JP2017174647A - Electrode structure and lithium secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the increase in internal resistance further.SOLUTION: An electrode structure 11 comprises: a positive electrode sheet 15 with a positive electrode mixture layer 14; a negative electrode sheet 18 with a negative electrode mixture layer 17; and a separator 21 provided between the positive electrode sheet 15 and the negative electrode sheet 18, and having a positive electrode-side layer 20 and a negative electrode-side layer 19. A lithium secondary battery 10 comprises: the electrode structure 11; and a nonaqueous electrolyte solution 22 filling between the positive electrode sheet 15 and the negative electrode sheet 18. As to the electrode structure 11, the following relation is satisfied: (D-C)/(A-B)>0, where A (mm) is a liquid-absorption height of the positive electrode mixture layer 14, B(mm) is a liquid-absorption height of the negative electrode mixture layer 17, C(mm) is a liquid-absorption height of the positive electrode-side layer 20 of the separator 21, and D(mm) is a liquid-absorption height of the negative electrode-side layer 19 of the separator 21, which were measured after the electrode structure had been left absorbing a test solution for ten minutes according to the Byreck method of JIS L 1907: 2010.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electrode structure and a lithium secondary battery.

  Conventionally, as a lithium secondary battery, the value A obtained by dividing the DBP oil absorption amount of the positive electrode active material particles by the porosity of the positive electrode active material layer and the thickness of the positive electrode active material layer, and the oil absorption of linseed oil of the negative electrode active material particles A battery is proposed in which the ratio A / B of the amount B divided by the porosity of the negative electrode active material layer and the thickness of the negative electrode active material layer is 0.78 ≦ (A / B) ≦ 1.22 (See Patent Document 1). In this battery, the positive electrode active material layer and the negative electrode active material layer have a generally balanced balance of the electrolyte retention characteristics. For this reason, in applications where charging and discharging are repeated at a high rate (high current), even when the electrolyte solution is repeatedly put in and out of the positive electrode and negative electrode of the battery, the increase in resistance of the battery can be kept low.

JP2013-109929A

  However, in the battery of Patent Document 1, the positive electrode active material layer and the negative electrode active material layer adjust the retention property of the electrolyte, thereby suppressing an increase in resistance and enhancing the durability against high-rate charge / discharge. However, it is not yet sufficient, and it has been desired to further improve durability against high-rate charge / discharge.

  This invention is made | formed in view of such a subject, and it aims at providing the electrode structure and lithium secondary battery which can suppress the increase in internal resistance more.

  As a result of diligent research to achieve the above-mentioned object, the present inventors have found that the liquid absorption height measured according to the Bayrec method has a predetermined relationship, and the positive electrode layer of the positive electrode, the negative electrode, and the separator, and A layer on the negative electrode side of the separator was prepared and an electrode structure was produced using these layers. As a result, it was found that an increase in internal resistance could be further suppressed, and the present invention was completed.

That is, the electrode structure of the present invention is
A positive electrode, a negative electrode, and two or more layers of separators interposed between the positive electrode and the negative electrode,
Absorbing height of the positive electrode was measured as A (mm), the absorbing height of the negative electrode was B (mm), and the absorbing liquid of the layer on the positive electrode side of the separator was measured by absorbing the test solution for 10 minutes by the Bayrec method. When the height is C (mm) and the liquid absorption height of the negative electrode layer of the separator is D (mm), (D−C) / (A−B)> 0 is satisfied.

The lithium secondary battery of the present invention is
The electrode structure described above;
A non-aqueous electrolyte that conducts lithium ions interposed between the positive electrode and the negative electrode;
It is equipped with.

  In the electrode structure and lithium secondary battery of the present invention, the increase in internal resistance can be further suppressed. The reason why such an effect can be obtained is assumed as follows. For example, when a separator having a single layer structure is used, the salt solution is particularly charged / discharged at a high rate due to the difference in the flowability of the electrolyte solution between the positive electrode and the negative electrode, the holding power of the electrolyte solution, and the like. Concentration unevenness increases and resistance tends to increase. However, two or more layers of separators are provided, and (DC) / (AB)> 0 is satisfied, that is, a separator having a high liquid absorption height is disposed on the electrode side having a low liquid absorption height, By arranging a separator having a low liquid absorption height on the electrode side having a high liquid absorption height, it is considered that the deviation in salt concentration can be reduced. Thus, it is speculated that an increase in resistance can be further suppressed. Here, the “Bilec method” is a liquid absorption method in accordance with JIS L 1907: 2010.

1 is a schematic diagram illustrating an example of a lithium secondary battery 10. FIG. 3 is a cross-sectional view showing an example of an electrode structure 11. Explanatory drawing which shows the measuring method of liquid absorption height. FIG. 2 is a schematic diagram illustrating an example of a lithium secondary battery 30.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing an example of a lithium secondary battery 10 of the present invention. FIG. 2 is a cross-sectional view illustrating an example of the electrode structure 11. As shown in FIGS. 1 and 2, the lithium secondary battery 10 of this embodiment includes, for example, a positive electrode sheet 15 in which a positive electrode mixture layer 14 is formed on a current collector 13 and a negative electrode mixture on the surface of the current collector 16. A separator 21 having a positive electrode layer 20 and a negative electrode layer 19 provided between the positive electrode sheet 15 and the negative electrode sheet 18; and a positive electrode sheet 15 and a negative electrode sheet 18. And a non-aqueous electrolyte solution 22 that satisfies the condition. In the lithium secondary battery 10, the separator 21 is sandwiched between the positive electrode sheet 15 and the negative electrode sheet 18, and these are wound and inserted into the cylindrical case 23, and the positive electrode terminal 24 and the negative electrode sheet 18 connected to the positive electrode sheet 15. And a negative electrode terminal 26 connected to each other.

  The lithium secondary battery 10 includes a positive electrode sheet 15 including a positive electrode active material and a current collector 13, a negative electrode sheet 18 including a negative electrode active material and a current collector 16, and between the positive electrode sheet 15 and the negative electrode sheet 18. The electrode structure 11 includes a separator 21 having a positive electrode layer 20 and a negative electrode layer 19 interposed therebetween. In this electrode structure 11, the liquid absorption height of the positive electrode mixture layer 14 is A (mm) and the liquid absorption height of the negative electrode mixture layer 17 is B (measured by absorbing the test solution for 10 minutes by the birec method. mm), the liquid absorption height of the layer 20 on the positive electrode side of the separator 21 is C (mm), and the liquid absorption height of the layer 19 on the negative electrode side of the separator 21 is D (mm). / (A−B)> 0 is satisfied.

  Here, the measuring method of liquid absorption height is demonstrated. The measuring method of the liquid absorption height shall be performed in accordance with the birec method of JIS L 1907: 2010. The measuring method of the liquid absorption height is that the test solution is not limited to water, the dimension of the test piece is about 100 cm × 2.5 cm, and the direction in which the test piece is collected corresponds to the axial direction of the battery is the longitudinal direction. This is the same as the JIS L 1907: 2010 birec method except that the direction (only in one direction) is such that a weight is attached to the end of the test piece on the side to be immersed.

  FIG. 3 is an explanatory view showing a method for measuring the liquid absorption height. As shown in FIG. 3, after fixing the test piece 60 on a horizontal bar 60 supported on the liquid level of the container 52 containing the test solution 66 with a pin or the like, the lower end 62 (from the lower end of the test piece 60) 20 mm ± 2 mm) is soaked in the reagent solution 66 and left as it is for 10 minutes. After standing, the height T (hereinafter also referred to as the liquid absorption height) at which the test solution 66 has risen due to capillary action is measured in units of 1 mm on a scale.

  As the test piece 60, the positive electrode sheet 15, the negative electrode sheet 18, the positive electrode side layer 20 of the separator 21, and the negative electrode side layer 19 of the separator 21 (or a sheet made of the same material) are each 100 cm × 2.5 cm. Use a size cut out. The longitudinal direction of the test piece 60 is made to coincide with the winding axis direction (hereinafter referred to as the axial direction) when each member is wound and incorporated in the lithium secondary battery 10. In FIG. 3, a weight 64 is attached to the end of the test piece 60 on the lower end portion 62 side to suppress the lower end portion 62 from floating. In addition, when the positive electrode mixture layer 14 and the negative electrode mixture layer 17 can maintain the shape independently, the positive electrode mixture layer 14 and the negative electrode mixture layer 17 (or the same as these) can be used instead of the positive electrode sheet 15 and the negative electrode sheet 18. The test piece 60 may be cut out from a sheet of material and used.

  The type of the test solution 66 is not particularly limited. This is because the values of A, B, C, and D may vary depending on the type of the test solution 66, but it is considered that there is no significant difference in the ratio of (DC) / (AB). The test solution 66 is preferably one having low volatility from the viewpoint of ease of evaluation. The test solution 66 may be a solvent which will be exemplified later as the nonaqueous electrolytic solution 22 of the lithium secondary battery 10, for example, propylene carbonate. Propylene carbonate has low volatility and is suitable for evaluation. The reagent solution 66 may be water. The type of the test solution 66 may be the same as or different from the solvent used for the non-aqueous electrolyte 22 of the lithium secondary battery 10. The temperature of the test solution is 20 ° C. ± 2 ° C.

  The value of (D−C) / (A−B) may be larger than 0, but is preferably 1 or more, and more preferably 2 or more. With such a thing, it is thought that the bias | inclination of salt concentration can be reduced more and resistance increase can be suppressed more. Moreover, the upper limit of the value of (D−C) / (A−B) is not particularly limited, but may be 100 or less, 75 or less, 50 or less, or the like.

  The value of | A−B | may be larger than 0, but may be 1 or more, 3 or more, or 5 or more. When the value of | A−B | is large, the bias of the salt concentration tends to increase when a single-layer separator or the like is used. In addition, what is necessary is just to set the value of A and B suitably so that a charging / discharging characteristic may become favorable, A may be larger than B and B may be larger than A.

  As shown in FIG. 2, a positive electrode mixture layer 14 containing a positive electrode active material is formed on both surfaces of the positive electrode sheet 15. The positive electrode mixture layer 14 may be formed on one side of the positive electrode sheet 15 depending on the structure to be employed. The thickness a per side of the positive electrode mixture layer 14 may be, for example, 10 μm or more and 500 μm or less, or 20 μm or more and 200 μm or less.

  The positive electrode sheet 15 is prepared by, for example, mixing a positive electrode active material, a conductive material, and a binder, adding a suitable solvent to form a paste-like positive electrode mixture, applying the coating to the surface of the current collector 13 and drying it. Depending on the case, the electrode may be compressed to increase the electrode density. The liquid absorption height A of the positive electrode sheet 15 can be adjusted, for example, by adjusting the type and amount of the positive electrode active material, the conductive material, and the binder used, or adjusting the electrode density. The liquid absorption height A may be, for example, 1 mm or more, 2 mm or more, 5 mm or more. Moreover, it is good also as 50 mm or less, 30 mm or less, 20 mm or less.

As the positive electrode active material, a sulfide containing a transition metal element, an oxide containing lithium and a transition metal element, or the like can be used. Specifically, transition metal sulfides such as TiS ₂ , TiS ₃ , MoS ₃ , and FeS _2, and the basic composition formula are Li _(1-x) MnO ₂ (0 <x <1, etc., the same shall apply hereinafter) and Li _{(1 -x)} Lithium-manganese composite oxides such as Mn ₂ O _4, lithium cobalt composite oxides whose basic composition formula is Li _(1-x) CoO _2, etc., basic composition formulas such as Li _(1-x) NiO ₂ lithium nickel composite oxide, the basic compositional formula _{Li (1-x) Ni a} Co b Mn c O 2 ( where 0 <a <1,0 <b < 1,0 <c <1, a + b + c = 1 Lithium nickel cobalt manganese composite oxide such as LiV ₂ O ₃ as a basic composition formula, transition metal oxide such as V ₂ O ₅ as a basic composition formula, etc. it can. Of these, lithium transition metal composite oxides such as LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O _{2 and the} like are preferable. The “basic composition formula” means that the composition of each element may be different or may contain other elements.

  The conductive material is not particularly limited as long as it is an electron conductive material that does not adversely affect the battery performance of the positive electrode. For example, graphite such as natural graphite (scale-like graphite, scale-like graphite) or artificial graphite, acetylene black, carbon black, What mixed 1 type (s) or 2 or more types, such as ketjen black, carbon whisker, needle coke, carbon fiber, metal (copper, nickel, aluminum, silver, gold, etc.) can be used. Among these, as the conductive material, carbon black and acetylene black are preferable from the viewpoints of electron conductivity and coatability.

  The binder serves to bind the active material particles and the conductive material particles. For example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), fluorine-containing resin such as fluorine rubber, or polypropylene, Thermoplastic resins such as polyethylene, ethylene propylene diene monomer (EPDM) rubber, sulfonated EPDM rubber, natural butyl rubber (NBR) and the like can be used alone or as a mixture of two or more. In addition, an aqueous dispersion of cellulose or styrene butadiene rubber (SBR), which is an aqueous binder, can also be used.

  Examples of the solvent for dispersing the positive electrode active material, the conductive material, and the binder include N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethylenetriamine, and N, N-dimethylaminopropylamine. Organic solvents such as ethylene oxide and tetrahydrofuran can be used. Moreover, a dispersing agent, a thickener, etc. may be added to water, and an active material may be slurried with latex, such as SBR. As the thickener, for example, polysaccharides such as carboxymethyl cellulose and methyl cellulose can be used alone or as a mixture of two or more.

  Examples of the application method include roller coating such as applicator roll, screen coating, doctor blade method, spin coating, bar coater, and the like, and any of these can be used to obtain an arbitrary thickness and shape.

  As the current collector 13, in addition to aluminum, titanium, stainless steel, nickel, iron, calcined carbon, conductive polymer, conductive glass, etc., aluminum and copper are used for the purpose of improving adhesiveness, conductivity and oxidation resistance. A surface treated with carbon, nickel, titanium, silver or the like can be used. For these, the surface can be oxidized. Examples of the shape of the current collector 13 include a foil shape, a film shape, a sheet shape, a net shape, a punched or expanded shape, a lath body, a porous body, a foamed body, and a formed body of fiber groups. The current collector 13 has a thickness of 1 to 500 μm, for example.

  A negative electrode mixture layer 17 containing a negative electrode active material is formed on both surfaces of the negative electrode sheet 18. The negative electrode mixture layer 17 may be formed on one surface of the negative electrode sheet 18 depending on the structure to be employed. The thickness b per side of the negative electrode mixture layer 17 may be, for example, 10 μm or more and 500 μm or less, or 20 μm or more and 200 μm or less.

  For example, the negative electrode sheet 18 is prepared by mixing a negative electrode active material, a conductive material, and a binder, and adding a suitable solvent to form a paste-like negative electrode mixture on the surface of the current collector 16. Depending on the case, the electrode may be compressed to increase the electrode density. The liquid absorption height B of the negative electrode sheet 18 can be adjusted, for example, by adjusting the type and amount of the negative electrode active material, the conductive material, and the binder used, or adjusting the electrode density. The liquid absorption height B may be, for example, 1 mm or more, 2 mm or more, 5 mm or more. Moreover, it is good also as 50 mm or less, 30 mm or less, 20 mm or less.

  Examples of the negative electrode active material include a carbonaceous material capable of inserting and extracting lithium ions, a composite oxide containing a plurality of elements, and a conductive polymer. 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 have an operating potential close to that of metallic lithium, can be charged and discharged at a high operating voltage, and suppresses self-discharge when a lithium salt is used as a supporting salt. In addition, the irreversible capacity during charging can be reduced, which is preferable. Examples of the composite oxide include lithium titanium composite oxide and lithium vanadium composite oxide. Among these, as the negative electrode active material, a carbonaceous material is preferable from the viewpoint of safety. In addition, as the conductive material, the binder, the solvent, and the like used for the negative electrode sheet 18, those exemplified for the positive electrode sheet 15 can be used. The current collector 16 of the negative electrode sheet 18 includes copper, nickel, stainless steel, titanium, aluminum, calcined carbon, conductive polymer, conductive glass, Al-Cd alloy, and the like, as well as adhesion, conductivity, and reduction resistance. For the purpose of improving the properties, for example, a surface of copper or the like treated with carbon, nickel, titanium, silver or the like can be used. For these, the surface can be oxidized. The shape of the current collector 16 can be the same as that of the positive electrode.

  The separator 21 includes a positive electrode layer 20 and a negative electrode layer 19. The separator 21 may be composed of two layers, a positive electrode layer 20 and a negative electrode layer 19, and one or more layers are provided between the positive electrode layer 20 and the negative electrode layer 19. It may be configured. Each layer may be joined by welding or the like, or may not be joined. The material of each layer is not particularly limited as long as it is a composition that can withstand the use range of the lithium secondary battery 10. For example, a polymer nonwoven fabric such as a polypropylene nonwoven fabric or a polyphenylene sulfide nonwoven fabric, or an olefin resin such as polyethylene or polypropylene is used. A thin microporous membrane can be mentioned.

  In the separator 21, the liquid absorption height C of the positive electrode layer 20 and the liquid absorption height D of the negative electrode layer 19 are adjusted, for example, by the material, density, and hole shape of the material constituting the layer. Can be adjusted. The liquid absorption heights C and D may be, for example, 1 mm or more, 2 mm or more, 10 mm or more. Moreover, it is good also as 500 mm or less, 300 mm or less, 200 mm or less.

  In the separator 21, the thickness c of the positive electrode layer 20 and the thickness d of the negative electrode layer 19 are preferably 5 μm or more, more preferably 15 μm or more, and further preferably 25 μm or more. When a separator with a large thickness is used, the difference in the easiness of the flow of the electrolyte solution between the positive electrode and the negative electrode, the holding power of the electrolyte solution, etc. It can be mitigated. Although the upper limit of thickness c and d is not specifically limited, For example, it is good also as 500 micrometers or less, 200 micrometers or less, etc. Here, the thickness c of the positive electrode layer 20 and the negative electrode layer thickness d are, for example, preferably such that the value of c / d satisfies 0.05 or more and 15 or less, and satisfies 0.5 or more and 10 or less. Is more preferable. In addition, the thickness c of the positive electrode layer 20 is preferably 0.1 or more and 5 or less with respect to the thickness a of the positive electrode mixture layer 14. It is more preferable to satisfy the following. Further, the thickness d of the negative electrode layer 19 is preferably 0.1 to 5 in terms of d / b with respect to the thickness b of the negative electrode mixture layer 17. It is more preferable to satisfy the following. In addition, when the outermost layer on the positive electrode side or the negative electrode side of the separator 21 has a very thin layer such as 1 μm or less or 3 μm or less, or a layer that bears only mechanical strength, such a layer alone is used for the positive electrode side. The layer 20 and the negative electrode layer 19 are not handled. In this case, a positive-side layer including a very thin layer is treated as a positive-side layer 20, and a negative-side layer including a very thin layer is treated as a negative-side layer 19.

  As the non-aqueous electrolyte solution 22 of the lithium secondary battery 10, a non-aqueous electrolyte solution or a non-aqueous gel electrolyte solution in which a supporting salt is dissolved in a solvent can be used. Examples of the solvent include carbonates, esters, ethers, nitriles, furans, sulfolanes and dioxolanes, and these can be used alone or in combination. Specifically, as carbonates, cyclic carbonates such as ethylene carbonate, propylene carbonate, vinylene carbonate, butylene carbonate, chloroethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl-n-butyl carbonate, methyl-t -Chain carbonates such as butyl carbonate, di-i-propyl carbonate, t-butyl-i-propyl carbonate, cyclic esters such as γ-butyllactone and γ-valerolactone, methyl formate, methyl acetate, ethyl acetate, Chain esters such as methyl butyrate, ethers such as dimethoxyethane, ethoxymethoxyethane, and diethoxyethane; nitriles such as acetonitrile and benzonitrile; Examples include furans such as lan, methyltetrahydrofuran, sulfolanes such as sulfolane and tetramethylsulfolane, and dioxolanes such as 1,3-dioxolane and methyldioxolane. Among these, the combination of cyclic carbonates and chain carbonates is preferable. According to this combination, not only the cycle characteristics representing the battery characteristics in repeated charge and discharge are excellent, but also the viscosity of the electrolyte, the electric capacity of the obtained battery, the battery output, etc. should be balanced. it can. The cyclic carbonates are considered to have a relatively high relative dielectric constant and increase the dielectric constant of the electrolytic solution, and the chain carbonates are considered to suppress the viscosity of the electrolytic solution.

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, LiClO. ₄ , LiCl, LiF, LiBr, LiI, LiAlCl _{4 and the} like. Among these, from the group consisting of inorganic salts such as LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiClO ₄ , and organic salts such as LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) _3. It is preferable from the viewpoint of electrical characteristics to use a combination of one or two or more selected salts. The supporting salt preferably has a concentration in the non-aqueous electrolyte of 0.1 mol / L or more and 5 mol / L or less, and more preferably 0.5 mol / L or more and 2 mol / L or less. When the concentration for dissolving the supporting salt is 0.1 mol / L or more, a sufficient current density can be obtained, and when it is 5 mol / L or less, the electrolytic solution can be made more stable. Moreover, you may add flame retardants, such as a phosphorus type and a halogen type, to this non-aqueous electrolyte.

  In the lithium secondary battery 10 of this embodiment described in detail above, a separator having two or more layers, a separator having a high liquid absorption height is disposed on the electrode side having a low liquid absorption height, and an electrode having a high liquid absorption height. A separator having a low liquid absorption height is disposed on the side. For this reason, it is thought that the bias | inclination of the salt concentration which may arise by the difference in the ease of the distribution | circulation of the electrolyte solution in a positive electrode and the negative electrode, the retention strength of an electrolyte solution, etc. can be suppressed more. Specifically, the difference in the ease of circulation of the electrolyte between the positive electrode and the negative electrode, the retention of the electrolyte, etc. are alleviated by the supply and retention of the electrolyte in each layer of the separator. It is thought that the bias can be suppressed. For this reason, it is thought that the resistance increase at the time of high rate charge / discharge can be suppressed more.

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

  For example, in the above-described embodiment, the electrode structure 11 is described by laminating and winding the positive electrode sheet 15, the negative electrode sheet 18, and the separator 21, but is not particularly limited thereto. Good. In the embodiment described above, the shape of the lithium secondary battery is a cylindrical shape, but is not particularly limited thereto, and examples thereof include a coin shape, a button shape, a sheet shape, a stacked shape, a flat shape, and a square shape. . Moreover, you may apply to the large sized thing etc. which are used for an electric vehicle etc.

  FIG. 4 is a schematic diagram showing an example of another lithium secondary battery 30 of the present invention. As shown in FIG. 4, the coin-type lithium secondary battery 30 includes a cup-shaped battery case 33, a positive electrode mixture layer 34 that has a positive electrode active material and is provided inside the battery case 33, and a negative electrode active material. A negative electrode mixture layer 37 provided at a position facing the positive electrode mixture layer 34 with the separator 41 interposed therebetween, a gasket 43 formed of an insulating material, and an opening of the battery case 33. And a sealing plate 36 that seals the battery case 33 through the gasket 43. The lithium secondary battery 30 contains a non-aqueous electrolyte solution 42 that conducts lithium ions in a battery case 33. The electrode structure 31 includes a positive electrode 35 including a battery case 33 and a positive electrode mixture layer 34, a negative electrode 38 including a sealing plate 36 and a negative electrode mixture layer 37, and a separator 41 interposed between the positive electrode 35 and the negative electrode 38. It has. In the lithium secondary battery 30 and the electrode structure 31, the separator 41 includes a positive electrode layer 40 and a negative electrode layer 39. The liquid absorption heights A to D of the positive electrode 35 (may be the positive electrode mixture layer 34), the negative electrode 38 (may be the negative electrode mixture layer 37), the positive electrode side layer 40, and the negative electrode side layer 39 are (D− C) / (AB)> 0 is satisfied. In a battery that is not a wound type, such as the coin-type lithium secondary battery 30, the sampling direction of the test piece used for measuring the liquid absorption height is not particularly limited. In addition, since general electrode materials and separator materials are considered to have very small in-plane anisotropy, the influence of the specimen sampling direction on the value of (DC) / (AB) is very large. It is thought that it is small. The electrode structure 31 has a structure having one positive electrode mixture layer 34 and one negative electrode mixture layer 37, but may have a multilayer structure. In this case, among the separators between the positive electrode mixture layer and the negative electrode mixture layer, one or more separators, preferably all separators, are two or more separators, the positive electrode mixture layer, the negative electrode mixture layer, The liquid absorption heights A to D of the layer on the positive electrode side of the separator and the layer on the negative electrode side of the separator need only satisfy (DC) / (AB)> 0.

  In the above-described embodiment, the lithium secondary batteries 10 and 30 including the electrode structures 11 and 31 have been described. However, the electrode structures 11 and 31 used for the lithium secondary battery may be used. Even if it does in this way, when it uses for a lithium secondary battery, there exists the same effect as a lithium secondary battery.

  In the embodiment described above, the electrode structures 11 and 31 are used for the lithium secondary batteries 10 and 30, but may be used other than the lithium secondary battery. For example, the positive electrode or the negative electrode may be used for a battery (such as an alkali metal secondary battery, an alkaline earth metal secondary battery, or an onium battery) that occludes and releases alkali metal, alkaline earth metal, and onium instead of lithium. Good. Moreover, you may use for not only a battery but a capacitor, the hybrid capacitor which combined the battery and the capacitor, etc.

  Below, the example which produced the battery of this invention concretely is demonstrated as an Example. Here, a lithium ion secondary battery using a nickel-cobalt-manganese (NCM) -based material as a positive electrode active material, graphite as a negative electrode active material, and a non-aqueous electrolyte solution as an electrolytic solution was manufactured.

[Example 1]
(Production of battery)
91% by mass of NCM material (LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ) as the positive electrode active material, 6% by mass of acetylene black (Electrochemical Industry HS100) as the conductive material, and polyfluoride as the binder. A positive electrode mixture was prepared by mixing 3% by mass of vinylidene chloride (KF polymer, Kureha Chemical Industries). The obtained positive electrode mixture was dispersed in N-methyl-2-pyrrolidone (NMP) to obtain a paste. The paste was applied to both sides of an aluminum foil having a thickness of 15 μm, dried, and roll-pressed to form a positive electrode sheet electrode. Got. The thickness of the positive electrode mixture layer was 65 μm per side. The positive electrode sheet electrode was 54 mm × 450 mm.

  A negative electrode mixture was prepared by mixing 98% by mass of graphite as a negative electrode active material, 1% by mass of carboxymethyl cellulose (CMC) as a thickener, and 1% by mass of styrene butadiene rubber (SBR) as a binder. The obtained negative electrode mixture was dispersed in water to obtain a paste. This paste was applied to both sides of a 10 μm thick copper foil, dried, and roll pressed to obtain a negative electrode sheet electrode. The thickness of the negative electrode mixture layer was 68 μm per side. The negative electrode sheet electrode was 56 mm × 500 mm.

  Phosphorus hexafluoride was added to a non-aqueous solvent in which ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) were mixed at a volume ratio of EC: DMC: EMC = 30: 40: 30. Lithium acid was added to 1 mol / L to obtain an electrolytic solution.

  The above positive / negative electrode sheet electrodes are wound in a roll shape through a separator 1 (58 mm × 500 mm) in which a 15 μm-thick positive electrode side layer and a 15 μm-thick negative electrode side layer are welded, and a test 18650 type battery After inserting into the can and injecting the above electrolyte, the top cap was caulked and sealed.

(Derivation of (DC) / (AB))
About the separator and the electrode, the following evaluation was performed according to the birec method of JIS L 1907: 2010. A test piece for evaluation was prepared by separating the two layers of the separator, the positive electrode, and the negative electrode into 2.5 cm × 20 cm, respectively. In that case, the test piece was produced so that the axial direction of the battery might be the longitudinal direction of the test piece. Next, one end in the longitudinal direction of each test piece was sandwiched between clips fixed at an appropriate height, and a weight was attached to the other end in the longitudinal direction and suspended. A part of the test piece on the side with the weight (about 2 cm at the lower end) was immersed in a container containing propylene carbonate (PC). The height at which the test piece absorbed in 10 minutes was measured from the position of the liquid surface of propylene carbonate, with the time when the immersion was started as 0 minutes. And the liquid absorption height A (mm) of the positive electrode, the liquid absorption height B (mm) of the negative electrode, the liquid absorption height C (mm) of the separator layer facing the positive electrode, the liquid absorption height of the separator layer facing the negative electrode The thickness D (mm) was measured, and the value of (DC) / (AB) was determined.

(Charge / discharge test)
The manufactured battery was first subjected to activation charge / discharge cycle (conditioning), and then subjected to a high-rate deterioration durability test to evaluate the high-rate deterioration durability performance. The test conditions for the high rate deterioration durability test are as follows. All evaluations were performed in a 20 ° C. environment. First, the battery was adjusted to SOC 60%. Then, the battery was discharged at a rate of 10 C for 10 seconds and rested for 5 seconds. Subsequently, the SOC was returned to 60% by charging at a rate of 2.5 C for 40 seconds, and then a 5-second pause was put. This charge / discharge cycle was performed 8000 times.

(Resistance measurement)
Resistance was evaluated by IV resistance. In the measurement of IV resistance, the evaluation cell was adjusted to SOC 60% in a temperature environment of 20 ° C., and after resting for 10 minutes, the cell was discharged at a constant current of 30 C for 10 seconds (CC discharge). Here, the lower limit voltage during discharge was set to 3.0V. From this, the slope of V = IR (R = V / I) was taken as IV resistance. This resistance measurement is performed before and after the high-rate deterioration durability test described above, and the internal resistance R ₀ [V] before the high-rate deterioration durability test and the internal resistance R [V] after the high-rate deterioration durability test are derived, and R × 100 / R _0. The rate of increase in internal resistance expressed by

[Example 2]
Evaluation was performed in the same manner as in Example 1 except that the separator 2 (58 mm × 500 mm) in which a positive electrode layer having a thickness of 25 μm and a negative electrode layer having a thickness of 15 μm were welded was used instead of the separator 1.

[Example 3]
Evaluation was performed in the same manner as in Example 1 except that the separator 3 (58 mm × 500 mm) in which a positive electrode layer having a thickness of 50 μm and a negative electrode layer having a thickness of 15 μm were welded was used instead of the separator 1.

[Example 4]
Instead of the separator 1, a separator 4 (58 mm × 500 mm) in which a positive electrode layer having a thickness of 15 μm and a negative electrode layer having a thickness of 15 μm were welded was used, and the thickness of the positive electrode mixture layer was 112 μm per side. Evaluation was performed in the same manner as in Example 1.

[Example 5]
Instead of the separator 1, a separator 5 (58 mm × 500 mm) in which a positive electrode side layer having a thickness of 25 μm and a negative electrode side layer having a thickness of 15 μm were used was used, and the thickness of the positive electrode mixture layer was 112 μm per side. Evaluation was performed in the same manner as in Example 1.

[Example 6]
Instead of the separator 1, a separator 6 (58 mm × 500 mm) in which a 50 μm-thick positive electrode side layer and a 15 μm-thick negative electrode side layer were welded was used, and the thickness of the positive electrode mixture layer was 112 μm per side. Evaluation was performed in the same manner as in Example 1.

[Comparative Example 1]
Evaluation was performed in the same manner as in Example 1 except that a single-layer separator 7 (58 mm × 500 mm) made of polyethylene and made by a wet method was used instead of the separator 1.

[Comparative Example 2]
Evaluation was performed in the same manner as in Example 1 except that instead of the separator 1, a separator 8 (58 mm × 500 mm) in which a positive electrode layer having a thickness of 15 μm and a negative electrode layer having a thickness of 25 μm were welded was used.

[Experimental result]
Table 1 shows the values of A, B, C, and D, the value of (D−C) / (A−B), and the resistance increase rate. As shown in Table 1, in Examples 1 to 6 satisfying (DC) / (AB)> 0, the rate of increase in resistance was lower than those of Comparative Examples 1 and 2 not satisfying this. From this, it was found that the increase in internal resistance can be further suppressed in the present invention. In Example 6, the value of (D−C) / (A−B) was the largest at 41.5. In Example 6, the rate of increase in resistance was larger than the others, so (D−C) It was speculated that the value of / (A−B) may not be too large. For example, it was speculated that 100 or less is preferable. Further, in Example 6, where the value of | A−B | was the smallest as 4, the resistance increase rate was larger than the others, so it was assumed that the value of | A−B | For example, it was assumed that | A−B | ≧ 1 is more preferable.

  Further, in this example, since it was possible to find a relationship between the value of (DC) / (AB) and the rate of increase in resistance, it conformed to the birec method of JIS L 1907: 2010. It was found that the electrolytic solution holding power and the like can be evaluated by a simple method.

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

  The present invention can be used in the field of the battery industry and the like.

  DESCRIPTION OF SYMBOLS 10 Lithium secondary battery, 11 Electrode structure, 13 Current collector, 14 Positive electrode mixture layer, 15 Positive electrode sheet, 16 Current collector, 17 Negative electrode mixture layer, 18 Negative electrode sheet, 19 Negative electrode layer, 20 Positive electrode side Layer, 21 separator, 22 non-aqueous electrolyte, 23 cylindrical case, 24 positive electrode terminal, 26 negative electrode terminal, 30 lithium secondary battery, 31 electrode structure, 33 battery case, 34 positive electrode mixture layer, 35 positive electrode, 36 sealing Plate, 37 negative electrode mixture layer, 38 negative electrode, 39 negative electrode side layer, 40 positive electrode side layer, 41 separator, 42 non-aqueous electrolyte, 43 gasket, 50 horizontal bar, 52 container, 60 test piece, 62 lower end, 64 spindles, 66 test solutions.

Claims (6)

A positive electrode, a negative electrode, and two or more layers of separators interposed between the positive electrode and the negative electrode,
Absorbing height of the positive electrode was measured as A (mm), the absorbing height of the negative electrode was B (mm), and the absorbing liquid of the layer on the positive electrode side of the separator was measured by absorbing the test solution for 10 minutes by the Bayrec method. When the height is C (mm) and the liquid absorption height of the negative electrode layer of the separator is D (mm), (D−C) / (A−B)> 0 is satisfied.
Electrode structure.   The electrode structure according to claim 1, wherein 0 <(D−C) / (A−B) ≦ 100 is satisfied.   The electrode structure according to claim 1, wherein | A−B | ≧ 1 is satisfied.   The electrode structure according to claim 1, wherein the sample solution is propylene carbonate. The electrode structure is a wound electrode structure,
The electrode structure according to claim 1, wherein the liquid absorption height is an axial liquid absorption height. The electrode structure according to any one of claims 1 to 5,
A non-aqueous electrolyte that conducts lithium ions interposed between the positive electrode and the negative electrode;
Rechargeable lithium battery.

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