JP6960271B2 - All solid state battery - Google Patents

Description

The present invention relates to an all-solid-state battery provided with an exterior body.

Compared to other secondary batteries, lithium-ion secondary batteries have a higher energy density and can operate at high voltage, so they can be made smaller and lighter, and are widely used as power sources for automobiles and mobile phones. It is expected to be used.

However, a general lithium ion secondary battery has a positive electrode and a negative electrode, and a liquid electrolyte (electrolyte solution) such as ethylene carbonate between them, and such an electrolytic solution generally leaks, ignites, or causes a liquid leakage or ignition. There is a risk of explosion. Therefore, an all-solid-state battery using a solid electrolyte is seen as a promising secondary battery in the future.

In an all-solid-state battery, all charge / discharge reactions occur at the interface between solids. Therefore, in an all-solid-state battery, unlike a battery using an electrolytic solution, the interface resistance at the interface between a solid and a solid (for example, the interface between an active material and a solid electrolyte) greatly affects the performance of the battery.

The battery cell of the above-mentioned lithium ion secondary battery is generally housed in the exterior body in a state where contact with the atmosphere is cut off. Since the electrodes expand and contract during charging and discharging of the lithium ion secondary battery, voids are generated inside the exterior body during charging and discharging in the exterior body fixed at regular intervals. If a gap is generated inside the exterior body, the cell may be damaged due to an impact such as vibration from the outside. In particular, in an all-solid-state battery, there is a problem that the interface resistance at the interface between solids increases due to the generation of voids.

For example, Patent Document 1 discloses a pressurizing device and a pressurizing method for a film exterior battery in which a lithium ion battery (film exterior battery) housed in a laminated film is sandwiched between movable plates and pressed by a tightening rod. Has been done.

Further, for example, Patent Document 2 describes that by pressing the exterior body in the thickness direction with a restraining plate, the exterior body is pressed in the stacking direction to maintain a low interfacial resistance at the interface between solids. Has been done.

Japanese Unexamined Patent Publication No. 2015-037047 Japanese Unexamined Patent Publication No. 2013-062174

However, since the tightening rod of Patent Document 1 is configured to press only the central region of the film exterior battery, there is a problem that pressure is not easily applied to the peripheral region of the film exterior battery.

On the other hand, in Patent Document 2, since the side surface portions of the exterior body in the stacking direction are pressed by the two restraint plates, the entire main surface of the battery cannot be uniformly pressed.

A first aspect of the present invention relates to an all-solid-state battery, wherein the all-solid-state battery comprises a first and second electrodes, at least one battery cell having a solid electrolyte disposed between them, and the battery cell. It comprises a first and second plate-shaped member to be sandwiched and an exterior body including a side wall connected to each of the plate-shaped members, and the side wall is the first plate-shaped member or the second plate. It is configured to expand and contract along the direction toward the shaped member.

According to the aspect of the present invention, the all-solid-state battery can be uniformly pressed in the stacking direction.

It is a perspective view which shows the all-solid-state battery which concerns on embodiment of this invention. (A) is a perspective view of the all-solid-state battery after the top plate is connected to the side wall of the exterior body, and (b) is a perspective view of the all-solid-state battery after the sealing space of the all-solid-state battery is decompressed. It is a figure. (A) to (c) are cross-sectional views corresponding to FIGS. 1 (a) to 1 (c), and (d) and (e) are cross-sectional views corresponding to FIGS. 2 (a) and 2 (b). be. (A) to (g) are enlarged cross-sectional views showing a specific shape of the telescopic portion.

An embodiment of the all-solid-state battery according to the present invention will be described below with reference to the accompanying drawings. In the description of each embodiment, directional terms (for example, "top plate" and "bottom plate") are appropriately used for ease of understanding, but these terms are for explanation purposes only. The present invention is not limited. In each drawing, in order to clarify the shape or characteristics of each component of the all-solid-state battery, these dimensions are shown as relative ones and are not necessarily represented by the same scale ratio.

The all-solid-state battery 30 according to the embodiment of the present invention includes an all-solid-state battery exterior body 1, and FIG. 1 is housed inside the components of the all-solid-state battery exterior body 1 and the all-solid-state battery exterior body 1. It is a perspective view which shows the cell laminated body 6. The all-solid-state battery 30 according to the embodiment of the present invention generally accommodates the cell laminate 6 in the all-solid-state battery exterior body 1 and provides a sealing space 4 formed inside the all-solid-state battery exterior body 1. It is configured by sealing and reducing the pressure. By decompressing the inside of the exterior body 1 for an all-solid-state battery in this way, the cell laminate 6 can be pressurized by atmospheric pressure.

(Cell laminate)
The cell laminate 6 is formed by laminating one or more battery cells 7. Although not shown in detail, each battery cell 7 is formed as a laminate composed of a positive electrode current collector, a positive electrode, a solid electrolyte layer, a negative electrode, and a negative electrode current collector. Further, the cell laminate 6 may include a single battery cell 7.

An ionic conductive inorganic solid electrolyte can be used for the solid electrolyte layer. As the inorganic solid electrolyte, sulfide (sulfide-based solid electrolyte) and hydride (hydride-based solid electrolyte) are preferable from the viewpoint of easy plastic deformation. The hydride also includes a solid electrolyte, commonly referred to as a complex hydride. The crystalline state of the solid electrolyte is not particularly limited and may be crystalline or amorphous. Note that easy plastic deformation means that when pressure is applied to the solid electrolyte particles, the pressure (plastic deformation pressure) at the start of the plastic deformation of the solid electrolyte particles is relatively small (for example, 500 MPa or less). means.

When the solid electrolyte layer is formed using the inorganic solid electrolyte, when the cell laminate 6 is pressed, the solid electrolyte particles are plastically deformed and densely packed in the solid electrolyte layer, and the gaps between the particles are reduced. .. Therefore, the adhesion of the interface between the solid and the solid (for example, the interface between the active material layer and the solid electrolyte) can be enhanced under atmospheric pressure without applying pressure to the cell laminate 6 by the restraint jig.
Therefore, the resistance at these interfaces can be reduced. In an all-solid-state battery without a restraint jig, the pressure applied in the thickness direction of the battery cell 7 is about 100 kPa. In the all-solid-state battery according to the present embodiment, even when the pressure is very small, the battery reaction can be performed without using a restraint jig. Further, since it is not necessary to use a restraint jig, the volume occupied by the electrodes and the like can be increased, and the energy density of the battery can be increased.

Examples of the sulfide, and Li 2 _S, Group 13 elements of the periodic table, Group 14 elements, and at least one or more kinds of sulfides containing one element selected from the group consisting of Group 15 Those containing and are preferable. Specific examples of sulfides include Li ₂ S-SiS ₂ , Li ₂ S-P ₂ S ₅ , Li ₂ S-GeS ₂ , Li ₂ S-B ₂ S ₃ , Li ₂ S-Ga ₂ S ₃ , Li. ₂ S-Al ₂ S ₃ , Li ₂ S-GeS _2- P ₂ S ₅ , Li ₂ S-Al ₂ S _3- P ₂ S ₅ , Li ₂ S-P ₂ S ₃ , Li ₂ S-P ₂ S _{3 -P 2 S 5, LiX-} Li 2 S-P 2 S 5, LiX-Li 2 S-SiS 2, LiX-Li 2 S-B 2 S 3 (X: I, Br, Cl, or I), etc. Can be mentioned.

Examples of the hydride include a complex hydride of lithium borohydride. Examples of the complex hydride include LiBH _4- LiI-based complex hydride, LiBH _4- LiNH _2- based complex hydride, LiBH _4- P ₂ S ₅ , LiBH _4- P ₂ I _{4 and the} like. As the solid electrolyte, one type may be used alone, or two or more types may be used in combination, if necessary.

As the positive electrode active material, those used as the positive electrode active material in the lithium ion secondary battery can be used without particular limitation. Examples of positive electrode active materials used in lithium ion secondary batteries include lithium-containing oxides containing, for example, cobalt, nickel, and / or manganese [eg, lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (for example). LiNiO ₂ ), lithium manganate (spinnel-type lithium manganate (LiMn ₂ O ₄ etc.), lithium nickel cobalt oxide (LiNi _1/3 Co _1/3 Mn _1/3 O ₂ etc.), Li excess composite oxide (Oxides such as (Li ₂ MnO _{3- LiMO 2} )], compounds other than oxides can also be mentioned. Examples of compounds other than oxides include olivine compounds (LiMPO ₄ ) and sulfur-containing compounds (Li _2). (S, etc.), etc.) In the above formula, M represents a transition metal.

The negative electrode active material is not particularly limited as long as ions serving as charge carriers can be inserted and removed, and a known negative electrode active material used in a lithium ion secondary battery can be used. Taking lithium-ion secondary batteries as an example, in addition to carbonic materials such as graphite (natural graphite, artificial graphite, etc.), hard carbon, and amorphous carbon, lithium metals that can alloy and dealloy lithium ions. , Alloy, Si alone, etc.

The current collector can be used without particular limitation as long as the metal ions do not elute and diffuse into the electrode material or the solid electrolyte at a high temperature. Examples of the form of such a current collector include a metal foil, a plate-like body, an aggregate of powders, and the like, and a film formed of a material of the current collector may be used. The metal foil may be an electrolytic foil, an etched foil, or the like. It is desirable that the current collector has a strength that does not wavy or tear when forming the electrode.

Examples of the material of the current collector used for the positive electrode include materials stable at the redox potential of the positive electrode, for example, aluminum, magnesium, stainless steel, titanium, iron, cobalt, zinc, tin, or alloys thereof. .. Examples of the material of the current collector used for the negative electrode include materials stable at the redox potential of the negative electrode, such as copper, nickel, stainless steel, titanium, and alloys thereof.

More specifically, each battery cell 7 includes a positive electrode tab 8a and a negative electrode tab 8b that are electrically connected to the positive electrode current collector and the negative electrode current collector (FIG. 1 (b)). The positive electrode tabs 8a and the negative electrode tabs 8b of the battery cells 7 may be electrically connected to each other to connect the battery cells 7 in parallel, or the positive electrode tabs 8a and the negative electrode tabs 8b of the adjacent battery cells 7 may be connected to each other. May be electrically connected and each battery cell 7 may be connected in series (not shown).

(Exterior body for all-solid-state battery)
The exterior body 1 for an all-solid-state battery includes a top plate 2 (see FIG. 1A, also referred to as a “first plate-shaped member” in the present application) formed of a rigid plate-shaped member, and a cell laminate 6. It has an exterior main body 10 (see FIG. 1 (c)) for accommodating the above. The top plate 2 may include a plate-shaped member made of a metal such as stainless steel or an aluminum alloy, or a plastic such as a fluororesin.

The exterior main body 10 has a bottom plate 12 (also referred to as a “second plate-shaped member” in the present application) formed of a plate-shaped member having the same rigidity, and a side wall 14 connected to the bottom plate 12. The bottom plate 12 may include a plate-shaped member made of the same metal or plastic as the top plate 2. Further, as will be described in detail later, the side wall 14 of the cell laminate 6 according to the embodiment of the present invention is in the stacking direction of the cell laminate 6 (that is, the direction from the top plate 2 to the bottom plate 12 of the exterior body 1 for an all-solid-state battery). A telescopic portion 20 (also referred to as a bent portion, an elastic portion, a bellows, or a bellows portion) that can be expanded and contracted in the opposite direction) is included.

The top plate 2 and the bottom plate 12 have, for example, a rectangular planar shape, but are not limited thereto, and may have any planar shape such as a circle, a triangle, or a polygon. The side wall 14 connects the opposite sides of the top plate 2 and the bottom plate 12, and like the top plate 2 and the bottom plate 12, is made of a rigid plate-like member (for example, a thin metal plate such as stainless steel or an aluminum alloy). It may be formed. In general, a thin metal plate is stronger in external force and has excellent moisture blocking property as compared with a laminated film, so that a hard package type exterior body has impact resistance and durability as compared with a laminated package type exterior body. , And is advantageous in moisture barrier properties.

As will be described later, FIG. 2A is a perspective view of the all-solid-state battery 30 after the top plate 2 is connected to the side wall 14 of the exterior body 10, and FIG. 2B is an all-solid-state battery thereafter. It is a perspective view of the all-solid-state battery 30 after the sealing space 4 of the battery exterior body 1 is decompressed (evacuated). That is, as shown in FIG. 2A, after the cell laminate 6 is housed in the sealing space 4 of the exterior body 10, the top plate 2 is connected to the upper end of the side wall 14. The connection between the top plate 2 and the upper end portion of the side wall 14 can be performed by any method as long as it can be hermetically sealed, but may be performed by, for example, laser welding or an adhesive. .. Further, these may be connected by fastening the top plate 2 to the side wall 14 using bolts and O-rings.

Further, in the all-solid-state battery 30 shown in FIGS. 2A and 2B, a positive electrode terminal 16a and a negative electrode terminal 16b protruding from the side wall 14 of the exterior main body 10 are attached. The positive electrode terminal 16a and the negative electrode terminal 16b are electrically connected to the positive electrode tab 8a and the negative electrode tab 8b. Although the positive electrode terminals 16a and the negative electrode terminals 16b shown in FIGS. 2 (a) and 2 (b) are shown as projecting from the side wall 14 of the exterior main body 10, they may be configured to project from the top plate 2. Good (not shown).

3 (a) to 3 (c) are cross-sectional views corresponding to FIGS. 1 (a) to 1 (c), respectively, and FIGS. 3 (d) and 3 (e) are FIGS. 2 (a) and 2 (b), respectively. It is a cross-sectional view corresponding to. The exterior body 1 for an all-solid-state battery shown in FIGS. 2 (a) and 3 (d) is reduced in pressure (vacuum) until the pressure in the sealing space 4 defined therein becomes less than, for example, 100 kPa. The telescopic portion 20 of the side wall 14 expands and contracts in the stacking direction of the cell laminate 6, and the cell laminate 6 is sandwiched between the top plate 2 and the bottom plate 12 and pressed in the stacking direction. As a result, according to the all-solid-state battery exterior body 1 according to the embodiment of the present invention, cells are laminated using atmospheric pressure through the top plate 2 and the bottom plate 12 without separately providing an independent pressurizing device or the like. By uniformly pressing the body 6 in the stacking direction, the interface resistance at the interface between the solids (for example, the interface between the active material layer and the solid electrolyte) can be kept low. Further, the cell laminate 6 can be securely fixed in the exterior body 1 for an all-solid-state battery to protect the cell laminate 6 from vibration or an external impact.

Further, in the all-solid-state battery housed in the conventional rigid exterior body, the electrodes in the battery cell 7 expand and contract during charging and discharging, so that the cell laminate 6 and the top plate of the all-solid-state battery exterior body 1 are expanded and contracted. There is a possibility that a gap may be formed between the 2 or the bottom plate 12. However, according to the present invention, since the side wall 14 of the exterior body 1 for an all-solid-state battery is provided with a stretchable portion 20 that can be expanded and contracted between the top plate 2 and the bottom plate 12, the cell laminate 6 is always (continued). It is pressed by atmospheric pressure, and the generation of the above-mentioned voids can be suppressed. Therefore, it is possible to suppress an increase in interfacial resistance at the interface between solids.

The all-solid-state battery 30 is manufactured by connecting the top plate 2 to the side wall 14 of the exterior body 10 and airtightly sealing the all-solid-state battery 30 and then evacuating the sealing space 4 of the exterior body 1 for the all-solid-state battery. As described above, the present invention is not limited to this, and the top plate 2 is connected to the side wall 14 of the exterior main body 10 in a vacuum chamber (decompression chamber) (not shown), airtightly sealed, and then taken out from the vacuum chamber. A similar all-solid-state battery 30 can be manufactured by applying atmospheric pressure.

4 (a) to 4 (g) are enlarged cross-sectional views showing a specific shape of the telescopic portion 20, and the telescopic portion 20 shown in FIG. 3 (d) is enlarged and shown in FIG. 4 (a). Similar to the side wall 14, the telescopic portion 20 of FIGS. 4A to 4E may be formed by bending a plate-shaped member made of a metal such as stainless steel or an aluminum alloy. The stretchable portion 20 of FIGS. 4 (f) and 4 (g) may be formed of a stretchable rubber such as butyl rubber as shown by hatching in the figure.

The telescopic portion 20 of FIGS. 4 (a) to 4 (e) is formed by forming a part of the side wall 14 over the entire peripheral edge portion, and the telescopic portion 20 of FIG. 4 (a) is bent in an L shape. The telescopic portion 20 of FIG. 4 (b) is bent in a W shape, the telescopic portion 20 of FIG. 4 (c) is bent in a zigzag shape, and the telescopic portion 20 of FIG. 4 (d) is bent. Is curved in a U shape, and the telescopic portion 20 in FIG. 4 (e) is curved in an S shape.

In the elastic rubber portion 20 of FIG. 4 (f), one end of the elastic rubber or elastic rubber arranged linearly is connected to the side wall 14 of the exterior body 10, and the other end is connected to the bottom plate 12. The stretchable portion 20 of FIG. 4 (g) is connected so that one end and the other end of a pair of linearly arranged elastic rubbers or stretchable rubbers sandwich the side wall 14 and the bottom plate 12 of the exterior body 10. It is a thing. The stretchable portion 20 of FIGS. 4 (f) and 4 (g) may be connected to the side wall 14 and the bottom plate 12 by using an adhesive or a thermosetting resin. Further, the connection between the telescopic portion 20 of FIG. 4 (g) and the side wall 14 and the bottom plate 12 may be reinforced by using screws and nuts (both not shown) inserted into the through holes penetrating them. ..

Although the telescopic portion 20 has been described above as being connected to the side wall 14 and the bottom plate 12, it is not always necessary to connect the telescopic portion 20 to the bottom plate 12, and by bending or bending a part of the side wall 14 (FIGS. 4A to 4A). (E)), it may be configured by arranging it in the central portion of the side wall 14 (FIGS. 4 (f) and (g)).

As described above, in the exterior body 1 for an all-solid-state battery according to the present invention, the sealing space 4 defined inside the outer body 1 accommodates the cell laminate 6 and is depressurized until, for example, becomes less than 100 kPa. The expansion / contraction portion 20 can be expanded and contracted in the stacking direction of the cell laminate 6, and the cell laminate 6 can be pressed between the top plate 2 and the bottom plate 12 in the stack direction. Therefore, according to the all-solid-state battery exterior body 1 according to the present invention, the cell laminate 6 is always uniformly pressed in the stacking direction by using atmospheric pressure through the rigid top plate 2 and bottom plate 12. The interface resistance at the interface between solids (for example, the interface between the active material and the solid electrolyte) can be kept low. Further, by securely fixing the cell laminate 6 in the exterior body 1 for an all-solid-state battery, the cell laminate 6 can be protected from vibration or an external impact.

Although not shown in detail, an elastic sheet formed of rubber or the like may be arranged between the cell laminate 6 and the top plate 2 and the bottom plate 12, and between the cell laminate 6 and the side wall 14. good. In this way, the cell laminate 6 can be pressed more uniformly in the stacking direction of the cell laminate 6 and in the horizontal direction orthogonal to the stacking direction, and the interface resistance at the interface between the solids can be maintained low more stably. .. In addition, the cell laminate 6 can be more reliably protected from vibration or external impact.

Further, according to the present embodiment, the cell laminate 6 can be uniformly pressed in the stacking direction by using atmospheric pressure via the top plate 2 and the bottom plate 12 without separately providing a pressurizing device or the like. The all-solid-state battery 30 using the all-solid-state battery exterior 1 according to the present invention can increase the unit weight and the energy density per unit volume, and can be miniaturized to reduce the manufacturing cost.

(Modification example 1)
In the present embodiment, the exterior body 1 for an all-solid-state battery accommodating the cell laminate 6 uses atmospheric pressure by depressurizing the sealing space 4 formed inside, and the top plate 2 and the bottom plate 12 Although the cell laminate 6 arranged between the cells and the cell laminate 6 has been described as being uniformly pressed, the present invention is not limited to this. That is, in the all-solid-state battery 30 according to the modified example of the present embodiment, the sealing space 4 is similarly depressurized, and then the pressure is higher than the atmospheric pressure (for example, the pressure is less than about 60 MPa) by using a pressurizing device or the like. By pressing the plate 2 and the bottom plate 12 against each other, the cell laminate 6 arranged between them may be uniformly pressed. In this case, the cell laminate 6 can be uniformly pressed with a pressure higher than the atmospheric pressure. Further, the battery exterior body 1 according to the present invention has a stretchable portion 20 whose side wall can expand and contract along the direction from the top plate 2 to the bottom plate 12, and the stretchable portion 20 is pressed with a larger pressure. The larger displacement of the resulting cell laminate 6 can be reliably absorbed. In the all-solid-state battery 30, after depressurizing the sealing space 4 as in the present embodiment, the top plate 2 and the bottom plate 12 are pressed against each other at a pressure equal to or higher than the atmospheric pressure using a pressurizing device or the like. May be good.

(Modification 2)
In the all-solid-state battery 30 according to still another modification 2, after the sealing space 4 is similarly depressurized, the battery is preliminarily charged in a state where the cell laminate 6 is pressed once by using a pressurizing device or the like. After being discharged (initial aging treatment is performed), the pressurizing device or the like may be removed at the time of use to uniformly press the cell laminate 6 arranged between the top plate 2 and the bottom plate 12. .. In this case, the unit weight of the all-solid-state battery 30 and the energy density per unit volume during use are reduced, and the telescopic portion 20 of the all-solid-state battery exterior body 1 is a cell as in the above embodiment and the first modification. The laminated body 6 can be pressed uniformly. Further, the expansion / contraction portion 20 of the exterior body 1 for an all-solid-state battery according to the present invention is subjected to a large displacement caused by pressing the cell laminate 6 with a large pressure while performing the initial aging treatment using a pressurizing device or the like. It can be reliably absorbed.

The present invention can be used for an all-solid-state battery that presses in the stacking direction of all-solid-state battery cells.

1 ... Exterior for all-solid-state battery, 2 ... Top plate, 4 ... Sealing space,
6 ... cell laminate, 7 ... battery cell, 8a ... positive electrode tab, 8b ... negative electrode tab,
10 ... Exterior body, 12 ... Bottom plate, 14 ... Side wall, 16a ... Positive terminal, 16b ... Negative terminal,
20 ... Telescopic part,
30 ... All-solid-state battery

Claims (3)

A first and second electrode and at least one battery cell having a solid electrolyte disposed between them.
A first and second plate-shaped member holding the battery cell and an exterior body including a side wall connected to each of the plate-shaped members are provided.
The sidewalls Ri stretchable der along a direction toward the first plate member or the second plate-like member,
Interior, all-solid-state battery according to claim state der Rukoto that depressurized. The all-solid-state battery according to claim 1, wherein the side wall includes a bent portion or an elastic portion. The all-solid-state battery according to claim 1 or 2 , wherein the solid electrolyte contains at least one selected from the group consisting of a sulfide-based solid electrolyte and a hydride-based solid electrolyte.

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