Recent progress on confinement of polysulfides through physical andchemical methods

With high theoretical energy density and the natural abundance of S, lithium-sulfur （Li-S） batteries areconsidered to be the promising next generation high-energy rechargeable energy storage devices. How-ever, issues including electronical insulation of S, the lithium polysulfides （LiPSs） dissolution and the shortcycle lifespan have prevented Li-S batteries from being practical applied. Feasible settlements of confiningLiPSs to reduce the loss of active substances and improve the cycle stability include wrapping sulfur withcompact layers, designing matrix with porous or hollow structures, adding adsorbents owning stronginteraction with sulfur and inserting polysulfide barriers between cathodes and separators. This reviewcategorizes them into physical and chemical confinements according to the influencing mechanism. Withfurther discussion of their merits and flaws, synergy of the physical and chemical confinement is believedto be the feasible avenue that can guide Li-S batteries to the practical application.

Raising the capacity of lithium vanadium phosphate via anion and cation co-substitution

The pursuit for batteries with high specific energy provokes the research of high-voltage/capacity cathode materials with superior stability and safety as the alternative for lithium iron phosphate.Herein,using the sol-gel method,a lithium vanadium phosphate with higher average discharge voltage(3.8 V,vs.Li+/Li) was obtained from a single source for Mg2+ and Cl-co-substitution and uniform carbon coating,and a nearly theoretical capacity(130.1 mA h g^-1) and outstanding rate performance(25 C) are acquired together with splendid capacity retention(80%) after 650 cycles.This work reveals that the well-sized anion and cation substitution and uniform carbon coating are of both importance to accelerate kinetic performance in the context of nearly undisturbed crystal structure for other analogue materials.It is anticipated that the electrochemistry comprehension will shed light on preparing cathode materials with high energy density in the future.

Tribocorrosion behavior of antibacterial Ti-Cu sintered alloys in simulated biological environments

Ti-Cu alloys have strong antibacterial proper-ties,high strength and excellent corrosion resistance,which might be used in orthopedic and dental implants.In this paper,the tribocorrosion behaviors of Ti-Cu alloy with different Cu contents were investigated in four simulated biological environments compared with cp-Ti.The results showed that Ti-Cu sintered alloy exhibited higher corro-sion resistance,lower coefficient friction and wear loss than cp-Ti in all tested solutions due to the formation of fine and homogeneously distributed Ti_(2)Cu phase,espe-cially in solution with lower F ion and pH.High Cu content and extrusion process improved the corrosion resistance and the wear resistance because of high Ti_(2)Cu phase fraction and fine grain size.However,aggressive solution,such as the solution with lower F ion and pH,accelerated wear in comparison with other solutions for cp-Ti and Ti-Cu sintered alloys.Scanning electron microscope(SEM)surface morphology demonstrated that the wear mecha-nism of cp-Ti during tribocorrosion process was mainly abrasive wear and adhesive wear while that of Ti-Cu alloy was abrasive wear.In summary,Ti-Cu sintered alloys showed much better tribocorrosion property than cp-Ti,which shows great potential application in condition for wear and corrosion resistance.