JP6981452B2 - Secondary battery - Google Patents

Description

The invention disclosed herein relates to a secondary battery.

Conventionally, as a secondary battery, one in which the material of the current collector part is devised in order to improve the current collector efficiency (Patent Documents 1 to 3), and one related to a current collector structure for fixing a plurality of current collector plates and conductors (Patent Documents 1 to 3). Patent documents 4 to 6) and the like are known. Further, as a secondary battery having a high energy density, a plurality of columnar negative electrodes, a separation membrane 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 also known (Patent Document 7). 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. 2019-32966 Japanese Unexamined Patent Publication No. 2019-33066 Japanese Unexamined Patent Publication No. 2018-116910 Japanese Patent No. 6159719 Japanese Unexamined Patent Publication No. 2014-154272 Japanese Unexamined Patent Publication No. 2015-10313 Japanese Unexamined Patent Publication No. 2018-152229

However, in the secondary battery of Patent Document 7, since the negative electrode current collecting structure is such that one end face of the columnar negative electrode is connected to the metal current 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 negative electrode current collecting structure in the secondary battery in which the columnar negative electrode surrounded by the separation membrane 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,
An insulating layer provided so that one end face of all the columnar negative electrodes is exposed,
A first negative electrode current collector layer provided so as to cover one end face of all the columnar negative electrodes exposed from the insulating layer,
A plurality of second negative electrode current collector layers intermittently provided on the first negative electrode current collector layer, and
A third negative electrode current collector layer, which is provided so as to bridge the second negative electrode current collector layer without contacting the first negative electrode current collector layer and has a smaller number than the second negative electrode current collector layer.
Equipped with
The electric resistance Ra1 of the current path of the first negative electrode current collector layer, the electric resistance Ra2 of the current path of the second negative electrode current collector layer, and the electric resistance Ra3 of the current path of the third negative electrode current collector layer are Ra1>. Satisfying the relationship Ra2> Ra3,
It is a thing.

According to this secondary battery, since the columnar negative electrode can be efficiently collected, the weight energy density and the volume energy density can be sufficiently increased. When the negative electrode current collecting structure is only the first negative electrode current collecting layer, the electric resistance of the path through which the current flows through the first negative electrode current collecting layer is high, so that the current from all the columnar negative electrodes can be measured within a practical voltage drop range. It's difficult to shed. However, here, the negative electrode current collecting structure is provided with a first negative electrode current collecting layer, a low resistance second negative electrode current collecting layer intermittently provided on the first negative electrode current collecting layer, and a second negative electrode collecting layer. Since it is composed of a third negative electrode current collector layer having a lower resistance provided on the electric layer, the current from all the columnar negative electrodes is collected from the first negative electrode current collector layer, the second negative electrode current collector layer, and the third negative electrode current collector layer. It is possible to collect current with a relatively low electrical resistance via the order of. As a result, the current from all the columnar negative electrodes 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 in the present specification, the electric resistance Ra1 is the second negative electrode current collector layer from the end face of the columnar negative electrode that does not overlap with the second negative electrode current collector layer via the first negative electrode current collector layer. It is the electric resistance of the shortest path to the negative electrode current collecting layer (for example, the center line of the second negative electrode collecting layer), and the electric resistance Ra2 is the second negative electrode collecting layer from the end of the second negative electrode collecting layer. It is the electric resistance of the path to the third negative electrode current collector layer (for example, the center line of the third negative electrode current collector layer) via the above, and the electric resistance Ra3 is from one end to the other end of the third negative electrode current collector layer. It may be the electrical resistance of the path leading to.

In the secondary battery disclosed in the present specification, even if the ratio of the electric resistance Ra2 to the electric resistance Ra1 is 0.1 or less and the ratio of the electric resistance Ra3 to the electric resistance Ra2 is 0.1 or less. good. In this way, the energy density can be further increased.

In the secondary battery disclosed herein, the end faces of the columnar negative electrodes are periodically arranged, and the second negative electrode current collector layer is parallel to the end faces of a plurality of columnar negative electrodes arranged on the same straight line. It may be provided so that the distance between the second negative electrode current collector layers adjacent to each other is constant. By doing so, the second negative electrode current collector layer has a periodic structure and is easy to form.

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

In the secondary battery disclosed in the present specification, the positive electrode is obtained by spatially 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 membrane. May be arranged in the central hole of the columnar positive electrode. In this way, the positive electrode can be manufactured relatively easily.

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. It is explanatory drawing of the method of obtaining the electric resistance Ra1 of the path Pa1 of the 1st negative electrode current collector layer 21.

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 membrane 14. 26 is a perspective view, and FIG. 4 is an explanatory diagram of a method for obtaining the electric resistance Ra1 of the path Pa1 of the first negative electrode current collector layer 21. In the present embodiment, the vertical direction, the horizontal direction, and the front-back direction are as shown in FIGS. 1 and 2, 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 membrane 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 the first negative electrode current collector layer 21 of the negative electrode current collector 20. Is connected in parallel to. 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, i in the left-right direction (i is an integer of 2 or more), and j in the front-back direction (j is 2 or more). 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 ionic 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. Examples thereof include sulfolanes such as sulfolane and tetramethylsulfolane, and dioxolanes such as 1,3-dioxolane and methyldioxolane. 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, ethylene propylene diene monomer (EPDM) rubber, sulfonated EPDM rubber, natural butyl rubber (NBR), etc. Can be used alone or as a mixture of two or more. Further, an aqueous dispersion of cellulose-based binder or styrene-butadiene rubber (SBR), which is an aqueous binder, can also be used.

As shown in FIG. 1, the negative electrode current collector 20 includes a first negative electrode current collector layer 21, a second negative electrode current collector layer 22, and a third negative electrode current collector layer 23, and is a secondary battery. It is located on top of 10.

The first negative electrode current collector layer 21 is formed by, for example, thin-film deposition, sputtering, printing, or the like so as to cover the upper end surfaces 12a of all the columnar negative electrodes 12 exposed from the insulating layer 18 and the surface of the insulating layer 18. Therefore, the upper end surfaces 12a of the n columnar negative electrodes 12 are connected in parallel to the first negative electrode current collector layer 21. Examples of the material of the first negative electrode current collector layer 21 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), aluminum, copper, or the like whose surface is treated with carbon, nickel, titanium, silver, platinum, gold, or the like can also be used. The shape of the first negative electrode current collector layer 21 is a plate shape in this embodiment.

The second negative electrode current collector layer 22 is a linear or plate-shaped member intermittently provided on the first negative electrode current collector layer 21. As shown in FIG. 1, the second negative electrode current collector layer 22 is parallel to and adjacent to the upper end surfaces 12a of a plurality of columnar negative electrode 12s arranged on the same straight line in the left-right direction. It is preferable that they are provided so that the distance between them is constant. In FIG. 1, the second negative electrode current collector layer 22 is provided so as to overlap the upper end surfaces 12a of a plurality of columnar negative electrode 12s arranged on the same straight line, and the pitch of the second negative electrode current collector layer 22 in the front-rear direction is , The pitch of the upper end surface 12a of the columnar negative electrode 12 in the front-rear direction is twice. Therefore, in the upper end surfaces 12a of the plurality of columnar negative electrodes 12 arranged on the same straight line in the left-right direction, those that overlap with the second negative electrode current collector layer 22 and those that do not overlap exist alternately in the front-rear direction. As the material of the second negative electrode current collector layer 22, any of the materials exemplified in the first negative electrode current collector layer 21 can be appropriately used, and the same material as the first negative electrode current collector layer 21 may be used. It may be a material.

The third negative electrode current collector layer 23 is a linear or plate-shaped member provided so as to bridge the second negative electrode current collector layer 22 without coming into contact with the first negative electrode current collector layer 21. The number of the third negative electrode current collector layer 23 is smaller than that of the second negative electrode current collector layer 22, and the number is one in the present embodiment. As the material of the third negative electrode current collector layer 23, any of the materials exemplified in the first negative electrode current collector layer 21 can be appropriately used, and the same as the first negative electrode current collector layer 21 and the second negative electrode current collector layer 22. It may be a material or a different material.

The electric resistance of the path through which the current flows through the first negative electrode current collector layer 21 is defined as the electric resistance Ra1 [Ω]. In the present embodiment, the electric resistance Ra1 is the shortest path from the upper end surface 12a of the columnar negative electrode 12 that does not overlap with the second negative electrode current collector layer 22 to the second negative electrode current collector layer 22 via the first negative electrode current collector layer 21. The electrical resistance of. Specifically, as shown in FIG. 4, the electric resistance Ra1 is a first negative electrode current collector layer 21 from the center line of the upper end surface 12a of the columnar negative electrode 12 in which the second negative electrode current collector layer 22 is not provided directly above. It is the electrical resistance of the path Pa1 (the shaded rectangular portion of FIG. 4) leading to the center line 22c of the second negative electrode current collector layer 22 via the electric resistance. This path Pa1 is a rectangular parallelepiped having a length La1 [m], a width wa1 [m], and a thickness ta1 [m] in the first negative electrode current collector layer 21. Assuming that the volume resistivity of the first negative electrode current collector layer 21 is ρa1 [Ωm], the electrical resistance Ra1 of the first negative electrode current collector layer 21 is expressed by the following equation. In the formula, Sa1 is the cross-sectional area (= wa1 × ta1) of the path Pa1.
Ra1 = ρa1 x La1 / Sa1

The electric resistance of the path through which the current flows through the second negative electrode current collector layer 22 is defined as the electric resistance Ra2 [Ω]. In the present embodiment, the electric resistance Ra2 is the electric resistance of the path from the end of the second negative electrode current collector layer 22 to the third negative electrode current collector layer 23 via the second negative electrode current collector layer 22. Specifically, as shown in FIG. 1, the electric resistance Ra2 is the third negative electrode current collector layer 23 from the end portion (right end) of the second negative electrode current collector layer 22 via the second negative electrode current collector layer 22. Let it be the electrical resistance of the path leading to the center line 23c. Assuming that the volume resistivity of the second negative electrode current collector layer 22 is ρa2 [Ωm], the electric resistance Ra2 is expressed by the following equation. The length La2 [m] and the cross-sectional area Sa2 [m ² ] are shown in FIG.
Ra2 = ρa2 × La2 / Sa2 (Sa2 is the cross-sectional area of the second negative electrode current collector layer 22).

The electric resistance of the path through which the current flows through the third negative electrode current collector layer 23 is defined as the electric resistance Ra3 [Ω]. In the present embodiment, the electric resistance Ra3 is an electric resistance extending from one end to the other end in the longitudinal direction of the third negative electrode current collector layer 23. Assuming that the volume resistivity of the third negative electrode current collector layer 23 is ρa3 [Ωm], the electric resistance Ra3 is expressed by the following equation. The length La3 [m] and the cross-sectional area Sa3 [m ² ] are shown in FIG.
Ra3 = ρa3 × La3 / Sa3 (S3 is the cross-sectional area of the third negative electrode current collector layer 23).

In the present embodiment, the electric resistances Ra1, Ra2, and Ra3 satisfy the relationship of Ra1> Ra2> Ra3. Further, the ratio of the electric resistance Ra2 to the electric resistance Ra1 is preferably 0.1 or less, and the ratio of the electric resistance Ra3 to the electric resistance Ra2 is preferably 0.1 or less.

The positive electrode current collector 30 is a conductive member and is electrically connected to the lower surface of the positive electrode 16. The lower end surfaces of n columnar positive electrodes 26 (see FIG. 2) are connected in parallel to the positive electrode current collector 30. Examples of the material of the positive electrode current collector 30 include those exemplified as the material of the first negative electrode current collector layer 21 of the negative electrode current collector 20. The lower surface of the positive electrode 16 is directly connected to the positive electrode current collector 30.

According to the secondary battery 10 of the present embodiment described in detail above, the columnar negative electrode 12 can be efficiently collected by adopting the negative electrode current collector 20 having a three-layer structure, so that the weight energy density and the weight energy density can be increased. The volumetric energy density can be made sufficiently high. When the negative electrode current collecting structure is only the first negative electrode current collecting layer 21, the current from all the columnar negative electrodes 12 is a practical voltage because the electric resistance of the path through which the current flows through the first negative electrode current collecting layer 21 is high. It is difficult to flow in the lowered range. However, here, the negative electrode current collecting structure is further divided into the first negative electrode current collecting layer 21, the low resistance second negative electrode current collecting layer 22 intermittently provided on the first negative electrode current collecting layer 21, and the second negative electrode current collecting layer 22. 2 Since it is composed of a third negative electrode current collector layer 23 having a lower resistance provided on the negative electrode current collector layer 22, the current from all the columnar negative electrode 12 is transferred to the first negative electrode current collector layer 21 and the second negative electrode current collector layer. The current can be collected with a relatively low electric resistance via the 22 and the third negative electrode current collecting layer 23 in this order. As a result, the current from all the columnar negative electrodes 12 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 membrane 14 is arranged in the positive electrode 16, the energy density can be sufficiently increased.

Further, since the ratio of the electric resistance Ra2 to the electric resistance Ra1 is 0.1 or less and the ratio of the electric resistance Ra3 to the electric resistance Ra2 is 0.1 or less, the energy density can be further increased.

Further, the second negative electrode current collector layer 22 is parallel to the upper end surfaces 12a of the plurality of columnar negative electrode 12s arranged on the same straight line, and the distance between the adjacent second negative electrode current collector layers 22 is constant. It is provided in. As a result, the second negative electrode current collector layer 22 has a periodic structure and is easy to form.

Furthermore, since the third negative electrode current collector layer 23 is a single conductive wire provided so as to bridge the second negative electrode current collector layer 22, when a plurality of third negative electrode current collector layers 23 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 membrane 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 negative electrode current collector layer 21 is foil-shaped, but the shape is not particularly limited to foil-like, and for example, plate-like, film-like, sheet-like, net-like, 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 negative electrode current collector layers 22 and 23. Further, the first to third negative electrode current collector layers 21 to 23 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 negative electrode current collector layer 22 is provided so as to overlap the upper end surface 12a of the columnar negative electrodes 12 arranged in a straight line, but the present invention is not particularly limited to this, and the second negative electrode current collector layer 22 is arranged in a straight line. It may be provided so as not to overlap the upper end surface 12a of the columnar negative electrode 12, or an overlapping one and a non-overlapping one may be mixed. Further, the pitch in the front-rear direction of the second negative electrode current collector layer 22 is twice the pitch in the front-rear direction of the upper end surface 12a of the columnar negative electrode 12, but is not particularly limited to twice, for example, three times. It may be quadrupled. Further, although the second negative electrode current collector layers 22 are provided at equal intervals, they do not have to be at equal intervals, and may be provided intermittently.

In the above-described embodiment, the columnar positive electrode 26 is a regular hexagonal prism, but any regular polygonal prism that can fill the space may be used, and for example, a regular triangular prism or a regular tetrahedron may be used.

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 or a binder material as needed.

10 Secondary battery, 12 Columnar negative electrode, 12a upper end surface, 14 Separation film, 16 Positive electrode, 18 Insulation layer, 20 Negative electrode current collector, 21 First negative electrode current collector layer, 22 Second negative electrode current collector layer, 22c Second negative electrode Center line of collector layer, 23rd negative electrode current collector layer, 23c center line of third negative electrode current collector layer, 26 columnar positive electrode, 26a center hole, 30 positive electrode current collector.

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,
An insulating layer provided so that one end face of all the columnar negative electrodes is exposed,
A first negative electrode current collector layer provided so as to cover one end face of all the columnar negative electrodes exposed from the insulating layer,
A plurality of second negative electrode current collector layers intermittently provided on the first negative electrode current collector layer, and
A third negative electrode current collector layer, which is provided so as to bridge the second negative electrode current collector layer without contacting the first negative electrode current collector layer and has a smaller number than the second negative electrode current collector layer.
Equipped with
The electric resistance Ra1 of the current path of the first negative electrode current collector layer, the electric resistance Ra2 of the current path of the second negative electrode current collector layer, and the electric resistance Ra3 of the current path of the third negative electrode current collector layer are Ra1>. Satisfying the relationship Ra2> Ra3,
Secondary battery. The electrical resistance Ra1 is the electrical resistance of the shortest path from the end face of the columnar negative electrode that does not overlap with the second negative electrode current collector layer to the second negative electrode current collector layer via the first negative electrode current collector layer. The electric resistance Ra2 is the electric resistance of the path from the end of the second negative electrode current collector layer to the third negative electrode current collector layer via the second negative electrode current collector layer, and is the electric resistance. Ra3 is the electrical resistance of the path from one end to the other end of the third negative electrode current collector layer.
The secondary battery according to claim 1. The ratio of the electric resistance Ra2 to the electric resistance Ra1 is 0.1 or less, and the ratio of the electric resistance Ra3 to the electric resistance Ra2 is 0.1 or less.
The secondary battery according to claim 1 or 2. The end face of the columnar negative electrode is periodically arranged.
The second negative electrode current collector layer is provided so as to overlap in parallel with the end faces of the plurality of columnar negative electrodes arranged on the same straight line and to keep the distance between adjacent second negative electrode current collector layers constant. ing,
The secondary battery according to any one of claims 1 to 3. The third negative electrode current collector layer is a single conductive wire provided so as to bridge the second negative electrode current collector layer.
The secondary battery according to any one of claims 1 to 4.

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