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Structure stability, electronic property and voltage profile of LiFe1−nNnP1−mMmO4 olivine cathode material
Ist Teil von
Rare metals, 2021-12, Vol.40 (12), p.3512-3519
Ort / Verlag
Beijing: Nonferrous Metals Society of China
Erscheinungsjahr
2021
Quelle
SpringerLink
Beschreibungen/Notizen
First-principles computational studies under density functional theory (DFT) framework were used to investigate the structural stability, conductivity and voltage profile of LiFe
1−
n
N
n
P
1−
m
M
m
O
4
(N, M = Si or S) electrode materials. It is found that the LiFeP
7/8
Si
1/8
O
4
system has the most stable structure. After doping, the band gap values of the systems decrease gradually, and LiFe
7/8
S
1/8
PO
4
system has a minimum band gap of 1.553 eV, attributed to the hybridization of the Fe-d and S-p orbital electrons. The LiFeP
7/8
S
1/8
O
4
system demonstrates the characteristic of n-type semiconductor, and other doping systems have the feature of p-type semiconductor. Charge density difference maps show that the covalent property of Si–O bond is enhanced in the LiFeP
7/8
Si
1/8
O
4
system. The average distance of Li and O atoms in the S doping systems increases from 0.21026 to 0.21486 and 0.21129 nm, respectively, indicating that doping broadens significantly the channel of Li ion de-intercalation in LiFe
7/8
S
1/8
PO
4
and LiFeP
7/8
S
1/8
O
4
. Additionally, the results of lithium intercalation potential imply that the voltages of the doping systems fall into the range of 2.23–2.86 V.
Graphic abstract