Air-Induced Degradation and Electrochemical Regeneration for the Performance of Layered Ni-Rich Cathodes.

Nickel-rich layered oxides are promising cathodes for power batteries owing to their high capacity and low cost. However, during the production, storage, and application of nickel-rich cathodes, especially in case the Ni content exceeds 70%, their surfaces almost inevitably react with ambient air to form electrochemically inert Li2CO3 and LiOH, leading to significant capacity loss and therefore imposing a significant hurdle to practical applications of nickel-rich cathodes. Here, we reveal surface structures and electrochemical properties of the exposed LiNi0.8Co0.15Al0.05O2 (NCA) cathodes and investigate systematically the impact of exposure humidity, temperature, and time on NCA cathodes. We demonstrate that introduction of a 3.0-4.5 V galvanostatic cycling operation at initial cycles can remarkably regenerate the subsequent 3.0-4.3 V battery performances of the exposed cathode. This work represents a facile method to regenerate the battery performance of surface-degraded nickel-rich cathodes, opening up an avenue in fulfilling efficient production, storage, and application of nickel-rich cathode materials.

Morphology and Mechanical Properties of Polyamide 6/Polystyrene Blends Prepared by Diffusion and Subsequent Polymerization of Styrene in Polyamide 6 Pellets.

Polyamide 6 (PA6)/polystyrene (PS) blend pellets were prepared by diffusion and subsequent polymerization of styrene in commercial PA6 pellets and processed into cuboid-shaped bars by injection molding. The average PS particle size in the bars was 240 nm, slightly higher than that in the blend pellets (120 nm), showing that only limited coalescence occurs during injection molding. The mechanical properties of PA6/PS bars were investigated by tensile, flexural, and notched impact tests. A 41% increase in notched impact strength was found without decreasing the modulus, tensile, and flexural strengths and elongation to break, when compared with those of neat PA6 bars. These good mechanical properties were attributed to the small PS particle sizes, and the good interfacial adhesion between PS particles and the PA6 matrix resulted from the occurrence of PS grafting onto PA6 during the preparation of the blend pellets and injection molding. The water sorption and water-induced dimensional changes in PA6/PS bars were significantly less than those of neat PA6 bars because of the presence of the hydrophobic PS phase. This work reveals that the PA6/PS quasi-nanoblend pellets are useful stock for plastic production.

Nickel cobalt oxide/carbon nanotubes hybrid as a high-performance electrocatalyst for metal/air battery.

High-performance, low cost catalyst for oxygen reduction reaction (ORR) remains a big challenge. Herein, nanostructured NiCo2O4/CNTs hybrid was proposed as a high-performance catalyst for metal/air battery for the first time. The well-formed NiCo2O4/CNTs hybrid was studied by steady-state linear polarization curves and galvanostatic discharge curves in comparison with CNTs-free NiCo2O4 and commercial carbon-supported Pt. Because of the synergistic effect, NiCo2O4/CNTs hybrid exhibited significant improvement of catalytic performance in comparison with NiCo2O4 or CNTs alone, even outperforming Pt/C hybrid in ORR process. In addition, the benefits of Ni incorporation were demonstrated by the improved catalytic performance of NiCo2O4/CNTs compared to Co3O4/CNTs, which should be attributed to improved electrical conductivity and new, highly efficient, active sites created by Ni cation incorporation into the spinel structure. NiCo2O4/CNTs hybrid could be used as a promising catalyst for high power metal/air battery.