JP2019212571A - Secondary battery - Google Patents

Abstract

To provide a secondary battery improved in charge/discharge characteristics furthermore.SOLUTION: A secondary battery includes a plurality of columnar electrode structures and an electronic conductor layer which is interposed between the columnar electrode structures. Each of the columnar electrode structures includes: a plurality of columnar first electrodes including a first electrode active material, the first electrodes being arranged in a predetermined direction at predetermined intervals; a second electrode including a second electrode active material, the second electrode being arranged to face the first electrode; and an electrolyte having ion conductivity, covering the first electrode and interposed between the first electrode and the second electrode.SELECTED DRAWING: Figure 1

Description

  The invention disclosed in this specification relates to a secondary battery.

  Conventionally, this type of secondary battery includes a positive electrode composed of a current collecting member and an active material-containing layer, a negative electrode composed of a current collecting member and an active material-containing layer, and an electrolyte layer that also serves as a separator. A plurality of unit cells stacked and held in a sealed state in a predetermined case and packaged has been proposed (see, for example, Patent Document 1). In this secondary battery, the electrode active material is subjected to a conductive treatment by coating the surface with a conductive additive and a binder, and the electrode active material is supported on the current collector surface by a dry method. And enables high energy density and high power density. In addition, as such a secondary battery, a lithium ion supply core part including an electrolyte, and a current collector having a three-dimensional network structure formed so as to surround the outer surface of the core part and coated on the outer surface with an internal electrode active material. There has been proposed a cable type secondary battery including an internal electrode including an external electrode including an external electrode active material layer formed so as to surround the external surface of the internal electrode (see, for example, Patent Document 2). In this secondary battery, the electrolyte in the core portion easily penetrates into the active material of the electrode, and the capacity characteristics and cycle characteristics of the battery are excellent.

JP 2004-6285 A Special table 2014-532277 gazette

  Incidentally, in recent years, lithium secondary batteries have been desired to have higher capacities and higher energy densities per unit volume. For example, in order to increase the battery capacity of the secondary battery described in Patent Document 1 described above, it is necessary to further increase the amount of the active material layer. For example, when the active material layer is made thicker, the volume occupied by members not related to charging / discharging, such as separators and current collectors, can be suppressed as compared with those in which more cells are stacked. In some cases, the conduction distance of ions becomes longer and the output decreases. On the other hand, when more cells having a relatively thin active material layer are stacked, although the ion conduction distance is short and high power can be handled, the volume occupied by members not related to charge / discharge increases, so the energy density is increased. It was difficult. In addition, the lithium secondary battery disclosed in Patent Document 2 is said to be able to improve capacity characteristics and cycle characteristics, but it has not been sufficient, for example, to increase energy density and input / output characteristics. Thus, there has been a demand for a new secondary battery that is not of a conventional structure and that further enhances charge / discharge characteristics.

  This indication is made in view of such a subject, and it aims at providing the novel secondary battery which can improve charge / discharge characteristics more.

  As a result of diligent research to achieve the above-described object, the present inventors have found that a columnar electrode structure in which columnar electrodes are arranged can improve the input / output characteristics, and an electron conductor between the columnar electrode structures. It has been found that the provision of a layer can further improve charge / discharge characteristics such as an improvement in charge / discharge capacity, and the invention disclosed in this specification has been completed.

That is, the secondary battery disclosed in this specification is
A plurality of columnar first electrodes including a first electrode active material and arranged at predetermined intervals in a predetermined direction; a second electrode including a second electrode active material and disposed opposite to the first electrode; A plurality of columnar electrode structures having conductivity and covering the first electrode and interposing between the first electrode and the second electrode;
An electron conductor layer interposed between the columnar electrode structure and the columnar electrode structure;
It is equipped with.

  The present disclosure can provide a novel secondary battery that further enhances charge / discharge characteristics. The reason why such an effect is obtained is assumed as follows, for example. For example, by using a three-dimensional array structure of columnar electrodes that can occlude and release ions three-dimensionally from the outer peripheral surface, the positive electrode and the negative electrode can be placed close to each other, thereby improving energy density and input / output performance. be able to. In addition, in a structure including a plurality of columnar electrode structures, since the electron conductor layer is provided between the columnar electrode structures, the current collecting property of the second electrode is improved, and the capacity reduction and the like are further suppressed to reduce charge and discharge capacity. It is speculated that this can be further improved.

FIG. 2 is a schematic diagram illustrating an example of a secondary battery 20. FIG. 2 is a schematic diagram illustrating an example of a secondary battery 20. Explanatory drawing which shows an example of the manufacturing process of the secondary battery. Explanatory drawing which shows an example of the secondary battery 20B. Explanatory drawing of the secondary battery 30. FIG. The relationship figure of the number of lamination | stacking of a column-shaped electrode coupling body and discharge capacity. The schematic diagram of the injection speed measurement cell 40. FIG. FIG. 5 is a graph showing the relationship between the electrolyte penetration time and ionic resistance. FIG. 3 is a schematic view showing that an electrolytic solution penetrates into an electron conductor layer 28.

(Secondary battery)
The secondary battery described in the present embodiment includes a plurality of columnar electrode structures, and an electron conductor layer interposed between the columnar electrode structures and the columnar electrode structures. The columnar electrode structure includes a plurality of columnar first electrodes, a second electrode disposed to face the first electrode, and an electrolyte interposed between the first electrode and the second electrode. In this columnar electrode structure, the electrolyte is formed in layers on the first electrode, the second electrode is formed in layers on the electrolyte, and an electrode body having the first electrode, the electrolyte, and the second electrode is provided. It is good also as what has the structure of the columnar electrode coupling body connected by the connection part. The first electrode may be a negative electrode or a positive electrode, but is preferably a negative electrode. The second electrode may be a positive electrode or a negative electrode, but is preferably a positive electrode. For convenience of explanation, here, a lithium secondary battery including a columnar electrode assembly including a first electrode as a negative electrode, a second electrode as a positive electrode, lithium ions as a carrier, and a connecting portion as a main example will be described below. explain.

  The first electrode may be a negative electrode that is a columnar body including a first electrode active material (negative electrode active material). The first electrode may be columnar, and the cross section thereof may be circular or elliptical, or may be polygonal such as square or hexagonal. In the secondary battery, a plurality of columnar first electrodes are arranged in a predetermined direction with a predetermined interval. The first electrode may include a carbonaceous material as the first electrode active material. Examples of the carbonaceous material include one or more of cokes, glassy carbons, graphites, non-graphitizable carbons, and pyrolytic carbons. Of these, graphites such as artificial graphite and natural graphite are preferable. Moreover, it is good also as carbon fiber which has a graphite structure. As such a carbonaceous material, for example, a material in which crystals are oriented in a columnar axial direction (longitudinal direction) is preferable. Moreover, it is preferable that the crystal is radially oriented from the center to the outer peripheral surface when viewed in a cross-section in a direction orthogonal to the columnar axial direction. Alternatively, the fibrous negative electrode may be a columnar composite oxide capable of occluding and releasing carrier ions. Examples of the composite oxide include lithium titanium composite oxide and lithium vanadium composite oxide. This negative electrode may have a conductive component formed on at least a part of its surface. With this conductive component, the conductivity can be further increased. The conductive component is not particularly limited as long as it is a highly conductive material. For example, a carbonaceous material or a metal may be used. Further, the first electrode may have a current collecting member such as a current collecting wire embedded therein, or may not have this current collecting member.

  The first electrode may have a diameter D (μm) in the range of 20 μm to 800 μm. When the diameter D is 20 μm or more, the formation process of the linked body can be facilitated, and when the diameter D is 800 μm or less, an increase in ion diffusion resistance in the electrode can be further suppressed, which is preferable. The diameter D is preferably 30 μm or more, and more preferably 50 μm or more. Moreover, the diameter D is preferably 500 μm or less, and more preferably 300 μm or less. The distance L (μm) between the first electrodes may be in the range of 5 μm to 1500 μm, and is preferably in the range of 10 μm to 1000 μm.

The second electrode may be a positive electrode that includes the second electrode active material (positive electrode active material) and is disposed to face the first electrode. This 2nd electrode is good also as what is formed in layers on electrolyte. Further, the second electrode may be a composite layer formed on the surface of the electrolyte. The second electrode may have a thickness T (μm) in the range of 5 μm to 200 μm, and is preferably in the range of 10 μm to 100 μm. The thickness T of the second electrode may be appropriately determined according to the positive / negative electrode capacity ratio. For example, the second electrode may be formed by mixing a positive electrode active material, and, if necessary, a conductive material and a binder. Examples of the positive electrode active material include a material capable of occluding and releasing lithium as a carrier. Examples of the positive electrode active material include a compound having lithium and a transition metal, such as an oxide containing lithium and a transition metal element, and a phosphate compound containing lithium and a transition metal element. Specifically, a lithium manganese composite oxide whose basic composition formula is Li _(1-x) MnO ₂ (0 ≦ x ≦ 1, etc., the same shall apply hereinafter), Li _(1-x) Mn ₂ O _4, etc., basic composition Lithium cobalt composite oxide having a formula of Li _(1-x) CoO ₂ or the like, lithium nickel composite oxide having a basic composition formula of Li _(1-x) NiO ₂ or the like, and a basic composition formula of Li _(1-x) Co _a Ni _b Mn _c O ₂ (a> 0, b> 0, c> 0, a + b + c = 1), Li _(1-x) Co _a Ni _b Mn _c O ₄ (0 <a <1, 0 <b <1, 1 ≦ c <2, a + b + c = 2), etc., lithium cobalt nickel manganese composite oxide, basic composition formula of LiV ₂ O ₃ etc., lithium vanadium composite oxide, basic composition formula of V ₂ O ₅ etc. Transition metal oxides such as can be used. A lithium iron phosphate compound having a basic composition formula of LiFePO ₄ can be used as the positive electrode active material. Of these, lithium cobalt nickel manganese composite oxides such as LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ and LiNi _0.4 Co _0.3 Mn _0.3 O ₂ are preferable. The “basic composition formula” means that other elements such as components such as Al and Mg may be included.

  The conductive material included in the second electrode is not particularly limited as long as it is an electron conductive material that does not adversely affect battery performance. For example, graphite such as natural graphite (scale-like graphite, flake-like graphite) or artificial graphite, acetylene black , Carbon black, ketjen black, carbon whisker, needle coke, carbon fiber, metal (copper, nickel, aluminum, silver, gold, etc.) or a mixture of two or more thereof can be used. The binder serves to keep the active material particles and conductive material particles in a predetermined shape and includes, for example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluororubber, and the like. Fluorine resin, thermoplastic resin such as polypropylene and polyethylene, ethylene propylene diene monomer (EPDM) rubber, sulfonated EPDM rubber, natural butyl rubber (NBR), etc. can be used alone or as a mixture of two or more. In addition, an aqueous dispersion of cellulose or styrene butadiene rubber (SBR), which is an aqueous binder, can also be used.

  In the second electrode, the content of the positive electrode active material is preferably higher, preferably 70% by mass or more, and more preferably 80% by mass or more with respect to the entire mass of the second electrode. The content of the conductive material is preferably in the range of 0% by mass to 20% by mass and more preferably in the range of 0% by mass to 10% by mass with respect to the total mass of the second electrode. In such a range, a decrease in battery capacity can be suppressed and sufficient conductivity can be imparted. Further, the content of the binder is preferably in the range of 0.1% by mass to 5% by mass with respect to the entire mass of the second electrode, and in the range of 0.2% by mass to 3% by mass. More preferably.

  The electrolyte has ion conductivity of ions (for example, lithium ions) that are carriers, covers the first electrode, and is interposed between the first electrode and the second electrode. This electrolyte insulates the first electrode from the second electrode. The electrolyte may be formed on the entire outer peripheral surface of the first electrode, and may be formed in layers on the first electrode. The electrolyte preferably has a thickness t (μm) in the range of 2 μm to 15 μm. When the thickness t is 2 μm or more, mechanical strength can be ensured, and a short circuit between the first electrode and the second electrode can be further prevented. Further, when the thickness t is 15 μm or less, the volume occupied by the electrolyte can be reduced, and the energy density can be improved. Moreover, the ion conducting distance can be further shortened, and the input / output performance can be further improved. This thickness t is preferably 3 μm or more, more preferably 5 μm or more from the viewpoint of mechanical strength. Further, the thickness t is preferably 12 μm or less, and more preferably 10 μm or less from the viewpoint of energy density.

The electrolyte is preferably a polymer having ionic conductivity and insulating properties. Examples of the electrolyte include polyvinylidene fluoride (PVdF), a copolymer of polyvinylidene fluoride and hexafluoropropylene (HFP), a polymethyl methacrylate (PMMA), and a copolymer of PMMA and an acrylic polymer. Is mentioned. For example, in the case of a copolymer of PVdF and HFP, a part of the electrolytic solution swells and gels this film, and becomes an ion conductive film. Further, the electrolyte may include an electrolytic solution that conducts ions as carriers. Examples of the electrolytic solution include a non-aqueous solvent. Examples of the solvent of the electrolytic solution include a solvent of a nonaqueous electrolytic solution. Examples of the solvent include carbonates, esters, ethers, nitriles, furans, sulfolanes and dioxolanes, and these can be used alone or in combination. Specifically, as carbonates, cyclic carbonates such as ethylene carbonate (EC), propylene carbonate, vinylene carbonate, butylene carbonate, chloroethylene carbonate, dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate, ethyl Chain carbonates such as n-butyl carbonate, methyl-t-butyl carbonate, di-i-propyl carbonate and t-butyl-i-propyl carbonate, cyclic esters such as γ-butyllactone and γ-valerolactone, Chain esters such as methyl formate, methyl acetate, ethyl acetate, methyl butyrate, ethers such as dimethoxyethane, ethoxymethoxyethane, diethoxyethane, acetonitrile, benzonitrile, etc. Nitriles, tetrahydrofurans such as tetrahydrofuran and methyltetrahydrofuran, sulfolanes such as sulfolane and tetramethylsulfolane, and dioxolanes such as 1,3-dioxolane and methyldioxolane. The electrolytic solution may be obtained by dissolving a supporting salt containing ions that are carriers of the secondary battery. Examples of the supporting salt include LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiSbF ₆ , LiSiF ₆ , LiAlF ₄ , LiSCN, Examples include LiClO ₄ , LiCl, LiF, LiBr, LiI, and LiAlCl ₄ . Among these, 1 selected from the group consisting of inorganic salts such as LiPF ₆ , LiBF ₄ and LiClO ₄ and organic salts such as LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ and LiC (CF ₃ SO ₂ ) _3. From the viewpoint of electrical characteristics, it is preferable to use a seed or a combination of two or more salts. The supporting salt preferably has a concentration in the electrolytic solution of 0.1 mol / L or more and 5 mol / L or less, and more preferably 0.5 mol / L or more and 2 mol / L or less.

Alternatively, the electrolyte may be a solid electrolyte. As the solid electrolyte, for example, an inorganic solid electrolyte, a mixed material of an organic polymer electrolyte and an inorganic solid electrolyte, or an inorganic solid powder bound by an organic binder or the like can be used. Examples of the inorganic solid electrolyte include Li ₃ N, Li ₁₄ Zn (GeO ₄ ) ₄ called LISICON, sulfide Li _3.25 Ge _0.25 P _0.75 S ₄ , perovskite-type La _0.5 Li _0.5 TiO ₃ , (La _{2 / 3} Li _3x □ _{1 / 3-2x} ) TiO ₃ (□: atomic vacancy), Li ₇ La ₃ Zr ₂ O _{12 of} garnet type, LiTi ₂ (PO ₄ ) ₃ called NASICON type, Li _1.3 M _0.3 Ti _1.7 (PO ₃ ) ₄ (M = Sc, Al). In addition, Li ₇ P ₃ S ₁₁ obtained from glass of glass ceramics with a composition of 80Li ₂ S · 20P ₂ S ₅ (mol%), and Li ₁₀ Ge ₂ PS which is a sulfide-based material having high conductivity. ₂ and so on. For glass-based inorganic solid electrolytes, Li ₂ S—SiS ₂ , Li ₂ S—SiS ₂ —LiI, Li ₂ S—SiS ₂ —Li ₃ PO ₄ , Li ₂ S—SiS ₂ —Li ₄ SiO ₄ , Li ₂ S— _{P 2 S 5, Li 3 PO} 4 -Li 4 SiO 4, Li 3 BO 4 -Li 4 SiO 4, and the Li ₂ O and _{SiO 2, GeO 2, B 2} O 3, P 2 O 5 as a glass-based material Examples of the material that can be used as a network modifier. Further, Li ₂ S-GeS ₂ system as Chiorishikon solid electrolyte, Li ₂ S-GeS ₂ -ZnS _{system, Li 2 S-Ga 2 S} 2 _{system, Li 2 S-GeS 2 -Ga} 2 S 3 system, Li ₂ S -GeS ₂ -P ₂ S _{5 based, Li 2 S-GeS 2 -SbS} 5 _{system, Li 2 S-GeS 2 -Al} 2 S 3 system, Li ₂ S-SiS _{2 system, Li 2 S-P 2 S} 5 And solid electrolytes such as Li ₂ S—Al ₂ S ₃ , LiS—SiS ₂ —Al ₂ S ₃ , and Li ₂ S—SiS ₂ —P ₂ S ₅ .

  The connecting portion is a portion configured by at least an electrolyte and connecting the first electrode and the first electrode. A second electrode may be formed on the surface of the connecting portion. That is, the second electrode may be formed across the plurality of first electrodes. This secondary battery may have a structure of a columnar electrode assembly in which an electrode body having a first electrode, an electrolyte, and a second electrode is connected by a connecting portion. The connecting portion may have a thickness in the range of 5 μm to 200 μm, and preferably in the range of 10 μm to 100 μm.

  In the columnar electrode assembly, the first electrodes may be planarly arranged at a predetermined interval. This columnar electrode assembly may constitute a laminate in which two or more columnar electrode assemblies are laminated, but the number of layers is not particularly limited, and may be two layers, three layers, four layers, or the like. . What is necessary is just to select suitably the number of the 1st electrode and the number of lamination | stacking of a columnar electrode coupling body from which a desired battery characteristic is acquired.

  In this secondary battery, the electrode capacity ratio (negative electrode capacity / positive electrode capacity), which is the ratio of the capacity of the first electrode active material (negative electrode active material) to the capacity of the second electrode active material (positive electrode active material), is 1.0. The range is preferably 1.5 or less and more preferably 1.2 or less. The thickness of the second electrode may be appropriately set according to the diameter of the first electrode and the electrode capacity ratio. The thickness of the second electrode may be, for example, the maximum thickness among the portions formed on the first electrode.

  An electron conductor layer is a layer comprised by the electron conductor which conducts an electron, and intervenes between a columnar electrode coupling body and a columnar electrode coupling body. This electron conductor layer may be formed other than between the columnar electrode assembly and the columnar electrode assembly. For example, the electron conductor layer may also be formed on the outermost peripheral surface of the laminate in which two or more columnar electrode assemblies are stacked and / or the outermost peripheral surface of the columnar electrode assemblies. When the electron conductor layer is formed on the outermost peripheral surface, the conductivity can be further increased. The electron conductor layer is more preferably one having higher electron conductivity, such as carbon paper, aluminum, copper, titanium, stainless steel, nickel, iron, platinum, baked carbon, conductive polymer, conductive glass, etc. In addition, for the purpose of improving adhesiveness, conductivity, and oxidation resistance (reduction), those obtained by treating the surface of aluminum or copper with carbon, nickel, titanium, silver, platinum, gold, or the like can be used. The shape of the electron conductor layer is not particularly limited. For example, the shape of the plate, foil, film, sheet, net, punch or expanded, lath, porous, foam, fiber group Examples include formed bodies.

  The electron conductor layer is preferably porous. This is because the electrolyte solution penetrates quickly when the electrolyte solution is injected, and the manufacturing time of the secondary battery can be further shortened. This electron conductor layer preferably has a porosity in the range of 30% by volume to 95% by volume. When the porosity is 30% by volume or more, the permeability of the electrolytic solution can be further increased. Moreover, when the porosity is 95% by volume or less, a decrease in electron conductivity can be further suppressed. The porosity of the electron conductor layer is more preferably 50% by volume or more, and further preferably 70% by volume or more, from the viewpoint of the permeability of the electrolytic solution. The porosity of the electron conductor layer is more preferably 90% by volume or less, and still more preferably 80% by volume or less from the viewpoint of electron conductivity. The thickness of the electron conductor layer is preferably in the range of 0.1 μm to 20 μm. When the thickness of the electron conductor layer is 0.1 μm or more, the electron conductivity can be further increased. In addition, when the thickness is 20 μm or less, a decrease in energy density of the secondary battery can be further suppressed. From the viewpoint of electron conductivity, the thickness of the electron conductor layer is more preferably 0.2 μm or more, and further preferably 0.4 μm or more. Further, the thickness of the electron conductor layer is more preferably 10 μm or less, and further preferably 5 μm or less from the viewpoint of energy density. A current collector may be connected to the electron conductor layer. The current collector is a conductive member, and is electrically connected to the end and / or surface of the electron conductor layer.

  1 and 2 are schematic views showing an example of the secondary battery 20. As shown in FIGS. 1 and 2, the secondary battery 20 includes a plurality of columnar first electrodes 21 arranged at predetermined intervals in a predetermined direction, and a second electrode disposed to face the first electrode 21. 22, an electrolyte 24 that covers the first electrode 21 and is interposed between the first electrode 21 and the second electrode 22, and a connecting portion 26 that connects the first electrode 21 and the first electrode 21. I have. Further, the secondary battery 20 may have a structure of the columnar electrode assembly 10 in which the electrode body 25 having the first electrode 21, the second electrode 22, and the electrolyte 24 is connected by the connecting portion 26. The secondary battery 20 has a structure in which a plurality of columnar electrode assemblies 10 are stacked, and an electron conductor layer 28 is formed between the layers. Further, a current collecting tab 29 as a current collecting unit is connected to the electron conductor layer 28.

(Method for manufacturing secondary battery)
The method for manufacturing a secondary battery according to the present disclosure includes a connecting body forming step of forming a columnar electrode assembly, a stacking step of forming an electron conductor layer on the columnar electrode assembly, and laminating the layers, and a concentration of the electron conductor layer. It is good also as a thing including the current collection part formation process which forms an electrical part. In each step, the above-described secondary battery member, composition, shape, structure, and the like are appropriately used. Note that the current collector forming step may be omitted as appropriate. In the coupling body forming step, the plurality of columnar first electrodes including the first electrode active material are arranged in a predetermined direction with an interval for forming a connecting portion for connecting the first electrode and the first electrode, The second electrode containing the electrode active material and the electrolyte having ion conductivity are disposed so that the electrolyte is interposed on the first electrode and constitutes a connecting portion, and a process of heating and pressing is performed. In this step, a plurality of columnar electrode assemblies having a first electrode, a second electrode, an electrolyte, and a connecting portion are produced. In the laminating step, an electron conductor layer is formed on the upper and lower surfaces of the columnar electrode assembly, and a process of laminating them is performed. The electron conductor layer is preferably a porous member. When the columnar electrode assembly is laminated, a load may be applied and crimped. The stacked body of columnar electrode assemblies obtained in this step may be housed in a housing member and sealed by injecting an electrolytic solution. In the current collector forming step, a process of forming a current collector (current collector tab) on the first electrode or the electron conductor layer is performed.

  FIG. 3 is an explanatory diagram illustrating an example of a manufacturing process of the secondary battery 20 in which the columnar electrode assemblies in which the columnar first electrodes 21 are coupled are stacked. In this manufacturing method, first, the second electrode layer 12 containing the first electrode active material formed on the support 13 and the electrolyte layer 14 are prepared (FIG. 3A). For the support 13, for example, a metal foil such as an Al foil can be used. Next, the second electrode layer 12 and the electrolyte layer 14 formed on the support 13 are bonded and pressed (FIG. 3B). Subsequently, the support 13 is peeled from the second electrode layer 12, whereby the positive electrode mixture is transferred to the electrolyte layer, and the second electrode layer 12 / electrolyte layer 14 assembly is obtained (FIG. 3C). A plurality of the joined bodies are produced. Next, the columnar first electrodes 11 are aligned at a predetermined interval, and the upper and lower sides thereof are sandwiched by a joined body (FIG. 3D), and the electrolyte layer 14 is joined by thermal fusion or the like to obtain the columnar electrode assembly 10 (FIG. 3E). ). The electron conductor layer 28 is formed on the second electrode 22 on the upper surface and the lower surface of the columnar electrode assembly 10, and these are stacked (FIG. 3F). A current collecting tab 29 is connected to the electron conductor layer 28, a current collecting tab 27 is connected to the first electrode 21, put into a housing member, injected with an electrolytic solution and sealed, and the electron conductor layer 28 is interposed therebetween. Thus, the secondary battery 20 in which the columnar electrode assembly 10 is laminated can be obtained (FIG. 3G).

  The secondary battery described in detail above can provide a novel secondary battery with higher charge / discharge characteristics. The reason why such an effect is obtained is assumed as follows, for example. For example, by using a three-dimensional array structure of columnar electrodes that can occlude and release ions three-dimensionally from the outer peripheral surface, the positive electrode and the negative electrode can be placed close to each other, thereby improving energy density and input / output performance. be able to. In addition, in a structure including a plurality of columnar electrode structures, an electron conductor layer is provided between the columnar electrode structures, so that the current collecting property of the second electrode is improved, and a decrease in capacity is further suppressed to charge / discharge capacity, etc. Can be further improved.

  In addition, this indication is not limited to the embodiment mentioned above at all, and as long as it belongs to the technical scope of this indication, it cannot be overemphasized that it can implement with a various aspect.

  For example, in the above-described embodiment, in the secondary battery, the columnar first electrode is described as a negative electrode, and the second electrode covering the first electrode is described as a positive electrode. However, the present invention is not limited to this, and the columnar first electrode is not limited to this. The positive electrode may be used, and the second electrode covering the first electrode may be used as the negative electrode.

  In the embodiment described above, the carrier of the secondary battery is lithium ion. However, the present invention is not particularly limited to this, and alkali metal ions such as sodium ions and potassium ions, and group II element ions such as calcium ions and magnesium ions. Also good. The positive electrode active material may include carrier ions. Moreover, although the electrolytic solution is a non-aqueous electrolytic solution, it may be an aqueous electrolytic solution.

  In the above-described embodiment, the columnar first electrode has been described as an example of a columnar shape, but is not particularly limited thereto, and may be a rectangular column, a hexagonal column, or the like.

  In the embodiment described above, the secondary battery has been described as a stack of a plurality of columnar electrode assemblies in which electrode bodies each having the first electrode, the second electrode, and the electrolyte are connected by a connecting portion, but the present invention is particularly limited to this. However, the present invention is not particularly limited to this as long as it has a plurality of columnar electrode structures having the first electrode, the second electrode, and the electrolyte, and the connecting portion may be omitted. FIG. 4 is an explanatory diagram showing an example of the secondary battery 20B. The secondary battery 20B includes a columnar electrode structure 10B having a first electrode 21, a second electrode 22, and an electrolyte 24, and an electron conductor layer 28B interposed between the columnar electrode structures 10B. In such a secondary battery 20B as well, as in the above-described embodiment, it is possible to provide a novel secondary battery that further enhances charge / discharge characteristics.

  Below, the example which produced the secondary battery mentioned above concretely is demonstrated as an experiment example. First, the result of considering the structure of the secondary battery will be described. Experimental example 1 is a reference example, experimental examples 2, 3, 6, and 7 are examples of the present disclosure, and experimental examples 4 and 5 correspond to comparative examples.

(Experimental Examples 1-3)
A cell in which one or two or more columnar electrode assemblies were laminated was produced in the order of production shown in FIG. First, a polyvinylidene fluoride-co-hexafluoropropylene (PVdF-HFP) solution dissolved in N-methylpyrrolidone (NMP) is applied to a glass substrate, dried, and then peeled to remove PVdF-HFP having a thickness of 5 μm. An isolated membrane (electrolyte layer) was obtained. The positive electrode active material is LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (NCM), the conductive material is carbon black, the binder is PVdF, and they are mixed at a mass ratio of 92: 5: 3. The positive electrode mixture was dispersed in NMP as a solvent. This positive electrode mixture paste was applied to an Al foil having a thickness of 15 μm and dried to prepare a positive electrode mixture layer (FIG. 3A). The positive electrode mixture layer and the electrolyte layer formed on the Al foil are bonded together, and after pressing (FIG. 3B), the Al foil is peeled off to transfer the positive electrode mixture to the electrolyte layer (FIG. 3C). / A joined body of electrolyte layer was obtained. A plurality of the joined bodies were produced. Next, five columnar carbon electrodes having a diameter of 500 μm were aligned at intervals of 1 mm, and the upper and lower sides thereof were sandwiched between joined bodies (FIG. 3D), and PVdF-HFP membranes were joined by thermal fusion to obtain a columnar electrode assembly. (FIG. 3E). A porous Al foil (thickness: 15 μm, porosity: 50% by volume) as an electron conductor was bonded to the positive electrode mixture layers on the upper and lower surfaces of the columnar electrode assembly. This columnar electrode assembly was prepared by stacking only one layer, two layers, and four layers (FIG. 3F), and the cells of Experimental Examples 1 to 3 were obtained. In Experimental Examples 2 and 3, an electron conductor layer is formed between layers of the columnar electrode assembly (see FIGS. 1 and 3). The positive and negative electrode tabs were joined and the electrolyte was injected, then sealed in a sealed container and allowed to stand for 100 hours or longer to obtain a columnar electrode array cell (FIG. 3G). As the electrolytic solution, a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) containing 1M LiPF ₆ at a volume ratio of 3: 4: 3 was used.

(Charge / discharge test, battery output measurement)
A charge / discharge test was performed using the produced cells of Experimental Examples 1 to 3. The charge / discharge test was performed at a final voltage of 2.0 to 4.1 V, a current value of 0.05 C, and a test temperature of 25 ° C. The battery output was calculated from the voltage and current value after 2 seconds when a cell charged to 4.1 V at 25 ° C. was discharged at 3 C.

(Experimental Examples 4 and 5)
A cell produced in the same manner as in Example 2 except that a porous Al foil was disposed only on the outermost periphery and no porous Al foil was used between the layers of the columnar electrode assembly was designated as Experimental Example 4. A cell produced in the same manner as in Example 3 was used as Experimental Example 5 except that a porous Al foil was disposed only on the outermost periphery and no porous Al foil was used between the layers of the columnar electrode assembly. FIG. 5 is an explanatory diagram of a secondary battery 30 that does not include an electron conductor layer between layers of columnar electrode assemblies (Experimental Example 5).

(Results and discussion)
Table 1 shows the number of stacked layers, the electron conductor layer between layers, the discharge capacity, and the battery output of Experimental Examples 1 to 5. FIG. 6 is a diagram showing the relationship between the number of stacked columnar electrode assemblies and the discharge capacity with and without an electron conductor layer between the layers of the columnar electrode assemblies. As shown in Table 1 and FIG. 6, when a porous Al foil as an electron conductor layer was used between the layers, the discharge capacity increased in proportion to the number of stacked columnar electrode assemblies. On the other hand, when the porous Al foil was not used between the layers (Experimental Examples 4 and 5), the discharge capacity did not increase even when the number of layers increased. The cause is presumed as follows. When the porous Al foil is not used between the layers, the active material between the layers is not involved in charging / discharging because the composite material between the layers of the columnar electrode assembly has a large electronic resistance, and only the re-periphery compound is charged / discharged. It was guessed that For this reason, even if the number of layers is increased, only the outermost columnar electrode assembly in contact with the electron conductor (current collector) can participate in charging / discharging, and it is assumed that the capacity does not increase. It was. On the other hand, in Experimental Examples 2 and 3 in which the porous Al foil is disposed between the layers, since the electrons are transferred to the active material between the layers, the discharge capacity increases proportionally as the number of layers increases. Inferred.

  Further, as shown in Experimental Examples 2 and 4 and Experimental Examples 3 and 5 in Table 1, the output was improved by arranging the porous Al foil between the layers in the same number of stacked cells. As described above, this was presumed to be due to the improvement of the electronic conductivity of the composite material portion between the layers of the columnar electrode assembly. Since battery output correlates with input characteristics and quick charge characteristics, it is inferred that these characteristics are improved by placing porous Al foil as an electron conductor layer between the layers of columnar electrode assemblies. It was done.

(Experimental Examples 6 and 7)
Next, the porosity of the electron conductor layer was examined. FIG. 7 is a schematic diagram of a liquid injection rate measuring cell 40 for evaluating the permeability of the electrolytic solution into the electrolyte. The liquid injection rate measuring cell 40 includes an electrolytic solution 43, an electrolyte 44, an electron conductor layer 48, and a current collector 49. In this liquid injection speed measuring cell 40, an electrolyte 44 is disposed between two electron conductor layers 48 connected to a current collector 49, and the ionic resistance when the electrolyte 43 penetrates the electrolyte 44 is measured via the current collector 49. The cell to be measured. PVdF-HFP film (5 μm thickness) as the electrolyte 44, porous Al foil (45 μm thickness, porosity 50 volume%) as the electron conductor layer 48, and 1M-LiPF ₆ / (EC + DMC + EMC) as described above. The cell of Experimental Example 6 was obtained. A cell similar to Experimental Example 6 was used as Experimental Example 7 except that a non-porous Al foil was used instead of the porous Al foil. The resistance of the electrolyte 44 in the injection rate measurement cell 40 was evaluated by sealing the electrolyte solution 43 immediately after injecting the electrolyte solution 43 into the cell and measuring the ionic resistance at a predetermined time interval at 25 ° C. by the AC impedance method.

(Results and discussion)
Table 2 shows the permeation time (h) of the electrolyte solution of Experimental Examples 6 and 7 and the material of the electron conductor layer. FIG. 8 is a graph showing the relationship between the penetration time of the electrolytic solution into the electrolyte and the ionic resistance of the electrolyte. As shown in FIG. 8, in Experimental Example 6, the ionic resistance of the film decreased with time. This is because the electrolyte is impregnated with the electrolyte through the porous electron conductor layer, and ions can be conducted in the electrolyte membrane. When the permeation time was 10 hours or longer, the ionic resistance of the electrolyte became constant. This was presumed to be because the amount of electrolyte impregnated in the electrolyte was saturated. Assuming that the time required for the ionic resistance of the electrolyte to be constant is the injection time, when the porous Al foil was used as the electron conductor layer, the injection time was 10 hours. On the other hand, in Experimental Example 7 using the non-porous Al foil, the injection time was 33 hours, and it was found that the injection time was longer than when the porous Al foil was used. In Experimental Examples 6 and 7, there is no difference in charge / discharge characteristics after the injection is completed.

  Here, the secondary batteries of Experimental Examples 1 to 5 will be considered. FIG. 9 is a schematic view showing that the electrolytic solution penetrates into the electron conductor layer 28 (electrolyte 24). FIG. 9A is a view of the secondary battery 20 using the porous electron conductor layer 28, and FIG. It is a figure of the secondary battery 20C using the non-porous electronic conductor layer 28C. Injection of the electrolytic solution of the secondary battery 20 is performed in a state where the cells are restrained and the columnar electrode assemblies are in close contact with each other. As shown in FIG. 9B, when the non-porous electron conductor layer 28 </ b> C is used, the electrolytic solution diffuses only in the pores of the second electrode 22 and penetrates into the electrolyte 24. On the other hand, as shown in FIG. 9A, when the porous electron conductor layer 28 is used, the electrolyte solution diffuses through the holes in the electron conductor layer 28 in addition to the holes in the composite material of the second electrode 22. To do. For this reason, it has been found that the use of the porous electron conductor layer 28 can shorten the time for injecting the electrolyte into the electrolyte 24. Thus, based on the difference in the diffusion path of the electrolytic solution, it has been found that it is preferable to provide a porous electron conductor layer in order to increase the injection rate of the electrolytic solution.

  In addition, this indication is not limited to the Example mentioned above at all, and as long as it belongs to the technical scope of this indication, it cannot be overemphasized that it can implement with a various aspect.

DESCRIPTION OF SYMBOLS 10 Columnar electrode assembly, 10B Columnar electrode structure, 11 1st electrode, 12 2nd electrode layer, 13 Support body, 14 Electrolyte layer, 20, 20B, 20C Secondary battery, 21 1st electrode, 22 2nd electrode, 24 Electrolyte, 25 Electrode body, 26 Connecting portion, 27 Current collecting tab, 28, 28B, 28C Electron conductor layer, 29 Current collecting tab, 30 Secondary battery, 40 Injection rate measuring cell, 43 Electrolytic solution, 44 Electrolyte, 48 Electron conductor layer, 49 Current collector.

Claims (8)

A plurality of columnar first electrodes including a first electrode active material and arranged at predetermined intervals in a predetermined direction; a second electrode including a second electrode active material and disposed opposite to the first electrode; A plurality of columnar electrode structures having conductivity and covering the first electrode and interposing between the first electrode and the second electrode;
An electron conductor layer interposed between the columnar electrode structure and the columnar electrode structure;
Secondary battery equipped with.   2. The secondary battery according to claim 1, wherein the columnar electrode structure is a columnar electrode assembly that includes at least the electrolyte and further includes a connecting portion that connects the first electrode and the first electrode. The columnar electrode assembly comprises a laminate in which the first electrodes are arranged in a planar shape and two or more columnar electrode assemblies are laminated,
The secondary battery according to claim 2, wherein the electron conductor layer is also formed on the outermost peripheral surface of the laminate and / or the outermost peripheral surface of the columnar electrode assembly.   The secondary battery according to claim 1, wherein the electron conductor layer is porous.   The secondary battery according to claim 4, wherein the electron conductor layer has a porosity in a range of 30% by volume to 95% by volume.   The secondary battery according to claim 1, wherein the electron conductor layer has a thickness in a range of 0.1 μm to 20 μm. The secondary battery according to any one of claims 1 to 6, which satisfies at least one of the following (1) to (4).
(1) The first electrode has a diameter D (μm) in a range of 20 μm to 800 μm.
(2) The second electrode has a thickness T (μm) in the range of 5 μm to 200 μm.
(3) The electrolyte has a thickness t (μm) in the range of 2 μm to 15 μm.
(4) The electrolyte is formed in layers on the first electrode, and the second electrode is formed in layers on the electrolyte. The first electrode is a negative electrode including a carbonaceous material as the first electrode active material,
The secondary battery according to any one of claims 1 to 7, wherein the second electrode is a positive electrode of a composite layer formed on the surface of the electrolyte.

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