Because of the outstanding discharge capacity provided by oxygen redox activity, Li-rich layered oxide positive electrode materials for Li-ion batteries attract tremendous attention. However, there is still no full consensus on the role that the ionocovalency of transition metal (TM)−oxygen (O) chemical bonding plays in the reversibility of the oxygen redox as well as on both local crystal and electronic structure transformations. Here, we managed to tune the cationic/anionic redox contributions to the overall electrochemical activity using the xLi 2 RuO 3 -(1 − x)Li 1.2 Ni 0.2 Mn 0.6 O 2 solid solutions as a model system possessing the same crystal structure and morphology as Li-rich layered oxides. We conclusively traced the whole cascade of events from increasing the covalency of the TM−O bond, suppressing irreversible oxygen oxidation to the generation of the reduced Mn species toward retarding the structure "densification" in the Li-rich layered oxides. The results demonstrate that enhancing the degree of covalency of the TM−O bonding is vitally important for anchoring the reversibility of the charge compensation mechanism occurring through partial oxygen oxidation.

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Nickel-rich layered transition metal oxides (LiNixMnyCo1-x-yO2 (x ≥ 0.6), Ni-rich NMCs) have been under intense investigation as high-energy density and low-cost positive electrode materials for Li-ion batteries. However, insufficient cyclic...

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We have studied the space-selective microcrystallization of barium titanium silicate glass under the femtosecond laser beam. The glass composition (mol %) was 40BaO•20TiO 2 •40SiO 2 corresponding to the composition of polar fresnoite phase known for its large second-order optical susceptibility. Optical and micro-Raman microscopy confirmed the laser-induced formation of the Ba 2 TiSi 2 O 8 crystalline tracks and their morphology was investigated by transmission electron microscopy. The possibility of a 20-fold increase in laser scanning speed providing homogeneous crystal track growth using the laser beam with an elliptical cross-section as compared to the conventional Gaussian beam has been shown. It has been demonstrated for the first time that annealing of laser-written crystalline tracks leads to substantial improvement of the quality of tracks structure tending to that of the fresnoite single crystal, which can be an important step in the development of single crystal optical waveguide components for photonics.