Journal of The Electrochemical Society, 161 (5) A663-A667 (2014)
0013-4651/2014/161(5)/A663/5/$31.00 © The Electrochemical Society
A663
Derivation of an Iron Pyrite All-Solid-State Composite Electrode
with Ferrophosphorus, Sulfur, and Lithium Sulfide as Precursors
Thomas A. Yersak,a,∗ Tyler Evans,b Justin M. Whiteley,b Seoung-Bum Son,c
Brian Francisco,b Kyu Hwan Oh,c and Se-Hee Leeb,∗,z
a Department of Nano Engineering, University of California San Diego, La Jolla, California 92093-0448, USA
b Department of Mechanical Engineering, University of Colorado at Boulder, Boulder, Colorado 80309-0427, USA
c Department of Materials Science and Engineering, Seoul National University, Seoul, 151-742, Korea
In order to address the poor energy density of bulk all-solid-state lithium-ion batteries a new composite electrode preparation method
is proposed. This study demonstrates the concurrent synthesis of the FeS2 active material and a glass electrolyte which is similar
to the (100-x)P2 S5 :xLi2 S system of glass electrolytes. This is accomplished through the successive mechanochemical and thermal
treatments of Fe2 P, S, and Li2 S. The composite electrode’s ionic conductivity of 5.46 × 10−5 S cm−1 at 60◦ C and specific energy
of 1.2 Wh g−1 versus a lithium metal anode suggest that this method may provide a more intimate solid-solid interfacial contact
between active material and glass electrolyte. The results of this study provide a completely new perspective on the preparation of
all-solid-state composite electrodes.
© 2014 The Electrochemical Society. [DOI: 10.1149/2.003405jes] All rights reserved.
Manuscript submitted December 10, 2013; revised manuscript received February 6, 2014. Published March 7, 2014.
Bulk all-solid-state composite electrode engineering conventionally approaches the problem of interfacial structuring from the perspective that the active material and the solid-state electrolyte must
each be prepared separately and then combined via mechanical mixing. Wetting the porous electrode with a liquid electrolyte creates
intimate interfacial contact. However, the power and energy density
of bulk all-solid-state batteries suffer because a solid-state electrolyte
cannot interface as intimately with the active material as a liquid electrolyte. For example, an all-solid-state electrode utilizing FeS2 and
the P2 S5 -Li2 S glass electrolyte had an active mass loading of only
32% in order to achieve FeS2 ’s theoretical capacity of 894 mAh g−1 .1
Similarly structured cells utilizing S or Li2 S as the active material suffer from the same limitations.2,3 While the bulk all-solid-state battery
architecture has demonstrated its value by enabling the reversible cycling of high capacity conversion active materials, further interfacial
engineering should address how to achieve practical electrode level
energy density.
Along these lines, hot isostatic pressing (HIP) was proposed as
a method to densify composite electrodes with the P2 S5 -Li2 S glassceramic for improved interfacial contact.4 HIP’ing is not appropriate
for active materials which may be reactive or decompose at high
temperatures. Pulsed laser deposition of P2 S5 -Li2 S glass electrolyte
coatings onto active material particles has also been suggested as a
way to improve interfacial contact and increase active material mass
loading.5,6 Another method involves mechanically preparing sulfur
composite electrodes at a temperature above sulfur’s melting point
so that sulfur can flow about P2 S5 -Li2 S glass-ceramic electrolyte
particles.7 An electrode prepared in such a manner was reported to
deliver a specific energy in excess of 1000 Wh kg−1 . Spark plasma
sintering8,9 and impregnation of active material sols into macroporous 3D electrolyte membranes10–14 have also been suggested for
all-solid-state batteries utilizing ceramic electrolytes other than the
P2 S5 -Li2 S system of glass-ceramics. Further, the development of polysulfidophosphates has blurred the distinction between active material
and solid-state electrolyte.15
In order to structure an intimate solid-solid interface this study
proposes that the active material and glass electrolyte former can be
synthesized concurrently as products of a single solid-state chemical reaction. Interfacial contact may then be dictated not only by the
mechanical properties of the composite electrode components, but
also by the process of phase nucleation and growth. In the study outlined here the concurrently synthesized active material and electrolyte
former are suggested to be FeS2 and P2 S5 , respectively.
∗
z
Electrochemical Society Active Member.
E-mail: [email protected]
Historically, the reaction of iron pyrite (FeS2 ) with ferrophosphorus (Fe2 P) at temperatures between 700 – 800◦ C was thought to
produce P2 S5 and FeS.16 In this two step process, FeS2 first thermally
decomposes into FeS and S.17 Sulfur then reacts with Fe2 P to form
P2 S5 and more FeS. P2 S5 can also be synthesized by the direct reaction of S with Fe2 P.18 Equation 1 proposes FeS2 and P2 S5 as the
byproducts for the reaction of S and Fe2 P at a temperature of 350◦ C.
The enthalpy of this reaction at standard state is −762.6 kJ mol−119 or
−674 kJ mol−120 depending upon the source of the P2S5 data so it is
expected that this reaction is thermodynamically favorable. The P2 S5
component of this proposed composite can then be mechanochemically modified with Li2 S to synthesize the 22.5P2 S5 :77.5Li2 S glass
electrolyte which will be intimately in contact with the FeS2 phase.
Equation 2 outlines this reaction assuming that Equation 1’s reaction
is complete with no other byproducts. This method should be contrasted with our previous FeS2 composite electrode preparation technique where FeS2 and carbon black are mixed with a pre-prepared
22.5P2 S5 :77.5Li2 S glass electrolyte.1
2Fe2 P + 13S → 4FeS2 + P2 S5 (350◦ C)
[1]
22.5(4FeS2 + P2 S5 ) + 77.5Li2 S → 90FeS2 + 22.5P2 S5 : 77.5Li2 S
[2]
Methods
All procedures to be outlined were conducted in a dry argon environment. The electrode composite was prepared via a three step process. First, 2 g total (2:13 molar ratio) of Fe2 P (Aldrich, 99.5%) and
Sulfur (Aldrich, 99.98%) were combined by planetary ball milling.
Material was milled in an airtight 500 mL stainless steel jar (Across
International) with two 16 mm diameter and twenty 10 mm diameter
stainless steel balls (Across International) for 20 hours at 500 rpm.
Second, the composite was heat treated in an evacuated flame sealed
borosilicate glass ampoule at 350◦ C for 3 hours with controlled temperature ramping and cooling both taking 1 hour. Third, planetary ball
milling was used to combine 0.5 g total (22.5:77.5 molar ratio) of the
heat treated composite and Li2 S (Aldrich, 99.999%, reagent grade).
Material was milled in an airtight 100 mL agate jar (Across International) with fifty 6 mm diameter and five 10 mm diameter agate balls
for 20 hours at 500 rpm. The materials resulting from the completion of the first, second, and third step are referred to as (BM), (BM
+ HT), and (BM + HT + BM) in the text and figures. BM is shorthand
for ball mill while HT is shorthand for heat-treatment.
To assemble test cells, a 200 mg glass electrolyte pellet separator
(ϕ = 13 mm) was first pressed at 1 metric ton inside a polyetheretherketone (PEEK) lined Ti test cell die.21 The electrolyte used for the
separator was the previously described mechanochemically prepared
Downloaded on 2016-03-06 to IP 130.203.136.75 address. Redistribution subject to ECS terms of use (see ecsdl.org/site/terms_use) unless CC License in place (see abstract).
A664
Journal of The Electrochemical Society, 161 (5) A663-A667 (2014)
Figure 1. Powder XRD patterns for the (BM),
(BM + HT) and (BM + HT + BM) samples.
Peaks are indexed to Fe2 P (open square), S (triangle), FeP (diamond), and cubic-FeS2 (star).
22.5P2 S5 :77.5Li2 S glass.22,23 For increased electronic conductivity,
10 wt% of carbon black (TimCal, C65) was added to the composite
electrode using an agate mortar and pestle. 5 mg of the composite
electrode was then pressed to one side of the glass electrolyte pellet
at 5 metric tons and an LiIn alloy (FMC Lithium Corp., Lectro Max
Powder 100 and Indium powder, Alfa Aesar, Puratronic 99.999%)
was attached to the opposite side of the pellet at 1 metric ton. The LiIn
alloy has a potential of 0.62 V vs. Li+ /Li for a limited compositional
range24 so voltage profile figures are given with respect to both LiIn
and Li metal. Calculations of specific energy assume Li metal as the
anode and all specific capacities and current densities are given with
respect to the total composite electrode mass including carbon black.
The test cells were cycled at 60◦ C under constant current constant
voltage (CCCV) cycling parameters.
The composite electrode was characterized by Cu-Kα powder
X-ray diffraction, FIB-SEM EDS analysis, cyclic voltammetry, and
Raman spectroscopy. The FIB sample was prepared as previously
described.1 Cyclic voltammetry was used to measure the electronic
conductivity of the composite electrode by sweeping symmetric cells
as presented in Figure 4a. To measure ionic conductivity, a composite
electrode pellet without a carbon black additive (150 mg) was sandwiched between two layers of the 22.5P2 S5 :77.5Li2 S glass electrolyte
(150 mg each) in order to block electron flow as presented in Figure 4b.
A similar cell configuration was used previously, but here junction potentials and resistance to charge transfer are considered negligible at
layer interfaces.25 The contributions from the electron-blocking glass
electrolyte layers can be subtracted out by considering that 1/σelectrode
= Rtotal – 2/σelectrolyte . The ionic conductivity of the 22.5P2 S5 :77.5Li2 S
glass electrolyte used in the experiment was measured to have an ionic
conductivity of 2.91 × 10−4 S cm−1 at 25◦ C and 1.297 × 10−3 S cm−1
at 60◦ C. DC polarization measurements at 10 mV were used to calculate the ionic conductivity of the electrodes. The calculations use the
stabilized current values because, after a period of transient decay, the
stabilized current is thought to be totally ionic. Raman spectra were
recorded using a JASCO NRS-3100 system equipped with a 532 nm
laser at a power level of 0.1 mW focused through a 20× objective
lens. Power levels higher than this were observed to cause sample
degradation. Raman shift was calibrated using a silicon standard and
accuracy was estimated to be ±7 cm−1 . As the dark color of the material led to weak Raman scattering, 15 accumulations of 45 seconds
each were typically averaged to increase the signal-to-noise ratio.
Results
Powder XRD was used to identify the phases present over the
course of the FeS2 composite electrode preparation. Figure 1 provides the XRD patterns for samples (BM), (BM + HT), and (BM +
HT + BM). From the pattern for sample (BM), it was determined
that Fe2 P does not react with S during mechanical milling. After
heat treating sample (BM) at 350◦ C a solid-state reaction was ob-
served to occur. The pattern for sample (BM + HT) has new peaks
which can be assigned to iron pyrite (FeS2 ) and orthorhombic FeP26,27
while peaks for Fe2 P disappear. Three weak peaks corresponding to
sulfur’s three strongest diffractions are also observed. Residual sulfur is consistent with the observation of sulfur crystallization on the
inside surface of the evacuated glass ampoules after heat-treatment
(Supporting Figure 1). After the addition of Li2 S, no new phases are
observed in the pattern for sample (BM + HT + BM). Depending on
the composition residual crystalline Li2 S is frequently observed when
the (100-x)P2 S5 :xLi2 S glass is mechanochemically prepared,21,22 but
no crystalline Li2 S peaks are observed here. This may be due to the
amorphization of Li2 S or a reaction between Li2 S and a glass former.
Diffraction peaks for FeS2 and FeP are found to broaden and reduce in intensity after the second ball milling step which is consistent
with the reduction of average crystallite size by mechanical grinding.
Diffraction peaks for crystalline P2 S5 are not observed in any of the
samples.
FIB-SEM and EDS mapping of sample (BM + HT) provided in
Figure 2 do not support the case for the formation of P2 S5 or another
glass former. A SEM image of a cross-sectioned sample is provided
in Figure 3a. Close inspection reveals particles embedded in a porous
material. EDS mapping for P, S, and Fe are provided in Figure 2b, 2c,
and 2d. It is noted that EDS cannot distinguish P in the sample from
the Pt supporting structure. Dispersion of Fe throughout the entire
sample is consistent with the formation of FeS2 and FeP. If P2 S5 were
Figure 2. a) FIB-SEM image of a crossed sectioned (BM + HT) pressed
pellet. Close inspection reveals particles embedded in a matrix. b-d) EDS
mapping for P, S, and Fe. P and S are segregated while Fe is well dispersed.
Downloaded on 2016-03-06 to IP 130.203.136.75 address. Redistribution subject to ECS terms of use (see ecsdl.org/site/terms_use) unless CC License in place (see abstract).
Journal of The Electrochemical Society, 161 (5) A663-A667 (2014)
Figure 3. Raman spectroscopy of the (BM + HT + BM) sample compared to
cubic-FeS2 , Li2 S, and the 22.5P2 S5 :77.5Li2 S glass electrolyte. Peaks at 422
cm−1 , 378 cm−1 , and 340 cm−1 are attributed to cubic-FeS2 while the peak
at 480 cm−1 is attributed to residual S. The PS4 3− ion, indicative of a glassy
ionic conductor, has been reported at 420 cm−1 . The 422 cm−1 peak attributed
to FeS2 overlaps is superimposed with the PS4 3− peak.
synthesized it would be expected that signals for P and S would be well
mixed, however, the opposite is true. Area mapped to P is segregated
from the area mapped to S. The particles observed in SEM have a
high concentration of P signals so these particles are attributed to the
FeP phase.
Raman spectroscopy provided in Figure 3 was used to characterize the ionically conductive component of the (BM + HT + BM)
electrode. The Raman spectrum for the (BM + HT + BM) electrode
is compared to that for FeS2 , Li2 S, and the 22.5P2 S5 :77.5Li2 S glass
electrolyte. Four main peaks are observed at 480 cm−1 , 422 cm−1 ,
378 cm−1 , and 340 cm−1 . The peak at 480 cm−1 is attributed to unreacted S in the composite28,29 while the peaks at 422 cm−1 , 378 cm−1 ,
and 340 cm−1 coincide with the peaks for FeS2 . A peak at 420 cm−1
is typically assigned to the thiophosphate ion, PS4 3− , of the (100x)P2 S5 :xLi2 S system of glass-ceramic electrolytes.30 Observation of
A665
the PS4 3− ion would confirm that the composite electrode contains
the local structure of the glass electrolyte and indirectly suggests the
formation of P2 S5 or another glass former. Qualitatively, the ratio of
the 422 cm−1 to 378 cm−1 peak intensities is much smaller for FeS2
than it is for the electrode. The increase in the ratio of these peaks is
attributed to the presence of PS4 3− . Unfortunately, the (BM + HT
+ BM) electrode powder exhibited poor Raman scattering so a meaningful peak deconvolution could not be performed. To substantiate our
claim for the formation of a glassy electrolyte, the ionic transport of the
(BM + HT + BM) sample was measured at 25◦ C and 60◦ C. A previous study used cyclic voltammetry to measure the ionic conductivity
of mixed conductors using the same symmetric cell configuration presented in Figure 4b.31 However, for the (BM + HT + BM) sample
we observed a significant amount of non-Ohmic current using the
cyclic voltammetry method. For this reason, the ionic conductivity
was measured by performing 10 mV DC polarization measurements
on symmetric multi-layer test cells (Figure 4d). In the DC polarization
method, the ionic conductivity is calculated by measuring the stabilized current after transient decay. It is noted that the transient current
of the (BM + HT + BM) sample tested at 60◦ C took far longer to decay than it did in other tests. The electronic conductivity was measured
by the cyclic voltammetry method. As a control, a conventional composite electrode was prepared by mixing nano-sized natural pyrite and
22.5P2 S5 :77.5Li2 S in a weight ratio of 56:44. This weight ratio corresponds to the theoretical weight ratio of the products in Equation 2.
The natural FeS2 is the same as that used in a recent study by Son
et al.32
The electronic conductivity of a conventional composite electrode
without carbon black additive is only 1.81 × 10−5 S cm−1 while the
electronic conductivity of the (BM + HT + BM) composite electrode
without carbon black is 4.94 × 10−4 S cm−1 (Figure 4c). The good
electronic conductivity of the (BM + HT + BM) electrode is attributed
to the presence of the unexpected FeP phase.33 On the other hand, the
ionic conductivity of the conventional electrode is superior to that of
the (BM + HT + BM) electrode. At 60◦ C, the conventional electrode
has an ionic conductivity of 2.82 × 10−4 S cm−1 while the (BM +
HT + BM) electrode has an ionic conductivity of approximately 5.46
× 10−5 S cm−1 (Figure 4d) at 60◦ C.
The results of constant current constant voltage (CCCV) cycling at
60◦ C are provided in Figure 5. All specific capacities are normalized
to the total mass of the composite electrode including carbon black.
In anticipation of excess Li2 S utilization, the (BM + HT + BM)
electrode was initially overcharged to provide an extra 114 mAh g−1
Figure 4. a) Schematic of the symmetric test cell used to
measure the electronic conductivity of the (BM + HT +
BM) sample. b) Schematic of the symmetric test cell used
to measure the ionic conductivity of the (BM + HT + BM)
sample. c) Cyclic voltammetry i-V curves at 25◦ C and calculated electronic conductivity for the (BM + HT + BM)
sample (solid blue) and a conventional control electrode with
a composition dictated by Equation 2 (dashed blue). d) 10
mV DC polarization i curves for the same two electrodes at
25◦ C (blue) and 60◦ C (red). The stabilized current was used
to calculate Ohmic ionic resistance in order to estimate ionic
conductivity.
Downloaded on 2016-03-06 to IP 130.203.136.75 address. Redistribution subject to ECS terms of use (see ecsdl.org/site/terms_use) unless CC License in place (see abstract).
A666
Journal of The Electrochemical Society, 161 (5) A663-A667 (2014)
of capacity. An overcharge capacity of 114 mAh g−1 indicates that
59% of the Li2 S added to the (BM + HT + BM) sample during
the final ball milling step was electrochemically oxidized. We have
previously reported on the electrochemical utilization of excess Li2 S in
composite electrodes with the 22.5P2 S5 :77.5Li2 S glass electrolyte.21
In the prior study activation of excess capacity was correlated with the
consumption of crystalline Li2 S, however, possible contributions to
excess capacity from non-crystalline Li2 S was not ascertained. Even
though the XRD spectra for (BM + HT + BM) does not indicate
the presence of crystalline Li2 S it is reasonable that Li2 S may still be
available for electrochemical utilization.
Assuming complete conversion of Equation 1, the (BM + HT
+ BM) electrode composite should theoretically only deliver 500
mAh g−1 through the complete reduction of FeS2 . On the other hand,
(BM + HT + BM) could also theoretically deliver 1024 mAh g−1 assuming that no solid-state reactions occurred during electrode preparation and that the S and Li2 S precursors were fully utilized. On its
initial discharge (cycle 2), the electrode delivers a specific discharge of
721 mAh g−1 . This discharge capacity, which is in between the two
extreme values of 500 mAh g−1 and 1024 mAh g−1 , provides further
evidence for the complex composition of the (BM + HT + BM) composite electrode. The sweeping voltage profile between 2.4 – 1.9 V is
attributed to the electrochemical reduction of residual S and of S created by the oxidation of excess of Li2 S during the initial overcharge.
A small fraction of capacity may also be attributed to utilization of
Li2 S in the glass electrolyte separator pellet.21 As expected, subsequent discharge profiles are much different than the initial discharge
which indicates either a change in chemistry or kinetics.1,21,34 Quite
impressively, the (BM + HT + BM) electrode delivers a specific
energy density of 1,200 Wh kg−1 (vs. Li+ /Li). On its 40th cycle the
(BM + HT + BM) electrode delivers a specific energy of 1,130
Wh kg−1 (vs. Li+ /Li), which attests to a good stability (Supporting
Figure 2). The lower discharge profiles, which are associated with
the redox of Fe2+ → Fe0 , are observed to fade faster than the stable
plateau at approximately 2.3 V which is attributed to the redox of S2 2−
→ 2S2− . This result is consistent with prior results obtained when cy-
Figure 5. 1st 10 cycles for a (BM + HT + BM) electrode with 10 wt% carbon
black. The cell is initially overcharged in order to activate 114 mAh g−1 of
additional residual sulfur capacity.
cling a conventionally prepared composite electrode with FeS and S
as the active material and a 22.5P2 S5 :77.5Li2 S glass as the solid-state
electrolyte.21
A rate test was initiated after ten cycles at a low discharge current
density of 30 mA g−1 . Three recovery cycles were applied for every
two cycles of high discharge rate. The charge current density was kept
constant at 30 mA g−1 . The average capacities of several different test
cells are provided in Figure 6a with an estimate of standard deviation.
The test cell provided in Figure 5 and Supplementary Figure 2 is
included in this average. It is observed that the capacity of the (BM
Figure 6. a) Rate test of the (BM + HT + BM) electrode. Given capacities are an average with an estimated
standard deviation. b) Voltage profiles for the cell presented in Figure 5 at 30, 40, 80, 200, 400, and 800 mA
g−1 , or equivalently, 0.11, 0.15, 0.30, 0.75, 1.51, and
3.01 mA cm−2 . The initial discharge profile is given as
a reference. c) Ragone plot summarizing Figure 6b).
Downloaded on 2016-03-06 to IP 130.203.136.75 address. Redistribution subject to ECS terms of use (see ecsdl.org/site/terms_use) unless CC License in place (see abstract).
Journal of The Electrochemical Society, 161 (5) A663-A667 (2014)
+ HT + BM) electrode is not stable at higher rates. However, the
capacity recovers when the current density is reduced. Figures 6b
and 6c summarize the rate test for the cell presented in Figure 5.
As the current density is increased, the lower voltage plateau, which
we attribute to the reduction of Fe2+ , is observed to disappear. At a
moderate current density of 400 mA g−1 , the Ragone plot (Figure 6c)
indicates that the electrode delivers a specific power of 706 W kg−1 .
We suspect that the lower voltage plateau is associated with either
the reduction of FeS or an intermediary Li2-x FeS2 phase to Li2 S and
Fe0 .1,34–36 The lower plateau disappears because the kinetics of FeS
or Li2-x FeS2 reduction may be limited by the solid state diffusion of
Fe0 atoms needed to nucleate separate phases of Li2 S and Fe0 .
Discussion
The characterization of the (BM + HT) material yields data that
does not support the formation of the glass former, P2 S5 . As mentioned, powder XRD peaks for crystalline P2 S5 are absent and elemental mapping indicates that signals for P and S are segregated. The
observation of FeP attests to the inadequacy of the proposed reaction
mechanism. Nevertheless, the ionic conductivity and Raman spectroscopy of the (BM + HT + BM) electrode indicate the presence of
an ionically conductive glassy electrolyte. Indeed, the ionic conductivity of the (BM + HT + BM) electrode was nearly double that of
the convention control electrode with prepared glass electrolyte.
Mechanochemical milling of (BM + HT) with Li2 S will yield a
material with a heavily altered structure that may include a glassy
electrolyte. Powder XRD results indicated that the initial ball milling
step did not induce a solid-state reaction, but the same may not be
true for the second ball milling step. The reactivities of FeP, S and
other possible unidentified reaction products under mechanochemical
action are not known. Preparation of sulfide glass electrolytes without
P2 S5 as a precursor is not without precedent. The mechanochemical
reaction of P, S and Li2 S has produced functional ionically conducting
glasses.28,29 P2 S3 has also been used as a glass former.37 To confirm
this suspicion EDS elemental mapping of the (BM + HT + BM)
sample should be performed to confirm the mixing of P and S signals.
Unfortunately, this characterization was not completed due to a lack
of resources.
Conclusions
We have demonstrated an electrode which delivers a specific energy of 1,200 Wh kg−1 which ranks it among the most energy dense
all-solid-state electrodes to be reported. Even though our proposed
reaction mechanism is incomplete it does provide a good starting
framework for understanding the coincident preparation of FeS2 and
glass electrolyte precursors. While the composition of the composite
electrode is not yet well understood, its high performance suggests
that much promise lies ahead for structuring interfaces via solid-state
reactions.
Acknowledgments
Funding for this study was provided by the National Science Foundation (NSF, CHE-1231048) and by the University of Colorado at
Boulder Dean’s Graduate Student Research grant. Special thanks are
given to Daniela Molina Piper and Dr. Chunmei Ban for discussion
and assistance with preliminary XRD data collection.
A667
References
1. T. A. Yersak, H. A. Macpherson, S. C. Kim, V. D. Le, C. S. Kang, S. B. Son,
Y. H. Kim, J. E. Trevey, K. H. Oh, C. Stoldt, and S. H. Lee, Advanced Energy Materials, 3(1), 120 (2013).
2. M. Nagao, A. Hayashi, and M. Tatsumisago, Electrochimica Acta, 56(17), 6055
(2011).
3. M. Nagao, A. Hayashi, and M. Tatsumisago, Journal of Materials Chemistry, 22(19),
10015 (2012).
4. H. Kitaura, A. Hayashi, T. Ohtomo, S. Hama, and M. Tatsumisago, J. Mater. Chem.,
21(1), 118 (2010).
5. Y. Sakurai, A. Sakuda, A. Hayashi, and M. Tatsumisago, Solid State Ionics, 182(1),
59 (2011).
6. K. Aso, A. Sakuda, A. Hayashi, and M. Tatsumisago, ACS Applied Materials and
Interfaces, 5(3), 686 (2013).
7. M. Nagao, A. Hayashi, and M. Tatsumisago, Energy Technology, 1(2-3), 186 (2013).
8. G. Delaizir, V. Viallet, A. Aboulaich, R. Bouchet, L. Tortet, V. Seznec, M. Morcrette,
J. M. Tarascon, P. Rozier, and M. Dollé, Advanced Functional Materials, 22(10),
2140 (2012).
9. A. Aboulaich, R. Bouchet, G. Delaizir, V. Seznec, L. Tortet, M. Morcrette, P. Rozier,
J. M. Tarascon, V. Viallet, and M. Dollé, Advanced Energy Materials, 1(2), 179
(2011).
10. M. Hara, H. Nakano, K. Dokko, S. Okuda, A. Kaeriyama, and K. Kanamura, Journal
of Power Sources, 189(1), 485 (2009).
11. K. Kanamura, N. Akutagawa, and K. Dokko, Journal of Power Sources, 146(1–2),
86 (2005).
12. M. Kotobuki, Y. Isshiki, H. Munakata, and K. Kanamura, Electrochimica acta, 55(22),
6892 (2010).
13. M. Kotobuki, Y. Suzuki, H. Munakata, K. Kanamura, Y. Sato, K. Yamamoto, and
T. Yoshida, Journal of The Electrochemical Society, 157(4), A493 (2010).
14. M. Kotobuki, Y. Suzuki, K. Kanamura, Y. Sato, K. Yamamoto, and T. Yoshida,
Journal of Power Sources, 196(22), 9815 (2011).
15. Z. Lin, Z. Liu, W. Fu, N. J. Dudney, and C. Liang, Angewandte Chemie International
Edition (2013).
16. P. Dutoit, U.S. Patent # 1,852,959, (1932).
17. I. C. Hoare, H. J. Hurst, W. I. Stuart, and T. J. White, Journal of the Chemical Society-Faraday Transactions I, 84, 3071 (1988).
18. T. Ozturk, E. Ertas, and O. Mert, Chemical reviews, 110(6), 3419 (2010).
19. O. Knacke, O. Kubaschewski, O. Hesselmann, and O. Editors, Thermochemical
Properties of Inorganic Substances, Springer-Verlag (1991).
20. I. Barin, Thermochemical data of pure substances, VCH, New York (1993).
21. T. A. Yersak, C. Stoldt, and S.-H. Lee, Journal of The Electrochemical Society,
160(8), A1009 (2013).
22. A. Hayashi, S. Hama, H. Morimoto, M. Tatsumisago, and T. Minami, Journal of the
American Ceramic Society, 84(2), 477 (2001).
23. J. Trevey, J. S. Jang, Y. S. Jung, C. R. Stoldt, and S.-H. Lee, Electrochemistry Communications, 11(9), 1830 (2009).
24. K. Takada, N. Aotani, K. Iwamoto, and S. Kondo, Solid State Ionics, 86-88(Part 2),
877 (1996).
25. D. J. Vischjager, A. A. Van Zomeren, J. Schoonman, I. Kontoulis, and B. C. H. Steele,
Solid state ionics, 40, 810 (1990).
26. G. Yunle, G. Fan, Q. Yitai, Z. Huagui, and Y. Ziping, Materials research bulletin,
37(6), 1101 (2002).
27. S. Boyanov, J. Bernardi, F. Gillot, L. Dupont, M. Womes, J. M. Tarascon,
L. Monconduit, and M. L. Doublet, Chemistry of materials, 18(15), 3531 (2006).
28. T. Ohtomo, F. Mizuno, A. Hayashi, K. Tadanaga, and M. Tatsumisago, Solid state
ionics, 176(31), 2349 (2005).
29. F. Mizuno, T. Ohtomo, A. Hayashi, K. Tadanaga, and M. Tatsumisago, Solid State
Ionics, 177(26–32), 2753 (2006).
30. M. Tachez, J.-P. Malugani, R. Mercier, and G. Robert, Solid State Ionics, 14(3), 181
(1984).
31. S.-B. Son, S. C. Kim, C. S. Kang, T. A. Yersak, Y.-C. Kim, C.-G. Lee, S.-H. Moon,
J. S. Cho, J.-T. Moon, K. H. Oh, and S.-H. Lee, Advanced Energy Materials, 2(10),
1226 (2012).
32. S.-B. Son, T. A. Yersak, D. M. Piper, S. C. Kim, C. S. Kang, J. S. Cho, S.-S. Suh,
Y.-U. Kim, K. H. Oh, and S.-H. Lee, Advanced Energy Materials (in press).
33. G. L. Evarts and G. T. Miller, U.S. Patent # 4,828,614 A, (1989).
34. R. Fong, J. R. Dahn, and C. H. W. Jones, Journal of The Electrochemical Society,
136(11), 3206 (1989).
35. B.-C. Kim, K. Takada, N. Ohta, Y. Seino, L. Zhang, H. Wada, and T. Sasaki, Solid
State Ionics, 176(31–34), 2383 (2005).
36. K. Takada, Y. Kitami, T. Inada, A. Kajiyama, M. Kouguchi, S. Kondo, M. Watanabe,
and M. Tabuchi, Journal of The Electrochemical Society, 148(10), A1085 (2001).
37. N. Machida, H. Yamamoto, and T. Shigematsu, Chemistry Letters, 33(1), 30 (2004).
Downloaded on 2016-03-06 to IP 130.203.136.75 address. Redistribution subject to ECS terms of use (see ecsdl.org/site/terms_use) unless CC License in place (see abstract).