Anti-Perovskite Li-Battery Cathode Materials

Article abstract of DOI:10.1021/jacs.7b04444

Through single-step solid-state reactions, a series of novel bichalcogenides with the general composition (Li₂Fe)ChO (Ch = S, Se, Te) are successfully synthesized. (Li₂Fe)ChO (Ch = S, Se) possess cubic anti-perovskite crystal structures, where Fe and Li are completely disordered on a common crystallographic site (3c). According to Goldschmidt calculations, Li⁺ and Fe²⁺ are too small for their common atomic position and exhibit large thermal displacements in the crystal structure models, implying high cation mobility. Both compounds (Li₂Fe)ChO (Ch = S, Se) were tested as cathode materials against graphite anodes (single cells); They perform outstandingly at very high charge rates (270 mA g^-1, 80 cycles) and, at a charge rate of 30 mA g^-1, exhibit charge capacities of about 120 mA h g^-1. Compared to highly optimized Li_1-xCoO₂ cathode materials, these novel anti-perovskites are easily produced at cost reductions by up to 95% and, yet, possess a relative specific charge capacity of 75%. Moreover, these iron-based anti-perovskites are comparatively friendly to the environment and (Li₂Fe)ChO (Ch = S, Se) melt congruently; the latter is advantageous for manufacturing pure materials in large amounts.

Full text of DOI:10.1021/jacs.7b04444

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Article
Anti-Perovskite Li-Battery Cathode Materials.
Kwing To Lai, Iryna Antonyshyn, Yurii Prots, and Martin Valldor
J. Am. Chem. Soc., Just Accepted Manuscript • Publication Date (Web): 23 Jun 2017
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Anti-Perovskite Li-Battery Cathode Materials.
Kwing To Lai,† Iryna Antonyshyn, Yurii Prots, and Martin Valldor*,‡
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Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straẞe 40, DE-01187 Dresden, Germany
ABSTRACT: Through single-step solid-state reactions, a series of novel bichalcogenides with the general composition
(Li2Fe)ChO (Ch = S, Se, Te) are successfully synthesized. (Li2Fe)ChO (Ch = S, Se) possess cubic anti-perovskite crystal struc-
tures, where Fe and Li are completely disordered on a common crystallographic site (3c). According to Goldschmidt calcu-
lations, Li+ and Fe2+ are too small for their common atomic position and exhibit large thermal displacements in the crystal
structure models, implying high cation mobility. Both compounds (Li2Fe)ChO (Ch = S, Se), were tested as cathode materials
‒
1
against graphite anodes (single cells); They perform outstandingly at very high charge rates (270 mA g , 80 cycles) and, at
‒
‒
1
1
a charge rate of 30 mA g , exhibit charge capacities of about 120 mA h g . Compared to highly optimized Li1‒xCoO2 cathode
materials, these novel anti-perovskites are easily produced at cost reductions by up to 95 % and, yet, possess a relative
specific charge capacity of 75 %. Moreover, these iron-based anti-perovskites are comparatively friendly to the environment
and (Li2Fe)ChO (Ch = S, Se) melt congruently; the latter is advantageous for manufacturing pure materials in large amounts.
1. Introduction
SrTiO313 inversely related to anti-perovskites, like zero-
thermal-expansion material Mn3(Ge0.5Cu0.5)N,14 supercon-
ductor Ni3MgC,15 and superionic conductors Ag3SI,16
Energy storage materials represent one of the most im-
portant research topics today and the focus is on solid-
state rechargeable batteries, as a result of their relative safe
use and long-life expectancy. Presently, Li-ion batteries re-
ceive most attention because they have high charge den-
sity. Although the demand for more efficient batteries in
mobile technologies steadily grows, our stand-point is al-
‒
Li3BrO, and Li3ClO.17 18 Recently, a new type of cation va-
cancy ordered anti-perovskite, (Fe2)SeO ( = vacancy)
was discovered.19 Given the fact that Br, as in Li3BrO, has

a similar ionic size as Se2 ,20 the new battery materials
(Li2Fe)ChO (Ch = S, Se, Te) were discovered, and the first
investigations thereof will be presented here.

most 15 years old concerning the battery cathode,1 2 so the
present call in 2017 is the development of new electrode

4
materials.3 At present, advanced Li-battery cathode ma-
2. Methods
terials like olivine type Li1xFePO4,5 delafossite structured
2.1. Materials synthesis. For the solid-state reactions of
the Li-containing anti-perovskites, x-ray pure Li2O precur-
sor was obtained by thermal decomposition of LiOH (Alfa
Aesar, 98 %) according to Brauer.21 All quaternaries were
synthesized by the same reaction: Li2O + Fe + Ch 
(Li2Fe)ChO, with Fe (Alfa Aesar, 3N), S (Alfa Aesar, 99.5 %),
Se (Alfa Aesar, 5N), and Te (Alfa Aesar, 4N). The constitu-
ents were mixed in an agate mortar and subsequently
pressed into pellets. All pellets were placed in corundum
crucibles (Aliaxis, Frialit-Degussit, AL23) that were loaded
into silica ampoules (QSIL AG Quarzschmelze, Ilmenau)
and temporarily shut with a rubber stopper. Outside the
glovebox, the ampoules were attached to a turbo-rotary
pump station and subsequently sealed when the inner
pressure was below 104 mbar. All samples were heated up
to about 750 C at a rate of 50 C h . This temperature was
held for 210 hours before quenching in water. The result-
ing pellets appeared black but turned dark-brown on
grinding. All preparations and sample handling were done
in an Ar-filled glove box with O2 and H2O levels below 1
ppm (MBraun).
Li1xTMO2 (TM = Co,6 Mn7), and spinel Li1+xMn2O4 are
8
used. To readily extract and insert Li+ ions, the host-lattices
have to allow for cation migration: Li1xFePO4 has Li+-filled
1-D tunnels, Li1xCoO2 has a 2-D layer-like crystal structure
with Li+ ions between two adjacent CoO2-layers, and
Li1+xMn2O4 is a 3-D structure where Li+ enters interstitial
sites. All three have high charge capacity per weight, but
they differ in other aspects; Li1xFePO4 is cheap and non-
hazardous but the Li+ migration is hampered by Li‒Fe dis-
order,9 which decreases battery life-times and charge/dis-
charge rates. Li1xCoO2 can be charged/discharged at high
rates but is very expensive due to limited resources of en-
vironmentally unfriendly cobalt. Li1+xMn2O4 is cheap and
work at high charging rates but the working voltage causes
irreversible deterioration of battery parts.10 Other oxide
candidate materials have significantly less charge density
or lower charge rates, making them unsuitable for applica-
tions. Non-oxide Li-sulphur battery materials are being de-
veloped11 but they have short battery life-times connected
to irreversible, dual migration of sulphur and lithium.12

1
In solid-state anti-structures, anions and cations have
literally switched places: this way is classic perovskite
2.2. Materials characterization. Powder x-ray diffraction
measurements were performed using Guinier cameras
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̅
(Huber) equipped with an image-plate detector using a
CoK x-ray source. Powdered (Li2Fe)SO sealed in a silica
capillary was investigated at the beamline ID22 at the Eu-
ropean Synchrotron Radiation Facility (ESRF) in Grenoble
(France). A single crystal of (Li2Fe)SeO mounted inside an
argon filled thin-walled silica capillary was investigated on
a Rigaku AFC7 diffractometer with a CCD camera as detec-
tor (Saturn 724+) and a MoK x-ray source. The software
JANA200622 was used to compare observed diffraction data
with structural model patterns. Thermal analyses were per-
formed with a STA449C (NETZSCH) inside a glove box
(MBraun). For elemental analyses by inductively coupled
plasma-optical emission spectroscopy (ICP-OES) on a ma-
trix matched calibrated Vista RL (Varian), the samples
were digested with a solution of ethylene-diamine-
tetraacetic acid (EDTA, 3.5 mL 0.02 M) and acid mixture
(2.5 mL HCl:HNO3, 1:1) in a turboWAVE (MLS-GmbH) at
120 ˚C for 15 minutes. The solutions were then transferred
to 50 mL volumetric flasks and filled with ultrapure water.
group 푃푚3푚. (Table S2, Supporting Information). Accord-
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ingly, Li and Fe are randomly distributed while sharing the
same positions on the atomic lattice. (Li,Fe) and Ch to-

gether form a cubic close-packing where O2 ions occupy
octahedral voids.
Powder x-ray diffraction data of (Li2Fe)TeO (Figure 1c)
are well described with an 4H-hexagonal anti-perovskite
structure model (Figure 2b), inversely related to that of
BaCrO3.23 Going from cubic (Ch = S, Se) to hexagonal (Ch =
Te) perovskites, the condensation of octahedra increases,
going from purely vertex-sharing to partly face-sharing.
Consequently, the lattice dimensionality changes drasti-
cally (Figure 2). There are two different cation sites in
Li2FeTeO: one site is fully occupied by Li and the other site
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contains a Li/Fe mixture (Figure 2b). O2 occupies two
neighbouring octahedral voids in a hexagonal close-pack-
ing of Li‒Fe‒Te.
2.3. Electrochemical measurements. Aluminium and cop-
per plates were used as current collectors for cathode and
anode, respectively. For preparation of slurries, the battery
cathode material (Li2Fe)ChO (Ch = S, Se) or anode graphite
(Alfa Aesar, 99.8 %, ~325 mesh) was mixed with carbon
black (Alfa Aesar, acetylene compressed, 99.9+ %, S>A, 75

1

1
m2 g , bulk density 80‒120 g L ), and polyvinylidene fluo-
ride (PVdF, Sigma Aldrich) in mass ratio 85:5:10 inside the
organic solvent N-methylpyrrolidone (NMP, Sigma Al-
drich, anhydrous, 99.5 %). All slurries were manually dis-
tributed on respective metallic plate (25 cm2) with subse-
quent heating at 100 oC during 1‒2 hours for organic solvent
(NMP) removal. About 0.3 grams of active material was
used for each trial battery. A separator of non-woven ma-
terial (Freudenberg, FS2226) was wetted with commer-
cially available 1.0 M LiPF6 in ethylene carbonate (EC) and
ethyl methyl carbonate (EMC) mixture (50:50 by volume,
Sigma Aldrich). The battery set-up was placed in plastic
bag with additional amounts of electrolyte. All prepara-
tions and electrochemical measurements were performed
in an Ar-filled glove box (MBraun) using a BioLogic SP300
potentiostat.
Figure 1. (a) Synchrotron x-ray diffraction powder pattern of
(Li2Fe)SO and laboratory camera powder x-ray diffraction
data of (b) (Li2Fe)SeO and (c) (Li2Fe)TeO. In (a), insets show
the high angle range (down) and intensities from secondary
phases (up), marked with asterisks, with a bar corresponding
to 1 % of the maximum diffraction intensity.
3. Results
3.1. Reaction products. For polycrystalline samples, a
thermal quenching after the main reaction proved neces-
sary to prevent partial decomposition of each anti-perov-
skite into binaries, like Li2Ch and iron oxides. All obtained
powders appeared dark red-brown while small crystals
were black. In all syntheses, there were no obvious reac-
tions between sample and crucible or silica tube. The de-
composition into binaries was much less obvious for single
crystals, as obtained by melting, although cooled at much
lower rates. A tentative explanation would be that the de-
composition into binaries initiates at crystallite surfaces
and its rate is proportional to the sample surface area. X-
ray diffraction data from single crystalline (Li2Fe)SeO (Ta-
ble S1, Supporting Information) and powder data of
(Li2Fe)ChO (Ch = S, Se, Figure 1a,b) indicate that both are
cubic anti-perovskites (Figure 2a) described by the space
Single-step syntheses result in highly crystalline materi-
als of at least 95% purity as estimated from x-ray powder
diffraction data (Figure 1). Unit cell volumes, as normalised
per formula unit (f.u.), increase expectedly through

1
SSeTe (59.871(2), 63.977(2), 75.068(3) Å3 f.u. ). To ana-
lyse relative atomic compositions, also with respect to elec-
tron poor lithium, complementary inductively coupled
plasma-optical emission spectroscopic (ICP-OES) analyses
were performed; All results strongly support the proposed
compositions (S4, Supporting Information).
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Figure 3. Differential thermal analysis (DTA) and thermo-
Figure 2. (a) Cubic anti-perovskites (Li2Fe)ChO (Ch = S, Se)
and (b) 4H-hexagonal anti-perovskite (Li2Fe)TeO with em-
phasized octahedra around oxygen.
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gravimetric (TG) data of (Li2Fe)SeO in flowing argon gas,
where arrows mark curve anomalies and measuring direc-
tions. An instrumental DTA curve feature is dashed.
3.2. Thermodynamic investigations. Under inert condi-
tions, an as-prepared powder of (Li2Fe)SeO melts congru-
ently at 1020 C and re-solidifies at 1000 C (Figure 3). X-
ray powder diffraction data confirm that there is no phase
deterioration at 1000 C and those of a melted and re-crys-
tallised sample (heated to 1250 C) indicate only tiny
amounts of secondary phases (Figure S5, Supporting Infor-
mation). The identical unit cell size of pristine and melted
samples also supports the congruent-melt scenario. A sim-
ilar behaviour is observed for (Li2Fe)SO (Figures S5‒S6,
Supporting Information) but its melting temperature is
980 C. The first order transition with only minor weight
change for (Li2Fe)ChO (Ch = S, Se) is a great advantage for
preparative works.
3.3. Electrochemical Li-charge/discharge. In a battery set
up with anti-perovskite (Li2Fe)SeO as cathode and graph-
ite as anode, the charging can be described with the gen-
eral reaction: (Li2Fe)SeO + nC(graphite) --> (Li2xFe)SeO +
LixCn. Thereby changes the average oxidation state of Fe
from +2 to +(2+x). During battery discharge, this reaction
is reversed. The Li extraction from the cathode is often as-
sumed to be rate limiting for charge/discharge processes.
Crystal structure investigations, presented above, cannot
distinguish between dynamic or static Li‒Fe disorder.
However, the structurally related anti-perovskites Li3BrO
and Li3ClO are reported to have dynamic Li disorder and
‒
remarkable Li+-ionic conducting properties.17 18
A
(Li2Fe)SeO ‒ graphite battery (Figure S9, Supporting Infor-
A slow deterioration of (Li2Fe)ChO (Ch = S, Se) in air is
clearly visible by eye, e.g. polycrystalline pieces crumble,
and this behavior was investigated: (Li2Fe)ChO (Ch = S, Se)
were left at room temperature in controlled, dry air during
5 hours and in normal air with 30 % moisture during 1.5
hours. From subsequent x-ray diffraction investigations
(Figures S7‒S8, Supporting Information) the reason is
clear: (Li2Fe)SeO endures dry air although oxygen is pre-
sent, but moist air leaches Li from the investigated phase
according to: (Li2Fe)SeO + 3x/2 H2O + x/4 O2  (Li2‒
xFe)SeO + x Li(OH)(H2O). (Li2Fe)SO reacts even more pro-
nounced with moist air (Figures S7‒S8, Supporting Infor-
mation). This means that water moisture in combination
with oxygen is the true reason for deterioration of our
novel Li-based anti-perovskites at room temperature.
mation) was extensively tested and the highest specific
charge current was 270 mA g‒ (Figure 4); During 10
1
charge/discharge cycles, there is no deterioration of the
battery (Figure 4) and the specific charge capacity (about
‒
1
60 mAh g ) remains almost constant during 80 cycles (Fig-
ure S9, Supporting Information).
Figure 4. Ten charge/discharge curves of a (Li2Fe)SeO –
graphite battery.
For an electrochemical extraction up to x = 1, which
would result in (LiFe)SeO, the theoretical charge density
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
would be Qmax = nF(3600M) 1 = 162.8 mA h g , where n is
1
ther polymer matrices nor liquid electrolytes. Alterna-
the number of Li+ ions in moles, F is the Faraday constant
= 96485 s A mol , and M is the molar mass of (Li2Fe)SeO =
1
2
3
4
tively, the recently reported solid-state electrolyte, involv-
ing Li-glass,26 can be used between the anode and the cath-
ode.

1

1
164.69 g mol . By the same calculation, (Li2Fe)SO theoret-
ically reaches even higher values of 227 mA h g (Figure
1
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S10, Supporting Information). This can be compared with

1
experimental (theoretical) values of 160 (274) mA h g for
Li1‒xCoO2.24 The reason for presuming the stability of 50 %
delithiated (LiFe)ChO ( = vacancy, Ch = S, Se) is the ex-
istence of cation vacant (Fe2)SeO,19 where one third of the
cations are missing without crystal structure break-down.
Performed charges/discharges indicate that about 3/4 of
the theoretical charge was already obtained for (Li2Fe)SeO:
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120 mA h g at a rate of about 30 mA g = 0.25C (Figure S9,
Supporting Information). The size of the atomic lattice
(unit cell parameter a) does not change significantly for a
charged (delithiated) material (Figure S11, Supporting In-
formation), which is a good indication of advantageous,
negligible lattice strain (volume change) for charge/dis-
charge processes.
Figure 5. Li+ migration paths in (a) olivine LiFePO4, (b)
delafossite LiCoO2, (c) spinel Li2Mn2O4, (d) anti-perovskite
(Li2Fe)ChO (Ch = S, Se), and (e) anti-perovskite (Li2Fe)SeO
with refined Li split-positions. All anions have been omitted
for clarity and the shortest distances (in Å) between two adja-
cent Li-sites are marked. Partial occupied sites are indicated
with corresponding filling of atom spheres.
4. Discussions
There are further promising Li-battery cathode materials
that are still being optimized. For example, LixV2O5, where
x can be even up to 3,27 has a very high charge density but
low charge rates, which were improved by increasing the
active surface28 or implementing it in a glassy composite.29
Unfortunately, the high charge capacity can only be re-
tained over few charge/discharge cycles. Moreover, vana-
dium is relatively expensive and its oxides are harmful to
the environment. In contrast, both Li2MnO330 and FeF331 are
environmentally viable and are also candidates for the use
as battery cathodes due to low costs and high energy den-
sities. However, both compounds suffer from strongly fad-
ing charge capacities during charge/discharge cycling, de-
spite the extensive topology optimizations, e.g. nano-wires
of FeF332 and nano-structured Li2MnO3.33 In contrast, the
cubic title compounds exhibit only faint capacity loss dur-
ing 80 charge/discharge cycles at high rates. However,
even longer experiments have to be performed to establish
the long-term stability of anti-perovskite cathodes.
To estimate the Goldschmidt tolerance factor13 for the
two cubic title compounds, an average ionic radius was as-
sumed for the (Li2Fe)-site. The calculated tolerance factors
and the ideal cubic cell parameters are smaller than obser-
vations (Figure S12, Supporting Information). This suggests
relatively large voids for the cations to occupy and agrees
with the extraordinary Li migration rate and thermal
atomic displacements in crystal structure descriptions.
As compared to delafossites LiTMO2 (TM = Co,6 Mn,7
Ni), the cubic anti-perovskite title compounds have +2
pristine oxidation states of Fe while TM is +3 in delafos-
sites. This lowers the work potential window for anti-per-
ovskite cathodes, and standard battery constituents re-
main stable: the anti-perovskites can be charged/dis-
charged without destroying anodes or electrolytes. This is
advantageous in comparison with high-voltage cathodes,
like Li1+xMn2O4,8 where a thermal run-away, due to over
voltage, decomposes the fluorine based electrolytes, which
are discussed as potential hazards for users and environ-
ment.25 Nevertheless, the working voltage of anti-perov-
skite batteries can be designed by selecting another anode
materials instead of graphite; this might increase the bat-
tery voltage and, thus, offer even higher energy densities.
In conclusion, our novel anti-perovskites can be readily
produced, are environmentally friendly, and perform well
enough as Li-battery cathodes to compete with Li1‒xCoO2.
(Li2Fe)ChO (Ch = S, Se) can be charged at high rates and
the material cost for (Li2Fe)SO is reduced by about 95 % in
comparison to Li1‒xCoO2. Hence, at viable costs and with
less environmental issues, the cubic anti-perovskite title
compounds can be used in larger energy storage stations
or power vehicles safely.
The cubic title compounds allow for isotropic 3D Li+ mi-
gration, which is similar to the situation in Li1+xMn2O4,8 but
more advantageous than Li+ migrations in layers of Li1‒
‒
5
x(Co,Mn)O26 7 and in columns of Li1‒xFePO4 (Figure 5). The
isotropic Li migration in investigated anti-perovskites is
stable against minor crystallographic faults, in contrast to
the high fault-sensitivity in Li1‒xFePO4.9 Moreover, due to
the structural similarities, an all-solid battery is possible
with any of the cubic title compounds as cathode, Li3XO (X
ASSOCIATED CONTENT
Supporting Information. Crystal structure models based on
single crystal and powder x-ray data, CIF-file of (Li2Fe)SO,
CIF-file of (Li2Fe)SeO, ICP-OES data, (Li2Fe)SO DTA/TG data,
x-ray data on melted samples, x-ray data on samples that were
left in dry air or in moist air, x-ray data on partly and highly
charges states of cathode material, charge/discharge curves,
‒
= Cl, Br)17 18 as electrolyte, and an anode of perhaps
Fe2SeO.19 Lattice mismatches would be small and tech-
niques such as molecular beam epitaxy or laser ablation
might be applied for making ultra-thin batteries with nei-
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(11)
J. K.; Brummer, S. B. J. Electrochem. Soc. 1979, 126, 523‒527.
(12) Manthiram, A.; Fu, Y.; Su, Y. –S. Acc. Chem. Res. 2013,
46, 1125‒1134.
Rauh, R. D.; Abraham, K. M.; Pearson, G. F.; Surprenant,
battery specific capacities. This material is available free of
charge via the Internet at http://pubs.acs.org.
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AUTHOR INFORMATION
Corresponding Author
(13)
(14)
Goldschmidt, V. M. Sci. Nat. 1926, 14, 477‒485.
Song, X.; Sun, Z.; Huang, Q.; Rettenmayr, M.; Liu, X.;
Seyring, M.; Li, G.; Rao, G.; Yin, F. Adv. Mater. 2011, 23, 4690‒4694.
(15) He, T.; Huang, Q.; Ramirez, A. P.; Wang, Y.; Regan, K.
A.; Rogado, N.; Hayward, M. A.; Haas, M. K.; Slusky, J. S.; Inumara,
K.; Zandbergen, H. W.; Ong, N. P.; Cava, R. J. Nature 2001, 411, 54‒
*E-mail: martin.valldor@cpfs.mpd.de or m.valldor@ifw-dres-
den.de.
ORCID: 0000-0001-7061-3492
9
56.
(16)
(17)
15042‒15047.
(18)
Present Addresses
Reuter, B.; Hardel, K. Sci. Nat. 1961, 48, 161‒161.
Zhao, Y.; Daemen, L. L. J. Am. Chem. Soc. 2012, 134,
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† Department of Physics, The Chinese University of Hong
Kong, Shatin, Hong Kong
‡ Leibniz Institute for Solid State and Materials Research,
Helmholtzstraẞe 20, DE-01069 Dresden, Germany
Emly, A.; Kioupakis, E.; van der Ven, A. Chem. Mater.
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Valldor, M.; Wright, T.; Fitch, A.; Prots, Yu. Angew.
Author Contributions
All authors have given approval to the final version of the
manuscript.
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ACKNOWLEDGMENT
We thank Marcus Schmidt and Susann Scharsach for thermal
analyses, Gudrun Auffermann for elemental analyses, and
Mauro Coduri for assistance at ESRF. Liu Hao Tjeng and Juri
Grin are acknowledged for their invaluable support and help.
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SYNOPSIS TOC
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7
8
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13
30000
800
600
400
200
(Li2Fe)SO, 293 K
1 %
a
ESRF, ID22
λ = 0.400014(1) Å
*
*
*
*
14
20000
15
16
17
18
19
20
21
22
5
7
9
11
13
15
1000
10000
23
500
24
25
26
27
28
29
30
0
Yobs
24
30
36
42
48
54
Ycalc
31
0
32
33
34
35
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37
38
39
Yobs-Ycalc
5
45
55
0
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30
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60
2Theta (degr.)
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25000
15000
2000
(Li2Fe)SeO
(Li2Fe)TeO
1
2
3
4
c
b
λ = 1.78892 Å (CoKα1)
λ = 1.78892 Å (CoKα1)
5
6
1000
7
8
9
Yobs
Ycalc
Yobs
5000
0
Ycalc
10
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(Li2Fe)TeO
Li2Te (3 vol%)
0
Yobs-Ycalc
Yobs-Ycalc
10
20
30
40
50
60
70
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90
100
10
20
30
40
50
60
70
80
90
100
2Theta (degr.)
2Theta (degr.)
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a
S (Se)
Li2/3Fe1/3
O
a
a
a
Li1/3Fe2/3
b
Te
Li
c
a
a
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99
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60
40
20
0
1000 °C
(Li2Fe)SeO
endo
exo
in Ar-gas flow
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1020 °C
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T (°C)
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(Li2Fe)SeO - graphite
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80
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0
2.4
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9
10
11
12
13
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2.2
2.0
1.8
16
-20
-40
-60
-80
17
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1.6
20
21
22
23
1.4
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25
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1.2
28
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t (min)
800
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3.00
a
c
Li
b
d
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2.8
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Fe
Li2/3Fe1/3
Li
Li
2.81
Li1/2
1.83
e
P
Co
Mn
Fe1/3
Li2/6
LiFePO4
LiCoO2
Li2Mn2O4
(Li2Fe)ChO
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+
+ Li
Li2/3Fe1/3
C
O
S (Se)
_
+
Li
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