Search

In this paper, powder metallurgy (PM) H13 steels were investigated based on the characterisation of water atomised H13 powders. Vacuum sintering was carried out from 1150 to 1265°C for sintering de...

LiAl5O8-coated Li1.2Mn0.54Ni0.13Co0.13O2 cathode materials were synthesized by using the co-precipitation method along with a facile sol-gel coating process. Homogeneous and 3–5 nm thin LiAl5O8 film was formed on the LMNC surface. After the coating modification, discharge specific capacity, the initial Coulombic efficiency, and rate performance were improved to some extent. It was particularly important to note that the voltage decay of the battery after the charge and discharge cycle was well suppressed. Specifically, the 3 wt% LiAl5O8-coated electrode can deliver the initial discharge capacity of 243.5 mAh g−1 with a low irreversible capacity loss of 51.1 mAh g−1 and the initial Coulombic efficiency reached the maximum of 82.63% at 0.1 C rate. Although the 1 wt% LiAl5O8-coated electrode was cycled through 100 cycles at a rate of 0.5 C, the capacity retention rate was still up to 95.8%, while that of the LiAl5O8-free one was only 82.8%. The stable and thin LiAl5O8 coating layer protected the electrode structure from HF corrosion and other side reactions and reduced the oxygen loss (in the form of Li2O) by suppressing the initial activation of Li2MnO3.

In this study, the effects of Dy2O3/WS2 co-doping on magnetic properties and microstructure of Nd-Fe-B–sintered magnets were investigated. With WS2 addition, microstructure regulation and coercivity improvement were achieved in the Dy-containing magnets. The optimal magnetic performance was obtained in the 2 wt% Dy2O3/0.4 wt% WS2 co-doped magnets. The coercivity, remanence, and maximum energy product were 1727.1 kA/m, 1.211 T, and 286.5 kJ/m3, respectively. The coercivity was 10.5% higher than the WS2-free magnets, while there was no obvious change in the remanence and the maximum energy product. Relatively clear grain boundary phases were observed with smaller grain size. The average grain size of the co-doped magnets was 6.4 μm, which was about 1.6 μm smaller than the WS2-free magnets. More uniform Dy distribution was also obtained with the Nd2O2S phase formation. Besides, the W element likely precipitated at the grain boundaries.

The inorganic solid electrolytes Li6.25-xAl0.25La3Zr2-xTaxO12 (LALZT) with various Ta contents (x) are synthesized using conventional solid-state reaction method at 1200 ​°C for different holding times. The effect of holding time and Al/Ta co-doping on the crystal structure, microstructure and ionic conductivity of the LALZT solid electrolytes is discussed. The LALZT powder with a fine particle size and narrow particle distribution is prepared by the high-energy ball milling. Suitable Al/Ta doping stabilizes the cubic phase and enhances the ionic conductivity of the LALZT. The short holding time is 6 ​h due to the equal ionic conductivity for the LALZT samples sintered for 6 ​h or 10 ​h by the solid-state reaction method. The highest ionic conductivity can be obtained for the optimized composition of Li5.85Al0.25La3Zr1.6Ta0.4O12. The excellent ionic conductivity indicates that Al/Ta co-doped LALZT could be a promising electrolyte candidate for all-solid-state Li-ion batteries in practical application.

The electrochemical properties and microstructure of Li-rich cathode materials Li1.2Mn0.54Co0.13Ni0.13O2 synthesized in one-step were studied. The sample (s-g) was composed of single crystal particles (1–2 μm) with regular and smooth surface, and the particle size distribution was concentrated. Compared with the sample (cop) prepared by traditional coprecipitation method, the discharge specific capacity of sample s-g increased from 79.9 mAh g−1 to 114.5 mAh g−1 at 10C. After 100 cycles at the rate of 0.1C and 0.2C, the capacity retention rates of sample s-g were 99.48% and 105.36%, while those of sample cop were 66.23% and 71.55%, respectively. Homogeneous single crystal structure and good grain size control greatly released the capacity potential of Li-rich cathode materials and solved the problem of poor rate performance and fast capacity decay.

In this study, the relationship between Dy2O3 and MoS2 on magnetic performance and microstructure in Nd-Fe-B sintered magnets was investigated. Compared with the Dy2O3 doped magnets, the coercivity of the Dy2O3/MoS2 co-doped magnets increased with the increasing of MoS2 content. A comprehensive magnetic performance was achieved in the 2 wt% Dy2O3/0.5 wt% MoS2 co-doped magnets. The coercivity increased from 1563.2 kA/m to 1710 kA/m while there was no obvious decrease in the remanence and maximum energy product. Furthermore, the average grain size decreased from 8 μm to 6.7 μm. In the co-doped magnets, the distribution of Dy element was relatively uniform because Dy atoms were found to avoid the Nd2O2S phase. Besides, the Mo atoms were likely diffused into the Nd2Fe14B phase instead of the Nd-rich phase.