Although Ni-rich layered oxides are considered a candidate of next-generation cathode materials, their inherent properties, such as surface lithium residues and structural destruction, cause detrimental electrochemical performance, especially at elevated temperatures. Here, a facile ball-milling method is proposed to remove the lithium residues and enhance the electrochemical performance of LiNi0.6Co0.2Mn0.2O2. After NH4VO3 treatment, a lithium ion-conductive Li3VO4 coating layer is found on the LiNi0.6Co0.2Mn0.2O2 surface at heat-treatment temperatures of 300 and 450 °C, with a small part of vanadium ions diffusing into the surface lattice. When the temperature surpasses 600 °C, almost all vanadium ions dope into the bulk structure. The complex relationships between the post-sintering temperature and surface structure and their impact on electrochemical properties are discussed in detail. Electrochemical tests show that 0.5 wt% NH4VO3 treated LiNi0.6Co0.2Mn0.2O2 at 450 °C exhibits much improved cycling stability (96.1% cycling retention at 0.5C after 100 cycles and 97.2% after 50 cycles at 55 °C), rate capability (117.0 mA h g-1 at 5C), and storage property (4683 ppm lithium residue amount after storing in air for 7 days). Such superior performance is ascribed to the Li3VO4 coating layer that inhibits the electrolyte decomposition and helps create a stable and thinner cathode-electrolyte interface, resulting in decreased interfacial resistance. In addition, this coating layer suppresses internal micro-stress and phase transformation from a layered to spinel and rock-salt structure, which increases the structural integrity of LiNi0.6Co0.2Mn0.2O2 during repeated charge-discharge cycling.

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Novel double-stranded polyacetylene with a perylene bisimide bridge has been efficiently synthesized by metathesis cyclopolymerization of bis(1,6-heptadiyne) derivatives, and exhibited good solubility, highly thermal and oxidative stability, low LUMO energy levels, narrow bandgaps, and regular ladder-like architecture.

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The severe capacity fading of LiMn2O4 at elevated temperature hinders its wide application in lithium ion batteries despite several advantages over present cathode materials in terms of cost, rate capability, and environmental benignity. In this study, porous nanosized TiO2-coated LiMn2O4 is prepared via a modified sol–gel process of controlling hydrolysis and condensation of titanium tetrabutoxide in ethanol/ammonia mixtures, and the phenomenon of homogeneous nucleation has been almost entirely avoided. The X-ray diffraction patterns and transmission electron microscopy images show that a porous nanosized TiO2 layer is uniformly coated on the surface of spinel LiMn2O4. Electrochemical tests reveal that the optimal coating content is 3 wt % which shows remarkably improved capacity retentions at both room temperature of 25 °C and elevated temperature of 55 °C. Even after long-term charge and discharge cycles, the TiO2 layer is still robust enough to prevent LiMn2O4 particles from the attack of electrolyte. The inductively coupled plasma-atomic emission spectrometry, electrochemical impedance spectroscopy, and X-ray photoelectron spectroscopy results indicate that the obvious improvement of TiO2-coated LiMn2O4 electrodes is attributed to the suppression of Mn dissolution, as well as the enhancement of kinetics of Li+ diffusion.