JP2010146808A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery for vehicle mounting in which binding property of a mixture layer is secured to obtain a high capacity. <P>SOLUTION: The lithium ion secondary battery 60 has a battery can 41. In the battery can 41, a wound group 5 in which a positive electrode plate and a negative electrode plate are wound around through a separator 21 is housed. The positive electrode plate has a positive electrode mixture layer 2 containing lithium manganate of a positive electrode active material formed on both sides of a positive electrode current collector sheet 1. The negative electrode plate has a negative electrode mixture layer 12 coated on the both sides of a negative electrode current collector sheet 11. The negative electrode mixture layer 12 contains a non-graphite carbon material of the negative electrode active material and SBR particles of a rubber binder. The thickness per single side of the negative electrode mixture layer 12 is set to be 50 μm or less. Since SBR particles are used for the binder, the ratio of the binder occupied in the negative electrode mixture layer 12 can be reduced. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a non-aqueous electrolyte secondary battery, and more particularly, to a positive electrode plate on which a positive electrode mixture layer containing an active material capable of occluding and releasing lithium ions is applied to a current collector and a current collector that stores lithium ions. A vehicle-mounted non-aqueous electrolyte comprising an electrode group in which a negative electrode plate coated with a negative electrode mixture layer containing a releasable active material is disposed via a separator, a non-aqueous electrolyte, and a battery container The present invention relates to a secondary battery.

  Among non-aqueous electrolyte secondary batteries, lithium ion secondary batteries that use the absorption and release of lithium ions have high energy density, so they are for consumer use such as power supplies for portable devices such as VTR cameras, notebook computers, and mobile phones. As widely used. On the other hand, due to the emergence of environmental problems such as global warming, reduction of carbon dioxide emissions from automobiles is required. Electric vehicles (EV) powered by electric energy that does not emit carbon dioxide, Development of a hybrid vehicle (HEV) that regenerates the generated energy and uses it as part of the power, and a plug-in hybrid vehicle (PHEV) that can be driven by electric power using a household power source is proceeding at a rapid pace. . Lithium ion secondary batteries are also attracting attention as in-vehicle power supplies for EV, HEV, and PHEV.

  Conventionally, in a lithium ion secondary battery, a mixture layer containing an active material capable of occluding and releasing lithium ions is applied to the positive and negative electrode current collectors, respectively. In addition to the active material, the composite layer contains a binder (binder) in order to improve the binding property of the active material and the binding property between the current collector and the composite material layer. In general, polyvinylidene fluoride (hereinafter abbreviated as PVDF) or the like is used as a binder. In addition, lithium-containing composite oxides are used for the positive electrode active material, and for the negative electrode active material, graphite carbon materials such as natural graphite and artificial graphite, non-graphitizable carbon materials, graphitizable carbon materials, etc. Non-graphitic carbon material is used. When a graphite carbon material is used for the negative electrode active material, the filling property of the composite layer is high due to high crystallinity and high true density, and the capacity per unit weight is larger than that of the non-graphite carbon material ( Since the irreversible capacity is small, the capacity of the lithium ion secondary battery can be increased. On the other hand, when non-graphitic carbon material is used, lithium ion diffusion and occlusion / release reactions are likely to occur during charge / discharge, and the volume change of crystals accompanying charge / discharge is small compared to graphite carbon material, A lithium ion secondary battery having high input / output characteristics and high cycle characteristics can be obtained. However, non-graphitic carbon materials have low crystallinity and low true density, so the filling property of the composite layer is low, and the irreversible capacity is large, so it is difficult to increase the capacity of the lithium ion secondary battery. .

  In an in-vehicle lithium ion secondary battery (for example, a capacity of 3 Ah or more), input characteristics and cycle characteristics are important as well as output characteristics. For example, in HEV, a motor is used for power assist when starting or accelerating. Therefore, a lithium ion secondary battery used as a power source is required to have high output characteristics capable of discharging a large current in a short time. On the other hand, since HEV regenerates and uses energy generated when a vehicle is decelerated, high input characteristics capable of charging a large current generated in a short time are also required. Since these characteristics depend on the negative electrode active material, it is preferable to use a non-graphitic carbon material having high input / output characteristics for the negative electrode active material of the in-vehicle lithium ion secondary battery. However, since EV and PHEV use a motor even during steady running, a high-capacity lithium ion secondary battery is required. As described above, the use of non-graphitic carbon material for the negative electrode active material increases the capacity. Becomes difficult. Regarding the increase in capacity of lithium ion secondary batteries using non-graphitic carbon materials, a coexistent of non-graphitic carbon materials consisting of at least one of non-graphitizable carbon materials and non-graphitizable carbon materials and graphite carbon materials The technique used as a negative electrode active material is disclosed (for example, refer patent document 1). Further, in consumer lithium-ion secondary batteries (for example, with a capacity of less than 3 Ah), there is a technology that uses a rubber binder instead of PVDF as a binder. The rubber binder here is a binder obtained by polymerizing at least one monomer mixture having a double bond site.

JP 7-192724 A

  However, the technique of Patent Document 1 is a technique for increasing the battery capacity by coexisting a non-graphitic carbon material with a graphite carbon material having a larger capacity per unit weight than the non-graphitic carbon material. It is not a technology that increases the effective capacity of the material itself. In other words, a technique for increasing the capacity of the non-aqueous electrolyte secondary battery by increasing the effective capacity of the non-graphitic carbon material itself has not been known so far. In addition, although rubber binders are used as negative electrode binders for consumer lithium ion secondary batteries, examples of use as negative electrode binders for in-vehicle lithium ion secondary batteries where input / output characteristics have been more important than capacity characteristics so far Has not been reported. Furthermore, in the in-vehicle lithium ion secondary battery, it is also important to secure the binding property of the composite material layer in order to suppress peeling of the composite material layer due to vibration, impact, or the like.

  An object of the present invention is to provide an in-vehicle non-aqueous electrolyte secondary battery capable of securing the binding property of the mixture layer and increasing the capacity, in view of the above-mentioned cases.

  In order to solve the above problems, the present invention is capable of absorbing and releasing lithium ions in a current collector and a positive electrode plate coated with a positive electrode mixture layer containing an active material capable of inserting and extracting lithium ions. A non-graphite carbon material active material and a negative electrode plate coated with a negative electrode composite layer containing a rubber binder are disposed via a separator, a non-aqueous electrolyte infiltrating the electrode group, and the electrode An on-vehicle nonaqueous electrolyte secondary battery comprising: a group; and a battery container containing the nonaqueous electrolyte solution.

  In the present invention, by including a rubber binder in the negative electrode mixture layer, the binding property of the negative electrode mixture layer can be ensured even if the proportion of the rubber binder in the negative electrode mixture layer is reduced, and the ratio of the rubber binder Since the ratio of the active material is relatively increased by the amount reduced, the capacity can be increased for in-vehicle use.

  In this case, the rubber binder is preferably in the form of particles having a particle size in the range of 0.1 to 1.0 μm. At this time, the particle diameter may be in the range of 0.1 to 0.3 μm. The negative electrode mixture layer may contain a thickener for viscosity adjustment blended at the time of coating. At this time, the thickener can be carboxymethylcellulose. Moreover, the negative electrode mixture layer can be applied to both sides of the current collector, the thickness per side can be 50 μm or less, and the battery capacity can be 3.5 Ah or more.

  According to the present invention, by including a rubber binder in the negative electrode mixture layer, the binding property of the negative electrode mixture layer can be ensured even if the proportion of the rubber binder in the negative electrode mixture layer is reduced. Since the ratio of the active material is relatively increased by reducing the ratio, the effect that the capacity can be increased for in-vehicle use can be obtained.

  Hereinafter, embodiments of a cylindrical lithium ion secondary battery to which the present invention is applied will be described with reference to the drawings.

  As shown in FIG. 1, the columnar lithium ion secondary battery 60 of the present embodiment includes a nickel-plated iron-made bottomed cylindrical battery can 41 serving as a battery container. The battery can 41 accommodates a wound group (electrode group) 5 in which the positive electrode plate and the negative electrode plate are wound.

  On the upper side of the wound group 5, a ribbon-like positive electrode lead 3 made of aluminum is exposed. One end of the positive electrode lead 3 is bonded to the positive electrode current collector sheet 1 constituting the positive electrode plate, and the other end is bonded to the lower surface of the positive electrode terminal 51 disposed on the upper side of the wound group 5. The positive electrode terminal 51 is made of aluminum and has a disk shape, and also serves as a battery lid that seals the opening of the battery can 41. A polyethylene insulator 31 is disposed between the lower surface of the positive electrode terminal 51 and the upper end surface of the wound group 5 in order to insulate between the wound group 5 and the positive electrode terminal 51 (to prevent short circuit). The positive electrode terminal 51 incorporates a safety valve (not shown) for cleaving as the battery internal pressure increases to release the pressure inside the battery.

  On the other hand, a ribbon-like negative electrode lead 13 made of nickel is exposed below the winding group 5. One end of the negative electrode lead 13 is bonded to the negative electrode current collector sheet 11 constituting the negative electrode plate, and the other end is bonded to the inner bottom surface of the battery can 41. For this reason, the negative electrode plate and the battery can 41 are electrically connected, and the battery can 41 also serves as the negative electrode terminal. An insulator 31 is disposed between the inner bottom surface of the battery can 41 and the lower end surface of the winding group 5 in order to insulate between the winding group 5 and the inner bottom surface of the battery can 41.

  In the wound group 5, a belt-like positive electrode plate and a negative electrode plate are wound in a cross-sectional spiral shape via a separator 21. In this example, a polyethylene porous membrane is used for the separator 21, and the thickness is set to 25 μm and the size in the width direction intersecting the longitudinal direction is set to 58 mm. The outer peripheral surface of the wound group 5 is provided with an insulating coating (not shown) over the entire periphery.

(Positive electrode plate)
In the positive electrode plate constituting the wound group 5, a positive electrode mixture containing a positive electrode active material is applied to both surfaces of the positive electrode current collector sheet 1 to form a positive electrode mixture layer 2. In this example, an aluminum foil having a thickness of 20 μm is used as the positive electrode current collector sheet 1. In the positive electrode mixture, lithium manganate as a positive electrode active material, a mixture of graphite and acetylene black as a conductive material, and polyvinylidene fluoride (hereinafter abbreviated as PVDF) as a binder have a weight of 80:10:10. Mixed in proportion. When the positive electrode mixture is applied to the positive electrode current collector sheet 1, a positive electrode mixture slurry is prepared in which each material is dispersed substantially uniformly in a dispersion solvent N-methylpyrrolidone (hereinafter abbreviated as NMP). . The positive electrode mixture slurry is applied substantially uniformly on both surfaces of the positive electrode current collector sheet 1 by a roll coating method. After drying at 120 ° C., they are integrated by pressing, and the positive electrode mixture layers 2 are formed on both surfaces of the positive electrode current collector sheet 1, respectively. In this example, the thickness of the positive electrode plate (the portion where the positive electrode mixture layer 2 is formed) is pressed to 90 μm, the size in the width direction is set to 54 mm, and the length is set to 450 mm. That is, the thickness of the positive electrode mixture layer 2 is (90-20) / 2 = 35 μm per one side of the positive electrode current collector sheet 1. Further, the positive electrode current collector sheet 1 that is not coated with the positive electrode mixture layer 2 is exposed at one end in the longitudinal direction of the positive electrode plate (the end located on the winding center side of the winding group 5). The positive electrode lead 3 is joined to the exposed part.

(Negative electrode plate)
On the other hand, in the negative electrode plate, a negative electrode mixture containing a negative electrode active material is applied to both surfaces of the negative electrode current collector sheet 11 to form a negative electrode mixture layer 12. In this example, a copper foil having a thickness of 10 μm is used as the negative electrode current collector sheet 11. The negative electrode composite material includes a non-graphite carbon material as a negative electrode active material, acetylene black as a conductive material, styrene-butadiene copolymer rubber (hereinafter abbreviated as SBR) particles as a rubber binder, and a thickener as a thickener. Carboxymethylcellulose (hereinafter abbreviated as CMC) is mixed in a weight ratio of 91: 4: 4: 1.

  In this example, a non-graphitizable carbon material is used as the non-graphitic carbon material of the negative electrode active material. The non-graphitizable carbon material, for example, carbonizes an organic polymer material such as furfuryl alcohol resin at 300 to 700 ° C. in an inert gas stream, and then raises the temperature to 900 to 1500 ° C. It can produce by the method of hold | maintaining for 0 to 30 hours. The rubber binder used for forming the negative electrode mixture layer 12 is obtained by polymerizing a mixture of one or more monomers having a double bond site. In this example, the SBR particles of the rubber binder have a number average particle diameter adjusted to 0.15 μm. The number average particle diameter can be adjusted, for example, by classification. When the negative electrode mixture is applied to the negative electrode current collector sheet 11, a negative electrode mixture slurry is produced in which the respective materials are dispersed substantially uniformly in the water of the dispersion solvent. The negative electrode mixture slurry is applied substantially uniformly on both surfaces of the negative electrode current collector sheet 11 by a roll coating method. After drying at 120 ° C., they are integrated by pressing, and the negative electrode mixture layers 12 are formed on both surfaces of the negative electrode current collector sheet 11. In this example, the thickness of the negative electrode plate (the portion where the negative electrode mixture layer 12 is formed) is pressed to 80 μm, the size in the width direction is set to 56 mm, and the length is set to 500 mm. That is, the thickness of the negative electrode mixture layer 12 is (80−10) / 2 = 35 μm per one side of the negative electrode current collector sheet 11. Further, an exposed portion of the negative electrode current collector sheet 11 to which the negative electrode mixture layer 12 is not applied is formed at one end portion in the longitudinal direction of the negative electrode plate (end portion located on the outer peripheral side of the wound group 5). The negative electrode lead 13 is joined to the exposed portion.

Moreover, as shown in FIG. 1, the positive electrode terminal 51 which also serves as a battery lid is crimped and fixed to the upper part of the battery can 41 via an insulating gasket. For this reason, the inside of the lithium ion secondary battery 60 is sealed. In addition, a nonaqueous electrolyte solution (not shown) is injected into the battery can 41. The non-aqueous electrolyte includes phosphorus hexafluoride as a lithium salt in a mixed solvent in which ethylene carbonate (EC), dimethyl carbonate (DMC) and diethyl carbonate (DEC) are mixed at a volume ratio of 1: 1: 1. A solution in which 1 mol / liter of lithium acid (LiPF ₆ ) is dissolved is used. The obtained lithium ion secondary battery 60 is formed with a diameter of 18 mm and a length of 65 mm.

(Action etc.)
Next, the operation and the like of the lithium ion secondary battery 60 of the present embodiment will be described.

  In the lithium ion secondary battery 60 of the present embodiment, a non-graphitizable carbon material of non-graphitic carbon material is used as the negative electrode active material, and SBR particles of rubber binder are used as the binder. In the PVDF generally used as a binder, positive and negative electrode composites and the like are bound mainly by entanglement of molecular chains. In contrast, the rubber binder exhibits binding properties mainly on the particle surface. By making the particle size of the rubber binder smaller than the particle size of the active material, the conductive material, etc., the surface area is increased and the binding property is improved. For this reason, even if the amount of the rubber binder of the negative electrode mixture is reduced, the binding property of the active material and the conductive material and the binding property of the negative electrode mixture layer 12 and the negative electrode current collector sheet 11 can be ensured.

  In addition, by using a rubber binder as the binder of the negative electrode mixture layer 12, since the binding property can be ensured even if the ratio of the rubber binder is reduced, the ratio of the negative electrode active material can be relatively increased. For this reason, the battery capacity can be improved. Surprisingly, it has been found that the use of a rubber binder reduces the amount of irreversible capacity of the non-graphitic carbon material used as the negative electrode active material. The reason for this is not clear, but one reason is that the distribution of the rubber binder in the negative electrode mixture layer 12 is different from the distribution of PVDF. By reducing the amount of irreversible capacity formed of the non-graphitic carbon material, the effective capacity increases, so that the battery capacity can be improved.

  Furthermore, in the lithium ion secondary battery 60 of the present embodiment, the number average particle diameter of the SBR particles used as the rubber binder is adjusted to 0.15 μm. By reducing the particle size, the surface area can be increased and the binding property can be improved. When the particle size of the rubber binder is larger than 1.0 μm, the particles of the rubber binder tend to settle in the dispersion solution in which the negative electrode mixture is dispersed, and contact between the active material and the conductive material in the negative electrode mixture layer 12 Is easily inhibited by the rubber binder particles. On the other hand, when the particle size of the rubber binder is less than 0.1 μm, the surface area increases, but the rubber binder tends to aggregate in the dispersion solution. Therefore, by setting the particle size of the rubber binder in the range of 0.1 to 1.0 μm, it is possible to increase the density of the active material and the conductive material while ensuring the dispersibility and binding property of the rubber binder. Thereby, since electroconductivity improves, the input-output characteristic of the lithium ion secondary battery 60 can be improved. If the dispersibility in the dispersion solution is improved and further improvement of input / output characteristics is taken into consideration, it is preferable to adjust the particle size of the rubber binder to a range of 0.1 to 0.3 μm.

  Furthermore, in the lithium ion secondary battery 60 of the present embodiment, the thickness of the positive electrode mixture layer 2 applied to both surfaces of the positive electrode current collector sheet 1 is set to 35 μm per side, and the negative electrode current collector The thickness of the negative electrode mixture layer 12 applied to both surfaces of the sheet 11 is set to 35 μm per one surface. That is, the positive and negative electrode mixture layers 2 and 12 each have a thickness of 50 μm or less per side of the positive and negative electrode current collector sheets 1 and 11. If the thickness of each of the positive and negative electrode mixture layers 2 and 12 per side is greater than 50 μm, the transmission of lithium ions may be inhibited in the thickness direction of the positive and negative electrode mixture layers 2 and 12. When the thickness of each of the positive and negative electrode mixture layers 2 and 12 is 50 μm or less, it is easy to exchange lithium ions. Further, by limiting the thickness of the positive and negative electrode mixture layers 2 and 12, the facing area of the positive and negative electrode plates can be increased in the battery per fixed volume. Thereby, the input / output characteristics of the lithium ion secondary battery 60 can be improved.

  Furthermore, in the lithium ion secondary battery 60 of this embodiment, the binding properties of the positive and negative electrode mixture layers 2 and 12 are ensured by using a rubber binder as described above. For this reason, for example, the problem that the positive and negative electrode composite material layers 2 and 12 are peeled off from the positive and negative electrode current collector sheets 1 and 11 due to vibration or impact when mounted on the vehicle can be suppressed. The lithium ion secondary battery 60 that has high input / output characteristics and high capacity characteristics and also prevents the positive and negative electrode mixture layers 2 and 12 from being peeled off even during vibration is, for example, an in-vehicle power supply such as EV, HEV, or PHEV. Can be suitably used. As a vehicle-mounted power supply, for example, a plurality of lithium ion secondary batteries 60 can be connected in series and parallel.

  In the present embodiment, an example of using a non-graphitizable carbon material of non-graphitic carbon material alone as a negative electrode active material has been shown, but the present invention is not limited to this, and lithium ions are occluded and released. Any non-graphitic carbon material may be used. An easily graphitizable carbon material may be used instead of the non-graphitizable carbon material. This graphitizable carbon material is, for example, carbonized at 300 to 700 ° C. in an inert gas stream, and then heated to 900 to 1500 ° C. and held at the ultimate temperature for 0 to 30 hours. It can produce by the method to do. Further, a non-graphitizable carbon material and a non-graphitizable carbon material may be used in combination, and the shape of the carbon material is not particularly limited. In addition to the non-graphitic carbon material, the negative electrode mixture can contain graphite in a proportion of 30% by weight or less of the non-graphitic carbon material. Compared with non-graphite carbon materials, graphite is less susceptible to lithium ion diffusion and occlusion / release reactions during charge / discharge, so if it exceeds 30% by weight, the charge / discharge characteristics of the lithium ion secondary battery 60 will be impaired. It becomes.

  In the present embodiment, the example in which the proportion of the negative electrode active material in the negative electrode mixture layer 12 is 91% by weight is shown, but the present invention is not limited to this. If the proportion of the negative electrode active material is less than 90% by weight, the amount of the active material becomes too small and the battery capacity is reduced. Conversely, if the proportion is more than 99.5% by weight, the binder amount is relatively reduced and the binding property is impaired. For this reason, the reliability of the battery is lowered. Therefore, the ratio of the negative electrode active material is preferably in the range of 90 to 99.5% by weight.

  Furthermore, in this embodiment, although SBR particle | grains were illustrated as a rubber binder contained in the negative mix layer 12, this invention is not limited to this. Examples of the rubber binder that can be used in addition to the SBR particles include SBR modified products, acrylonitrile-butadiene copolymer rubber and modified products thereof, acrylic rubber and modified products thereof, and the like. There is no restriction | limiting in particular also about the dispersion solvent used when producing the negative mix slurry containing a rubber binder, For example, water, methanol, ethanol, and these mixed solvents can be used. In the case of a rubber binder, when an aqueous solvent rather than an organic solvent such as methanol is used as a dispersion solvent, the hydrophobic rubber binder aggregates and is difficult to disperse in the aqueous solvent. In order to suppress aggregation of the rubber binder and improve dispersibility, a hydrophilic functional group such as a carboxyl group may be introduced on the surface of the rubber binder. Further, a surfactant may be added to improve the dispersibility. In this case, an antifoaming agent can also be added in order to suppress foaming during coating due to the addition of a surfactant. Examples of the surfactant include n-sodium dodecyl sulfate (SDS), and examples of the antifoaming agent include n-octanol and polysiloxane.

  Furthermore, in the present embodiment, an example in which the negative electrode mixture layer 12 contains 4% by weight of SBR particles of a rubber binder is shown, but the present invention is not limited to this, and 0.5 to 10% by weight The range can be adjusted. When the amount of the rubber binder is more than 10% by weight, the amount of the active material is relatively decreased, and thus the capacity of the lithium ion secondary battery 60 is decreased. On the other hand, when the amount is less than 0.5% by weight, it is difficult to secure the binding property, and the reliability of the lithium ion secondary battery 60 is impaired.

  Furthermore, in this embodiment, the example in which the positive and negative electrode mixture slurry is applied to the positive and negative electrode current collector sheets 1 and 11 by the roll coating method is shown, but the present invention is not limited to this. Examples of the method for applying the positive and negative electrode mixture slurry to the positive and negative electrode current collecting sheets 1 and 11 include a slit die coating method, in addition to the roll coating method. Moreover, NMP and water can be used as a solvent of a dispersion solution. Furthermore, in this embodiment, although CMC of the thickener was illustrated for viscosity adjustment at the time of apply | coating the negative mix slurry to the negative electrode collector sheet 11, this invention is not limited to this. Examples of thickeners other than CMC include CMC derivatives, polyvinylpyrrolidone (PVP) and derivatives thereof, and polyvinyl alcohol (PVA) and derivatives thereof. Moreover, you may make it apply | coat a negative mix slurry, without using a thickener. Furthermore, in this embodiment, although the example which makes the negative electrode compound material layer 12 contain acetylene black of a electrically conductive material was shown, the electrically conductive material which can be used by this invention is not limited to this. The conductive material is not particularly limited as long as it can assist the transmission of the potential generated with the occlusion and release of lithium ions to the negative electrode current collector sheet 11, and is usually used for a lithium ion secondary battery. A conductive material can be used.

  In the present embodiment, lithium manganate is exemplified as the positive electrode active material, but the present invention is not limited to this, and any material that can occlude and release lithium ions may be used. Examples of the positive electrode active material that can be used in the present invention include lithium cobaltate, lithium nickelate, lithium iron phosphate, and lithium composite oxide (lithium oxide containing two or more selected from cobalt, nickel, and manganese). Can be mentioned. Alternatively, a lithium transition metal double oxide in which a part of lithium or a transition metal element in a crystal is substituted or doped with another transition metal element such as Fe, Co, Ni, Cr, Al, or Mg may be used. Further, there is no particular limitation on the crystal structure, and the crystal structure may be any of spinel type, layered type, and olivine type. Further, the conductive material and binder contained in the positive electrode mixture layer 2 are not particularly limited, and materials usually used for lithium ion secondary batteries can be used. For example, graphite and acetylene black can be used as the positive electrode conductive material, and PVDF and fluororubber can be used as the binder. Of course, a rubber binder may be used for the binder of the positive electrode mixture layer 2.

  Furthermore, in the present embodiment, the positive electrode current collector sheet 1 is exemplified by an aluminum foil having a thickness of 20 μm, and the negative electrode current collector sheet 11 is exemplified by a copper foil having a thickness of 10 μm. However, the present invention is not limited thereto. . Electrons generated by the occlusion and release reaction of lithium ions in the positive and negative electrode mixture layers 2 and 12 can be transmitted to the positive and negative electrode leads 3 and 13, respectively, and contact with the non-aqueous electrolyte solution and occlusion and release of lithium ions as an active material. As long as the material does not significantly deteriorate due to the above, it is usually possible to use a conductive material used for the positive and negative electrode plates of a lithium ion secondary battery. The shape of the positive and negative electrode current collector sheets 1 and 11 is not particularly limited, such as a film shape or a perforated plate.

Furthermore, in the present embodiment, the non-aqueous electrolyte solution in which 1 mol / liter of lithium salt LiPF ₆ is dissolved in a mixed solvent of EC, DMC, and DEC is exemplified. The electrolytic solution is not particularly limited. As an organic solvent, what is normally used for a lithium ion secondary battery may be used. For example, carbonate organic solvents such as propylene carbonate (PC) and methyl ethyl carbonate (MEC) may be used, and these organic solvents may be used alone or in combination. Even lithium salt, as long as it is used in conventional lithium ion secondary battery, for _{example, LiClO 4, LiAsF 6, LiBF} 4, LiB (C 6 H 5) 4, CH 3 SO 3 Li, CF 3 SO ₃ Li or the like or a mixture thereof can be used. Needless to say, the mixing ratio of the organic solvent and the content of the lithium salt are not particularly limited.

  Furthermore, in this embodiment, although the polyethylene porous membrane was illustrated as the separator 21, this invention is not limited to this. It is a porous sheet that can pass lithium ions moving through the non-aqueous electrolyte while isolating the positive electrode plate and the negative electrode plate, as long as it is a material that does not deteriorate significantly by contact with the non-aqueous electrolyte, What is normally used for a lithium ion secondary battery can be used. For example, a polypropylene porous film etc. can be mentioned. Moreover, although the polyethylene board was illustrated as the insulator 31, it does not deteriorate significantly by contact with a non-aqueous electrolyte, and between the winding group 5 and the positive electrode terminal 51 and the winding group 5 and the battery can 41 (inner bottom surface). There is no particular limitation as long as it can be electrically insulated from each other.

  In the present embodiment, the wound columnar lithium ion secondary battery 60 is exemplified, but the present invention is not limited to this. Moreover, although the comparatively small lithium ion secondary battery 60 was illustrated, this invention is not restrict | limited to this. In other words, the present invention is not limited to the capacity, size, shape, etc. of the battery, but it is preferable to set the battery capacity to approximately 3.5 Ah or more for the on-vehicle lithium ion secondary battery. . The battery capacity can be set according to the content of the positive and negative electrode active materials, the area of the positive and negative electrode mixture layers 2 and 12, and the like. Moreover, as a battery other than the winding type, for example, a stacked type battery in which a positive and negative electrode plate in which an active material layer is coated on a current collector is stacked via a separator can be exemplified. The battery structure may be other than the lithium ion secondary battery 60 having a structure in which the positive electrode terminal 51 is caulked and sealed to the battery can 41 described above. As an example of such a structure, a battery in a state where positive and negative external terminals penetrate through the battery lid and are pressed through the shaft core in the battery container can be mentioned.

  Next, examples of the lithium ion secondary battery 60 manufactured according to the present embodiment will be described. In addition, it describes together about the lithium ion secondary battery of the comparative example produced for the comparison.

(Example 1, Example 2)
In Example 1, a battery A was produced as a lithium ion secondary battery 60 using a non-graphitizable carbon material of non-graphitic carbon material as a negative electrode active material. The non-graphitizable carbon material was prepared by holding a furfuryl alcohol resin in a nitrogen stream at a temperature of 500 ° C. for 5 hours, then raising the temperature to 1200 ° C. and performing a heat treatment for 1 hour. In Example 2, a battery B was manufactured as a lithium ion secondary battery 60 using a non-graphitizable carbon material, a non-graphitizable carbon material, as the negative electrode active material. The soot graphitizable carbon material was produced by holding coal pitch in a nitrogen stream at a temperature of 500 ° C. for 5 hours, then raising the temperature to 1400 ° C. and heat treating for 1 hour.

(Comparative Example 1 and Comparative Example 2)
In Comparative Example 1, a lithium ion secondary battery was produced in the same manner as in Example 1 except that the composition of the negative electrode mixture was changed. That is, the battery C as a lithium ion secondary battery using a composite material obtained by mixing a non-graphitizable carbon material as a negative electrode active material, acetylene black as a conductive material, and PVDF as a binder in a weight ratio of 91: 4: 5. Was made. In Comparative Example 2, a battery D was produced as a lithium ion secondary battery in the same manner as in Comparative Example 1 except that graphite was used as the negative electrode active material. That is, the negative electrode composite layers of Comparative Example 1 and Comparative Example 2 contain PVDF instead of the rubber binder, and do not contain CMC as a thickener.

(Evaluation)
For the lithium ion secondary batteries (Batteries A to D) of each Example and Comparative Example, each battery was charged to 4.1 V at 250 mA and the initial charge capacity was measured, and then discharged to 2.7 V at 250 mA for the first time. The discharge capacity was measured. The ratio of the initial discharge capacity to the initial charge capacity at this time was calculated as the initial charge / discharge efficiency. Then, after charging under the above-mentioned charging conditions and measuring the charge capacity, the battery was discharged to 2.7 V at a current value of 250 mA, 500 mA, 1500 mA, and 3000 mA, and the discharge capacity was measured. The charge / discharge efficiency was determined from the ratio of the discharge capacity to the charge capacity at each current value. Further, after charging under the above-mentioned charging conditions, it was left for one week. After that, according to the conditions of the Japanese Electric Vehicle Standard (JEVS D713: 2003 Power Density and Input Density Test Method for Sealed Nickel / Hydrogen Batteries for Hybrid Electric Vehicles) Characteristics were evaluated. Moreover, the discharge capacity after repeating the charging / discharging cycle between 4.1V-2.7V 1000 times at 3000 mA was measured, and the capacity maintenance ratio was determined from the ratio of the discharge capacity after 1000 cycles to the initial discharge capacity. Table 1 shows the measurement results of initial charge / discharge efficiency, charge / discharge efficiency at different current values, input density, output density, and capacity retention rate. In Table 1, “different current” indicates the charge / discharge efficiency at different current values.

  As shown in Table 1, in the battery C of Comparative Example 1 and the battery D of Comparative Example 2 using PVDF as the binder, the initial charge and discharge efficiencies were 65% and 68%, respectively. On the other hand, in the battery A of Example 1 and the battery B of Example 2 using rubber binder SBR particles as the binder, the initial charge and discharge efficiencies are 73% and 76%, respectively, and the rubber binder is used instead of PVDF. It has been found that the initial charge / discharge efficiency of the lithium ion secondary battery 60 is improved by using. In addition, the charging / discharging efficiency measured by changing the current value shows 96% or more at any discharge current value in each of the examples and comparative examples, and the capacity maintenance ratio shows almost the same value in each of the examples and comparative examples. It was. From this, it was found that even when a rubber binder is used as the binder, charge / discharge efficiency and cycle characteristics can be secured. Furthermore, the battery C of Comparative Example 1 and the battery D of Comparative Example 2 both showed an input density of 2500 W / kg and an output density of 2700 W / kg, whereas the battery A of Example 1 and Example In all the batteries B, the input density was 3300 W / kg and the output density was 3500 W / kg. From this, it is considered that both the input density and the output density are improved by using a non-graphite carbon material that is liable to cause diffusion or occlusion / release reaction of lithium ions during charge and discharge as the negative electrode active material. From the above, by using a non-graphite carbon material as the negative electrode active material and using a rubber binder as the binder, the input / output characteristics are improved while ensuring the charge / discharge efficiency and the cycle characteristics, and the high performance of the lithium ion secondary battery 60 is achieved. It became clear that the capacity could be increased.

  The present invention contributes to the manufacture and sale of non-aqueous electrolyte secondary batteries in order to provide a vehicle-mounted non-aqueous electrolyte secondary battery that can secure the binding property of the mixture layer and increase the capacity. Have industrial applicability.

It is a front view which partially fractures and shows the cylindrical lithium ion secondary battery of embodiment to which this invention is applied.

Explanation of symbols

1 Positive current collector sheet (current collector)
2 Positive electrode mixture layer 5 Winding group (electrode group)
11 Negative electrode current collector sheet (current collector)
12 Negative electrode mixture layer 21 Separator 60 Cylindrical lithium ion secondary battery (non-aqueous electrolyte secondary battery)

Claims (6)

A positive electrode plate in which a positive electrode mixture layer containing an active material capable of occluding and releasing lithium ions is applied to a current collector, and an active material of a non-graphitic carbon material capable of occluding and releasing lithium ions and a rubber binder are included in the current collector An electrode group in which a negative electrode plate coated with a negative electrode mixture layer is disposed via a separator;
A non-aqueous electrolyte infiltrating the electrode group;
A battery container containing the electrode group and the non-aqueous electrolyte;
A non-aqueous electrolyte secondary battery for vehicle use, comprising:   2. The non-aqueous electrolyte secondary battery according to claim 1, wherein the rubber binder has a particle size in a range of 0.1 μm to 1.0 μm.   The non-aqueous electrolyte secondary battery according to claim 2, wherein the rubber binder has a particle size in a range of 0.1 μm to 0.3 μm.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the negative electrode mixture layer contains a viscosity-adjusting thickener mixed at the time of application.   The non-aqueous electrolyte secondary battery according to claim 4, wherein the thickening material is carboxymethyl cellulose.   The negative electrode composite material layer is applied to both surfaces of the current collector, has a thickness of 50 μm or less per one surface, and has a battery capacity of 3.5 Ah or more. A nonaqueous electrolyte secondary battery according to 1.

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