JP4727021B2 - Electrode and non-aqueous battery using the same - Google Patents

Description

【００４１】
（電極の評価）
得られた図１または図２に示す積層構造を有する負極Ａ１〜Ａ３を密閉容器中でプロピレンカーボネートに浸漬したまま、室温から１５０℃まで約２℃／ｍｉｎで昇温していった。Ａ１及びＡ２は内温が１４５℃に到達した瞬間にマイクロスフェアーが一度に発泡し、Ａ１ではＭＣＭＢがばらばらに剥がれ落ちた状態、Ａ２ではＭＣＭＢの大部分が銅箔から剥がれて浮き上がった状態、となった。Ａ３は内温が１２５℃に到達した瞬間にマイクロスフェアーが一度に発泡し、ＭＣＭＢがばらばらに剥がれ落ちた状態となった。室温まで冷却後、発泡が起きた電極Ａ２を取り出し、合剤層上に１０ｇの分銅を置き、該分銅と銅箔の非被覆部との間での抵抗を測定したところ、発泡前の状態の約１５０倍の値を示した。
【００４２】
【発明の効果】
上記評価例は、本発明の熱膨張性マイクロカプセルを含む電極が、電解液との接触状態で所定温度に達すると、電極活物質と集電体との間で瞬間的に非導通状態が形成され、導通状態で進行する電池反応の熱暴走防止に極めて効果的であることを示すものと理解される。
【図面の簡単な説明】
【図１】本発明の一実施例にかかる電極の積層構造の模式図。
【図２】本発明の別の実施例にかかる電極の積層構造の模式図。
【図３】本発明の一実施例にかかる非水系電池の積層構造の模式図。
【図４】本発明の別の実施例にかかる非水系電池の積層構造の模式図。
【符号の説明】
１：電極合剤層（１Ａ：負極合剤層、１Ｂ：正極合剤層）
１ａ：電極活物質（１ａａ：負極活物質）
２：集電体（２Ａ：負極中、２Ｂ：正極中）
３：熱膨張性マイクロカプセル
４：中間シート状層（固体電解質またはセパレータ）
３０：マイクロカプセル層
Ａ：負極
Ｂ：正極[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrode with improved safety for the purpose of avoiding accidents associated with abnormalities such as a sudden temperature rise inside the battery due to overdischarge or overcharge in a non-aqueous battery, particularly a lithium ion secondary battery, and the electrode The present invention relates to a non-aqueous battery including
[0002]
[Prior art]
In recent years, the development of electronic technology has been remarkable, and various devices have been reduced in size and weight. Coupled with the reduction in size and weight of electronic devices, there is an increasing demand for reduction in size and weight of batteries that serve as power sources. Non-aqueous secondary batteries using lithium are mainly used as power sources for small electronic devices used in homes such as mobile phones, personal computers, and video camcorders as batteries that can obtain greater energy with a smaller volume and weight. I came. In these lithium non-aqueous secondary batteries, safety measures are important, especially overcharged batteries due to ignition accidents caused by over-discharge due to short-circuiting of external electrodes, or failure of the charging device during charging or improper rapid charging operation. A bimetallic thermal protector and a PTC element are mounted for the purpose of preventing a battery rupture accident caused by a voltage, an overcharge current, a reverse connection voltage, and a rise in temperature inside the battery.
[0003]
Among them, the PTC element is a resistive element that suppresses current by suddenly increasing its resistance value at a certain temperature, has a simple structure, can be reduced in size, and does not involve mechanical operation, so it is reliable. It has the advantage of being excellent. However, such a PTC element has a relatively high resistivity at room temperature, and an output loss is likely to occur, which tends to cause deterioration in discharge characteristics. Further, since the increase in area of the element tends to cause heat generation due to power concentration inside the element, there is a problem that it is difficult to mount the element on a large battery.
[0004]
On the other hand, several technologies for preventing thermal runaway of a battery by including in the battery a heat-sensitive microcapsule containing a substance capable of inhibiting the battery reaction when the temperature of the battery rises have been proposed (Japanese Patent Laid-Open Publication No. Sho). 63-86355, JP-A-6-283206, JP-A-10-270084, etc.). In these techniques, the battery reaction is intended to be chemically suppressed by the encapsulated substance.
[0005]
[Problems to be Solved by the Invention]
According to the researches of the present inventors, the above-described measures for preventing the thermal runaway of the battery that chemically suppresses the battery reaction by the encapsulated substance are as follows: (a) The encapsulated substance is not effectively released when the battery temperature rises. In addition, there is a time lag between the temperature rise and the release of the encapsulated substance, and (b) even if the encapsulated substance is released, this may act on the battery active material to rapidly advance the battery reaction suppression reaction. Thermal runaway of battery reaction that increases exponentially in temperature due to difficulty (Once it occurs, heat generation and runaway are further promoted by oxidative decomposition of electrolyte, etc., leading to accidents such as battery rupture and ignition) There is a problem that it cannot be effectively prevented.
[0006]
In view of the above circumstances, the main object of the present invention is to respond to a rapid temperature rise inside the battery due to overdischarge, overcharge, etc. with a quicker response, effectively preventing accidents caused by thermal runaway of the battery reaction. It is an object of the present invention to provide an electrode structure to be avoided and a non-aqueous battery including the electrode.
[0007]
[Means for solving the problems]
In the process of studying for the above-mentioned purpose, the present inventors pay attention to the fact that a battery reaction that can cause thermal runaway proceeds in a state where the conductive state in the battery is maintained. It has been found that the battery reaction can be suppressed, and that it is effective to dispose the thermally expandable microcapsules in the battery as a means of physically achieving the inhibition of the conductive state.
[0008]
The electrode of the present invention is based on the above-described knowledge. More specifically, the electrode has a laminated structure of an electrode mixture layer made of a positive electrode material or a negative electrode material that occludes / releases lithium, and a current collector, A heat-expandable microcapsule is included in the electrode mixture layer or in a layer provided between the electrode mixture layer and the current collector. Further, the non-aqueous battery of the present invention is a non-aqueous battery having a structure in which an electrolyte is present between a positive electrode and a negative electrode which are stacked apart from each other, and at least one of the positive electrode and the negative electrode is separated from the electrode. It is characterized by.
[0009]
The non-aqueous battery including the electrode of the present invention causes a rapid internal temperature increase due to overdischarge, overcharge, etc., and a predetermined temperature (preferably 80 ° C. to hundreds immediately before thermal runaway due to abnormal heat generation of the battery is started. When the temperature reaches 10 ° C., the outer shell made of the thermoplastic resin softens, and there is an expansion stress of the encapsulated volatile expansion agent, so that the outer shell expands rapidly and the electrode mixture layer expands or Abrupt peeling of the electrode mixture layer from the current collector occurs, and current interruption is effectively achieved by a rapid increase in resistance between the electrode active material and the current collector. Accordingly, the electrode active material is electrically connected to the current collector, and the battery reaction that proceeds in a good current transmission state is effectively blocked. Accordingly, the thermoplastic resin constituting the outer shell is appropriately designed to be stable at the battery operating temperature in contact with the electrolyte, but to be surely softened and expanded at the predetermined temperature. Then, in the non-aqueous battery including the electrode of the present invention, it is possible to effectively prevent the occurrence of an accident due to thermal runaway.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
1 and 2 are schematic cross-sectional views in the thickness direction showing two examples of typical laminated structures of the electrode of the present invention. That is, the electrode of the present invention typically includes a positive electrode material or negative electrode material (hereinafter collectively referred to as “electrode active material”) 1 a that occludes and releases lithium, and a current collector. 2 and the thermally expandable microcapsule 3 is included in the electrode mixture layer 1 (FIG. 1) or a layer between the electrode mixture layer 1 and the current collector 2 30 (FIG. 2).
[0011]
Thermally expandable microcapsules (often referred to as “microspheres”) 3 are obtained by encapsulating or encapsulating a volatile expansion agent in an outer shell made of a thermoplastic resin. Conventionally, such heat-expandable microcapsules suspend a polymerizable mixture containing at least a volatile expansion agent and a polymerizable monomer that gives a polymer constituting the outer shell in an aqueous dispersion medium. Manufactured by a polymerization method. For example, Japanese Patent Publication No. 42-26524, Japanese Patent Laid-Open No. 62-286534, Japanese Patent Laid-Open No. 4-292634, Japanese Patent Laid-Open No. 11-209504, etc. disclose a method for producing a thermally expandable thermoplastic microsphere. It can be applied to the production of the thermally expandable microcapsule of the present invention.
[0012]
The thermoplastic resin constituting the outer shell needs to show durability against the electrolyte solution described later, and more specifically, the battery operating temperature (generally from room temperature to about 80 ° C.) in contact with the electrolyte solution. A predetermined temperature immediately before the thermal runaway due to abnormal heat generation of the battery is started in a state in which the outer shell structure is stably maintained and a volatile expansion agent described later is included, that is, 80 ° C. to 180 ° C. It is necessary to suddenly soften and foam at 100C, more preferably from 100C to 160C. Therefore, as the thermoplastic resin itself, the elastic modulus lowering start temperature (thermally expandable microcapsules are heated and foamed, the inner foaming agent is removed, and then heated to 1 cm × 1.5 cm × 0.25 cm test piece. What was adjusted was measured at a frequency of 10 Hertz and a temperature rising rate of 3 ° C./min using a Rheograph solid of Toyo Seiki Seisakusho, 40 ° C. to 160 ° C., particularly 60 ° C. to 130 ° C. It preferably has gas barrier properties. An arbitrary thermoplastic resin is used as long as it has such characteristics, but it is not always easy to stably exhibit such characteristics, and an appropriate resin design needs to be made. .
[0013]
That is, the thermoplastic resin that forms the outer shell of the microcapsule is preferably a polymer that is excellent in anti-electrolytic solution, thermoplastic, and excellent in gas barrier properties. From this viewpoint, the outer shell is preferably constituted by a (co) polymer containing vinylidene chloride and a (co) polymer containing (meth) acrylonitrile.
[0014]
In particular, the outer shell is preferably composed of a (co) polymer containing (meth) acrylonitrile as a main component (51% by weight or more). Specific examples of preferable outer shell constituting polymers include (a) 51% by weight or more of at least one monomer selected from the group consisting of acrylonitrile and methacrylonitrile, and (b) vinylidene chloride, acrylic acid ester, methacrylic acid, Examples thereof include a copolymer obtained from a monomer mixture containing 49% by weight or less of at least one monomer selected from the group consisting of acid esters, styrene, and vinyl acetate. More preferably, the monomer mixture is (a) 51 to 98% by weight of at least one monomer selected from the group consisting of acrylonitrile and methacrylonitrile, (b1) 1 to 48% by weight of vinylidene chloride, and ( b2) It contains 1 to 48% by weight of at least one monomer selected from the group consisting of acrylic acid esters and methacrylic acid esters. If the copolymerization ratio of (meth) acrylonitrile is less than 51% by weight, the solvent resistance and heat resistance are excessively lowered, which is not preferable.
[0015]
As a preferable example of the copolymer not containing vinylidene chloride, as the polymerizable monomer, (c) at least one monomer selected from the group consisting of acrylonitrile and methacrylonitrile, 51 to 100% by weight, more preferably A monomer mixture containing 70 to 100% by weight and (d) at least one monomer selected from the group consisting of acrylic acid ester and methacrylic acid ester, 0 to 49% by weight, more preferably 0 to 30% by weight. The copolymer obtained by using is mentioned. More preferably, the monomer mixture is selected from the group consisting of (c1) acrylonitrile 20 to 80% by weight, (c2) methacrylonitrile 20 to 80% by weight, and (e) an acrylic ester and a methacrylic ester. It contains 0 to 49% by weight of at least one monomer, more preferably 0 to 30% by weight. With such a copolymer, it is possible to obtain an outer shell of a thermally expandable microcapsule having excellent gas barrier properties, solvent resistance, heat resistance, thermal expandability, and the like.
[0016]
In order to improve the foaming characteristics and heat resistance of the resulting microcapsules, a crosslinkable monomer can be used in combination with the polymerizable monomer as described above. As the crosslinkable monomer, a compound having two or more carbon-carbon double bonds is usually used. More specifically, examples of the crosslinkable monomer include divinylbenzene, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, allyl methacrylate, isocyanate. Examples include triallyl acid, triacryl formal, trimethylolpropane tri (meth) acrylate, 1,3-butyl glycol dimethacrylate, pentaerythritol tri (meth) acrylate, and the like. The use ratio of the crosslinkable monomer is usually 0.1 to 5% by weight in the polymerizable monomer. However, the durability to a good electrolytic solution and the microscopically reliably at a predetermined temperature under contact with the electrolytic solution. In order to cause foaming of the capsule, it is preferable to use 0.5% by weight, particularly 1.0% by weight, and 5% by weight or less, particularly 4% by weight or less of a crosslinkable monomer. From the viewpoint of controlling the foaming temperature, it is preferable to use a bifunctional monomer as compared with a trifunctional or higher polyfunctional monomer.
[0017]
As the volatile swelling agent enclosed in the outer shell, volatilization that gasifies at a predetermined temperature causing foaming of the microcapsule, more directly at a temperature below the softening point of the thermoplastic resin constituting the outer shell of the microcapsule. Organic compounds such as propane, propylene, n-butane, isobutane, butene, isobutene, isopentane, neopentane, n-pentane, n-hexane, isohexane, heptane, petroleum ether having a boiling point of 100 ° C. or less Hydrogen is preferably used. In consideration of safety inside the battery, non-flammable or flame retardant compounds such as halogenated hydrocarbons such as methyl chloride, methylene chloride, fluorotrichloromethane, difluorodichloromethane, chlorotrifluoromethane, and chlorofluorocarbons Is mentioned. These can be used alone or in combination of two or more.
[0018]
In the microencapsulation suspension polymerization, these volatile swelling agents are used in an amount of 5 to 100 with respect to 100 parts by weight of a polymerizable monomer (including a crosslinkable monomer) that gives a thermoplastic resin constituting the outer shell. It is preferable to use it in a ratio of parts by weight, particularly 7 to 70 parts by weight.
[0019]
The heat-expandable microcapsule of the present invention contains these volatile expansion agent and polymerizable monomer, if necessary, azobisisobutyronitrile, benzoyl peroxide, lauroyl peroxide, diisopropyl peroxydicarbonate, t -By subjecting it to suspension polymerization in the presence of a polymerization initiator such as butyl peroxide or 2,2'-azobis (2,4-dimethylvaleronitrile) in the usual manner, preferably in an aqueous dispersion medium. can get.
[0020]
The average particle diameter (median diameter) of the thermally expandable microcapsule can be controlled by a method generally used in this field. For example, in suspension polymerization, the selection of a dispersion stabilizer, that is, its type (inorganic fine particles such as colloidal silica and magnesium hydroxide) and amount, auxiliary stabilizer (for example, condensation product of diethanolamine and aliphatic dicarboxylic acid, polyvinylpyrrolidone, etc. , Polyethylene oxide, various emulsifiers, salt, etc.), selection of emulsifying and dispersing means and emulsifying conditions (such as stirring conditions). The average particle size is usually 1 to 40 μm, preferably 3 to 30 μm, particularly preferably 5 to 25 μm. In particular, if the particle size distribution is sharp, the foaming start temperature becomes sharp and can be used more suitably in the present invention. The foaming ratio is 2 to 100 times, preferably by controlling the selection of the volatile swelling agent and the polymerizable monomer, the kind and amount of the crosslinkable monomer, and the weight ratio of the volatile swelling agent / polymerizable monomer. A microcapsule adjusted to a desired value within a range of 3 to 60 times is obtained.
[0021]
Referring again to FIG. 1, the thermally expandable microcapsule 3 obtained as described above is instantly active in the electrode mixture layer 1 containing the electrode active material 1 a by foaming at a predetermined temperature. The minimum amount necessary to achieve effective separation between 1a and current collector 2, for example, 0.01 to 5% by weight, preferably 0.05 to 2% by weight of the total electrode mixture constituting layer 1 It is preferable to mix | blend in the ratio of%. In addition to the positive electrode or negative electrode active material 1a, the electrode mixture constituting the layer 1 comprises 88 to 99 parts by weight of a powder electrode material containing a conductive auxiliary agent such as carbon black and other auxiliary agents added as necessary. 1 to 12 parts by weight of a vinylidene fluoride polymer, a tetraethylene polymer, and a latex styrene-butadiene copolymer. The electrode mixture layer 1 may be formed by mixing the binder and the thermally expandable microcapsule 3 with water or an organic solvent to obtain an electrode mixture slurry, which is applied onto the current collector 2 and dried.
[0022]
When the configuration as an electrode for a lithium ion battery is taken as an example, the current collector 2 is made of, for example, a metal foil such as iron, stainless steel, copper, aluminum, nickel, titanium, or a metal net, and has a thickness of 5 to 5. In the case of a small scale, a conductive base material such as 5 to 20 μm is used, and the electrode mixture layer 1 is formed to a thickness of about 10 to 1000 μm, preferably about 30 to 500 μm.
[0023]
In the electrode of FIG. 2, the thermally expandable microcapsule 3 is arranged in a layer 30 between the electrode mixture layer 1 and the current collector 2, and the microcapsule layer 30 is formed as described above. To 100 parts by weight of the obtained thermally expandable microcapsules, 5 to 100 parts by weight of a binder and further 10 to 300 parts by weight of a conductive aid such as carbon black for ensuring conductivity are added, and water or organic The microcapsule slurry obtained by mixing with a solvent is preferably applied on the current collector 2 and dried to form a thickness of 3 to 100 μm, particularly 5 to 50 μm. A layer 2 of the electrode mixture (excluding or additionally including the thermally expandable microcapsule 3) as described above is further formed thereon.
[0024]
As the active material 1a for the lithium ion secondary battery, in the case of the positive electrode, the general formula LiMY ₂ (M is at least one kind of transition metal such as Co, Ni, Fe, Mn, Cr, V, etc .; Y is O, S, etc.) composite metal complex metal chalcogen compound represented by chalcogen elements), in particular taking a spinel structure such as _{LiNi x CO 1-x O 2} (0 ≦ x ≦ 1) and including a composite metal oxide, LiMn ₂ O ₄ Oxides are preferred.
[0025]
Active materials for the negative electrode include activated carbon, graphite materials such as mesophase carbon microbeads (MCMB), or those obtained by firing and carbonizing phenol resin or pitch, and carbonaceous materials such as coconut shell activated carbon. Physical GeO, GeO ₂ , SnO, SnO ₂ , PbO, PbO ₂ , SiO, SiO ₂ or the like, or a composite metal oxide thereof is used.
[0026]
FIGS. 3 and 4 show two examples of the non-aqueous battery of the present invention including the electrodes of FIGS. 1 and 2 as the negative electrode A (1A: negative electrode mixture layer including negative electrode active material 1aa, 2A: negative electrode current collector), respectively. It is a schematic cross section of an example. In these references, the non-aqueous battery generally has an intermediate sheet-like layer 4 made of a solid electrolyte or a separator formed in a sheet shape, the negative electrode A and the positive electrode B (1B: positive electrode mixture layer, 2B: positive electrode). A laminated structure sandwiched between the current collectors). Such a laminated structure is impregnated with an electrolytic solution (in particular, when the intermediate sheet-like layer 4 is a solid electrolyte made of a vinylidene fluoride-hexafluoropropylene copolymer or the like), or such a laminated structure is placed in the electrolytic solution. A non-aqueous battery is formed by immersing in (especially when the intermediate sheet-like layer 4 is a separator made of a porous material). The intermediate sheet-like layer 1 preferably has a thickness of about 2 to 1000 μm, particularly about 5 to 200 μm. In the above, the negative electrode A is composed of the electrode of the present invention, but conversely, the positive electrode B can be an electrode containing a thermally expandable microcapsule according to the present invention, and both the negative electrode A and the positive electrode B are thermally expanded. The electrode of the present invention including a conductive microcapsule may be used.
[0027]
The electrolyte includes LiPF ₆ , LiAsF ₆ , LiClO ₄ , LiBF ₄ , LiCl, LiBr, LiCH ₃ SO ₃ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , Etc., propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, γ-butyrolactone, methyl propionate, ethyl propionate, and mixtures thereof Although what was melt | dissolved in the solvent etc. is used, it is not necessarily limited to these.
[0028]
For example, the laminated sheet-like battery body having the structure shown in FIG. 3 or FIG. 4 obtained as described above is further laminated by winding, folding, or the like as necessary to increase the electrode area per volume. Is a non-aqueous battery having an overall structure such as a square shape, a cylindrical shape, a coin shape, or a paper shape, for example, by a process such as accommodating in a relatively simple container and forming an extraction electrode.
[0029]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples.
[0030]
(Preparation Example 1 of Thermally Expandable Microcapsule)
An aqueous dispersion medium was prepared by charging 16.5 g of colloidal silica, 0.65 g of diethanolamine-adipic acid condensation product, 169.8 g of sodium chloride, 0.11 g of sodium nitrite, and water to a total of 557 g. Furthermore, hydrochloric acid was added and adjusted so that the pH of the aqueous dispersion was 3.2.
[0031]
On the other hand, polymerization consisting of 147.4 g of acrylonitrile, 70.4 g of methacrylonitrile, 2.2 g of methyl methacrylate, 5.5 g of diethylene glycol dimethacrylate, 4.2 g of isobutane, 37.6 g of isopentane, and 1.32 g of azobisisobutyronitrile. (Weight ratio of monomer components: acrylonitrile / methacrylonitrile / methyl methacrylate = 67/32/1, the amount of the crosslinking agent is 2.44% by weight in the monomer). This polymerizable mixture and the aqueous dispersion medium prepared above were stirred and mixed with a disperser to granulate fine droplets of the polymerizable mixture.
[0032]
An aqueous dispersion medium containing fine droplets of this polymerizable mixture was charged into a polymerization can equipped with a stirrer (1.5 liters), and reacted at 60 ° C. for 45 hours using a hot water bath. The obtained reaction product was repeatedly filtered and washed with water to obtain thermally expandable microcapsules (microspheres) MS-1 having an average particle size of about 30 μm. The expansion ratio of MS-1 at 170 ° C. was about 25 times.
[0033]
(Preparation example 2 of thermally expandable microcapsule)
The average particle size is about 10 μm as in Preparation Example 1, except that 8.8 g of colloidal silica, 0 g of sodium chloride, and 1.32 g of isopropyl peroxydicarbonate instead of azobisisobutyronitrile are used. A thermally expandable microcapsule MS-2 was obtained. The expansion ratio of MS-2 at 170 ° C. was about 15 times.
[0034]
(Preparation Example 3 of Thermally Expandable Microsphere)
In the same manner as in Preparation Example 2, except that the monomer charge was changed so that the monomer component charge ratio was acrylonitrile / methacrylonitrile / methyl methacrylate = 65/30/5. A thermally expandable microcapsule MS-3 having a particle size of about 10 μm was obtained. The expansion ratio of MS-3 at 150 ° C. was about 15 times.
[0035]
(Preparation of positive electrode)
3 parts by weight of vinylidene fluoride-hexafluoropropylene copolymer was mixed with 92 parts by weight of LiCoO ₂ , 5 parts by weight of conductive carbon black and 35 parts by weight of N-methyl-2-pyrrolidone. The obtained slurry was applied onto an aluminum foil having a thickness of 10 μm and dried at 130 ° C. to obtain a positive electrode having a mixture layer having a thickness of 170 μm.
[0036]
(Preparation of negative electrode 1)
0.5 parts by weight of thermally expandable microcapsule MS-1 prepared as described above, 1.5 parts by weight of styrene-butadiene copolymer latex, 0.3 parts by weight of carboxymethyl cellulose, 110 parts by weight of water, and an average particle size 98 parts by weight of 20 μm mesophase carbon microbeads (MCMB, negative electrode active material) were mixed. The obtained slurry was applied on a copper foil having a thickness of 10 μm and dried at 80 ° C. to obtain a negative electrode A1 having a mixture layer having a thickness of 170 μm.
[0037]
(Production of negative electrode 2)
5 parts by weight of thermally expandable microcapsule MS-2 prepared as described above was mixed with 10 parts by weight of conductive carbon black, 2 parts by weight of styrene-butadiene copolymer latex, 0.3 parts by weight of carboxymethylcellulose and 100 parts by weight of water. did. The obtained slurry was applied onto a copper foil having a thickness of 10 μm and dried at 80 ° C. to obtain an electrode plate having a base layer having a thickness of 30 μm. Next, 98 parts by weight of MCMB was mixed with 2 parts by weight of styrene butadiene latex, 0.3 parts by weight of carboxymethyl cellulose and 110 parts by weight of water. The obtained slurry was applied on the base layer of the electrode plate and dried at 80 ° C. to obtain a negative electrode A2 having a mixture layer having a thickness of 140 μm and a base layer having a thickness of 30 μm.
[0038]
(Preparation of negative electrode 3)
Thermally expandable microsphere MS-1 Negative electrode A3 having a mixture layer having a thickness of 170 μm in the same manner as in (Preparation of negative electrode 1) except that 0.8 part of MS-3 was used instead of 0.5 part. Got.
[0039]
The operational characteristics and electrode structure of the thermally expandable microcapsules in the above examples are summarized as shown in Table 1 below.
[0040]
[Table 1]

[0041]
(Evaluation of electrode)
The obtained negative electrodes A1 to A3 having the laminated structure shown in FIG. 1 or FIG. 2 were heated from room temperature to 150 ° C. at about 2 ° C./min while being immersed in propylene carbonate in a sealed container. In A1 and A2, the microspheres foamed at the same time when the internal temperature reached 145 ° C., and in A1, MCMB was peeled off in bulk, and in A2, most of MCMB was peeled off from the copper foil and floated, It became. In A3, when the internal temperature reached 125 ° C., the microspheres foamed at once, and MCMB was peeled off in pieces. After cooling to room temperature, the electrode A2 in which foaming occurred was taken out, a weight of 10 g was placed on the mixture layer, and the resistance between the weight and the uncoated portion of the copper foil was measured. The value was about 150 times.
[0042]
【The invention's effect】
In the above evaluation example, when the electrode including the thermally expandable microcapsule of the present invention reaches a predetermined temperature in contact with the electrolytic solution, a non-conductive state is instantaneously formed between the electrode active material and the current collector. It is understood that it is extremely effective in preventing thermal runaway of a battery reaction that proceeds in a conductive state.
[Brief description of the drawings]
FIG. 1 is a schematic view of a laminated structure of electrodes according to an embodiment of the present invention.
FIG. 2 is a schematic diagram of a laminated structure of electrodes according to another embodiment of the present invention.
FIG. 3 is a schematic diagram of a laminated structure of a non-aqueous battery according to an embodiment of the present invention.
FIG. 4 is a schematic view of a laminated structure of a nonaqueous battery according to another embodiment of the present invention.
[Explanation of symbols]
1: Electrode mixture layer (1A: negative electrode mixture layer, 1B: positive electrode mixture layer)
1a: electrode active material (1aa: negative electrode active material)
2: Current collector (2A: in the negative electrode, 2B: in the positive electrode)
3: Thermally expandable microcapsule 4: Intermediate sheet layer (solid electrolyte or separator)
30: Microcapsule layer A: Negative electrode B: Positive electrode

Claims (6)

It has a laminated structure of an electrode mixture layer made of a positive electrode material or a negative electrode material that occludes / releases lithium and a current collector, and is in the electrode mixture layer or between the electrode mixture layer and the current collector. An electrode comprising thermally expandable microcapsules contained in a layer provided on the substrate.  At least one monomer selected from the group consisting of acrylonitrile and methacrylonitrile, wherein the heat-expandable microcapsule encloses a volatile expansion agent in an outer shell made of a thermoplastic resin. The electrode according to claim 1, comprising a polymer mainly composed of  A thermally expandable microcapsule is formed by encapsulating a volatile swelling agent in an outer shell made of a thermoplastic resin, and the thermoplastic resin contains a crosslinkable monomer of more than 0.5 wt% and not more than 5 wt%. The electrode according to claim 1, comprising a polymer of a monomer mixture containing the electrode.  The electrode according to any one of claims 1 to 3, wherein the average particle size of the thermally expandable microcapsule is 40 µm or less.  The electrode according to any one of claims 1 to 4, further comprising 0.01 to 5% by weight of thermally expandable microcapsules based on the weight of the mixture containing the positive electrode or the negative electrode active material in the electrode mixture layer. A nonaqueous battery having a structure in which an electrolyte is present between a positive electrode and a negative electrode that are stacked apart from each other, and at least one of the positive electrode and the negative electrode includes the electrode according to any one of claims 1 to 5. Non-aqueous battery.

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