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Abstract: We investigate the point defect chemistry of lithium storage in TiO2 and emphasize its great importance to lithium battery applications. Not only charge carrier concentration but also lithium diffusivity is successfully interpreted in terms of lithium content and activity as well as oxygen stoichiometry. A detailed defect chemical analysis reveals that ionic-electronic defect associations (Li i • + e′⇌ Li i X and V O •• +2e′⇌ V O • + e′⇌ V O X ) play a significant role in determining the concentration of defects and lithium diffusivity, and hence can have large impact on overall lithium storage performance of oxide based electrode materials. [Copyright &y& Elsevier]

We present the thermodynamic modeling and experimental evidence of the occurrence of lithium storage at abrupt junctions, which describes the transition from an electrostatic capacitor to a chemical capacitor. In both Ru:Li2O and Ni:LiF systems, the functionalities and extracted parameters are in good agreement with the thermodynamic model, based on the dependence of the storage capacity on open-circuit voltage. Moreover, it is set out that a complete understanding of a conventional storage mechanism requires unifying both the space charge and bulk storage for a nanocrystalline electroactive electrode. [ABSTRACT FROM AUTHOR]

Insulator–metal transitions are well known in transition-metal oxides, but inducing an insulator–metal transition in the oxide of a main group element is a major challenge. Here, we report the observation of an insulator–metal transition, with a conductivity jump of seven orders of magnitude, in highly non-stoichiometric, amorphous gallium oxide of approximate composition GaO1.2 at a temperature around 670 K. We demonstrate through experimental studies and density-functional-theory calculations that the conductivity jump takes place at a critical gallium concentration and is induced by crystallization of stoichiometric Ga2O3 within the metastable oxide matrix—in chemical terms by a disproportionation. This novel mechanism—an insulator–metal transition driven by a heterogeneous solid-state reaction—opens up a new route to achieve metallic behaviour in oxides that are expected to exist only as classic insulators. [ABSTRACT FROM AUTHOR]

We report measurements of the dynamics of isolated 8Li+ in single crystal rutile TiO2 using β-detected nuclear magnetic resonance. From spin-lattice relaxation and motional narrowing, we find two sets of thermally activated dynamics: one below 100 K and one at higher temperatures. At low temperature, the activation barrier is 26.8(6) meV with prefactor 1.23(5) × 1010 s-1. We suggest this is unrelated to Li+ motion and rather is a consequence of electron polarons in the vicinity of the implanted 8Li+ that are known to become mobile in this temperature range. Above 100 K, Li+ undergoes long-range diffusion as an isolated uncomplexed cation, characterized by an activation energy and prefactor of 0.32(2) eV and 1.0(5) × 1016 s-1, respectively, in agreement with macroscopic diffusion measurements. These results in the dilute limit from a microscopic probe indicate that Li+ concentration does not limit the diffusivity even up to high concentrations but that some key ingredient is missing in the calculations of the migration barrier. The anomalous prefactors provide further insight into both Li+ and polaron motion. [ABSTRACT FROM AUTHOR]

LiFePO4cathode material obtained via solvothermal synthesiswas investigated at several charging and discharging stages by a combinationof bulk (EELS) and surface sensitive (NEXAFS) methods in order toget insight into the distribution of Li in the surface and bulk regionof the particles. Different behavior was observed as a function ofthe particles morphology. The turbostratic stacking of layers in nanosizedcrystals induces higher dimensional defects responsible for sluggishLi insertion and extraction within the structure. In contrast, microstructuredcrystals without higher dimensional defects do not exhibit sluggishLi insertion/extraction, and achieve a higher degree of reversibilityduring electrochemical cycling. [ABSTRACT FROM AUTHOR]