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Low rate performance and poor cyclic performance are vital factors undermining the practical application of Li-rich layered oxides as the cathode material for advanced Li-ion batteries. Herein, we demonstrate a significant enhancement in rate capability and cyclic performance of Li1.2 Mn0.54Ni0.13Co0.13O2 via an L-ascorbic acid-based treatment. The discharge capacity ratio at different current rates (0.5C/0.05C) increases from 70.4% to 79.9% after L-ascorbic acid-based modification. Furthermore, the remaning energy for the modified sample after the 100th cycle is 628.6 Wh Kg-1, which is 35.6% higher than the energy density of pristine sample (463.5 Wh Kg-1). The enhancement in electrochemical performance of the L-ascorbic acid treated Li1.2 Mn0.54Ni0.13Co0.13O2 is attributed to the co-contribution of chemical activation of Li2MnO3 phase, exposure of high proportion of Li-conducting-favorable faces at the particle surface, increase in specific surface area and in-situ formation of minor spinel phase under the surface. [ABSTRACT FROM AUTHOR]

In this work, the effect of an L-ascorbic acid-based treatment on the physicochemical and electrochemical properties of a Li-rich oxide has been studied. Clear corrosion cavities with spinel coating layers were observed over the majority of the particle's surface, and these have been ascribed to the Li+-H+ exchange and reduction of Mn4+ to Mn2+, which is more soluble in the L-ascorbic acid solution. Furthermore, a special region without obvious traces of etching is observed over a small part of the surface of the L-ascorbic acid-treated sample, which arises from the enrichment of Ni2+ at the rim of the particle. Compared to the pristine oxide, the modified samples exhibit significantly higher initial discharge capacity/Columbic efficiency, remarkably enhanced rate performance, and considerably retarded voltage decay. The specific energy density and energy retention after 100 cycles of usage, increases from 497.6 Wh kg-1 and 63.4% for the pristine oxide to 640.8 Wh kg-1 and 68.9% for the modified sample. This enhancement in the electrochemical performance of the modified samples can be attributed to the synchronous formation of the spinel coating layer and modification of the bulk microstructure of the Li-rich layered oxide. [ABSTRACT FROM AUTHOR]

The effects of Ca on the properties of PrBa1-xCaxCo2O5+δ (x = 0.0, 0.3, and 0.5) as a cathode material for intermediate temperature solid oxide fuel cells were studied. Higher Ca content in PrBa1-xCaxCo2O5+δ led to a gradual change in phase symmetry from A-site cation ordered double perovskite (x = 0.0) to mixed A-site cation ordered-disordered perovskite (x = 0.3) to A-site cation disordered simple perovskite (x = 0.5). It also led to a decreased oxygen content. Comparing the electrochemical performance of the samples with x = 0.0 and x = 0.5, PrBa0.7Ca0.3Co2O5+δ exhibited the best catalytic activity for the oxygen reduction reaction and maximum power density. This was ascribed to the synergistic effect of the A-site cation ordered-disordered structure, which combined the advantages of a fast oxygen diffusion rate and a relatively short oxygen diffusion distance from the oxygen reduction site to the cathode/electrolyte interface. The maximum power density, which was as high as 2.16 W cm-2, was achieved for the PrBa0.7Ca0.3Co2O5+δ-based single cell with a commercial anode-supported half cell at 800°C. PrBa0.7Ca0.3Co2O5+δ was shown to be a potential cathode material for IT-SOFCs. [ABSTRACT FROM AUTHOR]