JP2010199035A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery which is expected to exhibit high safety by preventing expansion of an electrode body and conducting stable charge even when gas is generated within the electrode body in overcharge. <P>SOLUTION: A rectangular parallelopiped-shaped electrode body 10 is obtained by winding a positive plate 102, a separator 101, and a negative plate 100 and pressing the wound body from the side. A gas generating plate 14 containing a gas generating material (at least one of lithium carbonate and lithium oxalate) generating gas in a high voltage region of 4.5V or higher and a conductive agent is fixed with a PPS tape 15 and arranged in the center of the principal surface of the outermost periphery of the electrode body 10. The electrode body 10 is covered with a laminate outer packaging 20 together with a polymer electrolyte and internal sealing is conducted. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a non-aqueous electrolyte secondary battery such as a polymer battery, and more particularly to a technique for improving safety by preventing battery deformation induced by heat generated during overcharge.

  In recent years, with the widespread use of portable electronic devices such as mobile phones, mobile PCs, portable audio devices, digital cameras, and personal digital assistants (PDAs), the demand for non-aqueous electrolyte secondary batteries that are thin, lightweight, and high capacity has increased rapidly. Yes. In particular, a typical non-aqueous electrolyte secondary battery, a lithium ion polymer secondary battery (also referred to as a polymer battery or a laminate battery, hereinafter referred to as a “polymer battery”) including a lithium polymer electrolyte and a laminate outer package. It is flexible and can be formed very thin, and can be made extremely thin and lightweight while having a large capacity. For this reason, it is widely used as an optimal power source for the above-described small electronic devices.

  In general, a polymer battery is formed by laminating a belt-like positive electrode plate and a negative electrode plate with a separator interposed therebetween, and winding and crushing the same into a substantially rectangular parallelepiped wound body (electrode body). It has a power generation element impregnated with liquid. A tab (also called a current collecting terminal or an electrode tab) is attached to the electrode body with respect to the core body of each electrode plate. The power generation element is covered with a laminate outer package with each tab exposed to the outside. At this time, the inside of the laminate outer package is surely sealed by thermocompression treatment, particularly in the vicinity of the tab, so that the electrode body and the electrolytic solution do not leak to the outside.

  In polymer batteries, due to the chemical characteristics of the polymer electrolyte, when the battery is overcharged due to a failure or malfunction of the charger, gas is generated inside the electrode body at a high temperature, and the electrode body may be deformed due to the effect. is there. FIG. 5 is a schematic cross-sectional view showing the state of the electrode body that has been deformed by the generation of such gas. In the example shown in this figure, when the electrode body is deformed, the positive electrode plate bulges outside so as to be separated from the separator and the negative electrode plate. Therefore, the distance between the two electrode plates is increased in the region where the bulge occurs. It will be difficult to exchange lithium ions, etc. that have been performed smoothly. This induces a phenomenon in which current flows locally in the electrode body, which may increase the risk of the battery being further heated. Although FIG. 5 shows an example in which the positive electrode plate bulges, the negative electrode plate may bulge and the bipolar plates may bulge, respectively.

In addition, since the polymer battery has a soft laminate outer package, the outer package is softened when the battery is overheated as described above, and the shape of the battery is easily deformed.
Here, Patent Document 1 intends to use a gas at a high temperature of a battery by containing a substance that forms an interfering substance that prevents ion conduction at the inside of the polymer electrolyte, the inside of the electrode, or the interface between the polymer electrolyte layer and the electrode. A technique is disclosed in which overheating is prevented by increasing the internal resistance to inhibit current flow.

JP 11-260346 A JP-A-9-306510

  However, in the above-described conventional technology, a certain effect of inhibiting the flow of current can be obtained by generating gas in the internal space of the battery, but it is caused by local contact of the electrode plate while suppressing expansion of the electrode body. The effect of preventing overheating cannot be obtained. For this reason, even if gas is generated inside the electrode body during overcharging, it is difficult to obtain stable battery performance by maintaining a structure in which the electrode plates are appropriately stacked via the separator.

Patent Document 2 describes a technique in which carbonate is disposed on the outer peripheral portion of an electrode body inside a battery to absorb moisture mixed in the battery and to activate a current interruption mechanism. However, this technique does not suppress the expansion of the electrode body of the polymer battery including the polymer electrolyte.
Thus, at present, there is room for improvement in suppressing expansion of the electrode body of the polymer battery and using the battery safely and satisfactorily.

  The present invention has been made in view of the above problems, and enables stable charging by preventing expansion of the electrode body even when gas is generated inside the electrode body during overcharging. Accordingly, an object is to provide a non-aqueous electrolyte secondary battery that can be expected to exhibit excellent safety.

  In order to achieve the above object, the present invention includes an electrode body in which a positive electrode plate and a negative electrode plate are laminated via a separator, and the positive electrode plate is formed into a rectangular parallelepiped shape with the positive electrode plate as an outermost surface. A non-aqueous electrolyte secondary battery that is sealed together with an electrolyte inside a laminate outer body, wherein the electrode is arranged such that a gas generating plate containing a gas generating material that generates a gas during overcharge is in contact with the positive electrode plate. It was set as the structure interposed between at least one of the both main surfaces of a body, and the laminate exterior body.

Here, the gas generating plate can be configured to include a gas generating substance and a conductive agent.
In the gas generating plate, a conductive agent may be added at a ratio of 2 wt% or more and 15 wt% or less with respect to the weight of the gas generating plate.
The battery is a lithium ion polymer battery, and the gas generating substance is a substance that generates gas in a high voltage range of 4.5 V or higher, and is included in the gas generating plate in a solid state. It can also be configured.

The gas generating substance may include at least one of lithium carbonate and lithium oxalate.
The gas generating substance may be arranged at a plurality of locations on the outermost surface of the electrode body.
In the gas generating plate, the gas generating substance may be added in a range of 2 wt% to 25 wt% with respect to the battery weight.

  Alternatively, in the gas generating plate, the gas generating substance may be added in a range of 5 wt% to 25 wt% with respect to the battery weight.

  In the nonaqueous electrolyte secondary battery of the present invention having the above-described configuration, a gas generating plate is interposed between the laminate outer package and the electrode assembly, and a predetermined high voltage region (lithium ion polymer secondary battery) is obtained during overcharge. In the case of a secondary battery, for example, when a load of 4.5 V or more is applied to the battery, gas is generated from the gas generating plate. The pressure of this gas accumulates between the laminate outer package and the outermost surface of the electrode body, and acts to press the electrode body inward in the thickness direction from its main surface. As a result, even if gas is generated inside the electrode body during overcharging as in the conventional case, the electrode body is prevented from expanding outward, and the positive electrode plate, the separator, and the negative electrode plate always remain inside the electrode body. A densely stacked state is maintained. As a result, it is possible to prevent a phenomenon in which current concentrates and flows locally within the electrode body, and it is possible to prevent overheating of the battery and to take good safety measures.

In addition, since the overheating of the battery is effectively prevented by using the gas generating plate as described above, the problem that the laminate outer body is softened at a high temperature and the form of the battery is distorted can be avoided well.
In the present invention, a rectangular parallelepiped electrode body is provided as a constituent element, but the `` cuboid shape '' and the `` rectangular main surface '' referred to here are broader than mathematical definitions and can be said to be substantially a rectangular parallelepiped shape. If included, it shall be included. The electrode body formed by crushing the belt-shaped wound body has a strict shape with respect to these definitions because the side surface is curved, but in the present invention, such a shape also falls under the “cuboid shape”. To do.

1 is a diagram showing a configuration of a polymer battery 1 according to Embodiment 1. FIG. 1 is a set diagram showing an internal configuration of a polymer battery 1. FIG. It is a figure which shows the arrangement | positioning position of an electrode body and a gas generation board. It is typical sectional drawing for demonstrating the effect of this invention. It is typical sectional drawing for demonstrating the problem at the time of the conventional gas generation | occurrence | production.

The form for implementing this invention is demonstrated using an example.
The following embodiment is merely an example for explaining the configuration, operation, and effect of the present invention in an easy-to-understand manner, and the present invention is limited to the following form in addition to its essential features. is not.
<Embodiment 1>
FIG. 1 is a partially cutaway view showing a configuration of a lithium ion polymer battery 1 (hereinafter simply referred to as “battery 1”), which is Embodiment 1 of the nonaqueous electrolyte secondary battery of the present invention. In this figure, the laminated exterior body is partially cut away to show the inside. FIG. 2 is an assembled view showing a state when the electrode body is disposed on the laminate outer package.

As shown in FIG. 1, the battery 1 is housed in a laminated outer package 20 in a state where a flat electrode body 10 is impregnated with a polymer electrolyte.
The electrode body 10 is obtained by pressing a spiral electrode body obtained by winding a positive electrode plate 102 and a negative electrode plate 100 via a separator 101 (see FIG. 4) flatly from a side surface into a thin rectangular parallelepiped shape. In addition, the electrode body 10 is good also as a structure which laminates | stacks a strip-shaped positive-negative electrode both via a separator. In either case, the positive electrode plate 102 is formed on the outermost surface (or outermost periphery).

The positive electrode plate 102 is formed by applying a predetermined positive electrode active material (positive electrode material) capable of inserting and extracting lithium to an aluminum foil as a core. The cathode material, for example _{LiCoO 2, LiNiO 2, LiMnO 4} , LiMnO 2, LiNi 1-x O 2 (0 <x <1), LiNi 1-x Co x O 2 (0 <x <1), LiNi x Mn _y Co _z O ₂ (0 <x, y, z <1), lithium composite oxides such as LiFePO ₄ , and phosphate compounds having an olivine structure are desirable. Other examples include oxides such as titanium oxide, vanadium oxide, and manganese dioxide, disulfides such as iron disulfide, titanium disulfide, and molybdenum sulfide, and conductive polymers such as polyarinin and polythiophene. Two or more kinds of positive electrode materials may be mixed and used.

The negative electrode plate 100 is formed by applying a predetermined negative electrode active material (negative electrode material) capable of inserting and extracting lithium to a copper foil as a core. Examples of the anode material include carbon materials such as graphite and difficult (easy) graphitizable carbon, titanium oxides such as LiTiO ₂ and TiO ₂ , Mg, B, Al, Ga, Si, Ge, Sn, Pb, Bi, A metal element such as Zn or Ag, or a metalloid element is used. Examples of alloys or compounds of these metal elements or metalloid elements include SiB ₄ , SiB ₆ , Ni ₂ Si, TiSi ₂ , MoSi ₂ , CoSi ₂ , NiSi ₂ , CaSi ₂ , CrSi ₂ , Cu ₅ Si, and FeSi _{2. , MnSi 2, NbSi 2, TaSi} 2, VSi 2, WSi 2, ZnSi 2, SiC, Si 3 N 4, Si 2 N 2 O, SiO x (0 <x ≦ 2), SnO x (0 <x ≦ 2 _{), SnSiO 3, LiSiO, LiSnO} , Mg 2 Sn or tin-cobalt-containing alloys. Two or more kinds of these negative electrode materials may be mixed and used.

As the separator 101, a microporous film formed of a polyolefin material such as polypropylene or polyethylene can be selected. In addition to this, a resin having a high melting point may be mixed or laminated in order to ensure shutdown response. The thickness can be 0.03 mm.
In addition, each size width (z direction length) of the positive electrode plate 102, the negative electrode plate 100, and the separator 101 is set to increase in the same order. This is considered to ensure that the area of the negative electrode plate is larger than that of the positive electrode plate, so that the lithium ions from the positive electrode plate are sufficiently absorbed by the negative electrode plate during charging, and the generation of dendrites (dendritic crystals) is suppressed. It is a thing.

On the positive electrode plate 102 and the negative electrode plate 100, strip-like tabs (positive electrode tab 11 and negative electrode tab 12) for taking out electric power to the outside at one end of the spiral electrode body in the winding direction are formed by resistance welding or the like. To be attached. The positive electrode tab 11 is made of an aluminum material, and the negative electrode tab 12 is made of a nickel material.
As shown in FIGS. 1 and 2, films (so-called tab resins 30, 30) made of a heat-welding resin material are inserted into the portions of the tabs 11, 12 that overlap with the strip 200 before the thermocompression bonding. The The tab resins 30, 30 are softened at the time of the thermocompression bonding and enter the gaps between the surfaces of the tabs 11, 12 and the inner surface of the strip 200, so that the battery 1 can be reliably sealed inside.

The positive electrode plate 102 is laminated on the outermost periphery (surface) of the electrode body 10 so as to be oriented. In the substantially rectangular parallelepiped shape, a sheet-like gas generating plate 14 is fixed by attaching a PPS tape 15 to the center of one main surface. As the electrolyte impregnated in the electrode body 10, a gel polymer electrolyte which is a non-aqueous electrolyte is used.
The gas generating plate 14 is a main characteristic part of the present invention, and a small amount of a conductive agent (powdered acetylene black) is mixed with a predetermined gas generating substance (powdered lithium carbonate or lithium oxalate) and pressed. It is a plate processed into a pellet shape. The PPS (polyphenylene sulfide) tape 15 is a heat-resistant resin tape and is used to securely attach and fix the gas generating plate 14 to the central area of the main surface of the electrode body 10.

  In FIG. 2, the tape 15 is disposed so as to completely cover the gas generating plate 14. However, the present invention is not limited to this, and the gas generating plate 14 can be partially fixed as long as it can be fixed to the surface of the positive electrode plate 102. You may stick to. Further, the tape 15 can be made of a porous material. Such a device is suitable for generating the gas of the gas generating plate 14 between the laminate outer package 20. Further, the material of the tape 15 is not limited to PPS, and various heat-resistant materials can be used.

  As the gas generating material, when the present invention is applied to a lithium ion polymer secondary battery, the voltage between the positive electrode plate 102 and the negative electrode plate 100 during charging is a high voltage region (for example, 4.5 V or more). A substance that generates gas when it reaches a range of about 12 V is preferred. For example, at least one of lithium carbonate and lithium oxalate can be used. In addition, at least one element selected from Co, Mn, Ni, Al, Sn, Bi, Li, and Mo, oxide, carbonate, nitrate, sulfate, oxalate, phosphate, borate, acetic acid One or more combinations of salts can be used. The gas generating plate 14 maintains a solid state in a voltage range of less than 4.5V.

As the conductive agent, at least one of carbon black and ketjen black can be used in addition to acetylene black.
The electrode body 10 is impregnated with a polymer electrolyte obtained by dispersing an electrolyte salt and an additive in a predetermined solvent.
Examples of the electrolyte salt include LiClO ₄ , LiCF ₃ SO ₃ , LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , LiN (CF ₂ CF ₃ SO ₂ ) _{2 and the} like. You may use these in mixture of 2 or more types.

  Solvents include cyclic carbonates such as EC, PC and BC, carboxylic acid esters such as γ-BL and γ-VL, chain carbonates such as DMC, EMC, DEC and DNBC, MA, MP and pivalic acid methyl ester. Such as carboxylic acid esters such as 1,2-dimethoxyethane, cyclic ethers such as tetrahydrofuran and 1,4-dioxane, amide compounds such as N, N dimethylformamide and N-methyloxazolidinone, and sulfur compounds such as sulfolane And room temperature molten salts such as 1-ethyl-3-methylimidazolium tetrafluoroborate and 1-butylpyridinium tetrafluoroborate. It is desirable to use a mixture of two or more of these.

  As additives, VC, VEC, SUCAH (succinic anhydride), MAAH (maleic anhydride), 1,3-propane sultone, 1,3-propene sultone, ES (ethylene sulfite), VS (divinyl sulfone), VA (vinyl acetate), VP (vinyl pivalate), t-AV (tert-amylbenzene), t-BB (tert-butylbenzene), 1,3-DOX (1,3-dioxane), 1,3-DOXL ( 1,3-dioxolane), catechol carbonate, CHB (cyclohexylbenzene), BP (biphenyl), 4-fluoro-1,3-dioxolan-2-one, 4,5-difluoro-1,3-dioxolan-2-one 4-chloro-1,3-dioxolan-2-one, 4-trifluoromethyl-1,3-dioxolane 2-one and the like.

Subsequently, the polymer component of the polymer electrolyte is preferably an alkylene oxide polymer or a fluorine polymer such as a polyvinylidene fluoride-hexafluoropropylene copolymer.
A method for producing a polymer electrolyte includes, for example, a monomer having an unsaturated double bond such as acryloyl group, methacryloyl group, vinyl group, and allyl group, and a monomer having a cationic polymerizable cyclic ether group such as epoxy, oxetane, and formal. An example is a method of polymerizing a monomer after being contained in the above-described non-aqueous electrolyte. The timing for polymerizing the monomer may be after the battery is assembled.

  Monomers having an unsaturated double bond include acrylic acid, methyl acrylate, ethyl acrylate, ethoxyethyl acrylate, methoxyethyl acrylate, ethoxyethoxyethyl acrylate, polyethylene glycol monoacrylate, ethoxyethyl methacrylate, ethoxyethyl methacrylate, polyethylene glycol Monomethacrylate, N, N-diethylaminoethyl acrylate, glycidyl acrylate, allyl acrylate, diethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, polypropylene glycol diacrylate, polypropylene glycol dimethacrylate, polyalkylene glycol Dimethacrylate, polyalkylene glycol dimethacrylate, trimethylol propane alkoxylate triacrylate, pentaerythritol alkoxylate tetraacrylate, can be used pentaerythritol alkoxylate tetraacrylate. As the monomer having a cyclic ether group, a copolymer of methyl methacrylate and (3-ethyl-3-oxetanyl) methyl acrylate, tetraethylene glycol bisoxetane, polyvinyl formal, or the like can be used.

  Among these materials, a monomer having an unsaturated double bond can be polymerized by heat, ultraviolet light, electron beam or the like, but a polymerization initiator may be added in order to make the reaction proceed effectively. Examples of the polymerization initiator include organic compounds such as benzoyl peroxide, t-butyl peroxycumene, lauroyl peroxide, di-2-ethylhexyl peroxydicarbonate, t-butyl peroxypivalate, and t-hexyl peroxyisopropyl monocarbonate. A peroxide can be illustrated.

A monomer having a cyclic ether group can be polymerized by heat or charge / discharge with Li ⁺ or a small amount of H ⁺ in the nonaqueous electrolyte.
As another method for producing a polymer electrolyte, there is a method in which a polymer component is dissolved in a high temperature non-aqueous electrolyte and cooled. The polymer component in this case may be any component as long as it is in a gel state containing a nonaqueous electrolyte at room temperature and is stable as a battery material. Examples of such a polymer component include polymers having a ring such as polyvinyl pyridine and poly-N-vinyl pyrrolidone, acrylic derivative polymers such as polymethyl acrylate and polyethyl acrylate, fluorine-based compounds such as polyvinyl fluoride and polyvinylidene fluoride. Examples thereof include resins, polyvinyl alcohol polymers such as polyvinyl acetate and polyvinyl alcohol, and halogen-containing polymers such as polyvinyl chloride and polyvinylidene chloride. Moreover, a mixture with said polymer etc., a modified body, a derivative, a random copolymer, a graft copolymer, a block copolymer, etc. may be sufficient. The weight average molecular weight of these polymer components is usually in the range of 10,000 to 5,000,000.

  When a monomer having an unsaturated bond is polymerized by heat, ultraviolet light, electron beam, etc. to form a polymer electrolyte, its added amount ((non-aqueous solvent + electrolyte salt + chelate compound + additive of the present invention + monomer (necessary If present, the proportion of the polymerization initiator and other additives)) in the mass) is preferably 1.5 to 15% by mass, more preferably 3 to 7% by mass, and further preferably 4.5 to 5.%. 8% by mass.

When using a polymerization initiator, the addition amount is preferably 500 ppm to 1% by mass, more preferably 1000 ppm to 5000 ppm, based on the total electrolytic mass.
When using the compound which has cyclic ether groups, such as polyvinyl formal, the addition amount becomes like this. Preferably it is 0.5-5 mass%, More preferably, it is 1-2.5 mass%, More preferably, it is 1.5-2. 0% by mass.

When a polymer is dissolved in a high temperature non-aqueous electrolyte and cooled to prepare a polymer electrolyte, the addition amount is preferably 10 to 35% by mass, more preferably 15 to 30% by mass, Preferably it is 20-25 mass%.
The package 20 is composed of an aluminum laminate sheet (thickness: 100 μm) having a three-layer laminated structure of polypropylene layer (PP layer) / aluminum foil (Al layer) / polypropylene layer (PP layer). As shown in FIG. 2, the overall shape is a belt-like body 200, and a cup molding portion 20 a having a recess 201 for housing the electrode body 10 and a sheet portion having a flat inner main surface 202 along the longitudinal direction. 200b is provided continuously. The peripheral edge of the belt-like body 200 is a thermocompression bonding part L1 to L6 having a width of about 2 mm. With the sheet part 200b folded back to the cup molding part 200a, the PP layers on the surface of each thermocompression bonding part L1 to L6 are connected to each other. Three sides are sealed by thermocompression bonding. The PP layer is an example of a resin layer, and for example, a nylon layer may be used.

  As shown in FIG. 1, the electrode body 10 is sandwiched between the cup molding part 200a and the sheet part 200b of the strip 200 during the three-way sealing, and the positive electrode tab 11 and the negative electrode tab 12 are set to the outside. In the exposed state, the top seal portion 20T (the thermocompression bonding portions L3 and L6) and the side seal portions (the thermocompression bonding portions L1 and L4, and the thermocompression bonding portions L2 and L5) around the rectangular main surface of the electrode body 10 are exposed. Part). By this internal sealing process, the belt-like body 200 becomes the exterior body 20. The side seal portion is raised in the thickness direction of the electrode body 10 (z direction in FIG. 2) and becomes the bent side portions 20R and 20L.

As an example of the size of the battery 1, the short side (length in the y direction) 34 mm × long side (length in the z direction) 50 mm × thickness (length in the x direction) can be 3.8 mm. An example of the width (length in the z direction) of the top seal portion 20T is 4 mm. The weight of the battery 1 is about 14 g, for example.
In the battery 1 having the above configuration, the gas generating plate 10 is interposed between the laminate outer package 20 (specifically, the inner main surface 202 thereof) and the electrode body 10, so that Deformation is suppressed, and the safety is greatly improved as compared with the prior art. FIG. 4 is a schematic partial cross-sectional view for explaining the effect obtained by the battery 1.

  If the battery 1 is overcharged for any reason, such as a charger failure or malfunction during charging, reaction heat is generated when highly reactive lithium metal is deposited on the negative electrode, or the solvent is decomposed on the positive electrode. The battery temperature rises by generating Joule heat. At this time, as shown in FIG. 5, since the gas is generated from the inside of the electrode body, the distance between the electrode plates of the positive electrode plate and the negative electrode plate facing each other through the separator is increased. It becomes difficult to exchange lithium ions between the two plates. This reduces the effective electrode area inside the electrode body and increases the local rate. This further induces the lithium metal precipitation reaction and the generation of Joule heat as described above, leading to an increase in battery temperature, which also causes a decrease in battery safety.

In addition, since the polymer battery employs a soft laminate outer package, when the battery becomes hot due to the reaction heat or the Joule heat during overcharging, the laminate outer package softens and the battery is likely to be deformed. There is also.
On the other hand, in the battery 1, when the overcharge voltage reaches a high voltage range of 4.5 V or more, the gas generating substance in the gas generating plate 14 is decomposed as shown in FIG. Is generated. Thereby, gas is mainly generated between the laminate outer package 20 and the electrode assembly 10. Since the gas derived from the gas generating plate 14 is locally filled between the outermost periphery of the laminate outer package 20 and the electrode assembly 10, the pressure of the gas presses the electrode assembly 10 inward in the thickness direction and restrains it. Acts like Thus, as shown in FIG. 5, even if gas is generated inside the electrode body 10 (the portion of the positive electrode plate in contact with the separator) in the overcharged state, the positive electrode plate 102 moves outward in the thickness direction of the electrode body 10. The positive electrode plate 102, the separator 101, and the negative electrode plate 100 are always kept in a densely stacked state. Therefore, inside the electrode body 10, it is prevented that a large current flows locally in the electrode body 10 and the temperature becomes high, and the battery 1 can be charged safely. In addition, since the battery 1 is effectively prevented from becoming high temperature by such a principle, the problem that the laminate outer package 20 is softened at high temperature and the shape of the battery is distorted can be avoided well.

Note that the gas generating plate 14 does not cause a reaction to generate gas unless it is brought into contact with the positive electrode plate 102. Desirably, the gas generating plate 14 is brought into contact with the core (aluminum foil core) of the positive electrode plate 12.
Further, when lithium carbonate or lithium oxalate is used as the gas generating material, these compounds do not have conductivity. Therefore, it should be noted that it is necessary to add a conductive agent into the gas generating plate 14 in order to perform the gas generating reaction.

  In order to obtain such an effect, the gas generated by the gas generating plate 14 needs to stay at a certain position inside the battery. Therefore, a battery using a liquid electrolyte (electrolyte) with high fluidity is used. Not applicable. This is because the liquid electrolyte does not have the same viscosity as the polymer electrolyte, so that the gas generated from the gas generating plate diffuses inside the battery, and the force (restraint force) that presses the electrode body is small.

In general solid electrolytes, no gas is originally generated inside the electrode body. Therefore, it should be noted that the present invention needs to be applied to a battery using at least a gel polymer electrolyte.
<Other embodiments>
In the battery 1 of the first embodiment, as shown in FIG. 1, the gas generating plate 14 is disposed at the center of the main surface at the outermost periphery of the electrode body 10. However, the present invention is not limited to this configuration, and can be disposed at one or a plurality of locations so as to be in contact with the positive electrode plate 102 at an arbitrary position on the outermost periphery of the electrode body 10.

  Here, the battery 1A shown in FIG. 3B shows the internal configuration of the battery 1A in which the gas generating plate 14 is provided on the center side of the lower main surface of the electrode body 10A, contrary to the battery 1 of the first embodiment. FIG. In this drawing, only the inside of the battery is selectively illustrated, and the exterior body shows only the inner contours of the cup molding part 200a, the concave part 201, and the sheet part 200b. In this configuration, the gas generating plate 14 is disposed between the inner main surface 202 of the sheet portion 200b and the electrode body 10A (position close to the tabs 11 and 12) (illustration of the tape 15 is omitted). Even with a battery having such a configuration, high safety can be exhibited during overcharge as in the battery 1 of the first embodiment.

  In the battery 1B shown in FIG. 3C shown below, gas generating plates 14A and 14B are arranged at the center of both main surfaces of the electrode body 10B, respectively. In the configuration of FIG. 3C, the electrode body 10B receives the pressing force of the gas generated from the gas generating plates 14A and 14B from both main surfaces thereof, so that the deformation of the electrode body can be reduced as much as possible and the inside of the electrode body can be reduced. Adhesion can be further improved. As a result, overheating of the battery during overcharge can be more effectively prevented, and excellent safety can be exhibited.

In addition, the gas generating plate may be distributed and disposed at a plurality of locations with respect to the electrode body 10 (for example, disposed at the center and four corners of each main surface). Also in this case, it should be noted that the gas generating plate should be brought into contact with the outermost positive electrode plate of the electrode body.
<Performance confirmation experiment>
In order to confirm the performance of the present invention, the batteries of Examples and Comparative Examples were produced as follows, and predetermined experiments were performed.
(Preparation of positive electrode plate)
LiCoO ₂ is mixed with 95 wt%, acetylene black as a conductive agent is 2.5 wt%, and polyvinylidene fluoride (PVdF) as a binder is mixed at a ratio of 2.5 wt%, and NMP (N-methylpyrrolidone) is mixed therewith. In addition, a slurry was formed. This was apply | coated on the aluminum foil (12 micrometer film thickness) (application amount 380g / m < ² >). Then, after drying this and removing NMP, it pressure-molded (filling density 3.70g / cc) and obtained the positive electrode plate.

(Preparation of negative electrode plate)
95 wt% of artificial graphite, 1 wt% of carboxymethylcellulose (CMC) as a binder, 1 wt% of styrene butadiene rubber (SBR), and 3 wt% of acetylene black as a conductive agent are mixed, and water is added to this to slurry. I made it. This slurry was applied (165 g / m ² ) on a copper foil (thickness 8 μm). Thereafter, this was dried to remove moisture and subjected to pressure molding (filling density 1.60 g / cc) to obtain a negative electrode plate.
(Production of gas generating plate)
95 wt% of lithium carbonate or lithium oxalate powder and 5 wt% of acetylene black (conductive agent) were mixed and filled in a PP resin frame. And it pressurized at 100 kg / cm < ² > and shape | molded in the pellet form. Thereafter, this was cut and polished to obtain a plate-like gas generating plate having a height of 40 mm, a width of 10 mm, and a thickness of 0.5 to 2.0 mm.
(Preparation of non-aqueous electrolyte)
As a non-aqueous electrolyte, methyltrimethyl acetate (MTMA) shown in the following chemical formula 1, ethylene carbonate (EC), and propylene carbonate (PC) were mixed in the same order at a mass ratio of 50:30:20. LiPF ₆ as an electrolyte salt was dissolved and added to 1.0 M (mol / L), and 5% by weight of tripropylene glycol diacrylate as a monomer and a polymerization initiator (trade name: Perbutyl (registered trademark) PV) , Manufactured by Nippon Oil & Fats Co., Ltd.) was added at 3000 ppm each to prepare a pregel.

（注液前電池の作製）
所定の寸法にスリットした正極版及び負極板の各々に対し、集電タブを溶接した。これらをポリエチレン製の微多孔膜からなるセパレータ（厚み１２μｍ）を挟んで巻回し、厚さ３．８ｍｍ、幅３４ｍｍ、高さ５０ｍｍの電極体を作製した。ガス発生板を電極体の最外周中央部にＰＰＳテープで固定した後、カップ成型したラミネートに収納し、注液口を除いて熱シールすることで注液前電池を作製した。

(Preparation of battery before injection)
A current collecting tab was welded to each of the positive electrode plate and the negative electrode plate slit to a predetermined size. These were wound with a separator (thickness 12 μm) made of a polyethylene microporous film interposed therebetween, and an electrode body having a thickness of 3.8 mm, a width of 34 mm, and a height of 50 mm was produced. The gas generating plate was fixed to the outermost peripheral central portion of the electrode body with a PPS tape, then housed in a cup-molded laminate, and heat-sealed except for the liquid injection port to prepare a pre-injection battery.

At this time, the batteries of Examples 1 to 24 were obtained by changing the arrangement quantity and position or the thickness of the gas generating plates. Here, the configuration example 1 refers to the battery 1 of the first embodiment, the configuration example 2 refers to the battery 1A in FIG. 3B, and the configuration example 3 refers to the battery 1B in FIG.
(Battery preparation method)
After injecting the electrolytic solution from the liquid injection port, the impregnation treatment was performed, the inclusion liquid was gelled by heating, and then the liquid injection port was heat-sealed to perform charging and discharging, thereby completing a battery with an output of 750 mAh.

（考察）
表１の実験結果が示すように、いずれの実施例１〜２４も、比較例に比べて良好な性能を有していることが確認できた。 In addition, as a comparative example battery (Comparative Example 1), a battery was prepared in the same manner as in the above example except that no gas generating plate was used.
The battery weights of the examples were set so as to be within the range of 13.8 to 16.9 g.
(Overcharge safety test)
About each produced said battery, it charged until the voltage reached 12.0V by the constant current 0.6lt (450mA). Thereafter, the battery was overcharged at a constant voltage of 12.0 V for a total of 15 hours (23 ° C.). A further test was not performed for those in which smoke generation was confirmed, and a similar test was performed by increasing the constant current value in increments of 0.1 lt (75 mA) for those in which smoke generation was not confirmed. The maximum current rate at which no smoke was confirmed was confirmed as the limiting current value. The results are shown in Table 1.

(Discussion)
As the experimental result of Table 1 shows, it has confirmed that any Examples 1-24 had favorable performance compared with the comparative example.

In Comparative Example 1, as the overcharge progressed, gas was generated inside the electrode body and expanded in the thickness direction. When charging proceeds in a state in which the positive electrode plate and the negative electrode plate cannot face each other due to the deformation of the electrode body, the battery reaction is concentrated locally. As a result, it is considered that smoke was generated at a relatively low voltage in Comparative Example 1.
On the other hand, in the structural examples 1 and 2, gas is intentionally generated at the position where the gas generating plate interposed between the laminate outer package and the electrode assembly is disposed. The pressure accompanying the generation of gas is applied in the direction opposite to the direction of the force of the electrode body expanding along the thickness direction, so that the deformation of the electrode body is suppressed, and as a result, the separation between the positive electrode plate and the negative electrode plate is reduced. Is prevented. Therefore, it is considered that in both Configuration Examples 1 and 2, local battery reaction is unlikely to occur as in Comparative Example 1, and the overcharge limit rate can be increased accordingly.

  Further, comparing the configuration examples 1 and 2, it was confirmed that the configuration example 1 was more effective than the configuration example 2. In the configuration example 2, since the gas generating substance is arranged on the tab side, the tab is pulled and the electrode body is slightly deformed as the laminate on the tab side expands. For this reason, it is thought that the effect as the structural example 1 was not acquired. Still, the configuration example 1 shows a sufficiently higher effect than the comparative example, and it can be confirmed that the configuration example 1 has some performance.

On the other hand, in the configuration example 3, since the gas pressure is applied from the upper and lower sides in the thickness direction of the battery toward the electrode body, the effect of suppressing the deformation of the electrode body is further remarkable. For this reason, the safety of the battery has been dramatically improved. Note that the higher the value of the overcharge limit rate, the higher the safety of the battery. For this reason, the higher one is desirable.
In addition, when the difference of the used gas generating substance was compared, it turned out that the effect of the battery of Examples 13-24 using lithium oxalate is large compared with the battery of Examples 1-12 using lithium carbonate. This is thought to be due to the large amount of gas generated per weight.

  As described above, the superiority of the present invention over the conventional example could be confirmed.

  The present invention can be used for a lithium ion polymer battery as a main power source of, for example, a mobile phone, a portable audio, a digital camera, and a personal digital assistant (PDA).

1, 1A, 1B Lithium ion polymer secondary battery (non-aqueous electrolyte secondary battery)
10, 10A, 10B Electrode body 11 Positive electrode tab 12 Negative electrode tab 14, 14A, 14B Gas generation plate 15 PPS tape 20 Exterior body 20R, 20L Side seal part 20T Top seal part 30 Tab resin 200 Strip-like body 200a Cup molding part 200b Sheet part 201 Concave part 202 Inner main surface L1-L6 Thermocompression bonding part

Claims (8)

A positive electrode plate and a negative electrode plate are laminated via a separator, and have an electrode body molded in a rectangular parallelepiped shape with the positive electrode plate as an outermost surface, and the electrode body is sealed inside a laminate outer package together with a polymer electrolyte. A non-aqueous electrolyte secondary battery comprising:
A gas generating plate containing a gas generating material that generates gas at the time of overcharge is interposed between at least one of the two main surfaces of the electrode body and the laminate outer package so as to be in contact with the positive electrode plate. A non-aqueous electrolyte secondary battery. The non-aqueous electrolyte secondary battery according to claim 1, wherein the gas generating plate includes a gas generating substance and a conductive agent. The non-aqueous electrolyte secondary battery according to claim 2, wherein in the gas generating plate, the conductive agent is added at a ratio of 2 wt% to 15 wt% with respect to the weight of the gas generating plate. The battery is a lithium ion polymer battery;
The gas generating substance is a substance that generates gas in a high voltage range of 4.5 V or higher, and is included in the gas generating plate in a solid state. A non-aqueous electrolyte secondary battery according to claim 1. The non-aqueous electrolyte secondary battery according to claim 1, wherein the gas generating material includes at least one of lithium carbonate and lithium oxalate. The non-aqueous electrolyte secondary battery according to claim 1, wherein the gas generating substance is disposed at a plurality of locations on the outermost surface of the electrode body. The non-aqueous electrolyte 2 according to any one of claims 1 to 6, wherein the gas generating material is added in a range of 2 wt% to 25 wt% with respect to the battery weight. Next battery. The non-aqueous electrolyte secondary according to claim 1, wherein the gas generating material is added in a range of 5 wt% to 25 wt% with respect to a battery weight. battery.

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