Short summary in slides of the paper Antisite disorder and bond valence compensation in Li2FePO4F cathode for Li-ion batteries

1. Í Î ÂÛ ÅÍ ÈÇØÈÅÑÌ ÅØÀÍ Í Û ÅÁËÎ ×Í Û Å
ÕÀËÜÊÎ ÃÅÍ ÈÄÛ Í ÈÊÅËß
Московский Государственный Университет
им. М.В. Ломоносова
Факультет Наук о Материалах
Исаева А.А.
Научные руководители
д.х.н., проф. Б.А. Поповкин
к.х.н., асс. ФНМ А.И. Баранов
КАФЕДРА НЕОРГАНИЧЕСКОЙ ХИМИИ
Лаборатория Направленного Неорганического
Синтеза
Ë Î Ì Î Í Î ÑÎ Â -2 0 0 3
Short summary of the paper
"Antisite Disorder and Bond
Valence Compensation in
Li2FePO4F Cathode for Li-Ion
Batteries"
O. Karakulina et al., Chem. Mater. 2016, 28
(21), 7578–7581.

2. 2
Reason for the publication
There must be something specific in the structure
of Li2FePO4F that leads to antisite disorder upon
electrochemical charging
We observe massive antisite
disorder occuring for Li2FePO4F
after a mere 10 charge-discharge
cycles.
Similarly cycled LiFePO4
Pristine NaLiFePO4F
Chemically charged Li2FePO4F
do not show such antisite
disorder.
Contrary
to

3. 3
Why is migration of the transition metal
important in metal ion batteries?
transition metal cations
can block Li-diffusion
pathways
can induce irreversible
phase transitions
x
For example blocking diffusion through
tetrahedral interstices in edge sharing LiO6
octahedra in LiFePO4 [as in detail in Hu & Tao,
JMCA 40 (2015)]
For example in LiRhO2, where
structure transforms from a
layered structure to a tunnel
structure. [D. Mikhailova et al.,
Inorg. Chem. 2016, 55 (14),
7079–7089]

4. 4
After 10 cycles, we refined the occupancies
using electron diffraction tomography
we took electron diffraction patterns with a difference of 1°
we reconstructed the reciprocal lattice
we refined the structure and occupancies using JANA2006

5. 5
And found...
-the Fe positions contain
30 and 40 % Li
-the Li2 position contains
36% Fe
-Li1 and Li3 contain
10-12% Fe

6. 6
Li2FePO4F
In LiFePO4
Reason for the tendency towards antisite defects in
Li2FePO4F only:
1) "dangling bonds" in
Li2FePO4F: the O3 and O5
oxygens are connected to two
active lithium  charging
removes the active Li1 and O3
and O5 remain severly
underbonded there are no oxygen
that are under-
bonded upon
removal of the
active lithium (i.e.
upon charging)
replacing some Li by Fe
compensates the
underbonding

7. 7
Li2FePO4F
Reason for the tendency towards antisite defects in
Li2FePO4F only:
2) edge sharing FeO4F2
octahedra cause overbonding
of O2 and O6
replacing some Fe by Li
compensates the
overbonding
there are only
corner sharing
octahedra,
thus no
overbonding
In LiFePO4

8. 8
Li2FePO4F
This is why upon cycling there is an large amount of
antisite defects in Li2FePO4F but not in LiFePO4.
LiFePO4

9. 9
All details can be found in the paper
"Antisite Disorder and Bond Valence
Compensation in Li2FePO4F Cathode for Li-Ion
Batteries"
Karakulina, O. M.; Khasanova, N. R.; Drozhzhin, O. A.; Tsirlin, A.
A.; Hadermann, J.; Antipov, E. V.; Abakumov, A. M.
Chem. Mater. 2016, 28 (21), 7578–7581.