JP2019087523A - Composition for forming porous insulating layer, electrode for non-aqueous electrolyte secondary battery, non-aqueous electrolyte secondary battery, and manufacturing method of electrode for non-aqueous electrolyte secondary battery - Google Patents

Abstract

To provide a composition for forming a porous insulating layer and a manufacturing method of an electrode for a non-aqueous electrolyte secondary battery, which can suppress an increase in the thickness of an active material layer of an electrode, and an electrode for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery manufactured by the composition and the manufacturing method.SOLUTION: In a composition according to the present invention for forming a porous insulating layer on an active material layer disposed on the main surface of a current collector, and the active material layer includes at least an active material capable of electrochemically absorbing and desorbing lithium ions and an active material layer binder, and the composition for forming a porous insulating layer includes at least a solvent containing an organic solvent and insulating inorganic particles, and a distance between a Hansen solubility parameter of the active material layer binder and a Hansen solubility parameter of the organic solvent is 8.0 (MPa)or more.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a composition for forming a porous insulating layer, an electrode for a non-aqueous electrolyte secondary battery, a non-aqueous electrolyte secondary battery, and a method for producing an electrode for a non-aqueous electrolyte secondary battery.

  Non-aqueous electrolyte secondary batteries are also required to ensure safety while having relatively high energy density. For this reason, for example, a shutdown function is used to increase the internal resistance inside the battery by closing the pores of the separator by melting at the time of abnormal heating due to an internal short circuit of the battery or the like. In addition to the above-mentioned shutdown function by a separator, a method of directly forming a porous insulating layer on the electrode surface to prevent an internal short circuit has also been studied (for example, Patent Document 1).

  An electrode having such a heat-resistant insulating layer is produced, for example, as follows. First, an active material-containing paste as an aqueous slurry is applied onto a current collector, dried, and then pressurized to form an active material layer. Next, a material slurry constituting the porous insulating layer is applied onto the active material layer and dried to form a porous insulating layer.

JP, 2008-226566, A

  Here, the present inventors found that when the material slurry is applied onto the active material layer, the density of the active material layer is reduced due to the swelling of the active material layer due to the solvent in the material slurry. That is, since the active material layer has voids even after rolling, when the material slurry is applied, the liquid component in the slurry partially penetrates into the active material layer. The infiltrated liquid component affects the constituent material in the active material layer. The electrode after rolling has residual stress, but the infiltrated liquid component affects physical properties such as the elastic modulus of the constituent material. As a result, the balance of residual stress is lost and partial residual strain is released, and the active material It leads to the phenomenon that the layer thickness of the layer increases. When the layer thickness of the active material layer is larger than the designed thickness, a problem may occur when the battery element is inserted into the outer case. Although the increase in the layer thickness of the active material layer per layer is small, the battery element is usually a laminate in which a plurality of electrodes and separators are stacked, or a wound body in which a long electrode is wound, The increase in the thickness of the battery element due to the increase in the thickness of the plurality of active material layers can not be ignored.

  Such a problem becomes even more pronounced when the rolling of the active material layer is performed at a higher pressure in order to increase the energy density of the non-aqueous electrolyte secondary battery. That is, when the electrode density (filling factor of the active material layer) in the battery design is low, the design electrode density of the active material layer is set high beforehand at the time of electrode rolling in consideration of the electrode thickness increase after the porous insulating layer is formed. It was manageable by doing. However, with the recent increase in energy density of non-aqueous electrolyte secondary batteries, the design electrode density is high, so it is difficult to previously roll the active material layer to an electrode density higher than the design electrode density. There is a tendency. In addition, due to the demand for longer battery life, for example, as a negative electrode active material, there is a tendency to use hard-oriented graphite particles, and as a result, the pressure applied during electrode rolling is also increasing. Since the rolled electrode contains large residual stress and strain, the problem of the increase in film thickness when the material slurry is applied and dried becomes more serious, and it is necessary for the outer case of the non-aqueous electrolyte secondary battery. It can also develop into production problems such as being unable to load.

  Therefore, in the present invention, it is an object of the present invention to provide a composition for forming a porous insulating layer and a method for producing an electrode for a non-aqueous electrolyte secondary battery, which can suppress an increase in the thickness of the active material layer of the electrode. I assume. Another object of the present invention is to provide an electrode for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery produced thereby.

In order to solve the above problems, according to one aspect of the present invention, there is provided a composition for forming a porous insulating layer for forming a porous insulating layer on an active material layer disposed on the main surface of a current collector. There,
The active material layer contains at least an active material capable of electrochemically absorbing and desorbing lithium ions, and an active material layer binder.
The composition for forming a porous insulating layer contains at least a solvent containing an organic solvent, and insulating inorganic particles,
The composition for porous insulating layer formation whose distance of the Hansen solubility parameter of the said active material layer binder and the Hansen solubility parameter of the said organic solvent is 8.0 (MPa) ^1/2 or more.

  According to this aspect, when the porous insulating layer is formed, the thickness of the active material layer of the electrode is prevented from increasing.

The distance between the Hansen solubility parameter of the active material and the Hansen solubility parameter of the organic solvent may be 5.0 (MPa) ^1/2 or more.

  According to this aspect, the increase in the thickness of the active material layer of the electrode is further suppressed.

The distance between the Hansen solubility parameter of the active material and the Hansen solubility parameter of the organic solvent may be 8.0 (MPa) ^1/2 or more.

  According to this aspect, the increase in the thickness of the active material layer of the electrode is further suppressed.

In the organic solvent, the distance Ra (MPa) ^{1/2 of the} Hansen solubility parameter represented by the following formula (I) may be 5.0 (MPa) ^1/2 or more.

（式中、δ_{Ｄ（ｓｏｌｖｅｎｔ）}（ＭＰａ）^１／２は前記有機溶媒の分散項を、δ_{Ｐ（ｓｏｌｖｅｎｔ）}（ＭＰａ）^１／２は前記有機溶媒の極性項を、δ_{Ｈ（ｓｏｌｖｅｎｔ）}（ＭＰａ）^１／２は前記有機溶媒の水素結合項を、それぞれ示す。）

Wherein δ _{D (solvent)} (MPa) ^1/2 is the dispersion term of the organic solvent, δ _{P (solvent)} (MPa) ^1/2 is the polar term of the organic solvent, δ _{H (solvent)} ( MPa) ^1/2 represents the hydrogen bonding term of the organic solvent, respectively)

  According to this aspect, the increase in the thickness of the active material layer of the electrode is further suppressed.

  In addition, the composition for forming a porous insulating layer may further contain a binder.

  According to this aspect, the porous insulating layer can be suitably formed.

  The solvent may also contain water.

  According to this aspect, the dispersibility of the insulating inorganic particles can be improved.

  The boiling point of the organic solvent at 1 atm may be 160 ° C. or more.

  According to this aspect, it is possible to suppress a change in the physical properties of the composition for forming a porous insulating layer.

  The organic solvent may also contain an alcohol compound.

  The alcohol-based compound is suitably used from the viewpoint of the dispersibility of the insulating inorganic particles and the polyolefin-based polymer particles and the solubility of the binder, and the increase of the thickness of the active material layer of the electrode is further suppressed.

  The organic solvent may also contain a glycol alkyl ether compound.

  The glycol alkyl ether compound is suitably used from the viewpoint of the dispersibility of the insulating inorganic particles and the polyolefin polymer particles and the solubility of the binder.

  Further, the composition for forming a porous insulating layer may further contain polyolefin polymer particles.

  According to this aspect, the safety of the non-aqueous electrolyte secondary battery can be improved.

According to another aspect of the invention, a current collector
An active material layer disposed on the main surface of the current collector;
And a porous insulating layer formed on the active material layer by the composition for forming a porous insulating layer,
The active material layer is provided with an electrode for a non-aqueous electrolyte secondary battery including at least an active material capable of electrochemically absorbing and desorbing lithium ions and an active material layer binder.

  According to this aspect, in the manufactured electrode for a non-aqueous electrolyte secondary battery, the increase in the thickness of the active material layer is suppressed.

  According to another aspect of the present invention, there is provided a non-aqueous electrolyte secondary battery including the above-described electrode for a non-aqueous electrolyte secondary battery.

  According to this aspect, in the manufactured non-aqueous electrolyte secondary battery, the increase in the thickness of the active material layer is suppressed.

According to another aspect of the present invention, there is provided a step of forming a porous insulating layer on the active material layer disposed on the main surface of the current collector using the composition for forming a porous insulating layer,
The active material layer contains at least an active material capable of electrochemically absorbing and desorbing lithium ions, and an active material layer binder.
The composition for forming a porous insulating layer contains at least a solvent containing an organic solvent, and insulating inorganic particles,
There is provided a method for producing an electrode for a non-aqueous electrolyte secondary battery, wherein the distance between the Hansen solubility parameter of the active material layer binder and the Hansen solubility parameter of the organic solvent is 8.0 (MPa) ^1/2 or more. Ru.

  According to this aspect, it is possible to improve the cycle life when the non-aqueous electrolyte secondary battery is charged and discharged under high temperature and high voltage.

  As described above, according to the present invention, it is possible to suppress an increase in the thickness of the electrode of the non-aqueous electrolyte secondary battery.

BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing which shows schematic structure of the non-aqueous electrolyte secondary battery which concerns on embodiment of this invention.

  The present invention will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. In the present specification and the drawings, components having substantially the same functional configuration will be assigned the same reference numerals and redundant description will be omitted.

<1. Composition for forming porous insulating layer>
First, a composition for forming a porous insulating layer according to an embodiment of the present invention will be described. The composition for porous insulation layer formation concerning this embodiment is used in order to form a porous insulation layer on the active material layer of the electrode for nonaqueous electrolyte secondary batteries. The composition for forming a porous insulating layer according to the present embodiment contains at least a solvent containing an organic solvent and insulating inorganic particles, and further contains a material for forming the porous insulating layer, for example, a binder and the like. .

(1.1 solvent)
As mentioned above, the composition for porous insulation layer formation concerning this embodiment contains the solvent containing an organic solvent. The Hansen solubility parameter (hereinafter also referred to as “HSP”) of the binder (active material layer binder) in the active material layer and the HSP distance of the above organic solvent (hereinafter referred to as “first HSP distance”) ) Is 8.0 (MPa) ^1/2 or more.

  When the distance (first HSP distance) between the HSP of the organic solvent contained in the composition for forming the porous insulating layer and the HSP of the binder of the active material layer in the active material layer satisfies the relationship described above, the activity is activated. Even when the composition for forming a porous insulating layer is applied onto the material layer, the swelling of the active material layer is prevented. This prevents the thickness of the active material layer of the electrode from increasing.

Since the active material layer is generally subjected to rolling for the purpose of adjusting the density, it contains residual stress.
Even if the residual stress is contained, the shape is stable because the residual stress contained in the active material layer is balanced.

  The organic solvent generally used in the conventional composition for forming a porous insulating layer causes the active material layer binder to swell because the first HSP distance does not satisfy the above range. As a result, the elastic modulus of the active material layer binder is greatly reduced, the balance of the residual stress in the active material layer is broken, and the residual strain is released in the form of an increase in the layer thickness of the active material layer. On the other hand, in the present embodiment, the organic solvent has the relationship of the first HSP distance described above. Therefore, even when the composition for forming a porous insulating layer is applied on the active material layer, the swelling of the active material layer binder is suppressed, and as a result, the release of residual strain is also suppressed. The increase in layer thickness is also suppressed.

HSP is an extended concept in which the SP value of Hildebrandt, which is derived from the regular solution theory and obtained from the latent heat of evaporation and density of the material, is divided into three components: polar term δ _P , hydrogen bond term δ _H , and dispersion term δ _D is there. This is expressed as one point on a three-dimensional space. Therefore, in the calculation of the first HSP distance, the comparison between HSP of the binding agent and the solvent is discussed as the distance between two points (HSP distance) on the three-dimensional space, as shown in the following equation. In the present specification, HSP and the distance between HSPs and each component (polar term δ _P , hydrogen bond term δ _H , dispersion term δ _D ) are “(MPa) ^1/2 unless otherwise defined. Displayed based on the unit represented by

In the formula, δ _{D (binder)} is the dispersion term of the active material layer binder, δ _{D (solvent)} is the dispersion term of the organic solvent, and δ _{P (binder)} is the polarity term of the active material layer binder, δ _{P (solvent)} indicates the polar term of the organic solvent, δ _{H (binder)} indicates the hydrogen bonding term of the active material layer binder, and δ _{H (solvent)} indicates the hydrogen bonding term of the organic solvent.

Further, the upper limit of the above first HSP distance is not particularly limited, but in a general solvent, it falls within a value of 30 (MPa) ^1/2 or less.

  When a plurality of organic solvents are mixed, the HSP of the mixed solvent is calculated from the HSP of each organic solvent and the volume mixing ratio, and the distance between the HSP and the HSP of the active material layer binder (first The HSP distance should be at least 8.0. The HSP of the mixed solvent can be obtained by calculating the center of gravity after weighting each volume mixing ratio to one point of each solvent arranged in the three-dimensional space of HSP.

  Furthermore, when multiple types of active material layer binders are contained in the active material layer, the organic solvent is about 45% by mass or more of the active material layer binder with respect to the total mass of the active material layer binders, It is necessary to satisfy the above first HSP distance relationship. The organic solvent is preferably 50% by mass or more, more preferably 70% by mass to 100% by mass, based on the total mass of the active material layer binder in the active material layer, Satisfy the first HSP distance above. Furthermore, it is preferable to satisfy the first HSP distance relationship for all types of active material layer binders in the active material layer. Thereby, swelling of the active material layer can be more reliably prevented.

In addition, the distance between the Hansen solubility parameter of the active material of the active material layer and the Hansen solubility parameter of the organic solvent (hereinafter also referred to as “second HSP distance”) is 5.0 (MPa) ^1/2 or more Is preferred.

  The active material in the active material layer is mainly bound by the active material layer binder, but on the other hand, the frictional force between the active materials also maintains the balance of the residual stress in the active material layer, and thus, It can contribute to the maintenance of the layer thickness.

  When the second HSP distance satisfies the above relationship between the active material and the organic solvent, the interaction with the surface of the active material, the permeation of the active material and the binder to the adhesion interface, and the internal void Permeation of organic solvents is suppressed.

  As a result, the frictional force between the active materials is reduced, and the separation of the interface between the active material and the binder is suppressed, and the increase in the layer thickness of the active material layer is further reduced.

Further, the upper limit of the above-mentioned second HSP distance is not particularly limited, but in a general solvent except water, it falls within the value of 20 (MPa) ^1/2 or less. The second HSP distance is more preferably 8.0 or more, which further suppresses the increase in the layer thickness of the active material layer.

  The second HSP distance is calculated in the same manner as the first HSP distance described above except that the Hansen solubility parameter of the active material layer binder is replaced with the Hansen solubility parameter of the active material. In addition, even when a plurality of organic solvents are mixed in the composition for forming a porous insulating layer, the first HSP except that the Hansen solubility parameter of the active material layer binder is replaced with the Hansen solubility parameter of the active material. Similar to the distance, the second HSP distance can be calculated.

  When a plurality of active materials are contained in the active material layer, the organic solvent is preferably 45% by mass or more, more preferably 50% by mass or more, still more preferably 70% by mass, based on the total mass of the active material. More than 100% by mass or less of the active material and the above-mentioned second HSP distance are satisfied. Furthermore, it is preferable to satisfy the above-mentioned second HSP distance relationship for all types of active materials in the active material layer. Thereby, swelling of the active material layer can be more reliably prevented.

  The HSPs of various solvents can be used as a database on software such as Hansen Solubility Parameter in Practice 4th Edition, for example.

  The HSP of the active material layer binder is determined as follows. The active material layer binder (dried solid state) is immersed in a solvent of which HSP is known, and the degree of weight swelling to each solvent is measured. As the solvent used here, dimethylsulfoxide, acetonitrile, dimethylformamide, methanol, ethanol, 1-butanol, 1,4-dioxane, tetrahydrofuran, toluene, methyl ethyl ketone, acetone, N-methyl-2-pyrrolidone, n-hexane , Cyclohexane, methyl isobutyl ketone, n-butyl acetate, chloroform, methyl acetate, pyridine, hexafluoroisopropanol, diethylene glycol, γ-butyrolactone, 2-aminoethanol, cyclohexanone, 1,1,2,2-tetrabromoethane, 1- A plurality of hydrophilic solvents and hydrophobic solvents are widely selected, such as bromonaphthalene and aniline. For each solvent, a solvent having a degree of swelling of 3.0 or more by weight is classified as a "swelling solvent" and a solvent less than 3.0 is classified as a "non-swelling solvent". For each point of the solvent used in the test placed on the HSP three-dimensional space, include the points of the solvent classified as "Swelling solvent" and the points of the solvent classified as "Non-swelling solvent" are included Not calculate the sphere. The center coordinates of the sphere when the radius of the sphere is maximized is taken as the HSP of the active material layer binder. If it is difficult to experimentally determine the HSP of the active material layer binder, HSP may be obtained based on literature values.

The active material HSP may be determined experimentally, but in difficult cases, HSP may be obtained based on literature values. In addition, when it is difficult to obtain literature values for HSP of a specific active material, literature values for a compound corresponding to the active material can be substituted. For example, HSP may be obtained based on literature values for graphene described in Langmuir 2008; 24; 10560-4. According to the document, the dispersion term δ _{D of} graphene is 18.0 (MPa) ^1/2 , the polar term δ _{P of} graphene is 9.3 (MPa) ^1/2 , and the hydrogen bonding term δ _H of graphene is 7. It is 7 (MPa) ^1/2 . Therefore, in the organic solvent, the HSP distance Ra shown in the following formula (I) is preferably 5.0 (MPa) ^1/2 or more, more preferably 8.0 (MPa) ^1/2 or more. This further reduces the increase in the layer thickness of the active material layer.

In formula (I), _{δD (solvent)} indicates the dispersion term of the organic solvent, _{δP (solvent)} indicates the polar term of the organic solvent, and _{δH (solvent)} indicates the hydrogen bonding term of the organic solvent.

  Such organic solvents are not particularly limited as long as they satisfy the above-mentioned HSP relationship, in particular the first HSP distance relationship, and various known organic solvents such as glycol alkyl ether compounds and alcohol compounds Can be used. These organic solvents can easily satisfy the relationship between the general binder of the active material layer and the above first HSP distance, and the dispersibility of the insulating inorganic particles and the dissolution of the porous insulating layer binder described later It is preferably used from the viewpoint of sex. In particular, an alcohol compound is preferable from the viewpoint of simultaneously increasing the first HSP distance and the second HSP distance. In addition, an organic solvent may be used individually by 1 type, and may mix and use 2 or more types.

  The alcohol-based compound has, for example, 3 or more and 10 or less, preferably 4 or more and 8 or less carbon atoms, and includes unsubstituted or alkoxy-substituted linear or branched lower alkyl alcohol or aliphatic alcohol. Specifically as such alcohol compounds, 2-propanol, 1-butanol, 1-pentanol, 1-hexanol, 1-heptanol, 1-octanol, 2-methyl-1-pentanol, 2- Ethyl-1-pentanol, 2-methyl-1-hexanol, 2-ethyl-1-hexanol, 2-methyl-1-heptanol, 2-ethyl-1-heptanol, 2-propyl-1-heptanol, 1-methoxy -2-propanol, 3-methoxy-3-methyl-1-butanol, 3-ethoxy-3-methyl-1-butanol, 3-methoxy-3-methyl-1-pentanol, 3-ethoxy-3-methyl- 1-pentanol, 1-nonanol, 1-decanol etc. are mentioned. When the alcohol-based compound is substituted by an alkoxy group, the carbon number of the alkoxy group is not particularly limited, and is, for example, 1 to 4, preferably 1 to 3, and more preferably 1 or 2.

  The alcohol compound may be a monohydric alcohol or a polyhydric alcohol. However, the alcohol compound is preferably a monohydric alcohol. This further suppresses the increase in the layer thickness of the active material layer.

  Among the above, preferred alcohol compounds are 1-butanol, 1-hexanol, 2-ethyl-1-hexanol, and 3-methoxy-3-methyl-1-butanol. Particularly preferred alcohol compounds are 2-ethyl-1-hexanol and 3-methoxy-3-methyl-1-butanol.

  Examples of glycol alkyl ether compounds include monoalkylene glycol monoalkyl ethers such as ethylene glycol mono methyl ether, ethylene glycol mono ethyl ether, etc., diethylene glycol mono methyl ether diethylene glycol Dialkylene glycol monoalkyl ether such as monoethyl ether (diethylene glycol monoethyl ether), triethylene glycol monomethyl ether (triethylene glycol monomethyl) ther) and tri alkylene glycol monoalkyl ethers and triethylene glycol monoethyl ether (triethylene glycol monoethyl ether), and other polymerization degree include 3 or more alkylene glycol monoalkyl ethers. The carbon number of the alkoxy group in the glycol alkyl ether compound is not particularly limited, and is, for example, 1 to 4, preferably 1 to 3, and more preferably 1 or 2.

  Moreover, it is preferable that a glycol alkyl ether type compound has ethylene glycol frame | skeleton. Particularly preferred glycol alkyl ether compounds are triethylene glycol monomethyl ether, diethylene glycol monomethyl ether, and ethylene glycol monoethyl ether.

  The boiling point of the organic solvent is preferably 100 ° C. or more, more preferably 130 ° C. or more and 250 ° C. or less. This prevents evaporation of the solvent at the time of formation of the porous insulating layer and the accompanying change in viscosity, and a porous insulating layer with a uniform thickness can be formed.

  The solvent may also contain water. While water is excellent in the solubility of the active material layer binder in the active agent layer, it is suitable for dissolution and dispersion of each material of the composition for forming a porous insulating layer. The content of water in the solvent is, for example, 70% by mass or less, preferably 50% by mass or less, based on the solvent.

  The content of the solvent in the composition for forming a porous insulating layer is not particularly limited, and can be appropriately selected depending on the production conditions, but for example, 15% by mass or more and 60% by mass or less, preferably 20% by mass or more It is 45 mass% or less.

(1.2 Insulating inorganic particles)
In addition, the composition for forming a porous insulating layer contains insulating inorganic particles. The insulating inorganic particle is a main component in the solid content of the composition for forming a porous insulating layer. The insulating inorganic particles secure the insulation between the separator and the active material layer, and prevent unintended internal short circuit.

Such insulating inorganic particles are not particularly limited, and examples thereof include iron oxide, silica (SiO ₂ ), alumina (Al ₂ O ₃ ), oxide particles such as TiO ₂ , BaTiO ₂ , and ZrO, boron nitride, and the like. Aluminum nitride, silicon nitride or other nitride particles, calcium fluoride, barium fluoride, barium sulfate or other sparingly soluble ion crystal particles, silicon, diamond or other covalently bonded crystal particles, montmorillonite or other clay particles, boehmite, zeolite Materials derived from mineral resources such as apatite, kaolin, mullite, spinel, olivine and the like, or artificial products thereof.

In addition, the surface of conductive particles such as metal particles, oxide particles such as SnO ₂ and tin-indium oxide (ITO), carbon particles such as carbon black and graphite is surface-treated with a material having electrical insulation. Therefore, fine particles having electrical insulation may be used.

The average particle size of the insulating inorganic particles is not particularly limited, but is, for example, 0.01 μm to 5 μm, preferably 0.1 μm to 1 μm. In the present specification, the average particle diameter indicates the volume-based frequency cumulative D50 particle diameter, and can be measured by a laser diffraction / scattering type particle size distribution measuring device.
Further, the content of the insulating inorganic particles in the composition for forming a porous insulating layer is, for example, 20% by mass or more and 98% by mass or less, preferably 30% by mass with respect to the solid content in the composition for forming a porous insulating layer. It is mass% or more and 95 mass% or less.

(1.3 Binder)
The composition for forming a porous insulating layer may contain a binder (porous insulating layer binder).

  The porous insulating layer binder is not particularly limited, and any known binder that can be used for the porous insulating layer can be used alone or in combination of two or more.

  Examples of such a binder include polymers or copolymers of vinyl group-containing monomers. The vinyl group-containing monomer is not particularly limited, and ethylene: acrylic acid, methacrylic acid and (meth) acrylic acid salt: acrylonitrile: vinyl alcohol: vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate: (meth 2.) Isobornyl acrylate, 2-ethylhexyl (meth) acrylate, (meth) acrylic esters such as methoxyethyl (meth) acrylate, styrene, etc. may be mentioned.

  The porous insulating layer binder may also contain a polymer X containing one or more monomer units (A) represented by the following formula (1).

In the formulae, each occurrence of R ¹ and R ² independently is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms,
Ring X is a heterocyclic group which has at least one nitrogen atom as a ring component, and at least one or more hydrogen atoms may be substituted by an alkyl group having 1 to 3 carbon atoms.

The polymer X containing such a monomer unit (A) is easily soluble in the above-mentioned solvent, particularly a glycol alkyl ether compound. Further, the elastic modulus of the polymer X is improved by the monomer unit (A), which is also advantageous for the formation of a strong porous insulating layer.
In the above ^{R 1} and ^{R 2,} the alkyl group having 1 to 3 carbon atoms, a methyl group, an ethyl group, n- propyl group, an isopropyl group. R ¹ and R ² are preferably each independently at each occurrence a hydrogen atom or a methyl group, more preferably a hydrogen atom.

Examples of the ring constituting the ring X include heterocyclic groups containing a nitrogen atom such as pyrazolyl group and pyrazolidinyl group, and heterocyclic groups containing a nitrogen atom such as morpholinyl group and an oxygen atom. Among these, the ring constituting the ring X is preferably a heterocyclic group containing a nitrogen atom and an oxygen atom, more preferably a morpholinyl group.
The number of members of the ring constituting the ring X is not particularly limited, and is, for example, 4 to 10, preferably 4 to 7.
In addition, one or more hydrogen atoms present in the ring constituting ring X are substituted by an alkyl group having 1 to 3 carbon atoms, more specifically, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, etc. It may be done. On the other hand, none of the hydrogen atoms present in the ring constituting the ring X may be substituted.

  Further, the content of the monomer unit (A) in the polymer X is not particularly limited, but is, for example, 20% by mass or more, preferably 40% by mass or more and 98% by mass or less. As a result, the polymer X is more easily dissolved in the above-mentioned solvent, particularly the glycol ether compound.

  The polymer X further contains either or both of a monomer unit (B) represented by the following formula (2) and a monomer unit (C) represented by the following formula (3) It may be. The monomer units (B) and the monomer units (C) can be contained in the polymer X singly or in combination of two or more.

In the formulae, each of R ^{3 to} R ⁷ independently represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.
L is a divalent linking group,
Y is a heterocyclic group having at least one oxygen atom as a ring component, and at least one or more hydrogen atoms may be substituted by an alkyl group having 1 to 3 carbon atoms.

  When the polymer contains one or more monomer units (B) represented by the above formula (2), the polymer X dissolves more easily in the glycol ether compound.

In R ³ and R ⁴ in Formula (2), examples of the alkyl group having 1 to 3 carbon atoms include a methyl group, an ethyl group, an n-propyl group and an isopropyl group. R ³ and R ⁴ are preferably each independently a hydrogen atom or a methyl group, and more preferably a hydrogen atom.

  L is a divalent linking group, and examples thereof include a single bond, an alkylene group having 1 to 5 carbon atoms, and a polyethylene glycol group. A methylene group, ethylene group, a propylene group, a butylene group, a propylene group etc. are mentioned as a C1-C5 alkylene group. The hydrogen atom which comprises a C1-C5 alkylene group may be substituted by a C1-C3 alkyl group, more specifically, a methyl group, an ethyl group, n-propyl group, isopropyl group etc. .

As a ring constituting Y, for example, an unsaturated heterocyclic group containing an oxygen atom such as furanyl group, pyranyl group, 2,5-dihydrofuranyl group, etc., tetrohydrofuranyl group, tetrohydropyranyl group, dioxane And a saturated heterocyclic group containing an oxygen atom such as -yl group, a heterocyclic group containing a nitrogen atom such as morpholinyl group and an oxygen atom, and the like. Among these, the ring constituting the ring X is preferably a saturated heterocyclic group containing an oxygen atom, more preferably a tetrohydrofuranyl group.
The number of members of the ring constituting Y is not particularly limited, and is, for example, 4 to 10, preferably 4 to 7.

  In addition, one or more hydrogen atoms present in the ring constituting Y are substituted by an alkyl group having 1 to 3 carbon atoms, more specifically, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, etc. May be On the other hand, none of the hydrogen atoms present in the ring constituting Y may be substituted.

  In the polymer X, the mass ratio (A) / (B) of the monomer unit (A) to the monomer unit (B) is preferably 50/50 to 100/0. Thereby, when the solvent contains a glycol ether compound, the polymer X can be more easily dissolved in the solvent.

  In particular, when the polymer X contains one or more monomer units (C), the dispersibility of the insulating inorganic particles and the binding property to the active material layer are improved. When the polymer X contains one or more monomer units (C), and the composition for forming the porous insulating layer contains polyolefin polymer particles, the polyolefin polymer particles are in a stable dispersed state in the composition. Makes it easier to maintain

In R ^{5 to} R ⁷ in the formula (3), examples of the alkyl group having 1 to 3 carbon atoms include a methyl group, an ethyl group, an n-propyl group and an isopropyl group. R ^{5 to} R ⁷ are preferably each independently a hydrogen atom or a methyl group, and more preferably a hydrogen atom.

  The mass ratio (A) / (C) of the monomer unit (A) to the monomer unit (C) is preferably 40/60 to 60/40. Thereby, the binding property of the binder and the dispersibility of the polyolefin-based polymer particles can be simultaneously improved.

  The polymer X may contain an ionic monomer unit, but when the composition for forming a porous insulating layer does not contain polyolefin polymer particles, the content of the ionic monomer unit is preferably The content is 0.5% by mass or more and 50% by mass or less, more preferably 2% by mass or more and 30% by mass or less. Thereby, the dispersibility of the insulating inorganic particles and the binding property to the active material layer are further improved. When the composition for forming a porous insulating layer contains polyolefin polymer particles, the content of the ionic monomer unit is preferably 2% by mass or more and 5% by mass or less. Thereby, the dispersion stability of the polyolefin polymer particles is well maintained. In addition, an ionic monomer unit means the monomer unit which has a functional group which can produce a positive or negative charge by ionization etc., for example in the solvent containing water.

  The ionic monomer unit is not particularly limited, and examples thereof include a monomer unit (D) represented by the following formula (4).

In the formula, R ^{8 to} R ⁹ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.
Z ⁺ is a monovalent cationic group,
Z ^<+> and O ^{< - >} in a formula may be couple | bonded by ionic bond.

In R ⁸ and R ⁹ in the formula (4), examples of the alkyl group having 1 to 3 carbon atoms include a methyl group, an ethyl group, an n-propyl group and an isopropyl group. R ⁸ and R ⁹ are preferably each independently a hydrogen atom or a methyl group, and more preferably a hydrogen atom.

Moreover, as Z ⁺ , for example, inorganic cations such as hydrogen ion, ammonium ion, organic cation, metal ion, and metal complex compounds such as metal complex can be mentioned.
As an organic cation, the cationization thing of amines is mentioned. Such amines may be any of primary, secondary and tertiary, and examples thereof include methylamine, dimethylamine, triethylamine, methylemine, dimethylemine, triethylamine, monoethanolamine and diethanolamine. Aliphatic amines such as triethanolamine, ethylene diamine amine, N, N-diisopropylethylamine, hexamethylene diamine, aromatic amines such as aniline, pyrrolidine, piperidine, piperazine, morpholine, pyridine, pyridazine, pyrimidine, pyrazine, oxazole, Non-aromatic heterocyclic amines such as thiazoles.

The polymer X may contain a monomer unit other than the above.
In addition, the content of the total of the monomer units (A), (B) and (C) is, for example, 50% by mass or more, preferably 70% by mass, based on the whole of the polymer X in mass ratio The content is more preferably 95% by mass or more.

There are no particular limitations on the bonding mode of the polymer, copolymer and polymer that can be contained in the porous insulating layer binder, and the polymer is a random copolymer, alternating copolymer, periodic copolymer, It may be a block copolymer or a graft copolymer.
The weight average molecular weight of the polymer, copolymer and polymer that may be contained in the porous insulating layer binder is not particularly limited, and is, for example, 50,000 or more and 2,000,000 or less, preferably 100,000 or more, 1 It is less than, 000,000. In addition, a weight average molecular weight can be measured by gel permeation chromatography which converts polyethylene oxide (PEO) as a standard substance.

  In addition, the content of the porous insulating layer binder in the composition for forming a porous insulating layer is preferably, for example, 2% by mass or more and 10% by mass or less with respect to the solid content in the composition for forming a porous insulating layer Is 3% by mass or more and 7% by mass or less.

(1.4 Polyolefin-based polymer particles)
In addition, the composition for forming a porous insulating layer may contain polyolefin-based polymer particles. Since the polyolefin polymer particles have a relatively low melting point, they melt and block the migration of lithium ions when the nonaqueous electrolyte secondary battery is abnormally heated. This further improves the safety performance of the non-aqueous electrolyte secondary battery.

  Examples of the polyolefin-based polymer particles include polyethylene-based polymer particles and polypropylene-based polymer particles.

  The average particle size of the polyolefin-based polymer particles is not particularly limited, but is, for example, 0.5 μm or more and 4 μm or less, preferably 0.7 μm or more and 2 μm or less. In general, the porous insulating layer is formed as a relatively thin (for example, 4 μm or less) thin film. Therefore, it is also required to relatively reduce the average particle size of the polyolefin-based polymer particles. Although the polyolefin polymer particles are relatively difficult to disperse when the particle size is small, the porous insulating layer can be obtained by using the above-described polymer containing the monomer units (A) and (B) as a binder. It can be dispersed uniformly in it.

  In addition, the content of the polyolefin-based polymer particles in the composition for forming a porous insulating layer is, for example, 20% by mass or more and 80% by mass or less based on the solid content in the composition for forming a porous insulating layer.

  In the composition for forming a porous insulating layer according to the present embodiment described above, the organic solvent having the Hansen solubility parameter of the binder of the active material layer and the Hansen solubility parameter having a distance of 8.0 or more is employed. . Therefore, even when the composition for forming a porous insulating layer is applied on the active material layer, the swelling of the active material layer is suppressed.

<2. Configuration of Nonaqueous Electrolyte Secondary Battery>
Hereinafter, the specific configuration of the non-aqueous electrolyte secondary battery 10 according to the above-described embodiment of the present invention will be described with reference to FIG. FIG. 1 is an explanatory view illustrating the configuration of a non-aqueous electrolyte secondary battery according to an embodiment of the present invention. Moreover, the non-aqueous electrolyte secondary battery 10 has the negative electrode 30 as an electrode for non-aqueous electrolyte secondary batteries which concerns on one Embodiment of this invention.

  The non-aqueous electrolyte secondary battery 10 shown in FIG. 1 is an example of a secondary battery according to the present embodiment. As shown in FIG. 1, the non-aqueous electrolyte secondary battery 10 includes a positive electrode 20, a negative electrode 30, and a separator layer 40. The form of the non-aqueous electrolyte secondary battery 10 is not particularly limited, but may be, for example, cylindrical, square, laminate, button or the like.

  The positive electrode 20 includes a current collector 21 and a positive electrode active material layer 22 disposed on the main surface of the current collector 21. The current collector 21 may be any conductor, and may be, for example, aluminum (Al), stainless steel, nickel-plated steel, or the like.

  In the present specification, the term "main surface" refers to a surface having a much larger area than other surfaces of a thin plate. For example, in the current collector 21, the main surface means the front and back surfaces of the foil-like current collector 21, and does not mean an end surface, a side surface, or the like.

  The positive electrode active material layer 22 contains at least a positive electrode active material and a binder (positive electrode active material layer binder), and may further contain a conductive agent. The content of the positive electrode active material, the conductive agent, and the binder is not particularly limited, and may be any content as long as it is applied to a conventional non-aqueous electrolyte secondary battery.

The positive electrode active material is, for example, a transition metal oxide or a solid solution oxide containing lithium, and is not particularly limited as long as it is a substance capable of electrochemically absorbing and desorbing lithium ions. The transition metal oxide containing lithium, Li · Co-based composite oxide such as _{LiCoO 2, LiNi x Co y Mn} z O Li · Ni · Co · Mn -based composite oxides such as _2, Li · such LiNiO ₂ Examples include Ni-based composite oxides, and Li / Mn-based composite oxides such as LiMn ₂ O ₄ . The solid solution _{oxide, Li a Mn x Co y Ni} z O 2 (1.150 ≦ a ≦ 1.430,0.45 ≦ x ≦ 0.6,0.10 ≦ y ≦ 0.15,0.20 Z z 0.2 0.28), LiMn _x Co _y Ni _z O ₂ (0.3 x x 0.8 0.85, 0.10 y y 0.3 0.3, 0.10 z z 0.3 0.3), LiMn _{1 .5} Ni _0.5 O ₄ etc. can be illustrated. The content (content ratio) of the positive electrode active material is not particularly limited, as long as the content is applicable to the positive electrode active material layer of the non-aqueous electrolyte secondary battery. Moreover, you may use these compounds individually or in mixture of multiple types.

  The conductive agent may be, for example, carbon black such as ketjen black or acetylene black, natural graphite, artificial graphite, carbon nanotubes, carbon nanotubes, graphene, carbon nanofibers And fibrous carbon such as carbon nanofibers, or a composite of these fibrous carbon and carbon black. However, the conductive agent can be used without particular limitation as long as it is for enhancing the conductivity of the positive electrode. The content of the conductive agent is not particularly limited, as long as the content is applicable to the positive electrode active material layer of the non-aqueous electrolyte secondary battery.

  The binder includes, for example, a fluorine-containing resin such as polyvinylidene fluoride, a styrene-containing resin such as styrene-butadiene rubber, and an ethylene-propylene-diene terpolymer. ), Acrylonitrile butadiene rubber (acrylonitrile-butadiene rubber), fluoro rubber (fluoroelastomer), polyvinyl acetate (polyvinyl acetate), polymethyl methacrylate (polymethyl methacrylate), polyethylene (polyethylene), polyvinyl alcohol (polyviny) alcohol), carboxymethylcellulose or derivatives thereof (such as carboxymethylcelluloses (eg, a salt of carboxymethylcellulose)) or nitrocellulose. However, as long as the binder can bind the positive electrode active material and the conductive agent onto the current collector 21 and has oxidation resistance and electrolytic solution stability that can withstand the high potential of the positive electrode, the binder is particularly preferable. It is not restricted. Further, the content of the binder is not particularly limited, as long as the content is applicable to the positive electrode active material layer of the non-aqueous electrolyte secondary battery.

  The positive electrode active material layer 22 is obtained, for example, by dispersing a positive electrode active material, a conductive agent, and a binder in a suitable organic solvent (eg, N-methyl-2-pyrrolidone). A positive electrode slurry (slurry) is formed, and the positive electrode slurry can be coated on the current collector 21, dried, and rolled. The density of the positive electrode active material layer 22 after rolling is not particularly limited, as long as the density is applicable to the positive electrode active material layer of the non-aqueous electrolyte secondary battery.

  The negative electrode 30 is an example of a negative electrode for a secondary battery according to the present embodiment. The negative electrode 30 has a foil-like current collector 31, a negative electrode active material layer 32 disposed in contact with the current collector 31, and a porous insulating layer 33 disposed on the negative electrode active material layer 32.

  The current collector 31 is not particularly limited, and can be made of, for example, copper, aluminum, iron, nickel, stainless steel or an alloy thereof, or a plated steel thereof, such as nickel plated steel. The current collector 31 is particularly preferably made of copper or nickel or an alloy thereof.

  The negative electrode active material layer 32 is disposed in contact with the current collector 31, more specifically, in such a manner that one main surface is adhered onto the current collector 31. The negative electrode active material layer 32 contains at least a negative electrode active material. In the present embodiment, the negative electrode active material layer 32 includes a negative electrode active material and a binder (negative electrode active material layer binder).

The negative electrode active material is not particularly limited as long as it is a substance capable of electrochemically absorbing and desorbing lithium ions, and examples thereof include graphite active materials (artificial graphite, natural graphite, a mixture of artificial graphite and natural graphite, Natural graphite coated with artificial graphite, etc.) Si-based active material or Sn-based active material (eg fine particles of silicon (Si) or tin (Sn) or their oxides, alloys based on silicon or tin), metals Examples thereof include lithium and titanium oxide compounds such as Li ₄ Ti ₅ O ₁₂ . As the negative electrode active material, one or more of the above can be used. The oxide of silicon is represented by SiO _x (0 ≦ x ≦ 2).

  The content of the negative electrode active material in the negative electrode active material layer 32 is not particularly limited, but is, for example, 60.0 to 100% by mass, preferably 80 to 99.5% by mass, and more preferably 90 to 99% by mass Can be.

  As the negative electrode active material layer binder, the same binder as that constituting the positive electrode active material layer 22 can be used. Among the above, it is preferable to include one or more binders selected from styrene-containing resins, fluorine-containing resins, polyethylene, polyvinyl alcohol, and carboxymethyl celluloses. In addition, as a styrene containing resin, a styrene butadiene rubber is preferable, and a polyvinylidene fluoride is preferable as a fluorine containing resin. Carboxymethylcelluloses include carboxymethylcellulose and carboxymethylcellulose derivatives such as carboxymethylcellulose salts. Examples of carboxymethylcellulose salts include salts of carboxymethylcellulose and alkali metal ions, more specifically sodium carboxymethylcellulose, potassium carboxymethylcellulose, and lithium carboxymethylcellulose.

  Further, the content of the binder for the negative electrode active material layer in the negative electrode active material layer 32 is not particularly limited, but is, for example, 0 to 40% by mass, preferably 0.5 to 20% by mass, more preferably 1 to It can be 10% by mass.

  For example, the negative electrode active material layer 32 disperses the negative electrode active material and the negative electrode active material layer binder described above in an appropriate solvent (for example, water etc.) to form a negative electrode slurry, and the negative electrode slurry is It can be formed by coating on top, drying and rolling. The thickness of the negative electrode active material layer 32 after rolling is not particularly limited, and may be any thickness that can be applied to the negative electrode active material layer of the lithium ion secondary battery. In addition, the negative electrode active material layer 32 may be formed so as to selectively contain a graphite active material.

  The negative electrode active material layer 32 is not limited to the method described above, and can be formed by physical vapor deposition such as thermal evaporation, ion plating, sputtering, or chemical vapor deposition (CVD).

  The porous insulating layer 33 is formed on the negative electrode active material layer 32 so as to be disposed between the negative electrode 30 and the separator layer 40. The porous insulating layer 33 prevents unintended internal short circuit in the non-aqueous electrolyte secondary battery 10. In the present embodiment, the porous insulating layer 33 is formed by applying and drying the above-described composition for forming a porous insulating layer. Therefore, the porous insulating layer contains, for example, insulating inorganic particles and a porous insulating layer binder, and further optionally contains polyolefin-based polymer particles. The structures of the insulating inorganic particles, the porous insulating layer binder, and the polyolefin polymer particles are as described above.

The separator layer 40 usually includes a separator and an electrolytic solution. The separator is not particularly limited, and any separator may be used without particular limitation as long as it can be used as a lithium ion secondary battery separator. As a separator, it is preferable to use the porous film, the nonwoven fabric, etc. which show the outstanding high rate discharge performance individually or in combination. The separator may be coated with an inorganic substance such as Al ₂ O ₃ , Mg (OH) ₂ , SiO ₂ or the like, and may contain the above-mentioned inorganic substance as a filler.

  As a material which constitutes such a separator, for example, polyolefin resin represented by polyethylene (polyethylene), polypropylene (polypropylene), etc., polyethylene terephthalate (polyethylene terephthalate), polybutylene terephthalate (polybuthylene terephthalate) etc. Representative polyester resins, polyvinylidene difluoride, vinylidene difluoride-hexafluoropropylene copolymer, vinylidene fluoride (Vinylidene difluoride-perfluorovinylether copolymer), vinylidene difluoride-tetrafluoroethylene copolymer (vinylidene difluoride-tetrafluoroethylene copolymer), vinylidene difluoride-trifluoroethylene copolymer (vinylidene difluoride-trifluoroethylene copolymer) ), Vinylidene fluoride-fluoroethylene copolymer (vinylidene difluoride-fluoroethylene copolymer), vinylidene fluoride-hexafluoroacetone copolymer (vinylidene difl) oride-hexafluoroacetone copolymer, vinylidene difluoride-ethylene copolymer, vinylidene difluoride-propylene copolymer, vinylidene fluoride-trifluoropropylene copolymer (vinylidene) difluoride-trifluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer (vinylidene difluoride-tetrafluoroethylene-hexafluoropropylene c) Polymer), vinylidene fluoride - ethylene - tetrafluoroethylene copolymer (vinylidene difluoride-ethylene-tetrafluoroethylene copolymer) and the like can be used. In addition, the porosity in particular of a separator is not restrict | limited, It is possible to apply the porosity which the separator of the conventional lithium ion secondary battery has arbitrarily.

  The electrolytic solution contains an electrolyte salt and a solvent.

The electrolyte salt is an electrolyte such as a lithium salt. The electrolyte salt, for _{example, LiClO 4, LiBF 4, LiAsF} 6, LiPF 6, LiSCN, LiBr, LiI, Li 2 SO 4, Li 2 B 10 Cl 10, NaClO 4, NaI, NaSCN, NaBr, KClO4, such as KSCN Inorganic ionic salt containing one of lithium (Li), sodium (Na) or potassium (K), LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN ( CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), LiC (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO ₂ ) ₃ , (CH ₃ ) ₄ NBF ₄ , (CH ₃ ) ₄ NBr, ( C ₂ H ₅ ) ₄ NClO ₄ , (C ₂ H ₅ ) ₄ NI, (C ₃ H ₇ ) ₄ NBr, (n-C ₄ H ₉ ) ₄ NClO ₄ , (n —C ₄ H ₉ ) ₄ NI, (C ₂ H ₅ ) ₄ N-maleate, (C ₂ H ₅ ) ₄ N-benzoate, (C ₂ H ₅ ) ₄ N-phtalate, lithium stearyl sulfonate And organic ion salts such as lithium octyl sulfonate, lithium dodecylbenzene sulfonate, and the like can be used. In addition, these electrolyte salts may be used individually or in mixture of 2 or more types. Further, the concentration of the electrolyte salt is not particularly limited, but for example, a concentration of about 0.5 to 2.0 mol / L can be used.

  The solvent is a non-aqueous solvent that dissolves the electrolyte salt. The solvent is, for example, cyclic carbonates such as propylene carbonate, ethylene carbonate, buthylene carbonate, chloroethylene carbonate, vinylene carbonate, etc., γ-butyrolactone Cyclic esters such as (γ-butyrolactone), γ-valerolactone (γ-valerolactone), dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate (ethyl methyl ca) linear carbonates such as carbonate, methyl formate, methyl acetate, linear esters such as methyl butyrate, tetrahydrofuran or derivatives thereof, 1,3-dioxane 1,3-dioxane), 1,4-dioxane (1,4-dioxane), 1,2-dimethoxyethane (1,2-dimethoxyethane), 1,4-dibutoxyethane (1,4-dibutoxyethane), or Ethers such as methyl diglyme (methyldiglyme), nitriles such as acetonitrile (acetonitrile), benzonitrile (benzonitrile), dioxola (Dioxolane) or a derivative thereof, ethylene sulfide (ethylene sulfide), sulfolane (Sulfolane), sultone (sultone) or its derivatives, can be used alone or by their mixture of two or more. When two or more solvents are mixed and used, the mixing ratio of each solvent may be the mixing ratio used in a conventional lithium ion secondary battery.

  In addition, various additives, such as a negative electrode SEI (Solid Electrolyte Interface) forming agent and surfactant, may be added to the electrolytic solution.

  Such additives include, for example, succinic anhydride, lithium bis (oxalate) borate, lithium tetrafluoroborate, dinitrile compound, propane It is possible to use sultone (propane sultone), butane sultone (propane sultone), propene sultone, 3-sulfolene (3-sulfolene), fluorinated arylether, fluorinated acrylate or the like it can. Moreover, as content concentration of such an additive, content concentration of the additive in a general lithium ion secondary battery can be used.

  The nonaqueous electrolyte secondary battery 10 according to the present embodiment described above uses the composition for forming a porous insulating layer according to the present embodiment for forming the porous insulating layer 33 at the time of manufacturing the negative electrode 30. Therefore, the increase in the layer thickness of the negative electrode active material layer 32 is suppressed.

  In the above description, although the negative electrode 30 has been described as including the porous insulating layer 33, the present invention is not limited to the illustrated embodiment. For example, the positive electrode 20 may include a porous insulating layer. Also in this case, the increase in the layer thickness of the positive electrode active material layer 22 of the positive electrode 20 is suppressed. Further, in this case, the negative electrode 30 may not have the porous insulating layer.

<2. Method of Manufacturing Nonaqueous Electrolyte Secondary Battery>
Subsequently, a method of manufacturing the non-aqueous electrolyte secondary battery 10 will be described. In the method of manufacturing the non-aqueous electrolyte secondary battery 10 according to the present embodiment, a porous insulating layer is formed on the active material layer disposed on the main surface of the current collector using the composition for forming a porous insulating layer. Having a forming step. However, the method of manufacturing the non-aqueous electrolyte secondary battery 10 is not limited to the following method, and any manufacturing method can be applied.

  The positive electrode 20 is manufactured as follows. First, a mixture of a positive electrode active material, a conductive agent, and a positive electrode active material layer binder in a desired ratio is dispersed in an organic solvent (for example, N-methyl-2-pyrrolidone) to form a positive electrode slurry. Next, the positive electrode slurry is formed (for example, coated) on the current collector 21 and dried to form the positive electrode active material layer 22.

  Although the method of coating is not particularly limited, for example, a knife coater method, a gravure coater method or the like may be used. The following coating processes are also performed by the same method.

  Furthermore, the positive electrode active material layer 22 is compressed to a desired thickness by a compressor. Thereby, the positive electrode 20 is manufactured. Here, the thickness of the positive electrode active material layer 22 is not particularly limited as long as it is the thickness of the positive electrode active material layer of the conventional non-aqueous electrolyte secondary battery.

  The negative electrode 30 is also manufactured in the same manner as the positive electrode 20. First, a mixture of a negative electrode active material and a negative electrode active material layer binder in a desired ratio is dispersed in a solvent (eg, water) to form a negative electrode slurry. A graphite active material may be selectively mixed in the negative electrode slurry.

  Next, the negative electrode slurry is formed (for example, coated) on the current collector 31 and dried to form the negative electrode active material layer 32. Furthermore, the negative electrode active material layer 32 is compressed to a desired thickness by a compressor. Here, the thickness of the negative electrode active material layer 32 is not particularly limited, as long as it is the thickness of the negative electrode active material layer of the conventional non-aqueous electrolyte secondary battery.

  Thereafter, the porous insulating layer 33 is formed by the composition for forming the porous insulating layer. Specifically, the porous insulating layer 33 is formed by applying the composition for forming a porous insulating layer on the negative electrode active material layer 32 and drying it. Thereby, the negative electrode 30 is manufactured.

  In addition, when the composition for porous insulation layer formation is coated by forming the porous insulation layer 33 using the composition for porous insulation layer formation which concerns on this embodiment, the negative electrode active material layer 32 is formed. Swelling is suppressed. As a result, an increase in the thickness of the negative electrode 30 is prevented.

  Subsequently, the separator 40 is sandwiched between the positive electrode 20 and the negative electrode 30 to manufacture an electrode structure. Next, the manufactured electrode structure is processed into a desired form (for example, cylindrical, square, laminate, button, etc.), and inserted into a container of the form. Furthermore, the pores in the separator 40 are impregnated with the electrolytic solution by injecting a desired electrolytic solution into the container. Thereby, the non-aqueous electrolyte secondary battery 10 is manufactured.

  In the above description, the porous insulating layer 33 is formed on the negative electrode active material layer 32, but the present invention is not limited to the embodiment described above. For example, a porous insulating layer may be formed on the positive electrode active material layer 22 using a composition for forming a porous insulating layer. In this case, the porous insulating layer may not be formed on the negative electrode active material layer 32.

  Hereinafter, the present invention will be described in more detail based on specific examples. However, the following embodiments are merely examples of the present invention, and the present invention is not limited to the following embodiments.

(Synthesis of binder for porous insulating layer)
<Synthesis of Binder 1>
After charging 70.6 mg of azoisobutyronitrile, 10.0 g of N-vinylformamide, 9.5 g of acroyl morpholine, and 0.5 g of acrylic acid in a 500 ml flask equipped with a stirrer and a thermometer , 180.0 g of triethylene glycol monomethyl ether and 0.424 g of ethanolamine were sequentially added. The inside of the system was replaced with nitrogen, and the temperature inside the system was raised to 65 ° C. and reacted for 12 hours while stirring at 600 rpm. It was 9.7 mass% (conversion rate 96%) when the non volatile matter of the solution after reaction was measured. Thereafter, the initiator residue and the unreacted monomer were removed from the solution after reaction by heating under reduced pressure. The solution was cooled to room temperature and then adjusted to pH 8 by adding ethanolamine to obtain a copolymer solution. The solids content was 10%.

<Synthesis of Binder 2>
A 10% copolymer solution was obtained in the same manner as in the synthesis of the binder 1, except that the solvent was changed from triethylene glycol monomethyl ether to diethylene glycol monomethyl ether.

<Synthesis of Binder 3>
In the synthesis of binder 1, the composition in the reaction system was changed. That is, in the synthesis of binder 1, 8.0 g of N-vinylformamide, 11.0 g of acroyl morpholine and 1.0 g of acrylic acid are charged and stirred, then 180.0 g of triethylene glycol monomethyl ether and ethanolamine A 10% copolymer solution was obtained in the same manner except that 848 g was sequentially added.

<Synthesis of Binder 4>
In the synthesis of binder 1, the composition in the reaction system was changed. That is, in the synthesis of binder 1, 10.0 g of N-vinylformamide, 4.9 g of acroyl morpholine, 0.5 g of acrylic acid, and 4.6 g of tetrahydrofuranyl acrylate are stirred and then diethylene glycol monomethyl ether is added. An aqueous copolymer solution was obtained in the same manner except that 180.0 g and 0.424 g of ethanolamine were sequentially added.

<Synthesis of Binder 5>
In the synthesis of binder 1, the composition in the reaction system was changed. That is, in the synthesis of binder 1, 14.0 g of acroyl morpholine and 6.0 g of acrylic acid were charged and stirred, and then 180.0 g of diethylene glycol monomethyl ether and 5.088 g of ethanolamine were sequentially added. Thus, an aqueous copolymer solution was obtained.

<Synthesis of Binding Agent 6>
In the synthesis of binder 1, the composition in the reaction system was changed. That is, in the synthesis of binder 1, 19.0 g of acroyl morpholine and 1.0 g of acrylic acid were charged and stirred, and then 180.0 g of diethylene glycol monomethyl ether and 0.848 g of ethanolamine were sequentially added. Thus, an aqueous copolymer solution was obtained.

<Synthesis of Binder 8>
In a 500 ml flask equipped with a stirrer and a thermometer, 12.0 g of 2-ethylhexyl acrylate, 22.0 g of isobornyl acrylate, 4.0 g of acrylonitrile, 2.0 g of methacrylic acid, 0.8 g of sodium dodecylbenzene sulfonate and After charging 115 g of ion exchanged water and stirring, the inside of the system was replaced with nitrogen, and the temperature inside the system was raised to 70 ° C. while stirring at 600 rpm. After the temperature in the system reached 70 ° C., an aqueous solution in which 0.27 g of potassium persulfate was dissolved in 5.0 g of ion exchanged water was added and reacted for 12 hours. It was 25.0 mass% (conversion rate 100%) when the non volatile matter (solid content) of the aqueous dispersion liquid after reaction was measured. Thereafter, 200 ml of ethanol was added to a solution in which the reaction solution was concentrated to a nonvolatile content of 40% by mass by heating under reduced pressure to precipitate a solid. The solid was recovered, washed twice with 100 ml of ethanol and dried under reduced pressure at 80 ° C. for 10 hours, and then 460 g of 2-ethylhexanol was added and stirred at room temperature to obtain a copolymer solution. The solids content was 8%.

<Synthesis of Binder 9>
A copolymer solution was obtained in the same manner as in binder 5 except that 3-methoxy-3-methyl-1-butanol was used instead of diethylene glycol monomethyl ether.

(Production of electrode)
Artificial graphite (wheat granules, specific surface area 1.7 m ² / g, average particle diameter 15 μm), carboxymethyl cellulose sodium salt, styrene butadiene aqueous dispersion, the mass ratio of solid content 97.5: 1.0: 1. The negative electrode mixture slurry was produced by dissolving and dispersing in water solvent at 5. Next, this negative electrode mixture slurry was coated on both sides of a 10 μm thick copper foil current collector, dried, and rolled by a roll press to produce a negative electrode having a negative electrode active material layer on the copper foil current collector. The electrode coating amount was 26 mg / cm ² (both sides converted), and the electrode density was 1.65 g / cm ³ . Here, the binder in the negative electrode active material layer is styrene butadiene rubber and carboxymethyl cellulose.

(Preparation of a composition for forming a porous insulating layer)
Example 1
A mixed solvent solution of triethylene glycol monomethyl ether and ion-exchanged water in a mass ratio of 1: 1 is added to binder 1 with the same amount of ion-exchanged water as triethylene glycol monomethyl ether contained in the binder 1. Prepared (solid content 5.3%). This mixed solvent solution and boehmite particles having an average particle diameter (D50) of 0.9 μm were mixed so as to be 5:45 in solid content mass ratio, and dispersed by a bead mill to obtain a dispersion (solid content 35 .7%). Moreover, polyethylene is obtained by gradually adding, with stirring, triethylene glycol monomethyl ether in the same amount as the water contained in the aqueous dispersion to an aqueous dispersion of polyethylene wax (average particle diameter: 1 μm, solid content: 40%) A mixed solvent dispersion of wax was prepared (25.0% solids). A mixed solvent dispersion of this dispersion and a polyethylene wax was mixed at a weight ratio of 28: 36, and the composition for forming a porous insulating layer was produced by stirring with a rotation revolution mixer (final solid content 30% ).

  The composition for forming a porous insulating layer was coated on both surfaces of the negative electrode active material layer (active material layer) of the negative electrode using a wire bar so that the thickness after drying was 3 μm per side. Drying was carried out at 60 ° C. for 15 minutes in an oven. The thickness of the negative electrode active material layer of the obtained porous insulating layer-forming negative electrode was measured, and the amount of increase in the film thickness per one side was calculated as compared with the film thickness before forming the porous insulating layer. The thickness measurement of the negative electrode active material layer and the porous insulating layer was carried out by performing scanning electron microscope (SEM) observation after cross-sectioning processing of the electrode with a cryocross section polisher, and calculated as an average value of thickness measurement in 10 views. .

  Further, Table 1 shows the distance between triethylene glycol monomethyl ether and HSP of the binder for the negative electrode active material layer, the boiling point of triethylene glycol monomethyl ether, and the change in thickness of the negative electrode active material layer (active material layer). The HSP of triethylene glycol monomethyl ether was taken from Hansen Solubility Parameter in Practice 4th Edition. In addition, HSP of the negative electrode active material layer binder was experimentally obtained by the method described above using a solvent with known HSP. The same applies to the solvent and the negative electrode active material layer binder of other examples and comparative examples. As HSP of a negative electrode active material (graphite), HSP about the graphene as described in Langmuir2008; 24; 10560-4 was used.

(Example 2)
Composition for forming a porous insulating layer in the same manner as in Example 1 except that the binder 1 was changed to the binder 2 in Example 1, and diethylene glycol monomethyl ether was used instead of triethylene glycol monomethyl ether. Were coated and applied to the negative electrode. The results are shown in Table 1.

(Example 3)
The binder 3 and boehmite particles having an average particle diameter (D50) of 0.9 μm are mixed so as to be 5:95 in solid content mass ratio, and triethylene glycol monomethyl ether is added to make solid content 30%. I adjusted it. Thereafter, the composition for forming a porous insulating layer (solvent: triethylene glycol monomethyl ether) was produced by dispersing using a bead mill. Thereafter, it was applied to the negative electrode in the same manner as in Example 1. The results are shown in Table 1.

(Example 4)
The binder 4 and boehmite particles having an average particle diameter (D50) of 0.9 μm are mixed so as to be 5:95 in solid content mass ratio, and diethylene glycol monomethyl ether is added so that the solid content becomes 30%. It was adjusted. Thereafter, the composition for forming a porous insulating layer (solvent: diethylene glycol monomethyl ether) was produced by dispersing using a bead mill. Thereafter, it was applied to the negative electrode in the same manner as in Example 1. The results are shown in Table 1.

(Example 5)
The binder 5 and boehmite particles having an average particle diameter (D50) of 0.9 μm are mixed so as to be 5:95 in solid content mass ratio, and diethylene glycol monomethyl ether is added so that the solid content becomes 30%. It was adjusted. Thereafter, the composition for forming a porous insulating layer (solvent: diethylene glycol monomethyl ether) was produced by dispersing using a bead mill. Thereafter, it was applied to the negative electrode in the same manner as in Example 1. The results are shown in Table 1.

(Example 6)
The binder 6 and boehmite particles having an average particle diameter (D50) of 0.9 μm are mixed so as to be 5:95 in solid content mass ratio, and 2-ethoxyethanol (ethylene glycol monoethyl ether) is added. The solid content was adjusted to 30%. Thereafter, the composition for forming a porous insulating layer (solvent: 2-ethoxyethanol) was produced by dispersing using a bead mill. Thereafter, it was applied to the negative electrode in the same manner as in Example 1. The results are shown in Table 1.

(Example 7)
A vinyl butyral-vinyl alcohol-vinyl acetate copolymer (manufactured by Aldrich) having a weight molecular weight of 70,000 to 100,000 as binder 7 and boehmite particles having an average particle diameter (D50) of 0.9 μm are solidified. It mixed so that it might be set to 5:95 by mass ratio, and 1-butanol was added and it adjusted so that it might be 30% of solid content. Thereafter, the composition for forming a porous insulating layer (solvent: 1-butanol) was produced by dispersing using a bead mill. Thereafter, it was applied to the negative electrode in the same manner as in Example 1. The results are shown in Table 1.

(Example 8)
A composition for forming a porous insulating layer was prepared in the same manner as in Example 7 except that 3-methoxy-1-butanol was used in place of 1-butanol, and was applied to the negative electrode in the same manner as Example 1. did. The results are shown in Table 1.

(Example 9)
A composition for forming a porous insulating layer was prepared in the same manner as in Example 7 except that 2-ethyl-1-hexanol was used in place of 1-butanol, and was applied to the negative electrode in the same manner as Example 1. did. The results are shown in Table 1.

(Example 10)
The binder 8 and boehmite particles having an average particle diameter (D50) of 0.9 μm are mixed so as to be 5:95 in solid content mass ratio, and 2-ethyl-1-hexanol is added to make 30% solid content. Adjusted to be Then, the composition (solvent: 2-ethyl- 1-hexanol) for porous insulating layer formation was produced by making it disperse | distribute by bead mill. Thereafter, it was applied to the negative electrode in the same manner as in Example 1. The results are shown in Table 1.

(Example 11)
A composition for forming a porous insulating layer was prepared in the same manner as in Example 7 except that 1-hexanol was used in place of 1-butanol, and was applied to the negative electrode in the same manner as Example 1. The results are shown in Table 1.

(Example 12)
A composition for forming a porous insulating layer was prepared in the same manner as in Example 7 except that 3-methoxy-3-methyl-1-butanol was used in place of 1-butanol, and a negative electrode was prepared in the same manner as Example 1. It applied to the electrode. The results are shown in Table 1.

(Example 13)
Binder particle 9 and boehmite particles having an average particle diameter (D50) of 0.9 μm are mixed so as to be 5:95 in solid content mass ratio, and 3-methoxy-3-methyl-1-butanol is added to solidify it. It was adjusted to be 30% per minute. Thereafter, the composition for forming a porous insulating layer (solvent: 3-methoxy-3-methyl-1-butanol) was produced by dispersing with a bead mill. Thereafter, it was applied to the negative electrode in the same manner as in Example 1. The results are shown in Table 1.

(Example 14)
A composition for forming a porous insulating layer was prepared in the same manner as in Example 7 except that 1-heptanol was used in place of 1-butanol, and was applied to the negative electrode in the same manner as Example 1. The results are shown in Table 1.

(Example 15)
The binder 9 and boehmite particles having an average particle diameter (D50) of 0.9 μm are mixed so as to be 5:45 in solid content mass ratio, and 3-methoxy-3-methyl-1-butanol is added to solidify it. The dispersion was adjusted to be 45%, and then dispersed by a bead mill to prepare a dispersion of boehmite. In addition, an oxidized high density polyethylene wax is added to 3-methoxy-3-methyl-1-butanol so as to have a solid content of 15%, and after stirring with a homogenizer, the dispersion liquid of polyolefin particles is separately dispersed using a bead mill. Made. The dispersion of the boehmite and the dispersion of the polyethylene wax are mixed in a solid mass ratio of 50: 50 (binder 9: boehmite particles: oxidized high density polyethylene wax = 5: 45: 50), and planetata A composition for forming a porous insulating layer (solvent: 3-methoxy-3-methyl-1-butanol, solid content 22.5%) was produced by stirring with a Lee mixer. Thereafter, it was applied to the negative electrode in the same manner as in Example 1. The results are shown in Table 1.

(Example 16)
The binder 8 and boehmite particles having an average particle diameter (D50) of 0.9 μm are mixed so as to be 5:45 in solid content mass ratio, and 2-ethyl-1-hexanol is added to make the solid content 45%. The dispersion was adjusted to be as described above and dispersed by a bead mill to prepare a dispersion of boehmite. In addition, an oxidized high density polyethylene wax was added to 2-ethyl-1-hexanol so as to have a solid content of 15%, stirred by a homogenizer, and dispersed by a bead mill to separately prepare a dispersion of polyolefin particles. The dispersion of the boehmite and the dispersion of the polyethylene wax are mixed in a solid mass ratio of 50: 50 (binder 9: boehmite particles: oxidized high density polyethylene wax = 5: 45: 50), and planetata The composition for porous insulation layer formation (solvent: 2-ethyl 1-hexanol, solid content 22.5%) was produced by stirring with a Lee mixer. Thereafter, it was applied to the negative electrode in the same manner as in Example 1. The results are shown in Table 1.

(Comparative example 1)
Composition for forming a porous insulating layer having a solid content of 30% by changing to a solution of acrylic rubber in N-methyl-2-pyrrolidone (N-methylpyrrolidone) in place of binder 1 in Example 3 (solvent: NMP) was produced. Thereafter, it was applied to the negative electrode in the same manner as in Example 1. The results are shown in Table 1.

  In the table, “SBR” is styrene butadiene rubber, “CMC” is carboxymethylcellulose, “NVf” is N-vinylformamide, “ACMO” is acroyl morpholine, “AA” is acrylic acid, "MAA" is methacrylic acid, "THFA" is tetrahydrofuranyl acrylate, "2EHA" is 2-ethylhexyl acrylate (2-ethylhexyl acrylate), and "IBOA" is isobornyl acrylate (isobornyl acrylate) “VA” represents vinyl alcohol, “VB” represents vinyl butyrate (vinyl butyral), “VAc” represents vinyl acetate, and “AN” represents acrylonitrile.

  As shown in Table 1, when the porous insulating layer was formed using the composition for forming a porous insulating layer according to Examples 1 to 16, the composition for forming a porous insulating layer according to Comparative Example 1 was used. Compared to the case, the increase in the thickness of the active material layer was suppressed. In particular, when the composition for forming a porous insulating layer according to Examples 3 to 16 which does not contain water as a solvent is used, the effect of suppressing the increase in the thickness of the active material layer is large.

  Furthermore, in Examples 1-16, although HSP distance with an active material was 5.0 or more in all, for porous insulating layer formation which concerns on Examples 7-10 and 16 which were 8.0 or more When the porous insulating layer was formed using the composition, the increase in the thickness of the active material layer was further suppressed.

  Although the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to such examples. It is obvious that those skilled in the art to which the present invention belongs can conceive of various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also fall within the technical scope of the present invention.

10 non-aqueous electrolyte secondary battery 20 positive electrode 21 positive electrode current collector 22 positive electrode active material layer 30 negative electrode 31 negative electrode current collector 32 negative electrode active material layer 33 porous insulating layer 40 separator layer

Claims (13)

A composition for forming a porous insulating layer for forming a porous insulating layer on an active material layer disposed on a main surface of a current collector,
The active material layer contains at least an active material capable of electrochemically absorbing and desorbing lithium ions, and an active material layer binder.
The composition for forming a porous insulating layer contains at least a solvent containing an organic solvent, and insulating inorganic particles,
The composition for porous insulating layer formation whose distance of the Hansen solubility parameter of the said active material layer binder and the Hansen solubility parameter of the said organic solvent is 8.0 (MPa) ^1/2 or more. The composition for porous insulating layer formation of Claim 1 whose distance of the Hansen solubility parameter of the said active material and the Hansen solubility parameter of the said organic solvent is 5.0 (MPa) ^1/2 or more. The composition for porous insulation layer formation of Claim 1 or 2 whose distance of the Hansen solubility parameter of the said active material and the Hansen solubility parameter of the said organic solvent is 8.0 (MPa) ^1/2 or more. The composition for forming a porous insulating layer according to claim 1, wherein a distance Ra of a Hansen solubility parameter represented by the following formula (I) is 5.0 (MPa) ^1/2 or more as the organic solvent.

Wherein δ _{D (solvent)} (MPa) ^1/2 is the dispersion term of the organic solvent, δ _{P (solvent)} (MPa) ^1/2 is the polar term of the organic solvent, δ _{H (solvent)} ( MPa) ^1/2 represents a hydrogen bonding term of the organic solvent, respectively).   Furthermore, the composition for porous insulation layer formation as described in any one of Claims 1-4 containing a binder.   The composition for porous insulating layer formation as described in any one of Claims 1-5 in which the said solvent contains water.   The composition for porous insulating layer formation as described in any one of Claims 1-6 whose boiling point of the said organic solvent in 1 atm is 160 degreeC or more.   The composition for forming a porous insulating layer according to any one of claims 1 to 7, wherein the organic solvent contains an alcohol-based compound.   The composition for forming a porous insulating layer according to any one of claims 1 to 8, wherein the organic solvent contains a glycol alkyl ether compound.   Furthermore, the composition for porous insulation layer formation as described in any one of Claims 1-9 containing a polyolefin type polymer particle. Current collector,
An active material layer disposed on the main surface of the current collector;
A porous insulating layer formed on the active material layer by the composition for forming a porous insulating layer according to any one of claims 1 to 10,
The electrode for a non-aqueous electrolyte secondary battery, wherein the active material layer contains at least an active material capable of electrochemically absorbing and desorbing lithium ions and an active material layer binder.   A non-aqueous electrolyte secondary battery comprising the electrode for a non-aqueous electrolyte secondary battery according to claim 11. Forming a porous insulating layer on the active material layer disposed on the main surface of the current collector using the composition for forming a porous insulating layer,
The active material layer contains at least an active material capable of electrochemically absorbing and desorbing lithium ions and an active material layer binder,
The composition for forming a porous insulating layer contains at least a solvent containing an organic solvent and insulating inorganic particles,
The manufacturing method of the electrode for nonaqueous electrolyte secondary batteries whose distance of the Hansen solubility parameter of the said active material layer binder and the Hansen solubility parameter of the said organic solvent is 8.0 (MPa) ^1/2 or more.

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