U.S. patent application number 16/407352 was filed with the patent office on 2019-12-05 for cathode, all-solid-state battery and methods for producing them.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. The applicant listed for this patent is TOYOTA JIDOSHA KABUSHIKI KAISHA. Invention is credited to Nariaki MIKI.
Application Number | 20190372103 16/407352 |
Document ID | / |
Family ID | 66589465 |
Filed Date | 2019-12-05 |
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United States Patent
Application |
20190372103 |
Kind Code |
A1 |
MIKI; Nariaki |
December 5, 2019 |
CATHODE, ALL-SOLID-STATE BATTERY AND METHODS FOR PRODUCING THEM
Abstract
Provided is a cathode that is configured to decrease battery
resistance when it is used in an all-solid-state battery, and a
method for producing the cathode. Disclosed is a cathode comprising
a cathode layer for all-solid-state batteries, wherein the cathode
layer contains cathode active material particles and solid
electrolyte particles; wherein at least one of the cathode active
material particles and the solid electrolyte particles contain a
phosphorus element; and wherein, in a photoelectron spectrum by
X-ray photoelectron spectroscopy measurement of the cathode layer,
a P peak intensity ratio (A/B), which is derived from the
phosphorus element, of a signal intensity A at a binding energy of
131.6 eV to a signal intensity B at a binding energy of 133.1 eV,
is larger than 0.58.
Inventors: |
MIKI; Nariaki; (Susono-shi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TOYOTA JIDOSHA KABUSHIKI KAISHA |
Toyota-shi |
|
JP |
|
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
Toyota-shi
JP
|
Family ID: |
66589465 |
Appl. No.: |
16/407352 |
Filed: |
May 9, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 4/131 20130101;
H01M 10/0585 20130101; H01M 4/485 20130101; H01M 10/0525 20130101;
H01M 4/5825 20130101; H01M 4/1397 20130101; H01M 2300/0068
20130101; H01M 4/62 20130101; H01M 10/058 20130101; H01M 4/136
20130101; H01M 4/5805 20130101; H01M 4/1391 20130101; H01M 4/362
20130101; H01M 4/505 20130101; H01M 2300/0071 20130101; H01M
2004/028 20130101; H01M 4/525 20130101; H01M 10/0562 20130101 |
International
Class: |
H01M 4/36 20060101
H01M004/36; H01M 10/0585 20060101 H01M010/0585; H01M 10/0562
20060101 H01M010/0562; H01M 4/62 20060101 H01M004/62 |
Foreign Application Data
Date |
Code |
Application Number |
May 29, 2018 |
JP |
2018-102285 |
Claims
1. A cathode comprising a cathode layer for all-solid-state
batteries, wherein the cathode layer contains cathode active
material particles and solid electrolyte particles; wherein at
least one of the cathode active material particles and the solid
electrolyte particles contain a phosphorus element; and wherein, in
a photoelectron spectrum by X-ray photoelectron spectroscopy
measurement of the cathode layer, a P peak intensity ratio (A/B),
which is derived from the phosphorus element, of a signal intensity
A at a binding energy of 131.6 eV to a signal intensity B at a
binding energy of 133.1 eV, is larger than 0.58.
2. The cathode according to claim 1, wherein the cathode layer
contains composite active material particles comprising the cathode
active material particles and a lithium ion conducting oxide, the
lithium ion conducting oxide coating at least part of the surface
of the cathode active material particles.
3. The cathode according to claim 2, wherein the lithium ion
conducting oxide is at least one selected from the group consisting
of lithium niobate, lithium titanate, lithium lanthanum zirconate,
lithium tantalate and lithium tungstate.
4. The cathode according to claim 1, wherein the solid electrolyte
particles are sulfide-based solid electrolyte particles.
5. The cathode according to claim 1, wherein a moisture content of
the cathode active material particles is 70 ppm or less.
6. An all-solid-state battery comprising: a cathode comprising a
cathode layer, an anode comprising an anode layer, and a solid
electrolyte layer disposed between the cathode layer and the anode
layer, wherein the cathode is the cathode defined by claim 1.
7. A method for producing a cathode comprising a cathode layer for
all-solid-state batteries, the method comprising: preparing cathode
active material particles; vacuum-drying the cathode active
material particles at a temperature of 120.degree. C. or more and
300.degree. C. or less for one hour or more; mixing the cathode
active material particles with solid electrolyte particles to
obtain a cathode mix; and forming the cathode mix to obtain the
cathode layer, wherein at least one of the cathode active material
particles and the solid electrolyte particles contain a phosphorus
element, and wherein, in a photoelectron spectrum by a X-ray
photoelectron spectroscopy measurement of the cathode layer, a P
peak intensity ratio (A/B), which is derived from the phosphorus
element, of a signal intensity A at a binding energy of 131.6 eV to
a signal intensity B at a binding energy of 133.1 eV, is larger
than 0.58.
8. The method for producing the cathode according to claim 7,
wherein, in the preparing, composite active material particles
comprising the cathode active material particles and a lithium ion
conducting oxide, the lithium ion conducting oxide coating at least
part of the surface of the cathode active material particles, are
prepared.
9. The method for producing the cathode according to claim 8,
wherein, in the preparing, a precursor of the composite active
material particles is obtained by drying, on the surface of the
cathode active material particles, a peroxo complex aqueous
solution containing an element that will compose the lithium ion
conducting oxide, and the composite active material particles are
obtained by sintering the precursor.
10. The method for producing the cathode according to claim 7,
wherein the solid electrolyte particles are sulfide-based solid
electrolyte particles.
11. A method for producing an all-solid-state battery comprising: a
cathode comprising a cathode layer, an anode comprising an anode
layer, and a solid electrolyte layer disposed between the cathode
layer and the anode layer, wherein the cathode is a cathode
produced by the production method defined by claim 7.
Description
TECHNICAL FIELD
[0001] The disclosure relates to a cathode, an all-solid-state
battery and methods for producing them.
BACKGROUND
[0002] In recent years, with the rapid spread of IT and
communication devices such as personal computers, camcorders and
cellular phones, great importance has been attached to the
development of batteries that can be used as the power source of
such devices. In the automobile industry, etc., high-power and
high-capacity batteries for electric vehicles and hybrid vehicles
are under development.
[0003] Of all-solid-state batteries, an all-solid-state lithium ion
battery has attracted attention, due to its high energy density
resulting from the use of a battery reaction accompanied by lithium
ion transfer, and due to the use of a solid electrolyte as the
electrolyte present between the cathode and the anode, in place of
a liquid electrolyte containing an organic solvent.
[0004] Patent Literature 1 discloses that composite active material
particles are obtained by coating the surface of a cathode active
material that is used in all-solid-state lithium ion batteries,
with a lithium ion conducting oxide.
[0005] Patent Literature 1: International Publication No.
WO2007/004590
[0006] Conventional all-solid-state batteries cannot be said to
have sufficient performance, since the battery resistance of them
remains high.
SUMMARY
[0007] In light of the above circumstance, an object of the
disclosed embodiments is to provide a cathode that is configured to
decrease battery resistance when it is used in an all-solid-state
battery, and a method for producing the cathode.
[0008] In a first embodiment, there is provided a cathode
comprising a cathode layer for all-solid-state batteries,
[0009] wherein the cathode layer contains cathode active material
particles and solid electrolyte particles;
[0010] wherein at least one of the cathode active material
particles and the solid electrolyte particles contain a phosphorus
element; and
[0011] wherein, in a photoelectron spectrum by X-ray photoelectron
spectroscopy measurement of the cathode layer, a P peak intensity
ratio (A/B), which is derived from the phosphorus element, of a
signal intensity A at a binding energy of 131.6 eV to a signal
intensity B at a binding energy of 133.1 eV, is larger than
0.58.
[0012] The cathode layer may contain composite active material
particles comprising the cathode active material particles and a
lithium ion conducting oxide, the lithium ion conducting oxide
coating at least part of the surface of the cathode active material
particles.
[0013] The lithium ion conducting oxide may be at least one
selected from the group consisting of lithium niobate, lithium
titanate, lithium lanthanum zirconate, lithium tantalate and
lithium tungstate.
[0014] The solid electrolyte particles may be sulfide-based solid
electrolyte particles.
[0015] A moisture content of the cathode active material particles
may be 70 ppm or less.
[0016] In another embodiment, there is provided an all-solid-state
battery comprising:
[0017] a cathode containing a cathode layer,
[0018] an anode containing an anode layer, and
[0019] a solid electrolyte layer disposed between the cathode layer
and the anode layer,
[0020] wherein the cathode is the above-described cathode.
[0021] In another embodiment, there is provided a method for
producing a cathode comprising a cathode layer for all-solid-state
batteries, the method comprising:
[0022] preparing cathode active material particles;
[0023] vacuum-drying the cathode active material particles at a
temperature of 120.degree. C. or more and 300.degree. C. or less
for one hour or more;
[0024] mixing the cathode active material particles with solid
electrolyte particles to obtain a cathode mix; and
[0025] forming the cathode mix to obtain the cathode layer,
[0026] wherein at least one of the cathode active material
particles and the solid electrolyte particles contain a phosphorus
element, and
[0027] wherein, in a photoelectron spectrum by a X-ray
photoelectron spectroscopy measurement of the cathode layer, a P
peak intensity ratio (A/B), which is derived from the phosphorus
element, of a signal intensity A at a binding energy of 131.6 eV to
a signal intensity B at a binding energy of 133.1 eV, is larger
than 0.58.
[0028] In the preparing, composite active material particles
comprising the cathode active material particles and a lithium ion
conducting oxide, the lithium ion conducting oxide coating at least
part of the surface of the cathode active material particles, may
be prepared.
[0029] In the preparing, a precursor of the composite active
material particles may be obtained by drying, on the surface of the
cathode active material particles, a peroxo complex aqueous
solution containing an element that will compose the lithium ion
conducting oxide, and the composite active material particles may
be obtained by sintering the precursor.
[0030] The solid electrolyte particles may be sulfide-based solid
electrolyte particles.
[0031] In another embodiment, there is provided a method for
producing an all-solid-state battery comprising:
[0032] a cathode comprising a cathode layer,
[0033] an anode comprising an anode layer, and
[0034] a solid electrolyte layer disposed between the cathode layer
and the anode layer,
[0035] wherein the cathode is a cathode produced by the
above-described production method.
[0036] An all-solid-state battery having low battery resistance can
be obtained by using the cathode of the disclosed embodiments in an
all-solid-state battery.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] In the accompanying drawings,
[0038] FIG. 1 is a schematic sectional view of an example of the
all-solid-state battery of the disclosed embodiments;
[0039] FIG. 2 shows a photoelectron spectrum of Example 1; and
[0040] FIG. 3 shows a photoelectron spectrum of Comparative Example
1.
DETAILED DESCRIPTION
[0041] The cathode according to the disclosed embodiments is a
cathode comprising a cathode layer for all-solid-state
batteries,
[0042] wherein the cathode layer contains cathode active material
particles and solid electrolyte particles;
[0043] wherein at least one of the cathode active material
particles and the solid electrolyte particles contain a phosphorus
element; and
[0044] wherein, in a photoelectron spectrum by X-ray photoelectron
spectroscopy measurement of the cathode layer, a P peak intensity
ratio (A/B), which is derived from the phosphorus element, of a
signal intensity A at a binding energy of 131.6 eV to a signal
intensity B at a binding energy of 133.1 eV, is larger than
0.58.
[0045] It was thought that a factor that increases the battery
resistance of an all-solid-state battery is oxidation of the
cathode active material particles contained in the cathode layer
and/or oxidation of the solid electrolyte particles. Then, the
cathode that can decrease the battery resistance of an
all-solid-state battery, was found by focusing on the state of the
phosphorus element contained in the cathode active material
particles in the cathode layer and/or the phosphorus element
contained in the solid electrolyte particles.
1. Cathode
[0046] The cathode comprises at least the cathode layer. Also, the
cathode may comprise a cathode current collector that is
electrically connected to the cathode layer.
[0047] The cathode layer contains cathode active material particles
and solid electrolyte particles. At least one of the cathode active
material particles and the solid electrolyte particles contain a
phosphorus element, and the solid electrolyte particles may contain
a phosphorus element.
[0048] The cathode layer may contain an electroconductive material
and/or a binder as optional components.
[Cathode Active Material Particles]
[0049] The type of the cathode active material particles is not
particularly limited. The cathode active material particles can be
any type of particles composed of a material that is usable as an
active material for all-solid-state batteries. When an
all-solid-state battery is a lithium ion battery, as the material
for the cathode active material particles, examples include, but
are not limited to, LiCoO.sub.2, LiNi.sub.xCo.sub.1-xO.sub.2
(0<x<1), LiNi.sub.1/3Co.sub.1/3Mn.sub.1/3O.sub.2,
LiMnO.sub.2, different element-substituted Li--Mn spinels (such as
LiMn.sub.1.5Ni.sub.0.5O.sub.4, LiMn.sub.1.5Al.sub.0.5O.sub.4,
LiMn.sub.1.5Mg.sub.0.5O.sub.4, LiMn.sub.1.5Co.sub.0.5O.sub.4,
LiMn.sub.1.5Fe.sub.0.5O.sub.4 and LiMn.sub.1.5Zn.sub.0.5O.sub.4),
lithium titanates (such as Li.sub.4Ti.sub.5O.sub.12), lithium metal
phosphates (such as LiFePO.sub.4, LiMnPO.sub.4, LiCoPO.sub.4 and
LiNiPO.sub.4), transition metal oxides (such as V.sub.2O.sub.5 and
MoO.sub.3), TiS.sub.2, LiCoN, Si, SiO.sub.2, Li.sub.2SiO.sub.3,
Li.sub.4SiO.sub.4, lithium alloys (such as LiSn, LiSi, LiAl, LiGe,
LiSb and LiP), and lithium storage intermetallic compounds (such as
Mg.sub.2Sn, Mg.sub.2Ge, Mg.sub.2Sb and Cu.sub.3Sb).
[0050] The cathode active material particles may be particles of a
lithium-containing composite oxide selected from LiCoO.sub.2,
LiNi.sub.xCo.sub.1-xO.sub.2 (0<x<1),
LiNi.sub.1/3Co.sub.1/3Mn.sub.1/3O.sub.2, LiMnO.sub.2, different
element-substituted Li--Mn spinels and lithium metal
phosphates.
[0051] The form of the cathode active material particles is not
particularly limited. The primary particle diameter of the cathode
active material particles may be 1 nm or more and 100 .mu.m or
less. The lower limit of the primary particle diameter may be 10 nm
or more, may be 100 nm or more, or may be 500 nm or more. The upper
limit of the primary particle diameter may be 30 .mu.m or less, or
may be 3 .mu.m or less. The cathode active material particles may
be secondary particles formed by aggregation of the primary
particles.
[Composite Active Material Particles]
[0052] In the cathode layer, the composite active material
particles may be contained as a cathode active material, from the
point of view that formation of a resistive layer by reaction
between the cathode active material particles and the solid
electrolyte particles, can be suppressed. In the disclosed
embodiments, the given peak intensity ratio, which is obtained by
XPS measurement of the cathode layer, is determined as a measure to
judge whether the cathode active material particles contained in
the cathode layer and/or the solid electrolyte particles are kept
in an unoxidized state or not. Accordingly, even if the cathode
active material contained in the cathode layer is the composite
active material particles, it does not interfere with the
calculation of the peak intensity ratio of the cathode layer.
[0053] The composite active material particles comprise the cathode
active material particles and a coating layer coating at least part
of the surface of the cathode active material particles and
containing the lithium ion conducting oxide.
[0054] The content of the composite active material particles in
the cathode layer is not particularly limited. For example, it may
be 40 mass % or more and 99 mass % or less.
[0055] The method for coating the surface of the cathode active
material particles with the lithium ion conducting oxide, is not
particularly limited. As the method, examples include, but are not
limited to, a sputtering method, a sol-gel method, an electrostatic
spraying method, a ball milling method and the following method: in
the air environment, the cathode active material particles are
coated with the lithium ion conducting oxide by use of a
tumbling/fluidizing coating device (manufactured by Powrex
Corporation), and the coated particles are sintered in the air
environment.
[Lithium Ion Conducting Oxide]
[0056] The lithium ion conducting oxide has lithium ion
conductivity and functions as a protection material for suppressing
reaction between the cathode active material particles and the
below-described solid electrolyte particles. That is, the lithium
ion conducting oxide is a material having lithium ion conductivity
and, compared to the cathode active material particles, relatively
low reactivity to the solid electrolyte particles. As long as the
lithium ion conducting oxide has such a function, desired effects
can be exerted regardless of the type of the lithium ion conducting
oxide.
[0057] As the lithium ion conducting oxide, examples include, but
are not limited to, a composite oxide containing a lithium element
and a metal element. More specifically, examples include, but are
not limited to, lithium niobate, lithium titanate, lithium
lanthanum zirconate, lithium tantalate and lithium tungstate. Of
them, the lithium ion conducting oxide may be lithium niobate, from
the point of view that formation of a resistive layer by reaction
between the cathode active material particles and the solid
electrolyte particles, can be suppressed.
[0058] For the composite active material particles, the content of
such a lithium ion conducting oxide in the coating layer of the
lithium ion conducting oxide, may be 90 mass % or more. The upper
limit of the content is not particularly limited. For example, the
upper limit is 100 mass % or less.
[0059] The thickness of the coating layer is not particularly
limited. From the viewpoint of decreasing battery resistance, the
thickness may be 3 nm or more and 100 nm or less.
[Moisture Content]
[0060] The moisture content of the cathode active material
particles may be less than 402 ppm, may be 310 ppm or less, may be
119 ppm or less, or may be 70 ppm or less. By decreasing the
moisture content of the particles to such a very low level, when
the cathode is used in an all-solid-state battery, the
below-described solid electrolyte particles can be suppressed from
being deteriorated by the moisture contained in the cathode active
material particles, and the solid electrolyte particles can keep
high conductivity.
[Solid Electrolyte Particles]
[0061] The solid electrolyte particles may be particles composed of
a solid electrolyte such as an oxide-based solid electrolyte and a
sulfide-based solid electrolyte. The solid electrolyte may be a
sulfide-based solid electrolyte. Also, the solid electrolyte
particles may be sulfide-based solid electrolyte particles.
[0062] As the sulfide-based solid electrolyte, examples include,
but are not limited to, Li.sub.2S--SiS.sub.2,
LiI--Li.sub.2S--SiS.sub.2, LiI--Li.sub.2S--P.sub.2S.sub.5,
LiI--Li.sub.2O--Li.sub.2S--P.sub.2S.sub.5,
LiI--Li.sub.2S--P.sub.2O.sub.5,
LiI--Li.sub.3PO.sub.4--P.sub.2S.sub.5, Li.sub.2S--P.sub.2S.sub.5
and Li.sub.3PS.sub.4.
[0063] As the oxide-based solid electrolyte, examples include, but
are not limited to, Li.sub.6.25La.sub.3Zr.sub.2Al.sub.0.25O.sub.12,
Li.sub.3PO.sub.4, and Li.sub.3+xPO.sub.4-xN.sub.x (LiPON).
[0064] As the solid electrolyte, one or more kinds of solid
electrolytes may be used.
[0065] The solid electrolyte may be amorphous, crystalline or glass
ceramic.
[0066] The content of the solid electrolyte particles in the
cathode layer is not particularly limited.
[Other Components]
[0067] As the electroconductive material, examples include, but are
not limited to, carbonaceous materials such as vapor-grown carbon
fiber, acetylene black (AB), Ketjen Black (KB), carbon nanotube
(CNT) and carbon nanofiber, and metal materials that are resistant
to the environment where the all-solid-state battery is used. The
content of the electroconductive material in the cathode layer is
not particularly limited.
[0068] As the binder, examples include, but are not limited to,
acrylonitrile-butadiene rubber (ABR), butadiene rubber (BR),
polyvinylidene fluoride (PVdF) and styrene-butadiene rubber (SBR).
The content of the binder in the cathode layer is not particularly
limited.
[0069] The thickness of the cathode layer is not particularly
limited. It can be appropriately determined depending on desired
performance.
[Cathode Current Collector]
[0070] As the cathode current collector, a conventionally-known
metal that is usable as a current collector in all-solid-state
batteries, can be used. As the metal, examples include, but are not
limited to, a metal material containing one or more elements
selected from the group consisting of Cu, Ni, Al, V, Au, Pt, Mg,
Fe, Ti, Co, Cr, Zn, Ge and In.
[0071] The form of the cathode current collector is not
particularly limited. As the form, examples include, but are not
limited to, various kinds of forms such as a foil form and a mesh
form.
[0072] The whole form of the cathode is not particularly limited.
It may be a sheet form. In this case, the whole thickness of the
cathode is not particularly limited. It can be determined depending
on desired performance.
[0073] The method for forming the cathode layer is not particularly
limited. As the method, examples include, but are not limited to,
pressure-forming a powdered cathode mix that contains the cathode
active material particles, the solid electrolyte particles and, as
needed, other components.
[XPS Measurement of Cathode Layer]
[0074] For the cathode of the disclosed embodiments, in a
photoelectron spectrum by X-ray photoelectron spectroscopy
measurement of the cathode layer, the P peak intensity ratio (A/B),
which is derived from the phosphorus element, of the signal
intensity A at a binding energy of 131.6 eV to the signal intensity
B at a binding energy of 133.1 eV, is larger than 0.58.
[0075] The binding energy (131.6 eV) of the signal intensity A
indicates, for example, the energy of a P--S bond between the
phosphorus element and a sulfur element.
[0076] The binding energy (133.1 eV) of the signal intensity B
indicates, for example, the binding energy between an oxygen
element and the phosphorus element while the phosphorus element is
in an oxidized state, such as Pox.
[0077] Accordingly, the ratio (A/B) is a measure to judge whether
the phosphorus element is kept in an unoxidized state (e.g., P--S
bond) or not.
[0078] The P peak intensity ratio (A/B) may be larger than 0.58.
When the P peak intensity ratio (A/B) is larger than 0.58, it means
that the phosphorus element is not oxidized and the cathode layer
is not deteriorated. Accordingly, the upper limit of the P peak
intensity ratio (A/B) is not particularly limited. The upper limit
may be 2.0 or less, or it may be 1.55 or less.
[0079] The timing for the XPS measurement of the cathode layer is
not particularly limited.
[0080] The XPS measurement of the cathode layer may be carried out
by the following method, for example. When the XPS measurement of
the cathode layer is carried out after the all-solid-state battery
is initially discharged, the initially charged all-solid-state
battery is disassembled; the cathode layer is taken out; and the
XPS measurement is directly carried out on the cathode layer. Then,
the peak intensity ratio can be calculated from a photoelectron
spectrum thus obtained.
[0081] Also, the XPS measurement of the cathode layer may be
carried out as follows: the all-solid-state battery is
disassembled; the cathode is taken out; the cathode is cut and/or
polished as it is without removing the current collector from the
cathode, or the cathode is freeze-fractured. Also, the cathode
layer may be made into a powder before the XPS measurement.
2. All-Solid-State Battery
[0082] FIG. 1 is a schematic sectional view of an example of the
all-solid-state battery of the disclosed embodiments.
[0083] As shown in FIG. 1, an all-solid-state battery 100
comprises: a cathode 16 comprising a cathode layer 12 and a cathode
current collector 14, an anode 17 comprising an anode layer 13 and
an anode current collector 15, and a solid electrolyte layer 11
disposed between the cathode 16 and the anode 17.
[Cathode]
[0084] The structure of the cathode is as described above.
[Solid Electrolyte Layer]
[0085] The solid electrolyte layer contains a solid
electrolyte.
[0086] As the solid electrolyte contained in the solid electrolyte
layer, a conventionally-known solid electrolyte that is usable in
all-solid-state batteries, can be appropriately used. As such a
solid electrolyte, examples include, but are not limited to, a
solid electrolyte that can be incorporated in the cathode or in the
below-described anode.
[0087] As the solid electrolyte, one or more kinds of solid
electrolytes may be used. In the case of using two or more kinds of
solid electrolytes, they may be mixed together, or they may be
formed into layers to obtain a multi-layered structure.
[0088] The proportion of the solid electrolyte in the solid
electrolyte layer is not particularly limited. For example, it may
be 50 mass % or more, may be in a range of 60 mass % or more and
100 mass % or less, may be in a range of 70 mass % or more and 100
mass % or less, or may be 100 mass %.
[0089] From the viewpoint of exerting plasticity, etc., a binder
for binding solid electrolyte particles can be incorporated in the
solid electrolyte layer. As the binder, examples include, but are
not limited to, a binder that can be incorporated in the cathode or
in the below-described anode. However, the content of the binder in
the solid electrolyte layer may be 5 mass % or less, from the
viewpoint of preventing excessive aggregation of the solid
electrolyte and forming the solid electrolyte layer in which the
solid electrolyte is uniformly dispersed, for the purpose of easily
achieving high power output.
[0090] The form of the solid electrolyte layer is not particularly
limited. It may be a sheet form. In this case, the thickness of the
solid electrolyte layer is not particularly limited. It can be
determined depending on desired performance. It is generally 0.1
.mu.m or more and 1 mm or less.
[0091] As the method for forming the solid electrolyte layer,
examples include, but are not limited to, pressure-forming a
powdered solid electrolyte material that contains the solid
electrolyte and, as needed, other components. In the case of
pressure-forming the powdered solid electrolyte material,
generally, a press pressure of about 1 MPa or more and about 400
MPa or less is applied.
[Anode]
[0092] The anode comprises an anode layer. As needed, the anode may
comprise an anode current collector that is in contact with the
anode layer.
[0093] The anode layer contains an anode active material. The anode
layer may contain a solid electrolyte, a binder, an
electroconductive material and so on as optional components.
[0094] As the anode active material, a conventionally-known
material can be used. As the anode active material, examples
include, but are not limited to, a Li metal, carbon, Si, a Si alloy
and Li.sub.4Ti.sub.5O.sub.12 (LTO).
[0095] As the Si alloy, examples include, but are not limited to,
an alloy with a metal such as Li, and an alloy with at least one
metal selected from the group consisting of Sn, Ge and Al.
[0096] By assembling the all-solid-state battery and initially
charging the same, the Si is reacted with a metal such as Li to
form an amorphous alloy. An alloyed part of the Si is kept
amorphized even after metal ions such as lithium ions are released
by discharging the battery. In the disclosed embodiments,
therefore, the anode layer comprising Si include such an embodiment
that the Si is formed into amorphous alloy.
[0097] The form of the anode active material is not particularly
limited. For example, it may be a particulate form or a thin film
form.
[0098] The average particle diameter (D.sub.50) of the anode active
material may be 1 nm or more and 100 .mu.m or less, or it may be 10
nm or more and 30 .mu.m or less, for example.
[0099] In the disclosed embodiments, the average particle diameter
of particles is a value measured by laser diffraction/scattering
particle size distribution analysis. Also in the disclosed
embodiments, the median diameter (D.sub.50) is a diameter at which,
when the particle diameters of particles are arranged in ascending
order, the accumulated volume of the particles is half (50%) the
total volume of the particles.
[0100] The content of the anode active material in the anode layer
is not particularly limited. For example, it may be 40 mass % or
more and 100 mass % or less.
[0101] As the solid electrolyte, examples include sulfide- and
oxide-based solid electrolytes as mentioned above. The solid
electrolyte may be amorphous, crystalline or glass ceramic.
[0102] The content of the solid electrolyte in the anode layer is
not particularly limited.
[0103] The binder and electroconductive material used in the anode
layer, may be appropriately selected from the above-mentioned
examples applicable to the cathode layer.
[0104] The contents of the binder and electroconductive material in
the anode layer, are not particularly limited.
[0105] The thickness of the anode layer is not particularly
limited. It can be appropriately determined depending on desired
performance.
[0106] As the anode current collector, a conventionally-known metal
that is usable as a current collector in all-solid-state batteries,
can be used. As the metal, examples include, but are not limited
to, a metal material containing one or more elements selected from
the group consisting of Cu, Ni, Al, V, Au, Pt, Mg, Fe, Ti, Co, Cr,
Zn, Ge and In.
[0107] The form of the anode current collector is not particularly
limited. As the form, examples include, but are not limited to,
various kinds of forms such as a foil form and a mesh form.
[0108] The whole form of the anode is not particularly limited. It
may be a sheet form. In this case, the whole thickness of the anode
is not particularly limited. It can be determined depending on
desired performance.
[0109] The method for forming the anode layer is not particularly
limited. As the method, examples include, but are not limited to,
pressure-forming a powdered anode mix that contains the anode
active material and, as needed, other components.
[0110] As needed, the all-solid-state battery comprises an outer
casing for housing the cathode, the anode and the solid electrolyte
layer.
[0111] The form of the outer casing is not particularly limited. As
the form, examples include, but are not limited to, a laminate
form.
[0112] The material for the outer casing is not particularly
limited, as long as it is a material that is stable in
electrolytes. As the material, examples include, but are not
limited to, resins such as polypropylene, polyethylene and acrylic
resin.
[0113] As the all-solid-state battery, examples include, but are
not limited to, a lithium ion battery, a sodium battery, a
magnesium battery and a calcium battery. The all-solid-state
battery may be a lithium ion battery.
[0114] As the form of the all-solid-state battery, examples
include, but are not limited to, a coin form, a laminate form, a
cylindrical form and a square form.
3. Method for Producing Cathode
[0115] The cathode production method of the disclosed embodiments
is a method for producing a cathode comprising a cathode layer for
all-solid-state batteries, the method comprising:
[0116] preparing cathode active material particles;
[0117] vacuum-drying the cathode active material particles at a
temperature of 120.degree. C. or more and 300.degree. C. or less
for one hour or more;
[0118] mixing the cathode active material particles with solid
electrolyte particles to obtain a cathode mix; and
[0119] forming the cathode mix to obtain the cathode layer,
[0120] wherein at least one of the cathode active material
particles and the solid electrolyte particles contain a phosphorus
element, and
[0121] wherein, in a photoelectron spectrum by a X-ray
photoelectron spectroscopy measurement of the cathode layer, a P
peak intensity ratio (A/B), which is derived from the phosphorus
element, of a signal intensity A at a binding energy of 131.6 eV to
a signal intensity B at a binding energy of 133.1 eV, is larger
than 0.58.
[0122] The cathode production method of the disclosed embodiments
comprises at least (1) preparing, (2) vacuum-drying, (3) mixing and
(4) forming.
[0123] Hereinafter, these steps will be described in order.
(1) Preparing
[0124] This is a step of preparing cathode active material
particles.
[0125] The cathode active material particles will not be described
here, since they are the same as those described above under "1.
Cathode".
[0126] In the preparing, the composite active material particles
comprising the cathode active material particles and the lithium
ion conducting oxide, the lithium ion conducting oxide coating at
least part of the surface of the cathode active material particles,
may be prepared as the cathode active material, from the point of
view that formation of a resistive layer by reaction between the
cathode active material particles and the solid electrolyte
particles, can be suppressed. In the disclosed embodiments, the
given peak intensity ratio, which is obtained by XPS measurement of
the cathode layer, is determined as the measure to judge whether
the cathode active material particles contained in the cathode
layer and/or the solid electrolyte particles are kept in an
unoxidized state or not. Accordingly, as long as the cathode
comprising the cathode layer having the peak intensity ratio is
obtained, the cathode active material contained in the cathode
layer may be the cathode active material particles or composite
active material particles.
[0127] The lithium ion conducting oxide and the composite active
material particles will not be described here, since they are the
same as those described above under "1. Cathode".
[Method for Producing Composite Active Material Particles]
[0128] The method for producing the composite active material
particles may be the following method, for example: by immersing
the cathode active material particles in a solution containing an
element that will compose the lithium ion conducting oxide, or by
spraying the solution to the cathode active material particles
while the particles are in a fluidized state, the surface of the
cathode active material particles is coated with the solution; the
coated particles are dried for removal of the solvent; and the
dried particles are appropriately heated, thereby obtaining the
composite active material particles.
[0129] As the solution, a peroxo complex aqueous solution or an
alkoxide solution is used.
[0130] In the case of using the peroxo complex aqueous solution,
the composite active material particles can be produced by the
process as disclosed in Japanese Patent Application Laid-Open
(JP-A) No. 2012-74240 or JP-A No. 2016-170973, for example.
[0131] In the case of using the alkoxide solution, the composite
active material particles can be produced by the process as
disclosed in International Publication No. WO2007/004590 or JP-A
No. 2015-201252, for example.
[0132] In the cathode production method of the disclosed
embodiments, therefore, the composite active material particles may
be prepared in the preparing through (1-1) drying, on the surface
of the cathode active material particles, the peroxo complex
aqueous solution containing the element that will compose the
lithium ion conducting oxide to obtain the precursor of the
composite active material particles, and (1-2) sintering the
precursor.
(1-1) Drying
[0133] This is a step of drying, on the surface of the cathode
active material particles, the peroxo complex aqueous solution
containing the element will compose the lithium ion conducting
oxide to obtain the precursor of the composite active material
particles.
[0134] In the drying, accordingly, the cathode active material
particles are dried while the peroxo complex aqueous solution is in
contact with the surface of the cathode active material
particles.
[0135] The peroxo complex aqueous solution is brought into contact
with the surface of the cathode active material particles by the
above-described immersing or spraying. Of them, the peroxo complex
aqueous solution may be brought into contact with the particle
surface by the spraying.
[0136] When lithium niobate is used as the lithium ion conducting
oxide, the peroxo complex aqueous solution contains lithium and a
peroxo complex of niobium.
[0137] More specifically, a clear solution is produced by use of
hydrogen peroxide solution, niobic acid and ammonia water, and a
lithium compound is added to the clear solution, thereby obtaining
the peroxo complex aqueous solution. In this case, the percentage
of the moisture content of the niobic acid is not particularly
limited, since the peroxo complex of niobium can be produced even
if the percentage is changed.
[0138] Also, the mixing ratio of the niobic acid and the ammonia
water is not particularly limited, as long as the peroxo complex of
niobium can be synthesized.
[0139] As the lithium compound, examples include, but are not
limited to, LiOH, LiNO.sub.3 and Li.sub.2SO.sub.4. The lithium
compound may be a hydrate.
[0140] In the drying, after the peroxo complex aqueous solution is
brought into contact with the surface of the cathode active
material particles, volatile components that are contained in the
peroxo complex aqueous solution brought into contact with the
surface of the cathode active material particles, such as solvent
and hydration water, are removed by drying.
[0141] The drying can be carried out by use of a
tumbling/fluidizing coating device or a spray dryer, for
example.
[0142] As the tumbling/fluidizing coating device, examples include,
but are not limited to, "MULTIPLEX COATER" (manufactured by Powrex
Corporation) and "FLOW COATER" ((manufactured by Freund
Corporation).
[0143] In the drying, the drying temperature is not particularly
limited.
[0144] Also in the drying, the atmosphere (carrier gas) is not
particularly limited.
(1-2) Sintering
[0145] This is a step of sintering the thus-obtained precursor at a
given temperature. Accordingly, the composite active material
particles in which at least part of the surface of the cathode
active material particles is coated with the lithium ion conducting
oxide coating, are obtained.
[0146] The sintering can be carried out in the air atmosphere, for
example.
[0147] The sintering temperature may be the same as conventional
processes.
(2) Vacuum-Drying
[0148] This is a step of vacuum-drying the cathode active material
particles at a temperature of 120.degree. C. or more and
300.degree. C. or less for one hour or more.
[0149] By the vacuum-drying, moisture can be appropriately removed
from the cathode active material particles.
[0150] In the disclosed embodiments, "vacuum-drying" means removing
moisture from the cathode active material particles by decreasing
the atmospheric pressure to 100 kPa or less. The applied pressure
may be 50 kPa or less, or it may be 5 kPa or less.
[0151] The vacuum-drying can be carried out by use of a non-exposed
vacuum dryer, for example. More specifically, it can be carried out
by various kinds of methods, such as drying by use of an open
vacuum dryer in a glove box, and heating a hermetically sealed
system in a furnace while vacuumizing the hermetically sealed
system.
[0152] In the vacuum-drying, the vacuum-drying temperature may be
120.degree. C. or more, or it may be 200.degree. C. or more. When
the vacuum-drying temperature is too low, moisture cannot be
efficiently removed from the cathode active material particles.
[0153] In the vacuum-drying, the vacuum-drying temperature may be
300.degree. C. or less, or it may be 250.degree. C. or less. When
the composite active material particles are prepared in the
preparing, if the vacuum-drying temperature is too high, it is
possible that crystallization of the lithium ion conducting oxide
is promoted, and moisture is produced from the inside of the
crystal structure of the lithium ion conducting oxide to increase
the moisture content of the cathode active material particles. In
addition, when the crystallization of the lithium ion conducting
oxide is promoted, it is possible that the resistance of the
composite active material particles themselves increases.
[0154] In the vacuum-drying, the drying time is 1 hour or more, or
it may be 5 hours or more. When the drying time is too long, it is
difficult to appropriately remove moisture from the cathode active
material particles. The upper limit of the drying time is not
particularly limited. For example, it may be 10 hours or less.
(3) Mixing
[0155] This is a step of mixing the cathode active material
particles with solid electrolyte particles to obtain a cathode
mix.
[0156] As the solid electrolyte particles, examples include, but
are not limited to, oxide-based solid electrolyte particles and
sulfide-based solid electrolyte particles. The solid electrolyte
particles may be sulfide-based solid electrolyte particles.
[0157] The cathode active material particles and the solid
electrolyte particles may be dry-mixed, or they may be wet-mixed by
use of an organic solvent (such as a non-polar solvent).
[0158] In addition to the cathode active material particles and the
solid electrolyte particles, the cathode mix may further contain an
electroconductive material, a binder, etc.
[0159] The solid electrolyte particles, the electroconductive
material and the binder will not be described here, since they are
the same as those described above under "1. Cathode".
(4) Forming
[0160] This is a step of forming the cathode mix to obtain the
cathode layer.
[0161] The cathode mix may be dry-formed or wet-formed. The cathode
mix may be formed alone, or it may be formed in combination with
the cathode current collector. Also, the powdered cathode mix and
the solid electrolyte layer may be integrally formed on a surface
of the solid electrolyte layer.
[0162] For the cathode obtained by the production method of the
disclosed embodiments, in a photoelectron spectrum by X-ray
photoelectron spectroscopy measurement of the cathode layer, the P
peak intensity ratio (A/B), which is derived from the phosphorus
element, of the signal intensity A at a binding energy of 131.6 eV
to the signal intensity B at a binding energy of 133.1 eV, is
larger than 0.58.
[0163] The ratio (A/B) will not be described here, since it is the
same as the ratio (A/B) descried above under "1. Cathode".
4. Method for Producing all-Solid-State Battery
[0164] The all-solid-state battery production method of the
disclosed embodiments is a method for producing an all-solid-state
battery comprising:
[0165] a cathode comprising a cathode layer,
[0166] an anode comprising an anode layer, and
[0167] a solid electrolyte layer disposed between the cathode layer
and the anode layer,
[0168] wherein the cathode is a cathode produced by the
above-described production method.
[0169] The method for producing the all-solid-state battery of the
disclosed embodiments, is not particularly limited and may be a
conventionally-known method.
[0170] For example, the solid electrolyte layer is formed by
pressure-forming the powdered solid electrolyte material containing
the solid electrolyte. Next, the cathode layer is obtained by
pressure-forming the powdered cathode mix on one surface of the
solid electrolyte layer. Then, the anode layer is obtained by
pressure-forming the powdered anode mix on the other surface of the
solid electrolyte layer. Then, a cathode layer-solid electrolyte
layer-anode layer assembly thus obtained, can be the
all-solid-state battery.
[0171] In this case, the press pressure applied in the
pressure-forming of the powdered solid electrolyte material, the
powdered cathode mix and the powdered anode mix, is generally about
1 MPa or more and about 600 MPa or less.
[0172] The pressing method is not particularly limited. As the
method, examples include, but are not limited to, applying pressure
by use of a plate press machine, a roll press machine, etc.
[0173] As the method for producing the all-solid-state battery, the
powdered cathode mix, the powdered solid electrolyte material and
the powdered anode mix may be deposited and integrally formed at a
time.
[0174] The production of the cathode and the production of the
all-solid-state battery may be carried out in the state that
moisture is removed from the system as much as possible. For
example, it is thought to be effective to depressurize the inside
of the system in the production steps and to replace the inside of
the system by a substantially moisture-free gas (such as inert gas)
in the production steps.
EXAMPLES
Example 1
[Preparation of Peroxo Complex Aqueous Solution]
[0175] First, 870.4 g of hydrogen peroxide solution having a
concentration of 30 mass % was put into a container. In addition,
987.4 g of ion-exchanged water and 44.2 g of niobic acid
(Nb.sub.2O.sub.5.3H.sub.2O, Nb.sub.2O.sub.5 content: 72%) were put
into the container. Next, 87.9 g of ammonia water having a
concentration of 28 mass % was put into the container, thereby
obtaining a mixed solution. The mixed solution was sufficiently
stirred, thereby obtaining a clear solution. Next, 10.1 g of
lithium hydroxide monohydrate (LiOH.H.sub.2O) was added to the
clear solution, thereby obtaining a peroxo complex aqueous solution
containing lithium and a niobium complex.
[0176] For the thus-obtained peroxo complex aqueous solution, the
mol concentration of Li was 0.12 mol/kg, and the mol concentration
of Nb was 0.12 mol/kg.
[Spraying and Sintering]
[0177] By use of a coating device ("MP-01" manufactured by Powrex
Corporation), 2840 g of the peroxo complex aqueous solution was
sprayed onto 1 kg of cathode active material particles
(LiNi.sub.1/3Mn.sub.1/3Co.sub.1/3O.sub.2) to attach the peroxo
complex aqueous solution to the surface of the cathode active
material particles. The attached peroxo complex aqueous solution
was dried, thereby obtain a precursor of composite active material
particles.
[0178] The operation conditions of the coating device were as
follows:
[0179] Intake air/gas: Nitrogen
[0180] Intake air temperature: 120.degree. C.
[0181] Intake air flow rate: 0.4 m.sup.3/min
[0182] Rotor rotation frequency: 400 rpm
[0183] Spraying rate: 4.8 g/min
[0184] The thus-obtained precursor of the composite active material
particles was sintered in the air at 200.degree. C. for 5 hours,
thereby obtaining composite active material particles before
removal of moisture.
[Removal of Moisture]
[0185] By use of a glass tube oven (manufactured by Sibata
Scientific Technology Ltd.) as a non-exposed vacuum dryer, the
composite active material particles were vacuum-dried at
200.degree. C. for 5 hours at 5 kPa or less. Then, the composite
active material particles were collected and transferred to the
inside of a glove box under an Ar atmosphere (dew point:
-70.degree. C. or less) without exposing the particles to the air
atmosphere.
[Cathode]
[0186] The collected composite active material particles, particles
of a sulfide-based solid electrolyte (Li.sub.3PS.sub.4), 3 mass %
of VGCF (manufactured by Showa Denko K. K.) as an electroconductive
material, and 0.7 mass % of butylene rubber (manufactured by JSR
Corporation) as a binder, were put into heptane, thereby producing
a cathode mix slurry. The proportion of the VGCF and that of the
butylene rubber, which are both expressed in mass %, are values
when the total mass of a cathode layer is determined as 100 mass
%.
[0187] The produced slurry was dispersed by an ultrasonic
homogenizer. The dispersed slurry was applied onto an aluminum foil
as a cathode current collector. The applied slurry was dried at
100.degree. C. for 30 minutes, thereby obtaining a cathode in which
the cathode layer was formed on the cathode current collector.
Then, the cathode was cut in a size of 1 cm.sup.2. The composite
active material particles and the sulfide-based solid electrolyte
particles in the cathode layer were at a volume ratio of 6:2.
[Anode]
[0188] An anode active material (layered carbon), sulfide-based
solid electrolyte particles and 1.2 mass % of butylene rubber were
put into heptane, thereby producing an anode mix slurry. The
proportion of the butylene rubber, which is expressed in mass %, is
a value when the total mass of an anode layer is determined as 100
mass %.
[0189] The produced slurry was dispersed by the ultrasonic
homogenizer. The dispersed slurry was applied onto a copper foil as
an anode current collector. The applied slurry was dried at
100.degree. C. for 30 minutes, thereby obtaining an anode in which
the anode layer was formed on the anode current collector. Then,
the anode was cut in a size of 1 cm.sup.2. The anode active
material particles and the sulfide-based solid electrolyte
particles in the anode layer were at a volume ratio of 6:4.
[Solid Electrolyte Layer]
[0190] First, 64.8 mg of a sulfide-based solid electrolyte was put
into a ceramic tube having an inner diameter cross-sectional area
of 1 cm.sup.2. The sulfide-based solid electrolyte was leveled off
and then pressed at 1 ton/cm.sup.2 (.apprxeq.98 MPa), thereby
producing a solid electrolyte layer.
[All-Solid-State Battery]
[0191] The cathode was disposed on one surface of the solid
electrolyte layer, and the anode was disposed on the other surface
of the solid electrolyte layer, thereby obtaining a stack. After
the stack was pressed at 4.3 ton/cm.sup.2 for one minute, a
stainless rod is inserted in the cathode, and another stainless rod
was inserted in the anode. The stack was confined at 1 ton/cm.sup.2
(.apprxeq.98 MPa), thereby producing an all-solid-state
battery.
Comparative Example 1
[0192] A cathode and an all-solid-state battery were obtained in
the same manner as Example 1, except that the above-mentioned
"Removal of moisture" was not carried out, and composite active
material particles before removal of moisture were used in the
above-described "Cathode".
[Measurement of Internal Resistance of all-Solid-State
Batteries]
[0193] The all-solid-state battery of Example 1 was charged to a
voltage of 4.37 V and then discharged to 3.0 V. Next, the internal
resistance (initial internal resistance) during the initial
discharging of the all-solid-state battery when the battery voltage
was 3.95 V, was measured by an AC impedance method. The internal
resistance (initial internal resistance) of the all-solid-state
battery of Comparative Example 1 was measured in the same manner as
Example 1. The measurement results are shown in Table 1.
[0194] Then, a durability test was carried out as follows: the
voltage of each all-solid-state battery was controlled to 4.1 V,
and each all-solid-state battery was stored in an environment
controlled at 60.degree. C. for 28 days.
[0195] Then, the internal resistance of each all-solid-state
battery after the durability test, was measured by the AC impedance
method when the battery voltage was 3.95 V. The measurement results
are shown in Table 1. In the disclosed embodiments, the internal
resistance means the sum of DC resistance, reaction resistance,
diffusion resistance and other resistances.
[Measurement of Moisture Content of Composite Active Material
Particles]
[0196] The moisture content of the composite active material
particles of Example 1 and that of the composite active material
particles of Comparative Example 1, were measured by the Karl
Fischer titration method.
[0197] More specifically, the moisture content measurement was
carried out as follows. A coulometric Karl Fischer titrator
(manufactured by Hiranuma Sangyo Co., Ltd.) was used for the
measurement. The composite active material particles were placed in
the heating member of the titrator, which was controlled at
200.degree. C., thereby releasing moisture from the composite
active material particles. The released moisture was measured by
allowing nitrogen gas, which was used as a carrier, to flow into
the measuring member of the titrator. The measurement time was 40
minutes. The measurement results are shown in Table 1.
[XPS Measurement of Cathode Layer]
[0198] After the all-solid-state battery of Example 1 was initially
charged, the initially charged all-solid-state battery was
disassembled; the cathode was taken out; and the aluminum foil was
removed from the cathode, thereby obtaining the cathode layer. XPS
measurement was directly carried out on the cathode layer. For the
cathode layer, the narrow-range photoelectron spectrum of the
phosphorus element was measured by use of "QUANTERA" (manufactured
by ULVAC-PHI, Inc.) in the following conditions:
[0199] X-ray output: 25 W
[0200] X-ray beam size: 100 .mu.m .PHI.
[0201] X-ray take-off angle: 45 degrees
[0202] For the all-solid-state battery of Comparative Example 1,
the XPS measurement of the cathode layer and the measurement of the
narrow-range photoelectron spectrum of the phosphorus element, were
carried out in the same manner as Example 1.
[0203] FIG. 2 shows the photoelectron spectrum of Example 1.
[0204] FIG. 3 shows the photoelectron spectrum of Comparative
Example 1.
[0205] From the thus-obtained photoelectron spectra, the P peak
intensity ratio of Example 1 and that of Comparative Example 1 were
calculated. The results are shown in Table 1.
TABLE-US-00001 TABLE 1 Internal Moisture resistance (.OMEGA.) P
peak content Initial internal after durability intensity (ppm)
resistance (.OMEGA.) test ratio Example 1 70 15.6 19.1 1.55
Comparative 402 17.2 21 0.58 Example 1
[Evaluation Result]
[0206] As shown in Table 1, the peak intensity ratio of the cathode
layer of Example 1 is larger than that of the cathode layer of
Comparative Example 1.
[0207] For the composite active material particles of Example 1 in
which the removal of the moisture was carried out by vacuum-drying,
it was revealed that the moisture content was remarkably decreased
compared to the composite active material particles of Comparative
Example 1 in which the removal of the moisture was not carried
out.
[0208] For the all-solid-state battery of Example 1, it was
revealed that the internal resistance was remarkably decreased
compared to the all-solid-state battery of Comparative Example
1.
[0209] The effect exerted by the vacuum-drying is considered as
follows. By significantly removing the moisture contained in the
composite active material particles, in the all-solid-state
battery, reaction between the moisture contained in the composite
active material particles and the sulfide-based solid electrolyte
being in contact with the composite active material particles, was
suppressed, and oxidation of the sulfide-based solid electrolyte
was suppressed. Accordingly, it is thought that the conductivity of
the sulfide-based solid electrolyte was kept high and, as a result,
the battery resistance of the all-solid-state battery was
decreased.
[0210] Therefore, it was proved that the internal resistance of the
all-solid-state battery comprising the cathode layer can be
decreased when, as described above, in a photoelectron spectrum by
X-ray photoelectron spectroscopy measurement of the cathode layer,
the P peak intensity ratio (A/B), which is derived from the
phosphorus element, of the signal intensity A at a binding energy
of 131.6 eV to the signal intensity B at a binding energy of 133.1
eV, is larger than 0.58.
REFERENCE SIGNS LIST
[0211] 11. Solid electrolyte layer [0212] 12. Cathode layer [0213]
13. Anode layer [0214] 14. Cathode current collector [0215] 15.
Anode current collector [0216] 16. Cathode [0217] 17. Anode [0218]
100. All-solid-state battery
* * * * *