The structural, electronic, and adsorption properties of Li/Na ions on graphene decorated by epoxy groups are investigated by first-principles calculations based on density functional theory.Our results show that the ...The structural, electronic, and adsorption properties of Li/Na ions on graphene decorated by epoxy groups are investigated by first-principles calculations based on density functional theory.Our results show that the concentration of epoxy groups remarkably affects the structural and electronic properties of graphene.The bandgaps change monotonically from0.16 eV to 3.35 eV when the O coverage increases from 12.5% to 50%(O/C ratio).Furthermore, the highest lithiation potential of 2.714 V is obtained for the case of graphene oxide(GO) with 37.5 % O coverage, while the highest sodiation potential is 1.503 V for GO with 12.5% O coverage.This clearly demonstrates that the concentration of epoxy groups has different effects on Li and Na storage in GO.Our results provide a new insight into enhancing the Li and Na storage by tuning the concentration of epoxy groups on GO.展开更多
Understanding the mechanism of the interfacial reaction between the cathode material and the electrolyte is a significant work because the interfacial reaction is an important factor affecting the stability,capacity,a...Understanding the mechanism of the interfacial reaction between the cathode material and the electrolyte is a significant work because the interfacial reaction is an important factor affecting the stability,capacity,and cycling performance of Li-ion batteries.In this work,spin-polarized density functional theory calculations with on-site Coulomb energy have been employed to study the adsorption of electrolyte components propylene carbonate(PC)on the LiMn2O4(100)surface.The findings show that the PC molecule prefers to interact with the Mn atom on the LiMn2O4(100)surface via the carbonyl oxygen(Oc),with the adsorption energy of−1.16 eV,which is an exothermic reaction.As the adsorption of organic molecule PC increases the Mn atoms coordination with O atoms on the(100)surface,the Mn3+ions on the surface lose charge and the reactivity is substantially decreased,which improves the stability of the surface and benefits the cycling performance.展开更多
The spinel-type LiMn_(2)O_(4) is a promising candidate as cathode material for rechargeable Li-ion batteries due to its good thermal stability and safety.Experimentally,it is observed that in this compound there occur...The spinel-type LiMn_(2)O_(4) is a promising candidate as cathode material for rechargeable Li-ion batteries due to its good thermal stability and safety.Experimentally,it is observed that in this compound there occur the structural phase transitions from cubic(Fd3m)to tetragonal(I4_(1)/amd)phase at slightly below room temperature.To understand the phase transition mechanism,we compare the Gibbs free energy between cubic phase and tetragonal phase by including the configurational entropy.Our results show that the configurational entropy contributes substantially to the stability of the cubic phase at room temperature due to the disordered Mn^(3+)/Mn^(4+)distribution as well as the orientation of the Jahn-Teller elongation of the Mn^(3+)O_(6) octahedron in the the spinel phase.Meanwhile,the phase transition temperature is predicted to be 267.8 K,which is comparable to the experimentally observed temperature.These results serve as a good complement to the experimental study,and are beneficial to the improving of the electrochemical performance of LiMn_(2)O_(4) cathode.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.11764019)the Education Department of Jiangxi Province,China(Grant No.GJJ170186)Science Foundation for PHDs of Jiangxi Normal University,China(Grant No.7957)
文摘The structural, electronic, and adsorption properties of Li/Na ions on graphene decorated by epoxy groups are investigated by first-principles calculations based on density functional theory.Our results show that the concentration of epoxy groups remarkably affects the structural and electronic properties of graphene.The bandgaps change monotonically from0.16 eV to 3.35 eV when the O coverage increases from 12.5% to 50%(O/C ratio).Furthermore, the highest lithiation potential of 2.714 V is obtained for the case of graphene oxide(GO) with 37.5 % O coverage, while the highest sodiation potential is 1.503 V for GO with 12.5% O coverage.This clearly demonstrates that the concentration of epoxy groups has different effects on Li and Na storage in GO.Our results provide a new insight into enhancing the Li and Na storage by tuning the concentration of epoxy groups on GO.
基金Project supported by the National Natural Science Foundation of China(Grant No.51962010).
文摘Understanding the mechanism of the interfacial reaction between the cathode material and the electrolyte is a significant work because the interfacial reaction is an important factor affecting the stability,capacity,and cycling performance of Li-ion batteries.In this work,spin-polarized density functional theory calculations with on-site Coulomb energy have been employed to study the adsorption of electrolyte components propylene carbonate(PC)on the LiMn2O4(100)surface.The findings show that the PC molecule prefers to interact with the Mn atom on the LiMn2O4(100)surface via the carbonyl oxygen(Oc),with the adsorption energy of−1.16 eV,which is an exothermic reaction.As the adsorption of organic molecule PC increases the Mn atoms coordination with O atoms on the(100)surface,the Mn3+ions on the surface lose charge and the reactivity is substantially decreased,which improves the stability of the surface and benefits the cycling performance.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12174162,51962010,12064015,and 12064014).
文摘The spinel-type LiMn_(2)O_(4) is a promising candidate as cathode material for rechargeable Li-ion batteries due to its good thermal stability and safety.Experimentally,it is observed that in this compound there occur the structural phase transitions from cubic(Fd3m)to tetragonal(I4_(1)/amd)phase at slightly below room temperature.To understand the phase transition mechanism,we compare the Gibbs free energy between cubic phase and tetragonal phase by including the configurational entropy.Our results show that the configurational entropy contributes substantially to the stability of the cubic phase at room temperature due to the disordered Mn^(3+)/Mn^(4+)distribution as well as the orientation of the Jahn-Teller elongation of the Mn^(3+)O_(6) octahedron in the the spinel phase.Meanwhile,the phase transition temperature is predicted to be 267.8 K,which is comparable to the experimentally observed temperature.These results serve as a good complement to the experimental study,and are beneficial to the improving of the electrochemical performance of LiMn_(2)O_(4) cathode.
