JP2005268206A - Positive electrode mixture, nonaqueous electrolyte secondary battery and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress deterioration of property of a nonaqueous electrolyte secondary battery and reduce the amount of generated gas. <P>SOLUTION: The nonaqueous electrolyte secondary battery is formed by sealing a winding type electrode element 1 with a sheath material 2. The winding electrode element 1 is formed by winding a positive electrode and a negative electrode each having gel electrolyte layers formed on both sides thereof while interposing a separator between the positive electrode and the negative electrode. The positive electrode consists of a positive electrode collector and a positive electrode mixture layer formed on the both sides of the positive electrode collector. The negative electrode consists of a positive electrode collector and a negative electrode mixture layer formed on the both sides of the negative electrode collector. The positive electrode mixture layer consists of a lithium transition metals composite oxide, a binding agent, a conductive agent, poly (oxy-ethylene) or poly (oxy-propylene). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a positive electrode mixture that can be doped and dedoped with lithium, a nonaqueous electrolyte secondary battery, and a method for producing the same.

  In recent years, many portable electronic devices such as mobile phones, portable audio players, PDAs (Personal Digital Assistants) have appeared, and their size and weight have been reduced. As a portable power source for these electronic devices, a lithium ion secondary battery having a large energy density has been used.

  By the way, a non-aqueous electrolyte is used for the lithium ion secondary battery, and in order to prevent this liquid leakage, a metal container is used as an exterior material. However, when such a metal container is used as the exterior material, for example, a thin large-area sheet-type battery, a thin small-area card-type battery, or a flexible battery having a higher degree of freedom is manufactured. It becomes very difficult.

  Therefore, in order to solve the above-mentioned problem, it has been studied to produce a battery using an inorganic / organic complete solid electrolyte or a semi-solid electrolyte made of a polymer gel. Specifically, so-called solid electrolyte batteries using a polymer solid electrolyte composed of a polymer and an electrolyte and a gel electrolyte obtained by adding a non-aqueous electrolyte as a plasticizer to a matrix polymer have been proposed. (For example, refer to Patent Document 1).

  In the solid electrolyte battery, since the electrolyte is solid or gel, there is no fear of liquid leakage, the electrolyte is fixed, and the thickness of the electrolyte can be fixed. Moreover, the adhesiveness between the electrolyte and the electrode is good, and the contact between the electrolyte and the electrode can be maintained. For this reason, solid electrolyte batteries do not need to contain an electrolytic solution in a metal container or apply pressure to the battery element, so that a film-like exterior with a high degree of freedom in molding can be used, and the diversified portable Batteries can be designed according to electronic equipment.

  In particular, by using a moisture-proof laminate film made of a polymer film capable of heat-sealing and a metal foil as the exterior material, a sealed structure can be easily realized by hot sealing or the like. In addition, the moisture-proof laminate film has the advantages that the film itself has high strength and excellent airtightness, and is lighter, thinner and less expensive than a metal container.

However, since the material of the film-shaped exterior material is soft, it reacts sensitively to changes in the battery internal pressure. That is, there may be a problem that the battery swells due to gas generated as a result of oxidation / decomposition of the electrolyte on the electrode surface, resulting in a shape abnormality. In particular, it is expected that a fully charged battery will be adversely affected when stored for a long time in a car in summer.
JP 2003-197259 A

  As a method for solving the above problem, many electrolyte additives for generating a film on the positive electrode active material and suppressing gas generation have been proposed. However, there are problems in that the unreacted substances of these additives are reduced and decomposed at the negative electrode, and that the battery characteristics are deteriorated by generating an excessive amount of the positive electrode film in association with the charge / discharge cycle.

  Further, studies have been made to reduce the specific surface area of the positive electrode active material in order to suppress the oxidation reaction. However, when the specific surface area of the positive electrode active material is decreased, there are problems that characteristics such as load characteristics and temperature characteristics are often sacrificed and productivity of the positive electrode active material is lowered.

  Accordingly, an object of the present invention is to provide a positive electrode mixture, a non-aqueous electrolyte secondary battery, and a method for manufacturing the same, which can suppress a decrease in battery characteristics and reduce gas generation.

  The present inventor has intensively studied to solve the above-described problems of the prior art. As a result, by adding a small amount of poly (oxyethylene) or poly (oxypropylene) to the positive electrode mixture, it is possible to suppress the deterioration of battery characteristics and to reduce the gas generation. It came. The present invention has been devised based on the above studies.

  In order to solve the above problems, the first invention is a positive electrode mixture containing a positive electrode active material and poly (oxyethylene) or poly (oxypropylene).

A second invention comprises a positive electrode and a negative electrode for electrochemically doping and dedoping lithium,
An electrolyte interposed between the positive electrode and the negative electrode,
The positive electrode has a positive electrode mixture containing a lithium transition metal composite oxide and poly (oxyethylene) or poly (oxypropylene).

A third invention comprises a positive electrode and a negative electrode for electrochemically doping and undoping lithium,
In a method of manufacturing a nonaqueous electrolyte secondary battery comprising an electrolyte interposed between a positive electrode and a negative electrode,
Producing a positive electrode using a positive electrode mixture containing lithium transition metal composite oxide and poly (oxyethylene) or poly (oxypropylene);
Producing a negative electrode using a negative electrode active material;
And a step of interposing an electrolyte between the positive electrode and the negative electrode. A method for producing a non-aqueous electrolyte secondary battery.

In the first, second and third inventions, the positive electrode mixture preferably further contains a binder, and more preferably further contains a binder and a conductive agent. The positive electrode active material is typically a lithium transition metal composite oxide. The lithium transition metal composite oxide is typically a lithium / cobalt composite oxide, a lithium / nickel composite oxide, or a lithium / manganese composite oxide. Further, the lithium transition metal composite oxides are typically general formula _{Li x M y N z O 2} (M is Co, one of Ni, N is Co, Mn, Ni, Cr, Fe, V, Al , B, Mg, or a combination of two or more thereof, 0.05 ≦ x ≦ 1.10, y> 0, 0.80 ≦ y + z ≦ 1.00. Moreover, it is preferable to contain 0.03 to 3 parts by weight of poly (oxyethylene) or poly (oxypropylene). The specific surface area of the lithium-transition metal composite oxide is preferably within a range of 0.14 m ² / g or more 0.78 m ² / g. The lithium transition metal composite oxide typically has a layered structure or a spinel structure.

  In the second invention, it is preferable that poly (oxyethylene) or poly (oxypropylene) is dispersed in the positive electrode mixture. In addition, it is preferable that the lithium transition metal composite oxide typically has a particulate shape, and at least a part of the surface of the particle is covered with poly (oxyethylene) or poly (oxypropylene). The positive electrode typically includes a positive electrode current collector and a positive electrode mixture layer formed on the positive electrode current collector and made of a positive electrode mixture. Moreover, it is preferable to further include a separator interposed between the positive electrode and the negative electrode. Moreover, the positive electrode and negative electrode in which the separator is interposed are typically wound. A nonaqueous electrolyte secondary battery typically further includes an exterior material that houses a positive electrode and a negative electrode in which an electrolyte is interposed. The exterior material is typically formed by laminating an adhesive layer on a metal layer. The adhesive layer is typically a polymer film. The electrolyte is typically an electrolytic solution, a gel electrolyte, or a solid electrolyte. The gel electrolyte typically consists of a gelled polymer matrix.

In the third invention, before the step of producing the positive electrode, the lithium transition metal composite oxide is mixed with poly (oxyethylene) or poly (oxypropylene) to obtain poly (oxyethylene) or poly (oxypropylene). It is preferable to further include a step of producing a positive electrode mixture in which is dispersed. Further, it is preferable to further include a step of heating the positive electrode after the step of manufacturing the positive electrode. Also, if in the step of heating the cathode, a melting initiation temperature of poly observed by differential scanning calorimetry (oxyethylene) or poly (oxypropylene) and T _1, the heat treatment temperature was set to T _2, T ₁ <heat treatment is preferably performed so as to satisfy the relation of T _2. In the step of producing a positive electrode, typically, a lithium transition metal composite oxide and a positive electrode mixture composed of poly (oxyethylene) or poly (oxypropylene) are dispersed in a solvent to form a slurry. Then, it is applied onto a positive electrode current collector and dried to produce a positive electrode. Moreover, when drying the slurry positive electrode mixture, a melting initiation temperature of poly observed by differential scanning calorimetry (oxyethylene) or poly (oxypropylene) and T _1, drying the slurry of positive electrode material mixture the temperature for the case of the T _2, so as to satisfy the relationship of T ₁ <T _2, by heating a slurry positive electrode mixture is preferably dried. The electrolyte is typically an electrolytic solution, a gel electrolyte, or a solid electrolyte.

By adding a small amount of poly (oxyethylene) or poly (oxypropylene) to the positive electrode mixture, it is speculated that the deterioration of battery characteristics and gas generation can be reduced due to the following reasons. . That is, since poly (oxyethylene) and poly (oxypropylene) have high polarity, it is considered that the affinity with the active material surface hydroxyl group such as LiCoO ₂ and LiNiO ₂ is high. Therefore, it is considered that poly (oxyethylene) and poly (oxypropylene) are present in such a manner as to cover the positive electrode active material in the electrode, thereby suppressing oxidative decomposition of the electrolytic solution in a high-temperature overcharge state or the like. In addition, poly (oxyethylene) and poly (oxypropylene) have high lithium ion conductivity so that they are also used as solid electrolytes. Therefore, it is considered that the interface resistance is relatively small and the battery characteristics are not impaired.

  It is estimated that the effect of suppressing the swelling of the exterior material can be further improved by heat-treating the positive electrode at a temperature equal to or higher than the melting point of poly (oxyethylene) or poly (oxypropylene) for the following reason. That is, it is considered that poly (oxyethylene) or poly (oxypropylene) is melted and softened to more effectively coat the active material surface.

  As described above, according to the inventions according to claims 1, 7 and 21, it is possible to realize a nonaqueous electrolyte secondary battery in which gas generation during high-temperature storage is suppressed and deterioration of characteristics is suppressed. it can. Therefore, a high quality nonaqueous electrolyte secondary battery can be realized.

  According to the invention which concerns on Claim 5, 10 and 24, gas generation | occurrence | production can be suppressed and a favorable load characteristic can be acquired.

  According to the invention which concerns on Claim 6, 11 and 25, generation | occurrence | production of gas can further be suppressed and a favorable load characteristic can be acquired.

  According to the invention which concerns on Claim 12 and 26, since poly (oxyethylene) or poly (oxypropylene) is disperse | distributed in a positive electrode mixture, the active material layer surface contained in a positive electrode mixture is effectively coat | covered. be able to. Thereby, gas generation can be further suppressed.

  According to the invention of claim 28, since poly (oxyethylene) or poly (oxypropylene) can be melted, the active material layer surface contained in the positive electrode mixture can be effectively coated. Thereby, generation | occurrence | production of gas can further be suppressed.

  According to the invention of claim 30, since the poly (oxyethylene) or poly (oxypropylene) can be melted in the step of drying the positive electrode mixture, the heating can be performed without providing a separate heating step thereafter. The same effect as when processing is performed can be obtained. Therefore, it is possible to manufacture a non-aqueous electrolyte secondary battery in which the generation of gas during high-temperature storage is suppressed and the deterioration of characteristics is suppressed without deteriorating the production efficiency.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In all the drawings of the following embodiment, the same or corresponding parts are denoted by the same reference numerals.

  FIG. 1 is an exploded perspective view showing a configuration example of a nonaqueous electrolyte secondary battery according to an embodiment of the present invention. As shown in FIG. 1, this non-aqueous electrolyte secondary battery includes a wound electrode element 1 accommodated in an exterior material 2 made of a moisture-proof laminate film, and sealed around the wound electrode element 1 by welding. Stop. The wound electrode element 1 is provided with leads 3 and 4, and these leads 3 and 4 are sandwiched by the exterior material 2 and pulled out to the outside.

  The packaging material 2 has, for example, a laminated structure in which an adhesive layer, a metal layer, and a surface protective layer are sequentially laminated. The adhesive layer is made of a polymer film, and examples of the material constituting the polymer film include polypropylene (PP) and polyethylene (PE). The metal layer is made of a metal foil, and an example of a material constituting the metal foil is aluminum (Al). Examples of the material constituting the surface protective layer include nylon (Ny) and polyethylene terephthalate (PET). The surface on the adhesive layer side is a storage surface on the side where the wound electrode element 1 is stored.

  FIG. 2 is an exploded perspective view showing a configuration example of the wound electrode element 1. As shown in FIG. 2, the wound electrode element 1 includes a strip-shaped positive electrode 11, a strip-shaped negative electrode 12 disposed opposite to the positive electrode 11, and a gel formed on both surfaces of the positive electrode 11 and the negative electrode 12. An electrolyte layer 14 and a separator 13 interposed between the positive electrode 11 and the negative electrode 12 on which the gel electrolyte layer 14 is formed are provided. Specifically, the wound electrode element 1 includes a positive electrode 11 on which a gel electrolyte layer 14 is formed and a negative electrode 12 on which a gel electrolyte layer 14 is formed in a number of turns in the longitudinal direction via a separator 13. Turn.

  FIG. 3 is a cross-sectional view showing a configuration example of the wound electrode element 1. As shown in FIG. 3, the positive electrode 11 includes a strip-shaped positive electrode current collector 11a and a positive electrode mixture layer 11b formed on both surfaces of the positive electrode current collector 11a. The positive electrode current collector 11a is a metal foil made of, for example, aluminum. The positive electrode mixture layer 11b includes a positive electrode active material, a binder (binder), a conductive agent, and poly (oxyethylene) or poly (oxypropylene).

As the positive electrode active material, it is possible to use a lithium-transition metal composite oxide is a composite oxide of lithium and transition metal, for _{example, Li x M y N z O} 2 (M is Co, one of Ni, N Is Co, Mn, Ni, Cr, Fe, V, Al, B, Mg, or a combination of two or more thereof 0.05 ≦ x ≦ 1.10, y> 0, 0.80 ≦ y + z ≦ 1.00) can be used.

The specific surface area of the positive electrode active material is preferably 0.14 to 0.78 m ² / g. When the specific surface area is less than 0.14 m ² / g, the load characteristics tend to decrease. When the specific surface area is greater than 0.78 m ² / g, gas during high-temperature storage due to addition of poly (oxyethylene) or poly (oxypropylene) There is a tendency that the occurrence suppression effect is reduced and swelling occurs.

  The addition amount of poly (oxyethylene) or poly (oxypropylene) is preferably 0.03 parts by weight or more and 3 parts by weight or less. When the amount is less than 0.03 parts by weight, the swelling suppression effect of the outer packaging material 2 tends to be weakened, and when it is larger than 3 parts by weight, the load characteristics tend to deteriorate. Poly (oxyethylene) can be used from low molecular weight polyethylene glycol to high molecular weight polyethylene oxide, but preferably has a weight average molecular weight of 2,000 to 2,000,000, for example, about 200,000. . Poly (oxypropylene) can also be used from low molecular weight polypropylene glycol to high molecular weight polypropylene oxide, but preferably has a weight average molecular weight of 5,000 to 2,500,000, for example, about 300,000 polypropylene. Oxide.

  In addition, it is preferable that poly (oxyethylene) or poly (oxypropylene) is uniformly dispersed in the positive electrode mixture. By uniformly dispersing in this way, the surface of the particulate active material can be effectively covered. Therefore, gas generation due to oxidation / decomposition of the gel electrolyte layer 14 can be further suppressed. Therefore, the swelling of the exterior material 2 enclosing the wound electrode element 1 can be further suppressed.

  As the binder, for example, polytetrafluoroethylene, polyvinylidene fluoride (PVdF), polyethylene, or the like can be used. As the binder, for example, polyvinylidene fluoride having a weight average molecular weight of about 300,000 can be used. As the conductive agent, for example, carbon powder such as graphite and carbon black can be used.

  As shown in FIG. 3, the negative electrode 12 includes a strip-shaped negative electrode current collector 12a and a negative electrode mixture layer 12b formed on both surfaces of the negative electrode current collector 12a. The negative electrode current collector 12a is a metal foil made of, for example, copper. The negative electrode mixture layer 12b includes a negative electrode active material, a binder, and a conductive agent.

  The negative electrode active material is not particularly limited. For example, any metal can be used as long as it is a lithium metal, a metal capable of forming an alloy with lithium and an alloy thereof, or a material that is doped with lithium. Examples include non-graphitizable carbon, artificial graphite, natural graphite, pyrolytic carbons, cokes (pitch coke, needle coke, petroleum coke, etc.), graphites, glassy carbons, organic polymer compound fired bodies ( Carbonaceous materials such as phenol resins, furan resins and the like that are calcined and carbonized at an appropriate temperature), carbon fibers, activated carbon, carbon blacks, and the like can be used. Further, oxides such as iron oxide, ruthenium oxide, molybdenum oxide, tungsten oxide, titanium oxide, tin oxide, etc. that dope and dedope lithium at a relatively low potential, and other nitrides can be used as well.

  As the binder, for example, polytetrafluoroethylene, polyvinylidene fluoride (PVdF), polyethylene, or the like can be used. As the conductive agent, for example, carbon powder such as graphite and carbon black can be used.

  The gel electrolyte layer 14 is made of a gel electrolyte obtained by impregnating a matrix polymer with a nonaqueous solvent and an electrolyte salt. Any nonaqueous solvent can be used as long as it is used for this type of battery. For example, propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, γ-butyllactone, γ-valerolactone, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, , 3-dioxolane, 4-methyl-1,3-dioxolane, diethyl ether, sulfolane, methylsulfolane, acetonitrile, propionitrile, acetate ester, butyrate ester, propionate ester and the like. These may be used alone or as a mixture of two or more.

  As the matrix of the gel electrolyte, various polymers can be used as long as they can be gelated by absorbing the non-aqueous solvent described above. For example, fluorine-based polymers such as poly (vinylidene fluoride) and poly (vinylidene fluoride-co-hexafluoropropylene), ether-based polymers such as poly (ethylene oxide) and its crosslinked products, or poly (acrylonitrile) are used. it can. In particular, it is desirable to use a fluorine-based polymer from the viewpoint of redox stability. By containing an electrolyte salt, ionic conductivity is imparted.

Any electrolyte salt used in the above-described gel electrolyte layer 14 can be used as long as it is used in this type of battery. For example, LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiB (C ₆ H ₅ ) ₄ , CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, LiCl, LiBr, LiN (CF ₃ SO ₂ ) ₂ Etc.

  Next, a method for manufacturing a nonaqueous electrolyte secondary battery according to an embodiment of the present invention will be described.

<Positive electrode fabrication process>
First, for example, a positive electrode active material, a binder, a conductive agent, and poly (oxyethylene) or poly (oxypropylene) are mixed to prepare a positive electrode mixture. Then, this positive electrode mixture is dispersed in a solvent to form a slurry. Note that a ball mill, a sand mill, a biaxial kneader, or the like may be used as necessary.

  Next, the slurry-like positive electrode mixture is uniformly applied to both surfaces of the belt-like positive electrode current collector 11a. The coating apparatus is not particularly limited, and for example, slide coating, extrusion type die coating, reverse roll, gravure, knife coater, kiss coater, micro gravure, rod coater, blade coater and the like can be used.

  Next, after drying the positive electrode mixture applied on the positive electrode current collector 11a, the positive electrode mixture layer 11b is formed by compression molding using a roll press or the like. The drying apparatus is not particularly limited, and for example, standing drying, blower dryer, hot air dryer, infrared heater, far infrared heater, and the like can be used.

Note that the drying temperature of the positive electrode mixture is preferably set to a temperature equal to or higher than the melting point of poly (oxyethylene) or poly (oxypropylene). Specifically, when the melting start temperature of poly (oxyethylene) or poly (oxypropylene) observed by differential scanning calorimeter (DSC) is T ₁ and the drying temperature is T ₂ , It is preferable to heat and dry the positive electrode mixture so as to satisfy the relationship of T ₁ <T ₂ .

  More specifically, when poly (oxyethylene) is added to the positive electrode mixture, the heating temperature of the positive electrode mixture is determined by differential scanning calorimetry (using EXSTAR6000 DSC manufactured by SII Nano Technology Co., Ltd.). It is preferable that the melting start temperature of the observed poly (oxyethylene) is about 60 ° C. or higher.

  FIG. 4 shows a DSC peak measured using differential scanning calorimetry (using EXSTAR6000 DSC manufactured by SII Nanotechnology Inc.). In FIG. 4, the downward peak starting at about 60 ° C. indicates endotherm (melting).

<Negative electrode fabrication process>
Next, for example, a negative electrode active material and a binder are mixed to prepare a negative electrode mixture. This negative electrode mixture is dispersed in a solvent to form a slurry. Next, the slurry-like negative electrode mixture is uniformly applied to both surfaces of the negative electrode current collector 12a, dried, and then compression molded by a roll press or the like to form the negative electrode mixture layer 12b. In addition, as a coating device and a drying device, the same thing as the case where the above-mentioned positive electrode 11 is produced can be used.

<Electrolyte production process>
Next, an organic solvent and an electrolyte salt are mixed to prepare a plasticizer, and the matrix polymer is dissolved in the plasticizer. And this is uniformly apply | coated and impregnated on the positive mix layer 11b formed in both surfaces of the positive electrode collector 11a, and the negative mix layer 12b formed in both surfaces of the negative electrode collector 12a. Thereafter, for example, the organic solvent is vaporized and removed by leaving it at room temperature for a predetermined time.

<Winding process>
Next, the positive electrode 11 and the negative electrode 12 having the gel electrolyte layer 14 formed on both surfaces, and the separator 13 are sequentially laminated in the order of, for example, the negative electrode 12, the separator 13, the positive electrode 11, and the separator 13. The wound electrode element 1 is produced by winding the core around the core and winding it many times in the longitudinal direction.

<Sealing process>
Next, as shown in FIG. 1, the wound electrode element 1 is housed in an exterior material 2, and the surroundings are thermally welded and vacuum packaged. Through the above steps, a nonaqueous electrolyte secondary battery according to one embodiment of the present invention is manufactured.

  In the above-described example, the active material is mixed with a binder, an organic solvent, and the like to form a slurry, which is then applied onto the current collector and dried to produce the positive electrode 11 and the negative electrode 12. The method for manufacturing the electrode is not limited to the above example. For example, a method in which a known binder or the like is added to the active material and heated to apply, or a method in which a molded body electrode is formed by subjecting a material alone or a conductive material, or further mixed with a binder and subjected to a treatment such as molding. Is mentioned. In addition, regardless of the presence or absence of the binder, it is also possible to produce a strong electrode by pressure molding while applying heat to the active material.

According to one embodiment of the present invention, the following effects can be obtained.
Since the positive electrode mixture layer 12b comprises a positive electrode active material, a binder, a conductive agent, and poly (oxyethylene) or poly (oxypropylene), a stable surface coating that does not impair the characteristics of the positive electrode active material. It can be formed on the surface of the positive electrode active material. Therefore, in a state such as a high temperature overcharge state, generation of gas or the like due to oxidation / decomposition of the gel electrolyte can be suppressed. Therefore, it can suppress that the exterior material 2 which sealed the winding type electrode element 1 swells, and shape abnormality arises. That is, a high-quality nonaqueous electrolyte secondary battery excellent in shape stability can be realized. Further, it is possible to suppress the generation of gas or the like due to oxidation / decomposition of the gel electrolyte without depending on an additive that is difficult to control as in the conventional case. Moreover, even if it is a positive electrode active material which could not be used because of a large gas swell during high temperature overcharge, the swell can be significantly suppressed.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited only to these Examples.

Example 1
<Positive electrode fabrication process>
First, polyvinylidene fluoride having a specific surface area of 0.78 m ² / g and a LiCoO ₂ powder (positive electrode active material) of 90.97% by weight, graphite (conductive agent) of 6% by weight, and a molecular weight of about 300,000. A positive electrode mixture was prepared by mixing 3% by weight of a ride (binder) and 0.03% by weight of polyethylene oxide (PEO) having a molecular weight of about 200,000. The specific surface area was measured by the BET single point adsorption method (MacSorb HM model 1208 manufactured by Mountain Tech).

  Next, this positive electrode mixture was dispersed in N-methyl-2-pyrrolidone to form a slurry. And after apply | coating this uniformly on both surfaces of the aluminum foil 11a which is 20 micrometers in thickness and becomes a strip | belt shape as a positive electrode electrical power collector, it dried at 140 degreeC which is more than melting | fusing point of a polyethylene oxide. Thereafter, the positive electrode mixture layer 11b was produced by compression molding with a roll press.

<Negative electrode fabrication process>
First, 90% by weight of pulverized graphite powder (negative electrode active material) and 10% by weight of polyvinylidene fluoride as a binder were mixed to prepare a negative electrode mixture. Next, this negative electrode mixture was dispersed in N-methyl-2-pyrrolidone to form a slurry. Next, this was 20 micrometers in thickness used as a negative electrode electrical power collector, and it was made to dry after apply | coating uniformly on both surfaces of the strip-shaped copper foil 12a. And the negative mix layer 12b was produced by compression molding with a roll press machine.

<Electrolyte production process>
First, 12.5% by weight of ethylene carbonate (EC), 12.5% by weight of propylene carbonate (PC), and 5% by weight of LiPF ₆ as an electrolyte salt were mixed to prepare a plasticizer. On the other hand, 10% by weight of block copolymer poly (vinylidene fluoride-co-hexafluoropropylene) having a molecular weight of 600,000 and 60% by weight of diethyl carbonate were mixed and dissolved. Next, this was uniformly applied and impregnated on both surfaces of the positive electrode 11 and the negative electrode 12. Then, by leaving it at room temperature for 8 hours, diethyl carbonate was vaporized and removed, and a gel electrolyte layer 14 was produced.

<Winding process>
Next, the strip-shaped negative electrode 12 and the strip-shaped positive electrode 11 on which the gel electrolyte layer 14 is formed as described above, and the separator 13 which is a microporous polyethylene film having a thickness of 12 μm are combined with the negative electrode 12, the separator 13, 11 and separator 13 were laminated in this order, and the laminate was wound around a flat core and wound many times to produce a wound electrode element 1.

<Sealing process>
Finally, the wound electrode element 1 produced in this way was housed in an aluminum laminate film (exterior material) 2 in which an aluminum foil was sandwiched between polyolefin films, and vacuum packaged. The aluminum laminate sheet type non-aqueous electrolyte secondary battery was produced through the above steps.

Example 2
90.0% by weight of LiCoO ₂ powder having a specific surface area of 0.78 m ² / g, 6% by weight of graphite as a conductive agent, 3% by weight of polyvinylidene fluoride as a binder, and polyethylene oxide A battery was prepared in the same manner as in Example 1 except that 1.0% by weight was mixed to prepare a positive electrode mixture, applied, and dried at 140 ° C.

Example 3
LiCoO ₂ powder having a specific surface area of 0.78 m ² / g, 88.0% by weight, graphite as a conductive agent, 6% by weight, polyvinylidene fluoride as a binder, 3% by weight, polyethylene oxide A battery was prepared in the same manner as in Example 1 except that 3.0% by weight was mixed to prepare a positive electrode mixture, applied, and dried at 140 ° C.

Example 4
90.97% by weight of LiCoO ₂ powder having a specific surface area of 0.18 m ² / g, 6% by weight of graphite as a conductive agent, 3% by weight of polyvinylidene fluoride as a binder, and polyethylene oxide A battery was prepared in the same manner as in Example 1 except that 0.03% by weight was mixed to prepare a positive electrode mixture, applied, and dried at 140 ° C.

Example 5
90.0% by weight of LiCoO ₂ powder having a specific surface area of 0.18 m ² / g, 6% by weight of graphite as a conductive agent, 3% by weight of polyvinylidene fluoride as a binder, and polyethylene oxide A battery was prepared in the same manner as in Example 1 except that 1.0% by weight was mixed to prepare a positive electrode mixture, applied, and dried at 140 ° C.

Example 6
LiCoO ₂ powder having a specific surface area of 0.18 m ² / g, 88.0% by weight, graphite as a conductive agent, 6% by weight, polyvinylidene fluoride as a binder, 3% by weight, polyethylene oxide A battery was prepared in the same manner as in Example 1 except that 3.0% by weight was mixed to prepare a positive electrode mixture, applied, and dried at 140 ° C.

Example 7
90.97% by weight of LiCoO ₂ powder having a specific surface area of 0.78 m ² / g, 6% by weight of graphite as a conductive agent, 3% by weight of polyvinylidene fluoride as a binder, and polyethylene oxide A battery was prepared in the same manner as in Example 1 except that 0.03% by weight was mixed to prepare a positive electrode mixture, which was applied and dried at 90 ° C.

Example 8
90.0% by weight of LiCoO ₂ powder having a specific surface area of 0.78 m ² / g, 6% by weight of graphite as a conductive agent, 3% by weight of polyvinylidene fluoride as a binder, and polyethylene oxide A battery was prepared in the same manner as in Example 1 except that 1.0% by weight was mixed to prepare a positive electrode mixture, applied, and dried at 90 ° C.

Example 9
LiCoO ₂ powder having a specific surface area of 0.78 m ² / g, 88.0% by weight, graphite as a conductive agent, 6% by weight, polyvinylidene fluoride as a binder, 3% by weight, polyethylene oxide A battery was prepared in the same manner as in Example 1 except that 3.0% by weight was mixed to prepare a positive electrode mixture, applied, and dried at 90 ° C.

Example 10
90.97% by weight of LiCoO ₂ powder having a specific surface area of 0.18 m ² / g, 6% by weight of graphite as a conductive agent, 3% by weight of polyvinylidene fluoride as a binder, and polyethylene oxide A battery was prepared in the same manner as in Example 1 except that 0.03% by weight was mixed to prepare a positive electrode mixture, which was applied and dried at 90 ° C.

Example 11
90.0% by weight of LiCoO ₂ powder having a specific surface area of 0.18 m ² / g, 6% by weight of graphite as a conductive agent, 3% by weight of polyvinylidene fluoride as a binder, and polyethylene oxide A battery was prepared in the same manner as in Example 1 except that 1.0% by weight was mixed to prepare a positive electrode mixture, applied, and dried at 90 ° C.

Example 12
LiCoO ₂ powder having a specific surface area of 0.18 m ² / g, 88.0% by weight, graphite as a conductive agent, 6% by weight, polyvinylidene fluoride as a binder, 3% by weight, polyethylene oxide A battery was prepared in the same manner as in Example 1 except that 3.0% by weight was mixed to prepare a positive electrode mixture, applied, and dried at 90 ° C.

Example 13
90.97% by weight of LiCoO ₂ powder having a specific surface area of 0.78 m ² / g, 6% by weight of graphite as a conductive agent, 3% by weight of polyvinylidene fluoride as a binder, and polyethylene oxide A battery was prepared in the same manner as in Example 1 except that 0.03% by weight was mixed to prepare a positive electrode mixture, applied, and dried at 40 ° C.

Example 14
90.0% by weight of LiCoO ₂ powder having a specific surface area of 0.78 m ² / g, 6% by weight of graphite as a conductive agent, 3% by weight of polyvinylidene fluoride as a binder, and polyethylene oxide A battery was prepared in the same manner as in Example 1 except that 1.0% by weight was mixed to prepare a positive electrode mixture, which was applied and dried at 40 ° C.

Example 15
LiCoO ₂ powder having a specific surface area of 0.78 m ² / g, 88.0% by weight, graphite as a conductive agent, 6% by weight, polyvinylidene fluoride as a binder, 3% by weight, polyethylene oxide A battery was prepared in the same manner as in Example 1 except that 3.0% by weight was mixed to prepare a positive electrode mixture, applied, and dried at 40 ° C.

Example 16
90.97% by weight of LiCoO ₂ powder having a specific surface area of 0.18 m ² / g, 6% by weight of graphite as a conductive agent, 3% by weight of polyvinylidene fluoride as a binder, and polyethylene oxide A battery was prepared in the same manner as in Example 1 except that 0.03% by weight was mixed to prepare a positive electrode mixture, applied, and dried at 40 ° C.

Example 17
90.0% by weight of LiCoO ₂ powder having a specific surface area of 0.18 m ² / g, 6% by weight of graphite as a conductive agent, 3% by weight of polyvinylidene fluoride as a binder, and polyethylene oxide A battery was prepared in the same manner as in Example 1 except that 1.0% by weight was mixed to prepare a positive electrode mixture, which was applied and dried at 40 ° C.

Example 18
LiCoO ₂ powder having a specific surface area of 0.18 m ² / g, 88.0% by weight, graphite as a conductive agent, 6% by weight, polyvinylidene fluoride as a binder, 3% by weight, polyethylene oxide A battery was prepared in the same manner as in Example 1 except that 3.0% by weight was mixed to prepare a positive electrode mixture, applied, and dried at 40 ° C.

Example 19
LiCoO ₂ powder having a specific surface area of 0.92 m ² / g, 88.0% by weight, graphite as a conductive agent, 6% by weight, polyvinylidene fluoride as a binder, 3% by weight, polyethylene oxide A battery was prepared in the same manner as in Example 1 except that 3.0% by weight was mixed to prepare a positive electrode mixture, applied, and dried at 140 ° C.

Example 20
LiCoO ₂ powder having a specific surface area of 0.92 m ² / g, 88.0% by weight, graphite as a conductive agent, 6% by weight, polyvinylidene fluoride as a binder, 3% by weight, polyethylene oxide A battery was prepared in the same manner as in Example 1 except that 3.0% by weight was mixed to prepare a positive electrode mixture, applied, and dried at 90 ° C.

Example 21
LiCoO ₂ powder having a specific surface area of 0.75 m ² / g, 86.0% by weight, graphite as a conductive agent, 6% by weight, polyvinylidene fluoride as a binder, 3% by weight, polyethylene oxide A battery was prepared in the same manner as in Example 1 except that 5.0% by weight was mixed to prepare a positive electrode mixture, which was applied and dried at 140 ° C.

Example 22
LiCoO ₂ powder having a specific surface area of 0.75 m ² / g, 86.0% by weight, graphite as a conductive agent, 6% by weight, polyvinylidene fluoride as a binder, 3% by weight, polyethylene oxide A battery was prepared in the same manner as in Example 1, except that 5.0% by weight was mixed to prepare a positive electrode mixture, which was applied and dried at 90 ° C.

Example 23
LiCoO ₂ powder having a specific surface area of 0.18 m ² / g, 86.0% by weight, graphite as a conductive agent, 6% by weight, polyvinylidene fluoride as a binder, 3% by weight, polyethylene oxide A battery was prepared in the same manner as in Example 1 except that 5.0% by weight was mixed to prepare a positive electrode mixture, which was applied and dried at 140 ° C.

Example 24
LiCoO ₂ powder having a specific surface area of 0.18 m ² / g, 86.0% by weight, graphite as a conductive agent, 6% by weight, polyvinylidene fluoride as a binder, 3% by weight, polyethylene oxide A battery was prepared in the same manner as in Example 1, except that 5.0% by weight was mixed to prepare a positive electrode mixture, which was applied and dried at 90 ° C.

Example 25
LiCoO ₂ powder having a specific surface area of 0.78 m ² / g, 90.99% by weight, graphite as a conductive agent, 6% by weight, polyvinylidene fluoride as a binder, 3% by weight, and polyethylene oxide A battery was prepared in the same manner as in Example 1 except that 0.01% by weight was mixed to prepare a positive electrode mixture, which was applied and dried at 90 ° C.

Example 26
LiCoO ₂ powder having a specific surface area of 0.18 m ² / g, 90.99% by weight, graphite as a conductive agent, 6% by weight, polyvinylidene fluoride as a binder, 3% by weight, polyethylene oxide A battery was prepared in the same manner as in Example 1 except that 0.01% by weight was mixed to prepare a positive electrode mixture, which was applied and dried at 90 ° C.

Example 27
90.97% by weight of LiCoO ₂ powder having a specific surface area of 0.14 m ² / g, 6% by weight of graphite as a conductive agent, 3% by weight of polyvinylidene fluoride as a binder, and polyethylene oxide A battery was prepared in the same manner as in Example 1 except that 0.03% by weight was mixed to prepare a positive electrode mixture, which was applied and dried at 90 ° C.

Example 28
LiCoO ₂ powder having a specific surface area of 0.14 m ² / g, 88.0% by weight, graphite as a conductive agent, 6% by weight, polyvinylidene fluoride as a binder, 3% by weight, polyethylene oxide A battery was prepared in the same manner as in Example 1 except that 3.0% by weight was mixed to prepare a positive electrode mixture, applied, and dried at 90 ° C.

Comparative Example 1
Mixing 91.0% by weight of LiCoO ₂ powder having a specific surface area of 0.18 m ² / g, 6% by weight of graphite as a conductive agent, and 3% by weight of polyvinylidene fluoride as a binder. A battery was prepared in the same manner as in Example 1 except that the mixture was prepared, applied, and dried at 90 ° C.

Comparative Example 2
Mixing 91.0% by weight of LiCoO ₂ powder having a specific surface area of 0.78 m ² / g, 6% by weight of graphite as a conductive agent, and 3% by weight of polyvinylidene fluoride as a binder A battery was prepared in the same manner as in Example 1 except that the mixture was prepared, applied, and dried at 90 ° C.

  Next, the load characteristics and the high-temperature storage characteristics of the aluminum laminate sheet type non-aqueous electrolyte secondary batteries produced in Examples 1 to 28 and Comparative Examples 1 and 2 were evaluated by the following methods.

<Load characteristics>
A 1/2 hour rate discharge (2C) of theoretical capacity was performed and evaluated as follows. First, each battery was charged at a constant current and a constant voltage at 23 ° C. to an upper limit of 4.2 V for 3 hours. Next, a 5-hour rate discharge (0.2 C) was performed to a final voltage of 3.0V. The discharge capacity at this time was determined as a 0.2 C discharge capacity. Then, constant current constant voltage charge was again performed for 3 hours to the upper limit of 4.2V, and then 1/2 hour rate discharge (2C) was performed to the end voltage of 3.0V. The discharge capacity at this time was determined as 2C discharge capacity. The 2C discharge capacity with respect to the 0.2C discharge capacity was calculated as 100 fractions to obtain load characteristics.

<High temperature overcharge storage swelling measurement>
The change of the battery size when the charged battery was stored at high temperature was evaluated. First, each battery was charged with a constant current and a constant voltage at 23 ° C. for 3 hours up to an upper limit of 4.3 V. The thickness of each battery at this time was measured and used as the initial thickness. Then, after storing each battery in an 80 degreeC thermostat for 7 days, the battery thickness immediately after taking out from a thermostat was measured. The amount (change amount) obtained by subtracting the initial thickness from the thickness at this time was calculated as a 100 fraction with respect to the initial thickness, and was defined as the swelling rate.

Table 1 shows the evaluation results of the nonaqueous electrolyte secondary batteries of Examples 1 to 28 and Comparative Examples 1 and 2. In Table 1, “x”, “Δ”, and “◯” indicate the following evaluations.
×: Swelling rate 50% or more Δ: Swelling rate 30% or more and 49% or less, or Swelling rate 30% or less Load characteristic 59% or less ○: Swelling ratio 29% or less and load characteristic 60% or more

Table 1 shows the following.
(1) It can be seen that the non-aqueous electrolyte secondary batteries of Examples 1 to 28 have a remarkably small swelling rate during high-temperature overcharge storage as compared with the non-aqueous electrolyte secondary batteries of Comparative Examples 1 and 2. That is, it can be seen that by including poly (oxyethylene) in the positive electrode mixture layer 11b, it is possible to realize a non-aqueous chargeable secondary battery that is excellent in a swelling suppression effect during high-temperature overcharge storage.
(2) In the non-aqueous electrolyte secondary batteries of Examples 1 to 18 and 27 and 28, both good load characteristics and a swelling suppression effect during high-temperature overcharge storage can be achieved. It can be seen that the nonaqueous electrolyte secondary battery cannot achieve both the swelling suppression effect during high temperature overcharge storage and the load characteristics. That is, it can be seen that by adding 0.03 to 3.0% by weight of poly (oxyethylene) with respect to the positive electrode mixture composition, it is possible to provide a swelling suppression effect at high temperature overcharge storage without impairing load characteristics. Moreover, it turns out that the swelling suppression effect in high-temperature overcharge storage can be improved more by making the specific surface area of a positive electrode active material into the range of 0.14-0.78 m < ² > / g.

  The embodiment of the present invention has been specifically described above, but the present invention is not limited to the above-described embodiment, and various modifications based on the technical idea of the present invention are possible.

  For example, the numerical values given in the above-described embodiment are merely examples, and different numerical values may be used as necessary.

  In the above-described embodiment, the case where poly (oxyethylene) or poly (oxypropylene) is dispersed in the positive electrode mixture layer 11b is shown as an example, but at least a part of the surface of the positive electrode mixture layer 11b is made of poly. You may make it coat | cover with (oxyethylene) or poly (oxypropylene). Note that it is preferable to disperse poly (oxyethylene) or poly (oxypropylene) in the positive electrode mixture layer 11 b in consideration of more effectively suppressing the swelling of the exterior material 2.

  In the above-described embodiment, the case where poly (oxyethylene) or poly (oxypropylene) is dispersed in the positive electrode mixture layer 11b is shown as an example. However, a poly (oxyethylene) derivative or a poly (oxypropylene) derivative is used. Alternatively, these complexes may be used.

  Moreover, in the above-described embodiment, the case where the present invention is applied to a laminated sheet type non-aqueous electrolyte secondary battery is shown as an example. However, the present invention is not particularly limited with respect to the battery shape. The present invention can be applied to non-aqueous electrolyte secondary batteries having various shapes such as a square shape, a coin shape, and a button shape.

  In the above-described embodiment, the present invention is applied to a wound type nonaqueous electrolyte secondary battery in which an electrolyte layer is interposed between a positive electrode and a negative electrode, and the positive electrode and the negative electrode are wound. However, the present invention can also be applied to a stacked nonaqueous electrolyte secondary battery in which a positive electrode, an electrolyte layer, and a negative electrode are sequentially stacked. The present invention can also be applied to a thin or square non-aqueous electrolyte secondary battery manufactured using a winding method.

  In the above-described embodiment, an example in which the present invention is applied to a non-aqueous electrolyte secondary battery including a gel electrolyte as an electrolyte has been described. However, a non-electrolytic electrolyte including a solid electrolyte containing an electrolyte salt as an electrolyte is illustrated. The present invention can also be applied to a water electrolyte secondary battery. The present invention can also be applied to a non-aqueous electrolyte secondary battery including a non-aqueous electrolyte as an electrolyte. In addition, for solid electrolytes and gel electrolytes, electrolytes with different components can be used for each of the positive electrode and the negative electrode. However, when one type of electrolyte is used, a nonaqueous electrolyte solution in which an electrolyte salt is dissolved in a nonaqueous solvent is also used. Is possible.

  As the solid electrolyte, any inorganic solid electrolyte or polymer solid electrolyte can be used as long as the material has lithium ion conductivity. Examples of the inorganic solid electrolyte include lithium nitride and lithium iodide. The polymer solid electrolyte is composed of an electrolyte salt and a polymer compound that dissolves the electrolyte salt. The polymer compound is an ether polymer such as poly (ethylene oxide) or the same cross-linked product, a poly (methacrylate) ester, or an acrylate. Alternatively, they can be copolymerized or mixed in the molecule.

It is a disassembled perspective view which shows the example of 1 structure of the nonaqueous electrolyte secondary battery by one Embodiment of this invention. 2 is an exploded perspective view showing a configuration example of a wound electrode element 1. FIG. 2 is a cross-sectional view showing a configuration example of a wound electrode element 1. FIG. It is a graph which shows the DSC peak measured using differential scanning calorimetry.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Winding type electrode element, 2 ... Exterior material, 3, 4 ... Lead, 11 ... Positive electrode, 11a ... Positive electrode collector, 11b ... Negative electrode mixture layer, 12 ... Negative electrode, 12a ... Negative electrode current collector, 12b ... Negative electrode mixture layer, 13 ... Separator, 14 ... Gel electrolyte layer

Claims (30)

A positive electrode mixture containing a positive electrode active material and poly (oxyethylene) or poly (oxypropylene). The positive electrode mixture according to claim 1, further comprising a binder. The positive electrode mixture according to claim 1, wherein the positive electrode active material is a lithium transition metal composite oxide. The lithium transition metal composite oxide, any of the general formula _{Li x M y N z O 2} (M Co, one of Ni, N is Co, Mn, Ni, Cr, Fe, V, Al, B, and Mg Or a combination of two or more thereof, 0.05 ≦ x ≦ 1.10, y> 0, 0.80 ≦ y + z ≦ 1.00.) Positive electrode mixture. The positive electrode mixture according to claim 3, wherein the poly (oxyethylene) or poly (oxypropylene) is contained in an amount of 0.03 to 3 parts by weight. 4. The positive electrode mixture according to claim 3, wherein the lithium transition metal composite oxide has a specific surface area of 0.14 m ² / g or more and 0.78 m ² / g or less. A positive electrode and a negative electrode for electrochemically doping and dedoping lithium; and
An electrolyte interposed between the positive electrode and the negative electrode,
The non-aqueous electrolyte secondary battery, wherein the positive electrode has a positive electrode mixture containing a lithium transition metal composite oxide and poly (oxyethylene) or poly (oxypropylene). The nonaqueous electrolyte secondary battery according to claim 7, wherein the positive electrode mixture further contains a binder. The lithium transition metal composite oxide, any of the general formula _{Li x M y N z O 2} (M Co, one of Ni, N is Co, Mn, Ni, Cr, Fe, V, Al, B, and Mg Or a combination of two or more thereof, 0.05 ≦ x ≦ 1.10, y> 0, 0.80 ≦ y + z ≦ 1.00.) Non-aqueous electrolyte secondary battery. The non-aqueous electrolyte secondary battery according to claim 7, wherein the poly (oxyethylene) or poly (oxypropylene) is contained in an amount of 0.03 to 3 parts by weight. The nonaqueous electrolyte secondary battery according to claim 7, wherein the lithium transition metal composite oxide has a specific surface area of 0.14 m ² / g or more and 0.78 m ² / g or less. 8. The nonaqueous electrolyte secondary battery according to claim 7, wherein the poly (oxyethylene) or poly (oxypropylene) is dispersed in the positive electrode mixture. 8. The lithium transition metal composite oxide has a particle shape, and the poly (oxyethylene) or poly (oxypropylene) covers at least a part of the surface of the particle. Non-aqueous electrolyte secondary battery. The non-aqueous electrolyte secondary battery according to claim 7, wherein the positive electrode includes a positive electrode current collector and a positive electrode mixture layer formed on the positive electrode current collector and made of the positive electrode mixture. . The nonaqueous electrolyte secondary battery according to claim 7, further comprising a separator interposed between the positive electrode and the negative electrode. The non-aqueous electrolyte secondary battery according to claim 15, wherein the positive electrode and the negative electrode having the separator interposed therebetween are wound. The nonaqueous electrolyte secondary battery according to claim 7, further comprising an exterior material that houses the positive electrode and the negative electrode in which the electrolyte is interposed. The nonaqueous electrolyte secondary battery according to claim 17, wherein the exterior material is formed by laminating an adhesive layer on a metal layer. 19. The nonaqueous electrolyte secondary battery according to claim 18, wherein the adhesive layer is a polymer film. The non-aqueous electrolyte secondary battery according to claim 7, wherein the electrolyte is made of a gelled polymer matrix. A positive electrode and a negative electrode for electrochemically doping and dedoping lithium; and
In a method for producing a non-aqueous electrolyte secondary battery comprising an electrolyte interposed between the positive electrode and the negative electrode,
Producing a positive electrode using a positive electrode mixture containing lithium transition metal composite oxide and poly (oxyethylene) or poly (oxypropylene);
Producing a negative electrode using a negative electrode active material;
And a step of interposing an electrolyte between the positive electrode and the negative electrode. A method for producing a non-aqueous electrolyte secondary battery. The method for producing a nonaqueous electrolyte secondary battery according to claim 21, wherein a binder is further added to the positive electrode mixture. The lithium transition metal composite oxide, any of the general formula _{Li x M y N z O 2} (M Co, one of Ni, N is Co, Mn, Ni, Cr, Fe, V, Al, B, and Mg Or a combination of two or more thereof, 0.05 ≦ x ≦ 1.10, y> 0, 0.80 ≦ y + z ≦ 1.00.) A method for producing a non-aqueous electrolyte secondary battery. The method for producing a nonaqueous electrolyte secondary battery according to claim 21, wherein the poly (oxyethylene) or poly (oxypropylene) is contained in an amount of 0.03 to 3 parts by weight. The method for producing a non-aqueous electrolyte secondary battery according to claim 21, wherein a specific surface area of the lithium transition metal composite oxide is 0.14 m ² / g or more and 0.78 m ² / g or less. Before the step of producing the positive electrode, the lithium transition metal composite oxide was mixed with poly (oxyethylene) or poly (oxypropylene), and the poly (oxyethylene) or poly (oxypropylene) was dispersed. The method for producing a nonaqueous electrolyte secondary battery according to claim 21, further comprising a step of producing a positive electrode mixture. The method for producing a nonaqueous electrolyte secondary battery according to claim 21, further comprising a step of heat-treating the positive electrode after the step of manufacturing the positive electrode. In the step of heat-treating the positive electrode, when the melting start temperature of the poly (oxyethylene) or poly (oxypropylene) observed by differential scanning calorimetry is T ₁ and the temperature of the heat treatment is T ₂ , T ₁ <nonaqueous electrolyte secondary battery manufacturing method according to claim 27, wherein the performing the heat treatment so as to satisfy the relation of T _2. In the step of producing the positive electrode, a positive electrode mixture composed of a lithium transition metal composite oxide and poly (oxyethylene) or poly (oxypropylene) is dispersed in a solvent to form a slurry, and the mixture is formed on the positive electrode current collector. The method for producing a nonaqueous electrolyte secondary battery according to claim 21, wherein the positive electrode is produced by applying and drying. When drying the positive electrode mixture applied on the positive electrode current collector, a melting initiation temperature of poly observed by differential scanning calorimetry (oxyethylene) or poly (oxypropylene) and T _1, the drying 30. The positive electrode mixture applied on the positive electrode current collector is heated and dried so as to satisfy the relationship of T ₁ <T ₂ when the temperature is T _2. Of manufacturing a non-aqueous electrolyte secondary battery.

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