AM60B magnesium alloy was refined by MgCO3 and its microstmcturat evolution was investigated during partial remelting. The results indicate that MgCO3 is an effective grain refiner for AM60B alloy and can decrease the...AM60B magnesium alloy was refined by MgCO3 and its microstmcturat evolution was investigated during partial remelting. The results indicate that MgCO3 is an effective grain refiner for AM60B alloy and can decrease the grain size from 329 pm of the unrefined alloy to 69 μm. A semisolid microstructure with small and spheroidal primary particles can be obtained after being partially remelted. The microstructure evolution can be divided into four steps： the initial rapid coarsening, structure separation, spheroidization and final coarsening. Correspondingly, these four steps result from the phase transformations of β→α, α＋β→L and α→L, α→L and two reverse reactions of α→L and L→α, respectively. One spheroidal primary particle in the semisolid microstmcture usually originates one dendrite in the as-cast microstructure. The variation of primary particle size with holding time does not obey the LSW law, Dt^3-Do^3=Kt, after the semisolid system is in its solid-liquid equilibrium state. Longer heating duration makes the primary particles more globular, but it makes their size larger at the same time.展开更多
Li^(+) solvation structures have a decisive influence on the electrode/electrolyte interfacial properties and battery performances.Reduced salt concentration may result in an organic rich solid electrolyte interface(S...Li^(+) solvation structures have a decisive influence on the electrode/electrolyte interfacial properties and battery performances.Reduced salt concentration may result in an organic rich solid electrolyte interface(SEI)and catastrophic cycle stability,which makes low concentration electrolytes(LCEs)rather challenging.Solvents with low solvating power bring in new chances to LCEs due to the weak salt-solvent interactions.Herein,an LCE with only 0.25 mol L^(-1) salt is prepared with fluoroethylene carbonate(FEC)and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropylether(D_(2)).Molecular dynamics simulations and experiments prove that the low solvating power solvent FEC not only renders reduced desolvation energy to Li^(+) and improves the battery kinetics,but also promotes the formation of a LiF-rich SEI that hinders the electrolyte consumption.Li||Cu cell using the LCE shows a high coulombic efficiency of 99.20%,and LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)||Li cell also exhibits satisfying capacity retention of 89.93%in 200 cycles,which demonstrates the great potential of solvating power regulation in LCEs development.展开更多
基金Project(G2007CB613706) supported by the National Basic Research Program of China
文摘AM60B magnesium alloy was refined by MgCO3 and its microstmcturat evolution was investigated during partial remelting. The results indicate that MgCO3 is an effective grain refiner for AM60B alloy and can decrease the grain size from 329 pm of the unrefined alloy to 69 μm. A semisolid microstructure with small and spheroidal primary particles can be obtained after being partially remelted. The microstructure evolution can be divided into four steps： the initial rapid coarsening, structure separation, spheroidization and final coarsening. Correspondingly, these four steps result from the phase transformations of β→α, α＋β→L and α→L, α→L and two reverse reactions of α→L and L→α, respectively. One spheroidal primary particle in the semisolid microstmcture usually originates one dendrite in the as-cast microstructure. The variation of primary particle size with holding time does not obey the LSW law, Dt^3-Do^3=Kt, after the semisolid system is in its solid-liquid equilibrium state. Longer heating duration makes the primary particles more globular, but it makes their size larger at the same time.
基金supported by the National Key Research and Development Program of China(2019YFA0705603)the National Natural Science Foundation of China(22078341)+1 种基金the Natural Science Foundation of Hebei Province(B2020103028)financial support from York University。
文摘Li^(+) solvation structures have a decisive influence on the electrode/electrolyte interfacial properties and battery performances.Reduced salt concentration may result in an organic rich solid electrolyte interface(SEI)and catastrophic cycle stability,which makes low concentration electrolytes(LCEs)rather challenging.Solvents with low solvating power bring in new chances to LCEs due to the weak salt-solvent interactions.Herein,an LCE with only 0.25 mol L^(-1) salt is prepared with fluoroethylene carbonate(FEC)and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropylether(D_(2)).Molecular dynamics simulations and experiments prove that the low solvating power solvent FEC not only renders reduced desolvation energy to Li^(+) and improves the battery kinetics,but also promotes the formation of a LiF-rich SEI that hinders the electrolyte consumption.Li||Cu cell using the LCE shows a high coulombic efficiency of 99.20%,and LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)||Li cell also exhibits satisfying capacity retention of 89.93%in 200 cycles,which demonstrates the great potential of solvating power regulation in LCEs development.
