The diffusion property of the intercalated species in the graphite materials is at the heart of the rate performance of graphite-based metal-ion secondary battery.Here we study the diffusion process of a AlCl_(4) mole...The diffusion property of the intercalated species in the graphite materials is at the heart of the rate performance of graphite-based metal-ion secondary battery.Here we study the diffusion process of a AlCl_(4) molecule within graphite—a key component of a recently reported aluminum ion battery with excellent performance—via molecular dynamics(MD)simulations.Both ab-initio MD(AIMD)and semiempirical tight-binding MD simulations show that the diffusion process of the intercalated AlCl_(4) molecule becomes rather inhomogeneous,when the simulation time exceeds approximately 100 picoseconds.Specifically,during its migration in between graphene layers,the intercalated AlCl_(4) molecule may become stagnant occasionally,and then recovers its normal(fast)diffusion behavior after halting for a while.When this phenomenon occurs,the linear relationship of the mean squared displacement(MSD)versus the duration time is not fulfilled.We interpret this peculiar behavior as a manifestation of inadequate sampling of rare event(the stagnation of the molecule),which does not yet appear in short-time MD simulations.We further check the influence of strains present in graphite intercalated compounds(GIC)on the diffusion properties of AlCl_(4),and find that their presence in general slows down the diffusion of the intercalated molecule,and is detrimental to the rate performance of the GIC-based battery.展开更多
基金supported by the National Key Research and Development Program of China(Grant No.2016YFB0201202)the National Natural Science Foundation of China(Grant Nos.11874335 and 11774327)。
文摘The diffusion property of the intercalated species in the graphite materials is at the heart of the rate performance of graphite-based metal-ion secondary battery.Here we study the diffusion process of a AlCl_(4) molecule within graphite—a key component of a recently reported aluminum ion battery with excellent performance—via molecular dynamics(MD)simulations.Both ab-initio MD(AIMD)and semiempirical tight-binding MD simulations show that the diffusion process of the intercalated AlCl_(4) molecule becomes rather inhomogeneous,when the simulation time exceeds approximately 100 picoseconds.Specifically,during its migration in between graphene layers,the intercalated AlCl_(4) molecule may become stagnant occasionally,and then recovers its normal(fast)diffusion behavior after halting for a while.When this phenomenon occurs,the linear relationship of the mean squared displacement(MSD)versus the duration time is not fulfilled.We interpret this peculiar behavior as a manifestation of inadequate sampling of rare event(the stagnation of the molecule),which does not yet appear in short-time MD simulations.We further check the influence of strains present in graphite intercalated compounds(GIC)on the diffusion properties of AlCl_(4),and find that their presence in general slows down the diffusion of the intercalated molecule,and is detrimental to the rate performance of the GIC-based battery.
