Thickly and densely sintered Li3xLa2/3¹xTiO3 electrodes for the anode of Li-ion batteries

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<mark>DOI</mark> [https://doi.org/10.2109/jcersj2.24116](https://doi.org/10.2109/jcersj2.24116)
# JCS

<mark>FULL</mark> <mark>PAPER</mark>

## Thickly and densely sintered Li3xLa2/3¹xTiO3 electrodes for the anode of Li-ion batteries

Shinichi Takeno <sup>1</sup>, Ken Watanabe <sup>2,³</sup>, Koichi Suematsu <sup>2</sup> and Kengo Shimanoe <sup>2</sup>

1 Interdisciplinary Graduate School of Engineering Sciences, Kyushu University,
6–1 Kasuga Koen, Kasuga, Fukuoka 816–8580, Japan
2 Department of Advanced Materials Science and Engineering, Faculty of Engineering Sciences, Kyushu University,
6–1 Kasuga Koen, Kasuga, Fukuoka 816–8580, Japan

Japan

Thickly and densely sintered electrodes (TDSE) consisting of active materials can achieve highly capacitive Liion batteries and are one of the ideal electrode structures applicable for co-sintered-type solid-state batteries
based on oxide-based solid electrolytes. This study focused on Li3xLa2/3¹xTiO3 (LLTO) as the TDSE for the
anode. LLTO exhibits high Li-ion conductivity and a high capacity of 225 mAh g <sup>¹1</sup> with an operation potential
below 1 V (vs. Li <sup>+</sup> /Li). However, the electronic conductivity of LLTO is low (less than 10 <sup>¹8</sup> S cm <sup>¹1</sup> ), and the
improved electronic conductivity seems necessary. In this paper, we investigated the electrochemical properties
of LLTO sintered electrodes and improved the electronic conductivity of LLTO by Mn substitution for the Ti
site. LLTO shows a huge overpotential during initial Li insertion due to low electronic conductivity of 1.1 © 10 <sup>¹9</sup>

S cm <sup>¹1</sup>, resulting in extremely low capacity. On the other hand, Mn substitution enhances the electronic
conductivity, resulting in improved first-cycle charging properties.

Key-words : Li-ion batteries, Thickly and densely sintered electrodes (TDSE), Li3xLa2/3−xTiO3

[Received November 25, 2024; Accepted January 6, 2025; Published online February 14, 2025]

1. Introduction

Lithium-ion batteries (LIBs) are widely used as an
electric power source with high capacity and high output
density, making it possible for us to use mobile electronic
devices such as laptops and mobile phones. Moreover,
with growing environmental concerns and a push towards
a carbon-neutral society, LIBs have increasingly been
adopted for electric vehicles and stationary energy storage
systems. Thus, LIBs require higher capacity and energy
density. Since the capacity of electrodes depends on the
loading amount of active material in electrodes, various
strategies have been underway. One approach to increase
the amount of active material is to increase the thickness of
the electrode. In this approach, methods such as electrodes
using conductive agent/binder composite, <sup>1)</sup> designing bilayer electrodes using finite elements method and machine
learning, <sup>2)</sup> introduction of foam current collectors to shorten the electronic conduction path, <sup>3,4)</sup> electrodes made by
3D printing <sup>5)</sup>, composite electrodes using active materials
and solid electrolytes, <sup>6)</sup> electrode preparation by dry electrode coating process <sup>7)</sup> and phase-inversion method <sup>8)</sup> have
been investigated.

Another approach involves an increase in the volume
ratio of active material in the electrode, which has also been
underway. Park et al. reported an all-in-one multi-layered

³ Corresponding author: K. Watanabe; E-mail: watanabe.

ken.331@m.kyushu-u.ac.jp

cathodes-separator-anode monolith architecture for ultrathin flexible batteries, which achieved a high capacity of
44.5 mAh using the pouch cell with the thickness less than
1 mm. <sup>9)</sup> In general, electrodes consist not only of active
material but also of binders and conductive additives,
which limit the volume ratio of active material in the electrode. Thickly and densely sintered electrodes (TDSEs)
made by sintering only active material were proposed to
overcome this limitation. <sup>10)</sup> Since TDSEs are composed
solely of active material, TDSEs can achieve high capacity.
Additionally, TDSEs are produced by a high-temperature
sintering process. Accordingly, TDSEs are a suitable electrode structure for co-sintered type solid-state batteries <sup>11–14)</sup>

based on oxide solid electrolytes such as garnet family <sup>15–17)</sup>

and perovskite family. <sup>18–20)</sup>

The essential design for realizing TDSEs is a control of
the mixed Li-ionic and electronic conductivity of the
active materials because TDSE contains no conductive
additives. Recently, we have demonstrated that Li-ion conductivity through LiCoO2 TDSE is crucial for improving
the capacity. <sup>21)</sup> For instance, in the case of LiCoO2 TDSE
with 180 ¯m in thickness and 96 % relative density, Li-ion
conductivity of more than 10 <sup>¹5</sup> S cm <sup>¹1</sup> is needed to
achieve the theoretical capacity.

This paper focuses on Li3xLa2/3¹xTiO3 (LLTO), <sup>18)</sup> which
exhibits a high bulk Li-ion conductivity of 10 <sup>¹3</sup> S cm <sup>¹1</sup>, as
TDSE for anode. LLTO has a perovskite structure and has
been investigated as a candidate for oxide-based solid
electrolytes due to its high Li-ion conductivity. <sup>22,23)</sup> Re

©2025 The Ceramic Society of Japan

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Journal of the Ceramic Society of Japan (2025), Advance Publication by J-stage JCS-Japan

cently, some studies have demonstrated that LLTO works
as an active material. <sup>24,25)</sup> Lu et al. reported that electrodes
using LLTO powder achieved a high capacity of 225
mAh g <sup>¹1</sup> and low operating potential under 1 V (vs. Li <sup>+</sup> /
Li). <sup>25)</sup> Moreover, the authors also reported a high capability of nearly 100 mAh g <sup>¹1</sup> at 10C and superior capacity
retention of 79 % over 3000 cycles. Compared with
Li4Ti5O12 (LTO), <sup>26)</sup> LLTO exhibits higher capacity, lower
operating voltage, and higher Li-ion conductivity, which is
expected to be a promising anode material for TDSE.
However, to our knowledge, LLTO TDSE has not been
reported yet, and the explicit material design has not been
established.

Regarding Li-ion conduction, LLTO is an excellent
material, but its electronic conductivity is extremely low
(less than 10 <sup>¹8</sup> S cm <sup>¹1</sup> ). Commonly, LLTO becomes an
electronic conductor when it contacts Li metal due to the
reduction of Ti <sup>4+</sup> to Ti <sup>3+</sup> . <sup>18)</sup> This means that Li insertion
into LLTO causes electronic conduction. In other words, at
the initial stage of the Li insertion reaction, the reaction
site should be limited around the current collector due to
the low electronic conduction of LLTO. Thus, in the case
of LLTO TDSE, controlling electronic conduction through
LLTO seems key for improving the initial Li insertion
reaction.

In this paper, we first reveal the charge–discharge property for LLTO TDSE as the anode for LIBs. Then, we
demonstrate the effect of Mn substitution for the Ti site,
which has been reported as an efficient method to improve
the electronic conductivity, <sup>27)</sup> for LLTO on the charge–
discharge properties.

2. Experimental

2.1 Material preparation
Li0.33La0.557TiO3 (x = 0.11 in Li3xLa2/3¹xTiO3) and
Li0.33La0.557+1/3xTi1¹xMnxO3 (x = 0–0.075) were synthesized by solid-state reaction. Lithium carbonate (Li2CO3,
99.99 %, Rara metallic Co., Japan), Titanium oxide (TiO2,
99.8 %, Sigma-Aldrich Co., U.S.) and Lanthanum(III)
hydroxide [La(OH)3, 99.9 %, Sigma-Aldrich Co., U.S.],
manganese oxide(IV) (MnO2, 99.5 %, Wako Co., Japan)
were used. Starting materials were weighted to obtain the
desired composition and mixed using a planetary ball mill
at 450 rpm for 15 h with isopropanol as the solvent. After
ball milling, the solvent was evaporated to dryness, and
the mixture was grounded with a mortal. The obtained
precursor was calcinated at 800 °C for 4 h. The calcined
powder was grounded, press-formed into a disk shape, and
pressed again by cold isostatic pressing. The obtained disks
were sintered at 1100 °C for 15 h. While sintering, the disks
were covered with calcined powder to prevent contamination of other elements and evaporation of Li during sintering. Table S1 shows the relative density of LLTO and
Mn-substituted LLTOs. All samples were densified well.

2.2 Material characterization
The crystal structure of sintered disks was evaluated by
X-ray diffraction (XRD: MiniFlex600, RIGAKU, Japan)

with Cu K¡ as an X-ray source. Structural parameters
were calculated by Rietveld refinement using PDXL2
(RIGAKU, Japan). Microstructure observation was conducted using a scanning transmission electron microscope
(JCM-7000, JEOL Ltd., Japan).

2.3 Electrochemical property
The electronic and Li-ionic conductivities for the sintered samples were evaluated by the DC polarization method and AC impedance spectroscopy, respectively. First, to
remove the as-sintered surface and adjust the thickness, the
sintered disk was polished up to about 480 ¯m in thickness
with lapping film sheets (#320–#16000, 3M, U.S.). After
polishing, the Ag electrode was deposited on both sides of
the polished disk via sputtering. Then, samples were set
in the hand-made cell shown in Fig. S1(a) in the Ar-filled
grove box. DC polarization measurement was performed
using squidstat <sup>TM</sup> Plus (Admiral Instruments, U.S.) with
galvanostatic mode. AC impedance spectroscopy was conducted using VSP-300 (Biologic, France) with an amptitude of 10 mV and a frequency range of 7 MHz to 1 Hz.

The electrode performance of Li0.33La0.557TiO3 TDSE
for an anode of LIBs was evaluated using a half-cell with
the liquid electrolyte and Li metal as a reference electrode.
First, LLTO TDSE was polished up to 180 ¯m, and the Pt
current collector was sputtered on one side of the disk.
Then, samples were transferred to an Ar-filled grove box.
Then, the half-cell shown in Fig. S1(b) was assembled.
The charge–discharge performance of the half-cell was
evaluated by galvanostatic charging–discharging with a
constant current at 0.019C using HJ1001SD8 (Hokuto
Denko Co., Ltd., Japan). The theoretical capacity was calculated based on previous research, which reported that Li
is inserted into O4 square window sites located between
Li-Li atoms, <sup>21)</sup> resulting in 323 mAh g <sup>¹1</sup> . The upper and
lower cut-off voltages were set at 3.0 and 0 V (vs. Li <sup>+</sup> /Li).

3. Results and discussion

3.1 LLTO TDSE
First, the crystal structure and microstructure were characterized to confirm the quality of the fabricated LLTO.
Figure 1(a) shows the XRD pattern of Li0.33La0.557TiO3
after sintering. All diffraction peaks can be assigned to
tetragonal Li0.33La0.557TiO3 with space group P4/mmm.
However, the SEM-EDS mapping shown in Fig. 1(b)
suggests a small amount of Ti aggregation. Jonderian et al.
reported that obtaining the pure LLTO phase is too difficult, and impurity phases such as TiO2 and Li2Ti3O7
always coexist. Therefore, the obtained LLTO is suitable
for TDSE in terms of crystal structure and microstructure.

Figure 2(a) shows the Nyquist plot of Li0.33La0.557TiO3
at 25 °C. There are two typical semicircles in the frequency
range from 7 MHz to 300 Hz. The equivalent circuit shown
in Fig. 2(a) was used to estimate three resistance components: R1, R2, and R3. R1, R2, and R3 are assigned to the
bulk, grain boundary, and interfacial resistance. The estimated bulk Li-ion conductivity was 1.0 © 10 <sup>¹3</sup> S cm <sup>¹1</sup>,
two orders of magnitude greater than the grain boundary of

JCS-Japan Takeno et al.: Thickly and densely sintered Li3xLa2/3−xTiO3 electrodes for the anode of Li-ion batteries

a

a b

b

c d

Fig. 1. (a) XRD pattern of Li0.33La0.557TiO3. (b) SEM image
of Li0.33La0.557TiO3 sintered disk and elemental mappings of La
and Ti.

a

b

Fig. 2. (a) The complex impedance spectra of Li0.33La0.557TiO3
sintered disk and an equivalent circuit for fitting. (b) Electron
conductivity and Li-ion conductivity of Li0.33La0.557TiO3 sintered
disk.

2.0 © 10 <sup>¹5</sup> S cm <sup>¹1</sup> . Figure 2(b) shows the total Li-ion and
electronic conductivity of Li0.33La0.557TiO3. The obtained
electronic conductivity of 1.1 © 10 <sup>¹9</sup> S cm <sup>¹1</sup> was much
lower than the total Li-ion conductivity of Li0.33La0.557TiO3 of 1.9 © 10 <sup>¹5</sup> S cm <sup>¹1</sup> . The obtained values are comparable with those previously reported. <sup>19)</sup>

Figure 3(a) shows charge–discharge curves of the halfcell using Li0.33La0.557TiO3 TDSE at 0.53 mA cm <sup>¹2</sup> . The
diameter of the LLTO sintered disk used in the charging/
discharging test in Fig. 3(a) was 7.78 mm. At the first
charging, a huge overpotential was observed, and the
capacity gradually increased with an increase in the cycle
number. After charge–discharge test, the formation of
cracks was observed, indicating that the penetration of the
liquid electrolyte through cracks may enhance the capacity

Fig. 3. The charge–discharge curves for sintered disks of
Li0.33La0.557TiO3 sintered disk at (a) 0.53 mA cm <sup>¹2</sup>, (b) 0.17
mA cm <sup>¹2</sup>, (c) 0.06 mA cm <sup>¹2</sup> . (d) Correlation between current
density and areal capacity.

as the cycle number increased. However, the capacity at
the 10th cycle was less than 70 mAh g <sup>¹1</sup>, much lower than
the previously reported value for Li0.33La0.557TiO3 powder,
225 mAh g <sup>¹1</sup> . <sup>25)</sup> This means that the electrode reaction of
LLTO TDSE is different from that of the general powderbased electrode. The current density dependence of the
capacity was investigated to understand the electrode property for LLTO TDSE in detail. Figures 3(b) and 3(c) show
charge–discharge curves at 0.17 and 0.06 mA cm <sup>¹2</sup>, respectively. The diameter of the LLTO sintered disk used in
the charging/discharging test in Figs. 3(b) and 3(c) was
7.77 and 7.72 mm, respectively. As the current density decreased, the overpotential at first charging lowered, and the
capacity gradually increased. Figure 3(d) summarizes the
dependence between current density and discharge capacity. Even at a current density of 0.06 mA cm <sup>¹2</sup>, the discharge capacity was 81 mAh g <sup>¹1</sup>, which seems saturated.
In addition, the capacity above 1 V (vs. Li <sup>+</sup> /Li) was ³50
mAh g <sup>¹1</sup> and shows a good agreement with the previous
report, indicating that the electrode reaction below 1 V (vs.
Li <sup>+</sup> /Li) of TDSE differs from the normal electrode. Here,
we are considering two possible reasons for the lower
capacity. One is the suppression of phase transformation.
During the Li insertion process into LLTO, the phase
transformation from tetragonal to pseudo-cubic occurs. <sup>25)</sup>

This phase transformation causes the volume change of
LLTO. In the case of TDSE, grains are tightly connected
and there is no free space to allow the volume expansion,
although the normal electrode has enough free space for
volume change in LLTO particle. This suppression of
phase transformation caused by dense structure for TDSE
may prevent the Li insertion reaction. The other is that the
discharge capacity for LLTO TDSE may reach the theoretical capacity. This means that the structural difference
between the normal electrode using Li0.33La0.557TiO3 powder and TDSE causes a big difference in the capacity.
According to a previous report, <sup>25)</sup> the authors fabricated

Journal of the Ceramic Society of Japan (2025), Advance Publication by J-stage JCS-Japan

### d

Fig. 4. Photo images of Li0.33La0.557TiO3 (a) before and after charging to (b) 0.03 mAh g <sup>¹1</sup> and (c) 5 mAh g <sup>¹1</sup> .
(d) The schematic diagram of Li insertion reaction for Li0.33La0.557TiO3 TDSE at the initial stage.

the electrode by mixing LLTO powder with carbon material as a conductive additive. It was reported that carbon
black can intercalate/deintercalated Li <sup>+</sup> under 1.5 V (vs.
Li <sup>+</sup> /Li) and exhibit capacity. <sup>28)</sup> Thus, we believe that the
capacity of the normal powder-based electrode contains
the capacity of not only Li0.33La0.557TiO3 but also carbon
black, and the actual capacity of Li0.33La0.557TiO3 is estimated to be approximately 80 mAh g <sup>¹1</sup> corresponding to
the reduction of 52 % Ti <sup>4+</sup> to Ti <sup>3+</sup> . However, further investigation is needed to clear the reason.

To reveal the origin of overpotential seen at the first
charge, we investigated the reaction site of LLTO TDSE.
Figures 4(a)–4(c) shows the photographs of Li0.33La0.557TiO3 before and after charging to 0.03 mAh g <sup>¹1</sup> (corresponding to 1 min) and 5 mAh g <sup>¹1</sup> . After charging to 5
mAh g <sup>¹1</sup>, the color of Li0.33La0.557TiO3 TDSE turned black

[Fig. 4(c)]. According to the previous report, <sup>29,30)</sup> this
color change is attributed to the reduction of Ti <sup>4+</sup> with an
increase in electronic conductivity to 1.5 © 10 <sup>¹4</sup> S cm <sup>¹1</sup> . It
is noted that, after charging to 0.03 mAh g <sup>¹1</sup>, the color of
only the outer part of the LLTO TDSE turned black, indicating the charging reaction occurred from outside the
sintered disk. In addition, the Pt current collector is thin
film (³60 nm) and there are pores. Thus, not only the edge
but also the current collector side may play as the initial
reaction site. Based on this consideration, we propose the
reaction mechanism for LLTO TDSE at the first charging
process, as shown in Fig. 4(d). Firstly, since the electronic
conductivity of Li0.33La0.557TiO3 was extremely low, electrons can provide from only the current collector; the reaction occurred at the triple-phase boundary between LLTO,
electrolyte, and the current collector, where Ti <sup>4+</sup> reduction
phase forms around this interface. This limited reaction

site causes the localization of currents in this area, resulting in high overpotential. During the charging process, the
formed Ti <sup>3+</sup> enhances the electronic conduction through
LLTO, and the reaction site gradually increases due to the
chemical diffusion of Li through LLTO. Here, the outer
part can directly contact to the liquid electrolyte. On the
other hand, the inside of LLTO Li migration through the
LLTO is slower than that of the outside, because the Li ion
conductivity of LLTO is much lower than that of the liquid
electrolyte. As a result, the Li insertion reaction proceeds
homogeneously in the diameter direction. Finally, all surfaces of LLTO TDSE become the reaction surface, and the
overpotential caused by low electronic conductivity completely disappears. Thus, the high overpotential at the initial stage for the Li insertion may be improved by enhancing the electronic conductivity of LLTO TDSE. So far, we
investigated the effect of Mn substitution for Ti to improve
the electronic conductivity and demonstrate these electrode properties.

3.2 Mn substitution for Ti site to enhance the
electronic conductivity
To enhance electronic conductivity, we investigated Mn
substitution for Ti site in Li0.33La0.557+1/3xTi1¹xMnxO3.
Here, to compensate for the Mn <sup>3+</sup>, the amount of La <sup>3+</sup> was
controlled. Figures 5(a) and 5(b) show the XRD patterns
of Mn-substituted LLTO and the correlation between the
amount of Mn substitution and lattice constants (a and c)
calculated by Rietveld refinement. Although the perovskite
peak can be observed in all XRD patterns, the peak intensity of Li2La2Ti3O10 as the impurity phase increases with
an increase in Mn substitution amount. Additionally, c
increases as the Mn substitution amount increases despite

JCS-Japan Takeno et al.: Thickly and densely sintered Li3xLa2/3−xTiO3 electrodes for the anode of Li-ion batteries

a

b

Fig. 5. (a) XRD patterns of Li0.33La0.557+1/3xTi1¹xMnxO3 and
(b) the correlation between the amount of Mn substitution and
lattice constants.

a

b

Fig. 6. (a) The Nyquist plots of Li0.33La0.557+1/3xTi1¹xMnxO3
TDSEs at 25 °C. (b) The correlation between the amount of
Mn substitution and electron/Li-ion conductivity of Li0.33La0.557+1/3xTi1¹xMnxO3 sintered disks.

of no change in a. This change may be attributed to be
Jahn–Teller effect of substituted Mn <sup>3+</sup> at the B-site, indicating that Ti has been partially replaced by Mn in LLTO.

Figures 6(a) and 6(b) show the Nyquist plots of Mnsubstituted LLTO and the correlation between the amount
of Mn substitution and Li-ionic/electronic conductivity.
In the Nyquist plots, two semicircles are corresponding
to bulk and grain boundary resistance. According to the
equivalent circuit shown in Fig. 2(a), total Li-ion conductivities were estimated. As shown in Fig. 6(b), Li-ion
conductivity decreased to 2.2 © 10 <sup>¹6</sup> S cm <sup>¹1</sup> as the Mn

Fig. 7. The charge–discharge curves for sintered disks of Li0.33La0.557+1/3xTi1¹xMnxO3 sintered disks (a) x = 0.025, (b) x =
0.05, (c) x = 0.075, (d) correlation between the amount of Mn
substitution and the highest discharge capacity through 10 cycles.

substitution increased. On the other hand, the electronic
conductivity increased with an increase in Mn substitution, and the highest electrical conductivity for x = 0.075
of 7.1 © 10 <sup>¹8</sup> S cm <sup>¹1</sup> was obtained. These results show a
good agreement with the previous report. <sup>28)</sup>

A charge–discharge test was conducted to reveal the effect of Mn-substitution on electrode property. Figures 7(a)–
7(c) shows the charge–discharge curves of Mn-substituted
LLTO. The diameter of LLTO sintered disk used in the
charging/discharging test was 7.78, 7.83 and 7.93 mm, respectively. Although the compositions with x = 0.025 and
0.05 exhibited a low capacity of less than 10 mAh g <sup>¹1</sup> in the
first cycle, x = 0.075 exhibits the highest capacity of 75
mAh g <sup>¹1</sup> . This may be attributed to an increase in electronic
conductivity. As shown in Fig. 4(d), the charging reaction
occurred around the triple-phase boundary in LLTO sintered anode immediately after the start of charging due to
the low electronic conductivity of LLTO without Mn substitution. Consequently, it was shown that enhanced electronic conductivity improved the first Li insertion reaction
for LLTO TDSEs.

Figure 7(d) shows the relationship between the Mn
substitution amount and the highest discharge capacity
through 10 cycles. The discharge capacity increases with
an increase in the Mn substitution amount, indicating that
the Mn substitution effectively improves the discharge
capacity of LLTO TDSE. The improved electronic conductivity by Mn substitution may enhance the capacity.
However, the new plateau can be observed when the Mn
substitution amount increases. Figure 8 shows the dQ/dV
curves for LLTO and Mn-substituted LLTO (x = 0.075).
Although the peak intensity for Mn-substituted LLTO
above 1 V decreased, a new peak around 0.7 and 0.4 V was
observed. This new redox peak may be assigned to the
Ti <sup>4+</sup> redox in Li2La2Ti3O10. Thus, not only the change in
bulk property by Mn substitution for LLTO but also impurity phases like Li2La2Ti3O10 would affect the enhanced

Journal of the Ceramic Society of Japan (2025), Advance Publication by J-stage JCS-Japan

Fig. 8. The dQ/dV curves for LLTO and Mn-substituted LLTO.

discharge capacity. The detailed mechanisms will be
reported in the future.

4. Conclusion

In this study, we investigated the electrochemical properties of the LLTO thickly and densely sintered electrode
(TDSE) as the anode for Li-ion batteries. We found that
the LLTO TDSE exhibited high overpotential and low
capacity during the first cycle charging, attributed to low
electronic conductivity of 1.1 © 10 <sup>¹9</sup> S cm <sup>¹1</sup> . Furthermore, we investigated the effects of Mn substitution on
enhancing the electronic conductivity of LLTO. Mn substitution increased electronic conductivity to 7.1 © 10 <sup>¹8</sup>

S cm <sup>¹1</sup> despite a decrease in Li-ion conductivity, and this
enhanced electronic conductivity improved the overpotential and capacity during the first cycle. In addition, we have
demonstrated that Mn-substitution improved the discharge
capacity. Thus, it was found that controlling the electronic
conductivity with the partial substitution of other elements
effectively improves the initial Li insertion reaction for
LLTO TDSEs.

Acknowledgments This work was supported by Japan
Science and Technology (JST), the Advanced Low Carbon
Technology Research and Development Program, Specially
Promoted Research for Innovative Next Generation Battery
(ALCA-SPRING) project, Grant Number JPMJAL1301,
Green Technologies of Excellence (GteX) Program Japan,
Grant number JPMJGX23S22, the establishment of university
fellowships towards the creation of science technology innovation, Grant Number JPMJFS2132, and JSPS KAKENHI
Grant Number 22K04739, 24K21811, and 24K21222.

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