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The application of SiO anodes in Li-ion batteries is greatly restricted by its low initial coulombic efficiency (ICE). Usually, a pre-lithiation procedure is necessary to improve the ICE, but the available technologies are associated with safety issues. Metal (M)-mixed SiO shows great promise to address these issues by reactivating Li2 O through the reaction M+Li2 O→MOx +Li+ , which is the inverse reaction to that occurring at MOx anodes. Sn is found to be a good choice of metal for this concept. Nanoscale Sn-mixed SiO composites are prepared by mechanical milling. Sn forms an outstanding conductive phase, which boosts the reaction kinetics and also reactivates the Li2 O byproduct. Sn/SiO (1:2 w/w) delivers a significant improvement in ICE from 66.5 % to 85.5 %. A higher ICE value of >90 % is obtained when the Sn content is ≥50 wt %. However, additional electrolyte decomposition occurs, which is catalyzed by Sn. In addition, coarsening of the nano-Sn material reduces the inverse conversion reactivity of Sn/Li2 O and subsequently results in rapid capacity fading. The quantitative analysis indicates that, in contrast to transition metals, the alloying and dealloying nature of Sn gives a 50 % improvement in reversible capacity, attributed to Sn/Li2 O. This work gives a general strategy to choose metals for increasing the ICE of SiOx and metal oxides.

A stable MnOx @C@MnOx core-shell heterostructure consisting of vertical MnOx nanosheets grown evenly on the surface of the MnOx @carbon nanowires are obtained by simple liquid phase method combined with thermal treatment. The hierarchical MnOx @C@MnOx heterostructure electrode possesses a high specific capacitance of 350 F g-1 and an excellent cycle performance owing to the existence of the pore structure among the ultrasmall MnOx nanoparticles and the rapid transmission of electrons between the active material and carbon coating layer. Particularly, according to the in situ Raman spectra analysis, no characteristic peaks corresponding to MnOOH are found during charging/discharging, indicating that pseudocapacitive behavior of the MnOx electrode have no relevance to the intercalation/deintercalation of protons (H+ ) in the electrolyte. Further combining in situ X-ray powder diffraction analysis, the diffraction peak of α-MnO2 can be detected in the process of charging, while Mn3 O4 phase is found in discharge products. Therefore, these results demonstrate that the MnOx undergoes a reversible phase transformation reaction of Mn3 O4 ↔α-MnO2 . Moreover, the assembled all-solid-state asymmetric supercapacitor with a MnOx @C@MnOx electrode delivers a high energy density of 23 Wh kg-1 , an acceptable power density of 2500 W kg-1 , and an excellent cyclic stability performance of 94% after 2000 cycles, showing the potential for practical application.

A method of pulse electrodeposition was proposed to synthesize polyaniline (PANI)/MnO2 composite in aniline, H2SO4, and MnSO4 aqueous solution. The PANI/MnO2 composite has rod-like structure and MnO2 particles are distributed on PANI uniformly. To evaluate the performance of the as-prepared materials as supercapacitor electrodes, cyclic voltammetry, galvanostatic charge–discharge measurements, and electrochemical impedance spectroscopy were performed. The PANI/MnO2 composite shows a higher specific capacitance (810 F g−1) than pure PANI (662 F g−1) at a current density of 0.5 A g−1. The cycle life of the composite was also excellent. After 1,000 cycles, it maintained 86.3% of its initial capacitance. POLYM. COMPOS., 36:113–120, 2015. © 2014 Society of Plastics Engineers

The effects of forging on the diffusion of chromium (Cr) in alloy steel ingot are studied by diffusion model with finite element method (FEM) and verified by the experimental observations. Calculated results show that forging can enhance the diffusion of Cr in alloy steel ingot during the homogenization treatment, which is attributed to the geometry change and the increased diffusion coefficient caused by recrystallization. The geometry change caused by the forging is a factor to increase the diffusivity (from the high concentration region to the low one) of Cr. But, the diffusion coefficient of Cr in the deformed sample is obviously enhanced, the diffusivity is two orders of magnitude higher than that caused by geometry change. The enlarged diffusion coefficient is originated from the recrystallization, which plays a major role in enhancing the diffusion during the homogenization treatment. The experimental results are confirmed with the calculated predicts, the calculated deviation is less than 7%. It is shown that the effect of recrystallization is a new mechanism of enhancing the diffusion by forging .The theoretical explanations of the diffusion mechanism enhanced by forging are also proposed.

Carbon materials have attracted considerable attention as anodes for lithium-ion and sodium-ion batteries due to their low cost and environmental friendliness. This work reports an advanced carbon nanostructure that takes advantage of the chelation effect of glucose and metal ions, which ensures the uniform dispersion of metal in the precursor. Thus, an effective catalytic conversion from sp3 to sp2 carbon occurs, enabling simultaneously formation of pores with catalyzed graphitic structures. Due to the low carbonization temperature and short carbonization time as well as the different catalytic degree of various metals, a series of expanded graphitic layers from 0.34 to 0.44 nm with defects and amorphous carbon structure are obtained. The structure not only offers accessible graphitic spacings for reversible lithium/sodium ion insertion, but also provides abundant active sites for lithium/sodium ion adsorption in the defects and amorphous structure. Moreover, the hierarchical interconnected porous structure combining graphitic ribbons is beneficial for fast electronic/ionic transport and favorable electrolyte permeation. More importantly, such advanced carbon materials prove their feasibility for balancing the pore structure and degree of graphitization. When serving as the electrode material for lithium-ion and sodium-ion batteries, excellent electrochemical performance along with fast kinetics and long cycle life is achieved.