JP2009135070A - Secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress stripping or spalling of a negative electrode active material layer from a negative electrode current collector in a high temperature environment without increasing a binder. <P>SOLUTION: The negative electrode of a secondary battery uses an electrolyte which includes a cyclic carbonic acid ester 80% or more and 100% or less of all solvent and in which the concentration of electrolyte salt is 0.8 mol/kg or more and 1.8 mol/kg or less. The negative electrode active material layer includes as a component a polymer containing a repeating unit originated from vinylidene fluoride, and (1) the peel strength of the negative electrode active material and the negative electrode current collector is made 4 mN/mm or more after the negative electrode active material layer is soaked in a solvent, or (2) the calorific value by a differential scanning calorimetry of the negative electrode active material layer at the time of charging is made 450 J/g or less in a range of 230°C or more and 370°C or less, or (3) the difference between the maximum value of the calorific value by the differential scanning calorimetry of the negative electrode active material under the charging and the calorific value at 100°C is made 1.60 W/g or less. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a secondary battery covered with a laminate film, and can maintain a high battery capacity and a high cycle characteristic even in a usage state and / or a manufacturing method that is exposed to a high temperature environment. The present invention relates to a secondary battery.

  In recent years, many portable electronic devices such as a camera-integrated VTR (Videotape recorder), a mobile phone, or a laptop computer have appeared, and their size and weight have been reduced. Along with this, the demand for batteries used as power sources for portable electronic devices is growing rapidly. In order to reduce the size and weight of devices, the battery design is lighter and thinner, and the storage space inside the devices is more efficient. It is required to use. As a battery satisfying such requirements, a lithium ion secondary battery having a large energy density and output density is most suitable.

  Among them, lithium ion secondary batteries using a laminate film as an exterior material are widely used. Such a lithium ion secondary battery, for example, as shown in Patent Document 1 and Patent Document 2 below, is formed by laminating a belt-like positive electrode and a negative electrode connected with electrode terminals via a separator, and then winding in a longitudinal direction. A battery element is produced. And a secondary battery is produced by enclosing and sealing this battery element with a laminate film. The secondary battery is connected to a circuit board provided with a protection circuit, and is stored in, for example, a resin molded case or a hard laminate film, thereby forming a battery pack. When a laminate film is used as an exterior material, a thin, large-area battery that is lightweight and difficult to achieve with a metal can exterior can be produced.

Japanese Patent Laid-Open No. 2002-8606 JP 2005-166650 A

  Also, a polymer battery using a gel electrolyte in which an electrolytic solution is gelled with a polymer (matrix polymer) and immobilized on the surfaces of the positive electrode and the negative electrode has been put into practical use. As the matrix polymer, polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyethylene oxide (PEO), or the like is used. Since the polymer battery has no leakage of the electrolyte, very high reliability can be obtained.

  On the other hand, in a battery using a laminate film as an exterior material, when gas is generated inside the battery, the battery outer shape is easily deformed. For this reason, the non-aqueous solvent of the electrolyte contains a high proportion of cyclic carbonate having a high boiling point, thereby suppressing gas generation inside the battery. Cyclic carbonates have a higher dielectric constant and higher electrical conductivity than chain carbonates. For this reason, the mixing amount of the electrolyte salt can be relatively reduced.

  However, in the secondary battery as described above, when the positive electrode active material layer and the negative electrode active material layer are thickened in order to increase the battery capacity and the volumetric efficiency, the battery reaction hardly occurs in a part of the active material layer. The problem of creating an area occurs. This problem can be solved by increasing the concentration of the electrolyte salt in the electrolyte. However, the increase in the electrolyte salt concentration reduces the adhesion between the current collector and the active material layer in a high temperature environment. In some cases, there arises a new problem that the active material layer is peeled off or peeled off. The peeling and peeling of the active material layer leads to a decrease in battery capacity and cycle characteristics. The active material layer is peeled off or peeled off because the binder in the active material layer swells in a high temperature environment. When a cyclic carbonate having a high dielectric constant is used as a nonaqueous solvent, the binder is used. This will further promote the swelling of the material.

  Furthermore, polymer batteries may have a heating step to form a gel electrolyte. This is to dissolve the polymer once, to crosslink the gel electrolyte, or to apply a gel electrolyte precursor melted at a high temperature to the electrode surface. In this case, since the active material layer and the electrolyte are heated in a coexisting state, the binder in the active material layer is swollen by the non-aqueous solvent, and the active material layer is peeled off from the current collector. The production itself may be difficult.

  Such a problem can be solved by increasing the content of the binder in the active material layer, but a binder that does not contribute to the battery reaction causes a decrease in battery capacity in the negative electrode active material layer. Absent.

  In addition, a decrease in adhesion between the active material layer and the current collector is problematic from the viewpoint of battery reliability. For example, when the negative electrode active material layer peels off from the negative electrode current collector and the negative electrode current collector is exposed, the negative electrode current collector may be short-circuited with the opposing positive electrode current collector to generate heat. If the battery generates a large amount of heat and the battery abnormally generates heat, using a binder containing vinylidene fluoride such as polyvinylidene fluoride as a component in the negative electrode will result in fluorine contained in the binder and lithium absorbed in the negative electrode. Due to the exothermic reaction, the battery temperature further rises and the binder may be decomposed.

  Therefore, the present invention solves the above-mentioned problems, and maintains a high battery capacity and high cycle characteristics and a high safety secondary battery even in a use state and a production method that are exposed to a high temperature environment. The purpose is to provide.

  In order to solve the above-described problems, a first invention provides a positive electrode, a negative electrode in which a negative electrode active material layer is provided on at least one surface of a negative electrode current collector, an electrolyte, and a laminate containing the positive electrode, the negative electrode, and the electrolyte. In a secondary battery having a film exterior material, the non-aqueous solvent contained in the electrolyte contains a cyclic carbonate of 80% to 100% of the total solvent, and the concentration of the electrolyte salt contained in the electrolyte is 0.8 mol / kg. It is 1.8 mol / kg or less, the negative electrode active material layer contains a polymer containing vinylidene fluoride as a component, and the peel strength between the negative electrode active material layer and the negative electrode current collector is determined using the negative electrode active material layer as a solvent. It is a secondary battery characterized by being 4 mN / mm or more after being soaked.

  In the secondary battery described above, the nonaqueous solvent for the electrolyte is ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), or diethyl carbonate (DEC). It is preferable that at least one of at least one of EC) and propylene carbonate (PC) is mixed.

  Moreover, it is preferable that a non-aqueous solvent contains 30% or more and 80% or less of propylene carbonate (PC).

  Further, the electrolyte is preferably a gel electrolyte containing 70% by mass or more and 100% by mass or less of a vinylidene fluoride component as a matrix polymer.

  Further, the solvent is preferably N-methyl-2-pyrrolidone (NMP).

  Moreover, 2nd invention has a positive electrode, the negative electrode by which the negative electrode active material layer was provided in the at least one surface of the negative electrode collector, electrolyte, and the laminate film exterior material which accommodates a positive electrode, a negative electrode, and an electrolyte. In the secondary battery, the nonaqueous solvent contained in the electrolyte contains a cyclic carbonate of 80% to 100% of the total nonaqueous solvent, and the concentration of the electrolyte salt contained in the electrolyte is 0.8 mol / kg to 1.8 mol. / Kg or less, the negative electrode active material layer contains a polymer containing a repeating unit derived from vinylidene fluoride as a component, and the calorific value by differential scanning calorimetry of the negative electrode active material layer during charging is 230 ° C. or more and 370 It is a secondary battery characterized by being 450 J / g or less within the range of ° C. or lower.

  In addition, it is more preferable that the above-mentioned calorific value is 400 J / g or less.

  Moreover, 3rd invention has a positive electrode, the negative electrode by which the negative electrode active material layer was provided in the at least one surface of the negative electrode collector, electrolyte, and the laminate film exterior material which accommodates a positive electrode, a negative electrode, and an electrolyte. In the secondary battery, the nonaqueous solvent contained in the electrolyte contains a cyclic carbonate of 80% to 100% of the total nonaqueous solvent, and the concentration of the electrolyte salt contained in the electrolyte is 0.8 mol / kg to 1.8 mol. / Kg or less, the negative electrode active material layer contains a polymer containing a repeating unit derived from vinylidene fluoride as a component, and the maximum value of the calorific value by differential scanning calorimetry of the negative electrode active material layer during charging is 100, The secondary battery is characterized in that the difference from the calorific value at 0 ° C. is 1.60 W / g or less.

  In addition, it is more preferable that the difference between the maximum value of the heat generation amount described above and the heat generation amount at 100 ° C. is 1.40 W / g or less.

  In this invention, since the negative electrode active material layer contains a polymer containing vinylidene fluoride as a component, the swelling of the binder in the negative electrode active material layer under a high temperature environment is suppressed, and the negative electrode active material layer and Adhesion with the negative electrode current collector can be improved.

  According to the present invention, even when used in a high temperature environment or when a battery is produced, peeling and / or peeling of the negative electrode active material layer is suppressed, and high battery characteristics such as high battery capacity and high cycle characteristics are maintained. It becomes possible to do.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Hereinafter, a battery using a gel electrolyte will be described, but the electrolyte is not limited thereto.

(1) First Embodiment (1-1) Configuration of Secondary Battery The negative electrode used in the secondary battery according to one embodiment of the present invention is derived from vinylidene fluoride (VdF) in the negative electrode active material layer by, for example, heat treatment. A polymer containing a repeating unit as a component is contained, and the peel strength between the negative electrode active material layer and the negative electrode current collector is 4 mN / mm or more after the negative electrode active material layer is immersed in a solvent. It is. In addition, in this invention, a polymer shall have a three-dimensional network structure, ie, shall contain a crosslinked body, and the case where a part or all of a polymer is a crosslinked body is included.

  FIG. 1A is a schematic diagram illustrating an example of the appearance of a secondary battery 1 according to an embodiment of the present invention, and FIG. 1B is a schematic diagram illustrating a configuration example of the secondary battery 1. The secondary battery 1 is obtained by packaging a battery element 10 having the configuration shown in FIG. 2 with a laminate film 4 that is an exterior material. As shown in FIG. 3, the battery element 10 includes a strip-shaped positive electrode 11 and a strip-shaped negative electrode 12 disposed so as to face the positive electrode 11 alternately stacked with separators 13 and wound in the longitudinal direction. . A gel electrolyte layer (not shown) is formed on both surfaces of the positive electrode 11 and the negative electrode 12. From the battery element 10, a positive electrode terminal 2 a connected to the positive electrode 11 and a negative electrode terminal 2 b connected to the negative electrode 12 (hereinafter referred to as electrode terminal 2 when not showing a specific electrode terminal) are derived. Yes.

  The battery element 10 is packaged with a laminate film 4 that is a packaging material. The laminate film 4 is formed with a recess 5 by, for example, drawing in advance. The battery element 10 is housed in the recess 5, the laminate film 4 is disposed so as to cover the opening of the recess 5, and the periphery of the opening of the recess 5 is sealed by heat sealing or the like. At this time, the positive electrode terminal 2 a and the negative electrode terminal 2 b are led out from the sealing portion of the laminate film 4. The portions of the positive electrode terminal 2a and the negative electrode terminal 2b that are in contact with the laminate film 4 are covered with adhesion films 3a and 3b, respectively, in order to improve the adhesion between the positive electrode terminal 2a and the negative electrode terminal 2b and the laminate film 4. .

[Negative electrode]
FIG. 3 shows the configuration of the negative electrode 12 according to an embodiment of the present invention. The negative electrode 12 is formed, for example, by forming a negative electrode active material layer 12a containing a negative electrode active material on both surfaces of a negative electrode current collector 12b having a pair of opposed surfaces. Although not shown, a region for forming the negative electrode active material layer may be provided only on one surface of the negative electrode current collector.

  The negative electrode current collector 12b needs to have good electrochemical stability, electrical conductivity, and mechanical strength. Since the negative electrode 12 is exposed to a highly reducing atmosphere, many metals including aluminum (Al) form an alloy with lithium (Li) and become powdery. For this reason, it is necessary to use a metal material that does not cause alloying. Examples of such a metal material include copper (Cu), nickel (Ni), and stainless steel (SUS). In particular, copper (Cu) is preferable because it has high electrical conductivity and high flexibility.

  The negative electrode active material layer 12a includes, for example, a negative electrode active material, a conductive agent, and a binder. As the negative electrode active material, lithium metal, a lithium alloy, a carbon material that can be doped / undoped with lithium, or a composite material of a metal material and a carbon material is used. Specific examples of carbon materials that can be doped / undoped with lithium include graphite, non-graphitizable carbon, graphitizable carbon, and the like. More specifically, pyrolytic carbons and cokes (pitch coke, needle coke). , Petroleum coke), graphites, glassy carbons, organic polymer compound fired bodies (phenol resins, furan resins, etc., calcined at an appropriate temperature), carbon fibers, activated carbon and other carbon materials are used. be able to.

  In particular, natural graphite and artificial graphite and other graphites are rich in chemical stability and can repeatedly and stably undergo lithium ion deinsertion reactions, and are easily available industrially. Widely used.

  As materials other than carbon, various kinds of metals and semi-metals can be used. For example, magnesium (Mg), boron (B), aluminum (Al), gallium capable of forming an alloy with lithium can be used. (Ga), indium (In), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), bismuth (Bi), cadmium (Cd), silver (Ag), zinc (Zn), hafnium (Hf), zirconium (Zr), yttrium (Y), palladium (Pd), platinum (Pt), and alloys thereof. These may be crystalline or amorphous.

Further, lithium doped as the dedoping can material, may be used polyacetylene, an oxide of _2, such as polymers and SnO polypyrrole.

  Moreover, the negative electrode active material layer 12a contains a binder. As the binder, a polymer containing a repeating unit derived from vinylidene fluoride (VdF) as a component is preferable. This is because the stability in the secondary battery is high. Examples of such a polymer include a copolymer containing polyvinylidene fluoride (PVdF) or vinylidene fluoride (VdF) as a component. Specific examples of the copolymer include vinylidene fluoride-hexafluoropropylene (HFP) copolymer, vinylidene fluoride-tetrafluoroethylene (TFE) copolymer, vinylidene fluoride-chlorotrifluoroethylene (TFE) copolymer Examples thereof include vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-carboxylic acid copolymer, and vinylidene fluoride-hexafluoropropylene-carboxylic acid copolymer. Examples of the vinylidene fluoride-hexafluoropropylene-carboxylic acid copolymer include a vinylidene fluoride-hexafluoropropylene-monomethylmaleic acid ester copolymer. As the binder, one kind may be used alone, or two or more kinds may be mixed and used.

  The polymer as described above is, for example, crosslinked in the negative electrode active material, whereby the swelling of the polymer is suppressed, and the adhesion between the negative electrode active material layer 12a and the negative electrode current collector 12b can be improved. It is like that.

  Further, the peel strength between the negative electrode active material layer 12a and the negative electrode current collector 12b after the negative electrode 12 is immersed in a solvent is preferably 4 mN / mm or more, and more preferably 5 mN / mm or more. This is because, even after being soaked in a solvent, sufficient properties can be obtained with such a level of peel strength.

  In addition, the peeling strength after being immersed in a solvent can be measured using the following method, for example. That is, the anode 12 is immersed in a solvent, heated at 80 ° C. for 1 hour, and then dried. Thereafter, as shown in FIG. 4, for example, a peel strength of the negative electrode active material layer 12a is measured by a tensile test in which a tape (not shown) is applied to the negative electrode active material layer 12a and the tape is pulled in the arrow direction (180 ° direction). . For example, a tape having a width of 25 mm can be used. The tensile test can be measured, for example, by pulling the tape 60 mm in the 180 ° direction at a speed of 100 mm / min. The peel strength value is an average value between 10 mm and 60 mm, and is a value normalized by the tape width.

  At this time, N-methyl-2-pyrrolidone (NMP) is the most effective solvent, but esters such as propylene carbonate (PC), ethyl acetate, butyl acetate, dimethylformamide (DMF), tetrahydrofuran (THF) Or amines such as dimethylamine and triethylamine, or ketones such as acetone.

[Positive electrode]
The positive electrode 11 is formed by forming a positive electrode active material layer 11a containing a positive electrode active material on both surfaces of a positive electrode current collector 11b having a pair of opposing surfaces. As the positive electrode current collector 11b, for example, a metal foil such as an aluminum (Al) foil is used.

The positive electrode active material layer 11a includes, for example, a positive electrode active material, a conductive agent, and a binder. As the positive electrode active material, mainly Li _x MO ₂ (wherein M represents one or more transition metals, x is different depending on the charge / discharge state of the battery, and is usually 0.05 or more and 1.10 or less). A composite oxide of lithium and a transition metal is used. 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 lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), and lithium manganate (LiMn ₂ O ₄ ). A solid solution in which a part of the transition metal element is substituted with another element can also be used. Examples thereof include nickel cobalt composite lithium oxide (LiNi _0.5 Co _0.5 O ₂ , LiNi _0.8 Co _0.2 O _2, etc.). These lithium composite oxides can generate a high voltage and have an excellent energy density. Furthermore, TiS _2, MoS _2, may be used NbSe _2, V ₂ O no lithium metal sulfides such as ₅ or metal oxide as a cathode active material. As the positive electrode active material, a mixture of a plurality of these materials may be used.

  As the conductive agent, for example, a carbon material such as carbon black or graphite is used. As the binder, for example, polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), or the like is used.

[Laminate film]
As shown in FIG. 5, the laminate film 4 used as the exterior material is formed of a multilayer film having moisture resistance and insulating properties, in which an outer resin layer 4b and an inner resin layer 4c are formed on both surfaces of the metal foil 4a, respectively. . Nylon (Ny) or polyethylene terephthalate (PET) is used for the outer resin layer 4b because of its beautiful appearance, toughness, and flexibility. The metal foil 4a plays the most important role in preventing moisture, oxygen and light from entering, and protecting the battery element, which is the content. Aluminum (Al) is light because of its lightness, extensibility, price, and ease of processing. Is most often used. The inner resin layer 4c is a portion that is melted by heat or ultrasonic waves and fused to each other, and a polyolefin-based resin material such as unstretched polypropylene (CPP) is frequently used.

[Separator]
The separator 13 is composed of, for example, a porous film made of a polyolefin resin material such as polypropylene (PP) or polyethylene (PE), or a porous film made of an inorganic material such as a ceramic nonwoven fabric. A structure in which the porous films are laminated may be used. Among these, porous films of polyethylene (PE) and polypropylene (PP) are most effective.

  In general, the thickness of the separator is preferably 5 μm or more and 50 μm or less, more preferably 5 μm or more and 20 μm or less. If the separator is too thick, the amount of the active material filled decreases, the battery capacity decreases, and the ionic conductivity decreases and the current characteristics deteriorate. On the other hand, if it is too thin, the mechanical strength of the film will decrease, and both positive and negative electrodes will be shorted or broken by foreign matter.

[Electrolytes]
As the electrolyte, an electrolyte salt and a non-aqueous solvent that are generally used in lithium ion secondary batteries can be used. As the non-aqueous solvent, propylene carbonate (PC) and ethylene carbonate (EC) and / or cyclic carbonate are contained in an amount of 80% to 100% of the total non-aqueous solvent. In addition to the cyclic carbonate, the non-aqueous solvent may be one or more of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), which are chain carbonates. Good. When the cyclic carbonate is less than 80%, the proportion of the chain carbonate having a low boiling point of the electrolyte increases, so that gas is easily generated due to decomposition of the electrolyte inside the battery, and the battery is likely to swell. In addition, the dielectric constant of the electrolyte is lowered, and the electrical conductivity is reduced.

  Moreover, it is preferable that propylene carbonate (PC) is contained 30% or more and 80% or less of the total non-aqueous solvent among the cyclic carbonates. Propylene carbonate (PC) reacts with graphite of the negative electrode and decomposes to become a gas, so that it is difficult to use propylene carbonate (PC) alone, and it is often used by mixing with other solvents. As a solvent having low reactivity with graphite, ethylene carbonate (EC) is well known and widely used. Ethylene carbonate (EC) is suitable because it is one of cyclic carbonates and has a high boiling point.

  The content of propylene carbonate (PC) is determined by a relative relationship with ethylene carbonate (EC). When the content of propylene carbonate (PC) is less than 30%, the content of ethylene carbonate (EC) exceeds 70%, but since ethylene carbonate (EC) has a melting point of 38 ° C., the non-aqueous solvent has a low temperature. In this case, the ionic conductivity is reduced and the low temperature characteristics of the battery are deteriorated. Also, when the content of propylene carbonate (PC) exceeds 80%, the content of ethylene carbonate (EC) becomes less than 20%, the reactivity with graphite increases, the capacity decreases, and the propylene carbonate ( PC) Battery swelling due to gas generation accompanying decomposition becomes a problem. Here, “%” represents a weight percentage.

As the electrolyte salt, one that dissolves in the non-aqueous solvent is used, and a combination of a cation and an anion is used. As the cation, an alkali metal or an alkaline earth metal is used. As the anion, Cl ⁻ , Br ⁻ , I ⁻ , SCN ⁻ , ClO ₄ ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , CF ₃ SO ₃ ^{− and the} like are used. Specifically, lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), bis (trifluoromethanesulfonyl) imide lithium (LiN (CF ₃ SO ₂ ) ₂ ), bis (pentafluoro Ethanesulfonyl) imidolithium (LiN (C ₂ F ₅ SO ₂ ) ₂ ) lithium perchlorate (LiClO ₄ ) and the like. As the electrolyte salt concentration, the lithium ion concentration is in the range of 0.8 mol / kg to 1.8 mol / kg with respect to the non-aqueous solvent.

  When a gel electrolyte is used, the gel electrolyte is obtained by incorporating an electrolytic solution obtained by mixing a nonaqueous solvent and an electrolyte salt into a matrix polymer. The matrix polymer has a property compatible with a non-aqueous solvent. As such a matrix polymer, silicon gel, acrylic gel, acrylonitrile gel, polyphosphazene modified polymer, polyethylene oxide, polypropylene oxide, and their composite polymers, cross-linked polymers, modified polymers, and the like are used. Examples of the fluoropolymer include polyvinylidene fluoride (PVdF), vinylidene fluoride (VdF) -hexafluoropropylene (HFP) copolymer, vinylidene fluoride (VdF) -tetrafluoroethylene (TFE) copolymer, and the like. And a polymer containing a repeating unit derived from vinylidene chloride. Such polymers may be used alone or in combination of two or more, and contain 70% by mass to 100% by mass of a vinylidene fluoride (VdF) component. Is preferred.

(1-2) Secondary Battery Manufacturing Method The secondary battery 1 having the above-described configuration is manufactured as follows.

[Production of positive electrode]
First, a positive electrode active material, a conductive agent, and a binder are uniformly mixed to form a positive electrode mixture, and the positive electrode mixture is dispersed in a solvent to form a slurry. Next, the slurry is uniformly applied on the positive electrode current collector 11b by a doctor blade method or the like, dried, and after removing the solvent, the positive electrode active material layer 11a is formed by compression molding with a roll press or the like. To do. Here, the positive electrode active material, the conductive agent, the binder, and the solvent only have to be uniformly dispersed, and the mixing ratio is not limited.

  Next, the positive electrode terminal 2a is connected to one end of the positive electrode current collector 11b by spot welding or ultrasonic welding. The positive electrode terminal 2a is preferably a metal foil or a mesh-like one, but there is no problem even if it is not metal as long as it is electrochemically and chemically stable and can conduct electricity.

[Production of negative electrode]
Subsequently, the negative electrode active material, the binder, and, if necessary, the conductive agent are uniformly mixed to form a negative electrode mixture, and the negative electrode mixture is dispersed in a solvent to form a slurry. Next, this slurry is uniformly applied onto the negative electrode current collector 12b by a doctor blade method or the like, dried to remove the solvent, and then compression molded by a roll press or the like. Here, the negative electrode active material, the conductive agent, the binder, and the solvent only have to be uniformly dispersed, and the mixing ratio is not limited.

  Subsequently, the negative electrode active material layer precursor compression-molded on the negative electrode current collector 12b is irradiated with an electron beam, ultraviolet light, or the like, or the negative electrode active material layer precursor is heated, whereby the negative electrode active material layer precursor is heated. The negative electrode active material layer 12a is formed by polymerizing the binder in the body. At this time, the polymerization degree of the binder is adjusted by appropriately changing various conditions such as the irradiation time and output of an electron beam or ultraviolet rays, or the heating time. Thereby, the negative electrode 12 of this invention is obtained.

  When irradiating the negative electrode active material layer precursor with an electron beam or ultraviolet rays, it is preferable to irradiate for 3 minutes or more. In addition, the longer the irradiation time of the electron beam or the ultraviolet ray, the higher the degree of polymerization, the stronger the peel strength between the negative electrode active material layer 12a and the negative electrode current collector 12b, and the better the battery characteristics. When the electron beam or ultraviolet irradiation time is less than 3 minutes, the degree of polymerization of the binder is low, and there is a possibility that sufficient peel strength cannot be obtained.

  When heating a negative electrode active material layer precursor, it is preferable to heat at a high temperature of 180 ° C. or higher. In addition, the higher the heating temperature of the negative electrode active material layer precursor, the higher the degree of polymerization, the stronger the peel strength between the negative electrode active material layer 12a and the negative electrode current collector 12b, and the better the battery characteristics. When the heating temperature of the negative electrode active material layer precursor is lower than 180 ° C., the degree of polymerization of the binder is low, and sufficient peel strength may not be obtained.

  Next, the negative electrode terminal 2b is connected to one end of the negative electrode current collector 12b by spot welding or ultrasonic welding. The negative electrode terminal 2b 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.

  In addition, although it is preferable that the positive electrode terminal 2a and the negative electrode terminal 2b are derived | led-out from the same direction, if a short circuit etc. do not occur and there is no problem in battery performance, it is satisfactory even if it derive | leads out from which direction. Moreover, the connection location of the positive electrode terminal 2a and the negative electrode terminal 2b is not limited to the above example as long as electrical contact is established, and the method of attachment is not limited to the above example.

[Formation of gel electrolyte layer]
0.8 mol / kg or more of an electrolyte salt such as lithium hexafluorophosphate (LiPF ₆ ) or lithium tetrafluoroborate (LiBF ₄ ) in a non-aqueous solvent containing a cyclic carbonate of 80% to 100% After preparing an electrolytic solution by dissolving to a concentration of 1.8 mol / kg or less, for example, a matrix polymer such as vinylidene fluoride (VdF) -hexafluoropropylene (HFP) copolymer and the electrolytic solution are mixed. Thus, a sol electrolyte is prepared.

  Subsequently, a sol-like electrolyte is applied onto the positive electrode active material layer 11a and the negative electrode active material layer 12a, respectively, and cooled to form a gel electrolyte layer. Alternatively, for example, a low-viscosity sol is prepared using dimethyl carbonate (DMC) or the like as a diluent solvent, and coated on the positive electrode active material layer 11a and the negative electrode active material layer 12a, respectively, and then the diluent solvent is volatilized to form a gel electrolyte layer You can also

  Then, the positive electrode 11, the separator 33, the negative electrode 12, and the separator 33 are laminated | stacked one by one, and this laminated body is wound many times in a longitudinal direction. Then, the winding type battery element 10 is manufactured by providing a protective tape on the outermost winding periphery.

  Next, as shown in FIG. 1B, the battery element 10 is formed in the recess 5 using the laminate film 4 in which the recess 5 is formed by drawing in advance from the inner resin layer 4c toward the outer resin layer 4b. The exterior is made to be stored. At this time, the exterior resin layer 4c of the laminate film 4 is packaged so as to face each other. Then, the secondary battery 1 is produced by heat-sealing the peripheral part of the opening of the recessed part 5 formed in the laminate film 4 under reduced pressure.

  The secondary battery 1 may be manufactured by the following method. First, in the same manner as described above, the positive electrode 11 connected to the positive electrode terminal 2a and the negative electrode 12 connected to the negative electrode terminal 2b are prepared, stacked and wound via the separator 23, and protected to the outermost winding periphery. A battery element 10 is manufactured by providing a tape. At this time, the gel electrolyte layer is not provided. Next, the battery element 10 is packaged with the laminate film 4, and the outer peripheral edge except one side is heat-sealed to make the laminate film 4 into a bag shape. Next, an electrolyte composition containing a nonaqueous solvent, an electrolyte salt, a monomer that is a raw material for the polymer compound, a polymerization initiator, and other materials such as a polymerization inhibitor as necessary is prepared. Then, it is poured into the bag-shaped laminate film 4.

  After injecting the electrolyte composition, the opening of the laminate film 4 is heat-sealed in a vacuum atmosphere and sealed. Next, the laminate film 4 containing the battery element 10 and the electrolyte composition is heated to polymerize the monomer to form a polymer compound, thereby forming a gel electrolyte and manufacturing the secondary battery 1.

  Since the secondary battery 1 of the first embodiment contains a polymer containing as a component a repeating unit derived from vinylidene fluoride in the negative electrode active material layer 12a, the secondary battery 1 is used in a high-temperature environment. In the case where the negative electrode active material layer 12a is peeled off and / or peeled off from the negative electrode current collector 12b, the negative electrode current collector 12b can be prevented from peeling off and / or peeling off.

  In addition, since the negative electrode active material layer 12a can be prevented from peeling and / or peeling from the negative electrode current collector 12b without increasing the binder content, the high battery without reducing the battery capacity. A secondary battery having characteristics can be obtained.

(2) Second Embodiment (2-1) Configuration of Secondary Battery In the second embodiment, the configuration other than the negative electrode is the same as that of the first embodiment, and thus the description thereof is omitted. Moreover, since the structure of the negative electrode in 2nd Embodiment is the same as the negative electrode in 1st Embodiment, it demonstrates using the same code | symbol in the following description.

[Negative electrode]
The negative electrode 12 used in the secondary battery of the second embodiment is similar to the first embodiment in that a negative electrode active material layer containing a negative electrode active material on both surfaces of a negative electrode current collector 12b having a pair of opposed surfaces. 12a is formed. The negative electrode active material layer 12a includes, for example, a negative electrode active material, a conductive agent, and a binder. As the negative electrode active material, lithium metal, a lithium alloy, a carbon material that can be doped / undoped with lithium, or a composite material of a metal material and a carbon material is used. As the negative electrode active material, the conductive agent, and the binder, the same materials as in the first embodiment can be used.

  In the negative electrode 12 in the second embodiment, the negative electrode active material layer 12a is heat-treated, so that the fluorine in the negative electrode active material layer that raises the battery temperature by exothermic reaction with lithium occluded in the negative electrode active material. The amount is reduced. The heat treatment is performed at a temperature equal to or higher than the melting point of the binder contained in the negative electrode active material layer 12a. As a result, an increase in battery temperature due to an exothermic reaction between lithium or the like occluded in the negative electrode active material and fluorine in the binder is suppressed.

  Specifically, there is a reaction peak between lithium and fluorine when differential scanning calorimetry (DSC) is performed on the negative electrode active material layer 12a that occludes lithium or the like, that is, the charged negative electrode active material layer 12a. Within the range of 230 ° C. or more and 370 ° C. or less, the total calorific value is preferably 450 J / g or less, and more preferably 400 J / g or less. Alternatively, when the negative electrode active material layer 12a in a charged state is subjected to differential scanning calorimetry, the maximum calorific value and the exotherm at 100 ° C. are within a range of 230 ° C. or higher and 370 ° C. or lower where there is a reaction peak between lithium and fluorine. The difference from the amount is preferably 1.60 W / g or less, and more preferably 1.40 W / g or less. This is because within this range, the adhesion of the negative electrode active material layer 12a to the negative electrode current collector 12b is enhanced, and the effect of suppressing the exothermic reaction is high.

(2-2) Method for Manufacturing Secondary Battery The secondary battery 1 having the above-described configuration is manufactured as follows. Hereinafter, only the manufacturing method of the negative electrode 12 will be described.

[Production of negative electrode]
The negative electrode active material, the binder, and, if necessary, the conductive agent are uniformly mixed to form a negative electrode mixture, and the negative electrode mixture is dispersed in a solvent to form a slurry. Next, this slurry is uniformly applied onto the negative electrode current collector 12b, dried to remove the solvent, and then compression molded with a roll press or the like.

  Subsequently, the negative electrode active material layer precursor compression-molded on the negative electrode current collector 12b is heated to reduce the amount of fluorine in the negative electrode active material layer precursor, thereby forming the negative electrode active material layer 12a.

  The negative electrode active material layer precursor is heated at a temperature equal to or higher than the melting point of the binder. When polyvinylidene fluoride is used as the binder, the melting point is about 130 ° C to 170 ° C. The higher the heating temperature of the negative electrode active material layer precursor is, the higher the decrease in the amount of fluorine, and the less the exothermic reaction between lithium occluded in the negative electrode active material and fluorine in the negative electrode active material layer 12a. When the heating temperature of the negative electrode active material layer precursor is lower than 150 ° C., the amount of decrease in fluorine in the binder is small, and the exothermic reaction between lithium occluded in the negative electrode active material and fluorine in the negative electrode active material layer 12a is suppressed. There is a possibility that it cannot be done.

  Next, the negative electrode terminal 2b is connected to one end of the negative electrode current collector 12b by spot welding or ultrasonic welding. The negative electrode terminal 2b 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.

  In the secondary battery 1 of the second embodiment, the calorific value of the negative electrode active material layer in a charged state is 450 J / g or less or the charge is within a range from 230 ° C. to 370 ° C. where there is a reaction peak between lithium and fluorine. Since the difference between the maximum value of the calorific value of the negative electrode active material layer in the state and the calorific value at 100 ° C. is 1.60 W / g or less, the amount of fluorine contained in the negative electrode active material layer 12a is reduced. In addition, an exothermic reaction with lithium occluded in the negative electrode active material is suppressed. Accordingly, it is possible to suppress the decomposition of the binder even when the battery is abnormally heated. For this reason, since it can suppress that the negative electrode active material layer 12a peels and / or peels from the negative electrode collector 12b, without increasing a binder content, it is high, without reducing battery capacity. A secondary battery having battery characteristics and high safety can be obtained.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to these examples.

<Example 1>
(1) Negative electrode treatment method: electron beam irradiation <Sample 1>
[Production of positive electrode]
Lithium carbonate (Li ₂ CO ₃ ) and cobalt carbonate (CoCO ₃ ) were mixed at a molar ratio of 0.5: 1, and calcined in air at 900 ° C. for 5 hours to obtain lithium cobaltate (LiCoO ₂ ). . Subsequently, lithium cobalt oxide (LiCoO ₂ ) that is the positive electrode active material, graphite that is the conductive agent, and polyvinylidene fluoride (PVdF) that is the binder are uniformly distributed so as to have a mass ratio of 91: 6: 3. The mixture was mixed and dispersed in N-methyl-2-pyrrolidone to prepare a slurry-like positive electrode mixture. This slurry-like positive electrode mixture is uniformly applied to both sides of a positive electrode current collector made of 20 μm thick aluminum (Al) foil, and dried under reduced pressure for 12 hours at 120 ° C. to form a positive electrode active material layer did. Next, this was press-molded with a roll press to obtain a positive electrode sheet, and the positive electrode sheet was cut into a strip shape to obtain a positive electrode.

  Furthermore, a positive electrode terminal made of an aluminum (Al) ribbon was welded to a portion where the positive electrode active material layer was not formed on the positive electrode current collector. The aluminum (Al) ribbon was provided with an adhesive film made of acid-modified polypropylene at a portion facing the laminate film when it was later sheathed with a laminate film.

[Production of negative electrode]
Mesophase graphite microspheres having an average particle diameter of 20 μm are used as the negative electrode active material, and vinylidene fluoride and monomethylmaleic acid ester are copolymerized at a mass ratio of 99: 1 as a binder. Using the coalescence, the negative electrode active material and the binder were uniformly mixed so as to have a mass ratio of 95: 5 and dispersed in N-methyl-2-pyrrolidone to prepare a slurry-like negative electrode mixture. Next, this slurry-like negative electrode mixture is uniformly applied to both sides of a negative electrode current collector made of a copper (Cu) foil having a thickness of 15 μm at a thickness of 50 μm, and dried under reduced pressure for 10 minutes in an atmosphere of 120 ° C. Thus, a negative electrode active material layer was formed. Next, this was pressure-molded with a roll press machine to obtain a negative electrode sheet, and the negative electrode sheet was cut into a strip shape.

  Subsequently, the negative electrode active material layer was not irradiated with an electron beam, and the binder in the negative electrode active material layer was formed into a negative electrode without polymerizing (crosslinking). Further, a negative electrode terminal made of a nickel (Ni) ribbon was welded to a portion where the negative electrode active material layer was not formed on the negative electrode current collector. The nickel (Ni) ribbon was provided with an adhesive film made of acid-modified polypropylene at a portion facing the laminate film when it was later sheathed with a laminate film.

[Formation of gel electrolyte layer]
As a non-aqueous solvent, a mixed solvent in which ethylene carbonate (EC) and propylene carbonate (PC) are mixed at a mass ratio of 4: 6 is used, and lithium hexafluorophosphate (LiPF ₆ ) that is an electrolyte salt is used as the mixed solvent. Was dissolved so that the molar concentration was 0.3 mol / kg to prepare a non-aqueous electrolyte. As a matrix polymer, a copolymer having a number average molecular weight of 700,000 obtained by copolymerizing vinylidene fluoride (VdF) and hexafluoropropylene (HFP) at a mass ratio of 93: 7, and dimethyl carbonate (DMC) as a diluent solvent. The matrix polymer, the non-aqueous electrolyte, and the diluting solvent were mixed at a mass ratio of 1:10:10 and dissolved at 70 ° C. to obtain a sol electrolyte.

  Next, a gel electrolyte layer having a thickness of 20 μm is formed on the surfaces of the positive electrode and the negative electrode by applying the above sol electrolyte on both surfaces of the positive electrode and the negative electrode and volatilizing the diluting solvent with hot air at 100 ° C. did. Then, the positive electrode and negative electrode in which the gel electrolyte layer was formed were laminated | stacked and wound through the separator which consists of a 20-micrometer-thick porous polyethylene film, and the battery element was produced.

  Furthermore, the produced battery element was covered with an aluminum laminate film and sealed to obtain a secondary battery. The aluminum laminate film has a structure in which a 30 μm thick nylon (Ny) film and a 30 μm thick crystalline polypropylene (PP) film are bonded to both sides of a 40 μm thick aluminum (Al) foil. The polypropylene film side was the inside (battery element side). The battery element is housed in a recess formed in advance in the aluminum laminate film, and after folding the aluminum laminate film to cover the opening of the recess, the three sides of the outer peripheral edge excluding the folded back are heat-sealed and vacuum sealed. Stopped. The positive electrode terminal and the negative electrode terminal were led out from the sealed portion of the aluminum laminate film. Moreover, the part which the positive electrode terminal and negative electrode terminal, and the aluminum laminate film oppose was sealed with airtightness with the contact | adherence film.

<Sample 2>
A secondary battery was fabricated in the same manner as Sample 1, except that the negative electrode active material layer precursor was irradiated with an electron beam for 3 minutes to polymerize (crosslink) the binder in the negative electrode active material layer.

<Sample 3>
A secondary battery was fabricated in the same manner as in Sample 1, except that the negative electrode active material layer precursor was irradiated with an electron beam for 10 minutes to polymerize (crosslink) the binder in the negative electrode active material layer.

<Sample 4>
A secondary battery was fabricated in the same manner as Sample 1 except that the negative electrode active material layer precursor was irradiated with an electron beam for 30 minutes to polymerize (crosslink) the binder in the negative electrode active material layer.

<Sample 5>
A secondary battery was fabricated in the same manner as Sample 1, except that lithium hexafluorophosphate (LiPF ₆ ), which is an electrolyte salt, was dissolved in a mixed solvent so that the molar concentration was 0.8 mol / kg.

<Sample 6>
Lithium hexafluorophosphate (LiPF ₆ ), which is an electrolyte salt, was dissolved in a mixed solvent so that the molar concentration was 0.8 mol / kg, and the negative electrode active material layer precursor was irradiated with an electron beam for 3 minutes. A secondary battery was made in the same manner as Sample 1 except for the above.

<Sample 7>
Lithium hexafluorophosphate (LiPF ₆ ) as an electrolyte salt was dissolved in a mixed solvent so that the molar concentration was 0.8 mol / kg, and the negative electrode active material layer precursor was irradiated with an electron beam for 10 minutes. A secondary battery was made in the same manner as Sample 1 except for the above.

<Sample 8>
Lithium hexafluorophosphate (LiPF ₆ ) as an electrolyte salt was dissolved in a mixed solvent so that the molar concentration was 0.8 mol / kg, and the negative electrode active material layer precursor was irradiated with an electron beam for 30 minutes. A secondary battery was made in the same manner as Sample 1 except for the above.

<Sample 9>
A secondary battery was fabricated in the same manner as Sample 1, except that lithium hexafluorophosphate (LiPF ₆ ), which is an electrolyte salt, was dissolved in a mixed solvent so that the molar concentration was 1.2 mol / kg.

<Sample 10>
Lithium hexafluorophosphate (LiPF ₆ ) as an electrolyte salt was dissolved in a mixed solvent so that the molar concentration was 1.2 mol / kg, and the negative electrode active material layer precursor was irradiated with an electron beam for 3 minutes. A secondary battery was made in the same manner as Sample 1 except for the above.

<Sample 11>
Lithium hexafluorophosphate (LiPF ₆ ), which is an electrolyte salt, was dissolved in a mixed solvent so that the molar concentration was 1.2 mol / kg, and the negative electrode active material layer precursor was irradiated with an electron beam for 10 minutes. A secondary battery was made in the same manner as Sample 1 except for the above.

<Sample 12>
Lithium hexafluorophosphate (LiPF ₆ ), which is an electrolyte salt, was dissolved in a mixed solvent so that the molar concentration was 1.2 mol / kg, and the negative electrode active material layer precursor was irradiated with an electron beam for 30 minutes. A secondary battery was made in the same manner as Sample 1 except for the above.

<Sample 13>
A secondary battery was fabricated in the same manner as Sample 1 except that lithium hexafluorophosphate (LiPF ₆ ), which is an electrolyte salt, was dissolved in a mixed solvent so that the molar concentration was 1.8 mol / kg.

<Sample 14>
Lithium hexafluorophosphate (LiPF ₆ ), which is an electrolyte salt, was dissolved in a mixed solvent so that the molar concentration was 1.8 mol / kg, and the negative electrode active material layer precursor was irradiated with an electron beam for 3 minutes. A secondary battery was made in the same manner as Sample 1 except for the above.

<Sample 15>
Lithium hexafluorophosphate (LiPF ₆ ), which is an electrolyte salt, was dissolved in a mixed solvent so that the molar concentration was 1.8 mol / kg, and the negative electrode active material layer precursor was irradiated with an electron beam for 10 minutes. A secondary battery was made in the same manner as Sample 1 except for the above.

<Sample 16>
Lithium hexafluorophosphate (LiPF ₆ ), which is an electrolyte salt, was dissolved in a mixed solvent so that the molar concentration was 1.8 mol / kg, and the negative electrode active material layer precursor was irradiated with an electron beam for 30 minutes. A secondary battery was made in the same manner as Sample 1 except for the above.

<Sample 17>
A secondary battery was fabricated in the same manner as in Sample 1, except that lithium hexafluorophosphate (LiPF ₆ ), which is an electrolyte salt, was dissolved in a mixed solvent so that the molar concentration was 1.9 mol / kg.

<Sample 18>
An electrolyte salt, lithium hexafluorophosphate (LiPF ₆ ), was dissolved in a mixed solvent so that the molar concentration was 1.9 mol / kg, and the negative electrode active material layer precursor was irradiated with an electron beam for 3 minutes. A secondary battery was made in the same manner as Sample 1 except for the above.

<Sample 19>
An electrolyte salt, lithium hexafluorophosphate (LiPF ₆ ), was dissolved in a mixed solvent so that the molar concentration was 1.9 mol / kg, and the negative electrode active material layer precursor was irradiated with an electron beam for 10 minutes. A secondary battery was made in the same manner as Sample 1 except for the above.

<Sample 20>
Lithium hexafluorophosphate (LiPF ₆ ), which is an electrolyte salt, was dissolved in a mixed solvent so that the molar concentration was 1.9 mol / kg, and the negative electrode active material layer precursor was irradiated with an electron beam for 30 minutes. A secondary battery was made in the same manner as Sample 1 except for the above.

(2) Negative electrode treatment method: heating in vacuum <Sample 21>
A secondary battery was fabricated in the same manner as in Sample 1, except that the strip-shaped negative electrode sheet obtained by pressure-molding the negative electrode active material layer with a roll press was heated in a vacuum at a heating temperature of 25 ° C. for 12 hours. Of the heating time of 12 hours, the heating time is 4 hours from the start of heating.

<Sample 22>
A secondary battery was fabricated in the same manner as Sample 21, except that the heating temperature was 180 ° C.

<Sample 23>
A secondary battery was fabricated in the same manner as Sample 21, except that the heating temperature was 200 ° C.

<Sample 24>
A secondary battery was fabricated in the same manner as Sample 21, except that the heating temperature was 220 ° C.

<Sample 25>
A secondary battery was fabricated in the same manner as Sample 21, except that lithium hexafluorophosphate (LiPF ₆ ), which is an electrolyte salt, was dissolved in a mixed solvent so that the molar concentration was 0.8 mol / kg.

<Sample 26>
An electrolyte salt, lithium hexafluorophosphate (LiPF ₆ ), was dissolved in a mixed solvent so that the molar concentration was 0.8 mol / kg, and the heating temperature was changed to 180 ° C. A secondary battery was produced.

<Sample 27>
An electrolyte salt, lithium hexafluorophosphate (LiPF ₆ ), was dissolved in a mixed solvent so that the molar concentration was 0.8 mol / kg, and the heating temperature was set to 200 ° C. A secondary battery was produced.

<Sample 28>
An electrolyte salt, lithium hexafluorophosphate (LiPF ₆ ), was dissolved in a mixed solvent so that the molar concentration was 0.8 mol / kg, and the heating temperature was 220 ° C. A secondary battery was produced.

<Sample 29>
A secondary battery was fabricated in the same manner as in Sample 21, except that lithium hexafluorophosphate (LiPF ₆ ), which is an electrolyte salt, was dissolved in a mixed solvent so that the molar concentration was 1.2 mol / kg.

<Sample 30>
The electrolyte salt lithium hexafluorophosphate (LiPF ₆ ) was dissolved in a mixed solvent so that the molar concentration was 1.2 mol / kg, and the heating temperature was changed to 180 ° C. A secondary battery was produced.

<Sample 31>
The electrolyte salt, lithium hexafluorophosphate (LiPF ₆ ), was dissolved in a mixed solvent so that the molar concentration was 1.2 mol / kg, and the heating temperature was set to 200 ° C. A secondary battery was produced.

<Sample 32>
The electrolyte salt lithium hexafluorophosphate (LiPF ₆ ) was dissolved in a mixed solvent so that the molar concentration was 1.2 mol / kg, and the heating temperature was set to 220 ° C. A secondary battery was produced.

<Sample 33>
A secondary battery was fabricated in the same manner as Sample 21 except that lithium hexafluorophosphate (LiPF ₆ ), which is an electrolyte salt, was dissolved in a mixed solvent so that the molar concentration was 1.8 mol / kg.

<Sample 34>
An electrolyte salt, lithium hexafluorophosphate (LiPF ₆ ), was dissolved in a mixed solvent such that the molar concentration was 1.8 mol / kg, and the heating temperature was changed to 180 ° C. A secondary battery was produced.

<Sample 35>
An electrolyte salt, lithium hexafluorophosphate (LiPF ₆ ), was dissolved in a mixed solvent such that the molar concentration was 1.8 mol / kg, and the heating temperature was 200 ° C. A secondary battery was produced.

<Sample 36>
The electrolyte salt, lithium hexafluorophosphate (LiPF ₆ ), was dissolved in a mixed solvent so that the molar concentration was 1.8 mol / kg, and the heating temperature was 220 ° C. A secondary battery was produced.

<Sample 37>
A secondary battery was fabricated in the same manner as Sample 21, except that lithium hexafluorophosphate (LiPF ₆ ), which is an electrolyte salt, was dissolved in a mixed solvent so that the molar concentration was 1.9 mol / kg.

<Sample 38>
An electrolyte salt, lithium hexafluorophosphate (LiPF ₆ ), was dissolved in a mixed solvent so that the molar concentration was 1.9 mol / kg, and the heating temperature was 180 ° C. A secondary battery was produced.

<Sample 39>
The electrolyte salt lithium hexafluorophosphate (LiPF ₆ ) was dissolved in a mixed solvent so that the molar concentration was 1.9 mol / kg, and the heating temperature was set to 200 ° C. A secondary battery was produced.

<Sample 40>
An electrolyte salt, lithium hexafluorophosphate (LiPF ₆ ), was dissolved in a mixed solvent so that the molar concentration was 1.9 mol / kg, and the heating temperature was 220 ° C. A secondary battery was produced.

[Characteristic evaluation]
(A) High-temperature cycle test For each of the secondary batteries of Sample 1 to Sample 40, in a 60 ° C environment, a constant current charge was performed until the battery voltage reached 4.2 V at a constant current of 1 C, and then 4.2 V Constant voltage charging was performed until the total charging time was 2.5 hours. Next, constant current discharge was performed at a constant current of 1 C until the battery voltage reached 3.0 V, and the discharge capacity at the first cycle was measured.

  Subsequently, after 400 cycles of charge and discharge were performed under the same conditions, the discharge capacity at the 400th cycle was measured, and the capacity retention rate of the discharge capacity at the 400th cycle relative to the discharge capacity at the first cycle was calculated.

  The capacity retention rate was 70% or higher.

(B) High-temperature storage test For each of the secondary batteries of Sample 1 to Sample 40, constant current charging was performed until the battery voltage reached 4.2 V at a constant current of 1 C, and then the charging time of 4.2 V was constant. Constant voltage charging was performed until the total reached 2.5 hours. Furthermore, after storing the secondary battery for 14 days in an environment of 80 ° C., the battery was discharged at a constant current of 0.2 C until the battery voltage reached 3.0 V, and the remaining capacity was measured. Using the discharge capacity at the first cycle measured in the cycle test of (a) as the pre-storage capacity, the maintenance ratio of the remaining capacity with respect to the pre-storage capacity was calculated.

  This was again charged and discharged under the same conditions, and the recovery capacity was measured. Using the discharge capacity at the first cycle measured in the cycle test of (a) as the pre-storage capacity, the recovery rate of the recovery capacity relative to the pre-storage capacity was calculated.

  The remaining capacity was a non-defective product with a maintenance rate of 65% or more, and the recovery capacity was a recovery rate of 85% or more.

(C) Dissolution peeling test For each of the secondary batteries of Sample 1 to Sample 40, constant current charging was performed until the battery voltage reached 4.2 V at a constant current of 1 C, and then the charging time of 4.2 V was constant. Constant voltage charging was performed until the total reached 2.5 hours. Next, each secondary battery was disassembled and the negative electrode was taken out and washed with dimethyl carbonate (DMC). Further, this negative electrode was impregnated with N-methyl-2-pyrrolidone (NMP) for 1 hour in an environment of 80 ° C. and then dried, and the peel strength between the negative electrode current collector and the negative electrode active material was measured.

  The peel strength is measured by attaching a tape to the negative electrode active material layer and pulling the tape in the arrow direction (180 ° direction) in FIG. The width of the tape was 25 mm, and the tape was pulled 60 mm in the 180 ° direction at a speed of 100 mm / min. The peel strength value was an average value between 10 mm and 60 mm, and was a value normalized by the tape width.

  Table 1 below shows the evaluation results of the secondary batteries of Sample 1 to Sample 20. Table 2 shows the evaluation results of the secondary batteries of Sample 21 to Sample 40. In the table below, “○” indicates that the negative electrode active material layer is not peeled off from the negative electrode current collector, and “×” indicates that the negative electrode active material layer is peeled off from the negative electrode current collector. To do.

  As shown in Table 1, when the electrolyte salt concentration in the electrolyte is 0.8 mol / kg, sample 5 in which the electron beam irradiation time is 0 minutes does not cause peeling of the negative electrode active material layer, but the negative electrode current collector and The peel strength of the negative electrode active material layer is lowered. The secondary batteries of Sample 6 to Sample 8 that were subjected to electron beam irradiation at the same electrolyte salt concentration (0.8 mol / kg) and polymerized (crosslinked) the binder were compared with Sample 5 that was not subjected to electron beam irradiation. As a result, the capacity retention rate, storage test maintenance rate, storage test recovery rate, and peel strength all improved. In addition, the peel strength increased as the electron beam irradiation time increased, and the battery characteristics were further improved.

  Similarly, when the electrolyte salt concentration in the electrolyte is 1.2 mol / kg and 1.8 mol / kg, the secondary battery in which the electron beam irradiation is performed and the binder is polymerized (crosslinked) The battery characteristics were improved as compared with the secondary battery that did not. Moreover, the secondary battery which has a higher characteristic was able to be obtained as the irradiation time of the electron beam became long.

  On the other hand, in Sample 1 to Sample 4 in which the electrolyte salt concentration in the electrolyte is 0.3 mol / kg, the electrolyte salt concentration is low, so that the negative electrode active material layer does not peel or peel off regardless of the electron beam irradiation time. However, since the electrolyte salt concentration is low, the battery reaction does not occur sufficiently and the battery characteristics are lowered.

  Further, in Sample 17 to Sample 20 in which the electrolyte salt concentration in the electrolyte is 1.9 mol / kg, the electrolyte salt concentration is too high, and thus the adhesion between the negative electrode current collector and the negative electrode active material layer regardless of the electron beam irradiation time. Of the battery and the negative electrode active material are peeled off and peeled off, and the battery characteristics are also deteriorated.

  Further, as shown in Table 2, when the electrolyte salt concentration in the electrolyte is 0.8 mol / kg, the sample 25 having a heating temperature of 25 ° C. does not peel off the negative electrode active material layer, but the negative electrode current collector and The peel strength of the negative electrode active material layer is lowered. The secondary batteries of Sample 26 to Sample 28, in which the heating temperature is set to 180 ° C. to 220 ° C. with the same electrolyte salt concentration and the binder is polymerized (crosslinked), the capacity maintenance rate and the storage test are maintained as compared with Sample 25. Rate, storage test recovery rate and peel strength all improved. Moreover, as the heating temperature was increased, the peel strength was increased, and the battery characteristics were further improved.

  In Sample 29 and Sample 33, the electrolyte salt concentration is higher than in Sample 25, and thus the negative electrode active material layer peels off. However, in Samples 30 to 32 and Samples 34 to 36 where the heating temperature is 180 ° C. or higher, the peel strength is improved, and the capacity retention rate, storage test retention rate, storage test recovery rate, and peel strength are all good. Value.

  In Samples 21 to 24, as in Samples 1 to 4, the electrolyte salt concentration is too low, so that the negative electrode does not peel off, but the battery reaction does not occur sufficiently and the battery characteristics deteriorate. In addition, since Sample 37 to Sample 40 have an electrolyte salt concentration that is too high, as in Samples 17 to 20, the negative electrode active material layer peels off even when the binder in the negative electrode active material layer is polymerized (crosslinked). Battery characteristics will deteriorate.

  From the above evaluation, in the secondary battery having an electrolyte salt concentration of 0.8 mol / kg or more and 1.8 mol / kg or less, the negative electrode active can be obtained regardless of whether electron beam irradiation or heating in vacuum is used. If the binder in the material layer is polymerized (crosslinked) and the peel strength is 4 mN / mm or more, a secondary battery having a good capacity retention rate, storage test maintenance rate, and storage test recovery rate can be obtained. I understand.

<Example 2>
In Example 2, the negative electrode active material layer is heated to adjust the amount of fluorine in the negative electrode active material layer to evaluate battery performance. The amount of fluorine in the negative electrode active material layer is a calorific value within a range of 230 ° C. or higher and 370 ° C. or lower where a reaction peak between lithium and fluorine is present when the negative electrode active material layer in a charged state is subjected to differential scanning calorimetry. It is shown by the difference between the maximum value of the quantity and the calorific value at 100 ° C.

<Sample 41>
[Production of positive electrode]
A sample except that the mass ratio of lithium cobaltate (LiCoO ₂ ) that is a positive electrode active material, graphite that is a conductive agent, and polyvinylidene fluoride (PVdF) that is a binder is 91: 6: 10 In the same manner as in Example 1, a positive electrode was produced.

[Production of negative electrode]
A pulverized graphite powder as a negative electrode active material and polyvinylidene fluoride as a binder are uniformly mixed so as to have a mass ratio of 90:10, and this is dispersed in N-methyl-2-pyrrolidone to form a slurry. A negative electrode mixture was prepared. Next, this slurry-like negative electrode mixture is uniformly applied to both sides of a negative electrode current collector made of a copper (Cu) foil having a thickness of 15 μm at a thickness of 50 μm, and dried under reduced pressure for 10 minutes in an atmosphere of 120 ° C. Thus, a negative electrode active material layer was formed. Next, this was pressure-molded with a roll press and further heat-treated at 80 ° C. to obtain a negative electrode sheet, which was cut into a strip shape. The heat treatment was performed by exposing the electrode to a specified temperature for 8 hours in an oven under an argon (Ar) atmosphere.

  Subsequently, a negative electrode terminal made of a nickel (Ni) ribbon was welded to a portion where the negative electrode active material layer was not formed on the negative electrode current collector. The nickel (Ni) ribbon was provided with an adhesive film made of acid-modified polypropylene at a portion facing the laminate film when it was later sheathed with a laminate film.

[Formation of gel electrolyte layer]
As a non-aqueous solvent, a mixed solvent in which ethylene carbonate (EC) and propylene carbonate (PC) are mixed at a mass ratio of 1: 1 is used, and lithium hexafluorophosphate (LiPF ₆ ) that is an electrolyte salt is used as the mixed solvent. Was dissolved so that the molar concentration was 0.3 mol / kg to prepare a non-aqueous electrolyte. As a matrix polymer, a copolymer having a number average molecular weight of 700,000 obtained by copolymerizing vinylidene fluoride (VdF) and hexafluoropropylene (HFP) at a mass ratio of 93: 7, and dimethyl carbonate (DMC) as a diluent solvent. The matrix polymer, the non-aqueous electrolyte, and the diluting solvent were mixed at a mass ratio of 1:10:10 and dissolved at 70 ° C. to obtain a sol electrolyte.

  Next, a gel electrolyte layer having a thickness of 20 μm is formed on the surfaces of the positive electrode and the negative electrode by applying the above sol electrolyte on both surfaces of the positive electrode and the negative electrode and volatilizing the diluting solvent with hot air at 100 ° C. did. Then, the positive electrode and negative electrode in which the gel electrolyte layer was formed were laminated | stacked and wound through the separator which consists of a 20-micrometer-thick porous polyethylene film, and the battery element was produced.

  Furthermore, the produced battery element was covered with an aluminum laminate film and sealed to obtain a secondary battery. The same aluminum laminate film as that of Sample 1 was used.

  The secondary battery had a calorific value of 550 J / g in the range of 230 ° C. or higher and 370 ° C. or lower when the negative electrode active material layer was charged by differential scanning calorimetry. Further, the difference between the maximum calorific value by differential scanning calorimetry of the negative electrode active material layer during charging and the calorific value at 100 ° C. was 1.80 W / g.

The above calorific value and the difference between the maximum calorific value and the calorific value at 100 ° C. (hereinafter referred to as “calorific value difference”) were measured by the following procedure. First, after charging the secondary battery so that the battery voltage was 4.20 V, this was disassembled and the negative electrode was taken out and washed with dimethyl carbonate (DMC). Next, 4 mg of the negative electrode active material layer of this negative electrode was sampled and subjected to differential scanning calorimetry, and the calorific value at 230 ° C to 370 ° C and the calorific value difference were measured. In the differential scanning calorimetry, a differential scanning calorimeter DSC220U manufactured by Seiko Instruments Inc. was used, the reference material used for the measurement was alumina (Al ₂ O ₃ ), and the scanning speed was 10 ° C./min.

<Sample 42>
A secondary battery was fabricated in the same manner as Sample 41 except that the temperature for the heat treatment of the negative electrode was 150 ° C. The calorific value by differential scanning calorimetry of the negative electrode active material layer of this secondary battery was 450 J / g, and the calorific value difference was 1.60 W / g.

<Sample 43>
A secondary battery was fabricated in the same manner as Sample 41 except that the temperature of the negative electrode heat treatment was 200 ° C. The calorific value by differential scanning calorimetry of the negative electrode active material layer of this secondary battery was 400 J / g, and the calorific value difference was 1.40 W / g.

<Sample 44>
A secondary battery was fabricated in the same manner as Sample 41 except that the temperature of the negative electrode heat treatment was 220 ° C. The calorific value of the negative electrode active material layer of this secondary battery by differential scanning calorimetry was 300 J / g, and the calorific value difference was 1.30 W / g.

<Sample 45>
A secondary battery was fabricated in the same manner as Sample 41 except that the molar concentration of lithium hexafluorophosphate (LiPF ₆ ) in the non-aqueous electrolyte was 0.8 mol / kg.

<Sample 46>
A secondary battery is fabricated in the same manner as Sample 41 except that the molar concentration of lithium hexafluorophosphate (LiPF ₆ ) in the non-aqueous electrolyte is 0.8 mol / kg and the temperature of the negative electrode is 150 ° C. did. The calorific value by differential scanning calorimetry of the negative electrode active material layer of this secondary battery was 450 J / g, and the calorific value difference was 1.60 W / g.

<Sample 47>
A secondary battery is fabricated in the same manner as Sample 41 except that the molar concentration of lithium hexafluorophosphate (LiPF ₆ ) in the non-aqueous electrolyte is 0.8 mol / kg, and the temperature of the negative electrode is 200 ° C. did. The calorific value by differential scanning calorimetry of the negative electrode active material layer of this secondary battery was 400 J / g, and the calorific value difference was 1.40 W / g.

<Sample 48>
A secondary battery was fabricated in the same manner as Sample 41, except that the molar concentration of lithium hexafluorophosphate (LiPF ₆ ) in the non-aqueous electrolyte was 0.8 mol / kg and the temperature of the negative electrode heat treatment was 220 ° C. did. The calorific value of the negative electrode active material layer of this secondary battery by differential scanning calorimetry was 300 J / g, and the calorific value difference was 1.30 W / g.

<Sample 49>
A secondary battery was fabricated in the same manner as in Sample 41 except that the molar concentration of lithium hexafluorophosphate (LiPF ₆ ) in the nonaqueous electrolytic solution was changed to 1.2 mol / kg.

<Sample 50>
A secondary battery is fabricated in the same manner as Sample 41 except that the molar concentration of lithium hexafluorophosphate (LiPF ₆ ) in the non-aqueous electrolyte is 1.2 mol / kg and the temperature of the negative electrode is 150 ° C. did. The calorific value by differential scanning calorimetry of the negative electrode active material layer of this secondary battery was 450 J / g, and the calorific value difference was 1.60 W / g.

<Sample 51>
A secondary battery is fabricated in the same manner as Sample 41 except that the molar concentration of lithium hexafluorophosphate (LiPF ₆ ) in the non-aqueous electrolyte is 1.2 mol / kg and the temperature of the negative electrode heat treatment is 200 ° C. did. The calorific value by differential scanning calorimetry of the negative electrode active material layer of this secondary battery was 400 J / g, and the calorific value difference was 1.40 W / g.

<Sample 52>
A secondary battery is fabricated in the same manner as Sample 41 except that the molar concentration of lithium hexafluorophosphate (LiPF ₆ ) in the non-aqueous electrolyte is 1.2 mol / kg and the temperature of the negative electrode is 220 ° C. did. The calorific value of the negative electrode active material layer of this secondary battery by differential scanning calorimetry was 300 J / g, and the calorific value difference was 1.30 W / g.

<Sample 53>
A secondary battery was fabricated in the same manner as in Sample 41 except that the molar concentration of lithium hexafluorophosphate (LiPF ₆ ) in the nonaqueous electrolytic solution was 1.8 mol / kg.

<Sample 54>
A secondary battery was fabricated in the same manner as Sample 41, except that the molar concentration of lithium hexafluorophosphate (LiPF ₆ ) in the non-aqueous electrolyte was 1.8 mol / kg and the heat treatment temperature of the negative electrode was 150 ° C. did. The calorific value by differential scanning calorimetry of the negative electrode active material layer of this secondary battery was 450 J / g, and the calorific value difference was 1.60 W / g.

<Sample 55>
A secondary battery was fabricated in the same manner as Sample 41, except that the molar concentration of lithium hexafluorophosphate (LiPF ₆ ) in the non-aqueous electrolyte was 1.8 mol / kg and the temperature of the negative electrode heat treatment was 200 ° C. did. The calorific value by differential scanning calorimetry of the negative electrode active material layer of this secondary battery was 400 J / g, and the calorific value difference was 1.40 W / g.

<Sample 56>
A secondary battery was fabricated in the same manner as Sample 41 except that the molar concentration of lithium hexafluorophosphate (LiPF ₆ ) in the non-aqueous electrolyte was 1.8 mol / kg and the heat treatment temperature of the negative electrode was 220 ° C. did. The calorific value of the negative electrode active material layer of this secondary battery by differential scanning calorimetry was 300 J / g, and the calorific value difference was 1.30 W / g.

<Sample 57>
A secondary battery was fabricated in the same manner as Sample 41 except that the molar concentration of lithium hexafluorophosphate (LiPF ₆ ) in the nonaqueous electrolytic solution was 1.9 mol / kg.

<Sample 58>
A secondary battery was fabricated in the same manner as Sample 41, except that the molar concentration of lithium hexafluorophosphate (LiPF ₆ ) in the non-aqueous electrolyte was 1.9 mol / kg and the heat treatment temperature of the negative electrode was 150 ° C. did. The calorific value by differential scanning calorimetry of the negative electrode active material layer of this secondary battery was 450 J / g, and the calorific value difference was 1.60 W / g.

<Sample 59>
A secondary battery is fabricated in the same manner as Sample 41 except that the weight molar concentration of lithium hexafluorophosphate (LiPF ₆ ) in the non-aqueous electrolyte is 1.9 mol / kg and the temperature of the negative electrode is 200 ° C. did. The calorific value by differential scanning calorimetry of the negative electrode active material layer of this secondary battery was 400 J / g, and the calorific value difference was 1.40 W / g.

<Sample 60>
A secondary battery is fabricated in the same manner as Sample 41 except that the molar concentration of lithium hexafluorophosphate (LiPF ₆ ) in the non-aqueous electrolyte is 1.9 mol / kg and the temperature of the negative electrode heat treatment is 220 ° C. did. The calorific value of the negative electrode active material layer of this secondary battery by differential scanning calorimetry was 300 J / g, and the calorific value difference was 1.30 W / g.

[Characteristic evaluation]
(A) High-temperature storage test For each of the secondary batteries of Sample 41 to Sample 60, constant current charging was performed until the battery voltage reached 4.2 V at a constant current of 1 C, and then the charging time of 4.2 V was constant. Constant voltage charging was performed until the total reached 2.5 hours. Next, constant current discharge was performed at a constant current of 1 C until the battery voltage reached 3.0 V, and the discharge capacity was measured to obtain the capacity before storage.

  Subsequently, for each of the secondary batteries of the other samples 41 to 60, constant current charging was performed until the battery voltage reached 4.2V at a constant current of 1C, and then the total charging time at a constant voltage of 4.2V. Was charged at a constant voltage until 2.5 hours. Further, after storing the secondary battery in an environment of 60 ° C. for 14 days, the battery is measured at a constant current of 0.2 C until the battery voltage reaches 3.0 V, and the remaining capacity is measured. The maintenance rate of the remaining capacity was calculated.

  Furthermore, this was again charged and discharged under the same conditions, the recovery capacity was measured, and the recovery rate of the recovery capacity relative to the capacity before storage was calculated.

  The remaining capacity was a non-defective product with a maintenance rate of 65% or more, and the recovery capacity was a recovery rate of 85% or more.

(B) Disassembly observation About each secondary battery of the sample 41 thru | or the sample 60 after a storage test, the battery was disassembled and the mode of the negative electrode active material layer was confirmed.

(C) Nail penetration test For each of the secondary batteries of sample 41 to sample 60, constant current charging was performed at a constant current of 1 C until the battery voltage reached 4.35 V, and then a diameter of 2.5 mm in the thickness direction of the battery. The maximum temperature of the battery was measured by penetrating the nail.

  Table 3 below shows the evaluation results of the secondary batteries of Sample 41 to Sample 60. In the table below, the negative electrode active material layer is not peeled off from the negative electrode current collector, “◯”, the peel strength between the negative electrode current collector and the negative electrode active material layer is low, and the negative electrode active material layer is What was peeled off from the negative electrode collector was set as "x". In addition, in the nail penetration test, the battery was abnormally heated and gas was ejected as “gas ejection”. The battery from which the gas was ejected had a maximum temperature of 300 ° C. or higher.

  As shown in Table 3, when the electrolyte salt concentration in the electrolyte was 0.8 mol / kg, the sample 45 having a heating temperature of 80 ° C. had peeled off the negative electrode active material layer. Further, in the nail penetration test, the battery generated abnormal heat and gas was ejected. In the same electrolyte salt concentration (0.8 mol / kg), the heating temperature of the negative electrode was set to 150 ° C., which is higher than the melting point of the binder, and the amount of fluorine in the negative electrode active material layer was reduced. In the secondary battery, the storage test retention rate, the storage test recovery rate, and the peel strength were all improved as compared with Sample 45. Moreover, as the heating temperature of the negative electrode was increased, the battery characteristics were further improved, and the maximum temperature reached during the nail penetration test was also lowered.

  Similarly, in the case of Sample 49 to Sample 56 where the electrolyte salt concentration in the electrolyte is 1.2 mol / kg and 1.8 mol / kg, the heating temperature of the negative electrode is set to 150 ° C. or higher, which is equal to or higher than the melting point of the binder, The secondary battery in which the amount of fluorine in the negative electrode active material layer is reduced improves the battery characteristics as compared with the secondary batteries of Sample 49 and Sample 53, which have a lower heating temperature, and the battery characteristics increase as the heating temperature increases. I was able to improve. In addition, gas ejection during the nail penetration test was suppressed, and the maximum temperature reached by the battery could be lowered as the heating temperature increased.

  On the other hand, in Sample 41 to Sample 44 in which the electrolyte salt concentration in the electrolyte was 0.3 mol / kg, the electrolyte salt concentration was low, so that the negative electrode active material layer did not peel or peel off regardless of the heating temperature of the negative electrode. However, since the electrolyte salt concentration is low, the battery reaction does not occur sufficiently, and the battery characteristics are very low.

  Further, in Sample 57 to Sample 60 in which the electrolyte salt concentration in the electrolyte is 1.9 mol / kg, the electrolyte salt concentration is too high, and thus the negative electrode active material is peeled off and peeled off even when the heating temperature of the negative electrode is 200 ° C. As a result, the battery characteristics also deteriorate. Moreover, since electrolyte salt concentration is high, the adhesiveness of a negative electrode active material layer and a negative electrode collector falls, and a preservation | save test maintenance rate and a preservation | save test recovery rate will fall.

  From the above evaluation, in a secondary battery having an electrolyte salt concentration of 0.8 mol / kg or more and 1.8 mol / kg or less, the negative electrode is heated at a temperature equal to or higher than the melting point of the binder contained in the negative electrode active material layer. It was found that the increase in battery temperature can be suppressed without deteriorating the storage test maintenance rate and the storage test recovery rate.

  That is, the calorific value by differential scanning calorimetry of the negative electrode active material layer during charging is 450 J / g or less within the range of 230 ° C. or more and 370 ° C. or less, or the difference between the maximum calorific value and the calorific value at 100 ° C. It was found that by setting the power to 1.60 W / g or less, both high battery characteristics and high safety can be achieved.

  Also, the calorific value of the negative electrode active material layer during charging is 400 J / g or less within the range of 230 ° C. or higher and 370 ° C. or lower, or the difference between the maximum calorific value and the calorific value at 100 ° C. It was found that by setting it to 1.40 W / g or less, the maximum temperature reached during the nail penetration test can be made less than 100 ° C., and thus safety can be further improved.

  Although one embodiment of the present invention has been specifically described above, the present invention is not limited to the above-described embodiment, and various modifications based on the technical idea of the present invention are possible.

  For example, the numerical values given in the above-described embodiment are merely examples, and different numerical values may be used as necessary.

  Further, the negative electrode and electrolyte of the secondary battery of the present invention may be applied not only to a battery using a laminate film as an exterior but also to a battery using a battery can as an exterior.

It is a basic diagram which shows the example of 1 structure of the secondary battery concerning one Embodiment of this invention. It is a basic diagram which shows the example of 1 structure of the battery element accommodated in the secondary battery concerning one Embodiment of this invention. It is a basic diagram which shows the example of 1 structure of the battery element accommodated in the secondary battery concerning one Embodiment of this invention. It is a basic diagram which shows the measuring method of the tensile strength of the secondary battery concerning one Embodiment of this invention. It is sectional drawing which shows one structural example of the laminate film used for the secondary battery concerning one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Secondary battery 2a ... Positive electrode terminal 2b ... Negative electrode terminal 3a, 3b ... Separator 4 ... Laminate film 4a ... Metal foil 4b ... Outer resin layer 4c ... Inner side Resin layer 5 ... Recess 10 ... Battery element 11 ... Positive electrode 11a ... Positive electrode active material layer 11b ... Positive electrode current collector 12 ... Negative electrode 12a ... Negative electrode active material layer 12b ...・ Negative electrode current collector 13 ... Separator

Claims (12)

A positive electrode;
A negative electrode provided with a negative electrode active material layer on at least one surface of the negative electrode current collector;
Electrolyte,
In a secondary battery having the positive electrode, the negative electrode, and a laminate film exterior material containing the electrolyte,
The non-aqueous solvent contained in the electrolyte contains a cyclic carbonate in an amount of 80% to 100% of the total non-aqueous solvent,
The concentration of the electrolyte salt contained in the electrolyte is 0.8 mol / kg or more and 1.8 mol / kg or less,
The negative electrode active material layer contains a polymer containing a repeating unit derived from vinylidene fluoride as a component,
A secondary battery, wherein a peel strength between the negative electrode active material layer and the negative electrode current collector is 4 mN / mm or more after the negative electrode active material layer is immersed in a solvent. The non-aqueous solvent of the electrolyte is ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), or diethyl carbonate (DEC). The secondary battery according to claim 1, wherein one or more kinds including at least one of (PC) are mixed. The secondary battery according to claim 2, wherein the non-aqueous solvent contains propylene carbonate (PC) in an amount of 30% to 80%. 2. The secondary battery according to claim 1, wherein the electrolyte is a gel electrolyte containing a vinylidene fluoride component as a matrix polymer in an amount of 70% by mass to 100% by mass. The secondary battery according to claim 1, wherein the solvent is N-methyl-2-pyrrolidone (NMP). A positive electrode;
A negative electrode provided with a negative electrode active material layer on at least one surface of the negative electrode current collector;
Electrolyte,
In a secondary battery having the positive electrode, the negative electrode, and a laminate film exterior material containing the electrolyte,
The non-aqueous solvent contained in the electrolyte contains a cyclic carbonate in an amount of 80% to 100% of the total non-aqueous solvent,
The concentration of the electrolyte salt contained in the electrolyte is 0.8 mol / kg or more and 1.8 mol / kg or less,
The negative electrode active material layer contains a polymer containing a repeating unit derived from vinylidene fluoride as a component,
A secondary battery, wherein the negative electrode active material layer has a calorific value of 450 J / g or less within a range of 230 ° C. or higher and 370 ° C. or lower when the negative electrode active material layer is charged. The secondary battery according to claim 6, wherein the calorific value is 400 J / g or less. The non-aqueous solvent of the electrolyte is ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), or diethyl carbonate (DEC). The secondary battery according to claim 6, wherein one or more types including at least one of (PC) are mixed. The secondary battery according to claim 8, wherein the non-aqueous solvent contains 30% or more and 80% or less of propylene carbonate (PC). The secondary battery according to claim 6, wherein the electrolyte is a gel electrolyte containing 70% by mass or more and 100% by mass or less of a vinylidene fluoride component as a matrix polymer. A positive electrode;
A negative electrode provided with a negative electrode active material layer on at least one surface of the negative electrode current collector;
Electrolyte,
In a secondary battery having the positive electrode, the negative electrode, and a laminate film exterior material containing the electrolyte,
The non-aqueous solvent contained in the electrolyte contains a cyclic carbonate in an amount of 80% to 100% of the total non-aqueous solvent,
The concentration of the electrolyte salt contained in the electrolyte is 0.8 mol / kg or more and 1.8 mol / kg or less,
The negative electrode active material layer contains a polymer containing a repeating unit derived from vinylidene fluoride as a component,
A secondary battery, wherein a difference between a maximum calorific value obtained by differential scanning calorimetry of the negative electrode active material layer during charging and a calorific value at 100 ° C. is 1.60 W / g or less. The secondary battery according to claim 11, wherein a difference between the maximum value of the heat generation amount and the heat generation amount at 100 ° C. is 1.40 W / g or less.

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