solid electrolyte interphase. On the other hand, increasing the surface area shortens the length of Li-ion diffusion pathways and decreases the Ohmic drop within the material. The mechanism and properties of Li-ion (de-)intercalation for TiO 2 was shown to be dependent on the particle size for some materials. [ 7,8 ] It was proposed that both Li-rich and Li-poor phases cannot co-exist within one TiO 2 particle for particle sizes below a certain value, [ 7 ] which could infl uence the potential memory effect. These facts suggest the question: If the memory effect could be one of those particle size dependent properties?Here, we reveal the presence of a memory effect in anatase TiO 2 , showing that other active materials, beside LiFePO 4 , may suffer from a memory effect in LIBs. We also demonstrate that the memory effect in anatase TiO 2 is dependent on the specifi c surface area. Namely, increasing the surface area of the TiO 2 material leads to a decrease in the memory effect, which is practically disappearing for the particles with a very high specifi c surface area (300 m 2 g −1 ).We prepared seven samples of anatase TiO 2 with different specifi c surface areas (referred to as TiO 2 _ X , where X is the specifi c surface area of 10, 60, 95, 130, 180, 240, and 300 m 2 g −1 ). The values of the specifi c surface area were obtained by the Brunauer-Emmett-Teller method and the anatase phase was confi rmed for all samples by X-ray diffraction (Supporting Information Figure S1). For the evaluation of the memory effect in these samples, we followed the electrochemical procedure as suggested by Sasaki et al., [ 5 ] which consists of applying three subsequent cycles: a normal (de-)intercalation cycle, a memory writing cycle and a memory releasing cycle ( Figure 1 a). During the memory writing cycle, the oxidation process was interrupted at a certain SOC. In the next memory releasing step the sample was cycled within the normal potential range, i.e., 3 V to 1 V in our case, and the memory effect was revealed if occurred. For all examined materials, the memory effect was observed in the memory releasing cycle. It appeared as a bump in the plateau on Li-ion de-intercalation occurring at a similar SOC at which the memory writing cycle was stopped (Figure 1 b,c) similarly as in case of LiFePO 4 . [ 5 ] Here, we defi ne the magnitude of the memory effect as a difference (in mV) between the potential of the maximum of the memory effect bump and the potential at that SOC during the normal cycle (Figure 1 a). Figure 1 presents the data for TiO 2 _95 cycled at C/3 rate, but similar behavior was observed for each examined sample (Supporting Information Figure S2a-f).It is known that the two phases do not coexist within one particle during the phase transformation for some of the materials with very small particles. [ 7 ] Instead, they "switch" spontaneously from one phase to another when the critical Li-ions content is reached and this transformation takes place at once within the entire particle. The phase transformation results...

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The high (de)lithiation potential of TiO (ca. 1.7 V vs Li/Li in 1 M Li) decreases the voltage and, thus, the energy density of a corresponding Li-ion battery. On the other hand, it offers several advantages such as the (de)lithiation potential far from lithium deposition or absence of a solid electrolyte interphase (SEI). The latter is currently under controversial debate as several studies reported the presence of a SEI when operating TiO electrodes at potentials above 1.0 V vs Li/Li. We investigate the formation of a SEI at anatase TiO electrodes by means of X-ray photoemission spectroscopy (XPS) and scanning electrochemical microscopy (SECM). The investigations were performed in different potential ranges, namely, during storage (without external polarization), between 3.0-2.0 V and 3.0-1.0 V vs Li/Li, respectively. No SEI is formed when a completely dried and residues-free TiO electrode is cycled between 3.0 and 2.0 V vs Li/Li. A SEI is detected by XPS in the case of samples stored for 6 weeks or cycled between 3.0 and 1.0 V vs Li/Li. With use of SECM, it is verified that this SEI does not possess the electrically insulating character as expected for a "classic" SEI. Therefore, we propose the term apparent SEI for TiO electrodes to differentiate it from the protecting and effective SEI formed at graphite electrodes.

Combretastatins are stilbene-based, tubulin depolymerization agents with selective activity against the tumor vasculature; two variants (A-1 and A-4) are currently undergoing clinical trials. Combretastatin A-1 (CA1) has a greater antitumor effect than combretastatin A-4 (CA4). We hypothesized that this reflects the enhanced reactivity conferred by the second (ortho) phenolic moiety in CA1. Oxidation of CA1 by peroxidase, tyrosinase, or Fe(III) generates a species with mass characteristics of the corresponding ortho-quinone Q1. After administration of CA1-bis(phosphate) to mice, the hydroquinone-thioether conjugate Q1H2-SG, formed from the nucleophilic addition of GSH to Q1, was detected in liver. In competition, electrocyclic ring closure of Q1, over a few minutes at pH 7.4, leads to a second ortho-quinone product Q2, characterized by exact mass and NMR. This product was also generated by human promyelocytic leukemia (HL-60) cells in vitro, provided that superoxide dismutase was added. Q2 is highly reactive toward glutathione (GSH) and ascorbate, stimulating oxygen consumption in a catalytic manner. Free radical intermediates formed during autoxidation of CA1 were characterized by EPR, and the effects of GSH and ascorbate on the signals were studied. Pulse radiolysis was used to initiate selective one-electron oxidation or reduction and provided further evidence, from the differing absorption spectra of the radicals formed on oxidation of CA1 or reduction of Q2, that two different quinones were formed on oxidation of CA1. The results demonstrate fundamental differences between the pharmacological properties of CA1 and CA4 that provide two possible explanations for their differential activities in vivo: oxidative activation to a quinone intermediate likely to bind to protein thiols and possibly to nucleic acids and stimulation of oxidative stress by enhancing superoxide/hydrogen peroxide production. The observation of the GSH conjugate Q1H2-SG in vivo provides a new marker for oxidative metabolism of relevance to current clinical trials of CA1-bis(phosphate) (OXi4503).