wileyonlinelibrary.comcathode materials with well-ordered structures where most of doping metal atoms exist in the transition-metal sublattice. However, the conventional layered oxide cathode after modifi cation can only deliver a practical capacity of less than 200 mAh g −1 .In recent years, lithium-rich layered oxides based on Li 2 MO 3 (M = Mn, Ru etc.) with layered structure are considered as promising cathodes for Li-ion batteries due to their higher capacity of more than 220 mAh g −1 and higher stability at high voltage as compared with the conventional LiMO 2 layered oxides, provoking worldwide attentions. [8][9][10][11][12][13][14] The common feature accounting for the high capacities of these lithium-rich layered oxides is the two redox processes involving both of cation and anion. [ 10,13,15,16 ] Despite the same process of partly charge compensation by oxygen during deep charging/discharging process, the lithiumrich layered oxides can deliver much higher reversible capacity than that of conventional cathode materials. To the best of our knowledge, such difference on the structural stability between the conventional and lithium-rich layered oxides has attracted limited attention. It is of high importance that there must be some unknown mechanism leading to the stability difference since the geometric and electronic structure between these two kinds of layered materials are similar, except for the superlattice structure. In present work, we elucidate why lithium-rich layered oxides Li 2 RuO 3 exhibit high capacities without undergoing a structural collapse for a certain number of cycles by tracking the electronic and geometric structural changes induced in Li 2 RuO 3 during charging/discharging. Backed up with the density functional theory (DFT) calculations and a series of in situ experiments, we unravel that the presence of the lithium atoms in the transition metal layer could make the lithium-rich structure fl exible, facilitating the formation of O 2 2− -like species, which favors the structural integrity and providing high capacity. Results and DiscussionWe chose Li 2 RuO 3 as the model lithium-rich compound because it contains a single metal, making it convenient to track the electronic and geometric structural changes during charging/discharging process without interference. In addition,

High energy density Li-S batteries are highly attractive. However, their use in practical applications has been greatly affected by their poor cycle life and low rate performance, which can be partly attributed to the dissolution of polysulfides from the S cathode and their migration to the Li anode through the separator. While much effort has been devoted to designing the structure of the S cathodes for suppressing the dissolution of polysulfides, relatively little emphasis has been placed on modifying the separator. Herein, we demonstrate a new approach for modifying the separator with a polyvinylidene fluoride-carbon (PVDF-C) layer, where the polysulfides generated in the Li-S cells can be localized on the cathode side. Li-S batteries based on the novel separator and a cathode prepared by the simple mixing of a S powder and super P have delivered discharge capacities of 918.6 mAh g(-1), 827.2 mAh g(-1), and 669.1 mAh g(-1) after 100, 200, and 500 cycles, respectively, at a discharge rate of 0.5 C. Even under current densities of up to 5 C, the cells were able to retain a discharge capacity of 393 mAh g(-1), thereby demonstrating an excellent high rate performance and stability. The exceptional electrochemical performance could be attributed to the intense adsorption capability of the micropores, presence of C-C double bonds, and conductivity of the C network in the PVDF-C layer. This economical and simple strategy to overcome the polysulfide dissolution issues provides a commercially feasible method for the construction of Li-S batteries.

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A heated oxide covered copper electrode (HOCE) was facilely fabricated for the first time, providing a highly enhanced electrocatalytic oxidation, and cost effective and sensitive determination for polyhydroxy compounds such as glucose and shikimic acid.