U.S. patent application number 12/385851 was filed with the patent office on 2009-10-29 for solid lithium secondary cell, and production method therefor.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. Invention is credited to Yasushi TSUCHIDA.
Application Number | 20090269670 12/385851 |
Document ID | / |
Family ID | 51494667 |
Filed Date | 2009-10-29 |
United States Patent
Application |
20090269670 |
Kind Code |
A1 |
TSUCHIDA; Yasushi |
October 29, 2009 |
Solid lithium secondary cell, and production method therefor
Abstract
A solid electrolyte layer and electrode layers are formed within
an electrically insulating frame part, and current collecting
plates are held by the electrically insulating frame part. Since
the current collecting plates are held by the frame part, the
shifting or coming-apart of the current collecting plates can be
restrained. In order to cause the current collecting plates to be
held by the frame part, a powder of material of the electrode layer
is filled in between the frame part and the current collecting
plates.
Inventors: |
TSUCHIDA; Yasushi;
(Susono-shi, JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 320850
ALEXANDRIA
VA
22320-4850
US
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
Toyota-shi
JP
|
Family ID: |
51494667 |
Appl. No.: |
12/385851 |
Filed: |
April 22, 2009 |
Current U.S.
Class: |
429/231.95 ;
29/623.1 |
Current CPC
Class: |
H01M 4/13 20130101; H01M
10/052 20130101; Y02T 10/70 20130101; H01M 10/0585 20130101; Y02E
60/10 20130101; Y10T 29/49108 20150115; H01M 4/02 20130101 |
Class at
Publication: |
429/231.95 ;
29/623.1 |
International
Class: |
H01M 4/40 20060101
H01M004/40; H01M 10/00 20060101 H01M010/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 24, 2008 |
JP |
2008-114360 |
Claims
1. A solid lithium secondary cell comprising: an electrically
insulating tubular insulating frame; a solid electrolyte layer
formed within the insulating frame; an electrode layer that is
layered on at least one of surfaces of the solid electrolyte layer,
and that is formed within the insulating frame; and a
current-collecting member that is layered on the electrode layer,
and that is held by the insulating frame.
2. The solid lithium secondary cell according to claim 1, wherein
the electrode layer includes: a positive electrode layer that is
layered on one of sides of the solid electrolyte layer within the
insulating frame, and that is formed by compressing a powder, and a
negative electrode layer that is layered on another side of the
solid electrolyte layer within the insulating frame, and that is
formed by compressing a powder, and wherein the current-collecting
member includes: a positive electrode current-collecting member
that is layered on the positive electrode layer, and that is held
by the insulating frame; and a negative electrode
current-collecting member that is layered on the negative electrode
layer, and that is held by the insulating frame.
3. The solid lithium secondary cell according to claim 1, wherein:
the current-collecting member is disposed so that at least a
portion of the current-collecting member is within the insulating
frame; and a powder of a material of the electrode layer that
contacts the current-collecting member fills a space between the
insulating frame and the outer peripheral side surface of the
current-collecting member.
4. The solid lithium secondary cell according to claim 3, wherein
an outside diameter of the current-collecting member is smaller
than an inside diameter of the insulating frame by a length ranging
from 200 micrometers to 1200 micrometers.
5. A production method for a solid lithium secondary cell that
includes: an electrically insulating tubular insulating frame; a
solid electrolyte layer formed within the insulating frame; an
electrode layer that is layered on at least one of surfaces of the
solid electrolyte layer, and that is formed within the insulating
frame by pressing a powder of a material of the electrode layer;
and a current-collecting member that is layered on the electrode
layer, at least a portion of the current-collecting member being
disposed within the insulating frame, the production method being
comprising pressing the material of the electrode layer by applying
force to the current-collecting member, wherein when the material
is pressed, pressing is performed so that the current-collecting
member moves relative to the insulating frame.
6. The production method according to claim 5, wherein a distance
that the current-collecting member moves relative to the insulating
frame is greater than or equal to one-fifth of a thickness of the
current-collecting member, and is less than or equal to the
thickness of the current-collecting member.
7. A production method according to claim 5, wherein the electrode
layer includes: a positive electrode layer that is formed on one of
sides of the solid electrolyte layer within the insulating frame;
and a negative electrode layer that is formed on another side of
the solid electrolyte layer within the insulating frame, and
wherein the current-collecting member includes: a positive
electrode current-collecting member that is layered on the positive
electrode layer, and that is held by the insulating frame; and a
negative electrode current-collecting member that is layered on the
negative electrode layer, and that is held by the insulating
frame.
8. The production method according to claim 5, wherein an outside
diameter of the current-collecting member is smaller than an inside
diameter of the insulating frame by a length ranging from 200
micrometers to 1200 micrometers.
9. A production method for a solid lithium secondary cell,
comprising: making an electrolyte-electrode layered assembly that
has a layered structure that includes an electrode layer and a
solid electrolyte layer, by placing a powder of a material of the
electrode layer, and a powder of a material of the solid
electrolyte layer, in an electrically insulating tubular insulating
frame, and tentatively pressing the powder of the material of the
electrode layer, and the powder of the material of the solid
electrolyte layer, layering the current-collecting member on the
electrolyte-electrode layered assembly so that at least a portion
of the current-collecting member is disposed within the insulating
frame; and definitively pressing the electrolyte-electrode layered
assembly on which the current-collecting member has been layered,
in such a manner that the current-collecting member moves relative
to the insulating frame.
10. The production method according to claim 9, wherein a distance
that the current-collecting member moves relative to the insulating
frame is greater than or equal to one-fifth of a thickness of the
current-collecting member, and is less than or equal to the
thickness of the current-collecting member.
11. A production method according to claim 9, wherein the electrode
layer includes: a positive electrode layer that is formed on one of
sides of the solid electrolyte layer within the insulating frame;
and a negative electrode layer that is formed on another side of
the solid electrolyte layer within the insulating frame, and
wherein the current-collecting member includes: a positive
electrode current-collecting member that is layered on the positive
electrode layer, and that is held by the insulating frame; and a
negative electrode current-collecting member that is layered on the
negative electrode layer, and that is held by the insulating
frame.
12. The production method according to claim 9, wherein an outside
diameter of the current-collecting member is smaller than an inside
diameter of the insulating frame by a length ranging from 200
micrometers to 1200 micrometers.
13. A production method for a solid lithium secondary cell that
includes: an electrically insulating tubular insulating frame; a
solid electrolyte layer formed within the insulating frame; an
electrode layer that is layered on at least one of surfaces of the
solid electrolyte layer, and that is formed within the insulating
frame by pressing a powder of a material of the electrode layer;
and a current-collecting member that is layered on the electrode
layer, at least a portion of the current-collecting member being
disposed within the insulating frame, the production method being
comprising pressing the material of the electrode layer by applying
force to the current-collecting member, wherein when the material
is pressed, pressing is performed so that the material of the
electrode layer gets in between the insulating frame and an outer
periphery of the current-collecting member as a layer of the powder
of the material of the electrode layer plastically deforms.
14. A production method according to claim 13, wherein the
electrode layer includes: a positive electrode layer that is formed
on one of sides of the solid electrolyte layer within the
insulating frame; and a negative electrode layer that is formed on
another side of the solid electrolyte layer within the insulating
frame, and wherein the current-collecting member includes: a
positive electrode current-collecting member that is layered on the
positive electrode layer, and that is held by the insulating frame;
and a negative electrode current-collecting member that is layered
on the negative electrode layer, and that is held by the insulating
frame.
15. The production method according to claim 13, wherein an outside
diameter of the current-collecting member is smaller than an inside
diameter of the insulating frame by a length ranging from 200
micrometers to 1200 micrometers.
16. A production method for a solid lithium secondary cell,
comprising: making an electrolyte-electrode layered assembly that
has a layered structure that includes an electrode layer, and a
solid electrolyte layer, by placing a powder of a material of the
electrode layer, and a powder of a material of the solid
electrolyte layer, in an electrically insulating tubular insulating
frame, and tentatively pressing the powder of the material of the
electrode layer, and the powder of the material of the solid
electrolyte layer; layering the current-collecting member on the
electrolyte-electrode layered assembly so that at least a portion
of the current-collecting member is disposed within the insulating
frame; and definitively pressing the electrolyte-electrode layered
assembly on which the current-collecting member has been layered,
in such a manner that the material of the electrode layer gets in
between the insulating frame and an outer periphery of the
current-collecting member as the electrode layer plastically
deforms.
17. A production method according to claim 16, wherein the
electrode layer includes: a positive electrode layer that is formed
on one of sides of the solid electrolyte layer within the
insulating frame; and a negative electrode layer that is formed on
another side of the solid electrolyte layer within the insulating
frame, and wherein the current-collecting member includes: a
positive electrode current-collecting member that is layered on the
positive electrode layer, and that is held by the insulating frame;
and a negative electrode current-collecting member that is layered
on the negative electrode layer, and that is held by the insulating
frame.
18. The production method according to claim 16, wherein an outside
diameter of the current-collecting member is smaller than an inside
diameter of the insulating frame by a length ranging from 200
micrometers to 1200 micrometers.
Description
INCORPORATION BY REFERENCE
[0001] The disclosure of Japanese Patent Application No.
2008-114360 filed on Apr. 24, 2008 including the specification,
drawings and abstract is incorporated herein by reference in its
entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to a solid-type lithium secondary
cell, and a production method for the solid-type lithium secondary
cell.
[0004] 2. Description of the Related Art
[0005] Lithium secondary cells are high in energy density, and are
capable of outputting high voltage, and are therefore expected as
power sources of batteries of electric motor vehicles, hybrid motor
vehicles, etc., or as power sources of portable electric appliances
such as notebook personal computers, cellular phones, etc. Among
lithium secondary cells, a solid lithium secondary cell that
employs a solid electrolyte instead of a liquid electrolyte has
recently been proposed. The solid lithium secondary cell is
considered excellent in safety and productivity, and is expected as
a future secondary cell. The solid lithium secondary cell has a
structure in which a positive electrode layer, a solid electrolyte
layer, and a negative electrode layer are layered in that order,
and current collecting plates are attached to both sides of the
layered unit Generally, the solid lithium secondary cell is formed
by a powder molding method. Specifically, a positive electrode
material, an electrolyte material and a negative electrode material
are placed in a mold, and are pressed to make a pellet in which
electrode layers and electrolyte layer form a layered structure
(hereinafter, sometimes referred to as "electrolyte-electrode
layered assembly"). After the pellet is removed from the mold,
current collecting plates are attached thereto, whereby a cell is
produced.
[0006] In the case where a solid lithium secondary cell is produced
in the foregoing manner, when the pellet is removed from the mold,
a side surface of the pellet rubs on an internal surface of the
mold, so that electrode material adheres to a side surface of the
electrolyte layer, giving rise to a problem of internal
short-circuit of the cell. To overcome this problem, a solid
lithium secondary cell in which an electrically insulating frame
part is employed, and electrode layers and an electrolyte layer are
integrally formed within the frame part has been proposed. (see
Japanese Patent Application Publication No. 9-35724
(JP-A-9-35724)). According to this solid lithium secondary cell,
the rubbing of a side surface of the pellet does not occur, and
therefore the internal short circuit of the cell can be prevented.
Incidentally, in order to produce a cell, it is necessary to attach
current collecting plates to a layered assembly made up of a
positive electrode layer, an electrolyte layer, and a negative
electrode layer as described above. If a current collecting plate
falls apart from the electrolyte-electrode layered assembly, or the
adhesion area between a current collecting plate and the electrode
layer decreases, problems of productivity reduction, contact
resistance increase, etc. can occur Therefore, it is necessary to
devise some measures in order to fix the electrolyte-electrode
layered assembly and the current collecting plates.
SUMMARY OF THE INVENTION
[0007] The invention provides a solid lithium secondary cell that
employs an electrically insulating frame part and that is capable
of restraining the coming-apart of a current-collecting member from
the electrolyte-electrode layered assembly or reduction of the
contact area of a current-collecting member with the electrode
layer (hereinafter, referred to as "the coming-apart or the like"),
and also provides a production method for the solid lithium
secondary cell.
[0008] A first aspect of the invention is a solid lithium secondary
cell that includes: an electrically insulating tubular insulating
frame; a solid electrolyte layer formed within the insulating
frame; an electrode layer that is layered on at least one of
surfaces of the solid electrolyte layer, and that is formed within
the insulating frame; and a current-collecting member that is
layered on the electrode layer, and that is held by the insulating
frame.
[0009] A second aspect of the invention is a production method for
a solid lithium secondary cell that includes: an electrically
insulating tubular insulating frame; a solid electrolyte layer
formed within the insulating frame; an electrode layer that is
layered on at least one of surfaces of the solid electrolyte layer,
and that is formed within the insulating frame by pressing a powder
of a material of the electrode layer; and a current-collecting
member that is layered on the electrode layer, at least a portion
of the current-collecting member being disposed within the
insulating frame, the production method including the step of
pressing the material of the electrode layer by applying force to
the current-collecting member. In this step, when the material is
pressed, pressing is performed so that the current-collecting
member moves relative to the insulating frame.
[0010] A third aspect of the invention is a production method for a
solid lithium secondary cell, the production method including: the
step of making an electrolyte-electrode layered assembly that has a
layered structure that includes an electrode layer and a solid
electrolyte layer, by placing a powder of a material of the
electrode layer, and a powder of a material of the solid
electrolyte layer, in an electrically insulating tubular insulating
frame, and tentatively pressing the powder of the material of the
electrode layer, and the powder of the material of the solid
electrolyte layer; the step of layering the current-collecting
member on the electrolyte-electrode layered assembly so that at
least a portion of the current-collecting member is disposed within
the insulating frame; and the step of definitively pressing the
electrolyte-electrode layered assembly on which the
current-collecting member has been layered, in such a manner that
the current-collecting member moves relative to the insulating
frame.
[0011] A fourth aspect of the invention is a production method for
a solid lithium secondary cell that includes: an electrically
insulating tubular insulating frame; a solid electrolyte layer
formed within the insulating frame; an electrode layer that is
layered on at least one of surfaces of the solid electrolyte layer,
and that is formed within the insulating frame by pressing a powder
of a material of the electrode layer; and a current collecting
member that is layered on the electrode layer, at least a portion
of the current-collecting member being disposed within the
insulating frame. The production method includes the step of
pressing the material of the electrode layer by applying force to
the current-collecting member. In this step, when the material is
pressed, pressing is performed so that the material of the
electrode layer gets in between the insulating frame and an outer
periphery of the current-collecting member as a layer of the powder
of the material of the electrode layer plastically deforms.
[0012] A fifth aspect of the invention is a production method for a
solid lithium secondary cell which includes: the step of making an
electrolyte-electrode layered assembly that has a layered structure
that includes an electrode layer, and a solid electrolyte layer, by
placing a powder of a material of the electrode layer, and a powder
of a material of the solid electrolyte layer, in an electrically
insulating tubular insulating frame, and tentatively pressing the
powder for the electrode layer, and the powder for the solid
electrolyte layer, the step of layering the current-collecting
member on the electrolyte-electrode layered assembly so that at
least a portion of the current-collecting member is disposed within
the insulating frame; and the step of definitively pressing the
electrolyte-electrode layered assembly on which the
current-collecting member has been layered, in such a manner that
the material of the electrode layer gets in between the insulating
frame and an outer periphery of the current-collecting member as
the electrode layer plastically deforms.
[0013] According to the first aspect of the invention, since the
current-collecting member is hold by the frame part, the
coming-apart or the like of the current-collecting member can be
restrained.
[0014] Besides, the first aspect of the invention, a space between
the frame part and the current-collecting member is filled with the
powder of the material of the electrode layer. Therefore, by the
elastic force of the powder, the current-collecting member is fixed
to the insulating frame. Hence, the coming-apart or the like of the
current-collecting member can be effectively prevented. That is, in
this invention, the current-collecting member is held indirectly by
the insulating frame, via the powder of the electrode material.
[0015] Besides, according to the first aspect of the invention, a
gap into which the powder of the electrode material moves is formed
between the frame part and the current-collecting member, and the
current-collecting member is held by the elastic force of the
powder that fills the gap.
[0016] According to the second to fourth aspects of the invention,
when the definitive pressing is performed, the powder of the
electrode material gets in between the current-collecting member
and the frame part. Hence, a solid lithium secondary cell in which
the current-collecting member is held by the frame part via the
elastic force of the powder can be produced.
[0017] According to the fifth aspect of the invention, since a gap
into which the powder of the electrode material moves is formed
between the frame part and the current-collecting member, the
powder of the electrode material is more certainly forced to get in
between the frame part and the current-collecting member.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The foregoing and further features and advantages of the
invention will become apparent from the following description of
example embodiments with reference to the accompanying drawings,
wherein like numerals are used to represent like elements, and
wherein:
[0019] FIG. 1 is a perspective view of a solid cell of Embodiment 1
of the invention;
[0020] FIG. 2 is a sectional view of the solid cell of Embodiment
1;
[0021] FIG. 3 is a sectional view and a partial enlarged view of
the solid cell of Embodiment 1;
[0022] FIG. 4 is a diagram for describing a production method for
the solid cell of the Embodiment 1;
[0023] FIG. 5 is a diagram for describing the production method for
the solid cell of Embodiment 1;
[0024] FIG. 6 is a diagram for describing the production method for
the solid cell of Embodiment 1;
[0025] FIG. 7 is a diagram for describing the production method for
the solid cell of Embodiment 1; and
[0026] FIG. 8 is a perspective view of a modification of the solid
cell of Embodiment 1.
DETAILED DESCRIPTION OF EMBODIMENTS
[0027] Hereinafter, embodiments of the invention will be described
with reference to the drawings.
[0028] FIG. 1 is a perspective view of a solid lithium secondary
cell of Embodiment 1 of the invention. As shown in FIG. 1, the
solid lithium secondary cell 10 according to this embodiment is
equipped with an electrically insulating frame part 12
(hereinafter, termed the insulating frame 12). The insulating frame
12 is provided so as to entirely cover side surfaces of an
electrolyte layer, a positive electrode layer, and a negative
electrode layer of the solid lithium secondary cell 10, and so as
to partially cover a side surface of a negative electrode current
collecting plate 14, and a side surface of a positive electrode
current collecting plate 16 of the solid lithium secondary cell
10.
[0029] FIG. 2 is a sectional view of the solid lithium secondary
cell 10 of Embodiment 1. As shown in FIG. 2, the lithium secondary
cell 10 has a structure in which the current collecting plates 14
and 16 are attached to a layered assembly (electrolyte-electrode
layered assembly) made up of an electrolyte layer 20, a negative
electrode layer 22, and a positive electrode layer 24 (which,
hereinafter, will sometimes be referred to collectively as
"electrode layers"). The insulating frame 12 is disposed so as to
entirely cover the side surfaces of the electrolyte layer 20, and
the electrode layers 22 and 24, and so as to partially cover the
side surfaces of the current collecting plates 14 and 16. The
electrolyte layer and the electrode layers are all made of solid
substances, and are formed by pressing raw-material powders.
[0030] In this embodiment, the material of the electrolyte layer is
70Li.sub.2S-30P.sub.2S.sub.5, and the material of the positive
electrode layer is a mixture of 70Li.sub.2S-30P.sub.2S.sub.5, the
material of the electrolyte layer, and LiCoO.sub.2, which is a
positive electrode active material, and the material of the
negative electrode layer is a mixture of
70L.sub.2S-30P.sub.2S.sub.5, the material of the electrolyte layer,
and graphite, which is a negative electrode active material. In
this embodiment, 70Li.sub.2S-30P.sub.2S.sub.5 is used in the form
of a powder having an average particle diameter of 20 micrometers,
and LiCoO.sub.2 is used in the form of a powder having an average
particle diameter of 10 micrometers, and graphite is used in the
form of a powder having an average particle diameter of 10
micrometers. Besides, the insulating frame is constructed of an
electrically insulating resin. Besides, the current collecting
plate is a thin plate made of a stainless steel and having a
thickness of 300 micrometers.
[0031] FIG. 3 is a sectional view and a partial enlarged view of
the solid lithium secondary cell 10 of this embodiment. As shown in
FIG. 3, a gap 30 between the insulating frame 12 and the side
surface of the positive electrode current collecting plate 16 in
the solid lithium secondary cell 10 of this embodiment is filled
with a material that constitutes the positive electrode layer 24
(i.e., the positive electrode active material or the material of
the electrolyte layer). Likewise, a gap between the insulating
frame 12 and the negative electrode current collecting plate 14 is
filled with a material that constitutes the negative electrode
layer 22 (i.e., the negative electrode active material or the
material of the electrolyte layer).
[0032] In this embodiment, the gap 30 is set so that the width
thereof that is, the gap size, is 150 micrometers. Specifically,
the sizes of the insulating frame 12 and the positive electrode
current collecting plate 16 are determined so that the difference
between the inside diameter of the insulating frame 12 and the
outside diameter of the positive electrode current collecting plate
16 is 300 micrometers. Likewise, the size of the negative electrode
current collecting plate 14 is determined so that the difference
between the inside diameter of the insulating frame 12 and the
outside diameter of the negative electrode current collecting plate
14 is 300 micrometers. The gaps 30 between the insulating frame 12
and the current collecting plates 14 and 16 formed in this manner
are filled with the materials of the electrode layers 22 and 24,
respectively, as described above. In the solid lithium secondary
cell 10 of this embodiment, the current collecting plates 14 and 16
are held by the elastic force of the electrode materials that fills
the gaps between the insulating frame 12 and the current collecting
plates 14 and 16, and are fixed to the insulating frame 12. This
means, from another point of view, that the insulating frame 12
supports the current collecting plates 14 and 16 via the electrode
materials. Besides, it can also be considered that the current
collecting plate is fixed to the insulating frame by the elastic
force of the electrode materials.
[0033] With reference to FIG. 4 to FIG. 7, an example of a
production method for the solid lithium secondary cell of the
embodiment will be described. As shown in FIG. 4, an insulating
frame 50 is firstly set in a press apparatus 41 for cell
production.
[0034] Next, as shown in FIG. 5, 70Li.sub.2S-30P.sub.2S.sub.5,
which is the electrolyte material, is placed in the insulating
frame 50, and tentative pressing is performed to form an
electrolyte layer 52. Then, as shown in FIG. 6, a mixed material of
LiCoO.sub.2, which is a positive electrode active material, and
70Li.sub.2S-30P.sub.2S.sub.5, which is the electrolyte material, is
layered on one of the two sides of the electrolyte layer 52, and a
mixed material of graphite, which is the negative electrode active
material, and 70Li.sub.2S-30P.sub.2S.sub.5, which is the
electrolyte material, is layered on the other side of the
electrolyte layer 52, and then tentative pressing is performed. By
the tentative pressing in this manner, a layered assembly of a
positive electrode layer, an electrolyte layer and a negative
electrode layer (an electrolyte-electrode layered assembly) is
formed in the insulating frame 50. At this time, the tentative
pressing pressure is set so that the electrode layers will each be
compressed by about 100 micrometers by a definitive pressing
(described later).
[0035] Next, as shown in FIG. 7, current collecting plates are
attached to both sides of the electrolyte-electrode
layered-assembly. With the current collecting plates attached to
both sides of the electrolyte-electrode layered assembly, pressing
(definitive pressing) is performed by applying force to the current
collecting plate on both sides. The pressing is performed by
applying a force of 5 tons per square centimeter from both sides of
the layered assembly. The pressing herein is performed so that the
current collecting plates 60 and 62 move relative to the insulating
frame 50. Specifically, the pressing is performed so that each of
the current collecting plates 60 and 62 moves to the electrolyte
layer 52 within the insulating frame 50.
[0036] When the pressing is performed so that the current
collecting plates move relative to the insulating frame as
described above, the electrode layers plastically deform so that
the materials of the electrode layers enter the gaps between the
insulating frame 50 and the current collecting plates 60 and 62. In
other words, as the current collecting plates are displaced so as
to sink into the electrode layers while compressing the electrode
layers, the materials of the electrode layers are forced to fill
the gaps between the insulating frame 50 and the current collecting
plates 60 and 62. Then, the current collecting plates are held by
the elastic force of the materials of the electrode layers. In this
embodiment, the definitive pressing is performed so that each of
the current collecting plates having a thickness of 300 micrometers
moves a distance of 100 micrometers. In this manner, the materials
of the electrode layers are forced to get in between the insulating
frame and the side surfaces of the current collecting plates.
[0037] According to the solid lithium secondary cell of this
embodiment, since the current collecting plate is held by the
insulating frame, the coming-apart of the current collecting plates
or the like is restrained. The coming-apart of a current collecting
plate during production lowers the productivity, and the
coming-apart thereof after production makes the charging and
discharging difficult. However, according to the solid lithium
secondary cell of this embodiment, these troubles can be restrained
since the coming-apart of a current collecting plate can be
restrained. Besides, if the contact pressure or the contact area
between the electrode layer and the current collecting plates
declines although the coming-apart of a current collecting plate
does not occur, the contact resistance increases. According to the
all-solid lithium secondary cell of the invention, since movement
of the current collecting plates relative to the insulating frame
can be restrained, the weakening of the contact between the
electrode layer and the current collecting plates can also be
restrained.
[0038] Besides, according to the solid lithium secondary cell of
this embodiment, the sizes of the insulating frame and the current
collecting plates are determined so that the difference between the
inside diameter of the insulating frame and the outside diameter of
the current collecting plates is 300 micrometers. As described
above, since the average particle diameter of the materials of the
electrodes used in this embodiment is 10 to 20 micrometers,
sufficient amounts of the electrode materials to hold the current
collecting plates can be forced into the gaps between the
insulating frame and the side surfaces of the current collecting
plates if the size of the gaps is about 150 micrometers. Therefore,
the current collecting plates are held by the elastic force of the
electrode materials forced to fill the gaps between the insulating
frame and the current collecting plates.
[0039] Besides, since the electrode materials fill the gaps between
the insulating frame and the current collecting plates, the
electrode materials present in the electrode layer does not contact
the external air. Generally, the electrode layers are high in
reactivity, and are therefore likely to deteriorate when in contact
with the external air. According to this embodiment, however, the
electrode layers do not undergo deterioration since the electrode
layers do not contact the electrode layer. In addition, it can be
conceivable to use a seal material or the like in order to secure
air-tightness. However, since the electrode layers are high in
reactivity as described above, the contact of the electrode layers
with a kind of resin or the like that is different from the
electrode materials give rise to a risk of an unexpected reaction.
In this embodiment, however, since air-tightness is secured by
using the materials of the electrode layers instead of a sealing
material that is different in kind from the electrode layer
materials, there is no occurrence of an unexpected reaction.
[0040] Besides, it is also conceivable to use an adhesive as a
method for fixing the insulating frame and the current collecting
plates. However, as described above, if a resin or the like
different from the electrode materials contacts the electrode
layers, there is a risk of causing an unexpected reaction. In this
embodiment, since the current collecting plates are fixed to the
insulating frame without using an adhesive that is different in
kind from the electrode materials, the fixation between the
insulating frame and the current collecting plates can be achieved
while occurrence of an unexpected reaction is restrained.
[0041] Besides, as shown in FIG. 1, a portion of each current
collecting plate is inserted in the insulating frame, and a portion
thereof is protruded out of the insulating frame. Therefore, it is
possible to easily attach a mechanism that extracts output from the
cell, and therefore productivity improves. Besides, since the
spaces between the insulating frame and the current collecting
plates on both sides are filled with the electrode materials, this
construction restrains the coming-apart of either current
collecting plate.
[0042] Besides, the process of performing the pressing, and the
process of forcing the materials of the electrode layers to get in
between the insulating frame and the current collecting plates can
be simultaneously performed, and therefore the production is easy.
Besides, since the insulating frame can be held in a pressed state,
the insulating frame and the current collecting plate can be fixed
with an appropriate pressure applied thereto. Therefore, a solid
lithium secondary cell with a reduced contact resistance can be
produced.
[0043] Although in Embodiment 1, the sizes of the insulating frame
and the current collecting plate are determined so that the
difference between the inside diameter of the insulating frame and
the outside diameter of the current collecting plates is 300
micrometers, this is not restrictive. It is appropriate to set the
sizes of the insulating frame and the current collecting plates so
that the materials of the electrode layers can get in between the
insulating frame and the current collecting plates, and so that the
current collecting plates can be held by the elastic force of the
materials of the electrode layers. Concretely, the size of the gaps
between the current collecting plates and the insulating frame may
be in the range of 50 micrometers to 600 micrometers and,
particularly, in the range of 100 micrometers to 600 micrometers.
That is, the outside diameter of the current collecting plates may
be smaller than the inside diameter of the insulating frame by a
length of 100 micrometers to 1200 micrometers and, particularly, by
a length of 200 micrometers to 1200 micrometers.
[0044] Incidentally, the easiness of the entrance of the materials
of the electrode layers into the spaces between the insulating
frame and the current collecting plates is considered to be
dependent on the particle diameter of the materials. Therefore, the
difference between the inside diameter of the insulating frame and
the outside diameter of the current collecting plates may be
determined on the basis of the particle diameter of the materials
of the electrode layers. Concretely, the size of the gaps between
the insulating frame and the side surfaces of the current
collecting plates may be about 2 to 30 times the average particle
diameter of the electrode layer materials (the difference in
diameter between the insulating frame and the side surfaces of the
current collecting plates may be about 4 to 60 times the average
particle diameter). Depending on the production method for the
electrode layer materials, particles whose diameters are larger
than the average particle diameter can also exist in the materials.
In such a case, the size of the gaps may be set on the basis of the
maximum particle diameter of the material substances of the
electrode layers. Concretely, the size of the gaps between the
insulating frame and the side surfaces of the current collecting
plates may be about 1 to 10 times the maximum particle diameter
(the difference in diameter therebetween may be about 2 to 20 times
the maximum particle diameter).
[0045] Although in Embodiment 1, the current collecting plates are
held by the elastic force of the material substances of the
electrode layers, this is not restrictive. It suffices that the
current collecting plates are held or fixed by the insulating
frame. For example, the current collecting plates may be held
directly by the insulating frame. Concretely, the outside diameter
of the current collecting plates may be substantially equal to the
inside diameter of the insulating frame. Therefore, the current
collecting plates can be held directly by the insulating frame, and
air-tightness of the electrode layers can be secured. That is, from
the view point of restraining the coming-apart of the current
collecting plates or the like, it is appropriate that the current
collecting plates be held directly or indirectly by the insulating
frame.
[0046] Although in Embodiment 1, a tubular insulating frame having
a circular cross-section is used, this is not restrictive. That is,
it suffices that the insulating frame is constructed of an
electrically insulating member, and has a shape that allows an
electrolyte-electrode layered assembly to be formed in its
interior, and that makes it possible to directly or indirectly hold
the current collecting plate. For example, the insulating frame may
have a shape of a hollow tube having a rectangular cross-section
(square tube), or a tubular shape having a polygonal or elliptical
cross-section. That is, in this application, the term "tubular" is
not limited to a circular tubular shape.
[0047] Although in Embodiment 1, a portion of each current
collecting plate is within the insulating frame and another portion
thereof is outside the insulating frame, this is not restrictive.
For example, a structure as shown in FIG. 8 in which the current
collecting plates are provided within an insulating frame 72 is
also permissible. In this structure, the coming-apart of the
current collecting plates or the like can be restrained even in the
case where a lateral force is applied to the cell. Besides,
although in Embodiment 1, both the current collecting plates of the
negative electrode and the positive electrode are held by the
insulating frame, this is not restrictive. It is appropriate that
the foregoing construction in which an insulating fame holds a
current collecting plate be applied to at least one of the two
current collecting plates. Therefore, for example, in a solid cell
having a construction in which the electrode layer of the negative
electrode serves also as a current collecting plate of the negative
electrode, it is appropriate to apply the invention to the side of
the positive electrode.
[0048] Embodiment 1 uses LiCoO.sub.2 as a positive electrode active
material, 70Li.sub.2S-30P.sub.2S.sub.5 as an electrolyte material,
graphite as a negative electrode active material, and stainless
steel as a current collecting plate. However, this is not
restrictive. It is appropriate that the current collecting plate be
made of an electrically conductive substance that provides such a
strength that the current collecting plate can be held directly or
indirectly by the insulating frame. For example, aluminum, nickel,
copper, etc. may be used.
[0049] It suffices that the electrode active material and the
electrolyte material allow a solid lithium secondary cell to be
constructed. The positive electrode active material used herein may
be, for example, TiS.sub.2, LiNiO.sub.2, etc. Besides, the negative
electrode active material used herein may be, for example, Li
metal, Li--Al alloy, Li--In alloy, etc. Besides, the electrolyte
material used herein may also be solid electrolytes other than
70Li.sub.2S-30P.sub.2S.sub.5, such as
Li.sub.3PO.sub.4--Li.sub.2S--SiS.sub.2-based glass, a
chalcogenite-based lithium ion conductor containing Li.sub.2O,
Li.sub.2SO.sub.4 and Li.sub.2CO.sub.3, a material containing
lithium halide, and other oxide-based lithium ion conductors,
etc.
[0050] Besides, the particle diameter of the electrode active
material and the electrolyte material is not limited to the
particle diameters mentioned above in conjunction with Embodiment
1, but it is appropriate that a particle diameter selected be
suitably selected, from the view point of productivity.
[0051] Although in the production method of Embodiment 1, the
definitive pressing is performed so that each current collecting
plate moves 100 micrometers, this is not restrictive. It is
appropriate to determine an amount of movement of the current
collecting plates such that the materials of the electrode layer
are forced into the gaps to such a degree that the current
collecting plates can be held by the elastic force of the materials
of the electrode layers. Incidentally, from the view point of
holding the current collecting plates by the elastic force of the
materials of the electrode layers, it is also appropriate that the
moving distance of each current collecting plate relative to the
insulating frame be equal to or greater than one-fifth of the
thickness of the current collecting plates, and be less than or
equal to the thickness of the current collecting plates.
Specifically, it is appropriate to determine the tentative pressing
pressure and the definitive pressing pressure so that the moving
distance of the each current collecting plate relative to the
insulating frame is equal to or greater than one-fifth of the
thickness of each current collecting plate, and is less than or
equal to the thickness of each current collecting plate.
[0052] Besides, although in the production method of Embodiment 1,
the tentative pressing is performed, this is not restrictive.
Specifically, a feature of this production method is that materials
constituting the electrode layers are forced to get in between the
insulating frame and outer peripheries of the current collecting
plates, and it suffices that the production method is able to
achieve the foregoing operation and effect. That is, the tentative
pressing may be omitted. Incidentally, since the tentative pressing
fixes the materials of the electrode layers to some extent, the
tentative pressing may also be performed from the viewpoint of
productivity.
[0053] While the invention has been described with reference to
example embodiments thereof, it is to be understood that the
invention is not limited to the described embodiments or
constructions. To the contrary, the invention is intended to cover
various modifications and equivalent arrangements. In addition,
while the various elements of the example embodiments are shown in
various combinations and configurations, other combinations and
configurations, including more, less or only a single element, are
also within the scope of the invention.
* * * * *