JP6631568B2 - Secondary battery and method of manufacturing the same - Google Patents

Description

  The invention disclosed in this specification relates to a secondary battery and a method for manufacturing the same.

  Conventionally, as a secondary battery of this type, a lithium ion supply core portion containing an electrolyte, and a current collector having a three-dimensional network structure formed around the outer surface of the child tab and coated with an internal electrode active material on the outer surface are used. A cable type secondary battery including an internal electrode including the external electrode and an external electrode formed around the outer surface of the internal electrode and including an external electrode active material layer has been proposed (for example, see Patent Document 1). In this secondary battery, the electrolyte in the core portion easily penetrates into the active material of the electrode, and the battery has excellent capacity characteristics and cycle characteristics.

JP 2014-532277 A

  By the way, in recent years, lithium secondary batteries have been desired to have higher capacity and higher energy density per unit volume. For example, in order to increase the battery capacity of a secondary battery in which electrodes are stacked, it is necessary to increase the thickness of the active material layer. Flow path becomes longer, and it becomes difficult to reduce the ion concentration gradient in the thickness direction. In the lithium ion secondary battery of Patent Literature 1 described above, increasing the energy density has not been sufficiently studied.

  The present disclosure has been made in view of such a problem, and has as its main object to provide a novel secondary battery that can further increase energy density.

  The inventors of the present invention have conducted intensive studies to achieve the above-described object. As a result, the present inventors have found that a structure in which a plurality of pillar-shaped electrodes are bound and connected to a current collecting portion can further increase the energy density. And completed the invention disclosed in this specification.

That is, the secondary battery disclosed in this specification is:
A first electrode which is a columnar body having a first active material;
A first current collector connected to the first electrode;
A second electrode having a second active material;
A second current collector connected to the second electrode;
A separation membrane having ion conductivity and insulating the first electrode and the second electrode,
It has a structure in which a plurality of the first electrodes are bound in a state of being adjacent to the second electrode via the separation film.

The method for manufacturing a secondary battery disclosed in the present specification,
A separation film forming step of forming a separation film having ion conductivity and insulation on the surface of the first electrode which is a columnar body having the first active material;
A binding step of binding a plurality of the first electrodes in a state of being adjacent to the second electrode having a second active material via the formed separation film;
Is included.

  The present disclosure can provide a secondary battery with higher energy density and a method for manufacturing the same. The reason why such an effect is obtained is presumed as follows. For example, in a conventional electrode structure in which an active material is formed on a metal foil current collector and laminated via a separator, in order to increase the energy density, the application amount and the density of the electrode mixture on the current collector foil are increased. And harmful effects such as a decrease in ionic conductivity may occur. On the other hand, in the secondary battery of the present disclosure, by adopting a structure in which the columnar electrodes are bound, the conduction distance of ions can be further reduced. Further, in the secondary battery of the present disclosure, it is not necessary to provide a current collector inside the structure, and further increase the space occupation ratio of the active material by, for example, changing the separator or the like to a separation membrane to make it thinner. Can be. Therefore, it is presumed that the energy density can be further increased.

FIG. 2 is a schematic diagram illustrating an example of a secondary battery 10. FIG. 2 is a sectional view of the secondary battery 10 taken along line AA. FIG. 2 is a plan view of the secondary battery 10. Sectional drawing which shows an example of the secondary batteries 10B-10E. FIG. 2 is a schematic diagram showing an example of a secondary battery 30. FIG. 2 is a cross-sectional view of the secondary battery 30 taken along line AA. Explanatory drawing which shows an example of the manufacturing process of the secondary battery 30. The schematic diagram which shows an example of the secondary battery 30B. AA sectional view of the secondary battery 30B. The schematic diagram which shows an example of the secondary battery 10F. FIG. 4 is a graph showing the relationship between the length of one side of an electrode, the volume fraction of the positive and negative electrode mixture, the positive and negative electrode facing areas, and the distance between the positive and negative electrodes at 80% by volume of the electrode. FIG. 6 is a diagram showing the relationship between the volume fraction of the positive and negative electrode mixture, the positive and negative electrode facing areas, and the distance between the positive and negative electrodes at 80% by volume of the electrodes in the columnar body binding structure and the electrode foil laminated structure. FIG. 5 is a diagram showing the relationship between the volume fraction of the positive / negative electrode mixture, the positive / negative electrode facing area, and the cell energy density in the columnar body binding structure and the electrode foil laminated structure. FIG. 4 is a diagram illustrating the relationship between the diameter of a fibrous negative electrode active material and the facing area of electrodes. FIG. 4 is a diagram showing the relationship between the thickness of the composite material and the electrode facing area in a conventional structure in which current collecting foils are laminated.

  The secondary battery described in the embodiment includes a first electrode that is a columnar body, a first current collector, a first connection, a second electrode, a second current collector, a second connection, And a separation membrane. In this secondary battery, the first electrode may be a positive electrode including a positive electrode active material as a first active material, and the second electrode may be a negative electrode including a negative electrode active material as a second active material. Alternatively, in this secondary battery, the first electrode may be a negative electrode including a negative electrode active material, and the second electrode may be a positive electrode including a positive electrode active material. Each electrode may include a conductive material and a binder in addition to the active material. The first electrode may be a columnar body such as a cylinder or a polygonal column, and the second electrode may be a columnar body such as a cylinder or a polygonal column. Further, at least one of the first electrode and the second electrode may be columnar, and the other may not be columnar. In addition, the first electrode may have a current collecting member embedded therein, which is at least one of a current collecting wire, a current collecting foil, and a three-dimensional network structure, or may not include the current collecting member. Good. The second electrode may have at least one of the current collector, the current collector foil, and the three-dimensional network structure embedded therein, or may not include the current collector. Here, for convenience of explanation, a description will be given below of a lithium secondary battery in which the first electrode 11 is a negative electrode, the second electrode 16 is a positive electrode, and lithium ions are used as a carrier, as a main example.

(1st Embodiment)
Next, a secondary battery disclosed in the present embodiment will be described with reference to the drawings. FIG. 1 is a schematic diagram illustrating an example of the secondary battery 10. FIG. 2 is a sectional view taken along line AA of the secondary battery 10 of FIG. FIG. 3 is a plan view of the secondary battery 10. As shown in FIGS. 1 to 3, the secondary battery 10 includes a first electrode 11, a first current collector 12, a current collector 13, a first connection 14, a second electrode 16, It includes a current collector 17, a current collector 18, a second connection 19, and a separation membrane 21.

  The first electrode 11 is a pillar having a first active material. The first electrode 11 is a quadrangular prism having a rectangular cross section. The secondary battery 10 may have a structure in which 50 or more first electrodes 11 are bound. For example, the first electrodes 11 may have a capacitance of 1 / n of the cell capacitance, and n electrodes may be connected in parallel to the first current collector 12. The outer periphery of the first electrode 11 other than the end face is opposed to the second electrode 16 via the separation film 21. The first electrode 11 is preferably a columnar body having a length of one side of 100 μm or more and 300 μm or less in a direction orthogonal to the longitudinal direction. Within this range, the energy density per unit volume can be further increased. Alternatively, in this range, the movement distance of carrier ions can be further reduced, and charging and discharging can be performed with a larger current.

  Although the first electrode 11 contains the first active material, when the first active material does not have conductivity, it may be formed by mixing with, for example, a conductive material having conductivity. The first electrode 11 may be formed by, for example, mixing and molding a first active material, and if necessary, a conductive material and a binder. Examples of the first active material include a material capable of inserting and extracting lithium as a carrier. Examples of the first active material include inorganic compounds such as lithium metal, lithium alloy, and tin compound; carbonaceous materials capable of occluding and releasing lithium ions; composite oxides containing a plurality of elements; and conductive polymers. . Examples of the carbonaceous material include cokes, glassy carbons, graphites, non-graphitizable carbons, pyrolytic carbons, and carbon fibers. Of these, graphites such as artificial graphite and natural graphite are preferred. Further, carbon fibers having a graphite structure may be used. As such a carbon fiber, for example, one in which crystals are oriented in a longitudinal direction which is a fiber direction is preferable. Further, it is preferable that the crystals are radially oriented from the center to the outer peripheral surface side when viewed in a cross section in a direction orthogonal to the longitudinal direction (fiber direction) (see FIGS. 5 and 6 described later). Examples of the composite oxide include a lithium-titanium composite oxide and a lithium-vanadium composite oxide. The conductive material is not particularly limited as long as it is an electron conductive material that does not adversely affect the battery performance. One of black, carbon whiskers, 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 hold the first active material particles and the conductive material particles together and maintain a predetermined shape. For example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluororubber, etc. Or a thermoplastic resin such as polypropylene or polyethylene, an ethylene propylene diene monomer (EPDM) rubber, a sulfonated EPDM rubber, a natural butyl rubber (NBR), or the like can be used alone or as a mixture of two or more kinds. . Further, an aqueous dispersion of a cellulose-based or styrene-butadiene rubber (SBR) as an aqueous binder can be used.

  In the first electrode 11, the content of the first active material is preferably higher, and is preferably 70% by volume or more, more preferably 80% by volume or more based on the whole volume of the first electrode 11. preferable. The content of the conductive material is preferably in a range of 0% by volume or more and 20% by volume or less, and more preferably in a range of 0% by volume or more and 15% by volume or less based on the whole volume of the electrode mixture including the first active material. More preferably, there is. Within 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 volume to 5% by volume, and more preferably in the range of 0.2% by volume to 1% by volume, based on the entire volume of the first electrode 11. Is more preferable.

  A current collector 13 having a circular cross section is embedded inside the first electrode 11. The collecting wire 13 is preferably formed of a conductive material, for example, a metal such as aluminum, copper, titanium, stainless steel, nickel, iron, and platinum. The collecting wire 13 is drawn out to form a first connecting portion 14. The radial length (thickness) of the current collector 13 may be the same as or different from that of the first connection portion 14. The radial length of the current collector 13 is, for example, preferably 50 μm or less, more preferably 40 μm or less, and still more preferably 30 μm or less. It is preferable that the collector wire 13 be as thin as possible while ensuring conductivity, because the energy density per unit volume can be further improved. The radial length of the current collector 13 is, for example, preferably 1 μm or more, more preferably 5 μm or more, and further preferably 10 μm or more. The collector wire 13 is preferably thicker from the viewpoint of ensuring conductivity.

  The first current collector 12 is a member having conductivity, and is electrically connected to the first electrode 11. 50 or more first electrodes are connected in parallel to the first current collector 12 via a current collector 13. The first current collector 12 includes, for example, carbon paper, aluminum, copper, titanium, stainless steel, nickel, iron, platinum, calcined carbon, conductive polymer, conductive glass, and the like, as well as adhesiveness, conductivity, and the like. For the purpose of improving oxidation (reduction) resistance, a material 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 first current collector 12 is not particularly limited as long as the plurality of current collectors 13 can be connected. For example, a plate, foil, film, sheet, net, punch or expanded shape , A lath body, a porous body, a foam, a formed body of a fiber group, and the like.

  The second electrode 16 is a pillar having a second active material. The second electrode 16 is a quadrangular prism having a rectangular cross section. The secondary battery 10 may have a structure in which 50 or more second electrodes 16 are bound. For example, the second electrodes 16 may have a capacitance of 1 / n of the cell capacitance, and n electrodes may be connected in parallel to the second current collector 17. The outer periphery of the second electrode 16 other than the end face is opposed to the first electrode 11 via the separation film 21. The second electrode 16 is preferably a columnar body having a side of 100 μm or more and 300 μm or less in a direction perpendicular to the longitudinal direction. Within this range, the energy density per unit volume can be further increased. Alternatively, in this range, the movement distance of carrier ions can be further reduced, and charging and discharging can be performed with a larger current.

Although the second electrode 16 contains the second active material, when the second active material does not have conductivity, it may be formed by mixing with, for example, a conductive material having conductivity. The second electrode 16 may be formed, for example, by mixing the second active material, and if necessary, a conductive material and a binder. Examples of the second active material include a material capable of inserting and extracting lithium as a carrier. Examples of the second active material include a compound having lithium and a transition metal, for example, an oxide containing lithium and a transition metal element, a phosphate compound containing lithium and a transition metal element, and the like. Specifically, a lithium manganese composite oxide whose basic composition formula is Li _(1-x) MnO ₂ (0 <x <1, etc .; the same applies hereinafter), Li _(1-x) Mn ₂ O _4, etc. A lithium cobalt composite oxide whose formula is Li _(1-x) CoO ₂ , a lithium nickel composite oxide whose basic composition formula is Li _(1-x) NiO _2, etc., and a basic composition formula is Li _{(1-x) Co a Ni b Mn c O 2} (a> 0, b> 0, c> 0, a + b + c = 1) lithium-cobalt-nickel-manganese composite oxide, and the like, lithium vanadium composite to the basic formula, such as LiV ₂ O ₃ An oxide, a transition metal oxide whose basic composition formula is V ₂ O _5, or the like can be used. Further, a lithium iron phosphate compound having a basic composition formula of LiFePO ₄ can be used as the positive electrode active material. Among these, a lithium cobalt nickel manganese composite oxide, for example, LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ or LiNi _0.4 Co _0.3 Mn _0.3 O ₂ is preferable. The “basic composition formula” is intended to include other elements, for example, components such as Al and Mg.

  In the second electrode 16, the content of the second active material is preferably higher, and is preferably 70% by volume or more, more preferably 80% by volume or more based on the whole volume of the second electrode 16. preferable. The content of the conductive material is preferably in a range of 0% by volume to 20% by volume, more preferably in a range of 0% by volume to 15% by volume, based on the entire volume of the second electrode 16. . Within 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 volume to 5% by volume with respect to the entire volume of the second electrode 16, and in the range of 0.2% by volume to 1% by volume. Is more preferable.

  A collector wire 18 having a circular cross section is embedded in the second electrode 16. The collecting wire 18 is preferably formed of a conductive material, for example, a metal such as aluminum, copper, titanium, stainless steel, nickel, iron, and platinum. The collecting wire 18 is drawn out to form a second connecting portion 19. The radial length (thickness) of the current collector 18 is the same as that of the current collector 13.

  The second current collector 17 is a member having conductivity, and is electrically connected to the second electrode 16. Fifty or more second electrodes 16 are connected in parallel to the second current collector 17 via a current collector 18. The second current collector 17 may be a member similar to the first current collector 12.

  The separation film 21 has ion conductivity of ions (eg, lithium ions) serving as carriers and insulates the first electrode 11 from the second electrode 16. The separation film 21 is formed on the entire outer peripheral surface of the first electrode 11 facing the second electrode 16 and the entire outer peripheral surface of the second electrode 16 facing the first electrode 11. A short circuit with the second electrode 16 is prevented. The separation membrane 21 is preferably made of a polymer having ion conductivity and insulating properties. Examples of the separation membrane 21 include a copolymer of polyvinylidene fluoride (PVdF) and hexafluoropropylene (HFP), polymethyl methacrylate (PMMA), and a copolymer of PMMA and an acrylic polymer. . For example, in the case of a copolymer of PVdF and HFP, a part of the electrolyte swells and gels this film to form an ion conductive film. The thickness t of the separation membrane 21 is, for example, preferably 0.5 μm or more, more preferably 2 μm or more, and may be 5 μm or more. When the thickness t is 0.5 μm or more, it is preferable to secure insulation. The thickness t of the separation membrane 21 is preferably 20 μm or less, more preferably 10 μm or less. When the thickness t is 20 μm or less, it is preferable in that a decrease in ion conductivity can be suppressed. When the thickness t is in the range of 0.5 to 20 μm, ionic conductivity and insulation are suitable. The separation film 21 may be formed by, for example, immersing the first electrode 11 or the second electrode 16 in a solution containing a raw material and coating the surface thereof.

The separation membrane 21 may include an ion conductive medium that conducts ions serving as carriers. The ion conductive medium includes, for example, an electrolytic solution in which a supporting salt is dissolved in a solvent. Examples of the solvent for the electrolyte include a solvent for the non-aqueous electrolyte. Examples of the solvent include carbonates, esters, ethers, nitriles, furans, sulfolanes, dioxolanes, and the like, and these can be used alone or as a mixture. Specifically, cyclic carbonates such as ethylene carbonate (EC), propylene carbonate, vinylene carbonate, butylene carbonate, chloroethylene carbonate, dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate, and ethyl carbonate are used as carbonates. -N-butyl carbonate, methyl-t-butyl carbonate, di-i-propyl carbonate, chain carbonates such as t-butyl-i-propyl carbonate, γ-butyl lactone, cyclic esters such as γ-valerolactone, Chain esters such as methyl formate, methyl acetate, ethyl acetate, methyl butyrate, ethers such as dimethoxyethane, ethoxymethoxyethane, diethoxyethane, acetonitrile, benzonitrile, etc. Nitriles, furans such as tetrahydrofuran and methyltetrahydrofuran, sulfolane such as sulfolane and tetramethylsulfolane, and dioxolanes such as 1,3-dioxolan and methyldioxolan. The supporting salt contains, for example, ions that are carriers of the secondary battery 10. 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 , and LiSCN. , LiClO ₄ , LiCl, LiF, LiBr, LiI, LiAlCl _{4 and the} like. Among them, 1 is 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. It is preferable to use a combination of two or more kinds of salts in view of electric characteristics. The concentration of this supporting salt in the electrolytic solution is preferably from 0.1 mol / L to 5 mol / L, more preferably from 0.5 mol / L to 2 mol / L.

  As shown in FIGS. 1 to 3, the secondary battery 10 has a structure in which first electrodes 11 and second electrodes 16, which are columnar bodies, are alternately arranged and bound via a separation film 21. In this secondary battery 10, by forming the electrodes into micro-columns, each electrode can occlude and release carrier ions from the entire circumference (see FIG. 2). In this electrode structure, the carrier ions are absorbed and released from the entire circumference. In addition to promoting the reaction by increasing the positive and negative electrode facing areas, the amount of active material per facing area decreases toward the deep part (back side) ( The effect of improving the average reaction rate (decreasing the average distance between the positive and negative electrode active materials) due to the fact that the deeper the active material is, the more difficult it is to react) can be expected. Further, in the secondary battery 10, the length of one side of the columnar electrode is more preferably 100 μm to 300 μm. In this range, it is easy to secure a high energy density.

  In the secondary battery 10 described in detail above, a secondary battery with higher energy density can be provided. The reason why such an effect is obtained is presumed as follows. For example, in a conventional electrode structure in which an active material is formed on a metal foil current collector and laminated via a separator, in order to increase the energy density, the application amount and the density of the electrode mixture on the current collector foil are increased. And harmful effects such as a decrease in ionic conductivity may occur. On the other hand, in the secondary battery 10 of the present disclosure, by employing a structure in which the columnar electrodes are bound, the conduction distance of ions can be further reduced. Further, in the secondary battery of the present disclosure, it is not necessary to provide a foil-like current collector inside the structure.Furthermore, by changing the separator or the like to a separation membrane to make it thinner, the space occupancy of the active material can be reduced. Can be higher. Therefore, the energy density can be further increased.

  In the above-described secondary battery 10, the collector wires 13 and the collector wires 18 have been described as having a circular cross section, but are not particularly limited thereto. FIG. 4 is a cross-sectional view illustrating an example of the secondary batteries 10B to 10E. For example, the secondary battery 10B includes current collector foils 13B and 18B arranged diagonally in the cross section of each electrode. Further, the secondary battery 10C includes current collector foils 13C and 18C that are horizontally arranged in the cross section of each electrode. In addition, the secondary battery 10D includes current collector foils 13D and 18D that are vertically arranged in a cross section of each electrode. The secondary battery 10E includes current collecting members 13E and 18E, which are three-dimensional network structures, inside each electrode. Also in such secondary batteries 10B to 10E, the energy density can be further increased by employing a structure in which the columnar electrodes are bound.

(2nd Embodiment)
Next, the secondary battery 30 will be described. FIG. 5 is a schematic diagram showing an example of the secondary battery 30. FIG. 6 is a sectional view taken along line AA of the secondary battery 30 of FIG. As shown in FIGS. 5 and 6, the secondary battery 30 includes a first electrode 31, a first current collector 32, a current collector 33, a first connector 34, a second electrode 36, and a second electrode 36. It includes a current collector 37 and a separation film 41. The secondary battery 30 includes a first electrode 31 having a columnar shape with a circular cross section, and a second electrode 36 formed by an active material layer including a second active material formed around the first electrode 31. It has. That is, the secondary battery 30 has a structure in which the second electrode 36 is not a columnar body. In the secondary battery 30, the materials constituting each component are the same as those of the secondary battery 10, and the description is omitted.

  The first electrode 31 is a columnar body having a first active material and having a circular cross section. The secondary battery 30 may have a structure in which 50 or more first electrodes 31 are bound. The outer periphery of the first electrode 31 other than the end face is opposed to the second electrode 36 via the separation film 21. The first electrode 31 is preferably a cylindrical body having a radial length (thickness) of 10 μm or more and 200 μm or less. Within this range, the energy density per unit volume can be further increased. Alternatively, in this range, the movement distance of carrier ions can be further reduced, and charging and discharging can be performed with a larger current. This first active material may be a fibrous or columnar carbon fiber. This carbon fiber is preferably a highly crystalline carbon fiber in which the graphene structure is radially oriented from the center to the outer peripheral direction and is also oriented in the fiber length direction. Such a carbon fiber is preferable because it can occlude and release lithium ions as carriers from the outer periphery and has high ion conductivity. In the first electrode 31, the electrode itself has conductivity, and the burying of a current collector or the like is omitted.

  The second electrode 36 has the second active material, and is formed on the outer periphery of the first electrode 31 via the separation film 41. The second electrode 36 has a hexagonal outer shape in cross section, and includes the first electrode 31 having a columnar shape. The second electrode 36 may be filled between the first electrodes 31, and the outer shape is not particularly limited to a hexagonal shape. The second electrode 36 itself has conductivity, and the current collecting member is omitted. The end face of the second electrode 36 is directly connected to the second current collector 37. The second electrode 36 may be formed, for example, by forming a separation film 41 on the outer periphery of the first electrode 31 and then applying a material for the second electrode 36 on the outer periphery.

  The separation film 41 has ion conductivity of ions (for example, lithium ions) serving as carriers and insulates the first electrode 31 from the second electrode 36. The separation film 41 is formed on the entire outer peripheral surface of the first electrode 31 facing the second electrode 36, and prevents a short circuit between the first electrode 31 and the second electrode 36.

  Since the secondary battery 30 has a structure in which the columnar first electrodes 31 are bound like the secondary battery 10, each electrode can occlude and release carrier ions from the entire circumference. For this reason, in the secondary battery 30, in addition to the promotion of the reaction due to the increase in the positive and negative electrode facing areas, the effect of improving the average reaction rate due to the decrease in the amount of active material per facing area as it goes deeper (toward the back) is expected. it can.

  Next, a method for manufacturing a secondary battery will be described. This manufacturing method includes a separation membrane forming step and a binding step. In the separation film forming step, a separation film having ion conductivity and insulation is formed on the surface of the first electrode which is a columnar body having the first active material. In the binding step, the plurality of first electrodes are bound in a state of being adjacent to the second electrode having the second active material via the formed separation film. Here, a manufacturing process of the secondary battery 30 will be described as a specific example. 7A and 7B are explanatory diagrams illustrating an example of a manufacturing process of the secondary battery 30. FIG. 7A illustrates a heat treatment process, FIG. 7B illustrates a separation film forming process, and FIG. 7C illustrates a second active material. FIG. 7 (d) shows a conductive material adding step, and FIG. 7 (e) shows a binding step. In the heat treatment step, the raw material of the carbon fiber is heat-treated to produce highly oriented carbon fiber oriented in the fiber length direction and the outer peripheral surface. Next, a separation membrane is formed on the outer surface of the carbon fiber. The material for the separation membrane may be applied and dried. Next, a second active material is formed on the separation membrane. The second active material may be, for example, a material in which a conductive material or a binder is attached to fine particles of the active material. Such second active material particles may be made into a slurry state and applied on a separation membrane. Next, a process of adding a conductive material as necessary is performed. As the conductive material, a carbon material or metal particles (eg, Cu, Ni, Al, etc.) may be used. Then, a plurality of columnar bodies of the first electrode manufactured as described above are arranged and bound. Thus, the secondary battery 30 can be manufactured.

  Note that the present disclosure is not limited to the above-described embodiments at all, and it goes without saying that the present disclosure can be implemented in various modes as long as it belongs to the technical scope of the present disclosure.

  For example, in the above-described embodiment, in the secondary battery 30, the first electrode 31 is described as having no current collector. However, the present invention is not limited to this, and each electrode may have the current collector 33 embedded therein. Good. FIG. 8 is a schematic diagram illustrating an example of the secondary battery 30B. FIG. 9 is a cross-sectional view of the secondary battery 30B taken along line AA of FIG. A collector wire 33 having a circular cross section is embedded inside the first electrode 31. The current collecting wire 33 is drawn out to form a first connecting portion 34. The radial length (thickness) of the collecting wire 33 may be the same as or different from the first connecting portion 34. The diameter of the collecting wire 33 is, for example, preferably 50 μm or less, more preferably 40 μm or less, and further preferably 30 μm or less. It is preferable that the collector wire 33 be as thin as possible while ensuring conductivity, because the energy density per unit volume can be further improved. The radial length of the current collector 33 is, for example, preferably 1 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more. The collecting wire 33 is preferably thicker from the viewpoint of ensuring conductivity. In the secondary battery 30B, the first electrode 31 may be formed, for example, by forming a carbon material on the surface of the current collector 33 and then performing a heat treatment to increase the crystallization and orientation of the graphene structure.

  Similarly, in the secondary battery 10, the first electrode 11 has the collector 13 and the second electrode 16 has the collector 18. However, the present invention is not limited to this. May be omitted. FIG. 10 is a schematic diagram illustrating an example of the secondary battery 10F. In this secondary battery 10F, the collector electrode 13 is omitted because the first electrode 11 itself has conductivity. The first electrode 11 is electrically connected directly to the first current collector 12, and an end of the first electrode 11 constitutes a first connection portion 14 </ b> F. The second electrode 16 is omitted because the current collecting line 18 is omitted because the second electrode 16 itself has conductivity. The second electrode 16 is directly and electrically connected to the second current collector 17, and an end of the second electrode 16 constitutes a second connection 19 </ b> F. In the secondary battery 10F, since the internal structure has no current collector, the energy density can be further increased.

  In the above-described secondary battery 10, the first electrode 11 is a negative electrode and the second electrode 16 is a positive electrode. However, the present invention is not limited to this. The first electrode may be a positive electrode and the second electrode may be a negative electrode. In the above-described embodiment, the carrier of the secondary battery is lithium ion. However, the present invention is not particularly limited thereto. Good. Further, although the electrolytic solution is a non-aqueous electrolytic solution, it may be an aqueous electrolytic solution.

  Hereinafter, an example in which the above-described secondary battery is specifically manufactured will be described as an example.

[Example 1]
A secondary battery 10 having the structure shown in FIG. 1 was manufactured. First, a 30 mm long square pole electrode having a metal current collecting wire having a side of 200 μm and a diameter of 50 μm was prepared as a positive electrode and a negative electrode. The production was performed by extrusion molding. The positive electrode was formed by mixing Li (Ni, Co, Mn) O ₂ as a positive electrode active material, acetylene black as a conductive material, and PVdF as a binder at a mass ratio of 90/7/3. Produced. The negative electrode was produced by molding a mixture of graphite as the negative electrode active material and PVdF as the binder at a mass ratio of 97/3. A PVdF-HFP film was applied to the outer periphery of these electrodes by dip coating to a thickness of 10 μm. Next, 50 sets of positive / negative electrodes were arranged in a grid pattern and bound, thereby forming an electrode structure in which wire-like current collectors were connected in parallel to a current collector plate. At this time, 3 mm of the wire was left as a connection portion. Put the electrode structure AL laminated bag, after impregnation the electrolyte _{(1M-LiPF 6 / EC +} EMC + DMC), sealed, and the resulting secondary battery was as in Example 1.

11 shows the length of one side of the electrode, the volume fraction of the positive and negative electrode mixture, the positive and negative electrode facing area, and the distance between the positive and negative electrodes at 80% by volume of the electrode in the secondary battery 10 shown in FIG. FIG. 9 is a relationship diagram obtained by calculation. In FIG. 11, the calculation was performed on the assumption that the thickness of the separation membrane was 5 μm, 10 μm, 15 μm, and 20 μm. As shown in FIG. 11, when the length of one side of the electrode is in the range of 100 to 300 μm, the volume fraction exceeds 85%, the facing area exceeds 50 cm ² , the distance between the positive and negative sides falls below 150 μm, and the high energy density increases. And a high output.

FIG. 12 is a relationship diagram obtained by calculating the volume fraction of the positive / negative electrode mixture, the positive / negative electrode facing area, and the distance between the positive / negative electrodes at 80% by volume of the electrodes in the columnar body binding structure and the electrode foil laminated structure. . Examples 2 to 4 were calculated using the lengths of the sides of the positive electrode and the negative electrode, the thickness of the separation membrane, the diameter of the current collector, and the like shown in FIG. Comparative Example 1 was a conventional electrode having a laminated structure, and Comparative Example 2 was a model of a high-energy type electrode in which the thickness of an electrode mixture of the conventional electrode was increased. As shown in the table of FIG. 12, in Examples 2 to 4, the volume fraction of the positive / negative electrode mixture in the electrode exceeded 85%, and was almost equivalent to 88.4% of Comparative Example 2 having a thicker film (energy). (High density). Further, in Examples 2 to 4, the facing areas of the positive and negative electrodes exceeded 47.3 cm ^{2 of} Comparative Example 2, which proved to be advantageous for high output and rapid charging. Furthermore, in Examples 2 to 4, the distance between the positive electrode and the negative electrode of the active material occupying 80% by volume was 120 μm or less (the moving distance of ions was shorter), which proved to be advantageous for rapid charging. It has been found that these effects are further enhanced when one side of the columnar electrode is reduced to about 100 μm.

FIG. 13 shows, by calculation, the volume fraction of the positive / negative electrode mixture, the positive / negative electrode facing area, and the distance between the positive / negative electrodes at 80% by volume of the electrodes in the secondary battery 30 in the binding structure of the columnar body and the laminated structure of the electrode foil. FIG. Examples 5 and 6 were calculated using the diameter A of the negative electrode, the thickness X of the positive electrode, the thickness t of the separation membrane, and the like shown in FIG. Comparative Example 3 was a high-energy type electrode obtained by increasing the thickness of the electrode mixture of the conventional electrode, and Comparative Example 4 was a model of a conventional electrode having a laminated structure. Reference Example 1 considers the case where the capacity of the positive and negative electrodes was increased as compared with the conventional case. As shown in FIG. 13, when the structure of the secondary battery 30 is adopted, when the diameter of the negative electrode is set to 20 to 50 μm and the thickness of the positive electrode is set to 5 to 15 μm, the cell energy density is set to 650 Wh / L or more. It was found that the facing area could be 300 cm ² or more.

[Example 7]
A secondary battery 30 having the structure shown in FIG. 5 was manufactured. First, a highly crystalline carbon fiber having a diameter of 50 μm, in which graphene is oriented from the center to the outer periphery and also in the length direction, is cut into 10 cm (longitudinal direction of the cell) to obtain a negative electrode (negative electrode active material). . PVdF-HFP was applied as a separation membrane (electrolyte membrane) to the outer periphery of the carbon fiber by dip coating so as to have a thickness of 5 μm, and dried. A positive electrode slurry was dip-coated on the outer periphery of the carbon fiber to dry and increase the density. The positive electrode slurry was prepared by mixing Li (Ni, Co, Mn) O ₂ as a positive electrode active material, acetylene black as a conductive material, and PVdF as a binder at a mass ratio of 90/7/3. What was mixed with the solvent was used. The coating amount of the positive electrode slurry was adjusted so that the positive / negative electrode capacity ratio became 1.0. The number (for example, 50) of these carbon fibers is bundled to be the cell capacity, and the density is increased to such an extent that the gap between the bundled columnar electrodes becomes substantially equal to the porosity in the positive electrode, thereby improving the electron conductivity of the positive electrode. Was. Next, a metal was arranged on the end face of the carbon fiber of the negative electrode, melted and fixed, and joined in parallel. The resulting electrode structure was placed in AL laminated bag, after impregnation the electrolyte _{(1M-LiPF 6 / EC +} EMC + DMC), sealed, and the resulting secondary battery was as in Example 7.

FIG. 14 is a diagram showing the relationship between the diameter of the fibrous negative electrode active material and the facing area of the electrodes. FIG. 15 is a diagram showing the relationship between the film thickness of the composite material and the electrode facing area in the conventional structure in which current collecting foils are laminated. Here, the energy density of the secondary battery 30 was studied in more detail. In FIG. 14, the thickness t of the separation membrane was 5 μm, and the facing area and the energy density of the electrodes when the fiber diameter of the negative electrode active material was changed were calculated. In FIG. 15, the calculation was performed with the separation film thickness t set to 5 μm, the positive electrode current collector foil thickness B set to 12 μm, and the negative electrode current collector foil thickness D set to 10 μm. As shown in FIG. 14, when the fiber diameter is in the range of 10 μm to 200 μm, the electrode facing area is 100 cm ² or more, that is, the area where carrier ions enter and exit increases, and the energy density is 700 Wh / L or more. It has been found that density is feasible. In addition, it was found that this secondary battery 30 exhibited a maximum of 1210 Wh / L. On the other hand, as shown in FIG. 15, in the conventional laminated structure, the thickness of the composite material having an electrode facing area of 100 cm ² or more and an energy density of 700 Wh / L or more is 25 to 50 μm, and the energy density is 810 Wh at the maximum. / L, indicating that it is difficult to obtain a high energy density.

  As described above, the electrode structure of the example uses the positive electrode active material, the negative electrode active material, and the organic electrolyte used for the Li battery, and has an energy density of 600 Wh / L (electrode combination) suitable for EV vehicles. High output, quick chargeability, and high safety can be achieved while improving the volume fraction of the material to about 88%).

  It is needless to say that the present disclosure is not limited to the above-described embodiments, and can be implemented in various modes as long as they belong to the technical scope of the present disclosure.

For example, the shape of each electrode may be not only a square pole but also a circle or a hexagon regardless of the manufacturing process. The current collecting member may be a foam metal or the like instead of the current collecting wire. The separation membrane covering the electrode may be a solid electrolyte (oxide, sulfide), a gel polymer electrolyte, or an intrinsic polymer electrolyte (PEO, etc.) without being a polymer electrolyte. The electrolyte may not be the LiPF _6- based electrolyte used in the Li battery, but may be an aqueous electrolyte, a concentrated organic electrolyte, a non-flammable organic electrolyte using a non-flammable solvent as a solvent, or a solid. An electrolyte (all-solid-state battery) may be used.

  10, 10B to F, 30, 30B secondary battery, 11, 31 first electrode, 12, 32 first current collector, 13, 33 current collector, 13B to 13D current collector foil, 13E current collector, 14, 14F , 34 1st connection part, 16, 36 2nd electrode, 17, 37 2nd collector part, 18 collector wires, 18B-18D collector foil, 18E collector member, 19, 19F 2nd connection part, 21, 41 Separation membrane.

Claims (9)

A first electrode that is a columnar body or a polygonal pillar having a side length or a radial length of 10 μm or more and 300 μm or less having the first active material;
A first current collector connected to the first electrode;
A second electrode having a second active material;
A second current collector connected to the second electrode;
A separation membrane having ion conductivity and insulating the first electrode and the second electrode,
A structure in which a plurality of the first electrodes are bound in a state of being adjacent to the second electrode via the separation film;
The second electrode is formed by an active material layer including the second active material formed around the first electrode;
An outer periphery other than an end face of the first electrode is opposed to the second electrode via the separation membrane;
50 or more first electrodes are connected in parallel to the first current collector.
Secondary battery. 2. The secondary battery according to claim 1, wherein the first electrode has a carbon material in which crystals are oriented in a longitudinal direction as the first active material. 3. The first electrode may crystals when viewed in cross section in a direction perpendicular to the longitudinal direction has a carbon material oriented radially to the outer peripheral surface side from the center as the first active material, according to claim 1 or 2 two Next battery. The first electrode includes a carbon fiber as the first active material, the diameter of the carbon fiber is 200μm or less in the range of 10 [mu] m, the secondary battery according to any one of claims 1-3.   The secondary battery according to claim 1, wherein the separation membrane is formed with a thickness t of 0.5 μm or more and 20 μm or less. A separation film forming step of forming a separation film having ion conductivity and insulation on the surface of the first electrode which is a columnar body having the first active material;
A second active material forming step of forming a second active material constituting a second electrode on the separation film;
A binding step of binding a plurality of the first electrode in a state fit Ri said second active material Togatonari and the first active material through the pre-SL component separation membrane,
A method for manufacturing a secondary battery including:   In the separation membrane forming step, a first electrode that is a columnar body or a polygonal pillar having a side length or a radial length of 10 μm or more and 300 μm or less is used, and other than the end surface of the first electrode. The method for manufacturing a secondary battery according to claim 6, wherein the separation membrane is formed on an outer periphery.   The method for manufacturing a secondary battery according to claim 6, wherein in the binding step, 50 or more of the first electrodes are bound, and the first electrodes are connected in parallel to a first current collector.   9. The method for manufacturing a secondary battery according to claim 6, wherein, in the separation film forming step, the separation film is formed with a thickness t in a range from 0.5 μm to 20 μm.