JP4031405B2 - Non-aqueous electrolyte secondary battery - Google Patents

Description

  The present invention relates to a non-aqueous electrolyte secondary battery and a method for manufacturing the same.

Currently, thin 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 or carbonaceous material is used for the negative electrode, an organic solvent in which a lithium salt is dissolved in the electrolytic solution, and a porous film is used for the separator.

  Although it is desired to reduce the thickness of the battery as the mobile device becomes thinner, it is difficult to put a thin lithium ion secondary battery having a thickness of 4 mm or less into practical use. For this reason, a card-type lithium secondary battery using a polymer electrolyte has been conventionally proposed and developed for practical use.

  However, since the lithium secondary battery using the polymer electrolyte includes a gel polymer in which the nonaqueous electrolyte is held, the impedance of the electrode interface is larger than that of the lithium secondary battery using the nonaqueous electrolyte, and the lithium secondary battery There is a problem that ionic conductivity is low. In addition, in order to maintain the mechanical strength of the polymer electrolyte, it is necessary to make the thickness of the electrolyte thicker than that of the conventional separator, which causes a problem that the energy density is lowered.

  Therefore, the lithium secondary battery using the polymer electrolyte is inferior in volume energy density, cycle life and large current characteristics as compared with a thin lithium secondary battery impregnated with a non-aqueous electrolyte in a solution or liquid state. There is a point.

  On the other hand, the claims of JP-A-10-177865 (Patent Document 1) include a positive electrode, a negative electrode, a separator having an opposing surface holding an electrolytic solution, an electrolytic solution phase, and an electrolytic solution. A lithium ion secondary battery comprising a mixed phase of a polymer gel phase and a polymer solid phase and having an adhesive resin layer for joining the positive electrode and the negative electrode to the opposing surface of the separator is described. Further, the scope of claims of JP-A-10-189054 (Patent Document 2) includes a step of applying a binder resin solution obtained by dissolving a main component polyvinylidene fluoride in a solvent to the separator, A method for producing a lithium ion secondary battery comprising a step of forming a battery laminate by stacking electrodes and drying them while they are in close contact to evaporate the solvent, and a step of impregnating the battery laminate with an electrolyte is described. Yes. Further, in the claims of Japanese Patent Application Laid-Open No. 10-172606 (Patent Document 3), the positive electrode, the negative electrode, and the positive electrode and the negative electrode are disposed and hold an electrolyte containing lithium ions. A lithium ion secondary battery comprising a separator and a porous adhesive resin layer that holds the electrolytic solution and joins the positive electrode, the negative electrode, and the separator is disclosed.

However, the lithium ion secondary battery disclosed in each publication has a problem in that the cycle life and large current discharge characteristics are inferior because the internal resistance is high.
JP-A-10-177865 Japanese Patent Laid-Open No. 10-189054 JP-A-10-172606

The object of the present invention is suitable when the electrode group is impregnated with a non-aqueous electrolyte in a solution or in a liquid state, and the non-aqueous electrolyte secondary is improved in cycle characteristics and can be thinned. it is intended to provide the batteries.

The non-aqueous electrolyte secondary battery according to the present invention includes an electrode group having a structure in which a positive electrode and a negative electrode are wound in a flat shape through a separator therebetween,
A non-aqueous electrolyte impregnated in the electrode group;
The electrode group is housed , and comprises an exterior material having a thickness of 300 μm or less containing metal ,
The electrode group is characterized in that the surface where the laminated structure is exposed has a shape satisfying the following expression (1).

0.9 ≦ L ₂ / L ₁ ≦ 1.2 (1)
In the formula (1), L ₂ is the thickness of the most multilayered portion in the region excluding the curved laminated region in the surface, and L ₁ is a layer in the end portion of the region excluding the curved laminated region. The thickness of the end portion whose number is equal to L ₂ .

Another nonaqueous electrolyte secondary battery according to the present invention includes an electrode group having a structure in which a laminate composed of a positive electrode, a negative electrode, and a separator is bent twice or more,
A non-aqueous electrolyte impregnated in the electrode group;
The electrode group is housed , and comprises an exterior material having a thickness of 300 μm or less containing metal ,
The electrode group is characterized in that the surface where the laminated structure is exposed has a shape satisfying the following expression (2).

0.9 ≦ L ₄ / L ₃ ≦ 1.2 (2)
In the formula (2), L ₄ is the thickness of the outermost multilayer portion in the region excluding the folded laminated region, and L ₃ is the layer in the end portion of the region excluding the folded laminated region. The thickness of the end portion whose number is equal to the L ₄ .

According to the present invention, it is possible to provide a thickness of 4mm is suitable for a thin structure, the discharge capacity and the nonaqueous electrolyte secondary batteries that cycle characteristics are improved.

A first non-aqueous electrolyte secondary battery according to the present invention is a separator comprising a positive electrode, a negative electrode, and a porous sheet having an air permeability of 600 seconds / 100 cm ³ or less, disposed between the positive electrode and the negative electrode. A non-aqueous electrolyte impregnated in the electrode group; an exterior material in which the electrode group is accommodated.

  The positive electrode and the separator are bonded by a polymer having adhesiveness held in each gap. The negative electrode and the separator are bonded by a polymer having adhesiveness held in each gap.

  The second non-aqueous electrolyte secondary battery according to the present invention includes a positive electrode, a negative electrode, and an electrode group having a separator for electrically isolating the positive electrode and the negative electrode; A packaging material; a nonaqueous electrolyte solution impregnated in the electrode group.

  The positive electrode and the separator are bonded to each other by a polymer having adhesive properties scattered inside and at the boundary. Moreover, the said negative electrode and the said separator are adhere | attached with the polymer | macromolecule which has the adhesiveness scattered in the inside and boundary.

  In addition, when there are a plurality of at least one of the positive electrode and the negative electrode, each of the electrodes and the separator is less than the polymer having the adhesive property at the boundary between one of the plurality of electrodes and the separator. It is desirable that a part of the adhesive polymer exists in a part of the boundary.

  Hereinafter, the positive electrode, the negative electrode, the separator, the non-aqueous electrolyte, and the exterior material will be described in detail.

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 holds a polymer having adhesiveness in the gap.

  The positive electrode layer includes a positive electrode active material and a conductive agent. The positive electrode layer includes a binder for binding the positive electrode active material in addition to 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 content of the conductive material of the positive electrode is preferably in the range of 3 to 20% by weight when the positive electrode active material is 80 to 95% by weight.

  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), ethylene-propylene-diene copolymer (EPDM), styrene-butadiene rubber (SBR), and polyvinylidene fluoride (PVdF).

  It is desirable that the polymer having adhesiveness is one that can maintain high adhesiveness while holding a nonaqueous electrolytic solution. Furthermore, it is more preferable that such a polymer has high lithium ion conductivity. Examples of the polymer having high adhesiveness while holding the non-aqueous electrolyte and having high lithium ion conductivity include polyacrylonitrile (PAN), polyacrylate (PMMA), polyvinylidene fluoride (PVdF), poly One or more polymers selected from vinyl chloride (PVC) and polyethylene oxide (PEO) can be used. Among these, PVdF is preferable. PVdF can hold a non-aqueous electrolyte and partly gelate when it contains a non-aqueous electrolyte, so that the ionic conductivity in the positive electrode can be further improved.

  The adhesive polymer preferably has a porous structure in the positive electrode. Since the adhesive polymer having a porous structure can hold the non-aqueous electrolyte, the amount of the non-aqueous electrolyte held by the positive electrode can be increased.

  The content of the positive electrode binder and adhesive polymer is preferably in the range of 1 to 10% by weight.

  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.

In particular, as the current collector, 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 are present 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, when 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 there is a possibility that a sufficient cycle life cannot 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 holds a polymer having adhesiveness in the voids.

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

Examples of the active material include carbonaceous materials that occlude and release lithium ions. 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 graphite materials or carbonaceous materials obtained by subjecting mesophase pitch-based carbon fibers to 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 nonaqueous electrolyte secondary battery including a negative electrode containing such a graphite material as a carbonaceous material can greatly improve battery capacity and large current characteristics. The spacing d ₀₀₂ is more preferably at most 0.336 nm.

The carbonaceous material content of the negative electrode is preferably in the range of 5 to ²⁰ g / m ² in a state where the negative electrode is produced.

  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), ethylene-propylene-diene copolymer (EPDM), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVdF), carboxymethyl cellulose (CMC), and the like. Can be used.

  It is desirable that the polymer having adhesiveness is one that can maintain high adhesiveness while holding a nonaqueous electrolytic solution. Furthermore, it is more preferable that such a polymer has high lithium ion conductivity. Examples of the polymer having high adhesiveness while holding the non-aqueous electrolyte and having high lithium ion conductivity include the same polymers as those described above for the positive electrode. Among these, polyvinylidene fluoride is preferable. Polyvinylidene fluoride can hold a non-aqueous electrolyte and partly gelate when the non-aqueous electrolyte is included, so that the ionic conductivity in the negative electrode can be further improved.

  The adhesive polymer preferably has a porous structure in the negative electrode. Since the adhesive polymer having a porous structure can hold the non-aqueous electrolyte, the amount of the non-aqueous electrolyte held by the negative electrode can be increased.

  The content of the negative electrode binder and the polymer having adhesiveness is preferably in the range of 1 to 10% by weight.

  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.

In particular, as the current collector, 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 are present 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, when 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 there is a possibility that a sufficient cycle life cannot 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.

  It is preferable that at least one end portion of the end portion of the negative electrode protrudes compared to the positive electrode. With such a configuration, current concentration at the end of the negative electrode can be relaxed, and cycle life and safety can be improved. In particular, it is desirable to project all end portions of the negative electrode from the positive electrode.

  As the negative electrode, in addition to the above-described carbonaceous material that occludes / releases lithium ions, a metal oxide, a metal sulfide, a metal nitride, or a lithium metal or lithium alloy is used. Can be used.

  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 As this separator, for example, a separator in which a polymer having at least adhesiveness is held in the voids of the porous sheet can be used.

  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.

  It is desirable that the polymer having adhesiveness is one that can maintain high adhesiveness while holding a nonaqueous electrolytic solution. Furthermore, it is more preferable that such a polymer has high lithium ion conductivity. Examples of the polymer having high adhesiveness while holding the non-aqueous electrolyte and having high lithium ion conductivity include the same polymers as those described above for the positive electrode. Among these, polyvinylidene fluoride is preferable. Polyvinylidene fluoride can hold a non-aqueous electrolyte, and when the non-aqueous electrolyte is included, it partially gels, so that the ionic conductivity of the separator can be further improved.

  The adhesive polymer preferably has a porous structure in the separator. Since the adhesive polymer having a porous structure can hold the non-aqueous electrolyte, the amount of the non-aqueous electrolyte held by the separator can be increased.

The content of the polymer having adhesiveness in the separator is preferably 10% by weight or less. If the content exceeds 10% by weight, the ionic conductivity of the nonaqueous electrolytic solution may be lowered, and therefore, the large current discharge characteristics and cycle life may not be sufficiently improved. A more preferred range is 5% by weight or less, and a further preferred range is 1% by weight or less. Further, the lower limit of the content is preferably 1 × 10 ⁻⁵ . If the content is less than 1 × 10 ⁻⁵ wt%, it may be difficult to sufficiently increase the adhesion strength between the separator and the positive electrode and the adhesion strength between the separator and the negative electrode. This is because there is a possibility that it cannot be improved sufficiently. Therefore, the content is preferably in the range of 1 × 10 ⁻⁵ to 10% by weight. A more preferable range of the lower limit is 1 × 10 ⁻⁴ wt%, and a more preferable value is 1 × 10 ⁻³ wt%.

  In the separator, the concentration of the polymer having adhesiveness may be uniform, but the concentration of the polymer having adhesiveness may be uneven. In particular, it is desirable that the concentration of the polymer having adhesiveness is lower than the concentration of the polymer having adhesiveness on the surface facing the positive electrode or the negative electrode. In particular, it is preferable that the concentration of the polymer having adhesiveness at the central portion in the thickness direction of the separator is lower than the concentration of the polymer having adhesiveness on the surface facing the positive electrode or the negative electrode.

  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. 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 still more preferably 400 seconds / 100 cm ³ . The lower limit is more preferably 150 seconds / 100 cm ³ .

  It is preferable that at least one end of the end portion of the separator protrudes compared to the positive electrode or the negative electrode. With such a configuration, when an impact is applied to the battery by accidentally dropping the battery or when the battery is used in a high-temperature environment of 100 ° C. or higher, an internal short circuit is prevented from occurring when the separator is thermally contracted. be able to. Among them, it is desirable to project all the end portions of the separator as compared with the positive electrode or the negative electrode. In addition, when at least one end of the positive electrode protrudes compared to the negative electrode, or when at least one end of the negative electrode protrudes compared to the positive electrode, the end of the separator protrudes compared to the protruding electrode end. It is desirable. In particular, it is preferable that at least one end of the negative electrode protrudes compared to the positive electrode, and the end of the separator protrudes compared to the protruding negative electrode end.

  When projecting at least one end of the end portion of the separator as compared with the positive electrode or the negative electrode, the projecting length is preferably in the range of 0.25 to 2 mm. This is due to the following reason. If the protruding length is shorter than 0.25 mm, it may be difficult to reduce the internal short-circuit occurrence rate. On the other hand, if the protruding length exceeds 2 mm, the volume energy density of the battery may be reduced. A more preferable range is 0.5 to 1.5 mm. However, when at least one end of the positive electrode protrudes compared to the negative electrode, or when at least one end of the negative electrode protrudes compared to the positive electrode, the protruding length is set based on the protruding electrode end. .

  When at least one end of the end portion of the separator is protruded as compared with the positive electrode or the negative electrode, it is preferable that a polymer having adhesiveness is held at the protruded end portion. With such a configuration, the strength of the protruding separator end can be increased, so that the internal short-circuit occurrence rate can be further reduced.

  It is preferable that three types of the polymer having adhesiveness in the positive electrode, the negative electrode, and the separator are the same. With such a configuration, since the adhesive strength between the positive electrode and the separator and the adhesive strength between the negative electrode and the separator can be sufficiently increased, the large current discharge characteristics and the cycle characteristics can be further improved.

4) Non-aqueous electrolyte The non-aqueous electrolyte is a liquid electrolyte prepared by dissolving an electrolyte in a non-aqueous solvent.

  As the non-aqueous solvent, a known non-aqueous solvent can be used as a solvent for a lithium secondary battery, and is not particularly limited, but propylene carbonate (PC) or ethylene carbonate (EC) and a viscosity lower than that of the PC or EC. It is preferable to use a non-aqueous solvent mainly composed of a mixed solvent with one or more kinds of non-aqueous solvents (hereinafter referred to as second solvent) having a donor number of 18 or less.

  As the second type of solvent, for example, chain carbon is preferable, among which dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), diethyl carbonate (DEC), ethyl propionate, methyl propionate, γ-butyrolactone (γ- BL), acetonitrile (AN), ethyl acetate (EA), toluene, xylene or methyl acetate (MA). These second solvents can be used alone or in the form of a mixture of two or more. In particular, the second type solvent preferably has a donor number of 16.5 or less.

  The viscosity of the second solvent is preferably 28 mp or less at 25 ° C. The blending amount of the ethylene carbonate or propylene carbonate in the mixed solvent is preferably 10 to 80% by volume ratio. The blending amount of the ethylene carbonate or propylene carbonate is more preferably 20 to 75% by volume ratio.

  More preferable composition of the mixed solvent is EC and MEC, EC and PC and MEC, EC and MEC and DEC, EC and MEC and DMC, EC and MEC, PC and DEC mixed solvent, and the volume ratio of MEC is 30 to 30. 80% is preferable. A more preferable MEC volume ratio is in the range of 40 to 70%.

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 ]. Of these, LiPF ₆ and LiBF ₄ are preferably used.

  The amount of the electrolyte dissolved in the non-aqueous solvent is preferably 0.5 to 2.0 mol / 1.

  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 the non-aqueous electrolyte 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, when the amount of the non-aqueous electrolyte exceeds 0.6 g / 100 mAh, the amount of the electrolyte becomes large, which may make sealing difficult when using a film exterior material. A more preferable range of the amount of the non-aqueous electrolyte is 0.4 to 0.55 g / 100 mAh.

5) Exterior material As this exterior material, for example, a metal can or a film having a function of blocking moisture can be used. 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, lightweight aluminum is preferable. Examples of the synthetic resin include polyethylene and polypropylene.

  The thickness of the film exterior material is preferably in the range of 50 to 300 μm. This is due to the following reason. When the thickness is less than 50 μm, deformation and breakage are likely to occur. On the other hand, if the thickness is larger than 300 μm, there is a possibility that a high weight energy density cannot be obtained. A more desirable range of thickness is 80 to 150 μm.

  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.

  The adhesive layer preferably contains an adhesive polymer. It is desirable that the polymer having adhesiveness is one that can maintain high adhesiveness while holding a nonaqueous electrolytic solution. Furthermore, it is more preferable that such a polymer has high lithium ion conductivity. Examples of the polymer having high adhesiveness while holding the non-aqueous electrolyte and having high lithium ion conductivity include the same polymers as those described above for the positive electrode. Among these, polyvinylidene fluoride is preferable.

  The adhesive layer preferably has a porous structure. The adhesive layer having a porous structure can increase the amount of the non-aqueous electrolyte retained in the electrode group.

  The total amount of the adhesive polymer contained in the battery is preferably 0.2 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 0.2 mg per 100 mAh of battery capacity, it may be difficult to sufficiently improve the adhesive strength between the positive electrode and the separator and the adhesive strength between the negative electrode and the separator. 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 be reduced and the internal resistance may be increased, and the discharge capacity, large current discharge characteristics, and charge / discharge cycle life are sufficient. It may be difficult to improve. A more preferable range of the total amount of the polymer having adhesiveness is 0.5 to 3 mg per 100 mAh of battery capacity.

  When the total amount of the adhesive polymer contained in the battery is 0.2 to 6 mg per 100 mAh of battery capacity, the amount of the nonaqueous electrolyte is preferably 0.2 to 0.6 g per 100 mAh of battery capacity.

  A thin lithium ion secondary battery as an example of the first and second nonaqueous electrolyte secondary batteries according to the present invention will be described below with reference to FIGS.

  FIG. 1 is a cross-sectional view showing an example of first and second nonaqueous electrolyte secondary batteries according to the present invention, FIG. 2 is an enlarged cross-sectional view showing part A of FIG. 1, and FIG. 3 is a secondary battery of FIG. It is a schematic diagram which shows the boundary vicinity of the positive electrode in FIG., A separator, and a negative electrode.

  As shown in FIG. 1, an exterior material 1 made of, for example, a laminate film surrounds the electrode group 2. The electrode group 2 has a structure in which a laminate composed of a positive electrode, a negative electrode, and a separator is wound in a spiral shape, and the obtained wound product is compression-molded in the radial direction. 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 layer 4, a separator 3, a negative electrode layer 6, a negative electrode current collector 7, a negative electrode layer 6, a separator 3, and a positive electrode. The layer 4, the positive electrode current collector 5, the positive electrode layer 4, the separator 3, the negative electrode layer 6, and the negative electrode current collector 7 are laminated 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 between the positive electrode layer 4, the separator 3, and the negative electrode layer 6. The positive electrode and the separator 3 are bonded together by the positive electrode layer 4, the separator 3, and a polymer 9 having adhesive properties scattered at the boundary between the positive electrode layer 4 and the separator 3. On the other hand, the negative electrode and the separator 3 are bonded to each other by the negative electrode layer 6, the separator 3, and the polymer 9 having adhesive properties scattered at the boundary between the negative electrode layer 6 and the separator 3. 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 addition, in FIG. 1 described above, an example in which an electrode group having a structure in which a laminate including a plurality of positive electrodes and negative electrodes is spirally wound and then compressed in the radial direction has been described, as shown in FIG. Alternatively, an electrode group having a structure in which one positive electrode 12 and one negative electrode 13 are spirally wound through a separator 14 therebetween and then compressed in the radial direction may be used.

  Further, in FIG. 1 described above, an example in which an electrode group having a structure in which a positive electrode and a negative electrode are wound in a spiral shape through a separator therebetween and then compressed in a radial direction has been described. An electrode group having a structure bent through the electrode may be used. An example of this is shown in FIG. As shown in FIG. 5, the electrode group has a structure in which the positive electrode 12 and the negative electrode 13 are bent a plurality of times (for example, five times) so that the negative electrodes 13 are in contact with each other with a separator 14 therebetween.

  In FIG. 1 described above, the adhesive portion 8 is formed on the entire surface of the electrode group 2. However, if the nonaqueous electrolyte can be prevented from penetrating between the exterior material 1 and the electrode group 2, the electrode 8 It may be formed on a part of the surface of group 2. Especially, it is preferable to form an adhesive part at least on the outermost periphery. Further, in the case of the electrode group having the above-described bent structure, it is desirable that the adhesive portion is formed at least on the side surface.

  The first and second nonaqueous electrolyte secondary batteries according to the present invention are manufactured, for example, by the method described below.

(First step)
Between the positive electrode and the negative electrode, a porous sheet is interposed as a separator having no adhesive polymer, and an electrode group is prepared.

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

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

  Examples of the film exterior material include those described in the section of (5) exterior material described above.

  It is desirable that the polymer having adhesiveness is one that can maintain high adhesiveness while holding a nonaqueous electrolytic solution. Furthermore, it is more preferable that such a polymer has high lithium ion conductivity. Examples of the polymer having high adhesiveness while holding the non-aqueous electrolyte and having high lithium ion conductivity include the same polymers as those described above for the positive electrode. Among these, polyvinylidene fluoride 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 adhesive polymer in the solution is preferably in the range of 0.1 to 2.5% by weight. This is due to the following reason. If the concentration is less than 0.1% by weight, it may be difficult to bond the positive electrode and the separator and the negative electrode 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 0.5 to 1.5% by weight.

  The injection amount of the solution is preferably in the range of 0.2 to 2 ml per 100 mAh of battery capacity when the concentration of the adhesive polymer in the solution is 0.1 to 2.5% by weight. This is due to the following reason. If the injection amount is less than 0.2 ml, it may be difficult to sufficiently improve the adhesive strength between the positive electrode and the separator and the adhesive strength between 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 reduced and the internal resistance may be increased, which may improve the discharge capacity, large current discharge characteristics, and charge / discharge cycle life. It can be difficult. A more preferable range of the injection amount is 0.3 to 1 ml per 100 mAh of battery capacity.

(Third step)
The solvent in the solution is evaporated by drying under normal pressure or reduced pressure including vacuum while pressing the electrode group to a predetermined thickness. By this step, the polymer having adhesiveness is held in the voids of the positive electrode, the negative electrode, and the separator, and the positive electrode, the negative electrode, and the separator are integrated. In addition, a part of the adhesive polymer is scattered at the boundary between the positive electrode and the separator and the boundary between the negative electrode and the separator. In addition, the water | moisture content contained in the said electrode group can be simultaneously performed by this process.

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

  Molding can be performed by fitting into a mold instead of the press molding described above.

  The electrode group can be dried, for example, by heating under normal pressure, reduced pressure, or vacuum. Of these, vacuum heating and vacuum heating are preferable.

  The drying is preferably performed at 100 ° C. or lower. This is due to the following reason. When the drying temperature 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 contraction of the separator can be suppressed as the drying temperature becomes lower, if the drying temperature is lower than 40 ° C., it may be difficult to sufficiently evaporate the solvent. For this reason, it is more preferable that a drying temperature shall be 40-100 degreeC. A more preferable range is 60 to 90 ° 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 manufactured by sealing the opening of the exterior material.

  As the non-aqueous electrolyte, the same one as described in the first non-aqueous electrolyte secondary battery can be used.

  In the manufacturing method described above, the electrode group is housed in the exterior material, and then the solution in which the adhesive polymer is dissolved is injected. However, the solution may be injected without being accommodated in the exterior material. good. 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 solvent of the solution is evaporated by drying while forming the electrode group. 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.

  Moreover, in the manufacturing method mentioned above, drying and shaping | molding were performed simultaneously, However Drying may be performed anytime, for example, can be performed before shaping | molding or after shaping | molding.

  The concentration of the polymer having adhesiveness inside the separator is set lower than the concentration of the polymer having adhesiveness on the surface facing the positive electrode or the negative electrode. High separators can be used, or the amount of gaps present at the boundary between the positive electrode and the separator and the boundary between the negative electrode and the separator can be increased.

  A third non-aqueous electrolyte secondary battery according to the present invention includes an electrode group having a structure in which a positive electrode and a negative electrode are wound spirally through a separator therebetween and then compressed in a radial direction, and the electrode group includes A nonaqueous electrolytic solution to be impregnated; and a film exterior material in which the electrode group is accommodated. Moreover, the said electrode group has a shape where the surface where the laminated structure is exposed satisfy | fills following (1) Formula.

0.9 ≦ L ₂ / L ₁ ≦ 1.2 (1)
In the formula (1), L ₂ is the thickness of the most multilayered portion in the region excluding the curved laminated region in the surface, and L ₁ is a layer in the end portion of the region excluding the curved laminated region. The thickness of the end portion whose number is equal to L ₂ .

  An example of the third non-aqueous electrolyte secondary battery according to the present invention will be described with reference to FIGS.

  FIG. 6 is a cross-sectional view showing an example of a third nonaqueous electrolyte secondary battery according to the present invention, and FIG. 7 is an enlarged cross-sectional view showing part B of FIG.

  The film exterior material 21 surrounds the electrode group 22. The electrode group 22 has a structure in which a laminate composed of a positive electrode, a negative electrode, and a separator is spirally wound, and the obtained wound product is compressed in the radial direction. As shown in FIG. 7, the laminate includes a separator 23, a positive electrode layer 24, a positive electrode current collector 25, a positive electrode layer 24, a separator 23, a negative electrode layer 26, a negative electrode current collector 27, a negative electrode layer 26, a separator 23, and a positive electrode. The layer 24, the positive electrode current collector 25, the positive electrode layer 24, the separator 23, the negative electrode layer 26, and the negative electrode current collector 27 are laminated in this order. In the electrode group 22, the negative electrode current collector 27 is located in the outermost layer. 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 28 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-like negative electrode lead 29 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.

  The electrode group 22 has a shape in which the surface where the laminated structure is exposed (surface perpendicular to the winding axis) satisfies the following expression (1).

0.9 ≦ L ₂ / L ₁ ≦ 1.2 (1)
In the formula (1), L ₂ is the thickness of the outermost multilayer portion in the region X in which the layers are laminated substantially in parallel. The L ₁ is the thickness of the end portion of the region X where the number of layers is equal to the L ₂ . On the other hand, in the region Y located at both ends of the region X, the layer is curved. The number of layers means the total number of stacked positive electrodes, negative electrodes, and separators.

  In the secondary battery according to the present invention, the surface on which the laminated structure of the electrode group is exposed satisfies at least one of the above-described formula (1) in at least one of after assembly, after charge, and after discharge. is there. In particular, it is desirable that the surface where the laminated structure of the electrode group is exposed at least after charging satisfies the above-described formula (1).

The reason why the ratio of L ₂ / L ₁ is defined within the above range is as follows. Unlike a packaging material made of a metal can, a film packaging material has little effect of sandwiching or pressing an electrode group. For this reason, when the ratio of L ₂ / L ₁ exceeds 1.2, not only the contact between the positive electrode and the separator or the negative electrode and the separator from the initial stage of the charge / discharge cycle becomes insufficient, but also with the progress of the charge / discharge cycle. This further reduces the contact area. As a result, lithium deposition tends to occur in the negative electrode, so that a long life cannot be obtained. On the other hand, when the ratio of L ₂ / L ₁ is less than 0.9, the porosity of the electrode group is insufficient, so that the amount of nonaqueous electrolyte retained in the electrode group is reduced, and the charge / discharge cycle life can be improved. It becomes difficult. A more preferable range of the ratio L ₂ / L ₁ is 0.95 to 1.1.

  As the non-aqueous electrolyte and the film exterior material, the same materials as those described for the first non-aqueous electrolyte secondary battery can be used.

Hereinafter, the positive electrode, the negative electrode, and the separator will be described. (1) Positive electrode The positive electrode includes a current collector and a positive electrode layer that is supported on one or both surfaces of the current collector and includes an active material and a binder. .

  Examples of the positive electrode active material include the same materials as those described above for the positive electrodes of the first and second nonaqueous electrolyte secondary batteries.

  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 one or more selected from polytetrafluoroethylene (PTFE), ethylene-propylene-diene copolymer (EPDM), styrene-butadiene rubber (SBR), and polyvinylidene fluoride (PVdF). A polymer or the like can be used.

  The binder content of the positive electrode is preferably in the range of 2 to 7% by weight.

  The positive electrode layer preferably further contains a conductive agent. Examples of the conductive agent include the same ones as described for the positive electrodes of the first and second nonaqueous electrolyte secondary batteries. The content of the conductive material of the positive electrode is preferably in the range of 3 to 20% by weight when the positive electrode active material is 80 to 95% by weight.

  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.

In particular, as the current collector, 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 are present 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, when 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 there is a possibility that a sufficient cycle life cannot 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.

  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.

(2) Negative electrode The negative electrode includes a current collector and a negative electrode layer that is supported on one or both surfaces of the current collector and includes an active material and a binder.

  Examples of the active material include the same materials as those described for the negative electrodes of the first and second nonaqueous electrolyte secondary batteries.

  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), ethylene-propylene-diene copolymer (EPDM), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVdF), and carboxymethyl cellulose (CMC). At least one polymer selected from the group consisting of can be used. When using the carbonaceous material as the active material, the content of the binder in the negative electrode is preferably in the range of 2 to 10% by weight in a state where the negative electrode is produced.

  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.

In particular, as the current collector, 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 are present 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, when 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 there is a possibility that a sufficient cycle life cannot 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.

  It is preferable that at least one end portion of the end portion of the negative electrode protrudes compared to the positive electrode. With such a configuration, current concentration at the end of the negative electrode can be relaxed, and cycle life and safety can be improved. In particular, it is desirable to project all end portions of the negative electrode from the positive electrode.

  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. Can be produced by pressing once or multistage pressing 2-5 times.

  As the negative electrode, in addition to the above-described carbonaceous material that occludes / releases lithium ions, a metal oxide, a metal sulfide, a metal nitride, or a lithium metal or lithium alloy is used. Can be used.

  Examples of the metal oxide, the metal sulfide, the metal nitride, and the lithium alloy include the same ones as described for the negative electrodes of the first and second nonaqueous electrolyte secondary batteries. .

(3) Separator As the separator, for example, a porous sheet can be used.

  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 thermal shrinkage rate exceeds 20%, it may be difficult to make sufficient contact between the positive and negative electrodes and the separator. 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. 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 still more preferably 400 seconds / 100 cm ³ . The lower limit is more preferably 150 seconds / 100 cm ³ .

  The separator allows a small amount of an adhesive polymer to be contained. The content of the adhesive polymer in the electrode group including this separator is preferably 0.1% by weight or less (including 0% by weight). When the content exceeds 0.1% by weight, the lithium ion conductivity of the separator may be lowered.

  It is preferable that at least one end of the end portion of the separator protrudes compared to the positive electrode or the negative electrode. With such a configuration, when an impact is applied to the battery by accidentally dropping the battery or when the battery is used in a high-temperature environment of 100 ° C. or higher, an internal short circuit is prevented from occurring when the separator is thermally contracted. be able to. Among them, it is desirable to project all the end portions of the separator as compared with the positive electrode or the negative electrode. In addition, when at least one end of the positive electrode protrudes compared to the negative electrode, or when at least one end of the negative electrode protrudes compared to the positive electrode, the end of the separator protrudes compared to the protruding electrode end. It is desirable. In particular, it is preferable that at least one end of the negative electrode protrudes compared to the positive electrode, and the end of the separator protrudes compared to the protruding negative electrode end.

  When projecting at least one end of the end portion of the separator as compared with the positive electrode or the negative electrode, the projecting length is preferably in the range of 0.25 to 2 mm. This is due to the following reason. If the protruding length is shorter than 0.25 mm, it may be difficult to reduce the internal short-circuit occurrence rate. On the other hand, if the protruding length exceeds 2 mm, the volume energy density of the battery may be reduced. A more preferable range is 0.5 to 1.5 mm. However, when at least one end of the positive electrode protrudes compared to the negative electrode, or when at least one end of the negative electrode protrudes compared to the positive electrode, the protruding length is set based on the protruding electrode end. .

  In FIG. 6 described above, the winding end end of the electrode group 22 is disposed at the end of the region X, but the position of the winding end end of the electrode group 22 may be anywhere. For example, the winding end end can be arranged near the center of the region X, or can be arranged in the curved laminated region Y.

  In addition, in FIG. 6 described above, the electrode group was configured using a plurality of positive electrodes and a plurality of negative electrodes, but after winding one positive electrode and one negative electrode in a spiral through a separator therebetween, The present invention can be applied to an electrode group having a structure compressed in the radial direction.

  A fourth non-aqueous electrolyte secondary battery according to the present invention includes an electrode group having a structure in which a positive electrode and a negative electrode are folded twice or more via a separator, a non-aqueous electrolyte solution impregnated in the electrode group, A film exterior material in which the electrode group is accommodated. Further, the electrode group has a shape in which a surface where the laminated structure is exposed satisfies the following formula (2): A nonaqueous electrolyte secondary battery.

0.9 ≦ L ₄ / L ₃ ≦ 1.2 (2)
In the formula (2), L ₄ is the thickness of the outermost multilayer portion in the region excluding the folded laminated region, and L ₃ is the layer in the end portion of the region excluding the folded laminated region. The thickness of the end portion whose number is equal to the L ₄ .

  An example of the fourth non-aqueous electrolyte secondary battery according to the present invention will be described with reference to FIGS.

  FIG. 8 is a cross-sectional view showing an example of a fourth non-aqueous electrolyte secondary battery according to the present invention, and FIG. 9 is an enlarged cross-sectional view showing part C of FIG.

  The film exterior material 31 surrounds the electrode group 32. The electrode group 32 includes a strip-like laminate in which a separator 33, a positive electrode current collector 34, a positive electrode layer 35, a separator 33, a negative electrode layer 36, and a negative electrode current collector 37 as shown in FIG. It is produced by bending 6 times so that the electric bodies 37 are in contact with each other. The non-aqueous electrolyte is impregnated in the electrode group 32 in the exterior material 31. One end of the strip-like positive electrode lead 38 is connected to the positive electrode current collector 34 of the electrode group 32, and the other end is extended from the exterior member 31. On the other hand, one end of the strip-like negative electrode lead 39 is connected to the negative electrode current collector 37 of the electrode group 32, and the other end is extended from the exterior member 31.

  The electrode group 32 has a shape in which the surface where the laminated structure is exposed satisfies the following expression (2).

0.9 ≦ L ₄ / L ₃ ≦ 1.2 (2)
In the equation (2), L ₄ is the height of the most multilayered portion of the region X ₁ between an arbitrary turning point P ₁ and the next turning point P ₂ on the surface, and L ₃ is Of the thicknesses passing through the folding point P ₁ and the folding point P ₂ , the thickness is equal to the number of layers equal to L ₄ . The folding point refers to a point at which the laminates start to overlap each other when the strip-like laminate composed of the positive electrode, the negative electrode, and the separator is folded. Further, the folding point P ₁ and the folding point P ₂ are selected so that the region X ₁ does not include the folded laminated region Y ₁ . On the other hand, the number of layers means the total number of stacked positive electrodes, negative electrodes, and separators.

  In the secondary battery according to the present invention, the laminated surface of the electrode group satisfies the above-described formula (2) in at least one of after assembly, after charge, and after discharge. In particular, it is desirable that the laminated surface of the electrode group satisfies the above-described formula (2) at least after charging.

The reason why the ratio of L ₄ / L ₃ is defined in the above range is as follows. Unlike a packaging material made of a metal can, a film packaging material has little effect of sandwiching or pressing an electrode group. For this reason, when the ratio of L ₄ / L ₃ exceeds 1.2, not only the contact between the positive electrode and the separator or the negative electrode and the separator from the initial stage of the charge / discharge cycle becomes insufficient, but also with the progress of the charge / discharge cycle. This further reduces the contact area. As a result, lithium deposition tends to occur in the negative electrode, so that a long life cannot be obtained. On the other hand, when the ratio of L ₄ / L ₃ is less than 0.9, the porosity of the electrode group is insufficient, so the amount of nonaqueous electrolyte retained in the electrode group is reduced, and the charge / discharge cycle life can be improved. It becomes difficult. A more preferable range of the ratio of L ₄ / L ₃ is 0.95 to 1.1.

  As the positive electrode, the negative electrode, the separator, the non-aqueous electrolyte, and the film exterior material, the same materials as those described in the third non-aqueous electrolyte secondary battery can be used.

In addition, in FIG. 8 mentioned above, although the both ends of the strip | belt-shaped laminated body which consists of a positive electrode, a negative electrode, and a separator demonstrated the example which overlaps the bending part of an electrode group, the position of the both ends of the said strip | belt-shaped laminated body is not specifically limited. For example, it is possible to overlap the ends of the strip laminate in the region X ₁ of the electrode group. Further, the two end portions of the belt-like laminate may be at different positions.

  In FIG. 8 described above, an electrode group is formed by bending a single positive electrode and a single negative electrode through a separator between the negative electrode so that the negative electrodes are in contact with each other. The electrode group may be configured by laminating in order and bending the resulting laminate multiple times so that the separator contacts.

  The third and fourth nonaqueous electrolyte secondary batteries are manufactured, for example, by the method described below.

(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.

  As the positive electrode, the negative electrode, and the separator, the same materials as those described in the third non-aqueous electrolyte secondary battery can be used.

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

  As the exterior material, the same material as described in the third non-aqueous electrolyte secondary battery can be used.

(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. In the electrode group, the positive electrode and the negative electrode are in direct contact with the separator, and the polymer having adhesiveness is hardly contained in the separator. When this electrode group is molded at room temperature, springback occurs after molding, that is, a gap is formed between the positive electrode and the separator and between the negative electrode and the separator. As a result, the ratio of L ₂ / L ₁ ratio and L ₄ / L ₃ is greater than 1.2. 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 ratio of L ₂ / L _{1 and} the ratio of L ₄ / L ₃ can be 1.2 or less. 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 pressing pressure is preferably in the range of 0.01 to 20 kg / cm ² . This is due to the following reason. When the pressing pressure is lower than 0.01 kg / cm ² , the ratio L ₂ / L _{1 and} the ratio L ₄ / L ₃ are higher than 1.2. On the other hand, when the press pressure is higher than 20 kg / cm ² , the ratio L ₂ / L _{1 and} the ratio L ₄ / L ₃ are smaller than 0.9.

(4th process)
After injecting the nonaqueous electrolyte into the electrode group in the exterior material, the third and fourth nonaqueous electrolyte secondary batteries described above are obtained 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 a film exterior material, the above-described third and fourth non-aqueous electrolyte secondary batteries can be manufactured by injecting a non-aqueous electrolyte and performing sealing or the like. .

  Moreover, after producing an electrode group by laminating a positive electrode and a negative electrode through a separator between them, the electrode group was heated and molded along the laminating direction, and the obtained electrode group and non-aqueous electrolysis By storing the liquid in an exterior material and assembling the non-aqueous electrolyte secondary battery, the positive electrode, the negative electrode, and the separator can be kept in sufficient contact over a long period of time, resulting in high current discharge characteristics and cycle characteristics. An excellent nonaqueous electrolyte secondary battery can be realized. In such a method, excellent characteristics can be obtained even when the heating temperature of the electrode group is 40 ° C. or lower.

  A fifth non-aqueous electrolyte secondary battery according to the present invention includes an electrode group having a structure in which a positive electrode and a negative electrode are spirally wound through a separator therebetween and then compressed in a radial direction, and the electrode group includes A nonaqueous electrolytic solution to be impregnated; and a film exterior material in which the electrode group is accommodated. The positive electrode and the separator are bonded by an adhesive polymer scattered in the inside and boundary thereof, and the negative electrode and the separator are bonded by an adhesive polymer scattered in the interior and boundary thereof. Has been. Further, the electrode group has a shape in which the surface where the laminated structure is exposed satisfies the above-described formula (1).

  As the positive electrode, the negative electrode, the separator, the nonaqueous electrolyte, and the film exterior material, the same materials as those described in the first and second nonaqueous electrolyte secondary batteries can be used. .

  A sixth nonaqueous electrolyte secondary battery according to the present invention includes an electrode group having a structure in which a laminate composed of a positive electrode, a negative electrode, and a separator is folded twice or more, and a nonaqueous electrolyte solution impregnated in the electrode group. And a film exterior material in which the electrode group is accommodated. The positive electrode and the separator are bonded by an adhesive polymer scattered in the inside and boundary thereof, and the negative electrode and the separator are bonded by an adhesive polymer scattered in the interior and boundary thereof. Has been. In the electrode group, the surface where the laminated structure is exposed has a shape satisfying the above-described formula (2).

  As the positive electrode, the negative electrode, the separator, the nonaqueous electrolyte, and the film exterior material, the same materials as those described in the first and second nonaqueous electrolyte secondary batteries can be used. .

  The fifth and sixth nonaqueous electrolyte secondary batteries are manufactured by the method described below.

(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.

  The positive electrode, the negative electrode, and the separator are the same as those described in the method for manufacturing a non-aqueous electrolyte secondary battery described above.

  In the electrode group produced by such a method, in the second step to be described later, while preventing the polymer solution having adhesiveness from penetrating the boundary between the positive electrode and the separator and the entire boundary between the negative electrode and the separator, The solution can be infiltrated into the positive electrode, the negative electrode, and the separator. 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.

(Second step)
The electrode group is housed in a bag-shaped film exterior material. At this time, it is desirable that the laminated surface of the electrode group is visible from the opening of the exterior material. A solution obtained by dissolving a polymer having adhesiveness in a solvent is injected into the electrode group in the exterior material, and the electrode group is impregnated with the solution.

  As the film-made packaging material, the adhesive polymer, and the solvent, the same materials as described in the method for producing a non-aqueous electrolyte secondary battery described above can be used.

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

This process, the ratio of L ₂ / L ₁ ratio and L ₄ / L ₃ is 0.9 to 1.2. In addition, the positive electrode, the negative electrode, and the separator are bonded, and the electrode group is bonded to the inner surface of the exterior material. Furthermore, since the solvent in the solution evaporates, a part or all of the adhesive polymer contained in the electrode group has a porous structure. Further, moisture contained in the electrode group is removed.

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

  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. In the electrode group, polymers having adhesive properties are scattered at the boundary between the positive electrode and the separator and the boundary between the negative electrode and the separator. When this electrode group is molded at room temperature, springback occurs after molding, that is, a gap is formed between the positive electrode and the separator and between the negative electrode and the separator. As a result, the ratio of L ₂ / L ₁ ratio and L ₄ / L ₃ is greater than 1.2. By forming the electrode group at 40 ° C. or higher, the binder and the polymer having adhesiveness 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 ratio of L ₂ / L _{1 and} the ratio of L ₄ / L ₃ can be 1.2 or less. 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 pressing pressure is preferably in the range of 0.01 to 20 kg / cm ² . This is due to the following reason. When the pressing pressure is lower than 0.01 kg / cm ² , the ratio L ₂ / L _{1 and} the ratio L ₄ / L ₃ are higher than 1.2. On the other hand, when the press pressure is higher than 20 kg / cm ² , the ratio L ₂ / L _{1 and} the ratio L ₄ / L ₃ are smaller than 0.9.

(4th process)
After injecting a nonaqueous electrolyte into the electrode group in the exterior material, fifth and sixth nonaqueous electrolyte secondary batteries are manufactured 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 the solution in which the adhesive polymer is dissolved is injected. However, the solution may be injected without being accommodated in the exterior material. good. 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 molded while being heated to 40 to 120 ° C. to evaporate the solvent of the solution. After accommodating such an electrode group in an exterior material, the 5th and 6th nonaqueous electrolyte secondary battery can be manufactured by injecting a nonaqueous electrolyte and performing sealing or the like.

  A seventh non-aqueous electrolyte secondary battery according to the present invention includes at least one positive electrode, at least one negative electrode, at least one separator, between the positive electrode and the separator, and between the negative electrode and the separator. An electrode group having a structure in which at least two adhesive layers interposed between each of the electrode groups are laminated; a nonaqueous electrolytic solution impregnated in the electrode group; a film exterior material in which the electrode group is housed; It has.

  The separator includes 10% by weight or less of an adhesive polymer. Moreover, all the edge parts of the said separator protrude compared with the edge part of the said positive electrode, or the edge part of the said negative electrode.

  As the positive electrode, the negative electrode, the non-aqueous electrolyte, and the film exterior material, the same materials as those described in the third non-aqueous electrolyte secondary battery can be used. Hereinafter, the separator and the adhesive layer will be described.

(1) Separator The separator is made of a porous sheet in which an adhesive polymer is held. The separator has an adhesive polymer content of 10% by weight or less (including 0% by weight). Moreover, all the edge parts of the said separator protrude compared with the edge part of the said positive electrode, or the edge part of the said negative electrode.

  As the porous sheet, the same sheet as described in the separators of the first and second non-aqueous electrolyte secondary batteries can be used.

  As the polymer having adhesiveness, the same polymer as described in the separators of the first and second nonaqueous electrolyte secondary batteries described above can be used.

The reason why the content of the polymer having adhesiveness in the separator is defined in the above range is as follows. When the content is more than 10% by weight, the internal resistance of the secondary battery is increased, so that it is difficult to improve the cycle life. A more preferred range is 5% by weight or less, and a further preferred range is 1% by weight or less. Further, by setting the content of the adhesive polymer to 1 × 10 ⁻⁵ wt% or more, the adhesive strength between the positive electrode and the separator and the adhesive strength between the negative electrode and the separator can be improved. A more preferable lower limit of the content is 1 × 10 ⁻⁴ wt%, and a more preferable range is 1 × 10 ⁻³ wt%.

  In the separator, the adhesive polymer may be uniformly present, but the concentration of the adhesive polymer may be uneven. In particular, it is desirable that the concentration of the polymer having adhesiveness is lower than the concentration of the polymer having adhesiveness on the surface facing the positive electrode or the negative electrode. In particular, it is preferable that the concentration of the polymer having adhesiveness at the central portion in the thickness direction of the separator is lower than the concentration of the polymer having adhesiveness on the surface facing the positive electrode or the negative electrode.

  When at least one end of the positive electrode protrudes compared to the negative electrode, or when at least one end of the negative electrode protrudes compared to the positive electrode, all the end portions of the separator are protruded compared to the protruding electrode. It is desirable. With such a configuration, the internal short-circuit occurrence rate can be further reduced. In particular, it is preferable that at least one end portion of the negative electrode protrudes compared to the positive electrode, and all end portions of the separator protrude from the negative electrode. With such a configuration, it is possible to further reduce the internal short-circuit occurrence rate and further improve the cycle life.

  It is preferable that the adhesive polymer is held at the end of the separator. With such a configuration, the strength of the protruding separator end can be increased, so that the internal short-circuit occurrence rate can be further reduced.

  The protruding length of the end of the separator is preferably in the range of 0.25 to 2 mm. This is due to the following reason. If the protruding length is shorter than 0.25 mm, it may be difficult to reduce the internal short-circuit occurrence rate. On the other hand, if the protruding length exceeds 2 mm, the volume energy density of the battery may be reduced. A more preferable range is 0.5 to 1.5 mm. However, when at least one end of the positive electrode protrudes compared to the negative electrode, or when at least one end of the negative electrode protrudes compared to the positive electrode, the protruding length is set based on the protruding electrode end. .

(2) Adhesive layer This adhesive layer contains a polymer having adhesiveness. Examples of the adhesive polymer include the same polymers as those described for the positive electrodes of the first and second nonaqueous electrolyte secondary batteries.

  The adhesive layer preferably has a porous structure. The adhesive layer having a porous structure can increase the amount of the non-aqueous electrolyte retained in the electrode group.

  Hereinafter, a thin lithium ion secondary battery which is an example of the seventh nonaqueous electrolyte secondary battery according to the present invention will be described in detail with reference to FIGS.

  A laminated structure type electrode group 42 is accommodated in the film exterior material 41. The electrode group 42 includes a positive electrode 45 having a structure in which a positive electrode layer 44 is supported on a current collector 43 made of, for example, a porous conductive substrate, and a negative electrode layer 47 on a current collector 46 made of, for example, a porous conductive substrate. A negative electrode 48 having a supported structure, porous adhesive layers 49a and 49b bonded to the positive electrode layer 44 and the negative electrode layer 47, respectively, and the porous adhesive layers 49a and 49b are bonded to both surfaces. And a separator 50. All the end portions of the negative electrode 48 protrude as compared with the positive electrode 45. On the other hand, the separator 50 includes an adhesive polymer of 10 wt% or less (including 0 wt%), and all the end portions thereof protrude from the negative electrode 48. The nonaqueous electrolytic solution is accommodated in the exterior material 41. The positive electrode terminal 51 has one end connected to the positive electrode 45 and the other end extended from the exterior material 41. On the other hand, one end of the negative electrode terminal 52 is connected to the negative electrode 48 and the other end is extended from the exterior material 41.

According to the first non-aqueous electrolyte secondary battery according to the present invention described above, an adhesive polymer is surrounded by at least a gap surrounded by a positive electrode and a separator, a gap surrounded by a negative electrode and a separator, a positive and negative electrode, Since it can hold | maintain with each space | gap in a separator, adhesive polymer can be distributed in a three-dimensional network shape at least inside the electrode group. As a result, the positive electrode, the negative electrode, and the separator can be integrated while the positive electrode is in direct contact with one surface of the separator and the negative electrode is in direct contact with the other surface. In addition, sufficient adhesion between the positive and negative electrodes and the separator can be secured, and an increase in internal resistance due to the adhesive polymer can be suppressed. Furthermore, when the separator includes a porous sheet having an air permeability of 600 seconds / 100 cm ³ or less, at least a polymer having adhesiveness is retained, the lithium ion conductivity of the separator can be increased. it can. As a result, a nonaqueous electrolyte secondary battery with improved capacity, large current characteristics, and cycle life can be provided. Moreover, since a film-like exterior material can be used, a thin non-aqueous electrolyte secondary battery having a thickness as thin as 4 mm or less and excellent in capacity, large current characteristics and cycle life can be realized. .

  When using the film-shaped exterior material, the exterior material can be fixed to the electrode group by forming an adhesive layer on at least a part of the surface of the electrode group. As a result, it is possible to prevent the nonaqueous electrolyte from penetrating between the exterior material and the electrode group.

  By making the total amount of the polymer having adhesiveness in the range of 0.2 to 6 mg per 100 mAh of battery capacity, it is possible to further improve the adhesion between the positive electrode, the negative electrode and the separator while keeping the internal resistance low. As a result, the large current characteristics and cycle life of the secondary battery can be further improved.

  By setting the thickness of the separator to 30 μm or less, the internal resistance of the secondary battery can be further reduced, so that the large current characteristics and cycle life of the secondary battery can be further improved.

  Moreover, since the adhesiveness of a positive electrode, a negative electrode, and a separator can be improved more by making the thermal contraction rate in 120 degreeC and 1 hour of the said separator into 20% or less, the large current characteristic of the said secondary battery and The cycle life can be further improved.

  In addition, by setting the porosity of the separator to 30 to 60%, it is possible to satisfy both the strength of the separator and the electrolyte solution retainability, thereby further improving the large current characteristics and cycle life of the secondary battery. be able to.

  In addition, by using a negative electrode made of lithium metal or a lithium alloy as the negative electrode, a lithium dendride that tends to occur in a thin non-aqueous electrolyte secondary battery having a negative electrode made of lithium metal or a lithium alloy is used. The problem can be avoided.

Further, as the carbonaceous material, it is possible to further improve the result, the capacity and the large current characteristics of the secondary battery using those having a graphite crystal is not more than 0.340nm is plane spacing d ₀₀₂ of (002) plane .

Further, in at least one of the positive electrode and the negative electrode, a conductive substrate having a 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 is used as a current collector. Since the non-aqueous electrolyte can be uniformly infiltrated into the electrode group while ensuring the necessary electrode strength, the cycle life of the secondary battery can be further improved.

  The second non-aqueous electrolyte secondary battery according to the present invention includes an electrode group having a positive electrode, a negative electrode, and a separator for isolating the positive electrode and the negative electrode; an exterior material for housing the electrode group; A nonaqueous electrolytic solution impregnated in the electrode group. The positive electrode and the separator are bonded by a polymer having adhesiveness scattered in the inside and the boundary thereof, and the negative electrode and the separator have high adhesiveness scattered in the interior and the boundary thereof. Bonded by molecules. According to such a secondary battery, since a part of the positive electrode and a part of the negative electrode can be directly brought into contact with the separator, the internal resistance caused by the adhesive polymer can be reduced, and the positive electrode and The adhesive strength of the separator and the adhesive strength between the negative electrode and the separator can be improved. The reason why the adhesive strength is improved is presumed that the polymer having adhesiveness is distributed in a three-dimensional network inside the electrode group. As a result, a nonaqueous electrolyte secondary battery with improved capacity, large current characteristics, and cycle life can be provided. Moreover, the said electrode group can maintain the state to which the positive electrode, the negative electrode, and the separator were fully adhere | attached for a long period, when using a film-made exterior material. Therefore, a thin non-aqueous electrolyte secondary battery having a thin thickness of, for example, 4 mm or less and excellent capacity, large current characteristics, and cycle life can be realized.

  In the secondary battery according to the present invention, the adhesive strength between the positive electrode and the separator and the adhesive strength between the negative electrode and the separator are increased by setting the content of the polymer having adhesiveness of the separator to 10% by weight or less. Since the ionic conductivity of the non-aqueous electrolyte can be increased while maintaining it, the large current discharge characteristics and the cycle life can be further improved.

  In the secondary battery according to the present invention, the concentration of the polymer having adhesiveness inside the separator is made lower than the concentration of the polymer having adhesiveness on the surface facing the positive electrode or the negative electrode, thereby allowing the positive electrode and the separator to Since the internal resistance can be reduced while maintaining the adhesive strength between and the negative electrode and the separator at a high value, the large current discharge characteristics and the cycle life can be further improved.

  In the secondary battery according to the present invention, the total amount of the polymer having adhesiveness is in the range of 0.2 to 6 mg per 100 mAh of battery capacity, so that the internal resistance is kept low and the adhesive strength between the positive electrode and the separator is reduced. The adhesive strength between the negative electrode and the separator can be further improved. As a result, the large current characteristics and cycle life of the secondary battery can be further improved.

  In the secondary battery according to the present invention, when the total amount of the polymer having adhesiveness is in the range of 0.2 to 6 mg per 100 mAh of battery capacity, the amount of the non-aqueous electrolyte solution is 0.2 to 0.2 per 100 mAh of battery capacity. By making it 0.6 g, in addition to improving the large current characteristics and cycle life, it becomes possible to use a film exterior material, so that the thickness can be reduced.

  In the secondary battery according to the present invention, when a film-made outer packaging material is used, the electrode group is bonded to the inner surface of the film-made outer packaging material with an adhesive layer formed on at least a part of the surface of the electrode group. Thus, the exterior material can be fixed to the electrode group. As a result, it is possible to prevent the nonaqueous electrolyte from penetrating between the exterior material and the electrode group.

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 and a polymer having at least the adhesive property held therein. Lithium ion conductivity can be increased. As a result, the discharge capacity, large current characteristics, and charge / discharge cycle life can be further improved.

  By setting the thickness of the separator to 30 μm or less, the internal resistance of the secondary battery can be further reduced, so that the large current characteristics and cycle life of the secondary battery can be further improved.

  In addition, since the thermal shrinkage rate at 120 ° C. for 1 hour of the separator is 20% or less, the adhesive strength between the positive electrode and the separator and the adhesive strength between the negative electrode and the separator can be further improved. The large current characteristics and cycle life of the secondary battery can be further improved.

  In addition, by setting the porosity of the separator to 30 to 60%, it is possible to satisfy both the strength of the separator and the electrolyte solution retainability, thereby further improving the large current characteristics and cycle life of the secondary battery. be able to.

  In addition, by using a negative electrode made of lithium metal or a lithium alloy as the negative electrode, a lithium dendride that tends to occur in a thin non-aqueous electrolyte secondary battery having a negative electrode made of lithium metal or a lithium alloy is used. The problem can be avoided.

Further, as the carbonaceous material, it is possible to further improve the result, the capacity and the large current characteristics of the secondary battery using those having a graphite crystal is not more than 0.340nm is plane spacing d ₀₀₂ of (002) plane .

Further, in at least one of the positive electrode and the negative electrode, a conductive substrate having a 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 is used as a current collector. Since the non-aqueous electrolyte can be uniformly infiltrated into the electrode group while ensuring the necessary electrode strength, the cycle life of the secondary battery can be further improved.

  According to the method for manufacturing a non-aqueous electrolyte secondary battery according to the present invention, an electrode group produced by interposing a separator between a positive electrode and a negative electrode is impregnated with a solution in which an adhesive polymer is dissolved. Then, by forming the electrode group, the positive electrode, the negative electrode, and the separator can be bonded with high strength while suppressing internal resistance caused by the adhesive polymer. Next, the electrode group is impregnated with a non-aqueous electrolyte and stored in a desired exterior material, so that the non-aqueous electrolyte having excellent energy density, large current characteristics and cycle life can be obtained even when it is made thin. The secondary battery can be easily manufactured.

  In the manufacturing method according to the present invention, by injecting a polymer solution having adhesiveness in a state where the electrode group is housed in a film exterior material, the effects of reducing internal resistance and improving adhesive strength can be obtained. The electrode group can be adhered to the inner surface of the film exterior material, and the exterior material can be fixed to the electrode group. As a result, it is possible to suppress the nonaqueous electrolyte from penetrating between the electrode group and the exterior material.

  In the manufacturing method according to the present invention, when the electrode group impregnated with the solution in which the adhesive polymer is dissolved is dried, the solvent in the solution is evaporated, and the adhesive portion made of the adhesive polymer is formed. In this way, a part or all of the bonded portion has a porous structure. Since this adhesion part can hold | maintain a non-aqueous electrolyte in the space | gap, it can contribute to conduction of lithium ion. As a result, since the lithium ion conductivity of the secondary battery can be improved, the discharge capacity, large current discharge characteristics, and cycle life of the secondary battery can be improved.

  In the production method according to the present invention, the thermal shrinkage of the separator, particularly a separator containing polyethylene or polypropylene, can be suppressed by setting the drying temperature to 100 ° C. or lower. As a result, since the adhesive strength of the positive electrode, the negative electrode, and the separator can be further improved, the large current characteristics and cycle life of the secondary battery can be further improved.

  In addition, when the drying is performed at 100 ° C. or lower, the evaporation rate of the solvent can be improved by using an organic solvent having a boiling point of 200 ° C. or lower as the solvent. The adhesive strength between the positive and negative electrodes and the separator can be further increased.

  Further, when the drying is performed at 100 ° C. or lower, the thermal shrinkage rate of the separator at 120 ° C. for 1 hour is set to 20% or less, so that the thermal contraction of the separator can be further reduced. In addition, the adhesive strength of the separator can be further increased.

  A third non-aqueous electrolyte secondary battery according to the present invention includes an electrode group having a structure in which a positive electrode and a negative electrode are wound spirally through a separator therebetween and then compressed in a radial direction, and the electrode group includes A nonaqueous electrolytic solution to be impregnated; and a film exterior material in which the electrode group is accommodated. Further, the electrode group has a shape in which the surface where the laminated structure is exposed satisfies the above-described formula (1).

  That is, the electrode group of the non-aqueous electrolyte secondary battery repeatedly expands and contracts along the stacking direction as the charge / discharge cycle proceeds. The film exterior material has a small effect of suppressing the expansion / contraction, and deforms substantially following the expansion / contraction of the electrode group. On the other hand, a separator that does not contain an adhesive polymer can increase the ionic conductivity of the non-aqueous electrolyte. However, when a film exterior material is used as an exterior material of an electrode group including a separator that does not contain a polymer having adhesiveness, the contact area of the positive electrode, the negative electrode, and the separator decreases with the progress of the charge / discharge cycle, and the internal Resistance increases and long life cannot be obtained.

  According to the present invention, when the film exterior material is used, the positive electrode, the separator not containing the adhesive polymer, and the negative electrode can be sufficiently brought into contact with each other for a long period of time. As a result, since the increase in internal impedance accompanying the progress of the charge / discharge cycle can be suppressed, the charge / discharge cycle life can be improved. In addition, the secondary battery can improve the capacity recovery rate after high temperature storage. Furthermore, since a long life can be ensured even if the thickness of the film exterior material is in the range of 50 to 300 μm, a thin and long-life nonaqueous electrolyte secondary battery can be provided.

In the third nonaqueous electrolyte secondary battery according to the present invention, when the separator is a porous sheet having an air permeability of 600 seconds / 100 cm ³ or less, the lithium ion conductivity of the separator can be increased. it can. As a result, the discharge capacity and the charge / discharge cycle life can be further improved.

  In the third non-aqueous electrolyte secondary battery according to the present invention, the separator is made of at least one material selected from polyolefin and cellulose, whereby the internal resistance of the separator can be reduced, and the separator The lithium ion conductivity of can be further improved. As a result, the discharge capacity and charge / discharge cycle life of the secondary battery can be further improved.

  A fourth non-aqueous electrolyte secondary battery according to the present invention includes an electrode group having a structure in which a positive electrode and a negative electrode are bent at least twice via a separator, and a non-aqueous electrolyte solution impregnated in the electrode group And a film exterior material in which the electrode group is accommodated. The electrode group has a shape in which the surface where the laminated structure is exposed satisfies the formula (2).

  According to such a secondary battery, in the electrode group housed in the film exterior material, the positive electrode, the separator not containing the adhesive polymer, and the negative electrode are kept in sufficient contact over a long period of time. Can do. As a result, since the increase in internal impedance accompanying the progress of the charge / discharge cycle can be suppressed, the charge / discharge cycle life can be improved. In addition, the secondary battery can improve the capacity recovery rate after high temperature storage. Furthermore, since a long life can be ensured even if the thickness of the film exterior material is in the range of 50 to 300 μm, a thin and long-life nonaqueous electrolyte secondary battery can be provided.

In the fourth nonaqueous electrolyte secondary battery according to the present invention, when the separator is a porous sheet having an air permeability of 600 seconds / 100 cm ³ or less, the lithium ion conductivity of the separator can be increased. it can. As a result, the discharge capacity and the charge / discharge cycle life can be further improved.

  In the fourth non-aqueous electrolyte secondary battery according to the present invention, the separator is made of at least one material selected from polyolefin and cellulose, whereby the internal resistance of the separator can be reduced, and the separator The lithium ion conductivity of can be further improved. As a result, the discharge capacity and charge / discharge cycle life of the secondary battery can be further improved.

  Another method for producing a non-aqueous electrolyte secondary battery according to the present invention includes a step of producing an electrode group by interposing a separator made of at least one material selected from polyolefin and cellulose between a positive electrode and a negative electrode; Forming the electrode group while heating, and impregnating the electrode group with a non-aqueous electrolyte. According to such a method, since the binder contained in the positive electrode and the negative electrode can be thermally cured in the thermoforming step, the thickness of the positive electrode, the negative electrode, and the separator after molding is the thickness before molding. You can avoid trying to restore. As a result, the positive electrode, the negative electrode, and the separator can be sufficiently in contact with each other, and the state can be maintained even if the electrode group is repeatedly expanded and contracted as the charge / discharge cycle progresses. it can. As a result, it is possible to suppress an increase in internal resistance as the charge / discharge cycle progresses, so that the charge / discharge cycle life can be improved. In addition, when a film exterior material is used, a state in which the positive electrode, the negative electrode, and the separator are sufficiently in contact with each other can be maintained for a long period of time, thereby realizing a long-life thin non-aqueous electrolyte secondary battery. be able to. .

  In the manufacturing method according to the present invention, when forming the electrode group, the temperature of the electrode group is set to 40 to 120 ° C., thereby avoiding significant thermal shrinkage of the separator, and the contact state of the positive electrode, the negative electrode, and the separator. Therefore, the cycle life can be further improved.

  According to the fifth non-aqueous electrolyte secondary battery of the present invention, the electrode group having a structure in which the positive electrode and the negative electrode are spirally wound through a separator therebetween and then compressed in the radial direction, and the electrode A nonaqueous electrolytic solution impregnated in the group, and a film exterior material in which the electrode group is accommodated. The positive electrode and the separator are bonded by a polymer having adhesiveness scattered in the inside and the boundary thereof, and the negative electrode and the separator have high adhesiveness scattered in the interior and the boundary thereof. Bonded by molecules. Further, the electrode group has a shape in which the surface where the laminated structure is exposed satisfies the above-described formula (1).

  According to such a secondary battery, the positive electrode, the negative electrode, and the separator can be sufficiently brought into contact with each other for a long time while maintaining the internal resistance of the electrode group at a low value. As a result, the initial capacity, cycle life and large current discharge characteristics of the secondary battery can be dramatically improved.

  According to the sixth nonaqueous electrolyte secondary battery of the present invention, an electrode group having a structure in which a laminate composed of a positive electrode, a negative electrode, and a separator is folded twice or more, and nonaqueous electrolysis impregnated in the electrode group A liquid and a film exterior material in which the electrode group is accommodated. The positive electrode and the separator are bonded by a polymer having adhesiveness scattered in the inside and the boundary thereof, and the negative electrode and the separator have high adhesiveness scattered in the interior and the boundary thereof. Bonded by molecules. In the electrode group, the surface where the laminated structure is exposed has a shape satisfying the above-described formula (2).

  According to such a secondary battery, the positive electrode, the negative electrode, and the separator can be sufficiently brought into contact with each other for a long time while maintaining the internal resistance of the electrode group at a low value. As a result, the initial capacity, cycle life and large current discharge characteristics of the secondary battery can be dramatically improved.

  A seventh non-aqueous electrolyte secondary battery according to the present invention includes at least one positive electrode, at least one negative electrode, at least one separator, between the positive electrode and the separator, and between the negative electrode and the separator. An electrode group having a structure in which at least two adhesive layers interposed between each of the electrode groups are laminated; a nonaqueous electrolytic solution impregnated in the electrode group; a film exterior material in which the electrode group is housed; It has. The separator includes 10% by weight or less (including 0% by weight) of a polymer having adhesiveness, and an end portion of the separator protrudes from an end portion of the positive electrode or an end portion of the negative electrode.

  According to such a secondary battery, it is possible to suppress the occurrence of an internal short circuit when an impact is applied to the battery by accidentally dropping it or when the separator is thermally contracted when used in a high temperature environment. be able to. Moreover, since internal resistance can be reduced, the charge / discharge cycle life can be improved.

  The secondary battery which concerns on this invention WHEREIN: By making the protrusion length of the said separator into the range of 0.25-2 mm, an internal short circuit incidence rate can be reduced more, maintaining a high volume energy density.

  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, Two positive electrodes having a structure in which the electrode density was 3 g / cm ³ and the positive electrode layer was supported on both surfaces of the current collector were 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 One side of a current collector made of a porous copper foil (thickness: 15 μm) in which pores having a diameter of 0.5 mm are mixed at a ratio of 10 per 10 cm ² with 7% by weight of polyvinylidene fluoride (PVdF) The negative electrode A having a structure in which the electrode density was 1.3 g / cm ³ and the negative electrode layer was supported on one side of the current collector was prepared by applying to the substrate, drying, and pressing. Moreover, the negative electrode B having a structure in which the above-described mixture is applied to both sides of the current collector, dried, and pressed to have an electrode density of 1.3 g / cm ³ and a negative electrode layer supported on both sides of the current collector. Was made.

<Separator>
Four separators made of a polyethylene porous film having a thickness of 25 μm, a thermal shrinkage of 20% at 120 ° C. for 1 hour, and a porosity of 50% were prepared.

<Preparation of non-aqueous electrolyte>
A non-aqueous electrolyte was prepared by dissolving 1 mol / l of lithium hexafluorophosphate (LiPF ₆ ) in a mixed solvent of ethylene carbonate (EC) and methyl ethyl carbonate (MEC) (mixing volume ratio 1: 2).

<Production of electrode group>
The obtained positive electrode, negative electrode A, B, and separator were separated into separator, positive electrode, separator, negative electrode B (negative electrode layer, negative electrode current collector, negative electrode layer), separator, positive electrode, separator, and negative electrode A (negative electrode layer, negative electrode current collector). Body) and the obtained laminate was wound in a spiral shape, and then formed into a flat shape to produce an electrode group. Before lamination, 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.

  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 could be seen from the opening of the bag. Polyacrylonitrile (PAN), which is an adhesive polymer, was dissolved in 0.5% 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 100 mAh of battery capacity was 0.25 ml, the solution was infiltrated into the electrode group, and the entire surface of the electrode group was introduced. 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 PAN was 1.25 mg per 100 mAh battery capacity. In addition, the total amount of the adhesive polymer (for example, PAN) was calculated from the amount of weight increase when compared with the electrode group before impregnating the adhesive polymer solution.

  The non-aqueous electrolyte is injected into the electrode group in the laminate film so that the amount per battery capacity 1 Ah is 4.1 g (0.41 g per 100 mAh), and has the structure shown in FIGS. A thin non-aqueous electrolyte secondary battery having a thickness of 3 mm, a width of 40 mm, and a height of 70 mm was assembled.

Example 2
A thin nonaqueous electrolyte secondary battery was assembled in the same manner as in Example 1 except that aluminum was used as the negative electrode.

Example 3
An electrode group produced in the same manner as described in Example 1 was stored in a bag-shaped laminate film so that the laminated surface could be seen from the opening of the bag. Polyvinylidene fluoride (PVdF), which is an adhesive polymer, was dissolved in 0.5% by weight in dimethylformamide (boiling point: 153 ° C.), which is an organic solvent. The obtained solution was poured into the electrode group in the laminate film so that the amount per 100 mAh of battery capacity was the same as in Example 1, and the solution was allowed to penetrate into the electrode group, and the entire surface of the electrode group Adhered to.

  Next, the electrode group in the laminate film is vacuum-dried at 40 ° C. for 24 hours to evaporate the organic solvent, hold the polymer having adhesiveness in the gaps between the positive electrode, the negative electrode, and the separator. A porous adhesive part was formed on the surface of the film. The total amount of PVdF was 1.15 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 1Ah of battery capacity is the same as in Example 1, and has the structure shown in FIGS. A thin non-aqueous electrolyte secondary battery having a width of 40 mm and a height of 70 mm was assembled.

Example 4
A thin nonaqueous electrolyte secondary battery was assembled in the same manner as described in Example 3 except that the vacuum drying conditions were 80 ° C. and 12 hours.

Example 5
A thin nonaqueous electrolyte secondary battery was assembled in the same manner as described in Example 3 except that the vacuum drying conditions were 100 ° C. and 6 hours.

Example 6
A thin nonaqueous electrolyte secondary battery was assembled in the same manner as in Example 3 except that aluminum was used as the negative electrode.

Example 7
An electrode group produced in the same manner as described in Example 1 was stored in a bag-shaped laminate film so that the laminated surface could be seen from the opening of the bag. Polyvinylidene fluoride (PVdF) which is an adhesive polymer was dissolved in 0.1% by weight in dimethylformamide (boiling point: 153 ° C.) which is an organic solvent. The obtained solution was poured into the electrode group in the laminate film so that the amount per 100 mAh of battery capacity was the same as in Example 1, and the solution was allowed to penetrate into the electrode group, and the entire surface of the electrode group Adhered to.

  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 0.23 mg per 100 mAh of battery capacity.

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

Example 8
An electrode group produced in the same manner as described in Example 1 was stored in a bag-shaped laminate film so that the laminated surface could be seen from the opening of the bag. 1% by weight of polyvinylidene fluoride (PVdF), which is an adhesive polymer, was dissolved in dimethylformamide (boiling point: 153 ° C.), which is an organic solvent. The obtained solution was poured into the electrode group in the laminate film so that the amount per 100 mAh of battery capacity was the same as in Example 1, and the solution was allowed to penetrate into the electrode group, and the entire surface of the electrode group Adhered to.

  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 2.3 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 1Ah of battery capacity is the same as in Example 1, and has the structure shown in FIG. A thin non-aqueous electrolyte secondary battery having a height of 40 mm and a height of 70 mm was assembled.

Example 9
An electrode group produced in the same manner as described in Example 1 was stored in a bag-shaped laminate film so that the laminated surface could be seen from the opening of the bag. Polyvinylidene fluoride (PVdF), which is an adhesive polymer, was dissolved in 2.5% by weight in dimethylformamide (boiling point: 153 ° C.), which is an organic solvent. The obtained solution was poured into the electrode group in the laminate film so that the amount per 100 mAh of battery capacity was the same as in Example 1, and the solution was allowed to penetrate into the electrode group, and the entire surface of the electrode group Adhered to.

  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 2.88 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 1Ah of battery capacity is the same as in Example 1, and has the structure shown in FIG. A thin non-aqueous electrolyte secondary battery having a height of 40 mm and a height of 70 mm was assembled.

Example 10
An electrode group produced in the same manner as described in Example 1 was stored in a bag-shaped laminate film so that the laminated surface could be seen from the opening of the bag. 1 wt% of polyacrylate (PMMA), which is an adhesive polymer, was dissolved in dimethylformamide (boiling point: 153 ° C.), which is an organic solvent. The obtained solution was poured into the electrode group in the laminate film so that the amount per 100 mAh of battery capacity was the same as in Example 1, and the solution was allowed to penetrate into the electrode group, and the entire surface of the electrode group Adhered to.

  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 PMMA was 1.15 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 1Ah of battery capacity is the same as in Example 1, and has the structure shown in FIG. A thin non-aqueous electrolyte secondary battery having a height of 40 mm and a height of 70 mm was assembled.

Example 11
An electrode group produced in the same manner as described in Example 1 was stored in a bag-shaped laminate film so that the laminated surface could be seen from the opening of the bag. Polyvinyl chloride (PVC), which is an adhesive polymer, was dissolved in 0.5% by weight in dimethylformamide (boiling point: 153 ° C.), which is an organic solvent. The obtained solution was poured into the electrode group in the laminate film so that the amount per 100 mAh of battery capacity was the same as in Example 1, and the solution was allowed to penetrate into the electrode group, and the entire surface of the electrode group Adhered to.

  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 PVC was 1.15 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 1Ah of battery capacity is the same as in Example 1, and has the structure shown in FIG. A thin non-aqueous electrolyte secondary battery having a height of 40 mm and a height of 70 mm was assembled.

Example 12
An electrode group produced in the same manner as described in Example 1 was stored in a bag-shaped laminate film so that the laminated surface could be seen from the opening of the bag. Polyethylene oxide (PEO), which is an adhesive polymer, was dissolved in 0.5 wt% in dimethylformamide (boiling point: 153 ° C.), which is an organic solvent. The obtained solution was poured into the electrode group in the laminate film so that the amount per 100 mAh of battery capacity was the same as in Example 1, and the solution was allowed to penetrate into the electrode group, and the entire surface of the electrode group Adhered to.

  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 PEO was 1.15 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 1Ah of battery capacity is the same as in Example 1, and has the structure shown in FIG. A thin non-aqueous electrolyte secondary battery having a height of 40 mm and a height of 70 mm was assembled.

Comparative Example 1
An electrode group produced in the same manner as described in Example 1 above is stored in a bag formed of a laminate film so that the laminated surface can be seen from the opening of the bag, and vacuum drying is performed on the electrode group. It applied at 12 degreeC for 12 hours. The non-aqueous electrolyte is injected into the electrode group in the laminate film so that the amount per 1Ah of battery capacity is the same as in Example 1, and has the structure shown in FIG. A thin non-aqueous electrolyte secondary battery having a height of 40 mm and a height of 70 mm was assembled.

Comparative Example 2
A gel electrolyte (polyacrylonitrile (PAN), LiPF ₆ , EC and MEC mixed at a molar ratio of PAN: LiPF ₆ : EC: MEC = 16: 5: 55: 24) instead of the non-aqueous electrolyte is used from the nonwoven fabric. A thin nonaqueous electrolyte secondary battery was assembled in the same manner as in Example 1 except that the separator was impregnated and used, and a porous adhesive layer was not formed.

Comparative Example 3
3% by weight of polyvinylidene fluoride (PVdF), which is an adhesive polymer, was dissolved in dimethylformamide (boiling point: 153 ° C.), which is an organic solvent. The resulting solution was applied to both sides of a separator similar to that described in Example 1. The separator was interposed between the same positive electrode and negative electrodes A and B as described in Example 1 to prepare a laminate. The laminate was vacuum-dried at 80 ° C. for 12 hours to form a porous adhesive layer between the positive electrode and the separator and between the negative electrode and the separator. Next, the laminate was wound in a spiral shape, and then formed into a flat shape to produce an electrode group.

  The non-aqueous electrolyte is injected into the electrode group in the laminate film so that the amount per 1Ah of battery capacity is the same as in Example 1, and is a thin non-aqueous electrolysis having a thickness of 3 mm, a width of 40 mm, and a height of 70 mm. A liquid secondary battery was assembled.

  About the obtained secondary batteries of Examples 1, 3 to 5, 7 to 12 and Comparative Examples 1 to 3, after charging for 5 hours to 4.2 V at a charging current of 300 mA, the charge / discharge cycle discharging to 2.7 V at 300 mA The test was conducted in an atmosphere at 20 ° C. On the other hand, the secondary batteries of Examples 2 and 6 were charged and discharged at a charging current of 300 mA to 4.0 V for 5 hours, and then charged and discharged at 300 mA to 2.7 V in a 20 ° C. atmosphere. The discharge capacity (initial capacity) at the first cycle in each charge / discharge cycle test and the capacity retention rate (with respect to the initial capacity) at 300 cycles are shown in Table 2 below.

Moreover, about the secondary battery of Examples 1, 3-5, 7-12, and Comparative Examples 1-3, after charging for 5 hours to 4.2V with the charging current of 300 mA, the discharge capacity at the time of discharging to 2.7V at 2C The capacity retention rate at 2C discharge rate (ratio of the discharge capacity at 2C to the initial capacity) is calculated, and the results are also shown in Table 2 below. On the other hand, for the secondary batteries of Examples 2 and 6, after charging to 4.0 V at a charging current of 300 mA for 5 hours, the discharge capacity when discharged to 2.7 V at 2 C was measured to maintain the capacity at the 2 C discharge rate. The rate is calculated and the result is also shown in Table 2 below.

  As is clear from Tables 1 and 2, the secondary batteries of Examples 1 to 12 are excellent in initial capacity and cycle life, and in particular, compared with the secondary batteries of Comparative Examples 1 to 3 in terms of discharge capacity at a large current of 2C. Can be improved.

  On the other hand, it can be seen that the secondary battery of Comparative Example 1 has much lower initial capacity, cycle life, and large current discharge capacity than Examples 1-12. On the other hand, the secondary battery of Comparative Example 2 has a lower discharge capacity at a large current of 2C than the secondary batteries of Examples 1-12. Moreover, it turns out that the secondary battery of the comparative example 3 has a low initial capacity, a cycle life, and a large current discharge capacity compared with Examples 1-12.

Moreover, about the secondary battery of Examples 6-9 and Comparative Examples 1-3, content of the adhesive polymer of a separator was measured and the result is shown in following Table 3.

Further, for the secondary batteries of Examples 4 and 8 and Comparative Example 3, the concentration of the adhesive polymer in the central portion of the separator in the thickness direction, the surface facing the positive electrode and the surface facing the negative electrode was measured, respectively. Is shown in Table 4 below.

  As is apparent from Table 4, the separators included in the secondary batteries of Examples 4 and 8 have a lower internal adhesive polymer concentration than the adhesive polymer concentration on the surface facing the positive electrode or the negative electrode. . On the other hand, the separator contained in the secondary battery of Comparative Example 3 shows that the internal adhesive polymer concentration is higher than the adhesive polymer concentration on the surface facing the positive electrode or the negative electrode. This is because in Comparative Example 3, a polymer solution having adhesiveness was directly applied to the separator.

Example 12-1
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 assembled in the same manner as in Example 4.

Example 12-2
A thin non-aqueous electrolyte secondary battery was assembled in the same manner as in Example 12-1, except that the air permeability of the separator porous film was 580 sec / 100 cm ³ .

Example 12-3
A thin non-aqueous electrolyte secondary battery was assembled in the same manner as in Example 12-1, except that the air permeability of the porous sheet of the separator was 400 sec / 100 cm ³ .

Example 12-4
A thin non-aqueous electrolyte secondary battery was assembled in the same manner as in Example 12-1, 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 12-1 to 12-4, a charge / discharge cycle test was performed in an atmosphere of 20 ° C., which was charged to 4.2 V at a charging current of 300 mA for 5 hours and then discharged to 2.7 V at 300 mA. did. The discharge capacity (initial capacity) at the first cycle in each charge / discharge cycle test and the capacity retention rate (with respect to the initial capacity) at 300 cycles are shown in Table 5 below.

Moreover, about the secondary battery of Examples 12-1 to 12-4, after charging for 5 hours to 4.2V with a charging current of 300 mA, the discharge capacity when discharged to 2.7V at 2C was measured, and discharging at 2C was performed. The ratio of the capacity to the initial capacity is calculated, and the result is also shown in Table 5 below as the capacity maintenance ratio at the 2C discharge rate.

Example 13
<Preparation of positive electrode>
First, 91% by weight of lithium cobalt oxide (Li _x CoO ₂ ) powder was added to toluene by adding 3.5% by weight of acetylene black, 3.5% by weight of graphite and 2% by weight of ethylene propylene diene monomer powder. A positive electrode having a structure in which an electrode density was 3 g / cm ³ and a positive electrode layer was supported on both surfaces of the current collector was applied by pressing the current collector on both surfaces of an aluminum foil having a thickness of 30 μm.

<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 this is applied to both sides of a copper foil having a thickness of 15 μm as a current collector, dried and pressed to obtain an electrode density of 1.3 g / cm ^3. Thus, a negative electrode having a structure in which the negative electrode layer was supported on both surfaces of the current collector was produced.

  The positive electrode and the negative electrode were wound in a spiral shape through a separator made of a polyethylene porous film having a thickness of 15 μm to prepare an electrode group.

  Subsequently, the electrode group was accommodated in a stainless steel bottomed cylindrical container. Polyvinylidene fluoride (PVdF) which is an adhesive polymer was dissolved in 0.1% by weight in dimethylformamide (boiling point: 153 ° C.) which is an organic solvent. The obtained solution is injected into the electrode group in the container so that the amount per 100 mAh of battery capacity is 0.25 ml, and the solution is infiltrated into the electrode group and adheres to the entire surface of the electrode group. I let you.

  Next, the electrode group in the container is vacuum-dried at 80 ° C. for 12 hours to evaporate the organic solvent, hold the polymer having adhesiveness in the gap between the positive electrode, the negative electrode, and the separator, and A porous adhesive part was formed on the surface. The total amount of PVdF was 0.23 mg per 100 mAh of battery capacity.

  A nonaqueous electrolyte similar to that described in Example 1 is injected into the electrode group in the container so that the amount per battery capacity of 1 Ah is 3.8 g, and sealing is performed to form a cylindrical nonaqueous electrolyte. A secondary battery was assembled.

Comparative Example 4
A positive electrode similar to that described in Example 13 and the negative electrode were spirally wound through a separator made of a polyethylene porous film having a thickness of 25 μm to produce an electrode group.

  Next, the electrode group is housed in a bottomed cylindrical container made of stainless steel, and a non-aqueous electrolyte similar to that described in Example 1 is injected so that the amount per battery capacity 1 Ah is 3.8 g. A cylindrical non-aqueous electrolyte secondary battery was assembled by sealing and the like.

  About the obtained secondary battery of Example 13 and Comparative Example 4, after charging to 4.2V at a charging current of 800 mA for 3 hours, a charge / discharge cycle test was performed in an atmosphere of 20 ° C. to discharge to 2.7 V at 800 mA. The discharge capacity (initial capacity) at the first cycle in each charge / discharge cycle test and the capacity retention rate (with respect to the initial capacity) at 300 cycles are shown in Table 6 below.

Moreover, about the secondary battery of Example 13 and Comparative Example 4, after charging to 4.2V for 3 hours with a charging current of 800 mA, the discharge capacity when discharged to 2.7V at 2C was measured, and the capacity at the 2C discharge rate The maintenance ratio (ratio of the discharge capacity at 2C to the initial capacity) is calculated, and the results are also shown in Table 6 below.

  As is clear from Table 6, the secondary battery of Example 13 can use a thinner separator than the secondary battery of Comparative Example 4, and is excellent in initial capacity, cycle life, and large current discharge characteristics. I understand that.

  Moreover, in Example 13 mentioned above, although the example applied to the cylindrical non-aqueous-electrolyte secondary battery provided with a metal bottomed cylindrical container was demonstrated, the square provided with a metal bottomed rectangular cylindrical container The present invention can be similarly applied to a non-aqueous electrolyte secondary battery.

Example 14
<Preparation of positive electrode>
First, 91% by weight of lithium cobalt oxide (Li _x CoO _2, where X is 0 ≦ X ≦ 1) powder, 3.5% by weight of acetylene black, 3.5% by weight of graphite, and ethylene propylene as a binder Current collector made of porous aluminum foil (thickness 15 μm) having ² mm by weight of diene monomer (EPDM) powder and toluene mixed together and having 10 holes per 10 cm ² and having a diameter of 0.5 mm. After coating on both sides, a positive electrode having an electrode density of 3 g / cm ³ 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, the negative electrode having an electrode density of 1.3 g / cm ³ was produced by drying and pressing.

<Separator>
A separator made of a polyethylene porous film having a thickness of 25 μm, a thermal shrinkage of 20% at 120 ° C. for 1 hour, and a porosity of 50% was prepared. The length along the longitudinal direction of the separator is 2 mm longer than the positive electrode and 1.5 mm longer than the negative electrode. Moreover, the length orthogonal to the longitudinal direction of the separator is 2 mm longer than the positive electrode and 1.5 mm longer than the negative electrode.

<Preparation of non-aqueous electrolyte>
A non-aqueous electrolyte was prepared by dissolving 1 mol / l of lithium hexafluorophosphate (LiPF ₆ ) in a mixed solvent of ethylene carbonate (EC) and methyl ethyl carbonate (MEC) (mixing volume ratio 1: 2).

<Production of electrode group>
A belt-like positive electrode lead was welded to the obtained positive electrode current collector, and a belt-like negative electrode lead was welded to the negative electrode current collector. Subsequently, the positive electrode, the negative electrode, and the separator are laminated in the order of the separator, the positive electrode, the separator, and the negative electrode, and the obtained laminate is spirally wound so that the outermost periphery becomes a separator, and then formed into a flat shape to form an electrode. Groups were made. In the obtained electrode group, the negative electrode protruded compared to the positive electrode, and the separator protruded compared to the negative electrode. The protruding length of each end of the separator was 1 mm when measured from each end of the positive electrode and 0.75 mm when measured from each end of the negative electrode.

  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 could be seen from the opening of the bag. Polyacrylonitrile (PAN), which is an adhesive polymer, was dissolved in 0.5% 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 100 mAh of battery capacity was 0.25 ml, the solution was infiltrated into the electrode group, and the entire surface of the electrode group was introduced. 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 PAN was 1.25 mg per 100 mAh battery capacity. In addition, the total amount of the adhesive polymer (for example, PAN) was calculated from the amount of weight increase when compared with the electrode group before impregnating the adhesive polymer solution.

  The non-aqueous electrolyte is injected into the electrode group in the laminate film so that the amount per battery capacity 1 Ah is 4.1 g (0.41 g when converted per 100 mAh), the thickness is 3 mm, the width is 40 mm, A thin non-aqueous electrolyte secondary battery having a height of 70 mm was assembled.

Example 15
A thin non-aqueous electrolyte secondary battery was assembled in the same manner as in Example 14 except that aluminum was used as the negative electrode.

Example 16
An electrode group produced in the same manner as described in Example 14 was stored in a bag-shaped laminate film so that the laminated surface could be seen from the opening of the bag. Polyvinylidene fluoride (PVdF), which is an adhesive polymer, was dissolved in 0.5% 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 100 mAh of battery capacity was the same as in Example 14, so that the solution penetrated into the electrode group, and the entire surface of the electrode group Adhered to.

  Next, the electrode group in the laminate film is vacuum dried at 40 ° C. for 24 hours to evaporate the organic solvent, evaporate the organic solvent, and form a polymer having adhesiveness in the gaps between the positive electrode, the negative electrode, and the separator. While being held, a porous adhesive portion was formed on the surface of the electrode group. The total amount of PVdF was 1.15 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 1Ah of battery capacity is the same as in Example 14, and is a thin non-aqueous electrolysis having a thickness of 3 mm, a width of 40 mm, and a height of 70 mm. A liquid secondary battery was assembled.

Example 17
A thin nonaqueous electrolyte secondary battery was assembled in the same manner as described in Example 16 except that the vacuum drying conditions were 80 ° C. and 12 hours.

Example 18
A thin nonaqueous electrolyte secondary battery was assembled in the same manner as described in Example 16 except that the vacuum drying conditions were 100 ° C. and 6 hours.

Example 19
A thin non-aqueous electrolyte secondary battery was assembled in the same manner as in Example 16 except that aluminum was used as the negative electrode.

Example 20
An electrode group produced in the same manner as described in Example 14 was stored in a bag-shaped laminate film so that the laminated surface could be seen from the opening of the bag. Polyvinylidene fluoride (PVdF) which is an adhesive polymer was dissolved in 0.1% 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 100 mAh of battery capacity was the same as in Example 14, so that the solution penetrated into the electrode group, and the entire surface of the electrode group Adhered to.

  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 0.23 mg per 100 mAh of battery capacity.

  The non-aqueous electrolyte is injected into the electrode group in the laminate film so that the amount per 1Ah of battery capacity is the same as in Example 14, and is a thin non-aqueous electrolysis having a thickness of 3 mm, a width of 40 mm, and a height of 70 mm. A liquid secondary battery was assembled.

Example 21
An electrode group produced in the same manner as described in Example 14 was stored in a bag-shaped laminate film so that the laminated surface could be seen from the opening of the bag. 1% by weight of polyvinylidene fluoride (PVdF), which is an adhesive polymer, was dissolved 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 100 mAh of battery capacity was the same as in Example 14, so that the solution penetrated into the electrode group, and the entire surface of the electrode group Adhered to.

  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 2.3 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 1Ah of battery capacity is the same as in Example 14, and is a thin non-aqueous electrolysis having a thickness of 3 mm, a width of 40 mm, and a height of 70 mm. A liquid secondary battery was assembled.

Example 22
An electrode group produced in the same manner as described in Example 14 was stored in a bag-shaped laminate film so that the laminated surface could be seen from the opening of the bag. Polyvinylidene fluoride (PVdF), which is an adhesive polymer, was dissolved in 2.5% 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 100 mAh of battery capacity was the same as in Example 14, so that the solution penetrated into the electrode group, and the entire surface of the electrode group Adhered to.

  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 2.88 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 1Ah of battery capacity is the same as in Example 14, and is a thin non-aqueous electrolysis having a thickness of 3 mm, a width of 40 mm, and a height of 70 mm. A liquid secondary battery was assembled.

Example 23
An electrode group produced in the same manner as described in Example 14 was stored in a bag-shaped laminate film so that the laminated surface could be seen from the opening of the bag. 1 wt% of polyacrylate (PMMA), which is an adhesive polymer, was dissolved 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 100 mAh of battery capacity was the same as in Example 14, so that the solution penetrated into the electrode group, and the entire surface of the electrode group Adhered to.

  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 PMMA was 1.15 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 1Ah of battery capacity is the same as in Example 14, and is a thin non-aqueous electrolysis having a thickness of 3 mm, a width of 40 mm, and a height of 70 mm. A liquid secondary battery was assembled.

Example 24
An electrode group produced in the same manner as described in Example 14 was stored in a bag-shaped laminate film so that the laminated surface could be seen from the opening of the bag. Polyvinyl chloride (PVC), which is an adhesive polymer, was dissolved in 0.5% 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 100 mAh of battery capacity was the same as in Example 14, so that the solution penetrated into the electrode group, and the entire surface of the electrode group Adhered to.

  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 PVC was 1.15 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 1Ah of battery capacity is the same as in Example 14, and is a thin non-aqueous electrolysis having a thickness of 3 mm, a width of 40 mm, and a height of 70 mm. A liquid secondary battery was assembled.

Example 25
An electrode group produced in the same manner as described in Example 14 was stored in a bag-shaped laminate film so that the laminated surface could be seen from the opening of the bag. Polyethylene oxide (PEO), which is an adhesive polymer, was dissolved in 0.5 wt% 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 100 mAh of battery capacity was the same as in Example 14, so that the solution penetrated into the electrode group, and the entire surface of the electrode group Adhered to.

  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 PEO was 1.15 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 1Ah of battery capacity is the same as in Example 14, and has the structure shown in FIG. A thin non-aqueous electrolyte secondary battery having a height of 40 mm and a height of 70 mm was assembled.

Comparative Example 5
An electrode group produced in the same manner as described in Example 14 is stored in a bag formed of a laminate film so that the laminated surface can be seen from the opening of the bag, and vacuum drying is performed on the electrode group. It applied at 12 degreeC for 12 hours. The non-aqueous electrolyte is injected into the electrode group in the laminate film so that the amount per 1Ah of the battery capacity is the same as in Example 14, and is a thin non-aqueous electrolysis having a thickness of 3 mm, a width of 40 mm, and a height of 70 mm. A liquid secondary battery was assembled.

Comparative Example 6
Instead of non-aqueous electrolyte, gel electrolyte (polyacrylonitrile (PAN), LiPF ₆ , EC and MEC mixed at a molar ratio of PAN: LiPF ₆ : EC: MEC = 16: 5: 55: 24) is used as a non-woven fabric. Impregnation was performed to produce a separator.

  A positive electrode and a negative electrode similar to those described in Example 14 were spirally wound with the separator interposed therebetween, and then formed into a flat shape to prepare an electrode group. The electrode group was stored in a bag-shaped laminate film so that the laminated surface could be seen from the opening of the bag, and the electrode group was vacuum dried at 80 ° C. for 12 hours. Next, the non-aqueous electrolyte solution is injected into the electrode group in the laminate film so that the amount per 1Ah of battery capacity is the same as in Example 14, and the thickness is 3 mm, the width is 40 mm, and the height is 70 mm. A water electrolyte secondary battery was assembled.

Comparative Example 7
3% by weight of polyvinylidene fluoride (PVdF), which is an adhesive polymer, was dissolved in dimethylformamide (boiling point: 153 ° C.), which is an organic solvent. The resulting solution was applied to both sides of a separator similar to that described in Example 14. The separator was interposed between the same positive electrode and negative electrode as described in Example 14 to produce a laminate. The laminate was vacuum-dried at 80 ° C. for 12 hours to form a porous adhesive layer between the positive electrode and the separator and between the negative electrode and the separator. Next, the laminate was wound in a spiral shape, and then formed into a flat shape to produce an electrode group.

  The non-aqueous electrolyte is injected into the electrode group in the laminate film so that the amount per 1Ah of battery capacity is the same as in Example 14, and is a thin non-aqueous electrolysis having a thickness of 3 mm, a width of 40 mm, and a height of 70 mm. A liquid secondary battery was assembled. In addition, it was 15 weight% when content of the adhesive polymer in the said separator was measured.

  About the obtained secondary batteries of Examples 14, 16 to 18, 20 to 25 and Comparative Examples 5 to 7, after charging for 5 hours to 4.2 V at a charging current of 300 mA, the charge / discharge cycle discharging to 2.7 V at 300 mA The test was conducted in an atmosphere at 20 ° C. On the other hand, the secondary batteries of Examples 15 and 19 were charged and discharged at a charging current of 300 mA to 4.0 V for 5 hours, and then subjected to a charge / discharge cycle test at 300 mA to 2.7 V in an atmosphere of 20 ° C. The discharge capacity (initial capacity) at the first cycle in each charge / discharge cycle test and the capacity retention rate (with respect to the initial capacity) at 300 cycles are shown in Table 9 below.

Moreover, about the secondary battery of Examples 14, 16-18, 20-25, and Comparative Examples 5-7, after charging for 5 hours to 4.2V with a charging current of 300 mA, it discharged at 2C to 2.7V. The ratio of the discharge capacity at 2C to the initial capacity is calculated, and the result is also shown in Table 9 below as the capacity retention rate at the 2C discharge rate. On the other hand, for the secondary batteries of Examples 15 and 19, the capacity was maintained at the 2C discharge rate by measuring the discharge capacity when discharged to 2.7V at 2C after charging to 4.0V at a charging current of 300 mA for 5 hours. The rate is calculated and the result is also shown in Table 9 below.

  As is clear from Tables 7 to 9, the secondary batteries of Examples 14 to 25 are excellent in initial capacity and cycle life, and in particular, the discharge capacity at a large current of 2C is compared with the secondary batteries of Comparative Examples 5 to 7. Can be improved.

  On the other hand, the secondary battery of Comparative Example 5 is found to have much lower initial capacity, cycle life, and large current discharge capacity than Examples 14-25. On the other hand, it can be seen that the secondary battery of Comparative Example 6 has a lower discharge capacity at a large current of 2C than the secondary batteries of Examples 14-25. Moreover, it turns out that the secondary battery of the comparative example 7 has a low initial capacity, a cycle life, and a large current discharge capacity compared with Examples 14-25.

  In Examples 14 to 25 described above, an example in which an electrode group having a structure in which the positive electrode and the negative electrode are wound in a spiral shape via a separator and then compressed in the radial direction has been described. 5 except that the structure of the electrode group is changed as shown in FIG. 5 described above, that is, the positive electrode and the negative electrode are bent six times so that the negative electrodes are in contact with each other through the separator. When a thin non-aqueous electrolyte secondary battery was assembled, the battery capacity was reduced by about 10% compared to Example 17, but the other performances were equivalent to Example 17.

Example 26
In the same manner as described in Example 12-1, an electrode group was prepared and stored in a laminate film. Next, by pressing the laminate film 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. without injecting a polymer solution having adhesiveness, L ₂ / L ₁ was prepared an electrode group is 1.00.

  The non-aqueous electrolyte is injected into the electrode group in the laminate film so that the amount per 1Ah of battery capacity is the same as in Example 1, and is a thin non-aqueous electrolysis having a thickness of 3 mm, a width of 40 mm, and a height of 70 mm. A liquid secondary battery was assembled. In the secondary battery, the content of the adhesive polymer in the electrode group was 0% by weight.

Examples 27 to 33 and Comparative Example 8
A thin nonaqueous electrolyte secondary battery was assembled in the same manner as in Example 26 described above except that L ₂ / L ₁ was set as shown in Table 10 below by changing the pressing pressure.

Comparative Example 9
In the same manner as described in Example 12-1, an electrode group was prepared and stored in a laminate film. Next, by pressing the laminated film at a pressure of 0.001 kg / cm ² along the thickness direction of the electrode group in a vacuum atmosphere at 25 ° C. without injecting an adhesive polymer solution. An electrode group having L ₂ / L ₁ of 1.30 was produced.

  The non-aqueous electrolyte is injected into the electrode group in the laminate film so that the amount per 1Ah of battery capacity is the same as in Example 1, and is a thin non-aqueous electrolysis having a thickness of 3 mm, a width of 40 mm, and a height of 70 mm. A liquid secondary battery was assembled.

Example 34
A thin nonaqueous electrolyte secondary battery was assembled in the same manner as in Example 26 described above except that the air permeability of the porous film of the separator was 580 sec / 100 cm ³ .

Example 35
A thin nonaqueous electrolyte secondary battery was assembled in the same manner as in Example 26 described above, except that the air permeability of the porous sheet of the separator was set to 400 sec / 100 cm ³ .

Example 36
A thin non-aqueous electrolyte secondary battery was assembled in the same manner as in Example 26 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 26 to 36 and Comparative Examples 8 to 9, internal impedance at 1 kHz was measured, and the results are shown in Table 10 below. In addition, a charge / discharge cycle test was performed under the same conditions as described in Example 1 above, and the discharge capacity (initial capacity) at the first cycle and the capacity retention rate (with respect to the initial capacity) at 300 cycles are shown in Table 10 below. Shown in

As can be seen from Table 10, the secondary batteries of Examples 26 to 36 including an electrode group in which L ₂ / L ₁ is 0.90 to 1.20 include an electrode group in which L ₂ / L ₁ is out of the above range. It can be seen that the internal impedance is lower than the secondary batteries of Comparative Examples 8 and 9 provided, and the initial capacity and the capacity maintenance rate at the 300th cycle are high.

Example 37
A positive electrode and a negative electrode similar to those described in Example 1 were interposed between the same separators as described in Example 12-1, and an electrode group was prepared by bending 6 times so that the negative electrodes were in contact with each other. The electrode group was stored in a bag-like laminate film similar to that described in Example 1 so that the laminated surface could be seen from the opening.

Next, an electrode group with L ₄ / L ₃ of 1.00 is produced by pressing the laminate film 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. did.

  The non-aqueous electrolyte is injected into the electrode group in the laminate film so that the amount per 1Ah of battery capacity is the same as in Example 1, and is a thin non-aqueous electrolysis having a thickness of 3 mm, a width of 40 mm, and a height of 70 mm. A liquid secondary battery was assembled. In the secondary battery, the content of the adhesive polymer in the electrode group was 0% by weight.

Examples 38 to 44 and Comparative Example 10
A thin non-aqueous electrolyte secondary battery was assembled in the same manner as in Example 37 described above except that L ₄ / L ₃ was set as shown in Table 11 below by changing the pressing pressure.

Comparative Example 11
In the same manner as described in Example 37, an electrode group was prepared and stored in a laminate film. Next, an electrode group having L ₄ / L ₃ of 1.30 is obtained by pressing the laminate film in a vacuum atmosphere at 25 ° C. at a pressure of 0.001 kg / cm ² along the thickness direction of the electrode group. Produced.

  The non-aqueous electrolyte is injected into the electrode group in the laminate film so that the amount per 1Ah of battery capacity is the same as in Example 1, and is a thin non-aqueous electrolysis having a thickness of 3 mm, a width of 40 mm, and a height of 70 mm. A liquid secondary battery was assembled.

Example 45
A thin non-aqueous electrolyte secondary battery was assembled in the same manner as in Example 37 described above except that the air permeability of the porous film of the separator was 580 sec / 100 cm ³ .

Example 46
A thin nonaqueous electrolyte secondary battery was assembled in the same manner as in Example 37 described above, except that the air permeability of the porous sheet of the separator was set to 400 sec / 100 cm ³ .

Example 47
A thin nonaqueous electrolyte secondary battery was assembled in the same manner as in Example 37 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 37 to 47 and Comparative Examples 10 to 11, the internal impedance at 1 kHz was measured, and the results are shown in Table 11 below. In addition, a charge / discharge cycle test was performed under the same conditions as described in Example 1 above, and the discharge capacity (initial capacity) at the first cycle and the capacity retention rate at 300 cycles (relative to the initial capacity) are shown in Table 11 below. Shown in

As is clear from Table 11, the secondary batteries of Examples 37 to 47 including the electrode group in which L ₄ / L ₃ is 0.90 to 1.20 are electrode groups in which L ₄ / L ₃ is out of the above range. It can be seen that the internal impedance is lower than the secondary batteries of Comparative Examples 10 and 11 provided, and the initial capacity and the capacity maintenance rate at the 300th cycle are high.

Example 48
An electrode group produced in the same manner as described in Example 12-1 was stored in a bag-shaped laminate film so that the laminated surface could be seen from the opening of the bag. On the other hand, polyvinylidene fluoride (PVdF) which is an adhesive polymer was dissolved in 0.5% 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 laminate film is pressed at a pressure of 1.5 kg / cm ² along the thickness direction of the electrode group in a high-temperature vacuum atmosphere at 80 ° C., whereby L ₂ / L ₁ is 1.02. Was made. Also, by this step, the organic solvent is evaporated, and the positive electrode, the negative electrode, and the separator are bonded to each other, and a porous adhesive layer is formed on the surface of the electrode group so that the electrode group is the laminate film. Adhered to the inner surface.

  In the electrode group, the positive electrode and the separator were bonded by a polymer having adhesive properties scattered in the inside and the boundary. Moreover, the said negative electrode and the said separator were adhere | attached with the polymer | macromolecule which has the adhesiveness scattered in the inside and boundary.

  The non-aqueous electrolyte is injected into the electrode group in the laminate film so that the amount per 1Ah of battery capacity is the same as in Example 1, and is a thin non-aqueous electrolysis having a thickness of 3 mm, a width of 40 mm, and a height of 70 mm. A liquid secondary battery was assembled.

Example 49
A thin non-aqueous electrolyte secondary battery was assembled in the same manner as described in Example 48, except that the electrode group was molded by being inserted into the mold.

About the obtained secondary battery of Examples 48-49, the charging / discharging cycle test was implemented on the same conditions as having mentioned above. The discharge capacity (initial capacity) at the first cycle in each charge / discharge cycle test and the capacity maintenance rate at 300 cycles are shown in Table 12 below. Moreover, about the secondary battery of Examples 48-49, the capacity | capacitance maintenance factor in 2C discharge rate was computed on the same conditions as having demonstrated in Example 1 mentioned above, and the result is written together in following Table 12. FIG.

  As is clear from Table 12, the secondary batteries of Examples 48 and 49 have an initial capacity, a capacity retention rate after 300 cycles, and a capacity at 2C discharge, as compared with the secondary batteries of Examples 1 to 12 and 14 to 47. It can be seen that the maintenance rate is excellent.

Example 50
A positive electrode and a negative electrode similar to those described in Example 14 were prepared. Further, a polyethylene porous film similar to that described in Example 12-1 was prepared as a separator. The length of the separator is 2 mm longer than the positive electrode and 1.5 mm longer than the negative electrode, and the length perpendicular to the longitudinal direction is 2 mm longer than the positive electrode. And 1.5 mm longer than the negative electrode.

<Production of electrode group>
As an adhesive polymer, polyacrylonitrile (PAN) was dissolved in 1% by weight in a dimethylformamide (boiling point: 153 ° C.) solution. The obtained solution was applied to the positive electrode layer surface of the positive electrode and the negative electrode layer surface of the negative electrode, and the separator was disposed between the positive electrode layer surface and the negative electrode layer surface. The obtained laminate was vacuum-dried at 80 ° C. for 12 hours to evaporate dimethylformamide, thereby forming a porous adhesive layer between each electrode layer and the separator to obtain an electrode group. In the obtained electrode group, the negative electrode protruded compared to the positive electrode, and the separator protruded compared to the negative electrode. The protruding length of each end of the separator was 1 mm when measured from each end of the positive electrode and 0.75 mm when measured from each end of the negative electrode. Further, the PAN content in the separator was as shown in Table 13 below.

  After the electrode group was housed in a 100 μm thick laminate film in which both surfaces of an aluminum foil were covered with polypropylene, a non-aqueous electrolyte similar to that described in Example 1 was applied in an amount of 4.1 g per 1 Ah of battery capacity ( A thin non-aqueous electrolyte secondary battery having the structure shown in FIG. 10 described above, a thickness of 3 mm, a width of 40 mm, and a height of 70 mm is injected so as to be equivalent to 0.41 g per 100 mAh. Assembled.

Examples 51-54
A thin nonaqueous electrolyte secondary battery having the same configuration as in Example 50 described above was assembled except that the polymer having adhesiveness was changed to the type of polymer shown in Table 13 below.

Example 55
A thin nonaqueous electrolyte secondary battery having the same configuration as that of Example 50 described above was assembled except that a negative electrode made of an aluminum plate having a thickness of 0.1 mm was used.

Example 56
A thin non-aqueous electrolyte secondary battery was assembled in the same manner as in Example 50 described above except that the content of PAN in the separator was 0.4% by weight.

Example 57
A thin nonaqueous electrolyte secondary battery was assembled in the same manner as in Example 50 described above, except that the content of PAN in the separator was 0.3% by weight.

Comparative Example 12
3% by weight of polyvinylidene fluoride (PVdF), which is an adhesive polymer, was dissolved in dimethylformamide (boiling point: 153 ° C.), which is an organic solvent. The resulting solution was applied to both sides of a separator similar to that described in Example 50. Next, the separator was interposed between the same positive electrode and negative electrode as described in Example 50 to prepare a laminate. The laminate was vacuum-dried at 80 ° C. for 12 hours to form a porous adhesive layer between the positive electrode and the separator and between the negative electrode and the separator. In the obtained electrode group, the negative electrode protruded compared to the positive electrode, and the separator protruded compared to the negative electrode. The protruding length of each end of the separator was 1 mm when measured from each end of the positive electrode and 0.75 mm when measured from each end of the negative electrode. The content of PVdF in the separator was as shown in Table 13 below.

  A thin non-aqueous electrolyte secondary battery having a thickness of 3 mm, a width of 40 mm, and a height of 70 mm was assembled in the same manner as described in Example 50 except that such an electrode group was used.

Comparative Example 13
A thin nonaqueous electrolyte secondary battery was assembled in the same manner as Comparative Example 12 described above, except that the lengths of the positive electrode, the negative electrode, and the separator were aligned and the positive electrode, the negative electrode, and the separator were not protruded. .

  About the obtained secondary battery of Examples 50-54, 56-57, and Comparative Examples 12-13, after charging for 5 hours to 4.2V with a charging current of 300 mA, a charge / discharge cycle test for discharging to 2.7 V with 300 mA was performed. It was carried out in an atmosphere at 20 ° C. On the other hand, for the secondary battery of Example 55, a charge / discharge cycle test was performed in an atmosphere of 20 ° C., which was charged to 4.0 V at a charging current of 300 mA for 5 hours and then discharged to 2.7 V at 300 mA. Table 13 below shows the discharge capacity (initial capacity) at the first cycle in each charge / discharge cycle test and the capacity retention ratio (relative to the initial capacity) at 300 cycles.

  Moreover, about the secondary battery of Examples 50-54, 56-57, and Comparative Examples 12-13, after charging for 5 hours to 4.2V with a charging current of 300 mA, it measured the discharge capacity when discharged to 2.7V at 2C. Then, the ratio of the discharge capacity at 2C to the initial capacity is calculated, and the result is also shown in Table 13 below as the capacity retention ratio at the 2C discharge rate. On the other hand, for the secondary battery of Example 55, after charging to 4.0 V at a charging current of 300 mA for 5 hours, the discharge capacity when discharged to 2.7 V at 2 C was measured, and the capacity retention rate at the 2 C discharge rate was determined. The results are shown in Table 13 below.

Further, the secondary batteries of Examples 50 to 57 and Comparative Examples 12 to 13 were dropped on a concrete floor from a height of 90 cm in a charged state, and the presence or absence of an internal short circuit was examined from the battery voltage change and impedance change. This is also shown in Table 13 below.

  As is apparent from Table 13, the secondary of Examples 50 to 57, in which the content of the polymer having adhesiveness in the separator is 10% by weight or less and the end of the separator protrudes as compared with the positive electrode and the negative electrode. It can be seen that there are no batteries that cause an internal short circuit when dropped, and that the initial capacity, the capacity maintenance ratio after 300 cycles, and the capacity maintenance ratio when discharged at 2C are high.

  On the other hand, the secondary battery of Comparative Example 12 in which the content of the polymer having adhesiveness in the separator exceeds 10% by weight has no battery that causes an internal short circuit when dropped. It can be seen that the capacity, the capacity maintenance ratio after 300 cycles, and the capacity maintenance ratio when discharged at 2C are lower than those of Examples 50-57. Further, the secondary battery of Comparative Example 13 in which the content of the polymer having adhesiveness in the separator exceeds 10% by weight and the ends of the positive electrode, the negative electrode, and the separator are aligned is short-circuited when dropped. In addition, it can be seen that the initial capacity, the capacity maintenance ratio after 300 cycles, and the capacity maintenance ratio when discharged at 2C are lower than those of Examples 50-57.

Sectional drawing which shows an example of the 1st, 2nd nonaqueous electrolyte secondary battery concerning this 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. The perspective view which shows another example of the electrode group integrated in the 1st, 2nd nonaqueous electrolyte secondary battery concerning this invention. The side view which shows another example of the electrode group integrated in the 1st, 2nd nonaqueous electrolyte secondary battery concerning this invention. Sectional drawing which shows an example of the 3rd nonaqueous electrolyte secondary battery concerning this invention. The expanded sectional view which shows the B section of FIG. Sectional drawing which shows an example of the 4th nonaqueous electrolyte secondary battery concerning this invention. The expanded sectional view which shows the C section of FIG. Sectional drawing which shows an example of the 7th nonaqueous electrolyte secondary battery concerning this invention. The D section of FIG. 10 is an expanded sectional view.

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 part, 9 ... High having adhesiveness Molecule, 21 ... exterior material, 22 ... electrode group, 31 ... exterior material, 32 ... electrode group, 41 ... exterior material, 42 ... electrode group, 49a ... adhesive layer, 49b ... adhesive layer.

Claims (10)

An electrode group having a structure in which a positive electrode and a negative electrode are wound in a flat shape through a separator therebetween,
A non-aqueous electrolyte impregnated in the electrode group;
The electrode group is housed, and comprises an exterior material having a thickness of 300 μm or less containing metal,
The non-aqueous electrolyte secondary battery, wherein the electrode group has a shape in which a surface where the laminated structure is exposed satisfies the following formula (1).
0.9 ≦ L ₂ / L ₁ ≦ 1.2 (1)
In the formula (1), L ₂ is the thickness of the most multilayered portion in the region excluding the curved laminated region in the surface, and L ₁ is a layer in the end portion of the region excluding the curved laminated region. The thickness of the end portion whose number is equal to L ₂ . An electrode group having a structure in which a laminate composed of a positive electrode, a negative electrode, and a separator is bent twice or more;
A non-aqueous electrolyte impregnated in the electrode group;
The electrode group is housed, and comprises an exterior material having a thickness of 300 μm or less containing metal,
The non-aqueous electrolyte secondary battery, wherein the electrode group has a shape in which a surface where the laminated structure is exposed satisfies the following expression (2).
0.9 ≦ L ₄ / L ₃ ≦ 1.2 (2)
In the formula (2), L ₄ is the thickness of the outermost multilayer portion in the region excluding the folded laminated region, and L ₃ is the layer in the end portion of the region excluding the folded laminated region. The thickness of the end portion whose number is equal to the L ₄ .   The non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein a gap between the electrode groups is filled with an adhesive polymer that holds the non-aqueous electrolyte.   The non-aqueous electrolyte secondary battery according to claim 3, wherein the adhesive polymer is gelled by holding the non-aqueous electrolyte. The non-aqueous electrolyte secondary battery according to claim 1, wherein the separator is 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, wherein the separator is made of at least one material selected from polyolefin and cellulose. The non-aqueous electrolyte secondary according to claim 1, wherein the negative electrode includes a carbonaceous material having a graphite crystal having a (002) plane spacing d ₀₀₂ of 0.34 nm or less. battery.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the negative electrode contains lithium titanium oxide.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the exterior material is formed of a laminate film including a resin layer and having a thickness of 300 μm or less. The non-aqueous electrolyte secondary battery according to claim 1, wherein the exterior material containing metal is a film exterior material having a function of blocking moisture .

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