JP5400304B2 - Assembled battery - Google Patents

Description

  The present invention relates to a solid battery including a current collector formed on positive and negative electrodes, such as an all solid lithium ion secondary battery, and an assembled battery using the solid battery.

  In the field where lithium-ion secondary batteries are expected to be applied in the next generation, there are power storage devices for automobiles and power generators. To expand into these applications, it is essential to increase the size of lithium-ion secondary batteries It becomes.

  For example, when deploying in automobile applications, a conventional non-solid type lithium ion secondary battery uses a flammable organic solvent-based electrolyte, and thus the safety problem cannot be fundamentally solved. Therefore, in recent lithium ion secondary batteries, in order to solve the above-mentioned safety problem, an all-solid lithium ion secondary battery made of only a solid that does not use an organic solvent is known (see Patent Document 1). .

On the other hand, in a non-solid type lithium ion secondary battery, it is effective to use a non-carbon-based active material in order to further increase the capacity. However, in a non-carbon active material, the capacity decreases with repeated charge and discharge. In order to prevent this, there is a lithium ion secondary battery using an active material made of a metal or alloy that absorbs and releases lithium in a negative electrode for a lithium secondary battery and a conductive auxiliary agent such as carbon fiber having high electrical conductivity. It is disclosed (see Patent Document 2).
JP 2007-324079 A JP 2004-296186 A

  The all-solid-state lithium ion secondary battery described in Patent Document 1 has a low thermal conductivity of the material constituting the battery and cannot uniformly dissipate heat generated by the battery reaction. Since the heat due to the reaction cannot be dissipated uniformly, the internal temperature of the large-sized all-solid lithium ion secondary battery becomes nonuniform with the battery surface temperature. Due to the non-uniformity of the internal temperature, the speed of movement of lithium ions inside the battery differs between the high temperature part and the low temperature part. Thus, there is a problem that the performance of the battery is deteriorated by partially promoting the movement of lithium ions.

  Moreover, the carbon fiber used for the negative electrode for lithium secondary batteries of patent document 2 is used as a conductive auxiliary agent of an electrode to the last, and it is neither disclosed nor suggested that it relates to the above heat dissipation.

  The present invention has been made to solve the above-described problems, and the object of the present invention is to uniformly dissipate heat generated by a battery reaction in a solid state battery, and the battery performance does not deteriorate even when the battery is enlarged. The object is to provide a solid state battery.

  The inventors of the present invention have made extensive studies to solve the above problems. As a result, the inventors have found that the above problem can be solved by forming a layer having a predetermined void on the current collector formed on both the positive electrode and the negative electrode, and the present invention has been completed. More specifically, the present invention provides the following.

  (1) A solid battery in which current collectors are formed on both the positive electrode and the negative electrode, and at least one of the current collectors has a layer having a predetermined gap (hereinafter also simply referred to as a layer). .

  (2) The solid state battery according to (1), wherein the porosity of the layer is 50 vol% or more.

  (3) The solid battery according to (1) or (2), wherein the layer includes a fibrous material.

  (4) The solid battery according to (3), wherein the fibrous material is bound by a binder.

  (5) The solid battery according to (3) or (4), wherein the fibrous material is at least one kind selected from carbon fiber, metal fiber, metal oxide fiber, and glass fiber.

  (6) The solid battery according to any one of (1) to (5), wherein the layer has conductivity.

(7) The solid state battery according to any one of (1) to (6), wherein the layer has a thickness of 0.01 mm to 2 mm.
(8) The said collector is a solid battery in any one of (1) to (7) in which the said layer is further formed on the planar conductive layer formed on a positive electrode or a negative electrode.

  (9) The solid battery is an all solid lithium ion secondary battery in which a positive electrode current collector layer, a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer, and a negative electrode current collector layer are laminated in this order. The solid battery according to any one of (1) to (8).

  (10) An assembled battery formed by laminating a plurality of solid batteries according to any one of (1) to (9).

  (11) The assembled battery as described in (10) enclosed with gas.

  According to the present invention, a layer having a predetermined gap is formed in a current collector in a solid battery, so that reaction heat due to a battery reaction that occurs in the positive electrode or the negative electrode can be uniformly dissipated. For this reason, it becomes possible to prevent the temperature from becoming non-uniform inside the battery and to prevent the battery performance from deteriorating.

  Hereinafter, an embodiment of the present invention will be described in detail. However, the present invention is not limited to the following embodiment, and may be implemented with appropriate modifications within the scope of the object of the present invention. it can.

<Solid battery>
The solid battery is usually composed of a current collector / positive electrode / solid electrolyte / negative electrode / current collector. The solid state battery of the present invention is characterized in that a layer having a predetermined gap is formed on the current collector. Hereinafter, the solid battery of the present invention will be described in the order of a solid electrolyte, a positive electrode, a negative electrode, and a current collector.

[Solid electrolyte]
The solid electrolyte used in the present invention is not particularly limited, but is preferably composed of an inorganic solid electrolyte. As the inorganic solid electrolyte that can be used in the present invention, a phosphorus compound containing at least Li, P, and O is desirable. For example, lithium phosphate (Li ₃ PO ₄ ), LiPON obtained by substituting part of oxygen of lithium phosphate with nitrogen, LiPOD (D is Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb) , Mo, Ru, Ag, Ta, W, Pt, Au, etc.). LiAON (A is at least one selected from Si, B, Ge, Al, C, Ga, etc.) and the like can also be preferably used. These may be used alone or in combination of two or more.

[Positive electrode]
The positive electrode is not particularly limited as long as it contains a positive electrode active material. As the positive electrode active material, a material known as an active material of a secondary battery can be used without any particular limitation. Examples of the positive electrode active material include lithium-containing transition metal oxides, vanadium oxides, chromium oxides, titanium sulfides, and the like. Examples of the lithium-containing transition metal oxide include lithium cobalt oxide (LiCoO ₂ , LiCoPO ₄ F), lithium nickel oxide (LiNiO ₂ ), lithium manganese oxide (LiMnP 0 ₄ , LiMn ₂ O ₄ ), lithium Iron-based oxides (LiFePO ₄ , Li ₂ FePO ₄ F), LiMO ₂ (M is at least two selected from Ni, Co, Fe, Al, Mg, Mn, etc.) are preferable. These may be used alone or in combination of two or more.

[Negative electrode]
A negative electrode will not be specifically limited if a negative electrode active material is included. As the negative electrode active material, a material known as an active material of a secondary battery can be used without particular limitation. Examples of the negative electrode active material include metals or metalloids, oxides, nitrides, oxynitrides, SiB ₃ , Mg ₂ Si, carbon, Cu ₂ P, Fe ₂ S, and FeSb ₂ . As the metal or semimetal, lithium, silicon, amorphous silicon, aluminum, silver, tin, antimony, or the like can be used. As the oxide, SiO, SnB _0.5 P _0.5 O ₃ , SnBPO ₆ , the use of _{SnO 2, Fe 2 O 3,} CoO, WO 2, Li 2 SrTi 6 O 14, MoO 2, Li 4 Ti 5 O 12, TiO 2, Nb 2 O 5, WO, Ta 2 O 5 , etc. As the nitride, Li _2.6 Co _0.4 N, Li ₃ FeN ₂ , Li ₇ MnN ₄ or the like can be used. These may be used alone or in combination of two or more.

  The above positive electrode, solid electrolyte, and negative electrode can be laminated by a conventionally known method to form a battery. Although the lamination method is not particularly limited, for example, a method using a green sheet as described in JP 2007-134305 A can be appropriately used. The “green sheet” refers to an unfired body of glass powder, crystal (ceramics or glass ceramic) powder formed into a thin plate, glass powder, crystal (ceramics or glass ceramic) powder, organic binder, A slurry obtained by molding a mixed slurry of a plasticizer, a solvent, etc. into a thin plate shape by a doctor blade, a calendar method or the like. That is, a positive electrode, a solid electrolyte, and a green sheet of a negative electrode were respectively prepared, laminated and pressed to be densified, and then heated to remove organic substances such as a binder and a dispersant, and then fired at a high temperature to be positive electrode / solid electrolyte / A negative electrode laminate sintered body is obtained. As a result, a thin sintered body having a large area can be obtained.

[Current collector]
The current collector in the solid battery of the present invention has a layer having a predetermined gap. This makes it possible to uniformly dissipate the reaction heat of the battery reaction, and in particular, it is possible to effectively prevent the temperature inside the solid battery from becoming higher than the surface. That is, a part of the inside of the battery becomes high temperature, the movement of lithium ions is promoted at the high temperature part, and it is possible to prevent the battery performance from being deteriorated due to the deterioration of the part earlier. As in the present invention, the reaction heat due to the battery reaction is uniformly dissipated because the reaction heat moves through the air gap by convection of heat in the gap, and the heat release of the reaction heat is promoted to the outside. Conceivable.

  In the present invention, “a layer having a predetermined void is formed in the current collector” means that a layer having a predetermined void may be formed on the surface of the current collector, and the current collector itself is a predetermined layer. The case where the layer has a void is also included. In addition, a current collecting function, that is, conductivity is not essential for this layer. That is, the aspect of the current collector in the present invention includes (a) a normal current collecting layer + a layer having a predetermined void (conductivity), (b) a current collecting layer having a predetermined void (conductivity) ) Only, and (c) a normal current collecting layer + a layer having a predetermined gap (no conductivity). In the aspect (c), a layer having a predetermined gap is used as an insulating layer. In the present invention, the whole including the insulating layer is also defined as a current collector in this aspect.

  “A layer with a predetermined gap” means that heat of reaction caused by a battery reaction generated in an electrode is transferred from the electrode side to the layer, heat is convected in the gap, and the heat is dissipated outside the battery. That's fine. The degree of the void can be set as appropriate, but the void ratio is 50 vol% or more, more preferably 60 vol% or more, and still more preferably 70 vol% or more. If the porosity is 50 vol% or more, it is preferable because heat dissipation is sufficient, and if the porosity is 80 vol% or less, an extra space is included, but the entire battery can be contained in a compact volume. Here, the porosity is a numerical value defined by a value converted from the material forming the void layer in the volume of the void layer, for example, the fibrous material and the volume of the binder that joins them to the electrode.

  The configuration of the layer having the predetermined void is not particularly limited, and a lattice shape, a mesh shape, a fiber shape, or the like can be used. Among these, a fibrous shape is preferable, and the layer is formed of a fibrous material and a binder. It is preferable. In this case, if the fibrous material is conductive, the layer also has a current collecting effect, and if it is insulating, the layer portion functions as an insulating layer. And the high adhesive force in joining surfaces, such as a positive electrode or a negative electrode, is obtained by being bound with a binder. Moreover, it becomes possible to leave a preferable space | gap between fibers, connecting a fiber and a fiber with a binder by selecting suitably the kind and mixing | blending of a fibrous material and a binder. The layer formed of the fibrous material and the binder can be obtained by a conventionally known method, for example, by mixing the fibrous material and the binder with a solvent to form a slurry, and applying and drying the slurry.

  As the fibrous material, carbon fiber, metal fiber, metal oxide fiber, and glass fiber are preferable, and it is more preferable to use carbon fiber having conductivity and thermal conductivity.

  Since carbon fiber has high electrical conductivity and thermal conductivity, it is possible to further promote the release of reaction heat due to the battery reaction while having current collecting properties. For this reason, the effect which makes the temperature inside a solid battery uniform becomes high, and deterioration of battery performance can be suppressed more.

  In addition, since the metal fiber has high conductivity and high thermal conductivity like the carbon fiber, the deterioration of the battery performance can be further suppressed as described above. In addition, metal fibers are preferred because of the wide selection of materials. Furthermore, since the current collector is usually made of a metal such as aluminum or copper, the use of metal fibers is suitable when the current collector itself is used as the layer of the present invention having a predetermined gap. .

  In the case of using metal oxide fiber or glass fiber, it is suitable for insulating a layer having a predetermined gap. In some cases, the inside of a battery having a layer structure is desired to be electrically insulated between layers in order to prevent a short circuit. In such a case, if the metal oxide fiber or glass fiber is used, electricity is not passed, but reaction heat due to the battery reaction can be dissipated, which is preferable.

  Examples of carbon fibers that can be used in the present invention include vapor grown carbon fibers (for example, VGCF, registered trademark of Showa Denko KK), carbon nanotubes, and the like. Carbon nanotubes are preferred because they have lower electrical resistance than vapor grown carbon fibers. On the other hand, vapor grown carbon fibers are preferable because they are longer than carbon nanotubes and easily form voids. Vapor-grown carbon fiber is most preferable among carbon fibers having conductivity because it has high crystallinity and thermal conductivity and electrical conductivity. The conductive carbon fiber used in the present invention may contain a particulate or plate-like carbon material such as graphite or carbon black.

  Examples of the metal fiber that can be used in the present invention include titanium, nickel, copper, and the like. Among these, copper is particularly preferably used because of its high thermal conductivity and higher heat dissipation effect.

  Examples of the metal oxide fiber that can be used in the present invention include titanium oxide, zinc oxide, nickel oxide, and silicon oxide. Among these, silicon oxide is particularly preferable because of its insulating properties and abundant resources. preferable. Moreover, when it has electroconductivity, what contains a titanium oxide, a zinc oxide, etc. is preferable. Moreover, as a glass fiber, a conventionally well-known thing can be used.

  The binder is not particularly limited as long as it can form voids, but a resin binder is preferable. Specifically, a fluorine resin binder, an acrylic resin binder, and a urethane resin are preferable, and among these, polyvinylidene fluoride (PVDF) and PTFE are particularly preferable because of heat resistance.

  The usage-amount of a binder can be suitably set according to a required space | gap. Although it depends on the type of fibrous material, the amount of binder used in the present invention is preferably 1 part by mass to 50 parts by mass with respect to 100 parts by mass of the fibrous material having conductivity. More preferably, they are 2 mass parts-40 mass parts, Most preferably, they are 3 mass parts-30 mass parts. If the binder is used excessively, the voids may be blocked. However, if the amount of the binder resin used is within the above range, preferable voids are easily formed in the present invention.

The thickness of the layer having a predetermined gap is preferably changed as appropriate according to the material used for the layer, but is preferably in the range of 0.01 mm to 2 mm, more preferably 0.02 mm to 1.8 m, Most preferably, it is 0.05 mm-1.5 mm. If it is 0.01 mm or more, it is preferable because reaction heat due to the battery reaction is easily dissipated by convection of heat. Moreover, if it is 2 mm or less, since the volume of the whole battery can be made compact, it is preferable.

  In the present invention, the position of the layer having a predetermined void is not particularly limited, and it is preferable to appropriately change the position depending on the material used for the layer of the present invention. For example, it is usually preferable that electrons can conduct smoothly between the current collector and the positive electrode or the negative electrode, and if a highly conductive material is used for the layer of the present invention, the layer of the present invention is directly on the positive electrode or the negative electrode. It may be formed. Alternatively, the layer of the present invention may be formed after forming a planar conductive layer on the positive electrode or the negative electrode. According to this aspect, since the layer is not in direct contact with the electrode, it is possible to form an electrically insulating layer having heat dissipation performance, and to reduce the energy density of the battery compared to using an insulating material such as ceramics with less voids. The effect that it can hold high is acquired. The planar conductive layer means a layer having a substantially predetermined thickness, and includes not only thin films such as vapor deposition and sputtering but also foils and sheets.

  In addition, when the solid batteries of the present invention are connected in series and there is a portion to be insulated between the batteries, a heat dissipation layer using an insulating metal oxide fiber or the like is used as a current collector of one battery and its It is preferable to form a heat dissipation layer between the current collector of the battery and the current collector of another battery in contact with the current collector of the battery. In this case, it is preferable because heat can be radiated in addition to electrical insulation.

<All-solid lithium ion secondary battery>
The all-solid-state lithium ion secondary battery of the present invention is an all-solid-state lithium ion secondary battery in which a positive electrode current collector layer, a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer, and a negative electrode current collector layer are laminated in this order. Next battery. In the all-solid-state lithium ion secondary battery of the present invention, the positive electrode current collector and / or the negative electrode current collector is formed with a layer having a predetermined gap, or the positive electrode current collector and the negative electrode current collector itself are predetermined. It is a layer which has the space | gap.

  As the positive electrode current collector and / or the negative electrode current collector, the current collector in the solid state battery can be used as it is.

  A conventionally known solid electrolyte layer can be used and is not particularly limited. As an example, a green sheet containing a lithium ion conductive inorganic powder is fired. As the lithium ion conductive inorganic powder, it is preferable to use a pulverized lithium ion conductive glass ceramic as described in JP-A-2007-134305.

  A conventionally known positive electrode active material layer can be used and is not particularly limited. As an example, a material obtained by firing a green sheet containing a positive electrode active material can be given. As the active material used for the positive electrode material, a transition metal compound capable of occluding and releasing lithium can be used, and includes, for example, at least one selected from manganese, cobalt, nickel, vanadium, niobium, molybdenum, and titanium. Transition metal oxides and the like can be used. Since most active material materials have poor electron conductivity and ion conductivity, conductive carbon, graphite, carbon fiber, metal powder, metal fiber, electron conductive polymer, etc. should be added as an electron conduction aid. preferable. Moreover, it is preferable to add an ion conductive glass ceramic, an ion conductive polymer, etc. as an ion conductive support agent. The addition amount of these electron / ion conduction assistants is preferably in the range of 3 to 35% by mass, more preferably 4 to 30% by mass, and 5 to 25% by mass with respect to the positive electrode material. Most preferably it is.

  A conventionally well-known thing can be used for a negative electrode active material layer, and it does not specifically limit. As an example, a green sheet containing a negative electrode active material is fired. The active material used for the negative electrode material includes metal lithium, lithium-aluminum alloy, lithium-indium alloy and other alloys capable of occluding and releasing lithium, transition metal oxides such as titanium and vanadium, and carbon-based materials such as graphite. Is preferably used. When the active material has poor electron conductivity, it is preferable to add conductive carbon, graphite, carbon fiber, metal powder, metal fiber, electron conductive polymer or the like as an electron conduction aid. Moreover, it is preferable to add ion-conductive glass ceramics, ion-conductive polymers, etc. as an ion-conducting aid. The total amount of these electron / ion conduction assistants added is preferably in the range of 3 to 35% by mass, more preferably 4 to 30% by mass, and more preferably 5 to 25% by mass with respect to the positive electrode material. % Is most preferred.

  The ion conductive glass ceramic added to the positive electrode and the negative electrode is preferably the same as the glass ceramic contained in the solid electrolyte. If they are the same, the ion transfer mechanism contained in the electrolyte and the electrode material is unified, so that the ion transfer between the electrolyte and the electrode can be performed smoothly, and a battery with higher output and higher capacity can be provided.

  In addition, the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer can be appropriately laminated by a method using a green sheet or the like, as in the case of the solid battery, to obtain a laminated sintered body.

<Battery assembly>
The all-solid-state lithium ion secondary battery can be increased in size by using it as an assembled battery in which a plurality of layers are stacked. In this assembled battery, heat is likely to accumulate in the central portion of the laminate, so the problem of deterioration in battery performance is greater. Therefore, the solid battery of the present invention can be preferably applied to a large battery formed by stacking a plurality of solid batteries. At this time, by enclosing a gas such as an inert gas such as argon or nitrogen in the assembled battery, the heat dissipation efficiency is further improved because the heat is absorbed from the layer and the effect of diffusing in the battery is high. Can do.

Hereinafter, the present invention will be described in more detail with reference to examples.
<Preparation of amorphous oxide glass powder>
H ₃ PO ₄ , Al (PO ₃ ) ₃ , Li ₂ CO ₃ , SiO ₂ , and TiO ₂ are used as raw materials. These are mol% in terms of oxide, P ₂ O ₅ is 35.0%, Al ₂ Weigh and mix evenly so that the composition of O ₃ is 7.5%, Li ₂ O is 15.0%, TiO ₂ is 38.0%, and SiO ₂ is 4.5%. The glass melt was obtained by heating and melting for 3 hours while stirring at a temperature of 1500 ° C. in an electric furnace. Then, the glass melt was rapidly cooled by dropping it into running water at room temperature while heating from a platinum pipe attached to the pot, to obtain an oxide glass. When this glass was crystallized in an electric furnace at 1000 ° C. and the lithium ion conductivity was measured, it was 1.3 × 10 ⁻³ Scm ⁻¹ at room temperature. The precipitated crystal phase is mainly Li _{1 + x + y} Al _x Ti _{2 -x} Si _y P ₃ -yO ₁₂ (0 ≦ x ≦ 0.4, 0 <y ≦ 0.6) by powder X-ray diffraction. It was confirmed to be a crystalline phase. After pulverizing the oxide glass with a jet mill, it is placed in a ball mill using ethanol as a solvent, and wet pulverization is performed. The two types of oxide glass powders were obtained.

<Production of electrolyte green sheet>
An oxide slurry having an average particle size of 0.5 μm was prepared by dispersing and mixing an acrylic binder, a dispersant, and an antifoaming agent with water as a solvent. The slurry was decompressed to remove bubbles, and then shaped using a doctor blade and dried to prepare an electrolyte green sheet having a thickness of 30 μm.

<Preparation of positive electrode green sheet>
Commercially available lithium manganate was used as the positive electrode active material. Lithium manganate powder pulverized to an average particle size of 0.9 μm and oxide glass having an average particle size of 0.5 μm are weighed in a ratio of 75:25 wt%, and water is solvent together with the same acrylic binder and dispersant as above. Then, a positive electrode slurry was prepared by dispersing and mixing. The slurry was decompressed to remove bubbles, and then shaped using a doctor blade and dried to produce a positive electrode green sheet having a thickness of 20 μm.

<Preparation of negative electrode green sheet>
As the negative electrode active material, commercially available lithium titanate was used after annealing at 500 ° C. A lithium titanate powder having an average particle size of 5 μm and an oxide glass having an average particle size of 0.5 μm are weighed at a ratio of 80:20 wt%, and dispersed with water as a solvent together with the same acrylic binder and dispersant as described above. The negative electrode slurry was prepared by mixing. The slurry was decompressed to remove bubbles, and then shaped and dried using a continuous roll coater to prepare a negative electrode green sheet having a thickness of 25 μm.

<Production of electrode / electrolyte laminate>
The positive electrode green sheet produced above was cut into 100 mm square, and the negative electrode green sheet was cut into 130 mm square. After stacking two electrolyte green sheets and bonding them with a heated roll press, the green sheet laminate bonded in the order of positive electrode green sheet / electrolyte green sheet / was cut into 130 mm squares according to the size of the negative electrode. Each of the cut green sheets was densified by pressing at room temperature using CIP (cold isostatic pressing). The produced laminate was sandwiched between alumina setters and heated to 400 ° C. in an electric furnace to remove organic substances such as binder and dispersant in the laminate. Thereafter, the temperature was rapidly raised to 900 ° C., held for 5 minutes, and cooled to prepare a laminated sintered body of the positive electrode, the electrolyte, and the negative electrode.

<Preparation of all-solid lithium ion secondary battery>
An aluminum current collector having a thickness of 90 nm was formed by a vapor deposition method on the positive electrode side of the laminate produced above. Further, a 50 nm thick copper current collector was formed on the negative electrode side by sputtering.

  Next, on one side of a 20 μm thick aluminum foil (for positive electrode) and a 18 μm thick copper foil (for negative electrode), NMP (N-methylpyrrolidone) solvent, VGCF (trade name VGCF), PVDF, 90: A slurry mixed at a rate of 10 wt% was applied, and a VGCF layer was formed on each of them (thickness after drying: 55 μm). The porosity of the VGCF layer was 88 vol%.

  Next, the VGCF layer was placed on the electrode side of the laminate to form the current collector of the present invention, and a battery cell was produced. A battery pack in which 10 cells were stacked with a PTFE film and sealed in a laminate cell was produced.

<Cycle test>
The battery prepared above was charged and discharged 50 times at 25 ° C. and 1 / 6C. The discharge capacity after 50 cycles was 40% of the initial discharge capacity.

<Comparative example>
A SUS304 foil having a thickness of 100 μm was sandwiched between the cells so as to be the same as the arrangement of the VGCF layer in the example, and a battery pack was produced in the same manner as in the example. The produced battery was charged and discharged 50 times at 25 ° C. and 1 / 6C. The discharge capacity after 50 cycles was 2% of the initial capacity.

Claims (5)

The positive electrode current collector layer, the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, and the negative electrode current collector layer are laminated in this order,
In the positive electrode current collector layer, the negative electrode current collector layer, or both, a layer having a void with a porosity of 70 vol% or more containing carbon fiber and having a thickness of 0.05 mm to 1.5 mm is formed. An assembled battery in which a plurality of all solid lithium ion secondary batteries are stacked. The assembled battery according to claim 1 , wherein the carbon fibers are bound by a binder. Assembled battery according to claim 1 or 2 layers is electrically conductive with the gap. The assembled battery according to any one of claims 1 to 3 , wherein the current collector is further formed with a layer having the voids on a planar conductive layer formed on a positive electrode or a negative electrode. The assembled battery according to any one of claims 1 to 4 , wherein the battery pack is enclosed with gas.