JP2012054147A - Negative electrode for nonaqueous electrolyte battery and nonaqueous electrolyte battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the amount of a binder while suppressing degradation in battery characteristic.SOLUTION: A negative electrode active material layer contains a negative electrode active material and a binder. The binder is a mixture of a polyacrylonitrile resin having an electrolyte-swelling property of 200 wt.% or lower and a B-type viscosity of 1000 mPa s or higher, and a polyvinylidene fluoride having an electrolyte-swelling property of 200 wt.% or higher and a B-type viscosity of 1000 mPa s or higher. The polyacrylonitrile resin comprises a homopolymer of (meth-) acrylonitrile; a copolymer of (meth-) acrylonitrile and other monomers, or a modified product from the copolymer. The mixing ratio of the polyacrylonitrile resin to the polyvinylidene fluoride is preferably in the range of 90:10 to 10:90 by weight, and the total amount of addition of the binder obtained by mixing the polyacrylonitrile resin and the polyvinylidene fluoride is preferably in the range of 1 to 5 wt.% of a negative electrode mixture.

Description

  The present invention relates to, for example, a negative electrode for a non-aqueous electrolyte battery and a non-aqueous electrolyte battery, and more particularly to a negative electrode for a non-aqueous electrolyte battery and a non-aqueous electrolyte battery containing polyacrylonitrile and polyvinylidene fluoride as binders contained in the negative electrode.

  In recent years, portable electronic devices such as a camera-integrated VTR (video tape recorder), a mobile phone, or a laptop computer have been widely used, and there is a strong demand for miniaturization, weight reduction, and long life. Accordingly, as a power source for portable electronic devices, development of a battery, in particular, a secondary battery that is lightweight and can obtain a high energy density and a high output density is in progress.

  For example, lithium ion secondary batteries are widely used as such secondary batteries. A lithium ion secondary battery has a structure in which a positive electrode and a negative electrode are stacked or wound via a resin thin film separator as a diaphragm, and contains an electrolyte composed of an electrolyte salt and a nonaqueous solvent.

  An electrode used for a battery such as a lithium ion secondary battery usually has a structure in which an active material layer is formed on a current collector made of a band-shaped metal or the like. In this electrode, an active material layer is generally formed on a current collector by applying and drying a coating liquid in which at least an active material and a binder are dispersed or dissolved in a solvent on the current collector. It is. Since this manufacturing method can manufacture a large-area electrode at a time, it is industrially highly productive. As the binder, a polymer compound is usually used, and polyvinylidene fluoride (PVdF), styrene butadiene rubber (SBR), and the like have been widely used.

  When a carbon-based active material is used in the negative electrode, highly crystalline natural graphite or artificial graphite is used from the viewpoint of increasing the capacity of the battery. Natural graphite has a capacity close to the theoretical capacity of graphite, but since its specific surface area is generally larger than that of artificial graphite, binders such as vinylidene fluoride (PVdF) and styrene butadiene rubber (SBR) are used. In many cases, the adhesion of the negative electrode current collector is not sufficient, which causes problems such as a decrease in productivity and an increase in the electrode defect rate. In order to improve the adhesion between the negative electrode current collector and the negative electrode active material layer, the adhesion can be improved by increasing the amount of vinylidene fluoride (PVdF) or styrene butadiene rubber (SBR). As the amount of vinylidene fluoride (PVdF) and styrene butadiene rubber (SBR) having a large amount of is increased, Li ion insertion inhibition and capacity reduction during charging are caused.

  On the other hand, since artificial graphite generally has a specific surface area smaller than that of natural graphite, even if a binder such as PVdF is used, the adhesion to the negative electrode current collector can be ensured. Since it is lower than natural graphite, it is difficult to increase the capacity of the battery. Thus, it has been difficult to achieve both high battery capacity and high productivity.

  As a binder that satisfies the above-described requirements, for example, as in Patent Document 1 and Patent Document 2 below, an acrylic copolymer formed mainly from (meth) acrylic ester and (meth) acrylonitrile is used. A binding agent has been proposed. This binder made of an acrylic copolymer is disclosed as an alternative to vinylidene fluoride (PVdF) or styrene butadiene rubber (SBR). Binders composed of these acrylonitrile copolymers have the characteristics that they are excellent in electrochemical stability in the battery, particularly oxidation resistance, and can be used in a reduced amount.

  In Patent Document 3, an acrylic copolymer having a polymerization unit of (meth) acrylic acid ester and / or (meth) acrylonitrile as a main component, and a vinylidene fluoride-based heavy polymer having a weight average molecular weight of 250,000 or more. A binder formed from coalescence is disclosed. The binder of Patent Document 3 is disclosed as having a high adhesive property and capable of forming a slurry suitable for application.

  Further, in Patent Document 4, a binder obtained by mixing an emulsion latex of an acrylic copolymer and polyvinylidene fluoride (PVdF) is used.

JP-A-8-287915 JP 2001-332265 A JP 2003-317722 A Japanese Patent No. 4361241

  However, since the binder shown in Patent Document 1 and Patent Document 2 alone inhibits Li ion permeation, the charge / discharge characteristics at a high rate are deteriorated or a slurry suitable for coating cannot be formed. was there.

  Moreover, since the acrylic copolymer of the said invention exists as a particle | grain in a dispersion medium, since the binder shown in patent document 3 has a low thickening effect | action, there are many in order to obtain a stable slurry. The amount of binder is required. As a result, problems such as obstructing the permeation of Li ions and causing deterioration of cell capacity, cycle characteristics and the like have been serious. In addition, since polyvinylidene fluoride swells in the electrolyte widely used in nonaqueous electrolyte secondary batteries, the binder swells when cycled or stored at high temperatures for a long period of time. As a result of insufficient adhesion between the materials and between the active materials, there is a problem that the conductive path is hindered and the characteristics are greatly deteriorated due to deterioration over time.

  Further, in Patent Document 4, since the binder is an emulsion latex, it is difficult to suppress the expansion of polyvinylidene fluoride (PVdF) due to the electrolytic solution, and it is difficult to maintain the contact between the negative electrode active materials. there were.

  The present application has been made in view of such problems, and an object thereof is to achieve both high battery capacity and high productivity.

In order to solve the problem, the negative electrode for a nonaqueous electrolyte battery of the present application has a negative electrode active material layer formed on a negative electrode current collector,
The negative electrode active material layer contains a negative electrode active material and a binder,
The binder has a polyacrylonitrile-based resin having an electrolytic solution swelling resistance of 200% by weight or less and a B-type viscosity of 1000 mPa · s or more, an electrolytic solution swelling resistance of 200% by weight or more, and a B-type. Polyvinylidene fluoride having a viscosity of 1000 mPa · s or more is contained.

The nonaqueous electrolyte battery of the present application includes a positive electrode, a negative electrode, and a nonaqueous electrolyte,
The negative electrode has a negative electrode active material layer formed on a negative electrode current collector,
The negative electrode active material layer contains a negative electrode active material and a binder,
The binder has a polyacrylonitrile-based resin having an electrolytic solution swelling resistance of 200% by weight or less and a B-type viscosity of 1000 mPa · s or more, an electrolytic solution swelling resistance of 200% by weight or more, and a B-type. Polyvinylidene fluoride having a viscosity of 1000 mPa · s or more is contained.

  The swelling property was prepared from a solution in which each of polyacrylonitrile (PAN) and polyvinylidene fluoride (PVdF) was dissolved in N-methyl-2-pyrrolidone (NMP) so as to have a concentration of 10% by weight. The film was immersed in a non-aqueous electrolyte and obtained from the weight ratio of each film before and after immersion.

  The viscosity is the B-type viscosity of a solution obtained by dissolving polyacrylonitrile (PAN) and polyvinylidene fluoride (PVdF) in N-methyl-2-pyrrolidone (NMP) so as to have a concentration of 10% by weight. It is.

  In the non-aqueous electrolyte battery negative electrode and non-aqueous electrolyte battery described above, the polyacrylonitrile resin and the polyvinylidene fluoride as described above are mixed and used as a binder, so that the polyvinylidene fluoride expands with the non-aqueous electrolyte. Can be suppressed.

  According to this application, the usage-amount of a binder can be made small, and deterioration of a battery characteristic can be suppressed.

It is sectional drawing which shows one structural example of the nonaqueous electrolyte battery by the 2nd Embodiment of this invention. It is sectional drawing which shows the electrode laminated structure of the wound electrode body shown in FIG. It is an approximate line figure showing an example of 1 composition of a nonaqueous electrolyte battery by a 3rd embodiment of this invention. It is sectional drawing along the II-II line | wire of FIG. 3 which shows the electrode laminated structure of the winding electrode body shown in FIG. It is sectional drawing which shows the other battery form which can apply this invention.

Hereinafter, the best mode for carrying out the invention (hereinafter referred to as an embodiment) will be described. The description will be made as follows.
1. First embodiment (an example of a negative electrode using the binder of the present application)
2. Second embodiment (an example of a nonaqueous electrolyte battery including a negative electrode using the binder of the present application)
3. Third embodiment (example using a laminate film type non-aqueous electrolyte battery)
4). Other embodiments

1. First Embodiment Hereinafter, a negative electrode according to a first embodiment of the present application will be described.

(1-1) Binder The binder used for the negative electrode in the first embodiment has the following configuration.

(Ii) containing both polyacrylonitrile-based resin (hereinafter referred to as polyacrylonitrile (PAN) as appropriate) and polyvinylidene fluoride (PVdF) (ii) anti-electrolyte swelling resistance of polyacrylonitrile (PAN) is 200 wt% Preferably, it is 180 weight% or less, More preferably, it is 150 weight% or less. Moreover, the electrolytic solution swelling resistance of polyvinylidene fluoride (PVdF) is 200% by weight or more, preferably 250% by weight or more.
(Iii) The B-type viscosities of polyacrylonitrile (PAN) and polyvinylidene fluoride (PVdF) are 1000 mPa · s or more, preferably 2000 mPa · s or more, and more preferably 3000 mPa · s or more.

About (i) As the above-mentioned polyacrylonitrile (PAN), a homopolymer of (meth) acrylonitrile, a copolymer of (meth) acrylonitrile and other monomers, or a modified product of this copolymer can be used. Polyacrylonitrile (PAN) is excellent in electrochemical stability and can sufficiently obtain the effect as a binder with a small addition amount. Moreover, it has the property which is hard to swell with respect to the nonaqueous electrolyte injected into the inside of a battery. On the other hand, polyvinylidene fluoride (PVdF) is easily swelled with respect to the nonaqueous electrolyte, but has a property of not inhibiting lithium ion permeability. For this reason, polyacrylonitrile (PAN) physically suppresses the expansion of polyvinylidene fluoride (PVdF) with respect to the non-aqueous electrolyte by mixing and using polyacrylonitrile (PAN) and polyvinylidene fluoride (PVdF). That is, polyacrylonitrile (PAN) is interspersed, and the negative electrode active materials are bonded to each other within the negative electrode active material layer, or the conductive agent added as necessary and the negative electrode active material or the conductive agent are bonded. A strong network is formed. For this reason, the expansion of polyvinylidene fluoride (PVdF) can be suppressed.

  The polyacrylonitrile (PAN) used in the present invention is preferably represented by the following structural formula (Chemical Formula 1).

(Chemical formula 1)
_{(CH 2 -CHCN) x - (} CH 2 -CHR) y - (CH 2 -CHNH 2) z
(Wherein, R _{COO (CH 2) m -O (} CH 2) n CH 3, (CH 2) m -O (CH 2) n CH 3, COO- (CH 2 CH 2 -O) m CH 3 , And CH ₂ COOH and COOH, and m and n are 0 or more and 10 or less, and x, y, and z are the proportion of each monomer unit in the formula (unit: mass%). X> 90, y> 2 and z <1, preferably x> 92, y> 2 and z <1, more preferably x> 95, y> 2, z <0.5. .)

In the above (Chemical Formula 1), when there are few monomer units of (CH ₂ —CHCN), it is preferable that x> 90 since adhesion cannot be sufficiently provided. In addition, in the above (Chemical Formula 1), when there are few monomer units of (CH ₂ —CHR), it is preferable that y> 2 since adhesion between the current collector and the active material layer cannot be imparted. Furthermore, in the above (Chemical Formula 1), when there are too many monomer units of (CH ₂ —CHNH ₂ ), the resistance is large and the secondary battery is deteriorated. Therefore, z <2 is preferable.

About (ii) In this application, in order to obtain the polyvinylidene fluoride (PVdF) expansion suppression effect described in (i), the swelling property of polyvinylidene fluoride (PVdF) and low-expansion polyacrylonitrile (PAN) is defined. ing. In particular, polyacrylonitrile (PAN) has an electrolyte solution swell resistance of 200% by weight or less, and such polyacrylonitrile (PAN) having a structure of (Chemical Formula 1) is preferable. Moreover, the expansibility of polyvinylidene fluoride (PVdF) is general.

  When the swellability of polyacrylonitrile (PAN) is too high, the electrical conductivity between the active materials decreases, the resistance increases, and the battery characteristics deteriorate. Moreover, when the swelling property of polyvinylidene fluoride (PVdF) is too low, the lithium ion permeability is hindered and the load characteristics of the battery are deteriorated.

The electrolytic solution swell resistance in (ii) is obtained by dissolving each of polyacrylonitrile (PAN) and polyvinylidene fluoride (PVdF) in N-methyl-2-pyrrolidone (NMP) so as to have a concentration of 10% by weight, Coat the substrate. Then, it puts into a 130 degreeC hot air dryer, dries, peels, and produces a polyacrylonitrile (PAN) film and a polyvinylidene fluoride (PVdF) film. The polyacrylonitrile (PAN) film and the polyvinylidene fluoride (PVdF) film are immersed in a nonaqueous electrolytic solution at 23 ° C. for 7 days, and then the surface electrolytic solution is wiped off and the respective weights are measured. Finally, the electrolyte swellability using the weight ratio before and after immersion is calculated from the following formula.
Electrolyte swellability [%] = (weight before immersing electrolyte / weight after immersing electrolyte) × 100

In addition, the swelling property with respect to the electrolyte solution is 1:30: vinylene carbonate (VC), ethylene carbonate (EC), fluoroethylene carbonate (FEC), diethyl carbonate (DEC), and propylene carbonate (PC). A non-aqueous electrolyte in which lithium hexafluorophosphate (LiPF ₆ ), which is an electrolyte salt, is dissolved at a concentration of 1.0 mol / kg with respect to a non-aqueous solvent mixed at a mass ratio of 10:49:10. is there.

About (iii) The polyacrylonitrile (PAN) of the present application is used together with polyvinylidene fluoride (PVdF) to have a thickening effect of a negative electrode mixture slurry in which a negative electrode mixture is dispersed in a solvent, and the viscosity of the negative electrode mixture slurry Can be increased. When the viscosity of the negative electrode mixture slurry is low, the applicability of the negative electrode mixture slurry to the negative electrode current collector is lowered.

  The type B viscosity in (iii) was determined by dissolving polyacrylonitrile (PAN) and polyvinylidene fluoride (PVdF) in N-methyl-2-pyrrolidone (NMP) so as to have a concentration of 10% by weight. It is measured with a B-type viscometer below.

  By having such a viscosity, the negative electrode mixture layer can be stably formed. That is, the negative electrode mixture slurry containing the negative electrode active material can be stably applied to the negative electrode current collector.

  The mixing ratio of the above-mentioned polyacrylonitrile (PAN) and polyvinylidene fluoride (PVdF) is preferably 90:10 to 10:90, more preferably 80:20 to 20:80, and still more preferably 70:30 to 60:40.

  When the amount of polyacrylonitrile (PAN) mixed is too large, lithium ion permeability is slightly lowered, leading to deterioration of cycle characteristics. Moreover, when there is too much mixing amount of a polyvinylidene fluoride (PVdF), it will become difficult to suppress the swelling of a polyvinylidene fluoride (PVdF), and the fall of a cycle characteristic and the binding property at the time of high temperature storage will arise. .

  In addition, the total amount of the binder mixed with the above-mentioned polyacrylonitrile (PAN) and polyvinylidene fluoride (PVdF) is the same as that of the negative electrode active material, the binder, and the conductive agent added as necessary. It is preferable that it is 1 to 5 weight% with respect to an agent. The total amount of the binder added is more preferably 1.5% by weight or more and 4% by weight or less, and further preferably 2% by weight or more and 3% by weight or less.

  When the total amount of the binder added is small, the effect as the binder is reduced. On the other hand, when the total amount of the binder added is too large, the lithium ion permeability is lowered and the cycle characteristics are lowered.

(1-2) Configuration of Negative Electrode The negative electrode is, for example, one in which a negative electrode active material layer is provided on both surfaces of a negative electrode current collector. The negative electrode current collector is made of a metal material such as copper (Cu), nickel (Ni), or stainless steel (SUS). The negative electrode active material layer includes a negative electrode active material and a binder, and may further include a conductive agent (for example, a carbon material) as necessary.

  The negative electrode active material contains any one or more of negative electrode materials capable of inserting and extracting lithium. Examples of the negative electrode material include carbon materials, metals, metal oxides, silicon, and polymer materials. The carbon material is any one of carbon materials such as non-graphitizable carbon, graphitizable carbon, graphites, pyrolytic carbons, cokes, glassy carbons, organic polymer compound fired bodies, carbon fibers and activated carbon. Species or two or more can be used.

  In particular, natural graphite, artificial graphite, and other graphites are rich in chemical stability, can repeatedly and stably undergo lithium ion deinsertion reactions, and are easily available industrially. Widely used. In addition, as a kind of graphite, artificial graphite, natural graphite, etc., such as mesophase carbon microbead (MCMB), carbon fiber, or coke, are mentioned, for example. A carbon material is preferable because the crystal structure changes very little with insertion and extraction of lithium, and also functions as a conductive agent.

When natural graphite is used, those having a spherical shape, those coated with low crystalline carbon, and those obtained by coating spherical natural graphite with low crystalline carbon and heat-treating it are preferred. In addition, a mesophase carbon microbead (MCMB), which is a kind of artificial graphite, is coated with low crystalline carbon and heat-treated. The capacity of graphite is preferably 350 mAh / g or more, and the specific surface area of graphite is preferably 0.5 m ² / g or more and 5 m ² / g or less. In particular, mesophase carbon microbeads (MCMB) have a smaller capacity than natural graphite, but have a small specific surface area, so that the amount of binder can be reduced.

  Moreover, as a negative electrode material, the material which contains at least 1 sort (s) of the metallic element and metalloid element which can form an alloy with lithium as a constituent element is mentioned, for example. This type of material is preferable because a high energy density can be obtained. This negative electrode material may be any of a simple substance, an alloy or a compound of a metal element or a metalloid element, and may have one or more of these phases at least in part. The alloys in the present invention include those containing one or more metal elements and one or more metalloid elements in addition to those composed of two or more metal elements. Of course, the alloy may contain non-metallic elements. This structure includes a solid solution, a eutectic (eutectic mixture), an intermetallic compound, or one in which two or more of them coexist.

  Examples of the material containing at least one of a metal element and a metalloid element as a constituent element include a material containing silicon or tin. This is because a high energy density can be obtained because the ability to occlude and release lithium is large. These may be used alone or in combination of two or more.

As a specific example of this material, it is preferable that tin is the first constituent element and that the second and third constituent elements are included in addition thereto. For example, SnO, SnO ₂ , or a metal composite oxide thereof is used. Can do. Moreover, the thing (CoSnC material) which contains tin, cobalt, and carbon as a structural element is preferable. This is because a higher energy density can be obtained and excellent cycle characteristics can be obtained. This CoSnC-containing material may further contain other constituent elements as necessary. This is because the battery capacity and cycle characteristics are further improved.

Further, a simple substance of silicon, or an alloy or compound containing silicon as the first constituent element and the second and third constituent elements in addition thereto is preferable. For example, SiO, SiO ₂ , or a metal composite oxide thereof is used. be able to.

  In this case, for example, the negative electrode active material layer 12B is formed by using a vapor phase method, a liquid phase method, a thermal spraying method, a firing method, or two or more of these methods, and the negative electrode active material layer 12B The anode current collector 12A is preferably alloyed at least at a part of the interface. This is because the negative electrode active material layer 12B is less likely to be destroyed due to expansion and contraction associated with charge / discharge, and the electron conductivity is improved between the negative electrode current collector 12A and the negative electrode active material layer 12B.

  As the vapor phase method, for example, physical deposition method or chemical deposition method, more specifically, vacuum vapor deposition method, sputtering method, ion plating method, laser ablation method, thermal chemical vapor deposition (CVD; Chemical Vapor Deposition). ) Method or plasma enhanced chemical vapor deposition. As the liquid phase method, a known method such as electroplating or electroless plating can be used. The firing method is, for example, a method in which a particulate negative electrode active material and a binder are mixed and dispersed in a solvent, followed by heat treatment at a temperature higher than the melting point of the binder or the like. A known method can be used for the firing method, and examples thereof include an atmospheric firing method, a reactive firing method, a hot press firing method, and the like.

  As the binder, the binder of (1-1) can be used.

(1-3) Method for Producing Negative Electrode A negative electrode active material and a binder in which the above-mentioned polyacrylonitrile (PAN) and polyvinylidene fluoride (PVdF) are mixed are uniformly mixed to form a negative electrode mixture. The mixture is dispersed in a solvent to form a slurry. Here, the negative electrode active material and the binder need only be uniformly dispersed, and the mixing ratio is not limited as long as the conditions such as the viscosity are within the above range. Moreover, you may add a electrically conductive agent as needed.

  Next, this slurry is uniformly applied on the negative electrode current collector by a doctor blade method or the like, and compressed and dried by a high-temperature roll press machine or the like to drive off the solvent, thereby forming a negative electrode active material layer. Here, the negative electrode active material layer may be provided on at least one surface of the negative electrode current collector. Finally, a negative electrode terminal is attached to an unformed portion of the negative electrode active material layer of the negative electrode current collector. Thereby, a negative electrode is produced.

〔effect〕
The negative electrode thus produced does not swell the negative electrode mixture layer with respect to the non-aqueous electrolyte when used in a battery, and has a high binding property between the negative electrode current collector and the negative electrode active material layer. can do.

2. Second Embodiment First, the configuration of a nonaqueous electrolyte battery according to an embodiment of the present invention will be described. FIG. 1 is a cross-sectional view showing one structural example of a nonaqueous electrolyte battery according to a second embodiment of the present invention. FIG. 2 is a cross-sectional view showing the electrode laminated structure of the nonaqueous electrolyte battery according to the first embodiment of the present invention.

  This non-aqueous electrolyte battery 20 is a so-called cylindrical type, in which a strip-shaped positive electrode 11 and a strip-shaped negative electrode 12 are wound through a separator 13 inside a substantially hollow cylindrical battery can 1. A rotating electrode body 10 is provided.

(2-1) Structure of Nonaqueous Electrolyte Battery The separator 13 is impregnated with an electrolytic solution that is a liquid electrolyte. The battery can 1 is made of, for example, iron (Fe) plated with nickel (Ni), and has one end closed and the other end open. Inside the battery can 1, a pair of insulating plates 2, 3 are arranged perpendicular to the winding peripheral surface so as to sandwich the winding electrode body 10.

  A battery lid 4, a safety valve mechanism 5 and a heat sensitive resistance (PTC: Positive Temperature Coefficient) element 6 provided inside the battery lid 4 are caulked through a gasket 7 at the open end of the battery can 1. It is attached by being. Thereby, the inside of the battery can 1 is sealed.

  The battery lid 4 is made of, for example, the same material as the battery can 1. The safety valve mechanism 5 is electrically connected to the battery lid 4 via the heat sensitive resistance element 6. The safety valve mechanism 5 is a current that cuts the electrical connection between the battery lid 4 and the wound electrode body 10 when the disk plate 5A is reversed when the internal pressure of the battery exceeds a certain level due to internal short circuit or external heating. It functions as a shut-off valve.

  The heat-sensitive resistance element 6 limits the current by increasing the resistance value when the temperature rises, and prevents abnormal heat generation due to a large current. The gasket 7 is made of, for example, an insulating material, and asphalt is applied to the surface.

  The wound electrode body 10 is wound around, for example, a center pin 14. A positive electrode lead 15 made of aluminum (Al) or the like is connected to the positive electrode 11 of the spirally wound electrode body 10, and a negative electrode lead 16 made of nickel (Ni) or the like is connected to the negative electrode 12. The positive electrode lead 15 is electrically connected to the battery cover 4 by being welded to the safety valve mechanism 5, and the negative electrode lead 16 is welded and electrically connected to the battery can 1.

  FIG. 2 is an enlarged cross-sectional view showing a part of the spirally wound electrode body 10 shown in FIG. The wound electrode body 10 is obtained by stacking and winding a positive electrode 11 and a negative electrode 12 with a separator 13 interposed therebetween.

[Positive electrode]
The positive electrode 11 is obtained by forming a positive electrode active material layer 11B containing a positive electrode active material on both surfaces of a positive electrode current collector 11A. As the positive electrode current collector 11A, for example, a metal foil such as an aluminum (Al) foil, a nickel (Ni) foil, or a stainless steel (SUS) foil can be used.

The positive electrode active material layer 11B includes, for example, a positive electrode active material, a conductive agent, and a binder. As the positive electrode active material, a metal oxide, a metal sulfide, or a specific polymer can be used depending on the type of the target battery. For example, in the case of constituting a lithium ion battery, Li _x MO ₂ (wherein M represents one or more transition metals, and x varies depending on the charge / discharge state of the battery, and is usually 0.05 or more and 1.10 or less. ) And a composite oxide of lithium and transition metal. As a transition metal constituting the lithium composite oxide, cobalt (Co), nickel (Ni), manganese (Mn), or the like is used.

Specific examples of such a lithium composite oxide include LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiNi _y Co _1-y O ₂ (0 <y <1). A solid solution in which a part of the transition metal element is substituted with another element can also be used. Examples thereof include LiNi _0.5 Co _0.5 O ₂ and LiNi _0.8 Co _0.2 O ₂ . These lithium composite oxides can generate a high voltage and have an excellent energy density.

_{Further, TiS 2, MoS 2, NbSe} 2, V 2 O 5 and lithium may be used without metal compound as a positive electrode active material. These positive electrode active materials may be used alone or in combination of two or more.

  Examples of the conductive agent include carbon materials such as graphite, carbon black, acetylene black, and ketjen black. These may be single and multiple types may be mixed. Note that the conductive agent may be a metal material or a conductive polymer as long as it is a conductive material.

  Examples of the binder include synthetic rubbers such as styrene butadiene rubber, fluorine rubber or ethylene propylene diene, and polymer materials such as polyvinylidene fluoride. These may be single and multiple types may be mixed.

  The positive electrode 11 has a positive electrode lead 15 connected to one end of the positive electrode current collector 11A by spot welding or ultrasonic welding. The positive electrode lead 15 is preferably a metal foil or a mesh-like one, but there is no problem even if it is not a metal as long as it is electrochemically and chemically stable and can conduct electricity. Examples of the material of the positive electrode lead 15 include aluminum (Al) and nickel (Ni).

[Negative electrode]
The negative electrode 12 has the same configuration as the negative electrode in the first embodiment, and a negative electrode active material layer 12B containing a negative electrode active material is formed on both surfaces of the negative electrode current collector 12A.

[Separator]
The separator 13 separates the positive electrode 11 and the negative electrode 12 and allows lithium ions to pass through while preventing a short circuit of current caused by contact between the two electrodes. Any separator may be used as long as it is electrically stable, chemically stable with respect to the positive electrode active material, the negative electrode active material or the solvent, and has no electrical conductivity. Good. For example, a polymer nonwoven fabric, a porous film, glass or ceramic fibers in a paper shape can be used, and a plurality of these may be laminated. In particular, a porous polyolefin film is preferably used, and a composite of this with a heat-resistant material made of polyimide, glass, ceramic fibers, or the like may be used. The separator 13 is impregnated with the electrolyte described above.

  In this non-aqueous electrolyte battery, when charged, for example, lithium ions are extracted from the positive electrode 11 and inserted in the negative electrode 12 through the electrolytic solution impregnated in the separator 13. On the other hand, when discharging is performed, for example, lithium ions are released from the negative electrode 12 and inserted into the positive electrode 11 through the electrolytic solution impregnated in the separator 13.

  According to this non-aqueous electrolyte battery, when the capacity of the negative electrode 12 is expressed based on insertion and extraction of lithium, the electrolyte solution according to the first embodiment described above is provided. The decomposition reaction of the liquid is suppressed. Therefore, it is possible to improve the cycle characteristics and the storage characteristics particularly during high temperature use.

[Non-aqueous electrolyte]
The nonaqueous electrolytic solution is obtained by dissolving an electrolyte salt in a nonaqueous solvent.

The electrolyte salt contains, for example, one or more light metal salts such as a lithium salt. Examples of the lithium salt include lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium perchlorate (LiClO ₄ ), lithium hexafluoroarsenate (LiAsF ₆ ), lithium tetraphenylborate _{(LiB (C 6 H 5)} 4), methanesulfonic acid lithium (LiCH ₃ SO _3), lithium trifluoromethanesulfonate (LiCF ₃ SO _3), tetrachloroaluminate lithium (LiAlCl _4), six Examples thereof include dilithium fluorosilicate (Li ₂ SiF ₆ ), lithium chloride (LiCl), and lithium bromide (LiBr). Among them, at least one selected from the group consisting of lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium perchlorate (LiClO ₄ ), and lithium hexafluoroarsenate (LiAsF ₆ ). One is preferable, and lithium hexafluorophosphate (LiPF ₆ ) is more preferable. This is because the resistance of the non-aqueous electrolyte is lowered. In particular, it is preferable to use lithium tetrafluoroborate (LiBF ₄ ) together with lithium hexafluorophosphate (LiPF ₆ ). This is because a high effect can be obtained.

  Examples of the non-aqueous solvent include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC). , Methylpropyl carbonate (MPC), γ-butyrolactone, γ-valerolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 1,3-dioxolane, 4-fluoro-1,3-dioxolane- 2-one, 4-methyl-1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, methyl isobutyrate, methyl trimethylacetate , Ethyl trimethylacetate, acetonitrile, glutaronitrile , Adiponitrile, methoxyacetonitrile, 3-methoxypropionitrile, N, N-dimethylformamide, N-methylpyrrolidinone, N-methyloxazolidinone, N, N'-dimethylimidazolidinone, nitromethane, nitroethane, sulfolane, trimethyl phosphate or Dimethyl sulfoxide or the like can be used. This is because, in an electrochemical device such as a battery provided with a nonaqueous electrolyte, excellent capacity, cycle characteristics and storage characteristics can be obtained. These may be used alone or in combination of two or more.

  Especially, as a solvent, what contains at least 1 sort (s) of the group which consists of ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC) is used. It is preferable. This is because a sufficient effect can be obtained. In this case, in particular, ethylene carbonate or propylene carbonate having a high viscosity (high dielectric constant) solvent (for example, relative dielectric constant ε ≧ 30) and dimethyl carbonate having a low viscosity solvent (for example, viscosity ≦ 1 mPa · s). It is preferable to use a mixture containing diethyl carbonate or ethyl methyl carbonate. This is because the dissociation property of the electrolyte salt and the ion mobility are improved, and thus higher effects can be obtained.

(2-2) Manufacturing method of nonaqueous electrolyte battery Next, the manufacturing method of a nonaqueous electrolyte battery is demonstrated.

[Production method of positive electrode]
A positive electrode active material, a binder, and a conductive agent are mixed to prepare a positive electrode mixture, and the positive electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone to prepare a mixed solution. Next, this positive electrode mixture slurry is applied to the positive electrode current collector 11A and dried, and then compression molded by a roll press or the like to form the positive electrode active material layer 11B, whereby the positive electrode 11 is obtained.

[Production method of negative electrode]
The negative electrode 12 can be produced in the same manner as in the first embodiment.

[Method for producing non-aqueous electrolyte]
A non-aqueous electrolyte can be obtained by dissolving a predetermined amount of electrolyte salt in a non-aqueous solvent.

[Assembly of cylindrical nonaqueous electrolyte battery]
The positive electrode lead 15 is attached to the positive electrode current collector 11A by welding or the like, and the negative electrode lead 16 is attached to the negative electrode current collector 12A by welding or the like. Thereafter, the positive electrode 11 and the negative electrode 12 are wound through the separator 33, and the front end portion of the positive electrode lead 15 is welded to the safety valve mechanism 5 and the front end portion of the negative electrode lead 16 is welded to the battery can 1.

  Then, the wound positive electrode 11 and negative electrode 12 are sandwiched between a pair of insulating plates 2 and 3 and housed inside the battery can 1. After the positive electrode 11 and the negative electrode 12 are housed in the battery can 1, a nonaqueous electrolyte is injected into the battery can 1 and impregnated in the separator 13.

  Thereafter, the battery lid 4 provided with the safety valve mechanism 5 and the heat sensitive resistance element 6 is fixed to the opening end portion of the battery can 1 by caulking through the gasket 7. As described above, the nonaqueous electrolyte battery shown in FIG. 1 is manufactured.

  According to the non-aqueous electrolyte battery using such a non-aqueous electrolyte, the effect of forming a film on the electrode surface is enhanced, and a stronger and more stable film can be formed. For this reason, the decomposition reaction of the electrolytic solution is suppressed, and a high battery capacity can be maintained even if the charge / discharge cycle proceeds in a low temperature environment and a high temperature environment. Moreover, in order to suppress decomposition | disassembly of electrolyte solution, the operating time of a current cutoff valve can be extended.

〔effect〕
In the non-aqueous electrolyte battery thus produced, the binder in the negative electrode mixture layer does not swell with respect to the non-aqueous electrolyte, and the binding property between the negative electrode current collector and the negative electrode active material layer Can be high. For this reason, a high battery characteristic can be acquired and the deterioration of the battery characteristic accompanying cycling and the deterioration of the battery characteristic in a high temperature environment can be suppressed.

3. Third Embodiment (3-1) Configuration of Nonaqueous Electrolyte Battery In the third embodiment, a nonaqueous electrolyte battery covered with a laminate film will be described.

  FIG. 3 is a cross-sectional view showing a configuration example of the nonaqueous electrolyte battery according to the third embodiment of the present invention. FIG. 4 shows the electrode laminated structure of the nonaqueous electrolyte battery according to the third embodiment of the present invention.

  This nonaqueous electrolyte battery has a configuration in which a wound electrode body 30 to which a positive electrode lead 31 and a negative electrode lead 32 are attached is housed in a film-like exterior member 21 and has a flat shape. . Each of the positive electrode lead 31 and the negative electrode lead 32 has a strip shape, for example, and is led out from the inside of the exterior member 21 to the outside, for example, in the same direction. The positive electrode lead 31 is made of a metal material such as aluminum (Al), and the negative electrode lead 32 is made of a metal material such as nickel (Ni).

[Exterior material]
The exterior member 21 is, for example, a laminate film having a structure in which a heat sealing layer, a metal layer, and an exterior resin layer are laminated in this order and bonded together by a lamination process or the like. The exterior member 21 has, for example, each outer edge portion adhered to each other by fusion bonding or an adhesive with the heat sealing layer side as the inner side.

  The heat-fusible layer is made of, for example, a polyolefin resin such as polyethylene, polypropylene, modified polyethylene, modified polypropylene, or a copolymer thereof. This is because moisture permeability can be lowered and airtightness is excellent. The metal layer is made of foil-like or plate-like aluminum, stainless steel, nickel, iron, or the like. The exterior resin layer may be made of, for example, the same resin as that of the heat fusion layer, or may be made of nylon or the like. This is because the strength against tearing and piercing can be increased. The exterior member 21 may include a layer other than the heat fusion layer, the metal layer, and the exterior resin layer.

  Between the exterior member 21 and the positive electrode lead 31 and the negative electrode lead 32, the adhesion film 22 for improving the adhesion between the positive electrode lead 31 and the negative electrode lead 32 and the inside of the exterior member 21 and preventing the entry of outside air. Has been inserted. The adhesion film 22 is made of a material having adhesion to the positive electrode lead 31 and the negative electrode lead 32. When the positive electrode lead 31 and the negative electrode lead 32 are made of the above-described metal material, it is preferable that the positive electrode lead 31 and the negative electrode lead 32 are made of a polyolefin resin such as polyethylene, polypropylene, modified polyethylene, or modified polypropylene.

  FIG. 4 is a cross-sectional view taken along line II-II of the spirally wound electrode body 30 shown in FIG. The wound electrode body 30 is formed by stacking and winding a positive electrode 33 and a negative electrode 34 with a separator 35 and an electrolyte 36, and the outermost periphery is protected by a protective tape 37.

[Positive electrode and negative electrode]
The positive electrode 33 and the negative electrode 34 in the third embodiment can use the same materials and configurations as the positive electrode 11 and the negative electrode 12 in the second embodiment.

[Nonaqueous electrolyte]
The same nonaqueous electrolyte as that described in the second embodiment can be used. Further, as shown in FIGS. 3 and 4, a gel-like non-aqueous electrolyte (hereinafter referred to as a gel electrolyte as appropriate) may be used. The gel electrolyte is preferable because high ion conductivity (for example, 1 ms / cm or more at room temperature) is obtained and liquid leakage is prevented. Hereinafter, the gel electrolyte will be described.

  The gel electrolyte includes a nonaqueous solvent, an electrolyte salt, and a matrix polymer that takes in the nonaqueous solvent and gels. As the non-aqueous solvent and the electrolyte salt, the same materials as those in the first embodiment can be used.

  Matrix polymers include, for example, polyacrylonitrile, polyvinylidene fluoride, copolymers of polyvinylidene fluoride and polyhexafluoropyrene, polytetrafluoroethylene, polyhexafluoropropylene, polyethylene oxide, polypropylene oxide, polyphosphazene, polysiloxane , Polyvinyl acetate, polyvinyl alcohol, polymethyl methacrylate, polyacrylic acid, polymethacrylic acid, styrene-butadiene rubber, nitrile-butadiene rubber, polystyrene or polycarbonate. These may be used alone or in combination.

  In particular, from the viewpoint of electrochemical stability, it is preferable to use polyacrylonitrile, polyvinylidene fluoride, polyhexafluoropropylene, polyethylene oxide, or the like. The addition amount of the polymer compound in the electrolytic solution varies depending on the compatibility between the two, but is preferably 5% by mass or more and 50% by mass or less.

  The composition of the non-aqueous electrolyte contained in the gel electrolyte is the same as the composition of the non-aqueous electrolyte in the first embodiment. The non-aqueous solvent referred to here is not only a liquid solvent but also an electrolyte. This is a broad concept including those having ionic conductivity capable of dissociating salts. Accordingly, when a polymer compound having ion conductivity is used, the polymer compound is also included in the solvent.

[Separator]
The separator 35 in the third embodiment can use the same material and configuration as the separator 13 in the second embodiment.

(3-2) Manufacturing method of nonaqueous electrolyte battery [Preparation of positive electrode and negative electrode]
The manufacturing method of the positive electrode 33 and the negative electrode 34 in 3rd Embodiment can use the manufacturing method similar to the positive electrode 11 and the negative electrode 12 in 1st and 2nd embodiment.

  This nonaqueous electrolyte battery is manufactured, for example, by the following three types of manufacturing methods (first to third manufacturing methods).

(3-2-1) First Manufacturing Method In the first manufacturing method, first, for example, the positive electrode current collector 33A is manufactured by a procedure similar to the procedure for manufacturing the positive electrode 11 of the second embodiment described above. The positive electrode 33 is produced by forming the positive electrode active material layer 33B on both sides. Further, the negative electrode active material layer 34B is formed on both surfaces of the negative electrode current collector 34A by the same procedure as that of the negative electrode 12 of the second embodiment described above, and the negative electrode 34 is manufactured.

  Subsequently, after preparing a precursor solution containing the nonaqueous electrolytic solution according to the first embodiment, the polymer compound, and the solvent and applying the precursor solution to the positive electrode 33 and the negative electrode 34, the solvent is volatilized to obtain the gel electrolyte 36. Form. Subsequently, the positive electrode lead 31 is attached to the positive electrode current collector 33A, and the negative electrode lead 32 is attached to the negative electrode current collector 34A.

  Subsequently, the positive electrode 33 and the negative electrode 34 on which the electrolyte 36 is formed are stacked via the separator 35 and then wound in the longitudinal direction, and a protective tape 37 is adhered to the outermost peripheral portion to produce the wound electrode body 30. To do. Finally, for example, after the wound electrode body 30 is sandwiched between two film-shaped exterior members 21, the outer edge portions of the exterior member 21 are bonded to each other by heat fusion or the like, so that the wound electrode body 30 is Encapsulate. At this time, the adhesion film 22 is inserted between the positive electrode lead 31 and the negative electrode lead 32 and the exterior member 21. Thereby, a nonaqueous electrolyte battery is completed.

(3-2-2) Second Manufacturing Method In the second manufacturing method, first, the positive electrode lead 31 is attached to the positive electrode 33 and the negative electrode lead 32 is attached to the negative electrode 34. Subsequently, after the positive electrode 33 and the negative electrode 34 are laminated and wound via the separator 35, a protective tape 37 is adhered to the outermost peripheral portion thereof, and a wound body that is a precursor of the wound electrode body 30. Is made.

  Subsequently, after sandwiching the wound body between the two film-like exterior members 21, the remaining outer peripheral edge portion excluding the outer peripheral edge portion on one side is adhered by heat fusion or the like, thereby forming a bag-like exterior The wound body is stored inside the member 21. Subsequently, a composition for an electrolyte comprising the nonaqueous electrolytic solution according to the first embodiment, a monomer that is a raw material for the polymer compound, a polymerization initiator, and, if necessary, other materials such as a polymerization inhibitor. Is prepared and injected into the bag-shaped exterior member 21, and then the opening of the exterior member 21 is sealed by heat fusion or the like. Finally, the gel electrolyte 36 is formed by thermally polymerizing the monomer to obtain a polymer compound. Thereby, a nonaqueous electrolyte battery is completed.

(3-2-3) Third production method In the third production method, first, except that the separator 35 coated with the polymer compound on both sides is used, the same as the second production method described above, A wound body is formed and stored inside the bag-shaped exterior member 21.

  Examples of the polymer compound applied to the separator 35 include a polymer containing vinylidene fluoride as a component, that is, a homopolymer, a copolymer, or a multi-component copolymer. Specifically, polyvinylidene fluoride, binary copolymers containing vinylidene fluoride and hexafluoropropylene as components, and ternary copolymers containing vinylidene fluoride, hexafluoropropylene and chlorotrifluoroethylene as components. Such as coalescence.

  The polymer compound may contain one or more other polymer compounds together with the polymer containing vinylidene fluoride as a component. Subsequently, after the non-aqueous electrolyte according to the first embodiment is prepared and injected into the exterior member 21, the opening of the exterior member 21 is sealed by heat sealing or the like. Finally, the exterior member 21 is heated while applying a load, and the separator 35 is brought into close contact with the positive electrode 33 and the negative electrode 34 through the polymer compound. As a result, the non-aqueous electrolyte is impregnated into the polymer compound, and the polymer compound is gelled to form the electrolyte 36, thereby completing the non-aqueous electrolyte battery.

〔effect〕
In the third embodiment, the same effects as those of the second embodiment can be obtained.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. The present invention is not limited to these examples.

<Example 1>
[Production of negative electrode]
Using natural graphite having a specific surface area of 3 m ² / g as the negative electrode active material, polyacrylonitrile (PAN) and polyvinylidene fluoride (PVdF) as the binder, and N-methyl-2-pyrrolidone (NMP) as the solvent, The mixture was homogeneously mixed to obtain a negative electrode mixture slurry. The binder used was PAN 1.2 wt%, PVdF 1.2 wt%, and a total of 2.4 wt% (PAN: PVdF = 50: 50) with respect to the negative electrode mixture.

In Example 1, the monomer unit of (CH ₂ —CN) is 96.7% by mass, the monomer unit of (CH ₂ —CH—COO (CH ₂ ) ₂ —OCH ₂ CH ₃ ) is 1% by mass, ( A PAN obtained by copolymerizing ₂ % by mass of monomer units of (CH ₂ —CH—COOH) and 0.3% by mass of monomer units of (CH ₂ CH—CONH ₂ ) was used.

  Here, the electrolytic solution swelling resistance of the binder measured by the following method was 120% by weight for PAN and 250% by weight for PVdF. Moreover, the viscosity of the binder measured by the following method was 8500 mPa · s for PAN and 3200 mPa · s for PVdF.

[Electrolytic solution swelling resistance of binder]
PAN and PVdF were each dissolved in N-methyl-2-pyrrolidone (NMP) to a concentration of 10% by weight, coated on the substrate, dried in a hot air dryer at 130 ° C., and peeled off. Thus, a PAN film and a PVdF film were prepared. This PAN film and PVdF film were immersed in a non-aqueous electrolyte at 23 ° C. for 7 days. After immersion, the electrolyte solution on the surface was wiped off, and the electrolyte swellability was calculated from the following equation using the weight ratio before and after immersion.
Electrolyte swellability [%] = (weight before immersing electrolyte / weight after immersing electrolyte) × 100

In addition, the non-aqueous electrolyte used at the time of the measurement of the swelling property with respect to electrolyte solution is vinylene carbonate (VC), ethylene carbonate (EC), fluoroethylene carbonate (FEC), diethyl carbonate (DEC), and propylene carbonate (PC). ) And a non-aqueous solvent mixed at a mass ratio of 1: 30: 10: 49: 10, lithium hexafluorophosphate (LiPF ₆ ) as an electrolyte salt was dissolved at a concentration of 1.0 mol / kg. What was done was used.

[Binder viscosity]
PAN and PVdF were dissolved in N-methyl-2-pyrrolidone (NMP) to a concentration of 10% by weight, and measured with a B-type viscometer in a 25 ° C. environment.

  Next, the obtained negative electrode mixture slurry was uniformly applied to both surfaces of a 12 μm-thick strip-shaped copper foil serving as a negative electrode current collector and dried to form a negative electrode mixture layer. This was cut into a shape with a width of 40 mm and a length of 650 mm to produce a negative electrode, and a negative electrode terminal made of nickel (Ni) was further attached.

  Here, the peel strength between the negative electrode active material layer and the negative electrode current collector measured by the following method was 10 mN / mm or more.

[Measurement of peel strength]
A double-sided tape was adhered to the negative electrode active material layer provided on the rugged copper foil, and the copper foil and the negative electrode active material layer were cut out together to obtain a test piece. Thereafter, the multi-sided tape of the double-sided tape attached to the test piece is fixed with a stainless steel plate, and the negative electrode active material layer is peeled off to half, and the double-sided tape and the copper foil as the negative electrode current collector are peeled off at 180 °. I let you.

[Production of positive electrode]
Using lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, carbon black as a conductive agent, polyvinylidene fluoride (PVdF) as a binder, and N-methyl-2-pyrrolidone (NMP) as a solvent, and homogeneously By mixing, a negative electrode mixture slurry was obtained.

  Next, the obtained positive electrode mixture slurry was uniformly applied to both surfaces of a 15 μm-thick strip-shaped aluminum foil serving as a positive current collector and dried to form a negative electrode mixture layer. This was cut into a shape having a width of 40 mm and a length of 650 mm to produce a negative electrode, and a positive electrode lead made of aluminum was further attached.

[Adjustment of non-aqueous electrolyte]
As a non-aqueous solvent, vinylene carbonate (VC), ethylene carbonate (EC), fluoroethylene carbonate (FEC), diethyl carbonate (DEC), and propylene carbonate (PC) are mixed at 1: 30: 10: 49: What was mixed by the mass ratio of 10 was used. Then, lithium hexafluorophosphate (LiPF ₆ ), which is an electrolyte salt, was dissolved in a nonaqueous solvent at a concentration of 1.0 mol / kg to obtain a nonaqueous electrolytic solution.

[Battery assembly]
The positive electrode and the negative electrode prepared as described above were laminated via a separator made of a microporous polyethylene film having a thickness of 22 μm and wound to prepare a wound electrode body. Subsequently, after inserting a center pin having a diameter of 3.0 mm into the gap in the center of the wound electrode body, both wound surfaces of the wound electrode body are sandwiched between a pair of insulating plates, and the negative electrode terminal is made of nickel-plated iron. Welded to the bottom of the battery can. The positive electrode lead was welded to a safety valve mechanism provided on the battery lid. Thereafter, the wound electrode body was accommodated in a battery can, and a non-aqueous electrolyte was injected. Finally, a cylindrical secondary battery was produced by caulking the battery lid to the battery can via a gasket.

<Example 2>
As in Example 1, except that PAN 1.4% by weight, PVdF 1.4% by weight, and a total of 2.8% by weight (PAN: PVdF = 50: 50) were used as the binder. Thus, a cylindrical secondary battery was produced. The electrolytic solution swelling resistance of each binder and the viscosity of each binder were the same as in Example 1. Further, the peel strength between the negative electrode active material layer and the negative electrode current collector was 10 mN / mm or more.

<Example 3>
Cylindrical as in Example 1, except that 2 wt% PAN, 0.5 wt% PVdF, and 2.5 wt% in total (PAN: PVdF = 80: 20) were used as the binder. A type secondary battery was produced. The electrolytic solution swelling resistance of each binder and the viscosity of each binder were the same as in Example 1. Further, the peel strength between the negative electrode active material layer and the negative electrode current collector was 10 mN / mm or more.

<Example 4>
Natural graphite having a specific surface area of 5 m ² / g is used as the negative electrode active material, and ² % by weight of PAN and 2% by weight of PVdF are used as the binder, and 4% by weight in total (PAN: PVdF = 50: 50). A cylindrical secondary battery was produced in the same manner as in Example 1 except that. The electrolytic solution swelling resistance of each binder and the viscosity of each binder were the same as in Example 1. Further, the peel strength between the negative electrode active material layer and the negative electrode current collector was 10 mN / mm or more.

<Example 5>
Natural graphite having a specific surface area of 5 m ² / g was used as the negative electrode active material, and the binder was 2.5 wt% PAN, 1 wt% PVdF, and 3.5 wt% in total (PAN: PVdF = 71: A cylindrical secondary battery was produced in the same manner as in Example 1 except that 29) was used. The electrolytic solution swelling resistance of each binder and the viscosity of each binder were the same as in Example 1. Further, the peel strength between the negative electrode active material layer and the negative electrode current collector was 10 mN / mm or more.

<Example 6>
Artificial graphite having a specific surface area of 0.5 m ² / g is used as the negative electrode active material, and 1% by weight of PAN, 2% by weight of PVdF, and 3% by weight in total as the binder (PAN: PVdF = 34: 66). A cylindrical secondary battery was produced in the same manner as in Example 1 except that was used. The electrolytic solution swelling resistance of each binder and the viscosity of each binder were the same as in Example 1. Further, the peel strength between the negative electrode active material layer and the negative electrode current collector was 10 mN / mm or more.

<Example 7>
A cylindrical secondary battery was produced in the same manner as in Example 1 except that artificial graphite having a specific surface area of 0.5 m ² / g was used as the negative electrode active material. The electrolytic solution swelling resistance of each binder and the viscosity of each binder were the same as in Example 1. Further, the peel strength between the negative electrode active material layer and the negative electrode current collector was 10 mN / mm or more.

<Example 8>
As in Example 1, except that PAN 1.4% by weight, PVdF 1.4% by weight, and a total of 2.8% by weight (PAN: PVdF = 50: 50) were used as the binder. Thus, a cylindrical secondary battery was produced. Here, the binder used in Example 9 was a PAN having the same structure as in Example 1 but having a different molecular weight. The electrolytic solution swelling resistance of each binder was the same as in Example 1.

The molecular weight of PAN has a certain degree of correlation with the viscosity of the PAN solution. If the molecular weight of the polymer having the same structure is large, the viscosity of the solution dissolved with the same solid content increases. The viscosity of the PAN solution of Example 8 was 2000 mPa · s, and PAN having a molecular weight smaller than that of Examples 1 to 7 was used. PVdF was the same as that of Example 1. Further, the peel strength between the negative electrode active material layer and the negative electrode current collector was 10 mN / mm or more.

<Example 9>
As in Example 1, except that PAN 1.4% by weight, PVdF 1.4% by weight, and a total of 2.8% by weight (PAN: PVdF = 50: 50) were used as the binder. Thus, a cylindrical secondary battery was produced. Here, the binder used in Example 9 was a PAN having the same structure as in Example 1 and Example 8, but having a different molecular weight. The electrolytic solution swelling resistance of each binder was the same as in Example 1. Further, the viscosity of the binder was PAN of 1400 mPa · s, which was PAN having a molecular weight smaller than that of Examples 1 to 8, and PVdF was the same as that of Example 1. Further, the peel strength between the negative electrode active material layer and the negative electrode current collector was 10 mN / mm or more.

<Example 10>
As in Example 1, except that PAN 1.4% by weight, PVdF 1.4% by weight, and a total of 2.8% by weight (PAN: PVdF = 50: 50) were used as the binder. Thus, a cylindrical secondary battery was produced. Here, as the binder used in Example 9, PVdF having the same structure as that of Example 1 and Example 8 and having a different molecular weight was used. The electrolytic solution swelling resistance of each binder was the same as in Example 1. Moreover, as for the viscosity of the binder, PAN was the same as in Example 1, PVdF was 1200 mPa · s, and PVdF having a molecular weight smaller than those of Examples 1 to 9 was used. Further, the peel strength between the negative electrode active material layer and the negative electrode current collector was 10 mN / mm or more.

<Comparative Example 1>
A cylindrical secondary battery was produced in the same manner as in Example 1 except that 3% by weight of PAN was used as the binder with respect to the negative electrode mixture. The PAN swelling resistance and the viscosity of the binder were the same as in Example 1. Further, the peel strength between the negative electrode active material layer and the negative electrode current collector was 10 mN / mm or more.

<Comparative example 2>
A cylindrical secondary battery was produced in the same manner as in Example 1 except that 4% by weight of PVdF was used as the binder with respect to the negative electrode mixture. The electrolytic solution swelling resistance of PVdF as a binder and the viscosity of the binder were the same as those in Example 1. Moreover, the peel strength between the negative electrode active material layer and the negative electrode current collector was less than 10 mN / mm.

<Comparative Example 3>
A cylindrical secondary battery was produced in the same manner as in Example 1 except that 5% by weight of PVdF was used as the binder with respect to the negative electrode mixture. The electrolytic solution swelling resistance of PVdF as a binder and the viscosity of the binder were the same as those in Example 1. Moreover, the peel strength between the negative electrode active material layer and the negative electrode current collector was less than 10 mN / mm.

<Comparative example 4>
Cylindrical secondary battery in the same manner as in Example 1 except that 4% by weight of PAN, 3% by weight of PVdF, and 7% by weight in total (PAN: PVdF = 57: 43) were used as the binder. Was made. The electrolytic solution swelling resistance of each binder and the viscosity of each binder were the same as in Example 1. Further, the peel strength between the negative electrode active material layer and the negative electrode current collector was 10 mN / mm or more.

<Comparative Example 5>
As in Example 1, except that PAN 2.5% by weight, PVdF 0.2% by weight, and a total of 2.7% by weight (PAN: PVdF = 93: 7) were used as the binder. Thus, a cylindrical secondary battery was produced. The electrolytic solution swelling resistance of each binder and the viscosity of each binder were the same as in Example 1. Further, the peel strength between the negative electrode active material layer and the negative electrode current collector was 10 mN / mm or more.

<Comparative Example 6>
As in Example 1, except that PAN 0.3 wt%, PVdF 3.5 wt%, and total 3.8 wt% (PAN: PVdF = 8: 92) were used as the binder. Thus, a cylindrical secondary battery was produced. The electrolytic solution swelling resistance of each binder and the viscosity of each binder were the same as in Example 1. Moreover, the peel strength between the negative electrode active material layer and the negative electrode current collector was less than 10 mN / mm.

<Comparative Example 7>
As the binder, PAN and PVdF having the same structure as in Example 1 and having a molecular weight smaller than that of Example 1 were used. The electrolytic solution swelling resistance of each binder was the same as in Example 1. The binder had a viscosity of 700 mPa · s for PAN and PVdF. In Comparative Example 7, when a cylindrical secondary battery was prepared in the same manner as in Example 1, a negative electrode mixture slurry that could be stably applied could not be obtained, and a cylindrical secondary battery could be obtained. There wasn't.

<Comparative Example 8>
A cylindrical secondary battery was produced in the same manner as in Example 1 except that PAN copolymerized with butadiene was used as the binder. In addition, the electrolytic solution swelling resistance of the binder was 220% by weight of PAN, and PVdF was the same as in Example 1. Further, regarding the viscosity of the binder, PAN was 1200 mPa · s, and PVdF was the same as in Example 1. Moreover, the peel strength between the negative electrode active material layer and the negative electrode current collector was less than 10 mN / mm.

(A) Cycle characteristic test Each of the produced cylindrical secondary batteries was charged and discharged, and the discharge capacity retention rate at the 300th cycle was measured. The charging was performed at a constant current of 0.7 C until the battery voltage reached 4.2 V, and then the charging was continued at a constant voltage of 4.2 V until the total charging time reached 4 hours. Discharge was performed at a constant current of 0.5 C until the battery voltage reached 3.0V. Note that 1 C is a current value at which the theoretical capacity can be discharged in one hour.

The discharge capacity retention ratio was determined from the following formula by the ratio of the discharge capacity at the 300th cycle to the discharge capacity at the first cycle, and was shown as a relative ratio.
Discharge capacity maintenance ratio [%] = (discharge capacity at 300th cycle / discharge capacity at the first cycle) × 100
○: Discharge capacity maintenance rate 80% or more △: Discharge capacity maintenance rate 60% or more ×: Discharge capacity maintenance rate 60% or less

(B) Storage test Each of the produced cylindrical secondary batteries was charged and discharged, and the discharge capacity retention rate after high-temperature storage was examined. The charging was performed at a constant current of 0.7 C until the battery voltage reached 4.2 V, and then the charging was continued at a constant voltage of 4.2 V until the total charging time reached 4 hours. This cylindrical secondary battery was stored for 15 days in an environment of 60 ° C., and discharged after 15 days until the battery voltage reached 3.0 V at a constant current of 0.3 C, and the discharge capacity after high temperature storage was measured. This evaluation was stored every 15 days for 60 days, and the recovery capacities after 15 days, 30 days, 45 days and 60 days after the start of the storage were measured.

The discharge capacity retention rate after high-temperature storage was determined from the following formula by the ratio of the discharge capacity after high-temperature storage after 15 days, 30 days, 45 days and 60 days after the start of storage with respect to the discharge capacity before high-temperature storage.
Discharge capacity retention rate after high temperature storage [%] = (discharge capacity after high temperature storage / discharge capacity before high temperature storage) × 100
And it evaluated by calculating the average value of the discharge capacity maintenance factor after each high temperature preservation | save after 15 days, 30 days, 45 days, and 60 days after the beginning of existence.
○: Discharge capacity maintenance rate 80% or more ×: Discharge capacity maintenance rate 80% or less

  The results of the evaluation are shown in Table 1 below.

  As can be seen by comparing each example and Comparative Examples 1 to 3, the peel strength between the negative electrode active material layer and the negative electrode current collector is improved by using a binder containing both PAN and PVdF. At the same time, even when the charge / discharge cycle progresses or when the battery is stored in a high temperature environment, the deterioration of the battery characteristics is suppressed.

  Moreover, it was found from the comparison between each example and Comparative Example 4 that when the total amount of the binder was too large, the discharge capacity was reduced in the battery having advanced charge / discharge cycles. In particular, from comparison between Example 4 and Comparative Example 4, it was found that the upper limit of the total amount of the binder was preferably 5% by weight or less.

  As can be seen by comparing each example and Comparative Examples 5 to 6, when the content of PAN as the binder is too high, or when the content of PVdF is too high, the battery characteristics are deteriorated. occured. In particular, when the content of PAN is too large, the battery characteristics deteriorated in the secondary battery having advanced cycles. Moreover, when there is too much content of PVdF, the peeling strength of a negative electrode active material layer and a negative electrode electrical power collector falls, and it is a battery characteristic in both the secondary battery which the cycle advanced, and the secondary battery after a storage test. Decrease was observed. Comparison of Example 3 and Example 6 with Comparative Example 5 and Comparative Example 6 revealed that PAN and PVdF were preferably 90:10 to 10:90 in weight ratio.

  As can be seen by comparing each Example and Comparative Example 7, when the viscosity of the binder measured by the above method is too low, a negative electrode mixture slurry that can be stably applied to the negative electrode current collector is obtained. Therefore, it is difficult to produce a negative electrode. In particular, from comparison between Example 9 or Example 10 and Comparative Example 7, it was found that each of the viscosity of PAN and the viscosity of PVdF is preferably 1000 mPa · s or more.

  Furthermore, as can be seen by comparing each Example and Comparative Example 8, when the electrolytic solution swelling resistance of the binder measured by the above method is too high, the negative electrode active material layer, the negative electrode current collector, As a result, the peel strength of the battery deteriorated, and the battery characteristics of both the secondary battery with advanced cycle and the secondary battery after high-temperature storage deteriorated. When the swelling property of PAN is high, it is considered that the battery characteristics are deteriorated due to a large cause that the binding property is deteriorated. In particular, from the comparison between Example 9 and Comparative Example 8, even if the viscosity of PAN and the viscosity of PVdF are substantially the same, a large difference occurs in battery characteristics due to the high PAN swelling, It was found that the swellability of the PAN measured by the above method is preferably 200% by weight or less.

4). Other Embodiments The present invention is not limited to the above-described embodiments of the present invention, and various modifications and applications are possible without departing from the spirit of the present invention.

  For example, in the above-described embodiments and examples, a battery having a laminate film type, a cylindrical battery structure, and a battery having a square battery structure have been described, but the present invention is not limited thereto. For example, the present invention can be similarly applied to a battery having another battery structure such as a coin type or button type shown in FIG. 5 or a battery having a laminated structure in which electrodes are laminated, and the same effect can be obtained. be able to. Also, regarding the structure of the electrode body, various configurations such as a laminated type and a zigzag folded type can be applied as well as a wound type.

  Moreover, materials, such as a positive electrode, a negative electrode, a separator, are examples, and are not limited to these.

DESCRIPTION OF SYMBOLS 1 ... Battery can 2, 3 ... Insulation board 4 ... Battery cover 5 ... Safety valve mechanism 5A ... Disc board 6 ... Heat sensitive resistance element 7, 47 ... Gasket 11, 33 , 42 ... Positive electrode 11A, 33A ... Positive electrode current collector 11B, 33B ... Positive electrode active material layer 12, 34, 43 ... Negative electrode 12A, 34A ... Negative electrode current collector 12B, 34B ... Negative electrode active material layer 13, 35, 44 ... Separator 14 ... Center pin 15, 31 ... Positive electrode lead 16, 32 ... Negative electrode lead 20, 30, 40 ... Winding electrode body 21 ..Exterior member 22 ... Adhesion film 36 ... Electrolyte 37 ... Protective tape

Claims (6)

A negative electrode active material layer is formed on the negative electrode current collector,
The negative electrode active material layer contains a negative electrode active material and a binder,
The binder has a polyacrylonitrile-based resin having an electrolytic solution swelling resistance of 200% by weight or less and a B-type viscosity of 1000 mPa · s or more, an electrolytic solution swelling resistance of 200% by weight or more, and a B-type. A negative electrode for a non-aqueous electrolyte battery containing polyvinylidene fluoride having a viscosity of 1000 mPa · s or more. The non-aqueous electrolyte battery according to claim 1, wherein the polyacrylonitrile-based resin comprises a homopolymer of (meth) acrylonitrile, a copolymer of (meth) acrylonitrile and another monomer, or a modified product of this copolymer. Negative electrode. The negative electrode for nonaqueous electrolyte electricity according to claim 2, wherein the polyacrylonitrile-based resin has the following formula (1).
(Formula 1)
_{(CH 2 -CHCN) x - (} CH 2 -CHR) y - (CH 2 -CHNH 2) z
(Wherein, R _{COO (CH 2) m -O (} CH 2) n CH 3, (CH 2) m -O (CH 2) n CH 3, COO- (CH 2 CH 2 -O) m CH 3 , And CH ₂ COOH and COOH, and m and n are 0 or more and 10 or less, and x, y, and z are the proportion of each monomer unit in the formula (unit: mass%). X> 90, y> 2 and z <1, preferably x> 92, y> 2 and z <1, more preferably x> 95, y> 2, z <0.5. .) 4. The negative electrode for a non-aqueous electrolyte battery according to claim 2, wherein a mixing ratio of the polyacrylonitrile-based resin and the polyvinylidene fluoride is 90:10 to 10:90 by weight. The total amount of the binder mixed with the polyacrylonitrile-based resin and the polyvinylidene fluoride is 1 with respect to the negative electrode mixture in which the negative electrode active material, the binder, and a conductive agent added as necessary are mixed. The negative electrode for a non-aqueous electrolyte battery according to claim 4, wherein the negative electrode is in a range of 5% by weight to 5% by weight. A positive electrode, a negative electrode, and a non-aqueous electrolyte;
The negative electrode has a negative electrode active material layer formed on a negative electrode current collector,
The negative electrode active material layer contains a negative electrode active material and a binder,
The binder has a polyacrylonitrile-based resin having an electrolytic solution swelling resistance of 200% by weight or less and a B-type viscosity of 1000 mPa · s or more, an electrolytic solution swelling resistance of 200% by weight or more, and a B-type. A non-aqueous electrolyte battery containing polyvinylidene fluoride having a viscosity of 1000 mPa · s or more.

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