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High-capacity anode materials are widely studied for rechargeable batteries, which have the capability of storing more Li+ ions per formula. However, they normally experience large volume expansion and suffer inferior cycling stability. Herein, we propose pea-pod structured V2O3 yolk-shell microspheres@N, S co-doped carbon fiber network as an excellent anode material for lithium ion batteries. The prepared vanadium dioxide precursor is uniformly embedded into the carbon fibers by electrospinning treatment and further converted into V2O3 yolk-shell microspheres during the calcination process. The conductive carbon fiber framework which links V2O3 microspheres enhanced the electrical conductivity and structural stability significantly. Moreover, the co-doped N and S atoms derived from polymer could produce extrinsic defects, thereby improving Li+ diffusion and electrochemical active sites. When used as anodes for lithium ion batteries, the composite exhibits a high reversible capacity (793.7 mA h g−1 after 100 cycles at 100 mA g−1), excellent rate performance and cycle stability.

Based on XRD, SEM and TEM studies of the obtained Li (Ni0.67Co0.33) O2 phase from sintering, the results show that the space group of the phase is R 3 ¯ m , which belongs to the rhombohedral lattice, and there are observed many twins with 1 1 ¯ 0 4 ¯ as twining plane in the crystal. When Li (Ni0.67Co0.33) O2 phase is forming twins with 1 1 ¯ 0 4 ¯ as twinning plane, the octahedrons in the twinning plane need not to make any adjustment. At the same time, the 1 1 ¯ 0 4 ¯ interface f is close-packed plane for Li, (Ni, Co) and O atoms, moreover, the interface energy maybe the lowest if the 1 1 ¯ 0 4 ¯ plane is used as an interface. Crystallographic analysis showed that when the twins with 1 1 ¯ 0 4 ¯ as twinning plane were formed in Li (Ni0.67Co0.33) O2 phase, orientation relationship between the two twin sub-grains can also be considered as two variants of the orientation domain.

Powder packing behavior plays an important role in determining sintering ability of powder and the resultant performance of materials. In this study, a novel powder packing theory with bimodal particle size distribution is proposed by considering the loosening effect, wall effect and wedging effect. This theory is applied in PM nickel base superalloy by using mixture of coarse particles and fine particles. Microstructures of alloy sintered by vacuum hot pressing (HP) are observed by optical microscope (OM) and electron backscatter diffraction (EBSD). The prediction result by this theory is in good agreement with the experimental results. The enhanced sintering ability of powder containing appropriate fractions of coarse particle and fine particle is ascribed to the filling of fine particles to the voids between coarse particles, which enhanced the density of sample after sintering. Tensile behavior and the fracture morphology of alloys with various particle distributions are analyzed in details, suggesting the higher reliability of the present theory.