JP2015053288A - Battery provided with electrolyte holding layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery with a long service life, which does not undergo a remarkable decrease in the output thereof.SOLUTION: A lithium ion secondary battery is provided with: a positive electrode active material layer; a negative electrode active material layer; an electrolyte; a resin-made separator; and an electrolyte holding layer that is directly sandwiched between at least one active material layer of the active material layers and the resin-made separator. A solvent of the electrolyte jointly uses three kinds of ethylene carbonate, methyl ethyl carbonate and dimethyl carbonate. The thickness of the electrolyte holding layer is 1-7 μm, the density of the electrolyte holding layer is 1-3 g/cm, the porosity of the electrolyte holding layer is 25-75%, and the solution holding amount per 1 mof the electrolyte holding layer is 20-60 μL.

Description

  The present invention relates to a battery including an electrolyte solution holding layer.

  Conventionally, batteries having an active material layer having an active material, an electrolytic solution serving as a medium for ions to move between the positive electrode and the negative electrode, and a resin separator for preventing a short circuit between the positive electrode and the negative electrode are widely known. ing. At the time of manufacturing these batteries, a certain pressure was applied to the laminate in which the positive electrode having the positive electrode active material layer, the resin separator holding the electrolytic solution, and the negative electrode having the negative electrode active material layer were stacked. In general, the thickness is a specified thickness. In this manufacturing method, when the pressure is applied to the resin separator, the thickness of the resin separator itself decreases, and the electrolytic solution held in the resin separator is pushed out of the separator. If it does so, the quantity of the electrolyte solution which exists in the shortest distance of a positive electrode and a negative electrode will reduce, As a result, the performance of the battery fell.

  In the case of a secondary battery, a solid electrolyte interface film (hereinafter referred to as “SEI”) that prevents direct contact between the negative electrode active material and the electrolytic solution on the surface of the negative electrode by performing charge and discharge. It is known to form. Here, since the thickness of the negative electrode gradually increases with the formation of SEI, pressure is applied to the resin separator, and the thickness of the resin separator gradually decreases. As a result, when the charge / discharge cycle of the secondary battery is repeated, the capacity retention rate of the battery decreases significantly.

  As described above, in a battery using a resin separator, the thickness of the resin separator is reduced, resulting in a decrease in the amount of electrolytic solution existing between the shortest distance between the positive electrode and the negative electrode, which reduces the battery performance. It was the cause.

  On the other hand, Patent Documents 1-3 specifically describe a battery having an electrolyte solution retaining layer.

  However, a battery that employs an electrolyte solution retention layer other than a separator between the positive electrode and the negative electrode generally causes a decrease in output due to an increase in resistance or the like, and thus the battery performance as designed is not necessarily exhibited. Therefore, simply adopting the technique disclosed in Patent Documents 1-3 does not necessarily provide a high-performance battery.

JP 58-163172 A JP 2004-363048 A Japanese Patent Laid-Open No. 6-203819

  The present invention has been made in view of such circumstances, and a long-life battery that does not cause a significant decrease in output despite having an electrolyte solution retaining layer directly sandwiched between an active material layer and a resin separator. The purpose is to provide.

  The present inventor has intensively studied through many trials and errors. The present inventor has found that a battery in which an electrolyte solution retaining layer showing a retaining amount in a specific range is directly sandwiched between an active material layer and a resin separator does not cause a significant decrease in output and has a long life. The present invention has been completed.

The battery of the present invention includes an active material layer, an electrolyte solution, a resin separator, and an electrolyte solution holding layer directly sandwiched between the active material layer and the resin separator, and the electrolyte solution holding layer 1 m ^2. The amount of the retentate per unit is 20 to 60 μL.

  The battery of the present invention has a long life without causing a significant decrease in output despite having an electrolyte solution retaining layer directly sandwiched between the active material layer and the resin separator.

  Below, the form for implementing this invention is demonstrated. Unless otherwise specified, the numerical range “ab” described herein includes the lower limit “a” and the upper limit “b”. The numerical range can be configured by arbitrarily combining these upper limit value and lower limit value and the numerical values listed in the examples. Furthermore, numerical values arbitrarily selected from the numerical value range can be used as upper and lower numerical values.

The battery of the present invention includes an active material layer, an electrolyte solution, a resin separator, and an electrolyte solution holding layer directly sandwiched between the active material layer and the resin separator, and the electrolyte solution holding layer 1 m ^2. The amount of the retentate per unit is 20 to 60 μL.

  With respect to the type of the battery of the present invention, the type of the battery is not limited as long as the battery includes an active material layer, an electrolytic solution, and a resin separator. The battery of the present invention may be a primary battery such as a manganese battery, an alkaline manganese battery, a nickel battery, a silver oxide battery, a mercury battery, or a lithium battery, or a secondary battery such as a lithium ion secondary battery, a nickel hydrogen rechargeable battery, or a nickel cadmium storage battery. A secondary battery may be used. The battery of the present invention is preferably a secondary battery, and particularly preferably a lithium ion secondary battery, since a battery having SEI formed after repeated charge and discharge has a suitable effect.

The battery of the present invention can be mounted on a vehicle. The vehicle may be any vehicle that uses electric energy from a battery as a whole or a part of a power source. For example, an electric vehicle, a hybrid vehicle, a plug-in hybrid vehicle, a hybrid railway vehicle, an electric forklift, an electric wheelchair, and an electric assist. Bicycles and electric motorcycles are examples. In particular, among the batteries of the present invention, those having a liquid retention amount of 20 to 40 μL per 1 m ² of the electrolyte liquid retention layer are particularly high in output, and thus are preferably mounted on a hybrid vehicle requiring a high output battery. In addition, among the batteries of the present invention, those having a liquid retention amount of 40 to 60 μL per 1 m ² of the electrolyte liquid retention layer have a particularly long life, and thus are preferably mounted on an electric vehicle that requires a long life battery. .

  Hereinafter, although the case where the kind of battery is a lithium ion secondary battery is mainly demonstrated, the battery of this invention is not limited to a lithium ion secondary battery.

  The active material layer is a layer having an active material formed on the current collector.

  A current collector refers to a chemically inert electronic high conductor that continues to pass current through an electrode during battery discharge or charge. As a material of the current collector, at least one selected from silver, copper, gold, aluminum, magnesium, tungsten, cobalt, zinc, nickel, iron, platinum, tin, indium, titanium, ruthenium, tantalum, chromium, molybdenum, or Examples thereof include metal materials such as stainless steel and carbon materials such as graphite. In particular, aluminum or copper is preferable as the current collector material from the viewpoints of electrical conductivity, workability, and cost. The current collector can take the form of a foil, a sheet, a film, a linear shape, a rod shape, a mesh, or the like. Therefore, for example, a metal foil such as a copper foil, a nickel foil, an aluminum foil, and a stainless steel foil can be suitably used as the current collector. When the current collector is in the form of foil, sheet or film, the thickness is preferably in the range of 10 μm to 100 μm.

  The active material is a substance that performs an oxidation reaction for sending electrons and / or a reduction reaction for receiving electrons. In addition, it can be said that the active material is a substance that releases ions to the electrolytic solution or a substance that receives ions from the electrolytic solution in accordance with the oxidation-reduction reaction. For example, the active material of a lithium ion secondary battery is a substance that can occlude and release lithium ions. An active material used in the positive electrode is referred to as a positive electrode active material, and an active material used in the negative electrode is referred to as a negative electrode active material.

As the positive electrode active material, a known material employed in each battery may be used. For example, as the positive electrode active material of a lithium ion secondary _{battery, Li a Ni b Co c Mn} d D e O f (0.2 ≦ a ≦ 1, b + c + d + e = 1,0 ≦ e <1, D is Li, Fe , Cr, Cu, Zn, Ca, Mg, S, Si, Na, K, Al, 1.7 ≦ f ≦ 2.1), Li ₂ MnO ₂ , Li ₂ MnO ₃ , LiFePO ₄ , and lithium-containing metal oxides such as Li ₂ FeSO ₄ . In addition, the positive electrode active material of the lithium ion secondary battery is represented by LiMPO ₄ , LiMVO ₄ or Li ₂ MSiO ₄ (wherein M is selected from at least one of Co, Ni, Mn, and Fe). A polyanionic compound can be mentioned.

As the positive electrode active material of the lithium ion secondary batteries, from the viewpoint of high _{capacity, Li a Ni b Co c Mn} d D e O f (0.2 ≦ a ≦ 1, b + c + d + e = 1,0 of the layered rock-salt structure < b <1, 0 <c <1, 0 <d <1, 0 ≦ e <1, D is selected from Li, Fe, Cr, Cu, Zn, Ca, Mg, S, Si, Na, K, Al Preferably at least one element, 1.7 ≦ f ≦ 2.1), of which 0 <b <70/100, 0 <c <50/100, 10/100 <d <1 Preferably, those within the ranges of 1/3 ≦ b ≦ 50/100, 20/100 ≦ c ≦ 1/3, 1/3 ≦ d <1, more preferably b = 1/3, c = 1/3, Particularly preferred are those where d = 1/3, or b = 50/100, c = 20/100, and d = 30/100.

As the negative electrode active material, a known material employed in each battery may be used. For example, as a negative electrode active material of a lithium ion secondary battery, a carbon-based material that can occlude and release lithium, an element that can be alloyed with lithium, a compound that has an element that can be alloyed with lithium, or a polymer material is exemplified. can do. Examples of the carbon-based material include non-graphitizable carbon, artificial graphite, natural graphite, cokes, graphites, glassy carbons, organic polymer compound fired bodies, carbon fibers, activated carbon, and carbon blacks. Here, the organic polymer compound fired body refers to a material obtained by firing and carbonizing a polymer material such as phenols and furans at an appropriate temperature. Specifically, elements that can be alloyed with lithium include Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Ti, Ag, Zn, Cd, Al, Ga, In, Si. , Ge, Sn, Pb, Sb, Bi can be exemplified, and Si or Sn is particularly preferable. Specific examples of the compound having an element that can be alloyed with lithium include ZnLiAl, AlSb, SiB ₄ , SiB ₆ , Mg ₂ Si, Mg ₂ Sn, Ni ₂ Si, TiSi ₂ , MoSi ₂ , CoSi ₂ , NiSi ₂ , _{CaSi 2, CrSi 2, Cu 5} Si, FeSi 2, MnSi 2, NbSi 2, TaSi 2, VSi 2, WSi 2, ZnSi 2, SiC, Si 3 N 4, Si 2 N 2 O, SiO v (0 <v ≦ 2), SnO _w (0 <w ≦ 2), SnSiO ₃ , LiSiO 2 or LiSnO, and SiO _x (0.5 ≦ x ≦ 1.5) is particularly preferable. Moreover, tin compounds (Cu-Sn alloy, Co-Sn alloy, etc.) can be illustrated as a compound which has an element which can be alloyed with lithium. Specific examples of the polymer material include polyacetylene and polypyrrole.

  The active material layer includes a binder and / or a conductive aid as necessary.

  The binder plays a role of binding the active material to the surface of the current collector. As binders, fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene and fluororubber, thermoplastic resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamideimide, carboxymethylcellulose, methylcellulose and styrene-butadiene rubber Well-known materials such as alkoxysilyl group-containing resins can be used. These binders can be added to the active material layer alone or in combination of two or more. Although there is no restriction | limiting in particular about the usage-amount of a binder, The range of 1-50 mass parts of binders with respect to 100 mass parts of active materials is preferable. This is because when the amount of the binder is too small, the moldability of the electrode is lowered, and when the amount of the binder is too large, the energy density of the electrode is lowered.

  A conductive additive is added to increase conductivity. Examples of the conductive assistant include carbon black, graphite, acetylene black, ketjen black (registered trademark), and vapor grown carbon fiber (Vapor Grown Carbon Fiber) which are carbonaceous fine particles. These conductive assistants can be added to the active material layer alone or in combination of two or more. Although there is no restriction | limiting in particular about the usage-amount of a conductive support agent, For example, it can be set as 1-30 mass parts of conductive support agents with respect to 100 mass parts of active materials.

  In order to form an active material layer on the surface of the current collector, the surface of the current collector can be formed using a conventionally known method such as a roll coating method, a dip coating method, a doctor blade method, a spray coating method, or a curtain coating method. The active material may be directly applied to the surface. Specifically, a composition for forming an active material layer containing an active material and, if necessary, a binder and / or a conductive aid is prepared, and an appropriate solvent is added to the composition to obtain a paste-like liquid. To do. A solution in which a binder is dissolved in a solvent in advance or a dispersed suspension may be used. Examples of the solvent include N-methyl-2-pyrrolidone, methanol, ethanol, methyl isobutyl ketone, and water. The paste-like liquid is applied to the surface of the current collector and then dried. Drying may be performed under normal pressure conditions or under reduced pressure conditions using a vacuum dryer. What is necessary is just to set drying temperature suitably, and the temperature beyond the boiling point of the said solvent is preferable. What is necessary is just to set drying time suitably according to an application quantity and drying temperature. In order to increase the density of the active material layer, a compression step may be added to the dried current collector on which the active material layer is formed.

  The electrolytic solution is a solution containing a solvent and an electrolyte dissolved in the solvent. As the electrolytic solution, a known one used in each battery may be used.

  Examples of the solvent used for the electrolyte solution of the lithium ion secondary battery include non-aqueous solvents such as cyclic esters, chain esters, and ethers. Examples of cyclic esters include ethylene carbonate, propylene carbonate, butylene carbonate, gamma butyrolactone, vinylene carbonate, 2-methyl-gamma butyrolactone, acetyl-gamma butyrolactone, and gamma valerolactone. Examples of chain esters include dimethyl carbonate, diethyl carbonate, dibutyl carbonate, dipropyl carbonate, methyl ethyl carbonate, propionic acid alkyl ester, malonic acid dialkyl ester, and acetic acid alkyl ester. Examples of ethers include tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane, and 1,2-dibutoxyethane. A plurality of the above-described solvents may be used in combination as the solvent for the electrolytic solution. In particular, it is preferable to use three types of ethylene carbonate, methyl ethyl carbonate, and dimethyl carbonate in combination.

Examples of the electrolyte of the lithium ion secondary battery include lithium salts such as LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , and LiN (CF ₃ SO ₂ ) ₂ . The concentration of the electrolyte in the electrolytic solution is preferably in the range of 0.5 to 1.7 mol / L.

  The resin separator separates the positive electrode and the negative electrode, and allows ions to pass while preventing a short circuit of current due to contact between the two electrodes. As the resin separator, a known separator employed in each battery may be used, for example, a porous film using one or more synthetic resins such as polytetrafluoroethylene, polypropylene, polyethylene, polyester, polyamide, etc. it can. The resin separator may have a single-layer structure using a single synthetic resin or a laminated structure in which a plurality of synthetic resin layers are stacked. The thickness of the resin separator is not particularly limited, but is preferably in the range of 5 μm to 100 μm, more preferably in the range of 10 μm to 50 μm, and particularly preferably in the range of 20 μm to 30 μm.

The electrolyte solution holding layer is a layer having a space capable of holding the electrolyte solution. The electrolyte solution retaining layer of the present invention is characterized in that the amount of retained solution per 1 m ² of the electrolyte solution retaining layer is 20 to 60 μL. It is more preferable that the liquid retention amount per 1 m ^{2 of the} electrolyte liquid retention layer is 30 to 50 μL.

The electrolyte solution retaining layer is made of Al ₂ O ₃ , SiO ₂ , TiO ₂ , ZrO ₂ , MgO, SiC, AlN, BN, CaCO ₃ , MgCO ₃ , BaCO ₃ , talc, mica, kaolinite, CaSO ₄ , MgSO ₄ , One or more inorganic compounds selected from BaSO ₄ , CaO, ZnO, and zeolite, or particles composed of a resin compound having a hardness higher than that of the resin separator used, and a binder as necessary.

  As particles composed of a resin compound, a known particulate resin compound such as polyfluoroethylene, polypropylene, polyethylene, polyester, polyamide, polyethylene terephthalate, and the like having a higher hardness than the resin separator to be used is appropriately selected. It ’s fine.

  As the binder used in the electrolyte solution retaining layer, the binder described in the description of the active material layer may be employed singly or in combination. As the binder used for the electrolyte solution retaining layer, polyvinylidene fluoride is particularly preferable from the viewpoint of electrochemical stability.

  As a particle diameter of the particle | grains which consist of an inorganic compound or a resin compound, a thing with an average particle diameter of 0.1-10 micrometers is preferable, a 0.2-5 micrometers thing is more preferable, and a 0.5-3 micrometers thing is especially preferable. If the average particle size is too small, it may be difficult to form a space capable of holding the electrolytic solution. If the average particle size is too large, the thickness of the electrolyte solution retaining layer increases, and thus the resistance caused by the increase in thickness may adversely affect the battery output. In addition, what is necessary is just to measure an average particle diameter with general particle size distribution measuring apparatuses, such as a laser diffraction type particle size distribution measuring apparatus.

  When the electrolytic solution holding layer contains an inorganic compound, it is preferable to add a binder to the electrolytic solution holding layer. In this case, the preferred mass ratio between the inorganic compound and the binder is 5: 1 to 200: 1, more preferably 10: 1 to 150: 1, and particularly preferably 15: 1 to 100: 1. .

  The thickness of the electrolyte solution retaining layer is not particularly limited, but is preferably 0.1 to 10 μm, more preferably 0.5 to 8 μm, and particularly preferably 1 to 7 μm.

Although the density of the electrolyte solution holding layer is not particularly limited but is preferably 0.1 to 3 g / cm ^3, more preferably ^{0.5~2.5g / cm 3, 1~2g / cm} 3 is particularly preferred.

  The porosity of the electrolyte solution retaining layer is not particularly limited, but is preferably 5 to 90%, more preferably 15 to 85%, further preferably 20 to 80%, and particularly preferably 25 to 75%.

  The electrolyte solution retaining layer of the present invention is directly sandwiched between the active material layer and the resin separator. The active material layer may be a positive electrode active material layer, a negative electrode active material layer, or both active material layers.

  In order to provide an electrolytic solution holding layer on an active material layer or a resin separator, the electrolytic solution holding layer is formed by dispersing constituent components of the electrolytic solution holding layer in a solvent. After performing the process of preparing the composition for a liquid and the process of apply | coating the said composition for electrolyte solution liquid retention layer formation on an active material layer or a resin-made separator, what is necessary is just to implement a drying process. The blending amount of the constituent components of the electrolyte solution retention layer in the composition for forming an electrolyte solution retention layer is preferably in the range of 10 to 50% by mass. By changing the blending amount, the density and porosity of the electrolyte solution retaining layer to be formed can be changed. As the solvent used for the preparation of the electrolyte solution retaining layer forming composition, those in which particles composed of an inorganic compound or a resin compound are not dissolved are preferable. For example, N-methyl-2-pyrrolidone, methanol, ethanol, methyl isobutyl ketone What is necessary is just to select suitably from water. In the coating process, a conventionally known method such as a roll coating method, a dip coating method, a doctor blade method, a spray coating method, or a curtain coating method may be used. The drying step may be performed under normal pressure conditions or under reduced pressure conditions using a vacuum dryer. The drying temperature may be appropriately set within a range where the binder does not decompose, and a temperature equal to or higher than the boiling point of the solvent is preferable. What is necessary is just to set drying time suitably according to an application quantity and drying temperature.

  And the process of installing a resin separator on the electrolyte solution holding layer of the active material layer having the electrolyte solution holding layer, or the active material on the electrolyte solution holding layer of the resin separator having the electrolyte solution holding layer The battery of the present invention is manufactured through a step of installing a layer and a step employed in a conventional battery manufacturing method.

  As mentioned above, although embodiment of the battery of this invention was described, this invention is not limited to the said embodiment. The present invention can be implemented in various forms without departing from the gist of the present invention, with modifications and improvements that can be made by those skilled in the art.

  Hereinafter, the present invention will be described in more detail with reference to examples. In addition, this invention is not limited to a following example.

Example 1
The battery of the present invention was manufactured as follows.

96 parts by mass of Al ₂ O ₃ and 4 parts by mass of polyvinylidene fluoride were mixed to prepare a mixture. N-methyl-2-pyrrolidone was added to the mixture to prepare an electrolyte solution retention layer forming composition containing 32% by mass of the mixture.

98.3 parts by mass of natural graphite as a negative electrode active material, 1 part by mass of styrene butadiene rubber as a binder, and 0.7 parts by mass of carboxymethylcellulose were mixed. This mixture was dispersed in an appropriate amount of ion-exchanged water to prepare a slurry. A copper foil having a thickness of 20 μm was prepared as a negative electrode current collector. The slurry was applied in a film form on the surface of the copper foil using a doctor blade. The copper foil coated with the slurry was dried to remove water, and then the copper foil was pressed to obtain a bonded product. The obtained joined product was heat-dried at 120 ° C. for 6 hours with a vacuum dryer to obtain a copper foil on which a negative electrode active material layer was formed. The mass of the negative electrode active material layer per 1 cm ^{2 of the} copper foil was 11.1 mg, and the density of the negative electrode active material layer was 1.4 g / cm ³ . On the negative electrode active material layer of copper foil, the said composition for electrolyte solution retention layer formation was apply | coated to the film form using the doctor blade. This was dried at 120 ° C. for 6 hours to obtain a copper foil in which an electrolyte solution retaining layer having a film thickness of 4 μm, a density of 2 g / cm ³ and a porosity of 50% was formed on the negative electrode active material layer. This was used as a negative electrode.

94 parts by mass of a lithium-containing metal oxide having a layered rock salt structure represented by LiNi _5/10 Co _2/10 Mn _3/10 O _{2 as} a positive electrode active material, 3 parts by mass of acetylene black as a conductive auxiliary agent, and a binder 3 parts by mass of polyvinylidene fluoride as an agent was mixed. This mixture was dispersed in an appropriate amount of N-methyl-2-pyrrolidone to prepare a slurry. An aluminum foil having a thickness of 20 μm was prepared as a positive electrode current collector. The slurry was applied to the surface of the aluminum foil using a doctor blade so as to form a film. The aluminum foil coated with the slurry was dried at 80 ° C. for 20 minutes to remove N-methyl-2-pyrrolidone by volatilization to obtain an aluminum foil on which a positive electrode active material layer was formed. The mass of the positive electrode active material layer per 1 cm ^{2 of the} aluminum foil was 18.4 mg, and the density of the positive electrode active material layer was 3.3 g / cm ³ . The aluminum foil on which this positive electrode active material layer was formed was used as the positive electrode.

  A rectangular sheet (27 × 32 mm, thickness 25 μm) made of a polyethylene resin film was prepared as a resin separator.

A resin separator was installed on the electrolyte solution holding layer of the negative electrode, and then the positive electrode was installed to form an electrode plate group. The electrode plate group was covered with a set of two laminated films, and the three sides were sealed, and then an electrolyte solution was injected into the bag-like laminated film. As an electrolytic solution, a solution in which LiPF ₆ was dissolved to 1 mol / L in a solvent obtained by mixing 30 parts by volume of ethylene carbonate, 30 parts by volume of methyl ethyl carbonate, and 40 parts by volume of dimethyl carbonate was used. Thereafter, the remaining one side was sealed to obtain a lithium ion secondary battery in which the four sides were hermetically sealed and the electrode plate group and the electrolyte were sealed. This battery was referred to as the battery of Example 1. The amount of electrolyte solution retained per 1 m ² of electrolyte solution retaining layer in the battery of Example 1 was 40 μL.

  In addition, the positive electrode and negative electrode of the battery of Example 1 are provided with a tab that can be electrically connected to the outside, and a part of this tab extends to the outside of the lithium ion secondary battery.

(Example 2)
A battery of Example 2 was obtained in the same manner as in Example 1 except that the electrolyte solution retaining layer on the negative electrode active material layer was changed to a film thickness of 2 μm, a density of 2 g / cm ³ , and a porosity of 50%. The amount of electrolyte solution retained per 1 m ² of electrolyte solution retaining layer in the battery of Example 2 was 20 μL.

(Example 3)
A battery of Example 3 was obtained in the same manner as in Example 1 except that the electrolyte solution holding layer on the negative electrode active material layer was changed to a film thickness of 3 μm, a density of 2 g / cm ³ , and a porosity of 50%. The amount of electrolyte solution retained per 1 m ² of the electrolyte solution retaining layer in the battery of Example 3 was 30 μL.

Example 4
A battery of Example 4 was obtained in the same manner as in Example 1 except that the electrolyte solution retaining layer on the negative electrode active material layer was changed to a film thickness of 5 μm, a density of 2 g / cm ³ , and a porosity of 50%. The amount of electrolyte solution retained per 1 m ² of electrolyte solution retaining layer in the battery of Example 4 was 50 μL.

(Example 5)
A battery of Example 5 was obtained in the same manner as in Example 1 except that the electrolyte solution retention layer on the negative electrode active material layer was changed to a film thickness of 6 μm, a density of 2 g / cm ³ , and a porosity of 50%. The amount of electrolyte solution retained per 1 m ² of electrolyte solution retaining layer in the battery of Example 5 was 60 μL.

(Example 6)
A battery of Example 6 was obtained in the same manner as in Example 1 except that the electrolyte solution retention layer on the negative electrode active material layer was changed to a film thickness of 4 μm, a density of 2.8 g / cm ³ , and a porosity of 30%. . The amount of the electrolyte solution retained per 1 m ² of the electrolyte solution retaining layer in the battery of Example 6 was 24 μL.

(Example 7)
A battery of Example 7 was obtained in the same manner as in Example 1 except that the electrolyte solution retention layer on the negative electrode active material layer was changed to a film thickness of 4 μm, a density of 2.4 g / cm ³ , and a porosity of 40%. . The amount of the electrolyte solution retained per 1 m ² of the electrolyte solution retaining layer in the battery of Example 7 was 32 μL.

(Example 8)
A battery of Example 8 was obtained in the same manner as in Example 1 except that the electrolyte solution retention layer on the negative electrode active material layer was changed to a film thickness of 4 μm, a density of 1.6 g / cm ³ , and a porosity of 60%. . The amount of the electrolyte solution retained per 1 m ² of the electrolyte solution retaining layer in the battery of Example 8 was 48 μL.

Example 9
A battery of Example 9 was obtained in the same manner as in Example 1 except that the electrolyte solution retaining layer on the negative electrode active material layer was changed to a film thickness of 4 μm, a density of 1.2 g / cm ³ , and a porosity of 70%. . The amount of electrolyte solution retained per 1 m ² of electrolyte solution retaining layer in the battery of Example 9 was 56 μL.

(Comparative Example 1)
A battery of Comparative Example 1 was obtained in the same manner as in Example 1 except that the electrolyte solution retaining layer was not formed on the negative electrode active material layer.

(Comparative Example 2)
A battery of Comparative Example 2 was obtained in the same manner as in Example 1 except that the electrolyte solution holding layer on the negative electrode active material layer was changed to a film thickness of 10 μm, a density of 2 g / cm ³ , and a porosity of 50%. The amount of the electrolyte solution retained per 1 m ² of the electrolyte solution retaining layer in the battery of Comparative Example 2 was 100 μL.

<Battery evaluation>
The batteries of Examples 1, 2, and 5 and Comparative Examples 1 and 2 were subjected to the following test, and the capacity retention rate and output of the battery were measured. The results are shown in Table 1.

<Capacity maintenance rate>
When the battery to be measured is CCCV charged (constant current constant voltage charge) to 25 ° C, 1C rate, voltage 4.1V, and CCCV discharge (constant current constant voltage discharge) to 3V at a 0.33C rate The discharge capacity was measured and used as the initial capacity.

A cycle in which the battery is CC charged (constant current charge) to 25 ° C., 0.5 C rate, voltage 4.0 V, and CC discharged (constant current discharge) to 3.5 V at 0.5 C rate is defined as one cycle. This was repeated for 300 cycles. The discharge capacity of the battery after 300 cycles was measured by the same method as the measurement of the initial capacity, and the capacity retention rate was calculated. The capacity retention rate (%) was obtained by the following formula.
Capacity retention rate (%) = discharge capacity after 300 cycles / initial capacity × 100

<Output>
The output (W / g) was obtained by dividing the discharge power (W) for 5 seconds when the charging rate of the battery was 20% by the mass of the positive electrode active material layer.

  From the results in Table 1, it can be seen that the battery having the electrolyte solution retaining layer has an improved capacity retention rate, that is, a long life. As generally recognized from the results of Comparative Example 1 and Comparative Example 2, the battery of Comparative Example 2 has an electrolyte solution holding layer between the positive electrode active material layer and the negative electrode active material layer. It can be seen that a significant decrease in output was caused.

However, as is clear from the results of Examples 1, 2, and 5, even in the case of a battery having an electrolyte solution retaining layer, the amount of the electrolyte solution retained per 1 m ^{2 of the} electrolyte solution retaining layer is 20 to 60 μL. Within the range, it can be seen that the output is not significantly reduced and the output is equivalent to that of the battery having no electrolyte solution retention layer. In particular, it can be seen that the battery in which the amount of the electrolyte solution retained per 1 m ^{2 of} the electrolyte solution retaining layer is in the range of 20 to 40 μL maintains a high output without a decrease in output. Moreover, the battery in which the amount of electrolyte solution retained per 1 m ^{2 of} the electrolyte solution retaining layer is in the range of 40 to 60 μL exhibits a particularly excellent capacity retention rate, which indicates that the battery has an extremely long life.

  It was confirmed that the battery of the present invention has a long life without causing a significant decrease in output even though it has an electrolyte solution retention layer directly sandwiched between the active material layer and the resin separator.

Claims (7)

A positive electrode active material layer, a negative electrode active material layer, an electrolyte solution, a resin separator, and at least one active material layer of the active material layer and an electrolyte solution holding layer directly sandwiched between the resin separator;
The solvent of the electrolytic solution is a combination of ethylene carbonate, methyl ethyl carbonate, and dimethyl carbonate,
The electrolyte solution retention layer has a thickness of 1 to 7 μm,
The density of the electrolyte solution retaining layer is 1 to ³ g / cm ³ ,
The porosity of the electrolyte solution retaining layer is 25 to 75%,
The lithium ion secondary battery is characterized in that a liquid retention amount per 1 m ^{2 of the} electrolyte solution retention layer is 20 to 60 μL. The electrolyte solution retention layer is Al ₂ O ₃ , SiO ₂ , TiO ₂ , ZrO ₂ , MgO, SiC, AlN, BN, CaCO ₃ , MgCO ₃ , BaCO ₃ , talc, mica, kaolinite, CaSO ₄ , MgSO _4. , BaSO _4, CaO, ZnO, lithium ion secondary battery according to claim 1 comprising an inorganic compound and the binder is selected from zeolite.   3. The lithium ion secondary battery according to claim 2, wherein a mass ratio of the content of the inorganic compound and the binder in the electrolyte solution retaining layer is 5: 1 to 200: 1.   The lithium ion secondary battery according to claim 2 or 3, wherein the binder contains polyvinylidene fluoride.   The lithium ion secondary battery according to any one of claims 1 to 4, wherein the active material layer directly sandwiching the resin separator is a negative electrode active material layer.   The lithium ion secondary battery according to any one of claims 1 to 4, wherein the active material layer directly sandwiching the resin separator is a positive electrode active material layer. It is a manufacturing method of the lithium ion secondary battery in any one of Claims 1-6,
Preparing a composition for forming an electrolyte solution retention layer;
The manufacturing method including the process of apply | coating the said composition for electrolyte solution retention layer formation to an active material layer.