JP2019029336A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

To provide a nonaqueous electrolyte secondary battery arranged so that the worsening of a battery performance accompanying charge and discharge can be suppressed.SOLUTION: A nonaqueous electrolyte secondary battery comprises: a nonaqueous electrolyte secondary battery separator of which the ion permeable barrier energy per unit film thickness is 300 J/mol/μm or more and 900 J/mol/μm or less; and a nonaqueous electrolyte solution including a predetermined additive agent of 0.5 ppm or more and 300 ppm or less.SELECTED DRAWING: None

Description

  The present invention relates to a non-aqueous electrolyte secondary battery.

  Non-aqueous electrolyte secondary batteries, especially lithium ion secondary batteries, are widely used as batteries for personal computers, mobile phones, personal digital assistants, etc. due to their high energy density, and recently developed as in-vehicle batteries. It has been.

  As a non-aqueous electrolyte secondary battery, for example, a non-aqueous electrolyte secondary battery including a porous film mainly composed of polyolefin as described in Patent Document 1 is known.

JP-A-11-130900

  In a non-aqueous electrolyte secondary battery including a separator for a non-aqueous electrolyte secondary battery made of a conventional porous membrane as disclosed in Patent Document 1, it is possible to improve a decrease in battery performance due to charge / discharge. It was sought after.

The present invention includes the inventions shown in the following [1] and [2].
[1] A separator for a nonaqueous electrolyte secondary battery having an ion permeation barrier energy per unit film thickness of 300 J / mol / μm or more and 900 J / mol / μm or less,
A non-aqueous electrolyte containing 0.5 ppm or more and 300 ppm or less of an additive having an ionic conductivity reduction rate L represented by the following formula (A) of 1.0% or more and 6.0% or less. Water electrolyte secondary battery.

L = (LA−LB) / LA (A)
(In Formula (A), LA is LiPF such that the concentration of LiPF ₆ is 1 mol / L in a mixed solvent containing ethylene carbonate / ethyl methyl carbonate / diethyl carbonate = 3/5/2 (volume ratio)). ₆ represents the ionic conductivity (mS / cm) of the reference electrolyte in which ₆ is dissolved,
LB represents the ionic conductivity (mS / cm) of the electrolytic solution obtained by dissolving 1.0% by weight of the additive in the reference electrolytic solution. )
[2] The nonaqueous electrolyte secondary battery according to [1], wherein the capacity retention rate after 100 cycles is 90% or more.

  According to one embodiment of the present invention, there is an effect that it is possible to suppress a decrease in battery characteristics associated with charging and discharging.

  An embodiment of the present invention will be described below, but the present invention is not limited to this. The present invention is not limited to each configuration described below, and various modifications are possible within the scope shown in the claims, and various technical means disclosed in different embodiments are appropriately combined. The obtained embodiments are also included in the technical scope of the present invention. Unless otherwise specified in this specification, “A to B” indicating a numerical range means “A or more and B or less”.

  A non-aqueous electrolyte secondary battery according to an embodiment of the present invention includes a non-aqueous electrolyte secondary battery separator described later and a non-aqueous electrolyte described later. The members constituting the nonaqueous electrolyte secondary battery according to one embodiment of the present invention will be described in detail below.

[Separator for non-aqueous electrolyte secondary battery]
The separator for a non-aqueous electrolyte secondary battery in one embodiment of the present invention has a large number of pores connected to the inside thereof, and allows gas or liquid to pass from one surface to the other surface. It has become. The separator for a non-aqueous electrolyte secondary battery in one embodiment of the present invention usually includes a polyolefin porous film, preferably a polyolefin porous film. Here, the “polyolefin porous film” is a porous film containing a polyolefin resin as a main component. Further, “based on a polyolefin-based resin” means that the proportion of the polyolefin-based resin in the porous film is 50% by volume or more of the entire material constituting the porous film, preferably 90% by volume or more, More preferably, it means 95% by volume or more. The polyolefin porous film can be a base material for a separator for a non-aqueous electrolyte secondary battery in an embodiment of the present invention.

More preferably, the polyolefin resin contains a high molecular weight component having a weight average molecular weight of 3 × 10 ⁵ to 15 × 10 ⁶ . In particular, when the polyolefin resin contains a high molecular weight component having a weight average molecular weight of 1,000,000 or more, the strength of the separator for a nonaqueous electrolyte secondary battery including the polyolefin porous film is more preferable.

  The polyolefin-based resin that is the main component of the polyolefin porous film is not particularly limited. For example, a single resin such as ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, which is a thermoplastic resin. A homopolymer obtained by polymerizing a monomer (for example, polyethylene, polypropylene, polybutene) or a copolymer (for example, ethylene-propylene copolymer) may be mentioned.

  The polyolefin porous film may be a layer containing these polyolefin resins alone or a layer containing two or more of these polyolefin resins. Among these, since it is possible to prevent an excessive current from flowing at a lower temperature (shutdown), it is preferable to include polyethylene, and it is more preferable to include high molecular weight polyethylene mainly composed of ethylene. In addition, a polyolefin porous film does not prevent containing components other than polyolefin in the range which does not impair the function of the said film.

Examples of the polyethylene include low density polyethylene, high density polyethylene, linear polyethylene (ethylene-α-olefin copolymer), ultrahigh molecular weight polyethylene having a weight average molecular weight of 1,000,000 or more, and of these, weight average molecular weight. Is more preferably 1 million or more, and more preferably a high molecular weight component having a weight average molecular weight of 5 × 10 ⁵ to 15 × 10 ⁶ is contained.

  Although the film thickness of the said polyolefin porous film is not specifically limited, It is preferable that it is 4-40 micrometers, and it is more preferable that it is 5-20 micrometers. If the film thickness of the said polyolefin porous film is 4 micrometers or more, it is preferable from a viewpoint that the internal short circuit of a battery can fully be prevented. On the other hand, if the film thickness of the said porous polyolefin film is 40 micrometers or less, it is preferable from a viewpoint that the enlargement of a nonaqueous electrolyte secondary battery can be prevented.

The weight per unit area of the polyolefin porous film is usually preferably 4 to 20 g / m ² so that the weight energy density and volume energy density of the battery can be increased, and preferably 5 to 12 g. / M ² is more preferable.

  The air permeability of the polyolefin porous film is preferably 30 to 500 sec / 100 mL, more preferably 50 to 300 sec / 100 mL in terms of Gurley value, from the viewpoint of exhibiting sufficient ion permeability.

  The porosity of the polyolefin porous film is 20% by volume to 80% by volume so as to increase the amount of electrolyte retained and to obtain a function of more reliably preventing (shutdown) an excessive current from flowing. It is preferable that it is 30 to 75% by volume.

  The pore diameter of the pores of the polyolefin porous film is preferably 0.3 μm or less from the viewpoint of sufficient ion permeability and prevention of entering of particles constituting the electrode, and is 0.14 μm or less. More preferably.

[Ion permeation barrier energy per unit thickness]
In the present invention, the ion permeation barrier energy per unit film thickness of the non-aqueous electrolyte secondary battery separator is determined by using the non-aqueous electrolyte secondary battery separator as a charge carrier during operation of the non-aqueous electrolyte secondary battery. This is a value obtained by dividing the activation energy (barrier energy) when a certain ion (for example, Li ⁺ ) passes by the film thickness of the separator for a non-aqueous electrolyte secondary battery. The ion permeation barrier energy per unit film thickness is an index indicating the ease of permeation of ions in the non-aqueous electrolyte secondary battery separator.

  When the ion permeation barrier energy per unit film thickness is small, it can be said that ions easily pass through the non-aqueous electrolyte secondary battery separator. That is, it can be said that the interaction between the resin wall inside the separator for the nonaqueous electrolyte secondary battery and the ions is weak. On the other hand, when the ion permeation barrier energy per unit film thickness is large, it can be said that ions are difficult to permeate through the separator for the non-aqueous electrolyte secondary battery. That is, it can be said that the interaction between the resin wall inside the nonaqueous electrolyte secondary battery separator and the ions is strong.

  When the ion permeation barrier energy per unit film thickness of the separator for a non-aqueous electrolyte secondary battery in one embodiment of the present invention is 300 J / mol / μm or more and 900 J / mol / μm or less, the non-aqueous electrolyte During the operation of the non-aqueous electrolyte secondary battery incorporating the secondary battery separator, the rate at which ions as charge carriers permeate the non-aqueous electrolyte secondary battery separator can be controlled to an appropriate speed.

  When the ion permeation barrier energy is excessively low and the above-described ions permeate the separator for the non-aqueous electrolyte secondary battery too quickly, the ions (positive electrode) may be ionized when the charge / discharge cycle is repeated. It is considered that the battery characteristics of the non-aqueous electrolyte secondary battery are deteriorated due to the depletion of the electrode and the deterioration of the electrode due to this.

  Therefore, when the ion permeation barrier energy per unit film thickness of the non-aqueous electrolyte secondary battery separator is 300 J / mol / μm or more, the electrode is prevented from deteriorating and the charge / discharge cycle is repeated. The battery characteristics can be improved. From such a viewpoint, the ion permeation barrier energy per unit film thickness of the separator for a nonaqueous electrolyte secondary battery is preferably 320 J / mol / μm or more, and more preferably 350 J / mol / μm or more.

  On the other hand, when the ion permeation barrier energy is excessively high and the above-described ion permeability is excessively low, it is applied to the separator for the non-aqueous electrolyte secondary battery when ions pass when the charge / discharge cycle is repeated. The stress increases, and as a result, the pore structure of the non-aqueous electrolyte secondary battery separator changes, so that the battery characteristics of the non-aqueous electrolyte secondary battery are considered to deteriorate.

  When the ion permeation barrier energy is excessively high, the polarity of the resin wall inside the nonaqueous electrolyte secondary battery separator may be excessively high. At that time, a non-aqueous electrolyte secondary battery, which is generated when the non-aqueous electrolyte secondary battery is operated, closes the gap of the separator for the non-aqueous electrolyte secondary battery. The battery characteristics of the electrolyte secondary battery may deteriorate.

  Therefore, from such a viewpoint, the ion permeation barrier energy per unit film thickness of the separator for a non-aqueous electrolyte secondary battery is preferably 800 J / mol / μm or less, more preferably 780 J / mol / μm or less. .

[Measurement method of ion permeation barrier energy per unit thickness]
The ion permeation barrier energy per unit film thickness of the separator for a nonaqueous electrolyte secondary battery in one embodiment of the present invention is calculated by the following method.

First, the separator for a non-aqueous electrolyte secondary battery is cut into a disk shape of φ17 mm, sandwiched between two SUS plates having a thickness of 0.5 mm and φ15.5 mm, and an electrolyte solution is injected to form a coin cell (CR2032 type). Make it. In the electrolyte, LiPF ₆ was mixed with a mixed solvent in which LiPF ₆ was mixed at a ratio of ethylene carbonate (EC) / ethyl methyl carbonate (EMC) / diethyl carbonate (DEC) = 3/5/2 (volume ratio). A solution in which the concentration of 1 is 1 mol / L is used.

Next, the produced coin cell is placed in a thermostat set to a predetermined temperature, which will be described later, and an AC impedance device (FRA 1255B) and a cell test system (1470E) manufactured by Solartron are used, with a frequency of 1 MHz to 0.1 Hz and an amplitude. A Nyquist plot is calculated at 10 mV, and the liquid resistance r _{0 of the} separator for the nonaqueous electrolyte secondary battery at each temperature is obtained from the value of the X intercept. The ion permeation barrier energy is calculated from the following formulas (1) and (2) using the obtained values. The temperature of the thermostat is set to 50 ° C, 25 ° C, 5 ° C, and -10 ° C.

  Here, the ion permeation barrier energy is expressed by the following formula (1).

k = 1 / r ₀ = Aexp (−Ea / RT) (1)
Ea: ion permeation barrier energy (J / mol)
k: Reaction constant r ₀ : Liquid resistance (Ω)
A: Frequency factor R: Gas constant = 8.314 J / mol / K
T: Temperature of constant temperature bath (K)
Taking the natural logarithm of both sides of Equation (1), the following Equation (2) is obtained. Based on the equation (2), ln (1 / r ₀ ) is plotted against the reciprocal of temperature (1 / T), and −Ea / R which is the slope of a straight line obtained from the plot by the least square method is Ea is calculated by multiplying the value of -Ea / R by the gas constant R. Thereafter, the calculated Ea is divided by the film thickness of the non-aqueous electrolyte secondary battery separator to calculate the ion permeation barrier energy per unit film thickness.

ln (k) = ln (1 / r ₀ ) = lnA−Ea / RT (2)
The frequency factor A is a unique value that does not vary with temperature change, and is determined by the form of ions passing through the inside of the non-aqueous electrolyte secondary battery separator, the amount of charge, the size, and the like. The frequency factor A is a value of ln (1 / r ₀ ) when (1 / T) = 0, and is experimentally calculated from the plot.

  Although the film thickness of the said separator for nonaqueous electrolyte secondary batteries is not specifically limited, It is preferable that it is 4-40 micrometers, and it is more preferable that it is 5-20 micrometers.

  If the film thickness of the said separator for nonaqueous electrolyte secondary batteries is 4 micrometers or more, it is preferable from a viewpoint that the internal short circuit of a battery can fully be prevented.

  On the other hand, if the thickness of the separator for a non-aqueous electrolyte secondary battery is 40 μm or less, it is preferable from the viewpoint that an increase in the size of the non-aqueous electrolyte secondary battery can be prevented.

The weight per unit area of the non-aqueous electrolyte secondary battery separator is usually 4 to 20 g / m ² so that the weight energy density and volume energy density of the battery can be increased. Preferably, it is 5-12 g / m < ² >.

  The air permeability of the non-aqueous electrolyte secondary battery separator is preferably 30 to 500 sec / 100 mL, preferably 50 to 300 sec / 100 mL in terms of Gurley value, from the viewpoint of exhibiting sufficient ion permeability. More preferred.

  The porosity of the non-aqueous electrolyte secondary battery separator is 20 so as to increase the amount of electrolyte retained and to obtain a function of reliably preventing (shutdown) an excessive current from flowing at a lower temperature. The volume is preferably 80% by volume to 80% by volume, and more preferably 30% to 75% by volume.

  The pore diameter of the pores of the non-aqueous electrolyte secondary battery separator is preferably 0.3 μm or less from the viewpoint of sufficient ion permeability and prevention of particles entering the electrode, More preferably, it is 0.14 μm or less.

  In addition to the polyolefin porous film, the nonaqueous electrolyte secondary battery separator in an embodiment of the present invention may further include a heat-resistant layer, an adhesive layer, a protective layer, and the like as necessary.

[Polyolefin porous film production method]
The method for producing the polyolefin porous film is not particularly limited. For example, a polyolefin resin, a petroleum resin, and a plasticizer are kneaded and then extruded to produce a sheet-like polyolefin resin composition. Examples include a method of stretching the polyolefin resin composition, removing a part or all of the plasticizer with an appropriate solvent, and drying and heat-setting.

Specifically, the method shown below can be mentioned.
(A) adding a polyolefin-based resin and a petroleum resin to a kneader and melt-kneading to obtain a molten mixture;
(B) a step of adding a plasticizer to the obtained molten mixture and kneading to obtain a polyolefin resin composition;
(C) Extruding the obtained polyolefin resin composition from a T-die of an extruder, forming into a sheet shape while cooling, and obtaining a sheet-like polyolefin resin composition;
(D) a step of stretching the obtained sheet-like polyolefin resin composition,
(E) a step of washing the stretched polyolefin resin composition using a washing liquid;
(F) A step of obtaining a polyolefin porous film by drying and heat-setting the washed polyolefin resin composition.

  In the step (A), the amount of the polyolefin resin used is preferably 6% by weight to 45% by weight, and 9% by weight to 36% by weight when the weight of the polyolefin resin composition obtained is 100% by weight. It is more preferable that

  As petroleum resins, aliphatic hydrocarbon resins polymerized using C5 petroleum fractions such as isoprene, pentene and pentadiene as main raw materials; polymerized using C9 petroleum fractions such as indene, vinyltoluene and methylstyrene as main raw materials. Aromatic hydrocarbon resins; copolymer resins thereof; alicyclic saturated hydrocarbon resins obtained by hydrogenating the resins; and mixtures thereof. The petroleum resin is preferably an alicyclic saturated hydrocarbon resin. The petroleum resin has a feature that it is easily oxidized because it has many unsaturated bonds and tertiary carbons that easily generate radicals in its structure.

  By mixing the petroleum resin with the polyolefin resin composition, the interaction between the resin wall inside the resulting polyolefin porous film and the charge carrier can be adjusted. That is, the ion permeation barrier energy of the separator for a nonaqueous electrolyte secondary battery can be suitably adjusted.

  By mixing petroleum resin, which is a component that is more easily oxidized than polyolefin resin, the resin wall inside the resulting polyolefin porous film can be appropriately oxidized, that is, compared with the case where no petroleum resin is added. When a petroleum resin is added, the ion permeation barrier energy of the obtained nonaqueous electrolyte secondary battery separator increases.

  The petroleum resin preferably has a softening point of 90 ° C to 125 ° C. The amount of the petroleum resin used is preferably 0.5 wt% to 40 wt%, preferably 1 wt% to 30 wt%, when the weight of the polyolefin resin composition obtained is 100 wt%. More preferred.

  Examples of the plasticizer include phthalates such as dioctyl phthalate, unsaturated higher alcohols such as oleyl alcohol, saturated higher alcohols such as paraffin wax and stearyl alcohol, and liquid paraffin.

  In the step (B), the temperature inside the kneader when the plasticizer is added to the kneader is preferably 135 ° C. or higher and 200 ° C. or lower, more preferably 140 ° C. or higher and 170 ° C. or lower.

  By controlling the temperature inside the kneader within the above range, the plasticizer can be added in a state where the polyolefin resin and the petroleum resin are suitably mixed. As a result, the effect of mixing the polyolefin resin and the petroleum resin can be obtained more suitably.

  For example, if the temperature inside the kneader when adding the plasticizer is too low, the polyolefin resin and the petroleum resin cannot be uniformly mixed, and the resin wall inside the polyolefin porous film cannot be appropriately oxidized. There is a case. On the other hand, when the said temperature is too high (for example, 200 degreeC or more), the thermal deterioration of resin may occur.

  In the step (D), the stretching may be performed only in the MD direction, may be performed only in the TD direction, or may be performed in both the MD direction and the TD direction. As a method of stretching in both the MD direction and the TD direction, after stretching in the MD direction, the subsequent biaxial stretching in which the stretching is performed in the TD direction, and the simultaneous biaxial stretching in which the stretching in the MD direction and the TD direction are performed simultaneously. Is mentioned.

  For stretching, a method may be used in which the end of the sheet-like polyolefin resin composition is gripped and stretched with a chuck, or a method of stretching by changing the rotation speed of a roll for conveying the sheet-like polyolefin resin composition. Alternatively, a method of rolling a sheet-like polyolefin resin composition using a pair of rolls may be used.

  In the step (D), the stretching ratio when the sheet-like polyolefin resin composition is stretched in the MD direction is preferably 3.0 times or more and 7.0 times or less, more preferably 4.5 times. It is more than twice and less than 6.5 times. The stretch ratio when the sheet-like polyolefin resin composition stretched in the MD direction is further stretched in the TD direction is preferably 3.0 times or more and 7.0 times or less, more preferably 4.5 times. As mentioned above, it is 6.5 times or less.

  The stretching temperature is preferably 130 ° C. or lower, and more preferably 110 ° C. to 120 ° C.

  In the step (E), the cleaning liquid is not particularly limited as long as it is a solvent that can remove the plasticizer and the like. For example, aliphatic hydrocarbons such as heptane, octane, nonane, decane, methylene chloride, chloroform, dichloroethane, 1, 2 -Halogenated hydrocarbons such as dichloropropane.

  In the step (F), the washed polyolefin resin composition is heat-treated at a specific temperature to be dried and heat-set.

  Drying and heat setting is usually performed in the air using a ventilating dryer or a heating roll.

  From the viewpoint of further finely adjusting the degree of oxidation of the resin wall inside the polyolefin porous film and suitably controlling the interaction between the resin wall inside the polyolefin porous film and the charge carrier, the drying and heat setting is preferably 100. It is carried out at a temperature of not less than 150 ° C. and not more than 150 ° C., more preferably not less than 110 ° C. and not more than 140 ° C., more preferably not less than 120 ° C. and not more than 135 ° C. The drying / heat setting is preferably performed over a period of 1 minute to 60 minutes, more preferably 1 minute to 30 minutes.

[Laminate]
The separator for a non-aqueous electrolyte secondary battery provided in the non-aqueous electrolyte secondary battery according to an embodiment of the present invention is the non-aqueous electrolyte secondary battery described in the above section [Separator for non-aqueous electrolyte secondary battery]. The aspect which equips the single side | surface or both surfaces of the polyolefin porous film in the separator for secondary batteries with an insulating porous layer may be sufficient. Hereinafter, the separator for a nonaqueous electrolyte secondary battery according to this aspect may be referred to as a “laminated body”. In addition, the non-aqueous electrolyte secondary battery separator described in the section [Non-aqueous electrolyte secondary battery separator] may be referred to as “separator 1”.

[Insulating porous layer]
The insulating porous layer is usually a resin layer containing a resin, preferably a heat-resistant layer or an adhesive layer. The resin constituting the insulating porous layer (hereinafter also simply referred to as “porous layer”) is insoluble in the electrolyte of the battery and is electrochemically stable in the battery usage range. preferable.

  A porous layer is laminated | stacked on the single side | surface or both surfaces of the said polyolefin porous film as needed, and comprises a laminated body. When a porous layer is laminated only on one side of the polyolefin porous film, the porous layer is preferably the polyolefin porous in the non-aqueous electrolyte secondary battery according to one embodiment of the present invention. It is laminated | stacked on the surface facing the positive electrode in a film, More preferably, it laminate | stacks on the surface which contact | connects a positive electrode.

  Examples of the resin constituting the porous layer include polyolefin, (meth) acrylate resin, fluorine-containing resin, polyamide resin, polyimide resin, polyester resin, rubbers, and a melting point or glass transition temperature of 180 ° C. or higher. Resin; Water-soluble polymer etc. are mentioned.

  Of the above-mentioned resins, polyolefins, polyester resins, acrylate resins, fluorine-containing resins, polyamide resins, and water-soluble polymers are preferable. As the polyamide-based resin, a wholly aromatic polyamide (aramid resin) is preferable. As the polyester resin, polyarylate and liquid crystal polyester are preferable.

  The porous layer may contain fine particles. The fine particles in the present specification are organic fine particles or inorganic fine particles generally called a filler. Therefore, when the porous layer includes fine particles, the above-described resin contained in the porous layer has a function as a binder resin that binds the fine particles to each other and the fine particles and the porous film. The fine particles are preferably insulating fine particles.

  Examples of the organic fine particles contained in the porous layer include fine particles made of a resin.

  Specifically, as the inorganic fine particles contained in the porous layer, for example, calcium carbonate, talc, clay, kaolin, silica, hydrotalcite, diatomaceous earth, magnesium carbonate, barium carbonate, calcium sulfate, magnesium sulfate, barium sulfate, Examples include fillers made of inorganic substances such as aluminum hydroxide, boehmite, magnesium hydroxide, calcium oxide, magnesium oxide, titanium oxide, titanium nitride, alumina (aluminum oxide), aluminum nitride, mica, zeolite, and glass. These inorganic fine particles are insulating fine particles. Only one type of the fine particles may be used, or two or more types may be used in combination.

  Among the fine particles, fine particles made of an inorganic substance are preferable, and fine particles made of an inorganic oxide such as silica, calcium oxide, magnesium oxide, titanium oxide, alumina, mica, zeolite, aluminum hydroxide, or boehmite are more preferable, and silica Further, at least one fine particle selected from the group consisting of magnesium oxide, titanium oxide, aluminum hydroxide, boehmite and alumina is more preferable, and alumina is particularly preferable.

  The content of fine particles in the porous layer is preferably 1 to 99% by volume of the porous layer, and more preferably 5 to 95% by volume. By setting the content of the fine particles in the above range, voids formed by contact between the fine particles are less likely to be blocked by a resin or the like. Therefore, sufficient ion permeability can be obtained, and the basis weight per unit area can be set to an appropriate value.

  The fine particles may be used in combination of two or more different particles or specific surface areas.

  The thickness of the porous layer is preferably 0.5 to 15 μm and more preferably 2 to 10 μm per layer.

  When the thickness of the porous layer is less than 0.5 μm per layer, an internal short circuit due to battery breakage or the like may not be sufficiently prevented. In addition, the amount of electrolytic solution retained in the porous layer may decrease. On the other hand, when the thickness of the porous layer exceeds 15 μm per layer, battery characteristics may be deteriorated.

Fabric weight per unit area of the porous layer is preferably around from 1 to 20 g / ^{m 2} more, and more preferably around 4~10g / ^{m 2} more.

The volume of the porous layer constituents contained per square meter porous layer is preferably 0.5～20Cm ³ per layer, more preferably from 1 to 10 cm ³ per layer per layer More preferably, it is 2-7 cm ³ .

  The porosity of the porous layer is preferably 20 to 90% by volume, and more preferably 30 to 80% by volume so that sufficient ion permeability can be obtained. Further, the pore diameter of the pores of the porous layer is preferably 3 μm or less, and more preferably 1 μm or less from the viewpoint of preventing the particles constituting the electrode from entering the pores.

  The film thickness of the laminate in one embodiment of the present invention is preferably 5.5 μm to 45 μm, and more preferably 6 μm to 25 μm.

  The air permeability of the laminate in one embodiment of the present invention is preferably 30 to 1000 sec / 100 mL as a Gurley value, and more preferably 50 to 800 sec / 100 mL.

  In addition to the polyolefin porous film and the insulating porous layer, the laminate in one embodiment of the present invention may be a known porous film (porous material) such as a heat-resistant layer, an adhesive layer, or a protective layer, if necessary. May be included in a range not impairing the object of the present invention.

  The laminate in one embodiment of the present invention has ion permeation barrier energy per unit film thickness in the same specific range as the separator 1. Therefore, the resistance increase rate after repeating the charging / discharging cycle of the nonaqueous electrolyte secondary battery including the laminate can be reduced, and cycle characteristics can be improved. The ion permeation barrier energy per unit film thickness of the laminate is, for example, the ion permeation barrier energy per unit film thickness of the separator 1 included in the laminate, as described in the above method (petroleum resin is converted to polyolefin resin composition). It can be controlled by adjusting by mixing).

[Manufacturing method of laminate]
As a manufacturing method of the laminated body in one Embodiment of this invention, the method of depositing a porous layer by apply | coating the coating liquid mentioned later to the surface of the said polyolefin porous film, and drying is mentioned, for example.

  In addition, before apply | coating the said coating liquid to the surface of the said polyolefin porous film, the hydrophilic treatment can be performed to the surface which applies the coating liquid of the said polyolefin porous film as needed.

  The coating liquid used in the method for producing a laminate in one embodiment of the present invention usually dissolves a resin that can be contained in the above-mentioned porous layer in a solvent and fine particles that can be contained in the above-mentioned porous layer. Can be prepared by dispersing. Here, the solvent for dissolving the resin also serves as a dispersion medium for dispersing the fine particles. Here, the resin may be contained in the coating liquid as an emulsion without being dissolved in the solvent.

  The solvent (dispersion medium) is not particularly limited as long as it does not adversely affect the polyolefin porous film, can dissolve the resin uniformly and stably, and can uniformly and stably disperse the fine particles. Specific examples of the solvent (dispersion medium) include water and organic solvents. Only one type of solvent may be used, or two or more types may be used in combination.

  The coating liquid may be formed by any method as long as the conditions such as the resin solid content (resin concentration) and the amount of fine particles necessary for obtaining a desired porous layer can be satisfied. Specific examples of the method for forming the coating liquid include a mechanical stirring method, an ultrasonic dispersion method, a high-pressure dispersion method, and a media dispersion method. In addition, the coating liquid may contain additives such as a dispersant, a plasticizer, a surfactant, and a pH adjuster as components other than the resin and fine particles as long as the object of the present invention is not impaired. . In addition, the addition amount of an additive should just be a range which does not impair the objective of this invention.

  The method for applying the coating liquid to the polyolefin porous film, that is, the method for forming the porous layer on the surface of the polyolefin porous film is not particularly limited. As a method for forming the porous layer, for example, a method in which the coating liquid is directly applied to the surface of the polyolefin porous film, and then the solvent (dispersion medium) is removed; the coating liquid is applied to a suitable support, and the solvent (Dispersion medium) is removed to form a porous layer, and then the porous layer and the polyolefin porous film are pressure-bonded, and then the support is peeled off; after the coating liquid is applied to a suitable support, Examples include a method in which a polyolefin porous film is pressure-bonded to the coated surface, and then the solvent (dispersion medium) is removed after peeling off the support.

  As a method for applying the coating liquid, a conventionally known method can be employed. Specific examples include a gravure coater method, a dip coater method, a bar coater method, and a die coater method.

  As a method for removing the solvent (dispersion medium), a drying method is generally used. Further, the solvent (dispersion medium) contained in the coating liquid may be replaced with another solvent before drying.

[Positive electrode]
The positive electrode provided in the non-aqueous electrolyte secondary battery according to one embodiment of the present invention is not particularly limited as long as it is generally used as the positive electrode of the non-aqueous electrolyte secondary battery. A positive electrode sheet having a structure in which an active material layer containing a substance and a binder resin is formed on a current collector can be used. The active material layer may further contain a conductive agent and / or a binder.

  Examples of the positive electrode active material include materials that can be doped / undoped with metal ions such as lithium ions or sodium ions. Specific examples of the material include lithium composite oxides containing at least one transition metal such as V, Mn, Fe, Co, and Ni.

  Examples of the conductive agent include carbonaceous materials such as natural graphite, artificial graphite, cokes, carbon black, pyrolytic carbons, carbon fibers, and organic polymer compound fired bodies. Only one type of the conductive agent may be used, or two or more types may be used in combination.

  Examples of the binder include fluorine resins such as polyvinylidene fluoride (PVDF), acrylic resins, and styrene butadiene rubber. The binder also has a function as a thickener.

  Examples of the positive electrode current collector include conductors such as Al, Ni, and stainless steel. Among these, Al is more preferable because it is easily processed into a thin film and is inexpensive.

  As a method for producing a sheet-like positive electrode, for example, a method in which a positive electrode active material, a conductive agent and a binder are pressure-molded on a positive electrode current collector; a positive electrode active material, a conductive agent and a binder using an appropriate organic solvent are used. Examples include a method in which the paste is formed into a paste, and then the paste is applied to the positive electrode current collector, dried and then pressed to fix the positive electrode current collector.

[Negative electrode]
The negative electrode provided in the non-aqueous electrolyte secondary battery according to one embodiment of the present invention is not particularly limited as long as it is generally used as a negative electrode of a non-aqueous electrolyte secondary battery. A negative electrode sheet having a structure in which an active material layer containing a substance and a binder resin is formed on a current collector can be used. The active material layer may further contain a conductive agent.

  Examples of the negative electrode active material include materials that can be doped / undoped with metal ions such as lithium ions or sodium ions. Examples of the material include a carbonaceous material. Examples of the carbonaceous material include natural graphite, artificial graphite, coke, carbon black, and pyrolytic carbon.

  Examples of the negative electrode current collector include conductors such as Cu, Ni, and stainless steel. Cu is more preferable because it is difficult to form an alloy with lithium and is easy to process into a thin film.

  As a method for producing a sheet-like negative electrode, for example, a method in which a negative electrode active material is pressure-molded on a negative electrode current collector; the negative electrode active material is made into a paste using an appropriate organic solvent, For example, a method of applying to an electric body, drying and pressurizing to adhere to a negative electrode current collector; The paste preferably contains the conductive agent and the binder.

[Non-aqueous electrolyte]
In the non-aqueous electrolyte in one embodiment of the present invention, an additive having an ionic conductivity reduction rate L represented by the following formula (A) of 1.0% or more and 6.0% or less is 0.5 ppm to 300 ppm. contains.
L = (LA−LB) / LA (A)
Wherein (A), LA is a mixed solvent in a proportion of ethylene carbonate / ethyl methyl carbonate / diethyl carbonate = 3/5/2 (volume ratio), so that the concentration of LiPF ₆ is 1 mol / L LiPF ₆ Represents the ionic conductivity (mS / cm) of the reference electrolyte solution in which LB is dissolved, and LB is the ionic conductivity (mS / cm) of the electrolyte solution in which 1.0% by weight of the additive is dissolved in the reference electrolyte solution. cm).

  The additive is not particularly limited as long as it is a compound that satisfies the above requirements (the ionic conductivity reduction rate L represented by the formula (A) is 1.0% or more and 6.0% or less). Specific examples of the compound that satisfies the above requirements include pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], triethyl phosphate, vinylene carbonate, propane sultone, 2,6-di-tert-butyl-4-methylphenol, 6- [3- (3-t-Butyl-4-hydroxy-5-methylphenyl) propoxy] -2,4,8,10-tetra-t- butyrdibenzo [d, f] [1,3,2] dioxaphospine, tris (2,4-di-tert-butylphenyl) phosphate, 2- [1- (2-hydroxy-3,5-di-tert-pentylphenyl) ) Ethyl] -4,6-di-tert-pe tylphenyl acrylate, and di-butyl hydroxy toluene.

The non-aqueous electrolyte in one embodiment of the present invention generally includes an electrolyte and an organic solvent, similarly to the non-aqueous electrolyte used in a non-aqueous electrolyte secondary battery. Examples of the electrolyte include LiClO ₄ , LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , Li ₂ B ₁₀ Cl. ₁₀ , metal salts such as lithium salt such as lower aliphatic carboxylic acid lithium salt and LiAlCl ₄ . Only one type of electrolyte may be used, or two or more types may be used in combination.

  Examples of the organic solvent constituting the non-aqueous electrolyte include carbonates, ethers, esters, nitriles, amides, carbamates and sulfur-containing compounds, and fluorine groups introduced into these organic solvents. Examples include aprotic polar solvents such as fluorine-containing organic solvents. The organic solvent may be used alone or in combination of two or more.

  The organic solvent is preferably a mixed solvent containing a cyclic compound such as EC and a chain compound such as EMC and DEC, like the reference electrolyte. The mixed solvent contains the cyclic compound and the chain compound, preferably in a ratio of cyclic compound: chain compound = 2: 8 to 4: 6 (volume ratio), more preferably 2: 8 to It is included at a ratio of 3: 7 (volume ratio), particularly preferably at a ratio of 3: 7 (volume ratio). In addition, the mixed solvent mixed in the ratio of cyclic compound: chain compound = 3: 7 (volume ratio) is an organic solvent that is generally used in the non-aqueous electrolyte of the non-aqueous electrolyte secondary battery.

  In one embodiment of the present invention, the additive reduces the ionic conductivity of the reference electrolyte.

  The reason why the deterioration of the battery characteristics can be suppressed by adding the additive in one embodiment of the present invention to the non-aqueous electrolyte solution is not clear, but for example, by adding the additive, particularly during charging and discharging. When the battery is operated at high speed, the degree of ion dissociation in the vicinity of the electrode (positive electrode) can be reduced, and ion depletion in the vicinity of the electrode (positive electrode) can be reduced, thereby reducing the battery characteristics accompanying charging and discharging. The reason that it can suppress is considered.

  From the viewpoint of reducing ion depletion in the vicinity of the electrode, in the non-aqueous electrolyte secondary battery according to an embodiment of the present invention, the non-aqueous electrolyte contains 0.5 ppm or more of the additive, and contains 20 ppm or more. It is preferable to contain 45 ppm or more.

  On the other hand, when the content of the additive is excessively large, not only reducing the ion depletion in the vicinity of the above-described electrode, but also the degree of ion dissociation of the entire electrolyte in the embodiment of the present invention is excessively decreased. It is considered that the ion flow in the entire non-aqueous electrolyte secondary battery is hindered and the battery characteristics are deteriorated.

  From the viewpoint of suppressing the inhibition of the flow of ions in the entire non-aqueous electrolyte secondary battery, the non-aqueous electrolyte is the additive in the non-aqueous electrolyte secondary battery according to an embodiment of the present invention. Of 300 ppm or less, preferably 250 ppm or less, and more preferably 180 ppm or less.

  Here, in the non-aqueous electrolyte secondary battery according to an embodiment of the present invention that includes a non-aqueous electrolyte containing 0.5 ppm or more and 300 ppm or less of the additive, particularly when charging and discharging are repeated, The degree of ion dissociation in the vicinity of the electrode (positive electrode) when the battery is operated is strongly influenced by the strength (affinity) of the interaction between the additive and ions rather than the dielectric constant of the organic solvent. .

  Therefore, the non-aqueous electrolyte secondary battery according to one embodiment of the present invention suitably reduces the degree of ion dissociation near the electrode (positive electrode) regardless of the type of non-aqueous electrolyte in one embodiment of the present invention. can do. That is, regardless of the type and amount of the electrolyte contained in the non-aqueous electrolyte and the type of the organic solvent contained, by containing the additive in the range of 0.5 ppm to 300 ppm, the vicinity of the electrode (positive electrode) The degree of ion dissociation can be suitably reduced. As a result, it is possible to suppress a decrease in battery characteristics associated with charge / discharge.

  That is, as described above, the ion permeation barrier energy of the non-aqueous electrolyte secondary battery separator is adjusted to an appropriate range, and the ionic conductivity reduction rate and content of the additive contained in the non-aqueous electrolyte are set to a specific range. By adjusting, the flow of ions in the non-aqueous electrolyte secondary battery including these is adjusted to a suitable one, and as a result, the deterioration of the battery characteristics of the non-aqueous electrolyte secondary battery can be sufficiently suppressed. .

  The method for controlling the additive content in the non-aqueous electrolyte to 0.5 ppm or more and 300 ppm or less is not particularly limited. For example, in the method for producing a non-aqueous electrolyte secondary battery described later, non-aqueous electrolysis Examples include a method of dissolving the additive in advance in the non-aqueous electrolyte to be poured into a container that is a casing of a liquid secondary battery so that the content thereof is 0.5 ppm or more and 300 ppm or less. it can.

[Method for producing non-aqueous electrolyte secondary battery]
As a method for producing a non-aqueous secondary battery according to an embodiment of the present invention, a conventionally known production method can be employed. As a conventionally known manufacturing method, for example, a non-aqueous electrolyte secondary battery member is formed by arranging the positive electrode, the non-aqueous electrolyte secondary battery separator, and the negative electrode in this order. By putting the non-aqueous electrolyte secondary battery member into a container serving as a casing of the liquid secondary battery, and then filling the container with the non-aqueous electrolyte, and then sealing the container while reducing the pressure, the present invention The method of manufacturing the nonaqueous electrolyte secondary battery which concerns on one Embodiment can be mentioned.

  Hereinafter, although an example and a comparative example explain the present invention still in detail, the present invention is not limited to these examples.

[Measuring method]
The physical properties and the like of the separators for non-aqueous electrolyte secondary batteries produced in Examples and Comparative Examples, and the cycle characteristics of the non-aqueous electrolyte secondary batteries were measured using the following methods.

(1) Film thickness (unit: μm):
The film thickness of the separator for non-aqueous electrolyte secondary batteries was measured using a high precision digital length measuring machine (VL-50) manufactured by Mitutoyo Corporation.

(2) Air permeability (unit: sec / 100 mL):
The air permeability of the non-aqueous electrolyte secondary battery separator was measured in accordance with JIS P8117.

(3) Ion permeation barrier energy per unit film thickness of non-aqueous electrolyte secondary battery separator (unit: J / mol / μm)
A separator for a non-aqueous electrolyte secondary battery was cut into a disk shape having a diameter of 17 mm and sandwiched between two SUS plates having a thickness of 0.5 mm and a diameter of 15.5 mm, and an electrolyte was injected to prepare a coin cell (CR2032 type). Here, as an electrolytic solution, a concentration of LiPF ₆ was mixed with a mixed solvent mixed at a ratio of ethylene carbonate (EC) / ethyl methyl carbonate (EMC) / diethyl carbonate (DEC) = 3/5/2 (volume ratio). A solution in which LiPF ₆ was dissolved so as to have a concentration of 1 mol / L was used.

The produced coin cell was installed in the thermostat set to the predetermined temperature mentioned later. Subsequently, a Nyquist plot was calculated at a frequency of 1 MHz to 0.1 Hz and a voltage amplitude of 10 mV using a Solartron AC impedance device (FRA 1255B) and a cell test system (1470E). the solution resistance r ₀ of the separator for aqueous electrolyte secondary battery was determined. Using the obtained values, the ion permeation barrier energy was calculated from the following formulas (1) and (2). The temperature of the thermostat was set to 50 ° C, 25 ° C, 5 ° C, and -10 ° C.

  Here, the ion permeation barrier energy is expressed by the following formula (1).

k = 1 / r ₀ = Aexp (−Ea / RT) (1)
Ea: ion permeation barrier energy (J / mol)
k: Reaction constant r ₀ : Liquid resistance (Ω)
A: Frequency factor R: Gas constant = 8.314 J / mol / K
T: Temperature of constant temperature bath (K)
Taking the natural logarithm of both sides of Equation (1), the following Equation (2) is obtained. Based on the equation (2), ln (1 / r ₀ ) is plotted against the reciprocal of the temperature, and -Ea / R, which is the slope of a straight line obtained by the least square method, is obtained from the plot, -Ea / Ea was calculated by multiplying the value of R by the gas constant R. Thereafter, the calculated Ea was divided by the film thickness of the nonaqueous electrolyte secondary battery separator to calculate the ion permeation barrier energy per unit film thickness.

ln (k) = ln (1 / r ₀ ) = lnA−Ea / RT (2)
(4) Rate of decrease in ionic conductivity (%)
LiPF was mixed with a mixed solvent in which ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed at a ratio of 3: 5: 2 (volume ratio) so that the concentration of LiPF ₆ was 1 mol / L. ₆ was dissolved to prepare a reference electrolyte solution.

  The ionic conductivity of the reference electrolyte is measured using an electrical conductivity meter (ES-71) manufactured by HORIBA, Ltd., and the ionic conductivity (LA) of the reference electrolyte before the additive is added. did.

  After each additive used in Examples and Comparative Examples was added to diethyl carbonate so as to be 20.0% by weight and dissolved, the reference electrolyte solution was added to the reference electrolyte solution. An electrolyte solution in which the additive was dissolved at a concentration of 1.0% by weight (hereinafter referred to as “1.0% by weight additive solution”) was prepared.

  Then, using the electric conductivity meter (ES-71), the ionic conductivity of the 1.0 wt% additive solution was measured, and the ionic conductivity (LB) of the reference electrolyte solution after the additive was added It was.

  From the ionic conductivity of the reference electrolyte before and after the addition of the additive, the ionic conductivity reduction rate was calculated based on the following formula (A).

L = (LA−LB) / LA (A)
L: Decrease rate of ionic conductivity (%)
LA: Ionic conductivity (mS / cm) of the reference electrolyte before adding the additive
LB: Ionic conductivity (mS / cm) of the electrolyte after adding the additive to the reference electrolyte
(5) Cycle characteristics: capacity retention ratio The capacity retention ratio after 100 cycles of the non-aqueous electrolyte secondary batteries manufactured in Examples and Comparative Examples was measured by the method described below, and the cycle characteristics were evaluated.

  With respect to non-aqueous electrolyte secondary batteries that were not subjected to the charge / discharge cycle manufactured in Examples and Comparative Examples, voltage range at 25 ° C .; 4.1 to 2.7 V, current value; 0.2 C (1 hour rate) 4 cycles of initial charge / discharge was performed with 1 cycle as the current value for discharging the rated capacity of 1 hour after 1 hour, and the same for the following.

  First, the capacity | capacitance (initial capacity) of the nonaqueous electrolyte secondary battery which performed initial stage charge / discharge was measured. Subsequently, charging and discharging with a constant current of 1 C, a discharge current value; 10 C at 55 ° C. is performed as one cycle for the non-aqueous electrolyte secondary battery after measuring the initial capacity at 55 ° C. 100 cycles of charge and discharge were performed. And the capacity | capacitance (capacity | capacitance after 100 cycles) of the nonaqueous electrolyte secondary battery which charged / discharged 100 cycles was measured.

  The ratio of the capacity after 100 cycles to the initial capacity measured by the above method was calculated and used as the capacity retention rate after 100 cycles.

[Example 1]
[Manufacture of separators for non-aqueous electrolyte secondary batteries]
18 parts by weight of ultra-high molecular weight polyethylene powder (Hi-Zex Million 145M, manufactured by Mitsui Chemicals), 2 parts of petroleum resin (alicyclic saturated hydrocarbon resin having a softening point of 90 ° C.) having many tertiary carbon atoms in the structure Prepared the department. Using a blender, the ultrahigh molecular weight polyethylene powder and the petroleum resin were pulverized and mixed until the powder had the same particle size, whereby a mixture 1 was obtained.

  Next, the mixture 1 was added to a biaxial kneader from a quantitative feeder and melt-kneaded. At this time, the temperature inside the biaxial kneader immediately before the liquid paraffin was added was set to 144 ° C., and 80 parts by weight of liquid paraffin was side-feeded to the biaxial kneader by a pump. The “temperature inside the twin-screw kneader” refers to the temperature inside the segment type barrel in the twin-screw kneader. The segment-type barrel refers to a block-type barrel that can be connected to an arbitrary length.

  Thereafter, the melt-kneaded mixture 1 was extruded through a gear pump from a T die set at 210 ° C. into a sheet shape to obtain a sheet-shaped polyolefin resin composition 1. The extruded sheet-like polyolefin resin composition 1 was cooled by being held in a cooling roll. After cooling, the sheet-shaped polyolefin resin composition 1 is stretched by 6.4 times in the MD direction, and then sequentially stretched by 6.0 times in the TD direction. The stretched polyolefin resin composition 2 Got.

  After the stretched polyolefin resin composition 2 is washed with a washing liquid (heptane), it is left to stand in a ventilated oven at 118 ° C. for 1 minute to dry the washed sheet (sheet-like polyolefin resin composition). -Heat setting was performed to obtain a polyolefin porous film. The obtained polyolefin porous film was used as the separator 1 for a nonaqueous electrolyte secondary battery.

  Then, the physical property of the obtained separator 1 for nonaqueous electrolyte secondary batteries was measured with the above-mentioned measuring method. The nonaqueous electrolyte secondary battery separator 1 had a film thickness of 23 μm and an air permeability of 128 sec / 100 mL. Table 1 shows the measured physical properties of the nonaqueous electrolyte secondary battery separator 1.

[Preparation of non-aqueous electrolyte secondary battery]
(Preparation of positive electrode)
A commercially available positive electrode manufactured by applying LiNi _0.5 Mn _0.3 Co _0.2 O ₂ / conductive agent / PVDF (weight ratio 92/5/3) to an aluminum foil was used. The commercially available positive electrode is made of aluminum foil so that the size of the portion where the positive electrode active material layer is formed is 40 mm × 35 mm, and the portion where the width is 13 mm and the positive electrode active material layer is not formed remains on the outer periphery. A positive electrode was cut out. The positive electrode active material layer had a thickness of 58 μm and a density of 2.50 g / cm ³ .

(Preparation of negative electrode)
A commercially available negative electrode produced by applying graphite / styrene-1,3-butadiene copolymer / sodium carboxymethylcellulose (weight ratio 98/1/1) to a copper foil was used. The commercially available negative electrode is made of copper foil so that the size of the portion where the negative electrode active material layer is formed is 50 mm × 40 mm and the outer periphery of the negative electrode active material layer is 13 mm wide and no negative electrode active material layer is formed. A negative electrode was cut out. The thickness of the negative electrode active material layer was 49 μm, and the density was 1.40 g / cm ³ .

(Preparation of electrolyte)
LiPF ₆ is dissolved in a mixed solvent in which ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate are mixed at a ratio of 3: 5: 2 (volume ratio) so that the concentration of LiPF ₆ is 1 mol / L. Aprotic polar solvent electrolyte containing Li ⁺ ions).

  Diethyl carbonate was added to 10.2 mg of pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] (ionic conductivity decrease rate: 4.0%), which is an additive, and dissolved. It was made 5 mL, and it was set as the addition liquid 1. 90 μL of additive solution 1 and 1910 μL of electrolyte solution stock solution 1 were mixed to obtain electrolyte solution 1. In addition, content of the additive in the electrolyte solution used in the following Examples and Comparative Examples is shown in Table 1 described later.

(Assembly of non-aqueous electrolyte secondary battery)
Using the positive electrode, the negative electrode, the separator 1 for a nonaqueous electrolyte secondary battery, and the electrolyte 1, a nonaqueous electrolyte secondary battery was produced by the method described below. The produced non-aqueous electrolyte secondary battery was designated as non-aqueous electrolyte secondary battery 1.

  By laminating (arranging) the positive electrode, the nonaqueous electrolyte secondary battery separator 1, and the negative electrode in this order in a laminate pouch, a nonaqueous electrolyte secondary battery member 1 was obtained. At this time, the positive electrode and the negative electrode were disposed so that the entire main surface of the positive electrode active material layer of the positive electrode was included in the range of the main surface of the negative electrode active material layer of the negative electrode (overlaid on the main surface).

  Subsequently, the non-aqueous electrolyte secondary battery member 1 was put in a bag prepared in advance by laminating an aluminum layer and a heat seal layer, and 0.23 mL of the electrolyte 1 was put in this bag. . And the non-aqueous-electrolyte secondary battery 1 was produced by heat-sealing the said bag, decompressing the inside of a bag.

  Thereafter, the cycle characteristics of the nonaqueous electrolyte secondary battery 1, that is, the capacity retention rate (%) after 100 cycles were measured. The results are shown in Table 1.

[Example 2]
[Preparation of non-aqueous electrolyte secondary battery]
(Preparation of electrolyte)
Diethyl carbonate was added to 10.3 mg of dibutylhydroxytoluene (decrease in ionic conductivity: 5.3%) as an additive, and dissolved to make 5 mL. 90 μL of the additive solution 2 and 1910 μL of the electrolyte solution stock solution 1 were mixed to obtain an electrolyte solution 2.

(Assembly of non-aqueous electrolyte secondary battery)
A nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 except that the electrolyte solution 2 was used instead of the electrolyte solution 1. The produced non-aqueous electrolyte secondary battery was designated as non-aqueous electrolyte secondary battery 2.

  Thereafter, the cycle characteristics of the nonaqueous electrolyte secondary battery 2, that is, the capacity retention rate (%) after 100 cycles were measured. The results are shown in Table 1.

[Example 3]
[Preparation of non-aqueous electrolyte secondary battery]
(Preparation of electrolyte)
45 μL of the additive solution 1 and 1955 μL of the electrolyte solution stock solution 1 were mixed to obtain an electrolyte solution 3.

(Assembly of non-aqueous electrolyte secondary battery)
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that the electrolyte solution 3 was used instead of the electrolyte solution 1. The produced non-aqueous electrolyte secondary battery was designated as non-aqueous electrolyte secondary battery 3.

  Thereafter, the cycle characteristics of the nonaqueous electrolyte secondary battery 3, that is, the capacity retention rate (%) after 100 cycles were measured. The results are shown in Table 1.

[Example 4]
[Preparation of non-aqueous electrolyte secondary battery]
(Preparation of electrolyte)
180 μL of the additive solution 1 and 1820 μL of the electrolyte solution stock solution 1 were mixed to obtain an electrolyte solution 4.

(Assembly of non-aqueous electrolyte secondary battery)
A nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 except that the electrolyte solution 4 was used instead of the electrolyte solution 1. The produced non-aqueous electrolyte secondary battery was designated as non-aqueous electrolyte secondary battery 4.

  Thereafter, the cycle characteristics of the nonaqueous electrolyte secondary battery 4, that is, the capacity retention rate (%) after 100 cycles were measured. The results are shown in Table 1.

[Example 5]
[Preparation of non-aqueous electrolyte secondary battery]
(Preparation of electrolyte)
Diethyl carbonate was added to 10.0 mg of vinylene carbonate (ionic conductivity lowering rate: 1.3%) as an additive, and dissolved to make 5 mL. 90 μL of the additive solution 3 and 1910 μL of the electrolyte solution stock solution 1 were mixed to obtain an electrolyte solution 5.

(Assembly of non-aqueous electrolyte secondary battery)
A nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 except that the electrolyte solution 5 was used instead of the electrolyte solution 1. The produced non-aqueous electrolyte secondary battery was designated as non-aqueous electrolyte secondary battery 5.

  Thereafter, the cycle characteristics of the nonaqueous electrolyte secondary battery 5, that is, the capacity retention rate (%) after 100 cycles were measured. The results are shown in Table 1.

[Example 6]
[Manufacture of separators for non-aqueous electrolyte secondary batteries]
A polyolefin porous film was obtained in the same manner as in Example 1 except that the sheet washed with the washing liquid (heptane) was dried and heat-set at 134 ° C. for 16 minutes. The obtained polyolefin porous film was used as the separator 2 for a nonaqueous electrolyte secondary battery.

  Then, the physical property of the separator 2 for nonaqueous electrolyte secondary batteries was measured with the above-mentioned measuring method. The nonaqueous electrolyte secondary battery separator 2 had a film thickness of 12 μm and an air permeability of 124 sec / 100 mL. Table 1 shows the measured physical properties of the separator 2 for a non-aqueous electrolyte secondary battery.

[Preparation of non-aqueous electrolyte secondary battery]
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that the separator 2 for a nonaqueous electrolyte secondary battery was used instead of the separator 1 for a nonaqueous electrolyte secondary battery. The produced non-aqueous electrolyte secondary battery was designated as non-aqueous electrolyte secondary battery 6.

  Thereafter, the cycle characteristics of the nonaqueous electrolyte secondary battery 6, that is, the capacity retention rate (%) after 100 cycles were measured. The results are shown in Table 1.

[Example 7]
[Preparation of non-aqueous electrolyte secondary battery]
(Preparation of electrolyte)
20 μL of the additive solution 1 and 1980 μL of the electrolyte solution stock solution 1 were mixed to obtain an electrolyte solution 6.

(Assembly of non-aqueous electrolyte secondary battery)
A nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 except that the electrolyte solution 6 was used instead of the electrolyte solution 1. The produced non-aqueous electrolyte secondary battery was designated as non-aqueous electrolyte secondary battery 7.

  Thereafter, the cycle characteristics of the nonaqueous electrolyte secondary battery 7, that is, the capacity retention rate (%) after 100 cycles were measured. The results are shown in Table 1.

[Example 8]
[Preparation of non-aqueous electrolyte secondary battery]
(Preparation of electrolyte)
50 μL of the electrolyte solution 6 and 1950 μL of the electrolyte solution stock solution 1 were mixed to obtain an electrolyte solution 7.

(Assembly of non-aqueous electrolyte secondary battery)
A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that the electrolyte solution 7 was used instead of the electrolyte solution 1. The produced non-aqueous electrolyte secondary battery was designated as non-aqueous electrolyte secondary battery 8.

  Thereafter, the cycle characteristics of the nonaqueous electrolyte secondary battery 8, that is, the capacity retention rate (%) after 100 cycles were measured. The results are shown in Table 1.

[Example 9]
[Preparation of non-aqueous electrolyte secondary battery]
(Preparation of electrolyte)
LiPF ₆ was dissolved in a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a ratio of 3: 7 (volume ratio) so that the concentration of LiPF ₆ was 1 mol / L to obtain an electrolyte solution stock solution 2. 90 μL of additive solution 1 and 1910 μL of electrolyte solution stock solution 2 were mixed to prepare electrolyte solution 8.

(Assembly of non-aqueous electrolyte secondary battery)
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that the electrolyte solution 8 was used instead of the electrolyte solution 1. The produced non-aqueous electrolyte secondary battery was designated as non-aqueous electrolyte secondary battery 9.

  Thereafter, the cycle characteristics of the nonaqueous electrolyte secondary battery 9, that is, the capacity retention rate (%) after 100 cycles were measured. The results are shown in Table 1.

[Example 10]
[Preparation of non-aqueous electrolyte secondary battery]
(Preparation of electrolyte)
LiPF ₆ is dissolved in a mixed solvent in which ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate are mixed at a 4: 4: 2 (volume ratio) so that the concentration of LiPF ₆ is 1 mol / L. did. 90 μL of the additive solution 1 and 1910 μL of the electrolyte solution stock solution 3 were mixed to obtain an electrolyte solution 9.

(Assembly of non-aqueous electrolyte secondary battery)
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that the electrolyte solution 9 was used instead of the electrolyte solution 1. The produced non-aqueous electrolyte secondary battery was designated as non-aqueous electrolyte secondary battery 10.

  Thereafter, the cycle characteristics of the nonaqueous electrolyte secondary battery 10, that is, the capacity retention rate (%) after 100 cycles were measured. The results are shown in Table 1.

[Example 11]
[Preparation of non-aqueous electrolyte secondary battery]
(Preparation of electrolyte)
LiPF ₆ is dissolved in a mixed solvent obtained by mixing ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate in a ratio of 2: 5: 3 (volume ratio) so that the concentration of LiPF ₆ is 1 mol / L. did. 90 μL of the additive solution 1 and 1910 μL of the electrolyte solution stock solution 4 were mixed to obtain an electrolyte solution 10.

(Assembly of non-aqueous electrolyte secondary battery)
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that the electrolyte solution 10 was used instead of the electrolyte solution 1. The produced non-aqueous electrolyte secondary battery was designated as non-aqueous electrolyte secondary battery 11.

  Thereafter, the cycle characteristics of the nonaqueous electrolyte secondary battery 11, that is, the capacity retention rate (%) after 100 cycles were measured. The results are shown in Table 1.

[Comparative Example 1]
[Manufacture of separators for non-aqueous electrolyte secondary batteries]
Ultra-high molecular weight polyethylene powder (Hi-Zex Million 145M, Mitsui Chemicals Co., Ltd.) 20 parts by weight, petroleum resin is not added, and the temperature inside the biaxial kneader immediately before adding liquid paraffin to the biaxial kneader is 134 ° C. A porous polyolefin film was obtained in the same manner as in Example 1 except that the above was set. The obtained polyolefin porous film was used as a separator 3 for a non-aqueous electrolyte secondary battery.

  Then, the physical property of the separator 3 for nonaqueous electrolyte secondary batteries was measured with the above-mentioned measuring method. The nonaqueous electrolyte secondary battery separator 3 had a film thickness of 24 μm and an air permeability of 160 sec / 100 mL. Table 1 shows the measured physical properties of the non-aqueous electrolyte secondary battery separator 3.

[Preparation of non-aqueous electrolyte secondary battery]
(Preparation of electrolyte)
Diethyl carbonate was added to 10.0 mg of the additive triethyl phosphate (rate of decrease in ionic conductivity: 2.3%), dissolved, and made up to 5 mL. 45 μL of the additive solution 4 and 1955 μL of the electrolyte solution stock solution 1 were mixed to obtain an electrolyte solution 11.

(Assembly of non-aqueous electrolyte secondary battery)
Example 1 was used except that the separator 3 for a non-aqueous electrolyte secondary battery was used instead of the separator 1 for a non-aqueous electrolyte secondary battery and the electrolyte 11 was used instead of the electrolyte 1. A non-aqueous electrolyte secondary battery was manufactured. The produced non-aqueous electrolyte secondary battery was designated as non-aqueous electrolyte secondary battery 12.

  Thereafter, the cycle characteristics of the nonaqueous electrolyte secondary battery 12, that is, the capacity retention rate (%) after 100 cycles were measured. The results are shown in Table 1.

[Comparative Example 2]
[Preparation of non-aqueous electrolyte secondary battery]
(Preparation of electrolyte)
180 μL of the additive solution 4 and 1820 μL of the electrolyte solution stock solution 1 were mixed to obtain an electrolyte solution 12.

(Assembly of non-aqueous electrolyte secondary battery)
Example 1 was used except that the separator 3 for a non-aqueous electrolyte secondary battery was used instead of the separator 1 for a non-aqueous electrolyte secondary battery and the electrolyte 12 was used instead of the electrolyte 1. A non-aqueous electrolyte secondary battery was manufactured. The manufactured non-aqueous electrolyte secondary battery was designated as non-aqueous electrolyte secondary battery 13.

  Thereafter, the cycle characteristics of the non-aqueous electrolyte secondary battery 13, that is, the capacity retention rate (%) after 100 cycles were measured. The results are shown in Table 1.

[Comparative Example 3]
[Preparation of non-aqueous electrolyte secondary battery]
Except for using the separator 3 for a nonaqueous electrolyte secondary battery instead of the separator 1 for a nonaqueous electrolyte secondary battery and using the electrolyte 2 prepared in Example 2 instead of the electrolyte 1, A nonaqueous electrolyte secondary battery was produced in the same manner as Example 1. The produced non-aqueous electrolyte secondary battery was designated as non-aqueous electrolyte secondary battery 14.

  Thereafter, the cycle characteristics of the non-aqueous electrolyte secondary battery 14, that is, the capacity retention rate (%) after 100 cycles were measured. The results are shown in Table 1.

[Comparative Example 4]
[Preparation of non-aqueous electrolyte secondary battery]
(Preparation of electrolyte)
As an additive, 10.8 mg of tris- (4-tert-butyl-2,6-di-methyl-3-hydroxybenzyl) isocyanurate (ionic conductivity lowering rate: 6.1%) was used as the additive. Diethyl carbonate was added and dissolved to make 5 mL. 90 μL of the additive solution 5 and 1910 μL of the electrolyte solution stock solution 1 were mixed to obtain an electrolyte solution 13.

(Assembly of non-aqueous electrolyte secondary battery)
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that the electrolyte solution 13 was used instead of the electrolyte solution 1. The manufactured non-aqueous electrolyte secondary battery was designated as non-aqueous electrolyte secondary battery 15.

  Thereafter, the cycle characteristics of the non-aqueous electrolyte secondary battery 15, that is, the capacity retention rate (%) after 100 cycles were measured. The results are shown in Table 1.

[Comparative Example 5]
[Preparation of non-aqueous electrolyte secondary battery]
A nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 except that the separator 3 for a nonaqueous electrolyte secondary battery was used instead of the separator 1 for a nonaqueous electrolyte secondary battery. The manufactured non-aqueous electrolyte secondary battery was designated as non-aqueous electrolyte secondary battery 16.

  Thereafter, the cycle characteristics of the nonaqueous electrolyte secondary battery 16, that is, the capacity retention rate (%) after 100 cycles were measured. The results are shown in Table 1.

[Comparative Example 6]
[Preparation of non-aqueous electrolyte secondary battery]
(Preparation of electrolyte)
400 μL of the additive solution 1 and 1600 μL of the electrolyte solution stock solution 1 were mixed to obtain an electrolyte solution 14.

(Assembly of non-aqueous electrolyte secondary battery)
A nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 except that the electrolyte solution 14 was used instead of the electrolyte solution 1. The manufactured non-aqueous electrolyte secondary battery was designated as non-aqueous electrolyte secondary battery 17.

  Thereafter, the cycle characteristics of the nonaqueous electrolyte secondary battery 17, that is, the capacity retention rate (%) after 100 cycles were measured. The results are shown in Table 1.

[Comparative Example 7]
[Preparation of non-aqueous electrolyte secondary battery]
(Assembly of non-aqueous electrolyte secondary battery)
A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that the electrolyte solution stock solution 1 was used instead of the electrolyte solution 1. The produced non-aqueous electrolyte secondary battery was designated as non-aqueous electrolyte secondary battery 18.

  Thereafter, the cycle characteristics of the nonaqueous electrolyte secondary battery 18, that is, the capacity retention rate (%) after 100 cycles were measured. The results are shown in Table 1.

[result]
Physical property values of non-aqueous electrolyte secondary battery separators used in Examples 1 to 7 and Comparative Examples 1 to 7 (ion permeation barrier energy per unit film thickness, unit: J / mol / μm), ion conductivity Decreasing rate, content of additive in electrolyte solution (described as “content of additive” in the table), and cycle characteristics of non-aqueous electrolyte secondary battery (capacity maintenance rate after 100 cycles, unit: %) Is shown in Table 1 below.

  The nonaqueous electrolyte secondary battery manufactured in Examples 1 to 11 has an ion permeation barrier energy per unit film thickness of 300 J / mol / μm or more and 900 J / mol / μm or less. Containing 0.5 ppm or more and 300 ppm or less of an additive having a decrease in ionic conductivity of 1.0% or more and 6.0% or less of a reference electrolyte solution when dissolved for 1.0 wt% A non-aqueous electrolyte solution is provided. In the non-aqueous electrolyte secondary batteries manufactured in Comparative Examples 1 to 7, one of the ion permeation barrier energy per unit film thickness, the ion conductivity reduction rate, and the content of the additive is out of the above range. It is. From the results shown in Table 1, the non-aqueous electrolyte secondary batteries produced in Examples 1 to 11 are superior in cycle characteristics than the non-aqueous electrolyte secondary batteries produced in Comparative Examples 1 to 7, It turned out that the fall of the battery characteristic accompanying charging / discharging can be suppressed more.

  The non-aqueous electrolyte secondary battery according to one embodiment of the present invention is excellent in cycle characteristics, and therefore can be suitably used as a battery used in personal computers, mobile phones, personal digital assistants, and the like, and in-vehicle batteries. .

Claims (2)

A separator for a nonaqueous electrolyte secondary battery having an ion permeation barrier energy per unit film thickness of 300 J / mol / μm or more and 900 J / mol / μm or less;
A non-aqueous electrolyte containing 0.5 ppm or more and 300 ppm or less of an additive having an ionic conductivity reduction rate L represented by the following formula (A) of 1.0% or more and 6.0% or less. Water electrolyte secondary battery.
L = (LA−LB) / LA (A)
(In Formula (A), LA is LiPF such that the concentration of LiPF ₆ is 1 mol / L in a mixed solvent containing ethylene carbonate / ethyl methyl carbonate / diethyl carbonate = 3/5/2 (volume ratio)). ₆ represents the ionic conductivity (mS / cm) of the reference electrolyte in which ₆ is dissolved,
LB represents the ionic conductivity (mS / cm) of the electrolytic solution obtained by dissolving 1.0% by weight of the additive in the reference electrolytic solution. )   The nonaqueous electrolyte secondary battery according to claim 1, wherein the capacity retention rate after 100 cycles is 90% or more.