Battery module

Abstract

To provide a battery module that can suppress the extrusion of molten lithium to the outside even if a lithium metal melts when an all-solid-state battery reaches a predetermined temperature or higher.SOLUTION: A battery module 1 includes a battery assembly 2 formed by stacking a plurality of all-solid-state batteries 20 including an anode layer 207 including a lithium metal layer, a pressurizing mechanism 3 that applies a surface pressure to the battery assembly 2 along the stacking direction of the battery assembly 2, a buffer part 208e capable of storing molten lithium that is molten from the lithium metal layer, and a guiding channel 24 that guides the molten lithium to the buffer part 208e. The pressurizing mechanism 3 forms the guiding channel 24 by a surface pressure distribution when the temperature of the all-solid-state battery 20 is above the melting point of lithium.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a battery module in which a plurality of all-solid-state batteries are stacked. [Background technology]

[0002] In order to maintain low interfacial resistance between the solid electrolyte and the active material layers of the positive and negative electrodes, an electrode assembly having a laminated structure of a positive electrode, a solid electrolyte, and a negative electrode is pressurized in the stacking direction (see, for example, Patent Document 1). For example, a pressing mechanism that presses the exterior member that houses the electrode assembly in the thickness direction is disposed on the outside of the exterior member, and the all-solid-state battery is pressurized in the stacking direction by the pressing force generated by the pressing mechanism. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-062174 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the all-solid-state battery as described above, when the all-solid-state battery reaches a predetermined temperature or higher and the lithium metal melts, the molten lithium is forced out by the pressure applied by the pressing mechanism.

[0005] The problem to be solved by the present invention is to provide a battery module that can prevent molten lithium from being extruded to the outside even when the temperature of the all-solid-state battery reaches or exceeds a predetermined temperature and the lithium metal melts. [Means for solving the problem]

[0006] The present invention solves the above problem by causing a pressure mechanism to form a guide path by distributing surface pressure when the temperature of the all-solid-state battery reaches or exceeds the melting point of lithium, and by using the guide path to guide molten lithium to a buffer section. [Effects of the Invention]

[0007] According to the present invention, when the temperature of the all-solid-state battery reaches or exceeds the melting point of lithium, the pressurizing mechanism forms an induction path by means of a surface pressure distribution, and the induction path induces the molten lithium into the buffer section, thereby making it possible to prevent the molten lithium from being extruded to the outside. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view showing an example of a battery module according to an embodiment of the present invention. [Figure 2] 2(a) is a cross-sectional view taken along line IIa-IIa in FIG. 1, and FIG. 2(b) is a cross-sectional view taken along line IIb-IIb in FIG. 2(a). [Figure 3] FIG. 3 is a cross-sectional view showing a modification of the first adhesive and the second adhesive in the battery module according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] The battery module according to the present embodiment will be described with reference to the drawings. Fig. 1 is a perspective view showing an example of a battery module according to the present embodiment. Fig. 2(a) is a cross-sectional view taken along line IIa-IIa in Fig. 1, and Fig. 2(b) is a cross-sectional view taken along line IIb-IIb in Fig. 2(a).

[0010] The battery module 1 in this embodiment is mounted on a mobile object such as an automobile. The use of the battery module 1 is not particularly limited, and it may be mounted on, for example, an electronic device. As shown in Fig. 1, the battery module 1 includes a battery pack 2 and a pressure mechanism 3 that applies surface pressure to the battery pack 2.

[0011] As shown in FIG. 1 , the pressure mechanism 3 applies surface pressure to both end surfaces of the battery pack 2 in the stacking direction of the battery pack 2 (the X direction in the figure). The pressure mechanism 3 includes a first plate 31, a second plate 32, and multiple (four in this example) fasteners 33. The first and second plates 31, 32 are rigid plates made of metal or the like, and sandwich the battery pack 2 from both end sides in the stacking direction. The fasteners 33 fasten the first and second plates 31, 32 together so that the distance between the first and second plates 31, 32 can be adjusted. The fasteners 33 press the first and second plates 31, 32 toward the battery pack 2, causing the first and second plates 31, 32 to apply surface pressure to the battery pack 2.

[0012] As shown in FIG. 1 and FIG. 2(a), the battery pack 2 includes a plurality of (eight in this example) all-solid-state batteries 20, a plurality of (nine in this example) bus bars 21, a first adhesive 22 interposed between the all-solid-state batteries 20, and a second adhesive 23 interposed between the all-solid-state batteries 20.

[0013] The all-solid-state battery 20 shown in FIG. 2(a) is in a charged state. This charged state refers to a state in which the SOC (State of Charge) is greater than 0%. As will be described in detail later, in the all-solid-state battery 20 of this embodiment, an anode layer 207 made of lithium metal is deposited on the anode current collector 205 during charging. Conversely, when the all-solid-state battery 20 is in a fully discharged state, the anode layer 207 disappears. Note that the fully discharged state refers to a state in which the SOC of the all-solid-state battery 20 is 0%. Furthermore, the all-solid-state battery 20 is not limited to one in which an anode layer is not present when fully charged, and may be one in which an anode layer is present when fully discharged.

[0014] 2(a), the all-solid-state battery 20 includes a positive electrode current collector 201, a positive electrode tab 202, a positive electrode layer 203, a solid electrolyte layer 204, a negative electrode current collector 205, a negative electrode tab 206, a negative electrode layer 207, and an exterior member 208. Note that hereinafter, a laminate obtained by stacking the positive electrode current collector 201, the positive electrode tab 202, the positive electrode layer 203, the solid electrolyte layer 204, the negative electrode current collector 205, the negative electrode tab 206, and the negative electrode layer 207 may be referred to as an electrode body.

[0015] The positive electrode current collector 201 is a plate-like (or foil-like) member having electrical conductivity, and is made of, for example, a metal or a resin having electrical conductivity, but is not particularly limited thereto. Examples of metals that can be used include aluminum, nickel, iron, stainless steel, titanium, and copper. Alternatively, a clad material of nickel and aluminum, or a clad material of copper and aluminum may be used. Examples of resins having electrical conductivity include resins in which a conductive filler is added to a non-conductive polymer material.

[0016] The positive electrode tab 202, like the positive electrode current collector 201, is a conductive plate-like (or foil-like) member and is not particularly limited, and is made of, for example, a metal or a conductive resin. The metal and conductive resin may be the same materials as those used to make the positive electrode current collector 201. One end of the positive electrode tab 202 is connected to the positive electrode current collector 201, and the other end extends outside the exterior member 208. The positive electrode tab 202 is electrically connected to the negative electrode tab 206 of another all-solid-state battery 20 by a bus bar 21.

[0017] The positive electrode layer 203 is formed on a main surface of the positive electrode current collector 201. This positive electrode layer 203 contains at least a positive electrode active material capable of absorbing and releasing lithium (Li) metal, and is not particularly limited, but preferably contains a positive electrode active material containing sulfur. The sulfur-containing positive electrode active material may be any material that can utilize the oxidation-reduction reaction of sulfur to release lithium ions during charging and absorb lithium ions during discharging. The type of sulfur-containing positive electrode active material is not particularly limited, but particles or thin films of elemental sulfur (S), organic sulfur compounds, or inorganic sulfur compounds can be used.

[0018] The organic sulfur compound is not particularly limited, but examples thereof include disulfide compounds, sulfur-modified polyacrylonitrile, sulfur-modified polyisoprene, rubeanic acid (dithiooxamide), and polycarbon sulfide. The inorganic sulfur compound is not particularly limited, but examples thereof include S-carbon composite, TiS2, TiS3, TiS4, NiS, NiS2, CuS, FeS2, Li2S, MoS2, and MoS3. Note that a sulfur-free positive electrode active material may also be used.

[0019] A solid electrolyte layer 204 is interposed between the positive electrode layer 203 and the negative electrode layer 207. When the all-solid-state battery 20 is in a fully discharged state, the solid electrolyte layer 204 is in contact with the negative electrode current collector 205. As the solid electrolyte, for example, a sulfide solid electrolyte or an oxide solid electrolyte can be used, but it is preferable to use a sulfide solid electrolyte.

[0020] Examples of sulfide solid electrolytes include LiI-Li2S-SiS2, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li2S-P2S5, LiI-Li3PS4, LiI-LiBr-Li3PS4, Li3PS4, Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, and Li2S-P2S5-Z m S n (where m and n are positive numbers, and Z is Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li x MO y (where x and y are positive numbers, and M is any of P, Si, Ge, B, Al, Ga, and In). The term "Li2S-P2S5" refers to a sulfide solid electrolyte obtained using a raw material composition containing Li2S and P2S5, and the same applies to the other terms above. Alternatively, sulfide glass or the like may be used as the sulfide solid electrolyte.

[0021] As the oxide solid electrolyte, for example, a compound having a NASICON structure can be used. Examples of the compound having a NASICON structure include compounds represented by the general formula Li 1+x Al x Ge 2-x Compounds (LAGP) represented by (PO4)3 (0≦x≦2), general formula Li 1+x Al x Ti 2-x A compound (LATP) represented by (PO4)3 (0≦x≦2) can be used. Other oxide solid electrolytes include LiLaTiO (for example, Li 0.34 La 0.51 TiO3), LiPON (e.g., Li 2.9 PO 3.3 N 0.46 ), LiLaZrO (e.g., Li7La3Zr2O12 ) etc. can be used.

[0022] The negative electrode current collector 205 is a conductive plate-like (or foil-like) member, similar to the positive electrode current collector 201, and is made of, for example, but not limited to, a metal or a conductive resin. The metal and the conductive resin may be made of the same materials as those used to make the positive electrode current collector 201.

[0023] The negative electrode tab 206, like the negative electrode current collector 205, is a conductive plate-like (or foil-like) member and is not particularly limited, and is made of, for example, a metal or a conductive resin. The metal and conductive resin may be the same materials as those used to make the above-mentioned negative electrode current collector 205. One end of this negative electrode tab 206 is connected to the negative electrode current collector 205, and the other end extends outside the exterior member 208. The negative electrode tab 206 is electrically connected to the positive electrode tab 202 of another all-solid-state battery 20 by a bus bar 21.

[0024] The negative electrode layer 207 is a lithium metal layer mainly composed of lithium metal that is released from the positive electrode layer 203, reaches the main surface of the negative electrode current collector 205 through the solid electrolyte layer 204, and is deposited thereon as the all-solid-state battery 20 is charged. The volume of this lithium metal layer increases as alkali metal is deposited as the all-solid-state battery 20 is charged, but decreases as the alkali metal disappears (moves toward the positive electrode layer 203) as the battery is discharged.

[0025] The electrode assembly is housed inside exterior member 208. This exterior member 208 is, for example, a laminate film in which a fusion layer, a metal layer, and a surface protection layer are laminated in this order. The fusion portion is made of, for example, polyethylene or polypropylene, the metal portion is made of, for example, aluminum foil, and the protection layer is made of, for example, nylon.

[0026] As shown in Fig. 2(b), the exterior member 208 in this embodiment has a substantially rectangular planar shape. As shown in Fig. 2(a), this exterior member 208 is formed by folding a strip-shaped film at a folding portion 208a, and then bonding and sealing three sides of the rectangle with a sealing material 209. This bonding process forms first to third sealed portions 208b to 208d. Note that, although the present embodiment illustrates a case where three sides of the film are bonded using the sealing material 209, this is not limiting. For example, the first to third sealed portions 208b to 208d may be formed by heat-sealing a fusion layer of the exterior member 208.

[0027] The buffer section 208e stores molten lithium that melts from the negative electrode layer 207 when the temperature of the all-solid-state battery 20 reaches or exceeds the melting point of lithium. The melting point of lithium is, for example, approximately 180°C. In this embodiment, the buffer section 208e is an internal space formed between the folded-back section 208a of the exterior member 208 and the electrode body. The exterior member 208 has a metal layer made of aluminum foil or the like, and this metal layer prevents the molten lithium stored in the buffer section 208e from leaking out of the all-solid-state battery 20 at the folded-back section 208a. On the other hand, if the molten lithium reaches the first to third seal sections 208b to 208d, there is a risk that the molten lithium will leak out because the melting point of the seal material 209 is at most approximately 160°C.

[0028] In this embodiment, the buffer portion 208e is provided at the bottom of the battery module 1. Therefore, gravity makes it easier for the molten lithium to flow into the buffer portion 208e, and the molten lithium can be prevented from flowing out of the all-solid-state battery 20.

[0029] In this embodiment, the buffer section 208 is provided on the long side of the rectangle, and the length of the buffer section 208 is longer than the short side of the rectangle. Therefore, the distance that the molten lithium travels to the buffer section 208 can be shortened, and the volume of the buffer section 208 within the all-solid-state battery 20 can be increased.

[0030] As shown in FIGS. 2(a) and 2(b), the above-described plurality of all-solid-state batteries 20 are bonded to one another via a first adhesive 22 and a second adhesive 23. As shown in FIG. 2(b), the first adhesive 22 is provided in a first region R1 on the main surface of the all-solid-state battery 20. On the other hand, the second adhesive 23 is provided in a second region R1 on the main surface of the all-solid-state battery 20. In this embodiment, the first and second regions R1 and R2 have rectangular planar shapes, and the second region R2 is provided below the first region R1. That is, the second region R2 is provided closer to the buffer section 208e than the first region R1.

[0031] The first adhesive 22 and the second adhesive 23 are made of adhesives with different softening points, and the softening point T1 of the first adhesive 22 is higher than the softening point T2 of the second adhesive 23 (T1>T2). The softening point T1 of the first adhesive 22 may be, for example, higher than 100°C (T1>100°C), and the softening point T2 of the second adhesive 23 may be, for example, 100°C or higher and 180°C or lower (180°C≧T2≧100°C). Examples of materials that make up the first adhesive 22 include adhesive resins such as epoxy resins and silicone resins. The second adhesive 23 may also be made of the same resin as the material that makes up the first adhesive 22. The first adhesive 22 and the second adhesive 23 may be made of different materials.

[0032] When the temperature of the all-solid-state battery 20 is within a normal range (for example, less than 100°C), the first and second adhesives 22, 23 are not softened and have approximately the same hardness, so that the pressure mechanism 3 applies a uniform surface pressure to the surface of the all-solid-state battery 20.

[0033] On the other hand, when the temperature of the all-solid-state battery 20 is abnormally high (for example, above 180°C, which is the melting point of lithium), the second adhesive 23, which has a low softening point, is softer than the first adhesive 22, which has a high softening point. Therefore, the surface pressure applied to the surface of the all-solid-state battery 20 is high in the first region R1 where the first adhesive 22 is formed, and low in the second region R2 where the second adhesive 23 is formed. Therefore, the molten lithium melted from the negative electrode layer 207 is likely to flow from the first region R1 side to the second region R2 in a plan view of the all-solid-state battery 20. That is, the molten lithium is guided to the buffer section 208e along the guide path 24 formed by the surface pressure distribution by the pressurizing mechanism 3.

[0034] The shapes of the first adhesive 22 and the second adhesive 23 are not limited to those described above. For example, the first adhesive 22 may be U-shaped, and the second adhesive 23 may be provided inside the first adhesive 22. Such a modified example will be described with reference to the drawings. Fig. 3 is a cross-sectional view showing a modified example of the first adhesive and the second adhesive in the battery module of this embodiment.

[0035] 3, the first adhesive 22B has a downward U-shape. The first adhesive 22B has first to third strip-shaped portions 22a to 22c and an opening 22d. The first strip-shaped portion 22a is located on the positive and negative electrode tabs 202, 206 side of the all-solid-state battery 20, and extends along the width direction of the all-solid-state battery 20 (the Y direction in the figure).

[0036] On the other hand, the second strip portion 22b is located on the buffer portion 208e side of the all-solid-state battery 20 and extends along the height direction of the all-solid-state battery 20 (Z direction in the figure). The second strip portion 22b is connected to one end of the first strip portion 22a. The third strip portion 22c is also located on the buffer portion 208e side of the all-solid-state battery 20 and extends along the height direction of the all-solid-state battery 20 (Z direction in the figure). The third strip portion 22c is provided so as to be spaced apart from the second strip portion 22b and is connected to the other end of the first strip portion 22a. An opening 22d is provided between the second and third strip portions 22b, 22c. That is, the opening 22d is formed toward the buffer portion 208e side.

[0037] A second adhesive 23B is provided inside this opening 22d. As in the above embodiment, the second adhesive 23B is provided on the buffer section 208e side. The upper end and left and right ends of this second adhesive 23B are in contact with the first adhesive 22B, while the lower end is open to the buffer section 208e side.

[0038] In this modified example, by surrounding the second adhesive 23B on three sides with the U-shaped first adhesive 22B, a three-way guide path 24 can be formed, and the molten lithium can be concentrated in the buffer portion 208e.

[0039] With the battery module 1 as described above, when the temperature of the all-solid-state battery 20 reaches or exceeds the melting point of lithium, the molten lithium can be guided to the buffer portion 208e by the guide path 24 formed by the surface pressure distribution of the surface pressure of the pressurizing mechanism 3, thereby preventing the molten lithium from being pushed out of the battery module 1. Furthermore, when the temperature of the all-solid-state battery 20 is normal, no surface pressure distribution occurs and a uniform surface pressure is applied to the all-solid-state battery 20, thereby preventing a decrease in the battery performance of the all-solid-state battery 20.

[0040] Furthermore, as in this embodiment, by providing the buffer portion 208e on only one side of the all-solid-state battery 20 and guiding the molten lithium to the buffer portion 208e by the guide path 24, it is possible to suppress a decrease in energy density.

[0041] Although the embodiments of the present invention have been described above, these embodiments are described to facilitate understanding of the present invention and are not described to limit the present invention. Therefore, each element disclosed in the above embodiments is intended to include all design modifications and equivalents that fall within the technical scope of the present invention.

[0042] For example, in the above embodiment, the internal space of the all-solid-state battery 20 is used as the buffer portion 208e from the viewpoint of improving the volumetric energy density of the battery module 1, but this is not limiting. A buffer portion made of a material with a higher melting point than lithium may be attached to a seal portion or the like of the all-solid-state battery 20, and a guide path that allows molten lithium to move freely may be set in the buffer portion. [Explanation of symbols]

[0043] 1...Battery module 2...Battery pack 20...All-solid-state battery (cell) 201...Positive electrode current collector 202...Positive electrode tab 203...Positive electrode layer 204...Solid electrolyte layer 205...Negative electrode current collector 206...Negative electrode tab 207...negative electrode layer 208...Exterior components 208a...Folded section 208b to 208d: First to third seal parts 208e...Buffer section R1, R2...first and second regions 209...Sealing material 21... Bus bar 22, 22B...First adhesive 22a~22c...Strip 22d…Opening 23, 23B...Second adhesive 24…Taxiway 3...Pressure mechanism 31...First plate 32...Second plate 33...Fastener

Claims

1. a battery pack including a plurality of stacked all-solid-state batteries each including a negative electrode including a lithium metal layer; a pressure mechanism that applies a surface pressure to the battery pack along a stacking direction of the battery pack; a buffer section capable of storing molten lithium melted from the lithium metal layer; a guide path for guiding the molten lithium to the buffer portion, The pressure mechanism forms the guide path by a surface pressure distribution when the temperature of the all-solid-state battery reaches or exceeds the melting point of lithium.

2. The battery module according to claim 1, the all-solid-state battery has a surface to which a surface pressure is applied by the pressurizing mechanism, The surface is a U-shaped first region having an opening; a second region located inside the first region and having a surface pressure applied thereto that is smaller than that applied to the first region; The opening of the first region is located on the buffer portion side of the battery module.

3. The battery module according to claim 1 or 2, The buffer unit is a battery module provided at a lower portion of the battery module.

4. The battery module according to any one of claims 1 to 3, the buffer portion is provided on one side of the all-solid-state battery, The length of one side on which the buffer portion is provided is longer than the length of the other side of the all-solid-state battery.

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