Decreasing Li/Ni disorder has been a challenging problem for layered oxide materials, where disorder seriously restricts their electrochemical performances for lithium-ion batteries (LIBs). Element doping is a great strategy that has been widely used to stabilize the structure of the cathode material of an LIB and improve its electrochemical performance. On the basis of the results of previous studies, we hypothesized that the element of Ca, which has a lower valence state and larger radius compared to Ni, would be an ideal doping element to decrease the Li/Ni disorder of LiMO materials and enhance their electrochemical performances. A Ni-rich LiNiMnCoO cathode material was selected as the bare material, which usually shows severe Li/Ni disorder and serious capacity attenuation at a high cutoff voltage. So, a series of Ca-doped LiNiCoMnCaO (x = 0-8%) samples were synthesized by a traditional solid-state method. As hypothesized, neutron diffraction showed that Ca-doped LiNiCoMnO possessed a lower degree of Li/Ni disorder, and potentiostatic intermittent titration results showed a faster diffusion coefficient of Li compared with that of LiNiMnCoO. The Ca-doped LiNiMnCoO samples exhibited higher discharge capacities and better cycle stabilities and rate capabilities, especially under a high cutoff voltage with 4.5 V. In addition, the problems of polarization and voltage reduction of LiNiMnCoO were also alleviated by doping with Ca. More importantly, we infer that it is crucial to choose an appropriate doping element and our findings will help in the research of other layered oxide materials.

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Cobalt precursor Co(CO 3 ) 0.35 Cl 0.2 (OH) 1.1 nanowire bunches have been synthesized by a hydrothermal method and transformed into Co 3 O 4 nanowires by calcination at 500 °C for 3 h. The Co 3 O 4 nanowires were then mixed with LiOH and formed the LiCoO 2 nanowires by calcination at 750 °C . High resolution transmission electron microscopy revealed that the LiCoO 2 nanowires were composed of nanoparticles with most of the nanoparticles having exposed (010) planes. The electrochemical performance of the LiCoO 2 nanowires was thoroughly investigated by galvanostatic tests. The as-prepared LiCoO 2 nanowires exhibited excellent rate capability and satisfactory cycle stability, where the charge and discharge capacity still stabilized at 100 mA·h/g at a rate of 1000 mA/g after 100 cycles. The favorable electrochemical performance of the LiCoO 2 nanowires may result from their one-dimensional nanostructure and the exposure of (010) planes, since the (010) plane is electrochemically active for layered LiCoO 2 with the α-NaFeO 2 structure and favors fast Li + transportation.

Nanoceria has been demonstrated as a potential antioxidative nano-drug. However, its short residence time in the body, toxic solvents involved in the synthesis processes, and especially the poor water solubility hinder its potential clinical applications. In this work, water-soluble chitosan-coated nanoceria particles (CNPs) are synthesized by a facile wet chemical route. The molar weight (MW) and concentration of chitosan do not affect the particles' size and the antioxidative activity of the CNPs over a wide range, and the mechanism is explored further. The behavior of CNPs over time and with a change of pH value were also examined. The CNPs reveal excellent antioxidative activity and stability over seven months at room temperature, and importantly, chitosan widens the pH range for the stable existence of water-soluble nanoceria. As a result, including its inherent advantages of wide availability, non-toxicity, biocompatibility and biodegradability, chitosan can also present the nanoceria with good water-solubility without interfering with its antioxidative activity. In other words, chitosan can enlarge the nanoceria stability over a higher pH range. These factors show the advantages of chitosan as a coating layer, promising the further application of nanoceria in biomedical and biotechnological fields.