JP7059988B2 - Secondary battery - Google Patents

Description

The invention disclosed herein relates to a secondary battery.

Conventionally, as a secondary battery, a battery using a honeycomb structure current collector in which a titanium nitride film is adhered to the partition wall surface of a cell including the outer surface of the carbonaceous honeycomb structure (Patent Document 1), or lithium containing an electrolyte. An internal electrode formed by surrounding the outer surface of the ion supply core portion and the lithium ion supply core portion, a separation layer formed by surrounding the outer surface of the internal electrode, and an external electrode formed by surrounding the outer surface of the separation layer. (Patent Document 2) and the like are known. Further, as a secondary battery having a high energy density, a plurality of columnar negative electrodes, a separation film provided so as to surround each columnar negative electrode, and a positive electrode provided so as to fill the space between adjacent separation films. Is known (Patent Document 3). This secondary battery has a structure in which a columnar negative electrode surrounded by a separation membrane is arranged in the positive electrode. The positive electrode of this secondary battery is obtained by spatially filling a columnar positive electrode made of a regular hexagonal column, and the columnar negative electrode surrounded by a separation membrane is arranged in the central hole of the columnar positive electrode.

Japanese Unexamined Patent Publication No. 2001-126736 Japanese Patent Publication No. 2014-532277 Japanese Unexamined Patent Publication No. 2018-152229

However, in the secondary battery of Patent Document 3, since the positive electrode current collecting structure is such that one end face of the columnar positive electrode is connected to the metal collecting plate, the current collecting cannot be performed efficiently and the weight is heavy. It could not be said that the energy density and the volume energy density were sufficiently high.

The present disclosure has been made in view of such a problem, and an object of the present disclosure is to sufficiently increase the energy density in a secondary battery in which a columnar negative electrode surrounded by a separation membrane is arranged in a positive electrode.

In order to achieve the above-mentioned object, the present inventors sufficiently improve the energy density by devising the positive electrode current collecting structure in the secondary battery in which the columnar negative electrode surrounded by the separation film is arranged in the positive electrode. We have found that it can be enhanced, and have completed the invention disclosed in the present specification.

That is, the secondary battery disclosed in this specification is
Multiple columnar negative electrodes containing negative electrode active material,
A separation membrane provided so as to surround each columnar negative electrode,
A positive electrode containing a positive electrode active material and provided so as to fill the space between adjacent separation membranes,
A plurality of positive electrode conductive patterns arranged in a direction intersecting the columnar negative electrode inside the positive electrode, and
A first positive electrode current collector layer provided so as to cover an exposed surface on which one end surface of the positive electrode conductive pattern of the positive electrode is exposed.
A plurality of second positive electrode current collector layers intermittently provided on the first positive electrode current collector layer, and
A third current collector layer, which is provided so as to bridge the second positive electrode current collector layer without contacting the first positive electrode current collector layer, and has a smaller number than the second current collector layer.
Equipped with
The electric resistance Rc1 of the current path of the first positive electrode current collector layer, the electric resistance Rc2 of the current path of the second positive electrode current collector layer, and the electric resistance Rc3 of the current path of the third positive electrode current collector layer are Rc1>. Satisfy the relationship of Rc2> Rc3,
It is a thing.

According to this secondary battery, since the positive electrode can be efficiently collected, the weight energy density and the volume energy density can be sufficiently increased. When the positive electrode current collecting structure is only the first positive electrode current collecting layer, the electric resistance of the path through which the current flows through the first positive electrode current collecting layer is high, so that the current from all the positive electrode conductive patterns is practically reduced in voltage. It is difficult to flow in the range. However, here, the positive electrode current collecting structure is provided with a first positive electrode current collecting layer, a low resistance second positive electrode current collecting layer intermittently provided on the first positive electrode current collecting layer, and a second positive electrode current collecting layer. Since it is composed of a third positive electrode current collector layer having a lower resistance provided on the layer, currents from all the positive electrode conductive patterns are collected from the first positive electrode current collector layer, the second positive electrode current collector layer, and the third positive electrode current collector. Current can be collected with relatively low electrical resistance via the layers in that order. As a result, currents from all positive electrode conductive patterns can flow within a practical voltage drop range. Therefore, in a secondary battery in which a columnar negative electrode surrounded by a separation membrane is arranged in the positive electrode, the energy density can be sufficiently increased.

In the secondary battery disclosed herein, the electrical resistance Rc1 is said to pass from the end face of the positive electrode conductive pattern that does not overlap with the second positive electrode current collector layer via the first positive electrode current collector layer. It is the electric resistance of the shortest path to the second positive electrode current collecting layer (for example, the center line of the second positive electrode collecting layer), and the electric resistance Rc2 is the second positive electrode collecting from the end of the second positive electrode collecting layer. It is the electric resistance of the path from the electric layer to the third positive electrode current collecting layer (for example, the center line of the third positive electrode collecting layer), and the electric resistance Ra3 is from one end of the third positive electrode collecting layer. It may be the electrical resistance of the path leading to the other end.

In the secondary battery disclosed in the present specification, the ratio of the electric resistance Rc2 to the electric resistance Rc1 is 0.1 or less, and the ratio of the electric resistance Rc3 to the electric resistance Rc2 is 0.1 or less. preferable. In this way, the energy density can be further increased.

In the secondary battery disclosed in the present specification, the end face of the positive electrode conductive pattern is periodically arranged on the exposed surface, and the second positive electrode current collecting layer is a plurality of the positive electrodes arranged in the same straight line. It may be provided so as to be parallel to the end surface of the conductive pattern and to keep the distance between the second positive electrode current collecting layers adjacent to each other constant. By doing so, the second positive electrode current collector layer has a periodic structure and is easy to manufacture.

In the secondary battery disclosed in the present specification, the third positive electrode current collector layer may be a single conductive wire provided so as to bridge the second positive electrode current collector layer. By doing so, the configuration is simplified as compared with the case where a plurality of third positive electrode current collector layers are present.

In the secondary battery disclosed in the present specification, the positive electrode is obtained by space-filling a plurality of columnar positive electrodes composed of positive polygonal columns that can be space-filled, and the columnar negative electrode surrounded by the separation film. May be arranged in the central hole of the columnar positive electrode. In this way, the positive electrode can be manufactured relatively easily. In addition, "space filling" means filling the space with a three-dimensional object without any gaps.

The secondary battery disclosed in the present specification may be an all-solid-state battery using a solid electrolyte, or may be a secondary battery using an electrolyte solution.

The perspective view which shows the schematic structure of the secondary battery 10. The perspective view of the positive electrode 16 obtained by space-filling the columnar positive electrode 26. FIG. 3 is a perspective view of a columnar positive electrode 26 having a columnar negative electrode 12 with a separation membrane 14. The perspective view of the columnar negative electrode 12 with the separation membrane 14 arranged in a row. It is explanatory drawing of the method of obtaining the electric resistance Rc1 of the path Pc1 of the 1st positive electrode current collector layer 31.

Next, the secondary battery 10 disclosed in the present embodiment will be described with reference to the drawings. Here, for convenience of explanation, a lithium ion secondary battery having a lithium ion as a carrier will be described below as an example. FIG. 1 is a perspective view showing a schematic configuration of a secondary battery 10, FIG. 2 is a perspective view of a positive electrode 16 obtained by spatially filling a columnar positive electrode 26, and FIG. 3 is a columnar positive electrode having a columnar negative electrode 12 with a separation film 14. 26 is a perspective view, FIG. 4 is a perspective view of a columnar negative electrode 12 having a separation film 14 arranged in a row, and FIG. 5 is an explanatory diagram of a method for obtaining an electric resistance Rc1 of a path Pc1 of a first positive electrode current collector layer 31. In the present embodiment, the vertical direction, the horizontal direction, and the front-back direction are as shown in FIGS. 1, 2, and 4, but these are merely used for convenience in order to show the relative positional relationship.

The secondary battery 10 includes a columnar negative electrode 12, a separation film 14, a positive electrode 16, a negative electrode current collector 20, and a positive electrode current collector 30.

The columnar negative electrode 12 is a columnar body containing a negative electrode active material. The secondary battery 10 has a plurality of columnar negative electrodes 12. The columnar negative electrode 12 may be a bundle of carbon fibers, which is a negative electrode active material, or a twisted carbon fiber. The columnar negative electrode 12 has a capacity of 1 / n (n is an integer of 2 or more, the same applies hereinafter) of the negative electrode capacity of the entire secondary battery 10, and n of them are connected in parallel to the negative electrode current collector 20. The columnar negative electrode 12 preferably has a cross-sectional diameter perpendicular to the longitudinal direction in the range of 10 μm or more and 200 μm or less. When this diameter is 10 μm or more, the strength of the electrode structure can be ensured and stable charging / discharging can be performed. Further, when this diameter is 200 μm or less, the moving distance of the carrier ions does not become too long, and high output performance can be obtained. Further, if this diameter is in this range, the energy density per unit volume can be further increased. Alternatively, within this range, the moving distance of the carrier ions can be made shorter, and charging / discharging can be performed with a larger current. The length of the carbon fiber in the longitudinal direction can be appropriately determined depending on the intended use of the secondary battery 10, and may be, for example, in the range of 20 mm or more and 200 mm or less. When the length of the carbon fiber is 20 mm or more, the battery capacity can be further increased, and when it is 200 mm or less, the electric resistance of the columnar negative electrode 12 can be further reduced, which is preferable. The upper end surface 12a of the columnar negative electrode 12 is provided so as to be exposed from the insulating layer 18 provided on the upper end surface of the positive electrode 16. That is, the insulating layer 18 is provided so that the upper end surfaces 12a of all the columnar negative electrodes 12 are exposed. The insulating layer 18 is made of, for example, an electrically insulating polymer. The upper end surfaces 12a of the columnar negative electrode 12 are periodically arranged on the insulating layer 18 in a grid pattern, and i pieces (i is an integer of 2 or more) in the left-right direction and j pieces (j is 2 or more) in the front-back direction. Integer) lined up.

The separation membrane 14 is provided so as to surround the outer peripheral surface and the lower end surface of the columnar negative electrode 12. The separation membrane 14 is not provided on the upper end surface 12a of the columnar negative electrode 12. The separation membrane 14 has ionic conductivity of ions (lithium ions in this embodiment) as carriers, and insulates the columnar negative electrode 12 and the positive electrode 16. As the separation membrane 14, a polymer having ionic conductivity and insulating property is suitable. Examples of the separation film 14 include a copolymer of polyvinylidene fluoride (PVdF) and hexafluoropropylene (HFP), methyl polymethacrylate (PMMA), and a copolymer of PMMA and an acrylic polymer. .. For example, in a copolymer of PVdF and HFP, a part of the electrolytic solution swells and gels this membrane to become an ionic conduction membrane. The thickness of the separation membrane 14 is preferably 0.5 μm or more, more preferably 2 μm or more, and may be 5 μm or more, for example, in consideration of ensuring insulating properties. Further, the thickness of the separation membrane 14 is preferably 20 μm or less, more preferably 10 μm or less, in consideration of suppressing a decrease in ion conductivity. Therefore, it is preferable that the thickness of the separation membrane 14 is in the range of 0.5 to 20 μm in order to achieve both ionic conductivity and insulating property. The separation membrane 14 may be formed, for example, by immersing the columnar negative electrode 12 in a solution containing a raw material and coating the surface thereof.

In the present embodiment, the electrolytic solution is a non-aqueous solvent in which a supporting salt containing lithium ions is dissolved (non-aqueous electrolytic solution). Examples of the non-aqueous solvent include carbonates, esters, ethers, nitriles, furans, sulfolanes, dioxolanes and the like, 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, and chloroethylene carbonate, dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), diethyl carbonate, and ethyl. Chain carbonates such as -n-butyl carbonate, methyl-t-butyl carbonate, di-i-propyl carbonate, t-butyl-i-propyl carbonate, cyclic esters such as γ-butyl lactone and γ-valerolactone, Chain esters such as methyl formate, methyl acetate, ethyl acetate, methyl butyrate, ethers such as dimethoxyethane, ethoxymethoxy ethane, diethoxyethane, nitriles such as acetonitrile and benzonitrile, furan such as tetrahydrofuran and methyl tetrahydrofuran, etc. Classes, sulfolanes such as sulfolane and tetramethylsulfolane, and dioxolanes such as 1,3-dioxolane and methyldioxolan. 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, and the like. Examples thereof include LiClO ₄ , LiCl, LiF, LiBr, LiI, and LiAlCl ₄ . Of 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 . It is preferable to use a seed or a combination of two or more kinds of salts from the viewpoint of electrical characteristics. The concentration of this supporting salt in the electrolytic solution is preferably 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.

The positive electrode 16 contains a positive electrode active material and is provided so as to fill the space between adjacent separation films 14. As shown in FIG. 2, for example, the positive electrode 16 may be obtained by spatially filling a plurality of columnar positive electrodes 26 made of regular hexagonal prisms. In the central hole 26a of the columnar positive electrode 26, a columnar negative electrode 12 whose outer peripheral surface and lower end surface are surrounded by a separation film 14 is arranged. The central hole 26a is a bottomed cylindrical hole provided along the central axis of the columnar positive electrode 26 from the upper end surface to the lower end surface of the columnar positive electrode 26. Therefore, the outer peripheral surface and the lower end surface of the columnar negative electrode 12 and the inner wall and the bottom surface of the central hole 26a of the columnar positive electrode 26 are insulated by the separation film 14. FIG. 3 shows a perspective view of a columnar positive electrode 26 having a columnar negative electrode 12 with a separation membrane 14.

The positive electrode 16 contains a positive electrode active material, but when the positive electrode active material does not have conductivity, it may be formed by mixing a conductive material having conductivity. The positive electrode 16 may be formed by mixing, for example, a positive electrode active material, a conductive material, and a binder, if necessary. 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 compounds having lithium and a transition metal. Examples of such a compound include an oxide containing lithium and a transition metal element, a phosphoric acid compound containing lithium and a transition metal element, and the like. Specifically, a lithium manganese composite oxide having a basic composition formula of Li _(1-x) MnO ₂ (0 ≦ x ≦ 1, etc., the same applies hereinafter) or Li _(1-x) Mn ₂ O ₄ or the like, basic composition. Lithium-cobalt composite oxide with formula Li _(1-x) CoO ₂ , etc., lithium nickel composite oxide with basic composition formula Li _(1-x) NiO ₂ , etc., basic composition formula 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 is LiV ₂ O ₃ , etc., lithium vanadium composite oxide, basic composition formula is V ₂ O ₅ , etc. A transition metal oxide or the like can be used. Further, a lithium iron phosphate compound having a basic composition formula of LiFePO ₄ or the like 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 Al and Mg may be contained.

When the positive electrode 16 contains a conductive material, the conductive material is not particularly limited as long as it is an electron conductive material that does not adversely affect the battery performance, and is, for example, natural graphite (scaly graphite, scaly graphite), artificial graphite, or the like. Use one or a mixture of graphite, acetylene black, carbon black, ketjen black, carbon whisker, needle coke, carbon fiber, metal (copper, nickel, aluminum, silver, gold, etc.). Can be done. When the positive electrode 16 contains a binder, the binder is not particularly limited as long as it serves to hold the active material particles and the conductive material particles together to maintain a predetermined shape, and is not particularly limited, for example, polytetrafluoro. Fluororesin such as ethylene (PTFE), polyvinylidene fluoride (PVdF), fluororubber, thermoplastic resin such as polypropylene, polyethylene, ethylenepropylene diene monomer (EPDM) rubber, sulfonated EPDM rubber, natural butyl rubber (NBR), etc. Can be used alone or as a mixture of two or more. Further, an aqueous dispersion of cellulose-based binder or styrene-butadiene rubber (SBR), which is an aqueous binder, can also be used. Since a general positive electrode active material does not have conductivity, the positive electrode 16 is usually manufactured by mixing a conductive material. However, even if the conductive material is mixed, its conductivity is lower than that of the columnar negative electrode 12 in which carbon fibers are bundled. Therefore, a plurality of positive electrode conductive patterns 17 are arranged inside the positive electrode 16 in a direction in which they intersect (for example, orthogonally) without contacting the columnar negative electrode 12.

The positive electrode conductive pattern 17 is provided intermittently in the vertical direction and the front-back direction, respectively. The positive electrode conductive pattern 17 is a band-shaped pattern, and a plurality of columnar negative electrodes 12 arranged in the left-right direction in FIG. 1 are regarded as one group, and k rows (k is 2) intermittently in the vertical direction on the front side of each group. The above integers) are arranged. As shown in FIG. 1, the end faces 17a of the positive electrode conductive pattern 17 are periodically arranged on the left side surface of the positive electrode 16 in a grid pattern, and m pieces (m is an integer of 2 or more) in the front-rear direction and the up-down direction. K are provided in. The positive electrode conductive pattern 17 is formed of a material having better conductivity than the positive electrode 16, and examples of such a material include materials exemplified as a conductive material. When the positive electrode 16 shown in FIG. 2 is manufactured, for example, as shown in FIG. 4, a plurality of columnar positive electrodes 26 (columnar negative electrodes 12 with a separation film 14) arranged in a row in the left-right direction are inserted into the center hole 26a. The positive electrode conductive pattern 17 extending in the left-right direction was intermittently formed in the vertical direction on the front side of the group by compressing the positive electrode conductive pattern 17 from the left and right. A large number of groups may be arranged in the front-rear direction and compressed from the front and back to form the positive electrode 16.

The negative electrode current collector 20 is a member having conductivity, and is arranged above the secondary battery 10 as shown in FIG. The negative electrode current collector 20 is provided so as to cover the upper end surface 12a of all the columnar negative electrodes 12 exposed from the insulating layer 18 and the surface of the insulating layer 18. That is, the upper end surfaces 12a of the n columnar negative electrodes 12 are connected in parallel to the negative electrode current collector 20. Examples of the material of the negative electrode current collector 20 include carbon paper, aluminum, copper, titanium, stainless steel, nickel, iron, platinum, calcined carbon, conductive polymer, conductive glass, and the like, as well as adhesiveness and conductivity. Further, for the purpose of improving the oxidation resistance (reducing property), those having the surface of aluminum, copper or the like treated with carbon, nickel, titanium, silver, platinum, gold or the like can also be used. The shape of the negative electrode current collector 20 is a plate shape in this embodiment.

As shown in FIG. 1, the positive electrode current collector 30 includes a first positive electrode current collector layer 31, a second positive electrode current collector layer 32, and a third positive electrode current collector layer 33, and is a secondary battery. It is arranged on one side of 10. The positive electrode current collector 30 and the negative electrode current collector 20 are electrically insulated from each other.

The first positive electrode current collector layer 31 is, for example, vapor-deposited, sputtered, or printed so as to cover the entire surface of the exposed surface (left side surface in FIG. 1) where one end surface 17a of the positive electrode conductive pattern 17 of the positive electrode 16 is exposed. It is formed of. Therefore, the end faces 17a of the plurality of positive electrode conductive patterns 17 are connected in parallel to the first positive electrode current collector layer 31. Examples of the material of the first positive electrode current collector layer 31 include carbon paper, aluminum, copper, titanium, stainless steel, nickel, iron, platinum, calcined carbon, conductive polymer, conductive glass, and the like, as well as adhesiveness. For the purpose of improving conductivity and oxidation resistance (reducing property), those having a surface of aluminum, copper or the like treated with carbon, nickel, titanium, silver, platinum, gold or the like can also be used. The shape of the first positive electrode current collector layer 31 is a plate shape in this embodiment. When the first positive electrode current collector layer 31 is formed on the positive electrode 16 of FIG. 2, the first positive electrode current collector layer 31 is formed on the left side surface of the positive electrode 16 of FIG. 2 bent in a zigzag manner. The positive electrode current collector layer 31 also has a zigzag bent surface.

The second positive electrode current collector layer 32 is a linear or plate-shaped member intermittently provided on the first positive electrode current collector layer 31. As shown in FIG. 1, the second positive electrode current collector layer 32 is a second positive electrode current collector layer that is parallel to and adjacent to the end faces 17a of a plurality of positive electrode conductive patterns 17 arranged on the same straight line in the vertical direction. It is preferable that the 32s are provided so that the distance between them is constant. In FIG. 1, the second positive electrode current collector layer 32 is provided so as to overlap the end faces 17a of a plurality of positive electrode conductive patterns 17 arranged on the same straight line, and the pitch in the front-rear direction of the second positive electrode current collector layer 32. Is twice the pitch in the front-rear direction of the end face 17a of the positive electrode conductive pattern 17. Therefore, in the end faces 17a of the plurality of positive electrode conductive patterns 17 arranged on the same straight line in the vertical direction, those overlapping with the second positive electrode current collecting layer 32 and those not overlapping exist alternately in the front-rear direction. As the material of the second positive electrode current collector layer 32, any of the materials exemplified in the first positive electrode current collector layer 31 can be appropriately used, and the same material as the first positive electrode current collector layer 31 may or may not be used. It may be a material. When the second positive electrode current collector layer 32 is formed on the positive electrode 16 in FIG. 2, it is linear along a side extending in the vertical direction protruding to the left from the zigzag bent left side surface of the positive electrode 16 in FIG. The second positive electrode current collector layer 32 is formed on the surface.

The third positive electrode current collector layer 33 is a linear or plate-shaped member provided so as to bridge the second positive electrode current collector layer 32 without coming into contact with the first positive electrode current collector layer 31. The number of the third positive electrode current collector layer 33 is smaller than that of the second positive electrode current collector layer 32, and is one in the present embodiment. As the material of the third positive electrode current collector layer 33, any of the materials exemplified in the first positive electrode current collector layer 31 can be appropriately used, and the same as the first positive electrode current collector layer 31 and the second positive electrode current collector layer 32. It may be a material or a different material.

The electric resistance of the path through which the current flows through the first positive electrode current collector layer 31 is defined as the electric resistance Rc1 [Ω]. In the present embodiment, the electric resistance Rc1 is the shortest from the end face 17a of the positive electrode conductive pattern 17 that does not overlap with the second positive electrode current collector layer 32 to the second positive electrode current collector layer 32 via the first positive electrode current collector layer 31. The electrical resistance of the path. Specifically, as shown in FIG. 5, the electric resistance Rc1 is the first positive electrode current collector layer 31 from the center line of the end surface 17a of the positive electrode conductive pattern 17 in which the second positive electrode current collector layer 32 is not provided directly above. It is taken as the electric resistance of the path Pc1 (the shaded rectangular portion of FIG. 5) leading to the center line 32c of the second positive electrode current collector layer 32 via the above. This path Pc1 is a rectangular parallelepiped having a length Lc1 [m], a width wc1 [m], and a thickness tc1 [m] in the first positive electrode current collector layer 31. Assuming that the volume resistivity of the first positive electrode current collector layer 31 is ρc1 [Ωm], the electric resistance Rc1 of the first positive electrode current collector layer 31 is expressed by the following equation. In the formula, Sc1 is the cross-sectional area of the path Pc1 (= wc1 × tc1).
Rc1 = ρc1 × Lc1 / Sc1

The electric resistance of the path through which the current flows through the second positive electrode current collector layer 32 is defined as the electric resistance Rc2 [Ω]. In the present embodiment, the electric resistance Rc2 is the electric resistance of the path from the end of the second positive electrode current collector layer 32 to the third positive electrode current collector layer 33 via the second positive electrode current collector layer 32. Specifically, as shown in FIG. 1, the electric resistance Rc2 is the third positive electrode current collector layer 33 from the end portion (right end) of the second positive electrode current collector layer 32 via the second positive electrode current collector layer 32. Let it be the electrical resistance of the path leading to the center line 33c. Assuming that the volume resistivity of the second positive electrode current collector layer 32 is ρc2 [Ωm], the electric resistance Rc2 is expressed by the following equation. The length Lc2 [m] and the cross-sectional area Sc2 [m ² ] are shown in FIG.
Rc2 = ρc2 × Lc2 / Sc2 (However, Sc2 is the cross-sectional area of the second positive electrode current collector layer 32).

The electric resistance of the path through which the current flows through the third positive electrode current collector layer 33 is defined as the electric resistance Rc3 [Ω]. In the present embodiment, the electric resistance Rc3 is an electric resistance extending from one end to the other end in the longitudinal direction of the third positive electrode current collector layer 33. Assuming that the volume resistivity of the third positive electrode current collector layer 33 is ρc3 [Ωm], the electric resistance Rc3 is expressed by the following equation. The length Lc3 [m] and the cross-sectional area Sc3 [m ² ] are shown in FIG.
Rc3 = ρc3 × Lc3 / Sc3 (However, Sc3 is the cross-sectional area of the third positive electrode current collector layer 33).

In the present embodiment, the electric resistances Rc1, Rc2, and Rc3 satisfy the relationship of Rc1> Rc2> Rc3. Further, the ratio of the electric resistance Rc2 to the electric resistance Rc1 is preferably 0.1 or less, and the ratio of the electric resistance Rc3 to the electric resistance Rc2 is preferably 0.1 or less.

According to the secondary battery 10 of the present embodiment described in detail above, by adopting the positive electrode current collector 30 having a three-layer structure, the positive electrode 16 can be efficiently collected, so that the weight energy density and volume can be increased. The energy density can be made sufficiently high. When the positive electrode current collecting structure is only the first positive electrode collecting layer 31, the current from all the positive electrode conductive patterns 17 is practical because the electric resistance of the path through which the current flows through the first positive electrode collecting layer 31 is high. It is difficult to flow in a wide voltage drop range. However, here, the positive electrode current collecting structure is provided with the first positive electrode collecting layer 31, the low resistance second positive electrode collecting layer 32 intermittently provided on the first positive electrode collecting layer 31, and the second positive electrode collecting layer 32. Since it is composed of a third positive electrode current collector layer 33 having a lower resistance provided on the positive electrode current collector layer 32, the currents from all the positive electrode conductive patterns 17 are collected from the first positive electrode current collector layer 31 and the second positive electrode current collector. Current can be collected with relatively low electrical resistance via the layer 32 and the third positive electrode current collecting layer 33 in this order. As a result, the currents from all the positive electrode conductive patterns 17 can flow in a practical voltage drop range. Therefore, in the secondary battery 10 in which the columnar negative electrode 12 surrounded by the separation film 14 is arranged in the positive electrode 16, the energy density can be sufficiently increased.

Further, since the ratio of the electric resistance Rc2 to the electric resistance Rc1 is 0.1 or less and the ratio of the electric resistance Rc3 to the electric resistance Rc2 is 0.1 or less, the energy density can be further increased.

Further, the end surface 17a of the positive electrode conductive pattern 17 is periodically arranged on the exposed surface (the left side surface of the positive electrode 16), and the second positive electrode current collector layer 32 is parallel to the plurality of end surfaces 17a arranged on the same straight line. It is provided so that the distance between the adjacent second positive electrode current collector layers 32 is constant. As a result, the second positive electrode current collector layer 32 has a periodic structure and is easy to manufacture.

Furthermore, since the third positive electrode current collector layer 33 is a single conductive wire provided so as to bridge the second positive electrode current collector layer 32, when a plurality of third positive electrode current collector layers 33 are present. The configuration is simplified in comparison.

The positive electrode 16 is obtained by spatially filling a plurality of columnar positive electrodes 26 made of regular hexagonal columns, and the columnar negative electrode 12 surrounded by the separation film 14 is arranged in the central hole 26a of the columnar positive electrode 26. There is. Therefore, the positive electrode 16 can be manufactured relatively easily.

It should be noted that the present disclosure is not limited to the above-described embodiment, and it goes without saying that the present disclosure can be carried out in various embodiments as long as it belongs to the technical scope of the present disclosure.

For example, in the above-described embodiment, the carrier of the secondary battery 10 is lithium ion, but the carrier is not particularly limited to this, and alkali metal ions such as sodium ion and potassium ion, and group 2 element ions such as calcium ion and magnesium ion. May be. Further, the positive electrode active material may contain carrier ions. Further, although the electrolytic solution is a non-aqueous electrolytic solution, it may be an aqueous electrolytic solution.

In the above-described embodiment, the example in which the carbon fiber has a cylindrical shape has been described, but the carbon fiber is not particularly limited to this, and may have a shape such as a quadrangular column or a hexagonal column.

In the above-described embodiment, the shape of the first positive electrode current collector layer 31 is plate-shaped, but the shape is not particularly limited to plate-shaped, and for example, foil-shaped, film-shaped, sheet-shaped, net-shaped, punching sheet, and the like. It may be a glass body, a porous body, a foam body, a fiber group forming body, or the like. The same applies to the shapes of the second and third positive electrode current collector layers 32 and 33. Further, the first to third positive electrode current collector layers 31 to 33 may all have the same shape, two may have the same shape, and the remaining one may have a different shape, or all three may have different shapes. It may be.

In the above-described embodiment, the secondary battery 10 using an electrolytic solution is exemplified, but an all-solid-state battery that does not use an electrolytic solution may be used.

In the above-described embodiment, the second positive electrode current collector layer 32 is provided so as to overlap the end faces 17a of the positive electrode conductive patterns 17 arranged in a straight line, but the present invention is not particularly limited thereto, and the second positive electrode current collector layer 32 is arranged in a straight line. However, it may be provided so as not to overlap the end surface 17a of the positive electrode conductive pattern 17, or a mixture of overlapping and non-overlapping may be used. Further, the pitch in the front-rear direction of the second positive electrode current collector layer 32 is twice the pitch in the front-rear direction of the end surface 17a of the positive electrode conductive pattern 17, but is not particularly limited to twice, for example, three times. Or 4 times.

In the above-described embodiment, the positive electrode current collector 30 is provided on the left side surface of the secondary battery 10, but the present invention is not particularly limited thereto, and may be provided on the right side surface, or may be provided on the front surface or the rear surface. Alternatively, it may be provided on the lower surface.

In the above-described embodiment, the columnar positive electrode 26 having a regular hexagonal column is used, but the columnar positive electrode 26 may be pressed to form a regular hexagonal column.

In the above-described embodiment, the columnar negative electrode 12 is exemplified by a bundled or twisted carbon fiber which is a negative electrode active material, but the present invention is not particularly limited to this, and a carrier (for example, lithium ion) is occluded. Any material may be contained as long as it contains a material that can be released. Further, it may contain a conductive material and a binder material as needed.

10 Secondary battery, 12 Columnar negative electrode, 12a Top surface, 14 Separation film, 16 Positive electrode, 17 Positive electrode conductive pattern, 17a End surface, 18 Insulation layer, 20 Negative electrode current collector, 26 Columnar positive electrode, 26a Central hole, 30 Positive electrode collection Electric body, 31 1st positive electrode current collector layer, 32 2nd positive electrode current collector layer, 32c center line of 2nd positive electrode current collector layer, 33 3rd positive electrode current collector layer, 33c center line of 3rd positive electrode current collector layer.

Claims (5)

Multiple columnar negative electrodes containing negative electrode active material,
A separation membrane provided so as to surround each columnar negative electrode,
A positive electrode containing a positive electrode active material and provided so as to fill the space between adjacent separation membranes,
A plurality of positive electrode conductive patterns arranged in a direction intersecting the columnar negative electrode inside the positive electrode, and
A first positive electrode current collector layer provided so as to cover an exposed surface on which one end surface of the positive electrode conductive pattern of the positive electrode is exposed.
A plurality of second positive electrode current collector layers intermittently provided on the first positive electrode current collector layer, and
A third positive electrode current collector layer, which is provided so as to bridge the second positive electrode current collector layer without contacting the first positive electrode current collector layer, and has a smaller number than the second positive electrode current collector layer.
Equipped with
The electric resistance Rc1 of the current path of the first positive electrode current collector layer, the electric resistance Rc2 of the current path of the second positive electrode current collector layer, and the electric resistance Rc3 of the current path of the third positive electrode current collector layer are Rc1>. Satisfy the relationship of Rc2> Rc3,
Secondary battery. The electric resistance Rc1 is the shortest path from the end face of the positive electrode conductive pattern that does not overlap with the second positive electrode current collector layer to the second positive electrode current collector layer via the first positive electrode current collector layer. It is an electric resistance, and the electric resistance Rc2 is an electric resistance of a path from an end portion of the second positive electrode current collecting layer to the third positive electrode current collecting layer via the second positive electrode collecting layer. The electric resistance R c 3 is the electric resistance of the path from one end to the other end of the third positive electrode current collector layer.
The secondary battery according to claim 1. The ratio of the electric resistance Rc2 to the electric resistance Rc1 is 0.1 or less, and the ratio of the electric resistance Rc3 to the electric resistance Rc2 is 0.1 or less.
The secondary battery according to claim 1 or 2. The end face of the positive electrode conductive pattern is periodically arranged on the exposed surface.
The second positive electrode current collector layer is parallel to the end faces of the plurality of positive electrode conductive patterns arranged on the same straight line, and the distance between adjacent second positive electrode current collector layers is constant. It is provided,
The secondary battery according to any one of claims 1 to 3. The third positive electrode current collector layer is a single conductive wire provided so as to bridge the second positive electrode current collector layer.
The secondary battery according to any one of claims 1 to 4.

Images