JP2006108113A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery with an excellent discharge capacity, a heavy-current discharging property and a charging/discharging cycle property. <P>SOLUTION: This nonaqueous electrolyte secondary battery is provided with an electrode group 22 provided with a positive electrode 32 comprising a positive electrode current collector 25 and a positive electrode active material layer 24 and a negative electrode 33 comprising a negative electrode current collector 27 and a negative electrode active material layer 26 and a separator 23, a nonaqueous electrolyte impregnated in the electrode group 22 and comprising a nonaqueous solvent and lithium salt dissolved in the nonaqueous solvent, and a case material 21 housing the electrode group 22 and made of a sheet containing a resin layer and having a thickness of 0.5 mm or less. The porosity of the positive electrode active material layer 24 is low than the porosity of the negative electrode active material layer 26. The thickness of the positive electrode active material layer 24 is 10-60 μm, and the thickness of the negative electrode active material layer 26 is 10-65 μm. The nonaqueous solvent contains γ-butyrolactone which is 40-95 vol.% of the whole nonaqueous solvent. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

Currently, lithium ion secondary batteries are commercialized as non-aqueous electrolyte secondary batteries for portable devices such as mobile phones. In this battery, a lithium cobalt oxide (LiCoO ₂ ) is used for the positive electrode, a graphite material or a carbonaceous material is used for the negative electrode, an organic solvent in which a lithium salt is dissolved in a nonaqueous electrolytic solution, and a porous film is used for the separator. A non-aqueous solvent having a low viscosity and a low boiling point is used as the solvent for the electrolytic solution.

  For example, Patent Document 1 (Japanese Patent Laid-Open No. 4-14769) discloses an electrolysis in which a mixed solvent composed of propylene carbonate, ethylene carbonate and γ-butyrolactone is mainly used, and the ratio of γ-butyrolactone is 10 to 50% by volume of the whole solvent. A non-aqueous electrolyte secondary battery with a solution is described. This publication aims to improve the low-temperature discharge characteristics of a cylindrical non-aqueous electrolyte secondary battery.

  By the way, it is desired to reduce the thickness of the battery as the portable device becomes thinner. For this purpose, it is necessary to reduce the thickness of the exterior material that houses the positive electrode, the negative electrode, the separator, and the non-aqueous electrolyte. However, a lithium ion secondary battery provided with a non-aqueous electrolyte containing a solvent having a γ-butyrolactone content of 10 to 50% by volume described in Patent Document 1 (Japanese Patent Laid-Open No. 4-14769) described above is The gas generation from the negative electrode during the initial charge is increased, or when stored at a high temperature of 60 ° C. or higher, the positive electrode and the non-aqueous electrolyte react to cause oxidative decomposition of the non-aqueous electrolyte, resulting in gas generation. For this reason, when the thickness of the exterior material is reduced, there arises a problem that the exterior material is expanded and deformed by the generation of gas. If the exterior material is deformed, the battery may not fit in the electronic device, or the electronic device may malfunction.

On the other hand, in Patent Document 2 (Japanese Patent Laid-Open No. 11-97062), a nonaqueous electrolytic solution in which lithium borofluoride (LiBF ₄ ) is dissolved in a solvent having a γ-butyrolactone ratio of 100% by volume is provided. A water electrolyte secondary battery is disclosed. This publication aims to suppress the oxidative decomposition of a positive electrode containing a lithium cobalt composite oxide as an active material by a non-aqueous electrolyte.

However, a nonaqueous electrolytic solution in which lithium borofluoride (LiBF ₄ ) is dissolved in a solvent having a γ-butyrolactone ratio of 100% by volume disclosed in Patent Document 2 (Japanese Patent Application Laid-Open No. 11-97062) includes: Reductive decomposition is likely to occur due to reaction. As a result, current concentration is likely to occur in the negative electrode, so that lithium metal is deposited on the negative electrode surface, or the impedance at the negative electrode interface is increased, the charge / discharge efficiency of the negative electrode is lowered, and charge / discharge cycle characteristics are degraded.

Further, in non-aqueous electrolyte secondary batteries, further improvements in large current discharge characteristics and charge / discharge cycle characteristics are desired.
JP-A-4-14769 JP-A-11-97062

  An object of the present invention is to provide a non-aqueous electrolyte secondary battery excellent in discharge capacity, large current discharge characteristics and charge / discharge cycle characteristics.

According to the present invention, an electrode group comprising a positive electrode, a negative electrode containing a material that absorbs and releases lithium ions, and a separator disposed between the positive electrode and the negative electrode; the electrode group impregnated with a nonaqueous solvent And a non-aqueous electrolyte solution containing a lithium salt dissolved in the non-aqueous solvent; an exterior material made of a sheet having a thickness of 0.5 mm or less containing the electrode group and including a resin layer;
A non-aqueous electrolyte secondary battery is provided in which the non-aqueous solvent contains γ-butyrolactone in an amount of more than 50% by volume and not more than 95% by volume of the whole non-aqueous solvent.

According to the present invention, an electrode group comprising a positive electrode, a negative electrode containing a material that absorbs and releases lithium ions, and a separator disposed between the positive electrode and the negative electrode; the electrode group impregnated with a nonaqueous solvent And a non-aqueous electrolyte solution containing a lithium salt dissolved in the non-aqueous solvent; an exterior material having a thickness of 0.3 mm or less in which the electrode group is housed;
A non-aqueous electrolyte secondary battery is provided in which the non-aqueous solvent contains γ-butyrolactone in an amount of more than 50% by volume and not more than 95% by volume of the whole non-aqueous solvent.

According to the present invention, a positive electrode including a positive electrode current collector and a positive electrode active material layer supported on one or both surfaces of the positive electrode current collector, and supported on one or both surfaces of the negative electrode current collector and the negative electrode current collector. An electrode group comprising a negative electrode including a negative electrode active material layer containing a material that absorbs and releases lithium ions; and a separator disposed between the positive electrode and the negative electrode; and a nonaqueous solvent impregnated in the electrode group; A non-aqueous electrolyte containing a lithium salt dissolved in the non-aqueous solvent; an exterior material made of a sheet having a thickness of 0.5 mm or less containing the electrode group and including a resin layer;
The porosity of the positive electrode active material layer is lower than the porosity of the negative electrode active material layer, and the thickness of the positive electrode active material layer is 10 to 100 μm,
A non-aqueous electrolyte secondary battery in which the non-aqueous solvent contains γ-butyrolactone in an amount of 40% by volume to 95% by volume of the whole non-aqueous solvent is provided.

According to the present invention, a positive electrode including a positive electrode current collector and a positive electrode active material layer supported on one or both surfaces of the positive electrode current collector, and supported on one or both surfaces of the negative electrode current collector and the negative electrode current collector. An electrode group comprising a negative electrode including a negative electrode active material layer containing a material that absorbs and releases lithium ions; and a separator disposed between the positive electrode and the negative electrode; and a nonaqueous solvent impregnated in the electrode group; A non-aqueous electrolyte solution containing a lithium salt dissolved in the non-aqueous solvent; an exterior material having a thickness of 0.3 mm or less in which the electrode group is housed;
The porosity of the positive electrode active material layer is lower than the porosity of the negative electrode active material layer, the thickness of the positive electrode active material layer is 10 to 100 μm, and the non-aqueous solvent is γ-butyrolactone is non-aqueous. A nonaqueous electrolyte secondary battery containing 40% by volume or more and 95% by volume or less of the entire solvent is provided.

  According to the present invention, there is provided a non-aqueous electrolyte secondary battery in which deformation of an exterior material when stored at a high temperature is suppressed and weight energy density, volume energy density, large current discharge characteristics and charge / discharge cycle characteristics are improved. can do.

  The first non-aqueous electrolyte secondary battery according to the present invention includes an electrode group including a positive electrode, a negative electrode including a material that absorbs and releases lithium ions, and a separator disposed between the positive electrode and the negative electrode; A non-aqueous electrolyte containing a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent; and an exterior material in which the electrode group is housed. The non-aqueous solvent contains γ-butyrolactone in an amount of more than 50% by volume and not more than 95% by volume of the whole non-aqueous solvent.

  In this secondary battery, the positive electrode, the negative electrode, and the separator do not have to be integrated, but it is preferable that they are integrated under the conditions described in (a) or (b) below. .

  (A) Adhesion in which the positive electrode and the separator are integrated by an adhesive polymer present at at least a part of these boundaries, and the negative electrode and the separator are present at at least a part of these boundaries It is integrated with a polymer having properties. In particular, the positive electrode and the separator are integrated with an adhesive polymer scattered in the interior and boundary thereof, and the negative electrode and the separator have adhesiveness scattered in the interior and boundary thereof. It is desirable that they are integrated by a polymer.

  (B) The positive electrode, the negative electrode, and the separator are integrated by thermosetting the binder contained in the positive electrode and the negative electrode.

  By adopting the configuration of (a) or (b), the swelling of the exterior material can be further reduced.

  The secondary battery preferably has a product of battery capacity (Ah) and 1 kHz battery internal impedance (mΩ) of 10 mΩ · Ah or more and 110 mΩ · Ah or less. By setting the product of the capacity and the impedance within the above range, the large current discharge characteristics and the charge / discharge cycle characteristics can be further improved. Here, the battery capacity is a nominal capacity or a discharge capacity when discharged at 0.2C. A more preferable range is 20 mΩ · Ah or more and 60 mΩ · Ah or less.

  The product of the battery capacity and the impedance can be 10 mΩ · Ah or more and 110 mΩ · Ah or less, for example, by the manufacturing method (I) described later or the manufacturing method (II) described later. However, in (I), the addition amount of the adhesive polymer, the distribution of the adhesive polymer, and the initial charging conditions are set so that the product of the battery capacity and the impedance is 10 mΩ · Ah or more and 110 mΩ · Ah or less. In (II), the temperature, press pressure, and initial charge condition when forming the electrode group are set so that the product of the battery capacity and impedance is 10 mΩ · Ah or more and 110 mΩ · Ah or less.

  Hereinafter, a non-aqueous electrolyte secondary battery including an electrode group that satisfies the above-described (a) will be described.

1) Positive electrode This positive electrode has a structure in which a positive electrode layer containing an active material is supported on one side or both sides of a current collector.

  The positive electrode layer includes a positive electrode active material and a conductive agent. In addition, the positive electrode layer includes a binder that binds the positive electrode active materials to each other, apart from the adhesive polymer.

Examples of the positive electrode active material include various oxides such as manganese dioxide, lithium manganese composite oxide, lithium-containing nickel oxide, lithium-containing cobalt oxide, lithium-containing nickel cobalt oxide, lithium-containing iron oxide, and lithium. Examples thereof include vanadium oxide and chalcogen compounds such as titanium disulfide and molybdenum disulfide. Among them, when a lithium-containing cobalt oxide (for example, LiCoO ₂ ), a lithium-containing nickel cobalt oxide (for example, LiNi _0.8 Co _0.2 O ₂ ), or a lithium manganese composite oxide (for example, LiMn ₂ O ₄ , LiMnO ₂ ) is used. This is preferable because a high voltage can be obtained.

  Examples of the conductive agent include acetylene black, carbon black, and graphite.

  The binder has a function of holding the active material on the current collector and connecting the active materials to each other. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), ethylene-propylene-diene copolymer (EPDM), and styrene-butadiene rubber (SBR).

  The mixing ratio of the positive electrode active material, the conductive agent and the binder is preferably in the range of 80 to 95% by weight of the positive electrode active material, 3 to 20% by weight of the conductive agent, and 2 to 7% by weight of the binder.

  As the current collector, a conductive substrate having a porous structure or a non-porous conductive substrate can be used. These conductive substrates can be formed from, for example, aluminum, stainless steel, or nickel.

Among them, it is preferable to use a conductive substrate having a two-dimensional porous structure in which holes having a diameter of 3 mm or less exist at a rate of 1 or more per 10 cm ² . That is, when the diameter of the hole opened in the conductive substrate is larger than 3 mm, there is a possibility that sufficient positive electrode strength cannot be obtained. On the other hand, if the proportion of holes having a diameter of 3 mm or less is smaller than the above range, it is difficult to uniformly infiltrate the non-aqueous electrolyte into the electrode group, so that sufficient charge / discharge cycle characteristics may not be obtained. . The diameter of the hole is more preferably in the range of 0.1 to 1 mm. Moreover, it is more preferable that the existence ratio of the holes is in the range of 10 to 20 per 10 cm ² .

The conductive substrate having a two-dimensional porous structure in which holes having a diameter of 3 mm or less are present at a rate of 1 or more per 10 cm ² is preferably in the range of 15 to 100 μm. If the thickness is less than 15 μm, sufficient positive electrode strength may not be obtained. On the other hand, if the thickness exceeds 100 μm, the battery weight and the thickness of the electrode group increase, which may make it difficult to sufficiently increase the weight energy density and volume energy density of the thin secondary battery. A more preferable range of the thickness is 30 to 80 μm.

2) Negative electrode The negative electrode has a structure in which a negative electrode layer is supported on one side or both sides of a current collector.

  The negative electrode layer includes a carbonaceous material that occludes / releases lithium ions. The negative electrode layer contains a binder for binding the negative electrode material, in addition to the adhesive polymer.

Examples of the carbonaceous material include graphite or carbonaceous materials such as graphite, coke, carbon fiber, and spherical carbon, thermosetting resin, isotropic pitch, mesophase pitch, mesophase pitch-based carbon fiber, mesophase microspheres, etc. And a mesophase pitch-based carbon fiber is preferable because of its high capacity and charge / discharge cycle characteristics), and a graphite material or a carbonaceous material obtained by heat treatment at 500 to 3000 ° C. Among them, it is preferable to use a graphitic material having graphite crystals obtained by setting the temperature of the heat treatment to 2000 ° C. or more and having a (002) plane spacing d ₀₀₂ of 0.340 nm or less. A non-aqueous electrolyte secondary battery equipped with a negative electrode containing such a graphite material as a carbonaceous material can greatly improve battery capacity and large current discharge characteristics. The spacing d ₀₀₂ is more preferably at most 0.336 nm.

  Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), ethylene-propylene-diene copolymer (EPDM), styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), and the like. be able to.

  The blending ratio of the carbonaceous material and the binder is preferably in the range of 90 to 98% by weight of the carbonaceous material and 2 to 20% by weight of the binder.

  As the current collector, a conductive substrate having a porous structure or a non-porous conductive substrate can be used. These conductive substrates can be formed from, for example, copper, stainless steel, or nickel.

Among them, it is preferable to use a conductive substrate having a two-dimensional porous structure in which holes having a diameter of 3 mm or less exist at a rate of 1 or more per 10 cm ² . That is, when the diameter of the hole of the conductive substrate is larger than 3 mm, there is a possibility that sufficient negative electrode strength cannot be obtained. On the other hand, if the proportion of holes having a diameter of 3 mm or less is smaller than the above range, it is difficult to uniformly infiltrate the non-aqueous electrolyte into the electrode group, so that sufficient charge / discharge cycle characteristics may not be obtained. . The diameter of the hole is more preferably in the range of 0.1 to 1 mm. Moreover, it is more preferable that the existence ratio of the holes is in the range of 10 to 20 per 10 cm ² .

The conductive substrate having a two-dimensional porous structure in which at least one hole having a diameter of 3 mm or less exists at a rate of 1 or more per 10 cm ² is preferably in the range of 10 to 50 μm. If the thickness is less than 10 μm, sufficient negative electrode strength may not be obtained. On the other hand, if the thickness exceeds 50 μm, the weight of the battery and the thickness of the electrode group increase, and it may be difficult to sufficiently increase the weight energy density and volume energy density of the thin secondary battery.

  The negative electrode layer is made of a metal such as aluminum, magnesium, tin, or silicon, a metal oxide, a metal sulfide, or a metal nitride, in addition to the carbon material that absorbs and releases lithium ions. It may contain a selected metal compound or lithium alloy.

  Examples of the metal oxide include tin oxide, silicon oxide, lithium titanium oxide, niobium oxide, and tungsten oxide.

  Examples of the metal sulfide include tin sulfide and titanium sulfide.

  Examples of the metal nitride include lithium cobalt nitride, lithium iron nitride, and lithium manganese nitride.

  Examples of the lithium alloy include a lithium aluminum alloy, a lithium tin alloy, a lithium lead alloy, and a lithium silicon alloy.

3) Separator This separator is formed from a porous sheet.

  For example, a porous film or a non-woven fabric can be used as the porous sheet. The porous sheet is preferably made of at least one material selected from, for example, polyolefin and cellulose. Examples of the polyolefin include polyethylene and polypropylene. Among these, a porous film made of polyethylene, polypropylene, or both is preferable because it can improve the safety of the secondary battery.

  The thickness of the porous sheet is preferably 30 μm or less. If the thickness exceeds 30 μm, the distance between the positive and negative electrodes may be increased and the internal resistance may be increased. Further, the lower limit value of the thickness is preferably 5 μm. If the thickness is less than 5 μm, the strength of the separator is remarkably lowered and an internal short circuit is likely to occur. The upper limit value of the thickness is more preferably 25 μm, and the lower limit value is more preferably 10 μm.

  The porous sheet preferably has a heat shrinkage rate of 20% or less at 120 ° C. for 1 hour. If the heat shrinkage rate exceeds 20%, it may be difficult to make the adhesive strength between the positive and negative electrodes and the separator sufficient. The heat shrinkage rate is more preferably 15% or less.

  The porous sheet preferably has a porosity in the range of 30 to 60%. This is due to the following reason. If the porosity is less than 30%, it may be difficult to obtain high electrolyte retention in the separator. On the other hand, if the porosity exceeds 60%, sufficient separator strength may not be obtained. A more preferable range of the porosity is 35 to 50%.

The porous sheet preferably has an air permeability of 600 seconds / 100 cm ³ or less. The air permeability means time (seconds) required for 100 cm ³ of air to pass through the porous sheet. If the air permeability exceeds 600 seconds / 100 cm ³ , it may be difficult to obtain high lithium ion mobility in the separator. Further, the lower limit value of the air permeability is preferably 100 seconds / 100 cm ³ . This is because if the air permeability is less than 100 seconds / 100 cm ³ , sufficient separator strength may not be obtained. The upper limit value of the air permeability is more preferably 500 seconds / 100 cm ^3, and a more preferable upper limit value is 400 seconds / 100 cm ³ . The lower limit is more preferably 150 seconds / 100 cm ³ .

4) Non-aqueous electrolyte The non-aqueous electrolyte is prepared by dissolving a lithium salt in a mixed non-aqueous solvent mainly composed of γ-butyrolactone (BL), and the composition ratio of BL is 50% by volume of the entire mixed non-aqueous solvent. More than, it is 95 volume% or less. When the ratio is 50% by volume or less, gas is likely to be generated at a high temperature. Further, when the mixed non-aqueous solvent contains BL and cyclic carbonate, the ratio of the cyclic carbonate becomes relatively high, so that the solvent viscosity increases and the conductivity of the non-aqueous electrolyte decreases. As a result, the charge / discharge cycle characteristics, the large current discharge characteristics, and the discharge characteristics under a low temperature environment around −20 ° C. are deteriorated. On the other hand, if the ratio exceeds 95% by volume, the reaction between the negative electrode and BL occurs, and the charge / discharge cycle characteristics deteriorate. That is, when the negative electrode (for example, containing a carbonaceous material that occludes and releases lithium ions) reacts with BL to cause reductive decomposition of the non-aqueous electrolyte, a coating that inhibits the charge / discharge reaction is formed on the surface of the negative electrode. The As a result, current concentration is likely to occur in the negative electrode, so that lithium metal is deposited on the negative electrode surface, or the impedance at the negative electrode interface is increased, the charge / discharge efficiency of the negative electrode is lowered, and charge / discharge cycle characteristics are degraded. A more preferable range is 60% by volume or more and 95% by volume or less. By setting it within this range, it is possible to further increase the effect of suppressing gas generation during high-temperature storage, and to further improve the discharge capacity in a low temperature environment around −20 ° C. A more preferable range is 65 volume% or more and 90 volume% or less.

  As a solvent mixed with BL, a cyclic carbonate is desirable in terms of increasing the charge / discharge efficiency of the negative electrode.

  As the cyclic carbonate, propylene carbonate (PC), ethylene carbonate (EC), vinylene carbonate (VC), trifluoropropylene carbonate (TFPC) and the like are desirable. In particular, when EC is used as a solvent mixed with BL, charge / discharge cycle characteristics and large current discharge characteristics can be significantly improved. Moreover, as another solvent mixed with BL, a third solvent consisting of at least one selected from the group consisting of PC, VC, TFPC, diethyl carbonate (DEC), methyl ethyl carbonate (MEC), and an aromatic compound, and EC The mixed solvent is desirable in terms of enhancing the charge / discharge cycle characteristics.

  Further, from the viewpoint of lowering the solvent viscosity, a low-viscosity solvent may be contained in an amount of 20% by volume or less. Examples of the low viscosity solvent include chain carbonates, chain ethers, cyclic ethers and the like.

  More preferred compositions of the non-aqueous solvent according to the present invention include BL and EC, BL and PC, BL and EC and DEC, BL and EC and MEC, BL and EC and MEC and VC, BL and EC and VC, and BL and PC. And VC, or BL, EC, PC, and VC. At this time, the volume ratio of EC is preferably 5 to 40% by volume. This is due to the following reason. If the EC ratio is less than 5% by volume, it may be difficult to cover the negative electrode surface densely with a protective film, so that the reaction between the negative electrode and BL occurs, and the charge / discharge cycle characteristics can be sufficiently improved. It can be difficult. On the other hand, if the EC ratio exceeds 40% by volume, the viscosity of the non-aqueous electrolyte solution is increased and the ionic conductivity may be lowered. Therefore, sufficient charge / discharge cycle characteristics, large current discharge characteristics, and low temperature discharge characteristics are sufficiently obtained. It can be difficult to improve. A more preferable range of the EC ratio is 10 to 35% by volume. Moreover, the solvent which consists of at least 1 sort (s) chosen from DEC, MEC, PC, and VC forms the dense protective film on the surface of a negative electrode, and makes the effect | action which reduces the interface impedance of a negative electrode. The amount of the solvent added is not particularly limited, and is set to such an amount that this action occurs. However, when the ratio of at least one solvent selected from DEC, MEC, PC and VC in the non-aqueous solvent exceeds 10% by volume, the non-aqueous electrolyte is sufficiently suppressed from being oxidatively decomposed in a high temperature environment. May be difficult, or the viscosity of the non-aqueous electrolyte solution may increase and the ionic conductivity may decrease. For this reason, it is desirable that the volume ratio of at least one solvent selected from DEC, MEC, PC and VC in the non-aqueous solvent is 10% by volume or less. A more preferable volume ratio is 2% by volume or less. The lower limit of the volume ratio is preferably 0.001% by volume, and a more preferable lower limit is 0.05% by volume.

  In particular, a non-aqueous solvent containing BL, EC and VC of more than 50% by volume and not more than 95% by volume is preferable. A non-aqueous electrolyte secondary battery comprising a non-aqueous electrolyte containing a non-aqueous solvent and a negative electrode containing a carbonaceous material that occludes and releases lithium ions can greatly reduce the impedance at the interface of the negative electrode. Since it is possible to suppress the deposition of metallic lithium on the negative electrode, the charge / discharge efficiency of the negative electrode can be improved. As a result, it is possible to suppress deformation of the exterior material by suppressing gas generation during high-temperature storage while realizing excellent large current discharge characteristics and a long life. It is estimated that the negative electrode characteristics are improved in this way due to the action described below. In the secondary battery, in addition to forming a protective film by EC on the surface of the negative electrode, a thin and dense film by VC is formed. As a result, since the reaction between BL and the negative electrode is further suppressed, it is considered that the reduction in impedance and the prevention of precipitation of metallic lithium are achieved.

  Moreover, as a non-aqueous solvent, you may use what contains BL, EC, and an aromatic compound of more than 50 volume% and 95 volume% or less instead of what has the composition mentioned above. Examples of the aromatic compound include at least one selected from benzene, toluene, xylene, biphenyl, and terphenyl. EC adheres to the surface of a negative electrode (for example, containing a carbonaceous material that occludes and releases lithium ions) to form a protective film, and can suppress the reaction between the negative electrode and BL. At this time, the volume ratio of EC is preferably 5 to 40% by volume for the same reason as described above. Further, a more preferable range of the EC ratio is 10 to 35% by volume. On the other hand, since the benzene ring of the aromatic compound is easily adsorbed on the surface of the negative electrode (for example, containing a carbonaceous material that occludes and releases lithium ions), the reaction between the negative electrode and BL can be suppressed. Therefore, a non-aqueous electrolyte solution containing a non-aqueous solvent containing BL, EC and aromatic compound in an amount of more than 50% by volume and not more than 95% by volume can sufficiently suppress the reaction between the negative electrode and BL. The charge / discharge cycle characteristics of the secondary battery can be improved. Such a non-aqueous solvent preferably further contains at least one solvent selected from DEC, MEC, PC, TFPC and VC. By adding at least one solvent selected from DEC, MEC, PC, TFPC and VC, the reaction between the negative electrode and BL can be further suppressed, so that the charge / discharge cycle characteristics can be further improved. . Of these, VC is preferable. The addition amount of the third solvent consisting of at least one selected from the aromatic compound, DEC, MEC, PC, TFPC and VC is not particularly limited, and is set to such an amount that this action occurs. However, if the ratio of the third solvent in the non-aqueous solvent exceeds 10% by volume, it may be difficult to sufficiently prevent the non-aqueous electrolyte from undergoing oxidative decomposition in a high temperature environment, or the non-aqueous electrolyte. There is a possibility that the ionic conductivity may be lowered due to an increase in the viscosity of. For this reason, the volume ratio of the third solvent in the non-aqueous solvent is desirably 10% by volume or less. A more preferable volume ratio is 2% by volume or less. The lower limit of the volume ratio is preferably 0.001% by volume, and a more preferable lower limit is 0.05% by volume.

Examples of the electrolyte contained in the non-aqueous electrolyte include lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium borofluoride (LiBF ₄ ), and lithium arsenic hexafluoride (LiAsF ₆ ). And lithium salts (electrolytes) such as lithium trifluorometasulfonate (LiCF ₃ SO ₃ ) and lithium bistrifluoromethylsulfonylimide [(LiN (CF ₃ SO ₂ ) ₂ ]), among which LiPF ₆ or LiBF ₄ It is preferable to use it.

  The amount of the electrolyte dissolved in the non-aqueous solvent is preferably 0.5 to 2.0 mol / l.

  The amount of the non-aqueous electrolyte is preferably 0.2 to 0.6 g per 100 mAh of battery unit capacity. This is due to the following reason. If the amount of nonaqueous electrolysis is less than 0.2 g / 100 mAh, the ionic conductivity of the positive electrode and the negative electrode may not be sufficiently maintained. On the other hand, if the amount of the non-aqueous electrolyte exceeds 0.6 g / 100 mAh, the amount of the electrolyte may become so large that sealing with a film exterior material may be difficult. A more preferable range of the amount of the non-aqueous electrolyte is 0.4 to 0.55 g / 100 mAh.

5) Polymer having adhesiveness It is desirable that the polymer having adhesiveness can maintain high adhesiveness in a state where a non-aqueous electrolyte is held. Furthermore, it is more preferable that such a polymer has high lithium ion conductivity. Specific examples include polyacrylonitrile (PAN), polyacrylate (PMMA), polyvinylidene fluoride (PVdF), polyvinyl chloride (PVC), and polyethylene oxide (PEO). In particular, polyvinylidene fluoride is preferable. Polyvinylidene fluoride can hold a non-aqueous electrolyte, and if it contains a non-aqueous electrolyte, it partially gels, so that the ionic conductivity can be further improved.

  The polymer having adhesiveness preferably has a porous structure having fine pores in the gaps of the positive electrode, the negative electrode, and the separator. The adhesive polymer having a porous structure can hold a non-aqueous electrolyte.

  The total amount of adhesive polymer contained in the battery is preferably 0.1 to 6 mg per 100 mAh of battery capacity. This is due to the following reason. If the total amount of the polymer having adhesiveness is less than 0.1 mg per 100 mAh of battery capacity, it may be difficult to sufficiently improve the adhesion between the positive electrode, the separator and the negative electrode. On the other hand, if the total amount exceeds 6 mg per 100 mAh of battery capacity, the lithium ion conductivity of the secondary battery may decrease and the internal resistance may increase, improving the discharge capacity, large current discharge characteristics, and charge / discharge cycle characteristics. It can be difficult to do. A more preferable range of the total amount of the polymer having adhesiveness is 0.2 to 1 mg per 100 mAh of battery capacity.

6) Exterior material As the exterior material, a first exterior material made of a sheet having a thickness of 0.5 mm or less including a resin layer or a second exterior material having a thickness of 0.3 mm or less is used. Although the first and second exterior materials are lightweight and can increase the energy density per weight of the battery, they are generated from the electrode group or the non-aqueous electrolyte in order to have flexibility. Easily deformed by gas.

  The resin layer included in the first exterior material can be formed from, for example, polyethylene, polypropylene, or the like. Specifically, the first exterior material is a sheet in which a metal layer and protective layers disposed on both surfaces of the metal layer are integrated. The metal layer serves to block moisture. Examples of the metal layer include aluminum, stainless steel, iron, copper, and nickel. Among these, aluminum that is lightweight and has a high function of blocking moisture is preferable. The metal layer may be formed from one type of metal, but may be formed from a combination of two or more types of metal layers. Of the two protective layers, the protective layer in contact with the outside serves to prevent damage to the metal layer. This external protective layer is formed of one type of resin layer or two or more types of resin layers. On the other hand, the internal protective layer plays a role of preventing the metal layer from being corroded by the non-aqueous electrolyte. This internal protective layer is formed of one type of resin layer or two or more types of resin layers. Further, a heat-fusible resin can be disposed on the surface of the internal protective layer.

  When the thickness of the first exterior material exceeds 0.5 mm, the capacity per weight of the battery decreases. The thickness of the first exterior material is preferably 0.3 mm or less, more preferably 0.25 mm or less, and most preferably 0.15 mm or less. On the other hand, if the thickness is less than 0.05 mm, deformation or breakage tends to occur. For this reason, the lower limit value of the thickness is preferably 0.05 mm. A more preferred lower limit is 0.08 mm, and a most preferred range is 0.1 mm.

  As the second exterior material, for example, a metal can or a film having a function of blocking moisture can be used. The metal can can be formed from, for example, iron, stainless steel, or aluminum. On the other hand, examples of the film include a laminate film including a metal layer and a flexible synthetic resin layer formed on at least a part of the metal layer. Examples of the metal layer include aluminum, stainless steel, iron, copper, and nickel. Among these, aluminum that is lightweight and has a high function of blocking moisture is preferable. Examples of the synthetic resin include polyethylene and polypropylene.

  If the thickness of the second exterior material is greater than 0.3 mm, the effect of thinning is small, that is, it is difficult to sufficiently increase the weight energy density. The thickness of the second exterior material is preferably 0.25 mm or less, and more preferably 0.15 mm or less. On the other hand, if the thickness is less than 0.05 mm, deformation or breakage tends to occur. For this reason, the lower limit value of the thickness is preferably 0.05 mm. A more preferred lower limit is 0.08 mm, and a most preferred range is 0.1 mm. In particular, the thickness of the second exterior material is preferably in the range of 0.05 to 0.3 mm. A more preferable range is 0.08 to 0.15 mm.

  The thickness of the exterior material is measured by the method described below. That is, in the region excluding the sealing portion of the exterior material, three points that are separated from each other by 1 cm or more are arbitrarily selected, the thickness of each point is measured, an average value is calculated, and this value is calculated as the thickness of the exterior material. Say it. In addition, when the foreign material (for example, resin) has adhered to the surface of the said exterior material, thickness is measured after removing this foreign material. For example, when PVdF adheres to the surface of the exterior material, the PVdF is removed by wiping the surface of the exterior material with a dimethylformamide solution, and then the thickness is measured.

  When the film exterior material is used, it is desirable that the electrode group is adhered to the inner surface of the exterior material by an adhesive layer formed on at least a part of the surface thereof. With such a configuration, since the exterior material can be fixed to the surface of the electrode group, it is possible to prevent the electrolyte from penetrating between the electrode group and the exterior material.

  A thin lithium ion secondary battery which is an example of this non-aqueous electrolyte secondary battery will be described in detail with reference to FIGS.

  FIG. 1 is a cross-sectional view showing a thin lithium ion secondary battery as an example of a first non-aqueous electrolyte secondary battery according to the present invention, FIG. 2 is an enlarged cross-sectional view showing part A of FIG. 1, and FIG. FIG. 2 is a schematic diagram showing the vicinity of a boundary between a positive electrode layer, a separator, and a negative electrode layer in the secondary battery of FIG. 1.

  As shown in FIG. 1, an exterior material 1 made of, for example, a film surrounds an electrode group 2. The electrode group 2 has a structure in which a laminate composed of a positive electrode, a separator, and a negative electrode is wound into a flat shape. As shown in FIG. 2, the laminate includes a separator 3, a positive electrode layer 4, a positive electrode current collector 5, a positive electrode 12 including a positive electrode layer 4, a separator 3, a negative electrode layer 6, and a negative electrode collector. A negative electrode 13 including a current collector 7 and a negative electrode layer 6, a separator 3, a positive electrode layer 4, a positive electrode current collector 5, a positive electrode 12 including a positive electrode layer 4, a separator 3, a negative electrode layer 6, and a negative electrode current collector 7 are provided. The negative electrode 13 is formed by laminating in this order. In the electrode group 2, the negative electrode current collector 7 is located in the outermost layer. An adhesive portion 8 is present on the surface of the electrode group 2. The inner surface of the exterior material 1 is bonded to the bonding portion 8. As shown in FIG. 3, adhesive polymers 9 are held in the gaps of the positive electrode layer 4, the separator 3, and the negative electrode layer 6. The positive electrode 12 and the separator 3 are bonded to each other by a polymer 9 having adhesive properties scattered in the positive electrode layer 4 and the separator 3 and at the boundary between them. On the other hand, the negative electrode 13 and the separator 3 are bonded to each other by the polymer 9 having adhesive properties scattered in the negative electrode layer 6 and the separator 3 and at the boundary between them. The non-aqueous electrolyte is impregnated in the electrode group 2 in the exterior material 1. One end of the strip-like positive electrode lead 10 is connected to the positive electrode current collector 5 of the electrode group 2, and the other end is extended from the exterior material 1. On the other hand, one end of the strip-like negative electrode lead 11 is connected to the negative electrode current collector 7 of the electrode group 2 and the other end is extended from the exterior material 1.

  In FIG. 1 described above, the bonding portion 8 is formed on the entire surface of the electrode group 2, but the bonding portion 8 may be formed on a part of the electrode group 2. When forming the adhesion part 8 in a part of electrode group 2, it is preferable to form in the surface equivalent to the outermost periphery of an electrode group at least. Further, the bonding portion 8 may not be provided.

  The non-aqueous electrolyte secondary battery including the electrode group that satisfies the above-described condition (a) is manufactured by, for example, the method (I) described below. However, the manufacturing method of the non-aqueous electrolyte secondary battery according to the present invention is not limited to the following embodiment as long as it is within the scope of the present invention.

<Manufacturing method (I)>
(First step)
An electrode group is prepared by interposing a porous sheet as a separator between the positive electrode and the negative electrode.

  In the electrode group, the positive electrode and the negative electrode are spirally wound through a separator having no polymer between them, or wound in a spiral shape and then compressed in the radial direction, or the positive electrode It is desirable that the negative electrode is fabricated by bending a plurality of times through a separator having no polymer between them and having an adhesive property therebetween. When produced by such a method, in the second step to be described later, while the polymer solution having adhesiveness is infiltrated into the positive electrode, the negative electrode, and the separator, the solution is applied to the entire boundary between the positive electrode and the separator and between the negative electrode and the separator. Infiltration can be prevented. As a result, it is possible to intersperse the polymer having adhesiveness to the positive electrode, the negative electrode and the separator, and to interpose the polymer having adhesiveness to the boundary between the positive electrode and the separator and the boundary between the negative electrode and the separator. it can.

  The positive electrode is produced, for example, by suspending a conductive agent and a binder in an appropriate solvent in a positive electrode active material, applying the suspension to a current collector, and drying to form a thin plate. Examples of the positive electrode active material, the conductive agent, the binder, and the current collector include the same materials as those described in the section of (1) Positive electrode described above.

  The negative electrode is, for example, kneaded with a carbonaceous material that occludes / releases lithium ions and a binder in the presence of a solvent, and the resulting suspension is applied to a current collector and dried, followed by a desired pressure. It is produced by pressing once or multistage pressing 2-5 times.

  Examples of the carbonaceous material, the binder, and the current collector include the same materials as those described in the section of (2) Negative electrode.

  As the porous sheet of the separator, the same sheet as described in the section of (3) Separator described above can be used.

(Second step)
The electrode group is accommodated in a bag-shaped exterior material so that the laminated surface can be seen from the opening. A solution obtained by dissolving a polymer having adhesiveness in a solvent is injected into the electrode group in the exterior material from the opening, and the electrode group is impregnated with the solution.

  Examples of the exterior material include the same materials as those described in the section of (6) Exterior material described above.

  Examples of the adhesive polymer include the same polymers as described in the column of the adhesive polymer (5) described above. In particular, PVdF is preferable.

  As the solvent, it is desirable to use an organic solvent having a boiling point of 200 ° C. or lower. An example of such an organic solvent is dimethylformamide (boiling point 153 ° C.). If the boiling point of the organic solvent exceeds 200 ° C., the drying time may take a long time when the vacuum drying temperature described below is set to 100 ° C. or lower. The lower limit of the boiling point of the organic solvent is preferably 50 ° C. If the boiling point of the organic solvent is less than 50 ° C., the organic solvent may evaporate while the solution is injected into the electrode group. The upper limit of the boiling point is more preferably 180 ° C., and the lower limit of the boiling point is further preferably 100 ° C.

  The concentration of the polymer having adhesiveness in the solution is preferably in the range of 0.05 to 2.5% by weight. This is due to the following reason. If the concentration is less than 0.05% by weight, it may be difficult to bond the positive and negative electrodes and the separator with sufficient strength. On the other hand, if the concentration exceeds 2.5% by weight, it may be difficult to obtain a sufficient porosity to hold the non-aqueous electrolyte, and the interface impedance of the electrode may be significantly increased. As the interfacial impedance increases, the capacity and large current discharge characteristics are significantly reduced. A more preferable range of the concentration is 0.1 to 1.5% by weight.

  The amount of the solution injected is preferably in the range of 0.1 to 2 ml per 100 mAh of battery capacity when the concentration of the polymer having adhesiveness in the solution is 0.05 to 2.5% by weight. This is due to the following reason. If the injection amount is less than 0.1 ml, it may be difficult to sufficiently improve the adhesion between the positive electrode, the negative electrode, and the separator. On the other hand, if the injection amount exceeds 2 ml, the lithium ion conductivity of the secondary battery may be decreased and the internal resistance may be increased, which may improve the discharge capacity, large current discharge characteristics, and charge / discharge cycle characteristics. It can be difficult. A more preferable range of the injection amount is 0.15 to 1 ml per 100 mAh of battery capacity.

(Third step)
By subjecting the electrode group to vacuum drying, the solvent in the solution is evaporated, and an adhesive polymer is present in the gaps of the positive electrode, the negative electrode, and the separator. By this step, the positive electrode and the separator are adhered by a polymer having adhesiveness scattered in the inside and the boundary thereof, and the negative electrode and the separator have adhesiveness scattered in the interior and the boundary thereof. Bonded by polymer. Moreover, the moisture contained in the electrode group can be removed simultaneously by this vacuum drying.

  In addition, the said electrode group accept | permits containing a trace amount solvent.

  The vacuum drying is preferably performed at 100 ° C. or lower. This is due to the following reason. When the temperature of vacuum drying exceeds 100 ° C., the separator may be significantly heat-shrinked. When the thermal shrinkage increases, the separator warps, and it becomes difficult to firmly bond the positive electrode, the negative electrode, and the separator. In addition, the above-described heat shrinkage tends to occur remarkably when a porous film containing polyethylene or polypropylene is used as a separator. Although the thermal shrinkage of the separator can be suppressed as the vacuum drying temperature becomes lower, if the temperature of the vacuum drying is lower than 40 ° C., it may be difficult to sufficiently evaporate the solvent. For this reason, it is more preferable that the vacuum drying temperature is 40 to 100 ° C.

(4th process)
After injecting a non-aqueous electrolyte into the electrode group in the exterior material, a thin non-aqueous electrolyte secondary battery is assembled by sealing the opening of the exterior material.

  As said non-aqueous electrolyte, the thing similar to what was demonstrated in the column of (4) non-aqueous electrolyte mentioned above can be used.

  In the manufacturing method described above, the solution in which the adhesive polymer is dissolved is injected after the electrode group is stored in the exterior material. However, the injection may be performed without being stored in the exterior material. In this case, first, an electrode group is produced by interposing a separator between the positive electrode and the negative electrode. After the electrode group is impregnated with the solution, the electrode group is vacuum-dried to evaporate the solvent of the solution, and the adhesive polymer is present in the gaps of the positive electrode, the negative electrode, and the separator. A thin non-aqueous electrolyte secondary battery can be manufactured by injecting such a group of electrodes into an exterior material, then injecting a non-aqueous electrolyte and performing sealing or the like. You may apply | coat an adhesive agent to the electrode group outer periphery before the accommodation to an exterior material. Thereby, an electrode group can be adhere | attached on an exterior material. In this case, a metal can can be used as an exterior material instead of a film.

(5th process)
The secondary battery assembled as described above is initially charged at a charge rate of 0.05 C or more and 0.5 C or less under a temperature condition of 30 ° C. to 80 ° C. Charging under this condition may be performed only for one cycle or may be performed for two or more cycles. Moreover, you may store for about 1 hour-20 hours on 30 degreeC-80 degreeC temperature conditions before the first charge.

  Here, the 1C charging rate is a current value necessary for charging the nominal capacity (Ah) in one hour.

  The reason for defining the initial charging temperature within the above range is as follows. If the initial charging temperature is less than 30 ° C., the viscosity of the nonaqueous electrolyte solution remains high, so that it is difficult to uniformly impregnate the nonaqueous electrolyte solution in the positive electrode, negative electrode, and separator, and the internal impedance increases. Moreover, the utilization factor of an active material falls. On the other hand, when the initial charging temperature exceeds 80 ° C., the binder contained in the positive electrode and the negative electrode is deteriorated.

  By making the charge rate of the initial charge in the range of 0.05 to 0.5 C, the expansion of the positive electrode and the negative electrode due to the charge can be moderately slowed, so that the nonaqueous electrolyte uniformly penetrates the positive electrode and the negative electrode be able to.

  By providing such a process, the non-aqueous electrolyte can be uniformly impregnated in the gaps of the electrodes and the separator, so that the internal impedance of 1 kHz of the non-aqueous electrolyte secondary battery can be reduced. The product of the capacity and the internal impedance of 1 kHz can be in the range of 10 mΩ · Ah to 110 mΩ · Ah. As a result, since the utilization factor of the active material can be increased, the substantial capacity of the battery can be increased. Moreover, the charge / discharge cycle characteristics and the large current discharge characteristics of the battery can be improved.

  Next, a non-aqueous electrolyte secondary comprising an electrode group satisfying the above-mentioned (b) and a non-aqueous electrolyte containing a non-aqueous solvent containing γ-butyrolactone in an amount of more than 50% by volume and not more than 95% by volume. The battery will be described.

  In this secondary battery, the positive electrode, the negative electrode, and the separator are integrated by thermosetting the binder contained in the positive electrode and the negative electrode.

  As the separator, the same separator as described in the section of (3) Separator described above is used. Moreover, as an exterior material which accommodates the said electrode group, the thing similar to what was demonstrated in the column of (6) exterior material mentioned above is used.

  The positive electrode has a structure in which a positive electrode layer containing an active material, a binder, and a conductive agent is supported on one side or both sides of a current collector. As the active material, the binder, the conductive agent, and the current collector, the same materials as those described in the section of (1) Positive electrode described above are used.

  The negative electrode has a structure in which a negative electrode layer containing a carbonaceous material that occludes / releases lithium ions and a binder is supported on one side or both sides of a current collector. As the carbonaceous material, the binder, and the current collector, the same materials as those described in the section of (2) Negative electrode are used.

  The negative electrode layer is made of a metal such as aluminum, magnesium, tin, or silicon, a metal oxide, a metal sulfide, or a metal nitride, in addition to the carbon material that absorbs and releases lithium ions. It may contain a selected metal compound or lithium alloy. As the metal oxide, the metal sulfide, the metal nitride, and the lithium alloy, the same materials as those described in the section of (2) Negative electrode are used.

  This secondary battery is manufactured by, for example, the method (II) described below.

<Production method (II)>
(First step)
An electrode group is produced by the method described in the following (a) to (c).

  (A) The positive electrode and the negative electrode are wound spirally with a separator interposed therebetween.

  (B) The positive electrode and the negative electrode are wound spirally with a separator interposed therebetween, and then compressed in the radial direction.

  (C) The positive electrode and the negative electrode are bent twice or more with a separator interposed therebetween.

(Second step)
The electrode group is housed in a bag-shaped film exterior material.

(Third step)
The electrode group is molded while being heated to 40 to 120 ° C.

  The molding is compressed in the radial direction when the electrode group is produced by the method (a), and compressed in the laminating direction when the electrode group is produced by the method (b) or (c). To be done.

  The molding can be performed, for example, by press molding or insertion into a mold.

  The reason why the electrode group is heated when forming the electrode group will be described. The electrode group does not contain an adhesive polymer. For this reason, when this electrode group is molded at room temperature, springback occurs after molding, that is, gaps are formed between the positive electrode and the separator and between the negative electrode and the separator. As a result, the contact area between the positive electrode and the separator and the contact area between the negative electrode and the separator are reduced, so that the internal impedance is increased. By forming the electrode group at 40 ° C. or higher, the binder contained in the positive electrode and the negative electrode can be thermally cured, so that the hardness of the electrode group can be increased. As a result, since the spring back after molding can be suppressed, the contact area between the positive electrode and the separator and the contact area between the negative electrode and the separator can be improved, and the contact area can be maintained even after repeated charge / discharge cycles. Can do. On the other hand, when the temperature of the electrode group exceeds 120 ° C., the separator may be significantly heat-shrinked. A more preferable temperature is 60 to 100 ° C.

  The molding while heating to the specific temperature described above can be performed, for example, under normal pressure, under reduced pressure, or under vacuum. It is desirable to perform under reduced pressure or under vacuum because the water removal efficiency from the electrode group is improved.

When the molding is performed by press molding, the press pressure is preferably in the range of 0.01 to 20 kg / cm ² . This is due to the following reason. If the pressing pressure is lower than 0.01 kg / cm ^2, it may be difficult to suppress the spring back after molding. On the other hand, if the press pressure is higher than 20 kg / cm ² , the porosity in the electrode group may be reduced, and therefore the amount of nonaqueous electrolyte retained in the electrode group may be insufficient.

(4th process)
After injecting a nonaqueous electrolyte into the electrode group in the exterior material, the nonaqueous electrolyte secondary battery described above is assembled by sealing the opening of the exterior material.

  In the manufacturing method described above, the electrode group is housed in the exterior material and then molded while heating the electrode group to a specific temperature. However, the heat molding described above may be performed before housing in the exterior material. In this case, first, an electrode group is fabricated by the first process described above. The electrode group is molded while being heated to 40 to 120 ° C. Next, after the electrode group is housed in an exterior material, the nonaqueous electrolyte secondary battery described above can be assembled by injecting a nonaqueous electrolyte and performing sealing or the like. At this time, a metal can can be used as an exterior material instead of a film.

(5th process)
The secondary battery assembled as described above is initially charged at a charge rate of 0.05 C or more and 0.5 C or less under a temperature condition of 30 ° C. to 80 ° C. Charging under this condition may be performed only for one cycle or may be performed for two or more cycles. Moreover, you may store for about 1 hour-20 hours on 30 degreeC-80 degreeC temperature conditions before the first charge.

  The reason why the temperature of the initial charge and the charge rate of the initial charge are defined in the range is for the same reason as described above.

  By providing such a process, the non-aqueous electrolyte can be uniformly impregnated in the gaps of the electrodes and the separator, so that the internal impedance of 1 kHz of the non-aqueous electrolyte secondary battery can be reduced. The product of the capacity and the internal impedance of 1 kHz can be in the range of 10 mΩ · Ah to 110 mΩ · Ah. As a result, since the utilization factor of the active material can be increased, the substantial capacity of the battery can be increased. Moreover, the charge / discharge cycle characteristics and the large current discharge characteristics of the battery can be improved.

  The first nonaqueous electrolyte secondary battery according to the present invention has a structure in which a can made of aluminum or the like is used as an exterior material, and an electrode group consisting of a positive electrode, a negative electrode, and a separator is wound and inserted into the can. Also good. In that case, there is no need for an adhesive part or a polymer having adhesiveness.

  Next, the second nonaqueous electrolyte secondary battery according to the present invention will be described.

The secondary battery includes a positive electrode current collector and a positive electrode including a positive electrode active material layer supported on one or both surfaces of the positive electrode current collector, a negative electrode current collector, and one or both surfaces of the negative electrode current collector. An electrode group comprising a negative electrode including a negative electrode active material layer that is supported and includes a material that absorbs and releases lithium ions; and a separator disposed between the positive electrode and the negative electrode;
A nonaqueous electrolytic solution impregnated in the electrode group and comprising a nonaqueous solvent and a lithium salt dissolved in the nonaqueous solvent;
An exterior material in which the electrode group is housed.

  The porosity of the positive electrode active material layer is lower than the porosity of the negative electrode active material layer. The positive electrode active material layer has a thickness of 10 to 100 μm. Further, the non-aqueous solvent contains γ-butyrolactone in an amount of 40% by volume to 95% by volume based on the total amount of the non-aqueous solvent.

  In this secondary battery, the positive electrode, the negative electrode, and the separator do not have to be integrated, but it is preferable that they are integrated under the conditions described in (a) or (b) below. .

  (A) Adhesion in which the positive electrode and the separator are integrated by an adhesive polymer present at at least a part of these boundaries, and the negative electrode and the separator are present at at least a part of these boundaries It is integrated with a polymer having properties. In particular, the positive electrode and the separator are integrated with an adhesive polymer scattered in the interior and boundary thereof, and the negative electrode and the separator have adhesiveness scattered in the interior and boundary thereof. It is desirable that they are integrated by a polymer.

  (B) The positive electrode, the negative electrode, and the separator are integrated by thermosetting the binder contained in the positive electrode and the negative electrode.

  By adopting the configuration of (a) or (b), the swelling of the exterior material can be further reduced.

  The secondary battery preferably has a product of battery capacity (Ah) and 1 kHz battery internal impedance (mΩ) of 10 mΩ · Ah or more and 110 mΩ · Ah or less. By setting the product of the capacity and the impedance within the above range, the large current discharge characteristics and the charge / discharge cycle characteristics can be further improved. Here, the battery capacity is a nominal capacity or a discharge capacity when discharged at 0.2C. A more preferable range is 20 mΩ · Ah or more and 60 mΩ · Ah or less.

  The product of the battery capacity and the impedance can be 10 mΩ · Ah or more and 110 mΩ · Ah or less, for example, by the manufacturing method (I) described above or the manufacturing method (II) described above. However, in (I), the addition amount of the adhesive polymer, the distribution of the adhesive polymer, and the initial charging conditions are set so that the product of the battery capacity and the impedance is 10 mΩ · Ah or more and 110 mΩ · Ah or less. In (II), the temperature, press pressure, and initial charge condition when forming the electrode group are set so that the product of the battery capacity and impedance is 10 mΩ · Ah or more and 110 mΩ · Ah or less.

  Hereinafter, a non-aqueous electrolyte secondary battery including an electrode group that satisfies the above-described (a) will be described.

1) Positive Electrode This positive electrode has a structure in which a positive electrode active material layer including an active material, a conductive agent, an adhesive polymer, and a binder is supported on one side or both sides of a current collector.

  Examples of the active material, the conductive agent, the adhesive polymer, and the binder include the same materials as those described in the first non-aqueous electrolyte secondary battery.

The positive electrode active material layer has a thickness in the range of 10 to 100 μm. Here, the thickness of the positive electrode active material layer means the distance between the surface of the positive electrode active material facing the separator and the surface of the positive electrode active material in contact with the current collector. For example, as shown in FIG. 4, when the positive electrode active material layer P is supported on both surfaces of the current collector S, the positive electrode active material surface P ₁ facing the separator and the positive electrode active material surface P _{2 in} contact with the current collector Is the thickness T of the positive electrode active material layer. Therefore, when the positive electrode active material layer is supported on both surfaces of the positive electrode current collector, the thickness of one surface of the positive electrode active material layer is 10 to 100 μm and the total thickness of the positive electrode active material layer is 20 to 200 μm. Become. When the thickness of the positive electrode active material layer is less than 10 μm, the weight ratio of the current collector and the volume ratio are increased, so that the energy density is decreased. A preferable lower limit of the thickness is 30 μm, and a more preferable lower limit is 50 μm. On the other hand, when the thickness of the positive electrode active material layer exceeds 100 μm, the non-aqueous electrolyte concentrates on the positive electrode surface during the rapid charge / discharge cycle, and the electrode reaction inside the positive electrode hardly progresses, so that the cycle life is reduced. A preferable upper limit value of the thickness is 85 μm, and a more preferable upper limit value is 60 μm. In particular, the thickness of the positive electrode active material layer is preferably in the range of 10 to 60 μm. Within this range, the large current discharge characteristics and cycle life are greatly improved. A more preferable range is 30 to 50 μm.

  The thickness of the positive electrode active material layer is measured by the method described below. First, 10 points that are separated from each other by 1 cm or more are arbitrarily selected, the thickness of each point is measured, and the average value is calculated to measure the thickness of the positive electrode. However, when the positive electrode to be measured has a structure in which the positive electrode active material layer is supported on both sides of the current collector, the thickness of the positive electrode is measured after removing one of the positive electrode active material layers. Next, the positive electrode active material layer is removed from the current collector, and the thickness of the current collector is measured. The thickness of the current collector can be obtained by arbitrarily selecting 10 points that are separated from each other by 1 cm or more, measuring the thickness of each point, and calculating the average value. The difference between the thickness of the positive electrode and the thickness of the current collector is taken as the thickness of the positive electrode active material layer to be obtained.

  The porosity of the positive electrode active material layer is lower than the porosity of the negative electrode active material layer. The porosity of the positive electrode active material layer is preferably in the range of 25 to 40%. This is due to the following reason. If the porosity is less than 25%, it may be difficult to uniformly infiltrate the non-aqueous electrolyte even if the thickness of the positive electrode active material layer is regulated. On the other hand, if the porosity exceeds 40%, a high capacity, that is, a high energy density may not be obtained. A more preferable range of the porosity is 30 to 35%.

  As the current collector, a conductive substrate having a porous structure or a non-porous conductive substrate can be used. These conductive substrates can be formed from, for example, aluminum, stainless steel, or nickel. The thickness of the current collector is preferably in the range of 5 to 20 μm. This is because within this range, the balance between the positive electrode strength and the weight reduction can be achieved.

2) Negative electrode This negative electrode has a structure in which a negative electrode active material layer containing a carbonaceous material that occludes / releases lithium ions, an adhesive polymer, and a binder is supported on one side or both sides of a current collector.

  The carbonaceous material that absorbs and releases lithium ions, the conductive agent, the adhesive polymer, the binder, and the current collector are the same as those described in the first nonaqueous electrolyte secondary battery. Things can be mentioned.

  The thickness of the negative electrode active material layer is preferably in the range of 10 to 100 μm. Here, the thickness of the negative electrode active material layer means the distance between the surface of the negative electrode active material facing the separator and the surface of the negative electrode active material in contact with the current collector. When the negative electrode active material layer is supported on both sides of the negative electrode current collector, the thickness of one side of the negative electrode active material layer is 10 to 100 μm, and the total thickness of the negative electrode active material layer is in the range of 20 to 200 μm. It is desirable to make it. If the thickness of the negative electrode active material layer is less than 10 μm, the weight ratio of the current collector and the volume ratio are increased, which may make it difficult to sufficiently improve the energy density. A preferable lower limit of the thickness is 30 μm, and a more preferable lower limit is 50 μm. On the other hand, when the thickness of the negative electrode active material layer exceeds 100 μm, the non-aqueous electrolyte tends to concentrate on the surface of the negative electrode, which may make it difficult to sufficiently improve the cycle life. A preferable upper limit value of the thickness is 85 μm, and a more preferable upper limit value is 60 μm. In particular, the thickness of the negative electrode active material layer is preferably in the range of 10 to 60 μm. Within this range, the large current discharge characteristics and cycle life are greatly improved. A more preferable range is 30 to 50 μm.

  The thickness of the negative electrode active material layer is measured by the method described below. First, 10 points that are separated from each other by 1 cm or more are arbitrarily selected, the thickness of each point is measured, and the average value is calculated to measure the thickness of the negative electrode. However, when the negative electrode to be measured has a structure in which the negative electrode active material layer is supported on both sides of the current collector, the thickness of the negative electrode is measured after removing one of the negative electrode active material layers. Next, the negative electrode active material layer is removed from the current collector, and the thickness of the current collector is measured. The thickness of the current collector can be obtained by arbitrarily selecting 10 points that are separated from each other by 1 cm or more, measuring the thickness of each point, and calculating the average value. The difference between the thickness of the negative electrode and the thickness of the current collector is taken as the thickness of the desired negative electrode active material layer.

  The porosity of the negative electrode active material layer is preferably in the range of 35 to 50%. This is due to the following reason. If the porosity is less than 35%, the distribution of the non-aqueous electrolyte may become non-uniform, so that lithium dendride may be deposited. On the other hand, if the porosity exceeds 50%, a high capacity, that is, a high energy density may not be obtained. A more preferable range of the porosity is 35 to 45%.

The blending ratio of the carbonaceous material and the binder is preferably in the range of 90 to 98% by weight of the carbonaceous material and 2 to 20% by weight of the binder. In particular, the carbonaceous material is preferably in the range of 10 to 70 g / cm ^{2 on} one side in a state where a negative electrode is produced.

The density of the negative electrode active material layer is preferably in the range of 1.20 to 1.50 g / cm ³ .

  As the current collector, a conductive substrate having a porous structure or a non-porous conductive substrate can be used. These conductive substrates can be formed from, for example, copper, stainless steel, or nickel. The thickness of the current collector is preferably in the range of 5 to 20 μm. This is because the negative electrode strength and weight reduction can be balanced within this range.

  The negative electrode active material layer may be a metal such as aluminum, magnesium, tin, or silicon, a metal oxide, a metal sulfide, or a metal nitridation instead of the above-described carbon material that absorbs and releases lithium ions. It may contain a metal compound selected from those or a lithium alloy.

  Examples of the metal oxide, the metal sulfide, the metal nitride, and the lithium alloy include the same as those described in the first nonaqueous electrolyte secondary battery.

3) Separator This separator is formed from a porous sheet.

  Examples of the porous sheet include the same ones as described in the first non-aqueous electrolyte secondary battery.

4) Nonaqueous electrolyte The nonaqueous electrolyte is obtained by dissolving a lithium salt in a mixed nonaqueous solvent containing γ-butyrolactone (BL), and the composition ratio of BL is 40% by volume or more of the total mixed nonaqueous solvent, It is 95 volume% or less. In the mixed non-aqueous solvent, it is preferable that the BL composition ratio is maximized. When the ratio is less than 40% by volume, gas is likely to be generated at a high temperature even if the thickness of the positive electrode active material layer is regulated. In addition, when the mixed non-aqueous solvent contains BL and cyclic carbonate, the ratio of cyclic carbonate becomes relatively high, so that the solvent viscosity is remarkably increased. As a result, the conductivity and permeability of the non-aqueous electrolyte solution are greatly reduced. Therefore, even if the thickness of the positive electrode active material layer is regulated, the charge / discharge cycle characteristics, the large current discharge characteristics, and the low temperature environment around −20 ° C. The discharge characteristics at are deteriorated. On the other hand, if the ratio exceeds 95% by volume, the reaction between the negative electrode and BL occurs, and the charge / discharge cycle characteristics deteriorate. That is, when the negative electrode (for example, containing a carbonaceous material that occludes and releases lithium ions) reacts with BL to cause reductive decomposition of the non-aqueous electrolyte, a coating that inhibits the charge / discharge reaction is formed on the surface of the negative electrode. The As a result, current concentration is likely to occur in the negative electrode, so that lithium metal is deposited on the negative electrode surface, or the impedance at the negative electrode interface is increased, the charge / discharge efficiency of the negative electrode is lowered, and charge / discharge cycle characteristics are degraded. A more preferable range is 60% by volume or more and 90% by volume or less. By setting it within this range, it is possible to further increase the effect of suppressing gas generation during high-temperature storage, and to further improve the discharge capacity in a low temperature environment around −20 ° C. A more preferable range is 75% by volume or more and 90% by volume or less.

  As a solvent mixed with BL, a cyclic carbonate is desirable in terms of increasing the charge / discharge efficiency of the negative electrode.

  As the cyclic carbonate, propylene carbonate (PC), ethylene carbonate (EC), vinylene carbonate (VC), trifluoropropylene carbonate (TFPC) and the like are desirable. In particular, when EC is used as a solvent mixed with BL, charge / discharge cycle characteristics and large current discharge characteristics can be significantly improved. Moreover, as another solvent mixed with BL, a third solvent consisting of at least one selected from the group consisting of PC, VC, TFPC, diethyl carbonate (DEC), methyl ethyl carbonate (MEC), and an aromatic compound, and EC The mixed solvent is desirable in terms of enhancing the charge / discharge cycle characteristics.

  Further, from the viewpoint of lowering the solvent viscosity, a low-viscosity solvent may be contained in an amount of 20% by volume or less. Examples of the low viscosity solvent include chain carbonates, chain ethers, cyclic ethers and the like.

  More preferred compositions of the non-aqueous solvent according to the present invention include BL and EC, BL and PC, BL and EC and DEC, BL and EC and MEC, BL and EC and MEC and VC, BL and EC and VC, and BL and PC. And VC, or BL, EC, PC, and VC. At this time, the volume ratio of EC is preferably 5 to 40% by volume. This is due to the following reason. If the EC ratio is less than 5% by volume, it may be difficult to cover the negative electrode surface densely with a protective film, so that the reaction between the negative electrode and BL occurs, and the charge / discharge cycle characteristics can be sufficiently improved. It can be difficult. On the other hand, if the EC ratio exceeds 40% by volume, the viscosity of the non-aqueous electrolyte solution is increased and the ionic conductivity may be lowered. Therefore, sufficient charge / discharge cycle characteristics, large current discharge characteristics, and low temperature discharge characteristics are sufficiently obtained. It can be difficult to improve. A more preferable range of the EC ratio is 10 to 35% by volume. Moreover, the solvent which consists of at least 1 sort (s) chosen from DEC, MEC, PC, and VC forms the dense protective film on the surface of a negative electrode, and makes the effect | action which reduces the interface impedance of a negative electrode. The amount of the solvent added is not particularly limited, and is set to such an amount that this action occurs. However, when the ratio of at least one solvent selected from DEC, MEC, PC and VC in the non-aqueous solvent exceeds 10% by volume, the non-aqueous electrolyte is sufficiently suppressed from being oxidatively decomposed in a high temperature environment. May be difficult, or the viscosity of the non-aqueous electrolyte solution may increase and the ionic conductivity may decrease. For this reason, it is desirable that the volume ratio of at least one solvent selected from DEC, MEC, PC and VC in the non-aqueous solvent is 10% by volume or less. A more preferable volume ratio is 2% by volume or less. The lower limit of the volume ratio is preferably 0.001% by volume, and a more preferable lower limit is 0.05% by volume.

  In particular, a non-aqueous solvent containing 40 to 95% by volume of BL, EC and VC is preferable. A non-aqueous electrolyte secondary battery comprising a non-aqueous electrolyte containing a non-aqueous solvent and a negative electrode containing a carbonaceous material that occludes and releases lithium ions can greatly reduce the impedance at the interface of the negative electrode. Since it is possible to suppress the deposition of metallic lithium on the negative electrode, the charge / discharge efficiency of the negative electrode can be improved. As a result, it is possible to suppress deformation of the exterior material by suppressing gas generation during high-temperature storage while realizing excellent large current discharge characteristics and a long life. It is estimated that the negative electrode characteristics are improved in this way due to the action described below. In the secondary battery, in addition to forming a protective film by EC on the surface of the negative electrode, a thin and dense film by VC is formed. As a result, since the reaction between BL and the negative electrode is further suppressed, it is considered that the reduction in impedance and the prevention of precipitation of metallic lithium are achieved.

  Moreover, as a nonaqueous solvent, you may use what contains 40-95 volume% BL, EC, and an aromatic compound instead of what has the composition mentioned above. Examples of the aromatic compound include at least one selected from benzene, toluene, xylene, biphenyl, and terphenyl. EC adheres to the surface of a negative electrode (for example, containing a carbonaceous material that occludes and releases lithium ions) to form a protective film, and can suppress the reaction between the negative electrode and BL. At this time, the volume ratio of EC is preferably 5 to 40% by volume for the same reason as described above. Further, a more preferable range of the EC ratio is 10 to 35% by volume. On the other hand, since the benzene ring of the aromatic compound is easily adsorbed on the surface of the negative electrode (for example, containing a carbonaceous material that occludes and releases lithium ions), the reaction between the negative electrode and BL can be suppressed. Therefore, since the non-aqueous electrolyte containing a non-aqueous solvent containing 40 to 95% by volume of BL, EC, and an aromatic compound can sufficiently suppress the reaction between the negative electrode and BL, charging and discharging of the secondary battery Cycle characteristics can be improved. Such a non-aqueous solvent preferably further contains at least one solvent selected from DEC, MEC, PC, TFPC and VC. By adding at least one solvent selected from DEC, MEC, PC, TFPC and VC, the reaction between the negative electrode and BL can be further suppressed, so that the charge / discharge cycle characteristics can be further improved. . Of these, VC is preferable. The addition amount of the third solvent consisting of at least one selected from the aromatic compound, DEC, MEC, PC, TFPC and VC is not particularly limited, and is set to such an amount that this action occurs. However, if the ratio of the third solvent in the non-aqueous solvent exceeds 10% by volume, it may be difficult to sufficiently prevent the non-aqueous electrolyte from undergoing oxidative decomposition in a high temperature environment, or the non-aqueous electrolyte. There is a possibility that the ionic conductivity may be lowered due to an increase in the viscosity of. For this reason, the volume ratio of the third solvent in the non-aqueous solvent is desirably 10% by volume or less. A more preferable volume ratio is 2% by volume or less. The lower limit of the volume ratio is preferably 0.001% by volume, and a more preferable lower limit is 0.05% by volume.

Examples of the electrolyte contained in the non-aqueous electrolyte include the same ones as described in the first non-aqueous electrolyte secondary battery. Among them, it is preferable to use LiPF ₆ or LiBF ₄ .

  The amount of the electrolyte dissolved in the non-aqueous solvent is preferably 0.5 to 2.0 mol / l.

  In order to improve the paintability with the separator, a surfactant such as trioctyl phosphate may be added to the non-aqueous electrolyte in the range of 0.1 to 1%.

  The amount of the non-aqueous electrolyte is preferably 0.2 to 0.6 g per 100 mAh battery unit capacity for the same reason as described in the first non-aqueous electrolyte secondary battery. A more preferable range of the amount of the non-aqueous electrolyte is 0.4 to 0.55 g / 100 mAh.

5) Polymer having adhesiveness It is desirable that the polymer having adhesiveness can maintain high adhesiveness in a state where a non-aqueous electrolyte is held. Furthermore, it is more preferable that such a polymer has high lithium ion conductivity. Specifically, the same thing as having demonstrated with the 1st non-aqueous-electrolyte secondary battery mentioned above can be mentioned. In particular, polyvinylidene fluoride is preferable.

  The polymer having adhesiveness preferably has a porous structure having fine pores in the gaps of the positive electrode, the negative electrode, and the separator. The adhesive polymer having a porous structure can hold a non-aqueous electrolyte.

  The total amount of the polymer having adhesiveness contained in the battery is 0.1 to 6 mg per 100 mAh of battery capacity for the same reason as described in the first non-aqueous electrolyte secondary battery. preferable. A more preferable range of the total amount of the polymer having adhesiveness is 0.2 to 1 mg per 100 mAh of battery capacity.

6) Exterior material As this exterior material, a first exterior material made of a sheet including a resin layer and having a thickness of 0.5 mm or less or a second exterior material having a thickness of 0.3 mm or less is used. The first exterior material and the second exterior material are as described in the first non-aqueous electrolyte secondary battery.

  When the film exterior material is used, it is desirable that the electrode group is adhered to the inner surface of the exterior material by an adhesive layer formed on at least a part of the surface thereof. With such a configuration, since the exterior material can be fixed to the surface of the electrode group, it is possible to prevent the electrolyte from penetrating between the electrode group and the exterior material.

  A thin lithium ion secondary battery which is an example of this non-aqueous electrolyte secondary battery will be described in detail with reference to FIGS.

  FIG. 5 is a cross-sectional view showing a thin lithium ion secondary battery which is an example of a second non-aqueous electrolyte secondary battery according to the present invention, FIG. 6 is an enlarged cross-sectional view showing part B of FIG. 5, and FIG. FIG. 6 is a schematic diagram showing the vicinity of a boundary between a positive electrode layer, a separator, and a negative electrode layer in the secondary battery of FIG. 5.

  As shown in FIG. 5, an exterior material 21 made of, for example, a film surrounds the electrode group 22. The electrode group 22 has a structure in which a laminate composed of a positive electrode, a separator, and a negative electrode is wound into a flat shape. As shown in FIG. 6, the laminate includes a separator 23, a positive electrode layer 24, a positive electrode current collector 25, and a positive electrode 32 including a positive electrode layer 24, a separator 23, a negative electrode layer 26, and a negative electrode collector. A negative electrode 33 including a current collector 27 and a negative electrode layer 26, a separator 23, a positive electrode layer 24, a positive electrode current collector 25, a positive electrode 32 including a positive electrode layer 24, a separator 23, a negative electrode layer 26, and a negative electrode current collector 27 are provided. The negative electrode 33 is formed by laminating in this order. In the electrode group 22, the negative electrode current collector 27 is located in the outermost layer. An adhesive portion 28 exists on the surface of the electrode group 22. The inner surface of the exterior material 21 is bonded to the bonding portion 28. As shown in FIG. 7, a polymer 29 having adhesiveness is held in the gaps of the positive electrode layer 24, the separator 23, and the negative electrode layer 26. The positive electrode 32 and the separator 23 are bonded to each other by a polymer 29 having adhesiveness scattered in the positive electrode layer 24 and the separator 23 and at the boundary between them. On the other hand, the negative electrode 33 and the separator 23 are bonded to each other by a polymer 29 having adhesive properties scattered in the negative electrode layer 26 and the separator 23 and at the boundary between them. The non-aqueous electrolyte is impregnated in the electrode group 22 in the exterior material 21. One end of the strip-like positive electrode lead 30 is connected to the positive electrode current collector 25 of the electrode group 22, and the other end is extended from the exterior member 21. On the other hand, one end of the strip-shaped negative electrode lead 31 is connected to the negative electrode current collector 27 of the electrode group 22, and the other end is extended from the exterior material 21.

  In FIG. 5 described above, the bonding portion 28 is formed on the entire surface of the electrode group 22, but the bonding portion 28 may be formed on a part of the electrode group 2. When forming the adhesion part 28 in a part of electrode group 22, it is preferable to form in the surface equivalent to the outermost periphery of an electrode group at least. Further, the adhesive portion 28 may not be provided.

  The non-aqueous electrolyte secondary battery including the electrode group that satisfies the above-described condition (a) is, for example, the manufacturing method (I) described in the first non-aqueous electrolyte secondary battery, that is, the positive electrode. And a step of producing an electrode group by interposing a porous sheet as a separator between the negative electrode, a step of impregnating the electrode group with a solution obtained by dissolving an adhesive polymer in a solvent, A step of vacuum drying the electrode group, a step of assembling a thin non-aqueous electrolyte secondary battery by impregnating the electrode group with a non-aqueous electrolyte and then sealing the electrode group in the exterior material; The secondary battery is manufactured at a temperature of 30 ° C. to 80 ° C. at a charge rate of 0.05 C or more and 0.5 C or less. However, the manufacturing method of the non-aqueous electrolyte secondary battery according to the present invention is not limited to the above embodiment as long as it is within the scope of the present invention.

  Next, a non-aqueous electrolyte secondary battery including an electrode group satisfying the above-described (b) and a non-aqueous electrolyte containing a non-aqueous solvent containing 40 to 95% by volume of γ-butyrolactone will be described.

  In this secondary battery, the positive electrode, the negative electrode, and the separator are integrated by thermosetting the binder contained in the positive electrode and the negative electrode.

  As the separator, the same separator as described in the section of (3) Separator in the above-described second nonaqueous electrolyte secondary battery is used. Moreover, as the exterior material for housing the electrode group, the same material as that described in the section of (6) exterior material in the above-described second nonaqueous electrolyte secondary battery is used.

  The positive electrode has a structure in which a positive electrode active material layer containing an active material, a binder, and a conductive agent is supported on one side or both sides of a current collector. As the active material, the binder, the conductive agent, and the current collector, the same materials as those described in the column of (1) positive electrode in the above-described second nonaqueous electrolyte secondary battery are used.

  The thickness of the positive electrode active material layer is set in the range of 10 to 100 μm for the same reason as described above. In addition, when the positive electrode active material layer is carry | supported on both surfaces of a positive electrode electrical power collector, the total thickness of a positive electrode active material layer becomes the range of 20-200 micrometers. The lower limit value of the positive electrode active material layer is preferably 30 μm, and more preferably 50 μm. On the other hand, the upper limit of the positive electrode active material layer is preferably 85 μm, and more preferably 60 μm. The thickness of the positive electrode active material layer is preferably in the range of 10 to 60 μm for the same reason as described in the second non-aqueous electrolyte secondary battery described above. A more preferable range is 30 to 50 μm.

  The porosity of the positive electrode active material layer is lower than the porosity of the negative electrode active material layer. The porosity of the positive electrode active material layer is preferably in the range of 25 to 40% for the same reason as described above. A more preferable range of the porosity is 30 to 35%.

  The negative electrode has a structure in which a negative electrode active material layer containing a carbonaceous material that occludes / releases lithium ions and a binder is supported on one side or both sides of a current collector. As the carbonaceous material, the binder, and the current collector, the same materials as those described in the column of (2) negative electrode in the above-described second nonaqueous electrolyte secondary battery are used.

  The thickness of the negative electrode active material layer is preferably in the range of 10 to 100 μm for the same reason as described above. In addition, when the negative electrode active material layer is carry | supported on both surfaces of a negative electrode collector, it is desirable to make the total thickness of a negative electrode active material layer into the range of 20-200 micrometers. The lower limit value of the negative electrode active material layer is preferably 30 μm, and more preferably 50 μm. On the other hand, the upper limit value of the negative electrode active material layer is preferably 85 μm, and more preferably 60 μm. The thickness of the negative electrode active material layer is preferably in the range of 10 to 60 μm for the same reason as described in the second non-aqueous electrolyte secondary battery described above. A more preferable range is 30 to 50 μm.

  The porosity of the negative electrode active material layer is preferably in the range of 35 to 50% for the same reason as described above. A more preferable range of the porosity is 35 to 45%.

The blending ratio of the carbonaceous material and the binder is preferably in the range of 90 to 98% by weight of the carbonaceous material and 2 to 20% by weight of the binder. In particular, the carbonaceous material is preferably in the range of 10 to 70 g / cm ^{2 on} one side in a state where a negative electrode is produced.

The density of the negative electrode active material layer is preferably in the range of 1.20 to 1.50 g / cm ³ .

  This secondary battery is, for example, the manufacturing method (II) described in the first nonaqueous electrolyte secondary battery described above, that is, a step of creating an electrode group with a separator interposed between the positive electrode and the negative electrode, A step of forming the electrode group while heating to 40 to 120 ° C., and impregnating the electrode group with a nonaqueous electrolyte solution, and then sealing the electrode group with an exterior material, thereby forming a nonaqueous electrolyte secondary battery It is manufactured by a method comprising an assembling step and a step of subjecting the secondary battery to initial charging at a charging rate of 0.05 C or more and 0.5 C or less under a temperature condition of 30 ° C. to 80 ° C.

  The second nonaqueous electrolyte secondary battery according to the present invention has a structure in which a can made of aluminum or the like is used as an exterior material, and an electrode group consisting of a positive electrode, a negative electrode, and a separator is wound and inserted into the can. Also good. In that case, there is no need for an adhesive part or a polymer having adhesiveness.

  As described above in detail, the nonaqueous electrolyte secondary battery according to the present invention includes a positive electrode, a negative electrode containing a material that absorbs and releases lithium ions, and a separator disposed between the positive electrode and the negative electrode. An electrode group; a nonaqueous electrolyte solution containing a nonaqueous solvent impregnated in the electrode group and a lithium salt dissolved in the nonaqueous solvent; a packaging material having a thickness of 0.3 mm or less in which the electrode group is accommodated Comprising. The non-aqueous solvent contains γ-butyrolactone in an amount of more than 50% by volume and not more than 95% by volume of the whole non-aqueous solvent.

  In the nonaqueous electrolyte secondary battery, it is desired to reduce the thickness to about 3 to 4 mm. It is not preferable to reduce the thickness of the electrode group in order to reduce the thickness because the battery capacity decreases. In order to reduce the thickness without sacrificing the battery capacity, it is necessary to reduce the thickness of the exterior material. However, when the thickness of the exterior material is 0.3 mm or less, the exterior material is deformed by the gas generated during high-temperature storage. For this reason, it is difficult to use an exterior material having a thickness of 0.3 mm or less, and the battery capacity is sacrificed to make the battery thinner.

  Since γ-butyrolactone is excellent in chemical stability, the positive electrode active material reacts with the nonaqueous electrolyte when stored under high temperature conditions by containing a specific amount of γ-butyrolactone in the nonaqueous solvent. Thus, the oxidative decomposition of the nonaqueous electrolytic solution can be suppressed. As a result, since the amount of gas generated can be reduced, it is possible to suppress the expansion of a thin exterior material having a thickness of 0.3 mm or less. Accordingly, it is possible to reduce the thickness while maintaining practical large current discharge characteristics and charge / discharge cycle characteristics and almost without sacrificing battery capacity. A thin non-aqueous electrolyte secondary battery having high weight energy density and high volume energy density can be realized.

  When the secondary battery is initially charged, the non-aqueous electrolyte is prepared by reacting the negative electrode with γ-butyrolactone by setting the charging temperature to 30 to 80 ° C. and the charging rate to 0.05 to 0.5 C. Can be suppressed from reductive decomposition, so that the interfacial impedance of the negative electrode can be lowered and precipitation of metallic lithium can be suppressed. Therefore, the large current discharge characteristics and charge / discharge cycle characteristics of the secondary battery can be improved.

  In the secondary battery according to the present invention, the ionic conductivity of the non-aqueous electrolyte can be improved by setting the concentration of the lithium salt in the non-aqueous electrolyte to 0.5 mol / l or more. In addition, the cycle life can be further improved.

  In the secondary battery according to the present invention, when a negative electrode containing a carbonaceous material that occludes and releases lithium ions is used, the nonaqueous solvent further contains ethylene carbonate, thereby forming a protective film on the surface of the negative electrode. Therefore, the reaction between the negative electrode and γ-butyrolactone can be further suppressed, and the large current discharge characteristics and cycle life can be further improved. The non-aqueous solvent further contains a third solvent composed of at least one selected from vinylene carbonate, propylene carbonate, diethyl carbonate, methyl ethyl carbonate, trifluoropropylene, and an aromatic compound, whereby the surface of the negative electrode is covered with a protective film. Since it can cover densely, reaction of a negative electrode and (gamma) -butyrolactone can be reduced significantly, and a large current discharge characteristic and cycle life can be improved further.

  In the secondary battery according to the present invention, the product of the battery capacity (Ah) and the battery internal impedance (mΩ) of 1 kHz is made 10 mΩ · Ah or more and 110 mΩ · Ah or less to further improve the large current discharge characteristics and cycle life. Can be made.

In the secondary battery according to the present invention, the separator includes a porous sheet having an air permeability of 600 seconds / 100 cm ³ or less, so that the non-aqueous electrolyte containing a specific amount of the above-described γ-butyrolactone is uniformly formed in the separator. Can be impregnated. As a result, since the ion conductivity of the separator can be improved, the large current discharge characteristics and the cycle life can be further improved.

  By the way, the outer packaging material having a thickness of 0.3 mm or less included in the secondary battery according to the present invention easily deforms following the expansion / contraction of the electrode group accompanying the charge / discharge reaction, and has a force to sandwich the electrode group. weak. For this reason, when a charging / discharging cycle progresses, there exists a possibility that the contact area of a positive electrode and a separator and the contact area of a negative electrode and a separator may reduce. The positive electrode and the separator are integrated with an adhesive polymer present at at least a part of these boundaries, and the negative electrode and the separator are integrated at least a part of these boundaries with an adhesive polymer. By integrating, the positive electrode and the separator and the negative electrode and the separator can be adhered even if the charge / discharge cycle proceeds. As a result, an increase in internal impedance can be suppressed, so that the cycle life can be further improved. At the same time, gas generation at high temperatures can be further reduced.

  In the secondary battery according to the present invention, the positive electrode and the separator are integrated with an adhesive polymer scattered in the inside and the boundary, and the negative electrode and the separator are scattered in the inside and the boundary. By integrating with a polymer having adhesive properties, the adhesive strength between the positive electrode and the separator and the adhesive strength between the negative electrode and the separator can be improved while keeping the internal resistance low. As a result, an increase in internal impedance can be suppressed, so that the cycle life can be further improved. At the same time, gas generation at high temperatures can be further reduced.

  In the secondary battery according to the present invention, the positive electrode, the negative electrode, and the separator are integrated by thermally curing the binder contained in the positive electrode and the negative electrode, thereby keeping the internal resistance low. The contact area between the separator and the contact area between the negative electrode and the separator can be improved, and the contact area can be maintained even after repeated charge / discharge cycles. As a result, an increase in internal impedance can be suppressed, so that the cycle life can be further improved. At the same time, gas generation at high temperatures can be further reduced.

  Moreover, the manufacturing method of the non-aqueous-electrolyte secondary battery concerning this invention is an electrode group provided with a positive electrode, the negative electrode containing the material which occludes / releases lithium ion, and the separator arrange | positioned between a positive electrode and a negative electrode; A non-aqueous electrolyte secondary battery manufacturing method comprising: a non-aqueous electrolyte solution impregnated in the electrode group and including a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent. The solvent contains γ-butyrolactone in an amount of 55% to 95% by volume of the entire non-aqueous solvent, and the initial charge is performed at a temperature of 30 ° C. to 80 ° C. at a charge rate of 0.05C to 0.5C. The process to perform is comprised.

  According to the method for producing a non-aqueous electrolyte secondary battery of the present invention, since the non-aqueous electrolyte can be well permeated into the electrode or the separator, the impedance of the secondary battery can be reduced, and the active material Utilization rate can be increased, and substantial battery capacity can be improved.

  The non-aqueous electrolyte secondary battery according to the present invention includes an electrode group including a positive electrode, a negative electrode including a material that absorbs and releases lithium ions, and a separator disposed between the positive electrode and the negative electrode; A non-aqueous electrolyte comprising a non-aqueous solvent impregnated in an electrode group and a lithium salt dissolved in the non-aqueous solvent; from a sheet having a thickness of 0.5 mm or less containing the electrode group and including a resin layer The exterior material which comprises. The non-aqueous solvent contains γ-butyrolactone in an amount of more than 50% by volume and not more than 95% by volume of the whole non-aqueous solvent.

  According to such a secondary battery, since the amount of gas generation can be reduced, it is possible to prevent the exterior material made of a sheet having a thickness of 0.5 mm or less including the resin layer from expanding. As a result, it is possible to use a lightweight exterior material, and furthermore, it is possible to maintain practical large current discharge characteristics and charge / discharge cycle characteristics, so that it has excellent large current discharge characteristics, long life, and weight energy density. A non-aqueous electrolyte secondary battery having a high value can be realized.

  The non-aqueous electrolyte secondary battery according to the present invention includes a positive electrode current collector, a positive electrode including a positive electrode active material layer supported on one or both surfaces of the positive electrode current collector, a negative electrode current collector, and the negative electrode current collector. An electrode group comprising a negative electrode including a negative electrode active material layer that is supported on one or both surfaces of an electric body and includes a material that absorbs and releases lithium ions; and a separator disposed between the positive electrode and the negative electrode; And a non-aqueous electrolyte solution containing a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent; and a packaging material having a thickness of 0.3 mm or less in which the electrode group is accommodated. The porosity of the positive electrode active material layer is lower than the porosity of the negative electrode active material layer. The positive electrode active material layer has a thickness of 10 to 100 μm. Further, the non-aqueous solvent contains γ-butyrolactone in an amount of 40% by volume to 95% by volume based on the total amount of the non-aqueous solvent.

  In a non-aqueous electrolyte secondary battery, if the distribution of the non-aqueous electrolyte in the negative electrode is uneven, current concentration occurs in the negative electrode, and lithium dendride tends to precipitate. In order to avoid this, the porosity of the negative electrode is increased and the permeability of the non-aqueous electrolyte is improved. On the other hand, not only such a problem does not occur in the positive electrode, but if the porosity is the same as that of the negative electrode, the positive electrode active material layer density decreases and a high capacity cannot be obtained. For this reason, the porosity of the positive electrode active material is made lower than that of the negative electrode active material layer.

  By the way, the non-aqueous electrolyte containing γ-butyrolactone tends to hardly penetrate into electrodes such as a positive electrode and a negative electrode. If the above-mentioned positive electrode having a low porosity is impregnated with this non-aqueous electrolyte, only the surface can be impregnated, and the cycle life is significantly reduced.

  As in the present invention, by setting the thickness of the positive electrode active material layer having a low porosity to 10 to 100 μm, the electrolyte permeability of the positive electrode active material layer can be improved. As a result, the non-aqueous electrolyte containing γ-butyrolactone can be uniformly permeated into both the positive electrode active material layer and the negative electrode active material layer, so that the excellent oxidation resistance characteristic of γ-butyrolactone is fully utilized. The non-aqueous electrolyte containing a non-aqueous solvent containing 40% by volume or more and 95% by volume or less of γ-butyrolactone can suppress the generation of gas when stored under high temperature conditions, and has a thickness. Can be prevented from swelling as thin as 0.3 mm or less. Therefore, it is possible to reduce the thickness without sacrificing the battery capacity while maintaining practical large current discharge characteristics and charge / discharge cycle characteristics. Therefore, it has excellent high current discharge characteristics, long life, and weight. A thin non-aqueous electrolyte secondary battery with high energy density and volume energy density can be realized.

  When the secondary battery is initially charged, the non-aqueous electrolyte is prepared by reacting the negative electrode with γ-butyrolactone by setting the charging temperature to 30 to 80 ° C. and the charging rate to 0.05 to 0.5 C. Can be suppressed from reductive decomposition, so that the interfacial impedance of the negative electrode can be lowered and precipitation of metallic lithium can be suppressed. Therefore, the large current discharge characteristics and charge / discharge cycle characteristics of the secondary battery can be improved.

  In the secondary battery according to the present invention, the electrolyte solution permeability of the negative electrode active material layer can be improved by setting the thickness of the negative electrode active material layer to 10 to 100 μm. Furthermore, it can reduce, and can improve a large current discharge characteristic and charging / discharging cycling characteristics more.

  In the secondary battery according to the present invention, the ionic conductivity of the non-aqueous electrolyte can be improved by setting the concentration of the lithium salt in the non-aqueous electrolyte to 0.5 mol / l or more. In addition, the cycle life can be further improved.

  In the secondary battery according to the present invention, when a negative electrode containing a carbonaceous material that occludes and releases lithium ions is used, the nonaqueous solvent further contains ethylene carbonate, thereby forming a protective film on the surface of the negative electrode. Therefore, the reaction between the negative electrode and γ-butyrolactone can be further suppressed, and the large current discharge characteristics and cycle life can be further improved. The non-aqueous solvent further contains a third solvent composed of at least one selected from vinylene carbonate, propylene carbonate, diethyl carbonate, methyl ethyl carbonate, trifluoropropylene, and an aromatic compound, whereby the surface of the negative electrode is covered with a protective film. Since it can cover densely, reaction of a negative electrode and (gamma) -butyrolactone can be reduced significantly, and a large current discharge characteristic and cycle life can be improved further.

In the secondary battery according to the present invention, the separator includes a porous sheet having an air permeability of 600 seconds / 100 cm ³ or less, so that the non-aqueous electrolyte containing a specific amount of the above-described γ-butyrolactone is uniformly formed in the separator. Can be impregnated. As a result, since the ion conductivity of the separator can be improved, the large current discharge characteristics and the cycle life can be further improved.

  In the secondary battery according to the present invention, the positive electrode and the separator are integrated with an adhesive polymer present at at least part of these boundaries, and the negative electrode and the separator are integrated at least part of these boundaries. By integrating with a polymer having adhesiveness existing in, an increase in internal impedance accompanying the progress of the charge / discharge cycle can be suppressed, so that the cycle life can be further improved. At the same time, gas generation at high temperatures can be further reduced.

  In the secondary battery according to the present invention, the positive electrode and the separator are integrated with an adhesive polymer scattered in the inside and the boundary, and the negative electrode and the separator are scattered in the inside and the boundary. By integrating with a polymer having adhesive properties, the internal impedance at the beginning of the charge / discharge cycle can be lowered, and the value can be maintained even if the charge / discharge cycle progresses. Can be improved. At the same time, gas generation at high temperatures can be further reduced.

  In the secondary battery according to the present invention, by integrating the positive electrode, the negative electrode, and the separator by thermosetting the binder contained in the positive electrode and the negative electrode, the internal impedance at the initial stage of the charge / discharge cycle is lowered. Since the value can be maintained even when the charge / discharge cycle proceeds, the cycle life can be further improved. At the same time, gas generation at high temperatures can be further reduced.

  The non-aqueous electrolyte secondary battery according to the present invention includes a positive electrode current collector, a positive electrode including a positive electrode active material layer carried on one or both surfaces of the positive electrode current collector, a negative electrode current collector, An electrode group comprising a negative electrode including a negative electrode active material layer supported on one or both surfaces of a negative electrode current collector and containing a material that absorbs and releases lithium ions; and a separator disposed between the positive electrode and the negative electrode; A non-aqueous electrolyte containing a non-aqueous solvent impregnated in the electrode group and a lithium salt dissolved in the non-aqueous solvent; a sheet containing the electrode group and including a resin layer and having a thickness of 0.5 mm or less The exterior material which consists of; The porosity of the positive electrode active material layer is lower than the porosity of the negative electrode active material layer. The positive electrode active material layer has a thickness of 10 to 100 μm. Further, the non-aqueous solvent contains γ-butyrolactone in an amount of 40% by volume to 95% by volume based on the total amount of the non-aqueous solvent.

  According to such a secondary battery, since the amount of gas generation can be reduced, it is possible to prevent the exterior material made of a sheet having a thickness of 0.5 mm or less including the resin layer from expanding. As a result, it is possible to use a lightweight exterior material, and furthermore, it is possible to maintain practical large current discharge characteristics and charge / discharge cycle characteristics, so that it has excellent large current discharge characteristics, long life, and weight energy density. A non-aqueous electrolyte secondary battery having a high value can be realized.

[Example]
Hereinafter, preferred embodiments of the present invention will be described in detail.

Example 1
<Preparation of positive electrode>
First, 91% by weight of lithium cobalt oxide (Li _x CoO ₂ ; X is 0 ≦ X ≦ 1) powder, 3.5% by weight of acetylene black, 3.5% by weight of graphite, and ethylene propylene diene monomer powder 2 After adding wt% and toluene and mixing together, it was applied to both sides of a current collector made of a porous aluminum foil (thickness 15 μm) having 10 mm ² pores with a diameter of 0.5 mm, A positive electrode having a structure in which the electrode density was 3 g / cm ³ and the positive electrode layer was supported on both sides of the current collector was produced by pressing.

<Production of negative electrode>
93% by weight of powder of mesophase pitch carbon fiber (fiber diameter 8 μm, average fiber length 20 μm, average interplanar spacing (d ₀₀₂ ) 0.3360 nm) heat treated at 3000 ° C. as a carbonaceous material, as a binder 7% by weight of polyvinylidene fluoride (PVdF) is mixed and applied to a current collector made of a porous copper foil (thickness: 15 μm) having 10 mm ² holes with a diameter of 0.5 mm. Then, drying and pressing were performed to prepare a negative electrode having a structure in which the electrode density was 1.3 g / cm ³ and the negative electrode layer was supported on the current collector.

<Separator>
A separator made of a polyethylene porous film having a thickness of 25 μm, a heat shrinkage of 20% at 120 ° C. for 1 hour, and a porosity of 50% was prepared.

<Preparation of non-aqueous electrolyte>
Lithium tetrafluoroborate (LiBF ₄ ) is dissolved in a mixed solvent of ethylene carbonate (EC) and γ-butyrolactone (BL) (mixing volume ratio 25:75) at 1.5 mol / 1 to prepare a non-aqueous electrolyte. did.

<Production of electrode group>
A belt-like positive electrode lead was welded to the positive electrode current collector, and a belt-like negative electrode lead was welded to the negative electrode current collector, and then the positive electrode and the negative electrode were spirally wound through the separator therebetween. Then, it shape | molded in flat shape and produced the electrode group.

  A laminate film having a thickness of 100 μm in which both surfaces of an aluminum foil were covered with polypropylene was formed into a bag shape, and the electrode group was accommodated in the bag so that the laminated surface shown in FIG. 3 described above could be seen from the opening of the bag. Polyvinylidene fluoride (PVdF) which is an adhesive polymer was dissolved in 0.3% by weight in dimethylformamide (boiling point: 153 ° C.) which is an organic solvent. The obtained solution was injected into the electrode group in the laminate film so that the amount per battery capacity of 100 mAh was 0.2 ml, and the solution was infiltrated into the electrode group, and was applied to the entire surface of the electrode group. Attached.

  Next, the electrode group in the laminate film is vacuum-dried at 80 ° C. for 12 hours to evaporate the organic solvent, and hold the polymer having adhesiveness in the gaps between the positive electrode, the negative electrode, and the separator, and the electrode group A porous adhesive part was formed on the surface of the film. The total amount of PVdF was 0.6 mg per 100 mAh battery capacity.

  The non-aqueous electrolyte is injected into the electrode group in the laminate film so that the amount per battery capacity of 1 Ah is 4.7 g, and has the structure shown in FIGS. A thin nonaqueous electrolyte secondary battery having a height of 40 mm and a height of 70 mm was assembled.

  The following treatment was applied to the non-aqueous electrolyte secondary battery as an initial charging step. First, after being left in a high temperature environment of 40 ° C. for 5 hours, constant current / constant voltage charging was performed for 10 hours to 4.2 V at 0.2 C (120 mA) in that environment. Thereafter, the battery was discharged at 2.7 C to 2.7 V, and the second cycle was charged under the same conditions as in the first cycle to produce a nonaqueous electrolyte secondary battery.

  The capacity of the obtained nonaqueous solvent secondary battery and the internal impedance of 1 kHz were measured. Moreover, in order to investigate a large current discharge characteristic, the capacity maintenance rate at the time of 2C discharge at room temperature (20 degreeC) was measured. In order to investigate the charge / discharge cycle characteristics, the capacity retention rate after 300 cycles was measured by repeating a cycle of 4.2 V constant current / constant voltage at 0.5 C rate for 3 hours and 1 C rate 2.7 V discharge. . Moreover, the swelling after high-temperature storage for 120 hours at 85 degreeC after 4.2V charge was measured. Table 1 shows the electrolyte composition, initial charge conditions, and battery characteristics of the battery of Example 1 described above.

(Example 2 to Example 7)
A thin non-aqueous electrolyte secondary battery was obtained and evaluated in the same manner as in Example 1 except that the composition of the solvent of the electrolyte solution was changed as shown in Table 1. Table 1 shows the electrolyte composition, initial charge conditions, and battery characteristics of the battery of each example.

(Example 8)
Example 8 uses an aluminum can having a thickness of 0.2 mm as an exterior material, does not add an adhesive polymer, and has outer dimensions of 3.2 mm thickness, 40 mm width, and 70 mm height. A thin non-aqueous electrolyte secondary battery was obtained in the same manner as the thin non-aqueous electrolyte secondary battery of Example 1, and the battery was evaluated. Table 1 shows the electrolyte composition, initial charge conditions, and battery characteristics of the battery of Example 8.

(Example 9 to Example 11)
A thin nonaqueous electrolyte secondary battery was obtained and evaluated in the same manner as in Example 1 except that Example 1 and the initial charging temperature were changed as shown in Table 1. Table 1 shows the electrolyte composition, initial charge conditions, and battery characteristics of the batteries of each example.

(Examples 12 and 13)
A thin non-aqueous electrolyte secondary battery was obtained and evaluated in the same manner as in Example 1 except that the composition of the solvent of the electrolyte solution was changed as shown in Table 1. Table 1 shows the electrolyte composition, initial charge conditions, and battery characteristics of the battery of each example.

(Comparative Example 1)
A thin non-aqueous electrolyte secondary battery was obtained and evaluated in the same manner as in Example 1 except that 1.5 mol / l LiBF ₄ dissolved in 100% BL was used as the non-aqueous electrolyte. Table 2 shows the electrolyte composition, initial charge conditions, and battery characteristics of the battery of Comparative Example 1.

(Comparative Example 2)
A thin non-aqueous solution similar to that of Example 1 except that a non-aqueous electrolyte is a mixed solvent of BL, EC, and MEC (volume ratio 50:25:25) in which 1.5 mol / l LiBF ₄ is dissolved. An electrolyte secondary battery was obtained and evaluated. Table 2 shows the electrolyte composition, initial charge condition, and battery characteristics of the battery of Comparative Example 2.

(Comparative Example 3)
Same as Example 1 except that non-aqueous electrolyte was prepared by dissolving 1.5 mol / l LiBF ₄ in BL and EC (volume ratio 50:50), and changing the temperature and charge rate at the time of initial charge. A thin non-aqueous electrolyte secondary battery was obtained and evaluated. Table 2 shows the electrolyte composition, initial charge condition, and battery characteristics of the battery of Comparative Example 3.

(Comparative Example 4)
A thin non-aqueous electrolyte secondary battery similar to that of Example 1 was obtained except that BL and MEC (volume ratio 25:75) dissolved in 1 mol / l LiPF ₆ were used as the non-aqueous electrolyte, and battery evaluation was performed. went. Table 2 shows the electrolyte composition, initial charge condition, and battery characteristics of the battery of Comparative Example 4.

(Comparative Example 5)
A thin non-aqueous electrolyte secondary battery similar to that in Example 1 was obtained except that BL and EC (volume ratio 25:75) dissolved in 1.5 mol / l LiBF ₄ were used as the non-aqueous electrolyte. Evaluation was performed. Table 2 shows the electrolyte composition, initial charge conditions, and battery characteristics of the battery of Comparative Example 5.

(Comparative Example 6)
The same thinness as in Example 1 except that 0.8 mol / l LiPF ₆ dissolved in BL and EC (volume ratio 50:50) was used as the non-aqueous electrolyte, and the temperature at the initial charge was 25 ° C. A non-aqueous electrolyte secondary battery was obtained and evaluated. Table 2 shows the electrolyte composition, initial charge conditions, and battery characteristics of the battery of Comparative Example 6.

(Comparative Example 7)
A non-aqueous electrolyte solution prepared by dissolving 1.5 mol / l LiBF ₄ in BL and EC (volume ratio 50:50), and the same thinness as in Example 8 except that the temperature at the initial charge was 25 ° C. A non-aqueous electrolyte secondary battery was obtained and evaluated. Table 2 shows the electrolytic solution composition, initial charge conditions, and battery characteristics of the battery of Comparative Example 7.

(Comparative Example 8)
A non-aqueous electrolyte solution prepared by dissolving 1.5 mol / l LiBF ₄ in BL and EC (volume ratio 99: 1), and the same thinness as in Example 1 except that the temperature at the initial charge was 25 ° C. A non-aqueous electrolyte secondary battery was obtained and evaluated. Table 2 shows the electrolyte composition, initial charge condition, and battery characteristics of the battery of Comparative Example 8.

(Comparative Example 9)
A thin non-aqueous electrolyte secondary battery similar to that of Example 1 except that non-aqueous electrolyte using BL, EC, and DEC (volume ratio 50:25:25) in which 1.5 mol / l LiBF ₄ is dissolved is used. The battery was evaluated. Table 2 shows the electrolyte composition, initial charge condition, and battery characteristics of the battery of Comparative Example 9.

(Comparative Example 10)
A thin nonaqueous electrolyte secondary battery similar to that of Example 1 except that BL, EC, and MEC (volume ratio 50:25:25) in which 1.5 mol / l LiBF ₄ is dissolved are used as the nonaqueous electrolyte. The battery was evaluated. Table 2 shows the electrolyte composition, initial charge conditions, and battery characteristics of the battery of Comparative Example 10.

(Comparative Example 11)
A thin nonaqueous electrolyte secondary solution in the same manner as in Example 1, except that 1.5 mol / l LiBF ₄ dissolved in BL, PC and EC (volume ratio 50:25:25) is used as the nonaqueous electrolyte solution. A battery was obtained and evaluated. Table 2 shows the electrolyte composition, initial charge condition, and battery characteristics of the battery of Comparative Example 11.

  As is apparent from Tables 1 and 2, a non-aqueous electrolyte solution containing a non-aqueous solvent containing a packaging material having a thickness of 0.3 mm or less and a BL containing more than 50% by volume and 95% by volume or less of BL was provided. It turns out that the secondary battery of Examples 1-13 can suppress that an exterior material swells at the time of high temperature storage, and can improve the discharge capacity in 2C, and the capacity maintenance rate after 300 cycles.

  On the other hand, although the secondary batteries of Comparative Examples 1-3 and 11 can suppress the swelling of the exterior material during high-temperature storage, the discharge capacity at 2C and the capacity retention rate after 300 cycles are in Examples 1-13. It turns out that it is inferior compared. Moreover, it turns out that the secondary battery of Comparative Examples 4-10 has a large swelling of the exterior material at the time of high temperature storage compared with Examples 1-13. Note that the non-aqueous electrolyte contained in the secondary battery of Comparative Example 1 corresponds to the non-aqueous electrolyte disclosed in Japanese Patent Laid-Open No. 11-97062 described above. Further, the non-aqueous electrolyte contained in the secondary battery of Comparative Example 11 corresponds to the non-aqueous electrolyte disclosed in the above-mentioned JP-A-4-14769.

(Example 14)
An aluminum can with a thickness of 0.35 mm is used as the exterior material, and the thickness of the electrode group is reduced so that the battery dimensions are the same as in Example 1 (thickness is 3 mm, width is 40 mm, and height is 70 mm). Except for this, a thin nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 described above. The obtained secondary battery had a capacity of 0.4 Ah.

(Example 15)
As a non-aqueous electrolyte, lithium tetrafluoroborate (LiBF) was added to a non-aqueous solvent composed of 24% by volume of ethylene carbonate (EC), 75% by volume of γ-butyrolactone (BL) and 1% by volume of vinylene carbonate (VC). _A thin nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that ₄ ) dissolved in 1.5 mol / l was used.

(Example 16)
As a non-aqueous electrolyte, lithium tetrafluoroborate (LiBF) was added to a non-aqueous solvent consisting of 23% by volume of ethylene carbonate (EC), 75% by volume of γ-butyrolactone (BL) and 2% by volume of vinylene carbonate (VC). _A thin nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that ₄ ) dissolved in 1.5 mol / l was used.

(Example 17)
As a non-aqueous electrolyte, boron tetrafluoride was added to a non-aqueous solvent comprising 24.5% by volume of ethylene carbonate (EC), 75% by volume of γ-butyrolactone (BL) and 0.5% by volume of vinylene carbonate (VC). A thin non-aqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 except that 1.5 mol / l of lithium acid (LiBF ₄ ) was dissolved.

(Example 18)
As a non-aqueous electrolyte, lithium tetrafluoroborate (LiBF ₄ ) was added to a non-aqueous solvent composed of 25% by volume of ethylene carbonate (EC), 74% by volume of γ-butyrolactone (BL) and 1% by volume of toluene. A thin non-aqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 except that a dissolved amount of 0.5 mol / l was used.

  Regarding the obtained secondary batteries of Examples 15 to 18, the capacity, the internal impedance, the capacity retention rate at the time of 2C discharge, the capacity maintenance rate after 300 cycles, and 85 ° C. were the same as described in Example 1 above. The swelling after storage was measured and the results are shown in Table 3 below.

  As is clear from Table 3, the secondary batteries of Examples 15 to 17 having a non-aqueous electrolyte containing BL, EC and VC of more than 50% by volume and 95% by volume or less, and more than 50% by volume, The secondary battery of Example 18 provided with a nonaqueous electrolytic solution containing 95% by volume or less of BL, EC, and an aromatic compound has a higher capacity retention rate after 300 cycles than the secondary battery of Example 1. I understand that.

(Example 19)
As the separator, except that a polyethylene porous film having a thickness of 25 μm, a thermal shrinkage at 120 ° C. for 1 hour of 20%, an air permeability of 90 sec / 100 cm ³ and a porosity of 50% is used. A thin non-aqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 described above.

(Example 20)
A thin non-aqueous electrolyte secondary battery was produced in the same manner as in Example 19 except that the air permeability of the separator porous film was 580 sec / 100 cm ³ .

(Example 21)
A thin nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 19 described above except that the air permeability of the porous sheet of the separator was set to 400 sec / 100 cm ³ .

(Example 22)
A thin non-aqueous electrolyte secondary battery was manufactured in the same manner as in Example 19 except that the air permeability of the porous sheet of the separator was 150 sec / 100 cm ³ .

  For the obtained secondary batteries of Examples 19 to 22, the capacity, the internal impedance, the capacity retention rate at the time of 2C discharge, the capacity retention rate after 300 cycles, and 85 ° C. were the same as described in Example 1 above. The swelling after storage was measured and the results are shown in Table 4 below.

(Example 23)
An electrode group was prepared in the same manner as described in Example 1 except that no polymer having adhesiveness was added. The obtained electrode group was accommodated in an aluminum can having a thickness of 0.20 mm as an exterior material. Subsequently, the positive electrode, the negative electrode, and the separator are contained in the positive electrode and the negative electrode by pressing the exterior material at a pressure of 10 kg / cm ² along the thickness direction of the electrode group in a high-temperature vacuum atmosphere at 80 ° C. The agent was thermoset and integrated.

Lithium tetrafluoroborate (LiBF ₄ ) in a non-aqueous solvent consisting of 24.5% by volume ethylene carbonate (EC), 75% by volume γ-butyrolactone (BL) and 0.5% by volume vinylene carbonate (VC) Was dissolved at 1.5 mol / l to prepare a non-aqueous electrolyte. The non-aqueous electrolyte is injected into the electrode group in the aluminum can so that the amount per battery capacity of 1 Ah is the same as 4.7 g, and sealed to provide a thickness of 3.2 mm, a width of 40 mm, and a height. A thin non-aqueous electrolyte secondary battery having a thickness of 70 mm was assembled.

(Example 24)
An electrode group was prepared in the same manner as described in Example 1 except that no polymer having adhesiveness was added. The obtained electrode group was accommodated in an aluminum can having a thickness of 0.20 mm as an exterior material. Subsequently, the positive electrode, the negative electrode, and the separator are contained in the positive electrode and the negative electrode by pressing the exterior material at a pressure of 10 kg / cm ² along the thickness direction of the electrode group in a high-temperature vacuum atmosphere at 80 ° C. The agent was thermoset and integrated.

Lithium tetrafluoroborate (LiBF ₄ ) is added to a nonaqueous solvent composed of 23% by volume of ethylene carbonate (EC), 75% by volume of γ-butyrolactone (BL), and 2% by volume of vinylene carbonate (VC). Mol / l was dissolved to prepare a non-aqueous electrolyte. The non-aqueous electrolyte solution is injected into the electrode group in the aluminum can so that the amount per battery capacity of 1Ah is the same as 4.7 g, and the thickness is 3.2 mm, the width is 40 mm, and the height is 70 mm. A non-aqueous electrolyte secondary battery was assembled.

  For the obtained secondary batteries of Examples 23 to 24, the capacity, the internal impedance, the capacity maintenance rate at 2C discharge, the capacity maintenance rate after 300 cycles, and 85 ° C. were the same as described in Example 1 above. The swelling after storage was measured and the results are shown in Table 5 below.

  As is clear from Table 5, the secondary batteries of Examples 23 to 24 have a high capacity, a high capacity retention rate during 2C discharge and after 300 cycles, and can suppress swelling when stored at 85 ° C. Recognize.

(Example 25)
As the exterior material, a laminated film having a thickness of 500 μm in which both surfaces of an aluminum foil are covered with polypropylene is used, and the battery dimensions are 4 mm, width is 100 mm, and height is 280 mm. Similarly, a nonaqueous electrolyte secondary battery was produced.

  About the obtained secondary battery of Example 25, in the same manner as described in Example 1 above, the capacity, the capacity maintenance rate at the time of 2C discharge, the capacity maintenance rate after 300 cycles, and the swelling after storage at 85 ° C. Was measured. As a result, the secondary battery of Example 25 had a capacity of 6 Ah, a capacity maintenance ratio during 2C discharge of 85%, a capacity maintenance ratio after 300 cycles of 90%, and a swelling after storage at 85 ° C. of 3%. there were. Therefore, when a non-aqueous solvent containing BL of more than 50% by volume and 95% by volume or less is used, it can be confirmed that a laminate film having a thickness of 0.5 mm can be used as an exterior material of a large battery such as an electric vehicle. It was.

(Example 26)
<Preparation of positive electrode>
First, 91% by weight of lithium cobalt oxide (Li _x CoO ₂ ; X is 0 ≦ X ≦ 1) powder, 2.5% by weight of acetylene black, 3% by weight of graphite, and 4% by weight of polyvinylidene fluoride (PVdF) % And N-methylpyrrolidone (NMP) solution are added and mixed together. After coating on both sides of a current collector made of aluminum foil with a thickness of 10 μm, each surface of the current collector is dried and pressed. A positive electrode having a structure in which a positive electrode active material layer having a density of 3.3 g / cm ³ , a porosity of 34%, and a thickness of 48 μm was carried was prepared.

<Production of negative electrode>
93% by weight of powder of mesophase pitch carbon fiber (fiber diameter 8 μm, average fiber length 20 μm, average interplanar spacing (d ₀₀₂ ) 0.3360 nm) heat treated at 3000 ° C. as a carbonaceous material, as a binder 7% by weight of polyvinylidene fluoride (PVdF) and an N-methylpyrrolidone solution were mixed, applied to both sides of a current collector made of copper foil having a thickness of 10 μm, dried and pressed to collect current. A negative electrode having a structure in which a negative electrode active material layer having a density of 1.3 g / cm ³ , a porosity of 41%, and a thickness of 45 μm was supported on each surface of the body.

<Separator>
A separator made of a polyethylene porous film having a thickness of 20 μm and a porosity of 50% was prepared.

<Production of electrode group>
The positive electrode and the negative electrode were spirally wound through the separator therebetween, and then formed into a flat shape to produce a flat electrode group having a thickness of 2.5 mm, a width of 30 mm, and a height of 50 mm. .

<Preparation of non-aqueous electrolyte>
Lithium tetrafluoroborate (LiBF ₄ ) is dissolved in a mixed solvent of ethylene carbonate (EC) and γ-butyrolactone (BL) (mixing volume ratio 25:75) at 1.5 mol / 1 to prepare a non-aqueous electrolyte. did.

  Next, a laminate film having a thickness of 100 μm in which both surfaces of the aluminum foil were covered with polypropylene was formed into a bag shape, and the electrode group was accommodated in this, and both surfaces were sandwiched by holders so that the thickness was 2.7 mm. Polyvinylidene fluoride (PVdF) which is an adhesive polymer was dissolved in 0.3% by weight in dimethylformamide (boiling point: 153 ° C.) which is an organic solvent. The obtained solution was injected into the electrode group in the laminate film so that the amount per battery capacity of 100 mAh was 0.6 ml, and the solution was infiltrated into the electrode group, and over the entire surface of the electrode group. Attached.

  Next, the electrode group in the laminate film is vacuum-dried at 80 ° C. for 12 hours to evaporate the organic solvent, and hold the polymer having adhesiveness in the gaps between the positive electrode, the negative electrode, and the separator, and the electrode group A porous adhesive part was formed on the surface of the film.

  The non-aqueous electrolyte solution is injected into the electrode group in the laminate film so that the amount per battery capacity 1Ah is 2 g, and the thin non-aqueous electrolyte secondary solution has a thickness of 3 mm, a width of 32 mm, and a height of 55 mm. I assembled the battery.

  The following treatment was applied to the non-aqueous electrolyte secondary battery as an initial charging step. First, after being left in a high temperature environment of 40 ° C. for 5 hours, constant current / constant voltage charging was performed for 10 hours to 4.2 V at 0.2 C (120 mA) in that environment. Thereafter, the battery was discharged at 2.7 C to 2.7 V, and the second cycle was charged under the same conditions as in the first cycle to produce a nonaqueous electrolyte secondary battery.

  In order to examine the large current discharge characteristics at room temperature (20 ° C.) of the obtained nonaqueous solvent secondary battery, the capacity retention rate during 3C discharge was measured. At this time, the discharge capacity at 0.2 C was set as the reference capacity. Also, in order to investigate the charge / discharge cycle characteristics, a cycle of 4.2V constant current / constant voltage for 3 hours at 0.7C rate and 2.7V discharge at 1C rate was repeated, and the capacity retention rate after 300 cycles was measured. did. Moreover, the swelling after high-temperature storage for 120 hours at 85 degreeC after 4.2V charge was measured. Table 6 shows the initial capacity, the active material layer thickness, the content ratio of γ-butyrolactone as the solvent of the electrolytic solution, and the battery characteristics of the battery of Example 26 described above.

(Examples 27-37, A, B and Comparative Examples 12-13)
A thin non-aqueous electrolyte solution 2 was prepared in the same manner as in Example 26 except that the thicknesses of one surface of the positive electrode active material layer and the negative electrode active material layer and the content ratio of γ-butyrolactone as the solvent of the electrolyte solution were changed as shown in Table 6. A secondary battery was obtained and evaluated. Table 6 shows the initial capacity of each battery, the thickness of the active material layer, the content ratio of γ-butyrolactone as a solvent of the electrolytic solution, and battery characteristics.

  As is apparent from Table 6, the positive electrode active material layer has a positive electrode having a thickness of 10 to 100 μm, an exterior material having a thickness of 0.3 mm or less, and a nonaqueous solvent containing 40 to 95% by volume of BL. The secondary batteries of Examples 26 to 37, A, and B including the non-aqueous electrolyte that can suppress the expansion of the exterior material during high temperature storage, the initial capacity, the discharge capacity at 3C, and after 300 cycles It can be seen that the capacity retention rate of the can be improved.

  On the other hand, it can be seen that the secondary battery of Comparative Example 12 is inferior to Examples 26 to 37, A, and B in the discharge capacity at 3C and the capacity retention rate after 300 cycles. Moreover, it turns out that the secondary battery of the comparative example 13 is inferior to Examples 26-37, A, and B in the discharge capacity in 3C.

(Example 38)
As a non-aqueous electrolyte, boron tetrafluoride was added to a non-aqueous solvent comprising 24.9% by volume of ethylene carbonate (EC), 75% by volume of γ-butyrolactone (BL) and 0.1% by volume of vinylene carbonate (VC). A thin non-aqueous electrolyte secondary battery was produced in the same manner as in Example 26 described above except that 1.5 mol / l of lithium acid (LiBF ₄ ) dissolved therein was used.

(Example 39)
As a non-aqueous electrolyte, lithium tetrafluoroborate (LiBF) was added to a non-aqueous solvent composed of 24% by volume of ethylene carbonate (EC), 75% by volume of γ-butyrolactone (BL) and 1% by volume of vinylene carbonate (VC). ₄ ) A thin non-aqueous electrolyte secondary battery was produced in the same manner as in Example 26 except that 1.5 mol / l dissolved was used.

(Example 40)
As a non-aqueous electrolyte, lithium tetrafluoroborate (LiBF) was added to a non-aqueous solvent composed of 20% by volume of ethylene carbonate (EC), 75% by volume of γ-butyrolactone (BL) and 5% by volume of vinylene carbonate (VC). ₄ ) A thin non-aqueous electrolyte secondary battery was produced in the same manner as in Example 26 except that 1.5 mol / l dissolved was used.

(Example 41)
As a non-aqueous electrolyte, lithium tetrafluoroborate (LiBF ₄ ) was added to a non-aqueous solvent composed of 25% by volume of ethylene carbonate (EC), 74% by volume of γ-butyrolactone (BL) and 1% by volume of toluene. A thin non-aqueous electrolyte secondary battery was produced in the same manner as in Example 26 described above, except that a dissolved amount of 0.5 mol / l was used.

  For the obtained secondary batteries of Examples 38 to 41, the capacity, the capacity maintenance rate at the time of 3C discharge, the capacity maintenance rate after 300 cycles, and the storage at 85 ° C. were the same as described in Example 26 above. The results are shown in Table 7 below.

  As is apparent from Table 7, the secondary battery of Examples 38 to 40 with a non-aqueous electrolyte containing 40 to 95% by volume of BL, EC and VC, and 40 to 95% by volume of BL, EC and fragrance It can be seen that the secondary battery of Example 41 provided with the non-aqueous electrolyte containing a group compound has a higher capacity retention rate after 300 cycles than the secondary battery of Example 26.

(Example 42)
As the separator, except that a polyethylene porous film having a thickness of 25 μm, a thermal shrinkage at 120 ° C. for 1 hour of 20%, an air permeability of 90 sec / 100 cm ³ and a porosity of 50% is used. A thin nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 26 described above.

(Example 43)
A thin non-aqueous electrolyte secondary battery was produced in the same manner as in Example 42 described above, except that the air permeability of the porous film of the separator was 580 sec / 100 cm ³ .

(Example 44)
A thin non-aqueous electrolyte secondary battery was produced in the same manner as in Example 42 described above except that the air permeability of the porous sheet of the separator was set to 400 sec / 100 cm ³ .

(Example 45)
A thin non-aqueous electrolyte secondary battery was produced in the same manner as in Example 42 described above except that the air permeability of the porous sheet of the separator was 150 sec / 100 cm ³ .

  For the obtained secondary batteries of Examples 42 to 45, the capacity, the capacity maintenance rate at the time of 3C discharge, the capacity maintenance rate after 300 cycles, and the storage at 85 ° C. were the same as described in Example 26 above. The results are shown in Table 8 below.

(Example 46)
An electrode group was produced in the same manner as described in Example 26 except that no polymer having adhesiveness was added. The obtained electrode group was accommodated in an aluminum can having a thickness of 0.18 mm as an exterior material. Subsequently, the positive electrode, the negative electrode, and the separator are contained in the positive electrode and the negative electrode by pressing the exterior material at a pressure of 10 kg / cm ² along the thickness direction of the electrode group in a high-temperature vacuum atmosphere at 80 ° C. The agent was thermoset and integrated.

Lithium tetrafluoroborate (LiBF ₄ ) in a non-aqueous solvent consisting of 24.5% by volume ethylene carbonate (EC), 75% by volume γ-butyrolactone (BL) and 0.5% by volume vinylene carbonate (VC) Was dissolved at 1.5 mol / l to prepare a non-aqueous electrolyte. The non-aqueous electrolyte is injected into the electrode group in the aluminum can so that the amount per battery capacity of 1 Ah is the same as 4.7 g, and sealed to provide a thickness of 3 mm, a width of 32 mm, and a height of 55 mm. A thin non-aqueous electrolyte secondary battery was assembled.

(Example 47)
An electrode group was produced in the same manner as described in Example 26 except that no polymer having adhesiveness was added. The obtained electrode group was accommodated in an aluminum can having a thickness of 0.25 mm as an exterior material. Subsequently, the positive electrode, the negative electrode, and the separator are contained in the positive electrode and the negative electrode by pressing the exterior material at a pressure of 10 kg / cm ² along the thickness direction of the electrode group in a high-temperature vacuum atmosphere at 80 ° C. The agent was thermoset and integrated.

Lithium tetrafluoroborate (LiBF ₄ ) is added to a nonaqueous solvent composed of 24% by volume of ethylene carbonate (EC), 75% by volume of γ-butyrolactone (BL) and 2% by volume of vinylene carbonate (VC). Mol / l was dissolved to prepare a non-aqueous electrolyte. The non-aqueous electrolyte is injected into the electrode group in the aluminum can so that the amount per battery capacity of 1 Ah is the same as 4.7 g, and is a thin non-aqueous water having a thickness of 3 mm, a width of 32 mm, and a height of 55 mm. An electrolyte secondary battery was assembled.

  For the obtained secondary batteries of Examples 46 to 47, the capacity, the capacity maintenance rate at the time of 3C discharge, the capacity maintenance rate after 300 cycles, and the storage at 85 ° C. were the same as described in Example 26 above. The results are shown in Table 9 below.

  As is clear from Table 9, the secondary batteries of Examples 46 to 47 have a high capacity, a high capacity retention rate at the time of 3C discharge and after 300 cycles, and can suppress swelling when stored at 85 ° C. Recognize.

(Example 48)
As the exterior material, a laminated film having a thickness of 500 μm in which both surfaces of an aluminum foil are covered with polypropylene is used, and the battery dimensions are 4 mm in thickness, 80 mm in width, and 220 mm in height. Similarly, a nonaqueous electrolyte secondary battery was produced.

  For the obtained secondary battery of Example 48, the capacity, the capacity maintenance rate at the time of 3C discharge, the capacity maintenance rate after 300 cycles, and the swelling after storage at 85 ° C. were the same as described in Example 26 above. Was measured. As a result, the secondary battery of Example 48 had a capacity of 3.2 Ah, a capacity retention rate at 3C discharge of 96%, a capacity retention rate of 300% after 300 cycles, and a swelling after storage at 85 ° C. of 3%. %Met. Therefore, when the thickness of the positive electrode active material layer is 10 to 100 μm and a nonaqueous solvent containing 40 to 95% by volume of BL is used, the thickness is 0.5 mm as an exterior material of a large battery such as an electric vehicle. It was confirmed that the laminate film can be used.

Sectional drawing which shows an example of the 1st non-aqueous-electrolyte secondary battery concerning invention. The expanded sectional view which shows the A section of FIG. The schematic diagram which shows the boundary vicinity of the positive electrode in the secondary battery of FIG. 1, a separator, and a negative electrode. Sectional drawing for demonstrating the thickness of the positive electrode active material layer in the 2nd nonaqueous electrolyte secondary battery concerning this invention. Sectional drawing which shows an example of the 2nd nonaqueous electrolyte secondary battery concerning this invention. The expanded sectional view which shows the B section of FIG. The schematic diagram which shows the boundary vicinity of the positive electrode in the secondary battery of FIG. 5, a separator, and a negative electrode.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Exterior material, 2 ... Electrode group, 3 ... Separator, 4 ... Positive electrode layer, 5 ... Positive electrode collector, 6 ... Negative electrode layer, 7 ... Negative electrode collector, 8 ... Adhesive layer, 9 ... High having adhesiveness Molecule, 12 ... positive electrode, 13 ... negative electrode, 21 ... exterior material, 22 ... electrode group, 23 ... separator, 24 ... positive electrode layer, 25 ... positive electrode current collector, 26 ... negative electrode layer, 27 ... negative electrode current collector, 28 ... Adhesive layer, 29 ... polymer having adhesiveness, 32 ... positive electrode, 33 ... negative electrode.

Claims (12)

A positive electrode including a positive electrode current collector and a positive electrode active material layer supported on one or both surfaces of the positive electrode current collector, and supported on one or both surfaces of the negative electrode current collector and the negative electrode current collector, An electrode group comprising a negative electrode including a negative electrode active material layer containing a material to be released, and a separator disposed between the positive electrode and the negative electrode;
A non-aqueous electrolyte solution impregnated in the electrode group and comprising a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent;
The electrode group is housed, and includes a sheet exterior material having a thickness of 0.5 mm or less including a resin layer;
The porosity of the positive electrode active material layer is lower than the porosity of the negative electrode active material layer, the thickness of the positive electrode active material layer is 10 to 60 μm, and the thickness of the negative electrode active material layer is 10 to 65 μm. ,
The non-aqueous solvent contains γ-butyrolactone in an amount of 40% by volume to 95% by volume based on the total amount of the non-aqueous solvent. A positive electrode including a positive electrode current collector and a positive electrode active material layer supported on one or both surfaces of the positive electrode current collector, and supported on one or both surfaces of the negative electrode current collector and the negative electrode current collector, An electrode group comprising a negative electrode including a negative electrode active material layer containing a material to be released, and a separator disposed between the positive electrode and the negative electrode;
A non-aqueous electrolyte solution impregnated in the electrode group and comprising a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent;
An exterior material having a thickness of 0.3 mm or less in which the electrode group is accommodated;
The porosity of the positive electrode active material layer is lower than the porosity of the negative electrode active material layer, the thickness of the positive electrode active material layer is 10 to 60 μm, and the thickness of the negative electrode active material layer is 10 to 65 μm. ,
The non-aqueous solvent contains γ-butyrolactone in an amount of 40% by volume to 95% by volume based on the total amount of the non-aqueous solvent.   The non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the positive electrode active material layer has a porosity of 25 to 40%, and the negative electrode active material layer has a porosity of 35 to 50%.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the non-aqueous solvent further includes ethylene carbonate.   The non-aqueous solvent further includes ethylene carbonate and a third solvent consisting of at least one selected from propylene carbonate, vinylene carbonate, trifluoropropylene, diethyl carbonate, methyl ethyl carbonate, and an aromatic compound. The nonaqueous electrolyte secondary battery according to claim 1 or 2.   The positive electrode and the separator are integrated with an adhesive polymer that exists in at least a part of these boundaries, and the negative electrode and the separator have an adhesive property that exists in at least a part of these boundaries. 3. The non-aqueous electrolyte secondary battery according to claim 1, wherein the non-aqueous electrolyte secondary battery is integrated with a polymer.   The non-aqueous electrolyte secondary according to claim 1, wherein the positive electrode, the negative electrode, and the separator are integrated by thermosetting the binder contained in the positive electrode and the negative electrode. battery. The non-aqueous electrolyte secondary battery according to claim 1, wherein the separator includes a porous sheet having an air permeability of 600 seconds / 100 cm ³ or less.   The non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the positive electrode current collector or the negative electrode current collector has a thickness of 5 to 20 µm.   3. The nonaqueous electrolyte secondary battery according to claim 1, wherein the carbonaceous material that occludes and releases lithium ions is a graphite material or a carbonaceous material that has been heat-treated at 500 to 3000 ° C. 3. .   3. The non-aqueous electrolyte secondary battery according to claim 1, wherein the material that absorbs and releases lithium ions is lithium titanium oxide. The non-aqueous electrolyte secondary battery according to claim 1, wherein the lithium salt contains LiPF ₆ or LiBF ₄ .

Images