponds to the partial reduction of Ti4+ to Ti3+ and occurs several 100s of millivolts lower than typically encountered for titanium in an octahedral oxygen environment such as Li4Ti5O12. Lithium insertion into this phase was evaluated using especially in situ X-ray. Lithium insertion into Na2Ti6O13 phase includes three domains corresponding to two solid–solutions and a biphasic transition in the potential range between 1.5 V and 1.0 V vs. lithium. The process is very reversible so that after re-oxidation the structure is completely preserved. Capacity fading observed during the cycling is explained by parasitic reactions attributed to a catalytic effect of the exposed bare surface on the electrolyte degradation. Keywords: Na2Ti6O13, Titanium oxide, Anode, Lithium insertion, Li-ion batteries

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