U.S. patent application number 15/146207 was filed with the patent office on 2016-12-01 for device for producing composite active material powder and method for producing composite active material powder.
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 Masahiro IWASAKI.
Application Number | 20160351899 15/146207 |
Document ID | / |
Family ID | 57281624 |
Filed Date | 2016-12-01 |
United States Patent
Application |
20160351899 |
Kind Code |
A1 |
IWASAKI; Masahiro |
December 1, 2016 |
DEVICE FOR PRODUCING COMPOSITE ACTIVE MATERIAL POWDER AND METHOD
FOR PRODUCING COMPOSITE ACTIVE MATERIAL POWDER
Abstract
A device produces a composite active material powder by coating
active material or composite particle surfaces, which are obtained
by coating the active material particle surfaces with an
oxide-based solid electrolyte, with a sulfide-based solid
electrolyte. The device includes: a storage body having a
cylindrical inner wall surface, and a rotating body disposed in an
internal space surrounded by the storage body inner wall surface,
having a rotating shaft aligned with the internal space central
axis, and which includes blades. Each blade end part has such a
tapered section on a front side in the rotating body
rotation/movement direction, that a thickness of the blade
gradually tapers toward a blade end side, and each blade end part
has such a curved end surface on a back side in the rotating body
rotation/movement direction, that the curved end surface faces the
storage body inner wall surface and is generally parallel
thereto.
Inventors: |
IWASAKI; Masahiro;
(Nagoya-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: |
57281624 |
Appl. No.: |
15/146207 |
Filed: |
May 4, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 4/525 20130101;
B01F 7/00116 20130101; H01M 4/366 20130101; H01M 4/505 20130101;
Y02E 60/10 20130101; H01M 4/62 20130101; H01M 4/1391 20130101; H01M
4/587 20130101; H01M 10/0562 20130101; H01M 10/052 20130101; B01F
7/04 20130101; B01F 7/0025 20130101 |
International
Class: |
H01M 4/36 20060101
H01M004/36; H01M 4/525 20060101 H01M004/525; H01M 4/505 20060101
H01M004/505; H01M 4/58 20060101 H01M004/58 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 1, 2015 |
JP |
2015-111110 |
Claims
1. A device for producing a composite active material powder by
coating surfaces of active material particles or composite
particles, which are obtained by coating the surfaces of the active
material particles with an oxide-based solid electrolyte, with a
sulfide-based solid electrolyte, wherein the device comprises: a
storage body which has a cylindrical inner wall surface, and a
rotating body which is disposed in an internal space that is
surrounded by the inner wall surface of the storage body, which has
a rotating shaft that is aligned with a central axis of the
internal space, and which includes a plurality of blades, and
wherein an end part of each blade has such a tapered section on a
front side in a rotation/movement direction of the rotating body,
that a thickness of the blade gradually tapers toward a blade end
side, and the end part of each blade has such a curved end surface
on a back side in the rotation/movement direction of the rotating
body, that the curved end surface faces the inner wall surface of
the storage body and is generally parallel to the inner wall
surface of the storage body.
2. The device for producing the composite active material powder
according to claim 1, wherein a width of the end surface of the end
part of each blade is in a range of 0.1 to 0.7 with respect to the
thickness of the blade.
3. The device for producing the composite active material powder
according to claim 1, wherein, in a rotating shaft direction front
view of the rotating body, a length of the end part of each blade
in a radial direction of the rotating body is 0.5 to 30 mm.
4. The device for producing the composite active material powder
according to claim 1, wherein the width of the end surface of the
end part of each blade is 0.5 to 30 mm.
5. The device for producing the composite active material powder
according to claim 1, wherein a clearance between the end surface
of the end part of each blade and the inner wall surface of the
storage body is 0.5 to 10 mm.
6. The device for producing the composite active material powder
according to claim 1, wherein, in the rotating shaft direction
front view of the rotating body, an inclined angle of the tapered
section is 10 to 80.degree. to a tangent line at a point of
intersection between an inclined surface of the tapered section and
the inner wall surface of the storage body.
7. A method for producing a composite active material powder,
wherein surfaces of active material particles or composite
particles, which are obtained by coating the surfaces of the active
material particles with an oxide-based solid electrolyte, are
coated with a sulfide-based solid electrolyte by preparing the
production device defined by claim 1, putting the sulfide-based
solid electrolyte and any one of the active material particles and
the composite particles into the storage body of the production
device, and then rotating the storage body.
8. The method for producing the composite active material powder
according to claim 7, wherein the active material particles are
particles which contain at least any one of a cobalt element, a
nickel element and a manganese element, and which further contain a
lithium element and an oxygen element.
Description
BACKGROUND OF THE INVENTION
[0001] Technical Field
[0002] The present invention relates to a device for producing a
composite active material powder and a method for producing a
composite active material powder.
[0003] Background Art
[0004] In the field of all-solid-state batteries, there is an
attempt to improve the performance of all-solid-state batteries,
focusing on an interface between the electrode active material and
the solid electrolyte material.
[0005] Examples of conventional methods for coating the surfaces of
active material-containing particles with a sulfide-based solid
electrolyte, include gas phase methods such as pulsed laser
deposition (hereinafter may be referred to as PLD). However, the
PLD method is generally slow in film-forming rate, so that it is
remarkably low in productivity and is not practical. Also in the
PLD method, the target of the sulfide-based solid electrolyte is
turned into a plasma by laser irradiation. At this time, the
composition of the sulfide-based solid electrolyte may be changed
and may not be maintained.
[0006] Examples of other methods for coating the surfaces of active
material-containing particles with a sulfide-based solid
electrolyte, include mixing/kneading methods using a medium such as
planetary ball mill. However, in such mixing/kneading methods using
the medium, mechanical damage is applied in collision with the
medium and, as a result, the surfaces of the active
material-containing particles may be damaged. Therefore, to avoid
such mechanical damage, there is a demand for mixing/kneading
methods using no medium.
[0007] For example, in Patent Literature 1, as a technique to solve
the above problem, a method for obtaining a composite powder is
disclosed, in which different kinds of powders are bound by
applying a mechanical action, which contains compression and sheer
forces, to a raw material powder, which is made from various kind
of powders, using a powder treating device.
[0008] Patent Literature 1: Japanese Patent Application Laid-Open
No. 2010-180099
[0009] However, the use of the conventional composite active
material powder production device as disclosed in Patent Literature
1, is problematic in that the internal resistance of a battery
using the thus-obtained composite active material powder is
large.
SUMMARY OF THE INVENTION
[0010] The present invention was achieved in light of the above
circumstance. An object of the present invention is to provide a
device that is able to produce a composite active material powder,
which is able to reduce the internal resistance of a battery, and a
method for producing the composite active material powder.
[0011] The device for producing a composite active material powder
according to the present invention is a device for producing a
composite active material powder by coating the surfaces of active
material particles or composite particles, which are obtained by
coating the surfaces of the active material particles with an
oxide-based solid electrolyte, with a sulfide-based solid
electrolyte, wherein the device includes: a storage body which has
a cylindrical inner wall surface, and a rotating body which is
disposed in an internal space that is surrounded by the inner wall
surface of the storage body, which has a rotating shaft that is
aligned with a central axis of the internal space, and which
includes a plurality of blades, and wherein an end part of each
blade has such a tapered section on a front side in a
rotation/movement direction of the rotating body, that a thickness
of the blade gradually tapers toward a blade end side, and the end
part of each blade has such a curved end surface on a back side in
the rotation/movement direction of the rotating body, that the
curved end surface faces the inner wall surface of the storage body
and is generally parallel to the inner wall surface of the storage
body.
[0012] In the device for producing a composite active material
powder according to the present invention, the width of the end
surface of the end part of each blade is preferably in a range of
0.1 to 0.7 with respect to the thickness of the blade.
[0013] In the device for producing a composite active material
powder according to the present invention, in the rotating shaft
direction front view of the rotating body, the length of the end
part of each blade in the radial direction of the rotating body is
preferably 0.5 to 30 mm.
[0014] In the device for producing a composite active material
powder according to the present invention, the width of the end
surface of the end part of each blade is preferably 0.5 to 30
mm.
[0015] In the device for producing a composite active material
powder according to the present invention, the clearance between
the end surface of the end part of each blade and the inner wall
surface of the storage body is preferably 0.5 to 10 mm.
[0016] In the device for producing a composite active material
powder according to the present invention, in the rotating shaft
direction front view of the rotating body, the inclined angle of
the tapered section is preferably 10 to 80.degree. to a tangent
line at a point of intersection between the inclined surface of the
tapered section and the inner wall surface of the storage body.
[0017] The method for producing the composite active material
powder according to the present invention is a method wherein the
surfaces of active material particles or composite particles, which
are obtained by coating the surfaces of the active material
particles with an oxide-based solid electrolyte, are coated with a
sulfide-based solid electrolyte by preparing the device for
producing composite active material powder, putting the
sulfide-based solid electrolyte and any one of the active material
particles and the composite particles into the storage body of the
production device, and then rotating the storage body.
[0018] In the method for producing the composite active material
powder according to the present invention, the active material
particles are preferably particles which contain at least any one
of a cobalt element, a nickel element and a manganese element, and
which further contain a lithium element and an oxygen element.
[0019] According to the present invention, a device that is able to
produce a composite active material powder, which is able to reduce
the internal resistance of a battery, and a method for producing
the composite active material powder can be provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a schematic side view of the production device of
the present invention.
[0021] FIG. 2 is a schematic front view of a rotating body shown in
FIG. 1.
[0022] FIG. 3 is a schematic view of blades installed to a rotating
shaft of a rotating body.
[0023] FIG. 4 is a schematic sectional view of an embodiment of a
composite active material powder.
DETAILED DESCRIPTION OF THE INVENTION
1. Device for Producing Composite Active Material Powder
[0024] The device for producing a composite active material powder
according to the present invention is a device for producing a
composite active material powder by coating the surfaces of active
material particles or composite particles, which are obtained by
coating the surfaces of the active material particles with an
oxide-based solid electrolyte, with a sulfide-based solid
electrolyte, wherein the device includes: a storage body which has
a cylindrical inner wall surface, and a rotating body which is
disposed in an internal space that is surrounded by the inner wall
surface of the storage body, which has a rotating shaft that is
aligned with a central axis of the internal space, and which
includes a plurality of blades, and wherein an end part of each
blade has such a tapered section on a front side in a
rotation/movement direction of the rotating body, that a thickness
of the blade gradually tapers toward a blade end side, and the end
part of each blade has such a curved end surface on a back side in
the rotation/movement direction of the rotating body, that the
curved end surface faces the inner wall surface of the storage body
and is generally parallel to the inner wall surface of the storage
body.
[0025] The inventor of the present invention has found that the
internal resistance of a battery can be reduced more than ever
before by shaping the form of the end part of each blade. The
reason for this is supposed to be as follows: because the end part
of each blade has the tapered section on the front side in the
rotation/movement direction of the rotating body, a raw material
powder can be efficiently supplied to a treating section (a minute
space between the end part of each blade and the inner wall surface
of the storage body); moreover, because the end part of each blade
has such a curved end surface on the back side in the
rotation/movement direction of the rotating body, that the curved
end surface faces the inner wall surface of the storage body and is
generally parallel to the inner wall surface of the storage body,
the time required to grind the raw material powder becomes longer
for the width of the end surface, and the efficiency of coating the
surfaces of the active material particles or the below-described
composite particles with the sulfide-based solid electrolyte
(coating efficiency) is increased. As a result, it is considered
that the internal resistance of a battery using the thus-obtained
composite active material powder becomes low.
[0026] In the present invention, "coat" means to coat 40% or more
of the surface of each active material particle or composite
particle.
[0027] Also in the present invention, internal resistance means the
sum of direct-current resistance, reaction resistance, diffusion
resistance and other resistances.
[0028] Hereinafter, an embodiment of the composite active material
powder production device of the present invention will be
described.
[0029] FIG. 1 is a schematic side view of an embodiment of the
production device of the present invention.
[0030] As shown in FIG. 1, a production device 100 includes a
storage body 11, which has a cylindrical inner wall surface 12 and
a laterally extending central axis X (indicated by an alternate
long and short dash line in FIG. 1), and a rotating body 13, which
is disposed in the internal space that is surrounded by the inner
wall surface 12 of the storage body 11 and which is rotary driven
around the central axis X. The rotating body 13 has a rotating
shaft 14, which is aligned with the central axis X, and a plurality
of blades 15, which extend outwardly in a radial direction from an
outer peripheral part of the rotating shaft 14. One end of the
rotating shaft 14 is supported by a bearing 16 and connected to a
motor 17, which is a driving means. An opening is provided at the
right end of the storage body 11, so that materials can be put into
the storage body through the opening.
[0031] As needed, the external wall of the storage body 11 can be
surrounded by a chiller pipe for circulating a temperature control
fluid (not shown).
[0032] FIG. 2 is a schematic front view of a rotating body shown in
FIG. 1.
[0033] In FIG. 2, an arrow indicates the rotation direction of the
rotating body 13.
[0034] As shown in FIG. 2, an end part 19 of each blade 15 has such
a tapered section on the front side in the rotation/movement
direction of the rotating body 13, that the thickness of the blade
gradually tapers toward the blade end side.
[0035] As shown in FIG. 2 (that is, in the rotating shaft direction
front view of the rotating body 13 shown in FIG. 1), an inclined
angle 20 of the tapered section is preferably 10 to 80.degree. to a
tangent line L at a point of intersection between an extended line
extended from an inclined surface 28 of the tapered section in the
inclined direction and the inner wall surface 12 of the storage
body 11. From the viewpoint of increasing the amount of the raw
material powder incorporated into a clearance 22, the inclined
angle 20 is particularly preferably 30 to 60.degree..
[0036] Also, the end part 19 of each blade 15 has such a curved end
surface 21 on the back side in the rotation/movement direction of
the rotating body 13, that the curved end surface 21 faces the
inner wall surface 12 of the storage body 11 and is generally
parallel to the inner wall surface 12 of the storage body 11. That
is, by shaping the end surface 21 of the end part 19 of each blade
15 in the form of a curved surface that curves circularly around
the inner wall surface 12 of the storage body 11, the clearance 22
between the end surface 21 of the end part 19 of each blade 15 and
the inner wall surface 12 of the storage body 11 is generally kept
constant, over the total length of the end surface 21. The reason
for keeping the clearance 22 constant is to apply a uniform force
to the powder. The reason for keeping the clearance 22 minute is to
apply a stronger force to the powder by reducing the space for
passing the powder therethrough. The clearances 22 between the
inner wall surface 12 of the storage body 11 and the end parts 19
of the blades 15 can vary depending on the positions where the
blades 15 are installed.
[0037] The clearance (minute space) 22 between the end surface of
the end part 19 of each blade 15 and the inner wall surface 12 of
the storage body 11 is preferably 0.5 mm or more, particularly
preferably 1 mm or more, and it is preferably 10 mm or less,
particularly preferably 5 mm or less. If the clearance is more than
10 mm, the space for passing the powder therethrough increases and
cannot apply a strong mechanical action to the powder. On the other
hand, if the clearance 22 is less than 0.5 mm, the amount of the
powder which can be incorporated into the clearance 22 is small, so
that a long treatment time is needed, and there is an increase in
production cost. Also, the blades 15 may be brought into contact
with the storage body 11, due to an unexpected vibration that is
caused during operation by overload, etc.
[0038] As shown in FIG. 2 (that is, in the rotating shaft direction
front view of the rotating body 13 shown in FIG. 1), a width 23 of
the end surface 21 of the end part 19 of each blade 15 is 0.5 mm or
more, particularly preferably 1 mm or more, and it is preferably 30
mm or less, particularly preferably 20 mm or less.
[0039] A thickness 24 of each blade 15 is preferably 1 mm or more,
more preferably 2 mm or more, still more preferably 5 mm or more,
and it is preferably 100 mm or less, more preferably 50 mm or less,
still more preferably 20 mm or less.
[0040] The width 23 of the end surface 21 of the end part 19 of
each blade 15 is preferably in a range of 0.01 to 0.95, more
preferably in a range of 0.1 to 0.7, with respect to the thickness
24 of the blade 15.
[0041] A length 25 of the end part 19 of each blade 15 in the
radial direction of the rotating body 13 is preferably 0.5 mm or
more, more preferably 1 mm or more, still more preferably 3 mm or
more, and it is preferably 30 mm or less, particularly preferably
20 mm or less.
[0042] A total length 26 of each blade 15 is preferably 10 mm or
more, particularly preferably 15 mm or more, and it is preferably
600 mm or less, particularly preferably 400 mm or less.
[0043] The length 25 of the end part 19 of each blade 15 is
preferably in a range of 0.002 to 1, more preferably in a range of
0.05 to 0.95, with respect to the total length 26 of each blade
15.
[0044] A diameter 27 of the rotating shaft 14 of the rotating body
13 is preferably 30 mm or more, particularly preferably 40 mm or
more, and it is preferably 1000 mm or less, particularly preferably
500 mm or less.
[0045] FIG. 3 is a schematic view of blades installed to a rotating
shaft of the rotating body. An arrow shown in FIG. 3 indicates the
rotation direction of the rotating body.
[0046] As shown in FIG. 3, each blade 15 is installed parallel to
the rotating shaft 14.
[0047] Each blade 15 can be installed at an angle in relation to
the rotating shaft 14. The number of the blades 15 installed to the
rotating shaft 14 is not particularly limited. It can be
appropriately determined depending on the scale of the device, the
amount of the raw materials put into the production device,
etc.
2. Method for Producing Composite Active Material Powder
[0048] The method for producing the composite active material
powder according to the present invention is a method wherein the
surfaces of active material particles or composite particles, which
are obtained by coating the surfaces of the active material
particles with an oxide-based solid electrolyte, are coated with a
sulfide-based solid electrolyte by preparing the production device,
putting the sulfide-based solid electrolyte and any one of the
active material particles and the composite particles into the
storage body of the production device, and then rotating the
storage body.
[0049] The production device that can be used in the production
method of the present invention will not be described here, since
it is the same as the device described above under "1. Device for
producing composite active material powder".
[0050] The temperature inside the storage body is not particularly
limited. Preferably, the temperature is controlled to 100.degree.
C. or less.
[0051] The peripheral speed of the rotating body is preferably 10
to 30 m/sec.
[0052] The rotating time of the rotating body is not particularly
limited. For example, it can be 30 seconds to 3 hours.
[0053] The amount of the raw material powder put into the storage
body is preferably set in a range of 5 to 95% of the inner volume
of the treating space inside the storage body, so that the powder
is more effectively subjected to a stirring action inside the
storage body. The inner volume of the treating space inside the
storage body means the volume of a space obtained by deducting the
volume occupied by the rotating body from the inner volume of the
storage body itself (that is, the substantial space inside the
storage body, in which the powder can move around).
[0054] The amount of the sulfide-based solid electrolyte added is
not particularly limited. It is preferably 5 to 25 parts by mass,
with respect to 100 parts by mass of the active material particles
or 100 parts by mass of the composite particles.
[0055] The production method of the present invention is
advantageous in that it can offer cost reduction since it is a dry
mixing method that does not need a dispersion medium, etc.
(1) Active Material Particles
[0056] The active material particles are not particularly limited,
as long as they can serve as an electrode active material, more
specifically, as long as they can occlude and/or release ions such
as lithium ions.
[0057] Examples of cathode active material particles include:
layered active materials such as LiCoO.sub.2, LiNiO.sub.2,
LiCo.sub.1/3Ni.sub.1/3Mn.sub.1/3O.sub.2, LiVO.sub.2 and
LiCrO.sub.2; spinel-type active materials such as
LiMn.sub.2O.sub.4, Li (Ni.sub.0.25Mn.sub.0.75).sub.2O.sub.4,
LiCoMnO.sub.4 and Li.sub.2NiMn.sub.3O.sub.8; olivine-type active
materials such as LiCoPO.sub.4, LiMnPO.sub.4 and LiFePO.sub.4; and
NASICON-type active materials such as
Li.sub.3V.sub.2P.sub.3O.sub.12. Of them, preferred are those which
contain at least any one of a cobalt element, a nickel element and
a manganese element, and which further contain a lithium element
and an oxygen element, that is, LiCoO.sub.2, LiNiO.sub.2,
LiCo.sub.1/3Ni.sub.1/3Mn.sub.1/3O.sub.2, LiMn.sub.2O.sub.4,
Li(Ni.sub.0.2.5Mn.sub.0.75).sub.2O.sub.4, LiCoMnO.sub.4,
Li.sub.2NiMn.sub.3O.sub.8, LiCoPO.sub.4 and LiMnPO.sub.4. Of them,
LiNi.sub.1/3Co.sub.1/3Mn.sub.1/3O.sub.2 is particularly
preferred.
[0058] Examples of anode active material particles include:
carbonaceous materials such as mesocarbon microbeads (MCMB),
graphite, highly oriented pyrolytic graphite (HOPG), hard carbon
and soft carbon; oxides such as Nb.sub.2O.sub.5,
Li.sub.4Ti.sub.5O.sub.12 and SiO; lithium metals (Li); lithium
alloys such as LiM (where M is Sn, Si, Al, Ge, Sb, P or the like);
and metals such as In, Al, Si and Sn. Of them, carbonaceous
materials such as graphite, highly oriented pyrolytic graphite
(HOPG), hard carbon and soft carbon are preferably used.
[0059] In the present invention, there is no clear distinction
between the cathode active material and the anode active material.
A battery with a desired voltage can be constituted by comparing
the charge-discharge potentials of two kinds of compounds and using
one with a noble potential in the cathode and one with a base
potential in the anode.
[0060] In the present invention, the active material particles can
be single-crystal particles of an active material, or they can be
polycrystalline active material particles in which active material
single crystals are bound to each other at the crystal plane
level.
[0061] In the present invention, the average particle diameter of
the active material particles is not particularly limited, as long
as it is less than the average particle diameter of the target
composite active material powder. The average particle diameter of
the active material particles is preferably 0.1 to 30 .mu.m. When
the active material particles are polycrystalline active material
particles in which active material single crystals are bound to
each other, the average particle diameter of the active material
particles means the average particle diameter of the
polycrystalline active material particles.
[0062] In the present invention, the average particle diameter of
the particles is calculated by a general method. An example of the
method for calculating the average particle diameter of the
particles is as follows. First, for a particle shown in an image
taken at an appropriate magnitude (e.g., 50,000.times. to
1,000,000.times.) with a transmission electron microscope
(hereinafter referred to as TEM) or a scanning electron microscope
(hereinafter referred to as SEM), the diameter is calculated on the
assumption that the particle is spherical. Such a particle diameter
calculation by TEM or SEM observation is carried out on 200 to 300
particles of the same type, and the average of the particles is
determined as the average particle diameter.
(2) Composite Particles
[0063] In the present invention, the composite particles are
particles obtained by coating the surfaces of the active material
particles with the oxide-based solid electrolyte. By disposing the
oxide-based solid electrolyte between the sulfide-based solid
electrolyte and the active material particles, a deterioration in
reaction, which is due to a contact between the sulfide-based solid
electrolyte and the active material particles, can be
inhibited.
[0064] The active material particles contained in the composite
particles are preferably particles which contain at least any one
of a cobalt element, a nickel element and a manganese element, and
which further contain a lithium element and an oxygen element. In
particular, preferred are LiCoO.sub.2, LiNiO.sub.2,
LiCo.sub.1/3Ni.sub.1/3Mn.sub.1/3O.sub.2 LiMn.sub.2O.sub.4,
Li(Ni.sub.0.25Mn.sub.0.75).sub.2O.sub.4, LiCoMnO.sub.4,
Li.sub.2NiMn.sub.3O.sub.8, LiCoPO.sub.4 and LiMnPO.sub.4.
Particularly preferred is
LiNi.sub.1/3CO.sub.1/3Mn.sub.1/3O.sub.2.
[0065] The oxide-based solid electrolyte contained in the composite
particles is not particularly limited, as long as it contains an
oxygen element (O) and it has chemical affinity for the active
material particles to the extent that it can coat at least part of
the surface of each active material particle.
[0066] Examples of the oxide-based solid electrolyte include those
represented by the general formula Li.sub.xAO.sub.y (where A is B,
C, Al, Si, P, 5, Ti, Zr, Nb, Mo, Ta or W, and x and y are positive
integers). In particular, there may be mentioned Li.sub.3BO.sub.3,
LiBO.sub.2, Li.sub.2CO.sub.3, LiAlO.sub.2, Li.sub.4SiO.sub.4,
Li.sub.2SiO.sub.3, Li.sub.3PO.sub.4, Li.sub.2TiO.sub.3,
Li.sub.4Ti.sub.5O.sub.12, Li.sub.2Ti.sub.2O.sub.5,
Li.sub.2ZrO.sub.3, LiNbO.sub.3, Li.sub.2MoO.sub.4,
Li.sub.2WO.sub.4, etc. Also, there may be mentioned
Li.sub.2O--B.sub.2O.sub.3-P.sub.2O.sub.5, Li.sub.2O--SiO.sub.2,
Li.sub.2O--B.sub.2O.sub.3, Li.sub.2O--B.sub.2O.sub.3-ZnO, etc. Of
them, LiNbO.sub.3 is particularly preferably used.
[0067] The thickness of the oxide-based solid electrolyte layer
coating the active material particles is preferably such a
thickness that does not cause a reaction between the sulfide-based
solid electrolyte and the active material particles. For example,
it is preferably in a range of 0.1 to 100 nm, more preferably in a
range of 1 to 20 nm.
[0068] The oxide-based solid electrolyte layer is needed to coat
40% or more of the surface of each active material particle.
Preferably, the oxide-based solid electrolyte layer coats a larger
surface area of each active material particle. More preferably, the
layer coats all of the surface of each active material particle. In
particular, the coating rate is preferably 70% or more, more
preferably 90% or more.
[0069] Examples of methods for forming the oxide-based solid
electrolyte layer on the surfaces of the active material particles
include a tumbling/fluidizing coating method (sol-gel method), a
mechanofusion method, a chemical vapor deposition (CVD) method and
a physical vapor deposition (PVD) method. As a method for measuring
the thickness of the oxide-based solid electrolyte layer, there may
be mentioned TEM, for example. As a method for measuring the
coating rate of the oxide-based solid electrolyte layer, there may
be mentioned TEM and X-ray photoelectron spectroscopy (XPS), for
example.
(3) Sulfide-Based Solid Electrolyte
[0070] The sulfide-based solid electrolyte used in the present
invention is not particularly limited, as long as it contains a
sulfur element (S); it has chemical affinity for the
above-mentioned active material particles or composite particles to
the extent that it can coat the surfaces of the active material
particles or composite particles; and it has ion conductivity.
[0071] The thickness of the sulfide-based solid electrolyte layer
coating the surfaces of the active material particles or composite
particles is preferably in a range of 0.1 to 1000 nm, more
preferably in a range of 1 to 500 nm, for example.
[0072] The sulfide-based solid electrolyte layer is needed to coat
40% or more of the surface of each active material particle or
composite particle. Preferably, the sulfide-based solid electrolyte
layer coats a larger surface area of each particle. More
preferably, the sulfide-based solid electrolyte layer coats all of
the surface of each active material particle or composite particle.
In particular, the coating rate is preferably 70% or more, more
preferably 90% or more. The sulfide-based solid electrolyte coating
state can be qualitatively confirmed by TEM, SEM, etc.
[0073] The form of the sulfide-based solid electrolyte used for
mixing/kneading is not particularly limited. Preferred is a
particle form.
[0074] In the case where the composite active material powder of
the present invention is used in an all-solid-state lithium
battery, as the sulfide-based solid electrolyte, there may be
mentioned Li.sub.2S--SiS.sub.2-based solid electrolytes,
Li.sub.2S--P.sub.2S.sub.3-based solid electrolytes,
Li.sub.2S--P.sub.2S.sub.5-based solid electrolytes,
Li.sub.2S--GeS.sub.2-based solid electrolytes,
Li.sub.2S--B.sub.2S.sub.3-based solid electrolytes,
Li.sub.3PO.sub.4-P.sub.2S.sub.5-based solid electrolytes, and
Li.sub.4SiO.sub.4-Li.sub.2S--SiS.sub.2-based solid electrolytes,
for example. More specifically, there may be mentioned
Li.sub.2S--P.sub.2S.sub.5, Li.sub.2S--P.sub.2S.sub.3,
Li.sub.2S--P.sub.2S.sub.3-P.sub.2S.sub.5, Li.sub.2S--SiS.sub.2,
Li.sub.2S--P.sub.2S.sub.5-LiI,
LiI--Li.sub.2S--SiS.sub.2-P.sub.2S.sub.5,
LiI--LiBr--Li.sub.2S--P.sub.2S.sub.5,
LiI--LiBr--Li.sub.2S--SiS.sub.2-P.sub.2S.sub.5,
Li.sub.2S--SiS.sub.2-Li.sub.4SiO.sub.4,
Li.sub.2S--SiS.sub.2-Li.sub.3PO.sub.4, Li.sub.2S--GeS.sub.2,
Li.sub.3PS.sub.413 Li.sub.4GeS.sub.4,
LiGe.sub.0.25P.sub.0.75S.sub.4, Li.sub.2S--B.sub.2S.sub.3,
Li.sub.3.4P.sub.0.6Si.sub.0.4S.sub.4,
Li.sub.3.25P.sub.0.25Ge.sub.0.76S.sub.4,
Li.sub.4-xGe.sub.1-XP.sub.XS.sub.4 and Li.sub.7P.sub.3S.sub.11. Of
them, preferred is Li.sub.2S--P.sub.2S.sub.5-LiI.
[0075] The sulfide-based solid electrolyte can be a sulfide glass
or a crystallized sulfide glass obtained by heating a sulfide
glass.
[0076] FIG. 4 is a schematic sectional view of an embodiment of the
composite active material powder provided by the present invention.
The purpose of FIG. 4 is to qualitatively explain the material
coating state in an embodiment, and it is not a view that
qualitatively reflects the particle size of the actual solid
electrolyte, the coating state of the solid electrolyte, the
thickness of the solid electrolyte layer, etc.
[0077] As shown in FIG. 4, a composite active material powder 30
contains composite particles, in which all of the surfaces of
active material particles 31 are coated with an oxide-based solid
electrolyte layer 32, and a sulfide-based solid electrolyte layer
33, with which all of the surfaces of the composite particles is
coated.
[0078] The composite active material powder provided by the present
invention can be used in electrode active material layers (cathode
and anode active material layers) and is preferably used in the
electrode active material layers of an all-solid-state battery.
This is because electrode active material layers with excellent
electron conductivity and large charge-discharge capacity can be
obtained.
[0079] Examples of methods for forming electrode active material
layers include a method for compression molding an electrode
mixture that contains the composite active material powder. For
example, an all-solid-state battery can be produced by stacking a
cathode mixture and an anode mixture through a solid electrolyte
layer.
[0080] The method for producing the electrode mixture is not
particularly limited. For example, it can be produced by mixing the
composite active material powder, an electroconductive material and
a binder at a desired ratio.
[0081] The content of the composite active material powder in the
electrode mixture is preferably in a range of 10 to 99% by mass,
for example.
[0082] The electroconductive material is not particularly limited,
as long as it can increase the electron conductivity of
electrodes.
[0083] Examples of the electroconductive material include acetylene
black, Ketjen Black and carbon fibers. The content of the
electroconductive material in the electrode mixture varies
depending on the type of the electroconductive material. It is
generally in a range of 1 to 30% by mass.
[0084] As needed, the electrode mixture can contain a binder.
Examples of the binder include fluorine resins such as
polyvinylidene fluoride (PVdF) and polytetrafluoroethylene (PTFE),
and elastic resins such as butadiene rubber (BR). No particular
limitation is imposed on the elastic resins, and a hydrogenated
butadiene rubber or a hydrogenated butadiene rubber in which a
functional group is introduced in a terminal thereof, can be
preferably used. They can be used alone or in combination of two or
more kinds. The content of the binder in the electrode mixture is
needed to be an amount that can fix the cathode active material,
etc., and it is preferably small. The binder content is generally
in a range of 1 to 10% by mass.
[0085] The method for mixing them is not particularly limited and
can be wet mixing or dry mixing.
[0086] In the case of wet mixing, for example, there may be
mentioned a method in which the composite active material powder,
the electroconductive material, the sulfide-based solid electrolyte
particles, the binder and a dispersion medium are mixed to produce
a slurry, and the slurry is dried. As the dispersion medium, there
may be mentioned butyl butyrate, butyl acetate, dibutyl ether,
heptane, etc.
[0087] In the case of dry mixing, for example, there may be
mentioned a method in which the composite active material powder,
the electroconductive material, the sulfide-based solid electrolyte
particles and the binder are mixed with a mortar or the like.
[0088] A current collector can be provided to the electrode active
material layer formed from the electrode mixture. The structure and
form of the current collector and the material therefor are not
particularly limited, as long as the current collector has desired
electron conductivity. As the material for the current collector,
for example, there may be mentioned gold, silver, palladium, copper
and nickel.
[0089] The composite active material powder provided by the present
invention can be used in many types of batteries, in addition to
lithium secondary batteries, depending on the materials used
therefor (electrode active material, solid electrolyte, etc.)
EXAMPLES
Example 1
[0090] First, composite particles in which
LiNi.sub.1/3Co.sub.1/3Mn.sub.1/3O.sub.2 particles (active material
particles) are coated with LiNbO.sub.3 (oxide-based solid
electrolyte) were prepared (average particle diameter 6 .mu.m).
[0091] Next, 20 g of the composite particles and 4 g of
60Li.sub.2S-2OP.sub.2S.sub.5-20LiI particles (sulfide-based solid
electrolyte, average particle diameter 0.8 .mu.m) were put into a
dry mixing/kneading machine (product name: NOB-MINI; manufactured
by: Hosokawa Micron Corporation) and mixed and kneaded for 10
minutes under the following conditions, thereby producing a
composite active material powder.
[0092] Thickness of each blade: 6 mm
[0093] Width of the end surface of the end part of each blade: 1
mm
[0094] Length of the end part of each blade: 5.0 mm
[0095] Total length of each blade: 18.9 mm
[0096] Diameter of the rotating shaft of a rotating body: 50 mm
[0097] Clearance: 1 mm
[0098] Inclined angle: 45.degree.
[0099] Peripheral speed: 18.5 m/s
Example 2
[0100] A composite active material powder was produced in the same
manner as Example 1, except that the width of the end surface of
the end part of each blade was changed to 2.5 mm, and the thickness
of each blade was changed to 7.5 mm.
Example 3
[0101] A composite active material powder was produced in the same
manner as Example 1, except that the width of the end surface of
the end part of each blade was changed to 5 mm, and the thickness
of each blade was changed to 10 mm.
Comparative Example 1
[0102] First, composite particles in which
LiNi.sub.1/3Co.sub.1/3Mn.sub.1/3O.sub.2 particles (active material
particles) are coated with LiNbO.sub.3 (oxide-based solid
electrolyte) were prepared (average particle diameter 6 .mu.m).
[0103] Next, 20 g of the composite particles and 4 g of
60Li.sub.2S-20P.sub.2S.sub.5-20LiI particles (sulfide-based solid
electrolyte, average particle diameter 0.8 .mu.m) were subjected to
dry mixing (spatula mixing) for 10 minutes, thereby producing a
composite active material powder.
Comparative Example 2
[0104] A composite active material powder was produced in the same
manner as Example 1, except that the thickness of each blade was
changed to 1 mm, and any tapered section was not formed at the end
part of each blade (that is, both the thickness of each blade and
the width of the end surface of the end part of each blade were set
to 1 mm).
Comparative Example 3
[0105] A composite active material powder was produced in the same
manner as Example 1, except that the thickness of each blade was
changed to 2.5 mm, and any tapered section was not formed at the
end part of each blade (that is, both the thickness of each blade
and the width of the end surface of the end part of each blade were
set to 2.5 mm).
Comparative Example 4
[0106] A composite active material powder was produced in the same
manner as Example 1, except that the thickness of each blade was
changed to 5 mm, and any tapered section was not formed at the end
part of each blade (that is, both the thickness of each blade and
the width of the end surface of the end part of each blade were set
to 5 mm).
Battery Production
[0107] Hereinafter, all-solid-state lithium secondary batteries
were produced using the composite active material powders of
Examples 1 to 3 and Comparative Examples 1 to 4 as a cathode active
material.
[0108] The composite active material powders were prepared as the
cathode active material; 60Li.sub.2S-20P.sub.2S.sub.5-20LiI
particles were prepared as a sulfide-based solid electrolyte;
vapor-grown carbon fibers (VGCF) were prepared as an
electroconductive material; and PVdF was prepared as a binder. Each
of the cathode active materials, the sulfide-based solid
electrolyte, the electroconductive material and the binder were
prepared at the following ratio: cathode active
material/sulfide-based solid electrolyte/electroconductive
material/binder=81.3% by mass/16.6% by mass/1.3% by mass/0.8% by
mass. Then, 13 g of butyl butyrate was added thereto, and the
mixture was subjected to wet mixing for 2 minutes with an
ultrasonic homogenizer, thereby preparing a cathode mixture.
[0109] As the raw material for a separator layer (solid electrolyte
layer), 60Li.sub.2S-20P.sub.2S.sub.5-20LiI particles (sulfide-based
solid electrolyte) were prepared.
[0110] Natural black lead was prepared as an anode active material;
60Li.sub.2S-20P.sub.2S.sub.5-20LiI particles were prepared as a
sulfide-based solid electrolyte; and PVdF was prepared as a binder.
The anode active material, the sulfide-based solid electrolyte and
the binder were prepared at the following ratio: anode active
material/sulfide-based solid electrolyte/binder=54.8% by mass/43.4%
by mass/1.8% by mass. Then, 13 g of butyl butyrate was added
thereto, and the mixture was subjected to wet mixing for 2 minutes
with an ultrasonic homogenizer, thereby preparing an anode
mixture.
[0111] First, as the separator layer, a pressed powder was formed
by pressing the 60Li.sub.2S-20P.sub.2S.sub.5-20LiI particles. Next,
the cathode mixture was disposed on one surface of the pressed
powder, and the anode mixture was disposed on the other surface.
The resultant was subjected to flat pressing at a press pressure of
6 ton/cm.sup.2 (.apprxeq.588 MPa) for a pressing time of 1 minute,
thereby obtaining a laminate. For the laminate thus obtained, the
thickness of the cathode mixture layer was 30 .mu.m; the thickness
of the anode mixture layer was 45 .mu.m; and the thickness of the
separator layer was 300 .mu.m. The laminate was held at a pressure
of 0.2 N in the laminating direction, thereby producing an
all-solid-state lithium secondary battery.
[0112] Hereinafter, the all-solid-state lithium secondary batteries
in which the composite active material powders of Examples 1 to 3
and Comparative Examples 1 to 4 were used as a raw material, are
referred to as all-solid-state lithium secondary batteries of
Examples 1 to 3 and Comparative Examples 1 to 4.
Measurement of Internal Resistance of All-Solid-State Lithium
Secondary Batteries
[0113] For the all-solid-state lithium secondary batteries of
Examples 1 to 3 and Comparative Examples 1 to 4, the internal
resistance was measured by the 10s-DCIR method. Details of the
measurement method are as follows.
[0114] OCV potential: 3.52 V
[0115] Current density: 15.7 mA/cm.sup.2
[0116] The internal resistance was calculated by Ohm's law, from
the overvoltage and current value which were measured 10 seconds
after discharge.
[0117] The internal resistances of the all-solid-state lithium
secondary batteries of Examples 1 to 3 and Comparative Examples 1
to 4 are shown in Table 1.
TABLE-US-00001 TABLE 1 Width of end Length Inclined Blade surface
of end of end Internal Tapered angle thickness part part resistance
section (.degree.) (mm) (mm) (mm) (.OMEGA./cm.sup.2) Example 1
Formed 45 6 1 5 100.1 Example 2 Formed 45 7.5 2.5 5 81 Example 3
Formed 45 10 5 5 72.8 Comparative -- -- -- -- -- 149.8 Example 1
Comparative Not formed -- 1 1 -- 120.2 Example 2 Comparative Not
formed -- 2.5 2.5 -- 104.7 Example 3 Comparative Not formed -- 5 5
-- 110.3 Example 4
[0118] As shown in Table 1, the internal resistances of the
all-solid-state lithium secondary batteries of Examples 1 to 3 and
Comparative Examples 1 to 4 are as follows: 100.1 .OMEGA./cm.sup.2
in Example 1; 81.0 .OMEGA./cm.sup.2 in Example 2; 72.8
.OMEGA./cm.sup.2 in Example 3; 149.8 .OMEGA./cm.sup.2 in
Comparative Example 1; 120.2 .OMEGA./cm.sup.2 in Comparative
Example 2; 104.7 .OMEGA./cm.sup.2 in Comparative Example 3; and
110.3 .OMEGA./cm.sup.2 in Comparative Example 4.
[0119] As shown in Table 1, the internal resistances of the
all-solid-state lithium secondary batteries of Examples 1 to 3 are
to 51% smaller than the internal resistance of Comparative Example
1 in which the device for producing the composite active material
powder was not used.
[0120] Also, the internal resistances of the all-solid-state
lithium secondary batteries of Examples 1 to 3 are 4 to 39% smaller
than those of all-solid-state lithium secondary batteries of
Comparative Examples 2 to 4 in which the blades that do not have a
tapered section at the end part thereof, were used.
[0121] As the result of comparing Example 1 and Comparative Example
2, in both of which the composite active material powder was
produced under the condition that the width of the end surface of
the end part of each blade is 1 mm, the internal resistance of the
all-solid-state lithium secondary battery of Example 1 is 17%
smaller than the all-solid-state lithium secondary battery of
Comparative Example 2. As the result of Example 2 and Comparative
Example 3, in both of which the composite active material powder
was produced under the condition that the width of the end surface
of the end part of each blade is 2.5 mm, the internal resistance of
the all-solid-state lithium secondary battery of Example 2 is 23%
smaller than that of the all-solid-state lithium secondary battery
of Comparative Example 3. As the result of comparing Example 3 and
Comparative Example 4, in both of which the composite active
material powder was produced under the condition that the width of
the end surface of the end part of each blade is 5 mm, the internal
resistance of the all-solid-state lithium secondary battery of
Example 3 is 34% smaller than that of the all-solid-state lithium
secondary batter of Comparative Example 4. Therefore, it is clear
that in the case where the widths of the end surfaces of the end
parts of the blades are the same, the internal resistances becomes
17 to 34% smaller, depending on the presence of the tapered
section.
[0122] As the result of comparing Examples 1 to 3, it is clear that
the internal resistance of the all-solid-state lithium secondary
battery of Example 3 is the smallest, and the internal resistance
of the all-solid-state lithium secondary battery of Example 2 is
the smallest next to Example 3.
[0123] Therefore, it is clear that by having the tapered section
and increasing the width of the end surface of the end part of each
blade, the coating efficiency is increased, and the internal
resistance of the all-solid-state lithium secondary battery is
decreased.
[0124] From the above, it is clear that the composite active
material powder produced using the device for producing the
composite active material powder according to the present
invention, has a function to reduce the internal resistance of a
battery more than conventional composite active material
powders.
REFERENCE SIGNS LIST
[0125] In the accompanying drawings,
[0126] 11. Storage body
[0127] 12. Inner wall surface
[0128] 13. Rotating body
[0129] 14. Rotating shaft
[0130] 15. Blade
[0131] 16. Bearing
[0132] 17. Motor
[0133] 19. End part of blade
[0134] 20. Inclined angle of tapered section
[0135] 21. End surface of end part of blade
[0136] 22. Clearance
[0137] 23. Width of end surface of end part of blade
[0138] 24. Thickness of blade
[0139] 25. Length of end part of blade
[0140] 26. Total length of blade
[0141] 27. Diameter of rotating shaft of rotating body
[0142] 28. Inclined surface of tapered section
[0143] 30. Composite active material powder
[0144] 31. Active material particle
[0145] 32. Oxide-based solid electrolyte layer
[0146] 33. Sulfide-based solid electrolyte layer
[0147] 100. Device
* * * * *