JP2008277196A - Manufacturing method of electrode plate for nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of an electrode plate for a nonaqueous electrolyte secondary battery in which an electrode quality and high rate discharge characteristics, temperature characteristics, cycle characteristics are improved to attain a higher reliability. <P>SOLUTION: The manufacturing method of an electrode plate of a nonaqueous electrolyte secondary battery includes a process in which, in an sheet-shaped cathode plate 25 or an anode plate 30 of the nonaqueous electrolyte secondary battery 10 having a metallic foil as a current collector, at least in a condition of an electrode-winding hoop, a residual solvent, a thickener or a binder are dried or heat-treated accompanying thermal denaturation, and the drying and heat-treatment is conducted on the electrode plates 25, 30 at least by conducting a direct current. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  In the non-aqueous electrolyte lithium secondary battery, the present invention uses a metal oxide capable of inserting and extracting lithium as a positive electrode active material, a carbon material and / or an inorganic material containing elements such as tin and silicon as a negative electrode active material. Further, the present invention relates to a method for producing an electrode plate for a non-aqueous electrolyte secondary battery that is carried on a current collector and particularly relates to drying or heat treatment.

  As an example of a method for producing an electrode plate for a non-aqueous electrolyte secondary battery, one that performs hot air drying, far-infrared drying, vacuum drying, drying in an inert gas atmosphere, or the like for drying or heat treatment is known. (For example, see Patent Document 1, Patent Document 2, Patent Document 3, and Patent Document 4).

  On the other hand, a sintered substrate manufacturing method in an alkaline storage battery such as nickel-cadmium is known as a heating technique from the inside rather than from the outside of the electrode plate (see, for example, Patent Document 5).

JP 2005-251481 A JP 2005-267997 A JP 2001-250536 A Japanese Patent No. 3191614 Japanese Patent Publication No. 55-19283

  In the conventional method for producing an electrode plate for a nonaqueous electrolyte secondary battery disclosed in Patent Document 1, Patent Document 2, Patent Document 3, and Patent Document 4, all of them are heated from outside, heat conduction, and radiation. Is due to. For example, when drying is performed in a wound roll state in which the electrode is wound around the electrode, temperature unevenness occurs between the outer periphery of the electrode winding body and the inside when the temperature is increased or decreased. Thereby, for example, when heat treatment is performed at a predetermined temperature at which the binder is melted, the expansion rate of the mixture layer, that is, the thickness difference between the electrode winding outer peripheral portion and the inner peripheral portion is large after the heat treatment is finished. Deformation due to peeling or expansion of the mixture layer is observed.

  Moreover, in the manufacturing method of the electrode plate for nonaqueous electrolyte secondary batteries disclosed in Patent Document 5, slurry (mixture) is applied and filled as a drying method after slurry application and filling in the initial step of producing the porous sintered base. Electricity is passed through the core plate of the band-shaped metal porous core plate. And it is the construction method which dries a slurry to 5-8% order of moisture content by the generated Joule heat, Comprising: The homogeneous drying and the short-time processing effect are shown. In this technique, the core (winding core) is energized, and the mixture layer is hardly energized. Therefore, a considerably large current is required to obtain the Joule heat generation, and there is a concern in terms of energy cost. In addition, in the heat treatment of electrode plates that have been processed by slurry application, dried by other predetermined methods, and processed by press molding or other residual moisture and residual solvent to the order of several hundreds of ppm, the electrode plates are combined for the following reasons. This is unsuitable because the electrical properties of the agent layer are uneven.

  In the mixture member that is in contact with the core body by energization of the core body and the portion of the mixture that is separated from the core body in the thickness direction, the reaction activation action of the mixture layer by the forced electronic conduction called energization and the heat of residual moisture and solvent In addition, a large difference is caused by the heat treatment effect caused by electrolysis. For this reason, in the case of heat-treating an electrode plate whose water content or residual solvent is on the order of several hundred ppm from the wet state after slurry application and filling, there is a problem in that the unevenness of the energization occurs in the mixture layer.

  The present invention relates to a heat treatment method for an electrode plate for a non-aqueous electrolyte secondary battery and the like, particularly when it is performed in an electrode winding hoop state, and the deformation of the electrode plate that occurs because the outer peripheral portion of the entire winding hoop is rapidly heated from the inside. Instability of electrode quality such as warp, warp, crack or uneven thickness, temperature variation in each part of electrode winding hoop during temperature rising process, that is, reduction in production efficiency such as expansion of temperature rising time to specified temperature due to temperature rising variation, electrode plate It is an object of the present invention to achieve a drastic improvement in the above-described problems, such as variations in decomposition and evaporability due to the temperature and the degree of reduced pressure of the heat-treated material inside, that is, a reduction in removal efficiency.

  The present invention has been made in view of the above-described problems, and its object is to improve the electrode quality, the high-rate discharge characteristics, the temperature characteristics, and the cycle characteristics, so that it is more reliable for non-aqueous electrolyte secondary batteries. It is providing the manufacturing method of the electrode plate for nonaqueous electrolyte secondary batteries which can obtain an electrode plate.

  Specific means for solving the above problems are as follows.

  1) In a sheet-like positive electrode plate or negative electrode plate obtained by applying a positive electrode mixture or a negative electrode mixture to a current collector that is a metal foil of a non-aqueous electrolyte secondary battery, at least in the state of electrode winding hoop, residual solvent and thickener Or it is a manufacturing method of the electrode plate for nonaqueous electrolyte secondary batteries regarding the heat processing accompanied by drying or heat denaturation of a binder, Comprising: This drying or heat processing heat-processes by supplying at least a direct current to the said electrode plate.

2) The energization current density is 0.02 A / mm ^{2 to} 12 A / mm ² with respect to the electrode cross-sectional area.

  3) The said heat processing is performed at 50 to 350 degreeC.

  4) In the electrode winding forward direction of the sheet-like electrode plate, between the core material that is the mixture uncoated portion on the winding core side of the hoop and the core material that is the mixture portion on the winding outer peripheral side or the mixture uncoated portion. A substance having a resistance equal to or less than that of the core material is connected to both ends of the wire as an energization terminal, and direct current is energized between the winding core side and the winding outer peripheral side to perform energization heat treatment.

  5) A core material portion, which is a mixture uncoated portion, is provided at both ends of the winding hoop width direction, which is a direction perpendicular to the electrode winding direction of the sheet electrode plate, from the winding core side to the winding outer peripheral side. A substance having a resistance equal to or less than that of the core material is connected to the core material, which is a solid part of the agent, as a current-carrying terminal, a direct current is applied, and an electric heating process is performed.

  6) The drying or the heat treatment is performed in an inert gas.

  7) The drying or the heat treatment is performed in a fluid atmosphere having an oxygen concentration of 0% to 1%.

  8) The drying or the heat treatment is performed in a vacuum reduced pressure atmosphere.

  9) The drying or the heat treatment is performed in a heat treatment atmosphere in which a fluid atmosphere and a vacuum decompression atmosphere are combined.

  10) The material of the winding core tube of the electrode hoop of the sheet-like electrode plate, which is connected between the electrode core tube and the electrode collector metal foil plain portion with a lower resistance than the electrode current collector, An energizing electrode terminal is connected between the electrode core tube and at least a part of the electrode winding hoop to conduct energization heat treatment.

  11) At least one of heating from the inside of the core tube of the electrode winding hoop of the sheet-like electrode plate and heating from the outer periphery of the electrode winding is combined with electrode current heating.

  12) The positive electrode current collector is an aluminum foil, and the negative electrode current collector is a copper foil or a nickel foil.

  13) a positive electrode having a positive electrode mixture containing a positive electrode active material capable of occluding and releasing lithium and a positive electrode current collector, and a negative electrode mixture containing a negative electrode active material capable of occluding and releasing lithium and a negative electrode current collector A separator disposed between the positive electrode and the negative electrode, a non-aqueous electrolyte composition, and an exterior member that accommodates these.

  14) The electrode to be heat-treated by heating contains at least polyvinylidene fluoride, N-methylpyrrolidene, carboxymethylcellulose, and styrene butanediene rubber.

  In the present invention, a mixture is applied to an electrode current collector (core body), dried by a predetermined drying method, and then the electrode mixture is pressed by a predetermined press to increase the volume density of the mixture. With respect to the electrode plate whose residual moisture or residual solvent is on the order of several hundred ppm, in the state where the electrode plate is rolled up, the current collector of the winding core and the mixture or current collector of the outer periphery of the winding A current-carrying terminal made of a material having a resistance smaller than that of the current collector is connected between the current collectors. As a result, it is possible to energize not only the current collector but also the electrode mixture layer, and not only the Joule heat generated by the current collector current but also the resistance heat generated by the current mixture layer and the electrolysis of residual water are newly introduced. It is established as an electrode plate heat treatment technology by utilizing the headline.

  In other words, the reaction activation effect of the mixture layer by forced electronic conduction such as energization, thermal denaturation of the binder, and removal of residual moisture and solvent by heat and electrolysis to a few ppm order reduce factors that can cause reaction resistance. It is possible to improve the battery characteristics and safety. Therefore, the manufacturing method of the electrode plate for nonaqueous electrolyte secondary batteries which is stable and favorable with respect to battery charging / discharging can be provided.

  In the present invention, as a heat treatment technique for solving the above problems, an electric heating technique for realizing core material energization and mixture energization is provided as a basic solution. That is, since not only the core material in the electrode plate but also the mixture layer is energized, the object to be treated in the electrode plate is thermally or electrolyzed, the treatment is efficiently performed, and the residual solvent and thickener are dried and The heat treatment effect accompanied by binder modification can also be achieved with high efficiency, and a drastic solution to the above problems can be achieved. In addition, as an additional effect, the electrical characteristics of the mixture (active material) are improved, that is, the reaction of the mixture layer is activated. Therefore, the electrical characteristics of the electrode are improved, that is, the battery characteristics are improved by improving the electronic conductivity. Is planned.

  In terms of manufacturing technology, it is possible to apply a direct current to the electrode plate to heat it alone or in combination with heater heating in the heat treatment apparatus or core heating from inside the electrode winding core tube, inert gas, dry air, By intensively studying the combination with an atmosphere control technology such as vacuum, it is possible to provide a method for producing an electrode plate for a non-aqueous electrolyte secondary battery with further improved electrode quality, productivity, and battery performance.

  The first content of the present invention relates to a heat treatment method for a sheet-like electrode plate using a metal foil of a non-aqueous electrolyte secondary battery as a current collector, and is a wound roll formed by winding the sheet-like electrode plate. In this embodiment, a current-carrying terminal made of a material having a resistance smaller than that of the current collector is connected between the current collector at the winding core and the mixture or current collector at the outer periphery of the winding. In this way, the mixture layer energization is generated in addition to the current collector energization, and the electrode plate heat treatment technology is established by utilizing the functions of Joule heat generation, resistance heat generation and electrolysis.

Next, the second content is related to the atmosphere control around the electrode during the heat treatment.
(1) An inert gas such as dry nitrogen or argon or dry air having a dew point of about −30 ° C. or less.
(2) A vacuum under which the fluid in the atmosphere is almost completely removed.
By interposing at least one of these two atmospheres as a heat treatment atmosphere, it is possible to more effectively remove residual moisture and solvent in the electrode mixture layer to the order of several ppm. Although details will be described in the examples, the atmosphere control is more preferably repeated in combination of (1) and (2).

  According to the method for producing an electrode plate for a non-aqueous electrolyte secondary battery of the present invention, the electrode quality, high-rate discharge characteristics, temperature characteristics, and cycle characteristics are improved, thereby providing a more reliable non-aqueous electrolyte secondary battery electrode. The manufacturing method of the electrode plate for nonaqueous electrolyte secondary batteries which can obtain a board can be provided.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

  1 is a partially broken external perspective view of a non-aqueous electrolyte secondary battery manufactured using the method for manufacturing an electrode plate for a non-aqueous electrolyte secondary battery according to an embodiment of the present invention, and FIG. It is sectional drawing of the wound body in a water electrolyte secondary battery.

  As shown in FIG. 1 and FIG. 2, the non-aqueous electrolyte secondary battery 10 manufactured by using the method for manufacturing a non-aqueous electrolyte secondary battery electrode plate according to an embodiment of the present invention has an open upper surface. A wound body 12 is disposed inside a bottomed cylindrical battery can 11 around a center pin (not shown) 13 and sealed by a battery lid 14.

  The battery can 11 is composed of, for example, a SUS can or a nickel-plated iron can, and the wound body 12 is wound in the same manner via a wound separator 15 and 16 containing an electrolyte. And the negative electrode 18 has the structure arrange | positioned facing.

  The battery cover 14 is provided with a safety valve mechanism 20 together with a heat sensitive resistance element (Positive Temperature Coefficient: PTC element) 19 on the inside, and is attached by caulking the battery can 14 with a gasket 21. Has been. That is, the inside of the nonaqueous electrolyte secondary battery 10 is sealed by the battery can 11 and the battery lid 14.

  The safety valve mechanism 20 is electrically connected with the battery lid 14 via the heat sensitive resistance element 19, and the internal pressure of the nonaqueous electrolyte secondary battery 10 becomes a certain level or more due to internal short circuit or external heating. In addition, the electrical connection between the battery lid 14 and the wound body 12 is cut, for example, when the built-in disk plate is inverted. Here, when the temperature rises, the thermal resistance element 19 limits the current by increasing the resistance value and prevents abnormal heat generation due to a large current.

  The wound body 11 has a configuration in which a strip-shaped (thin plate) positive electrode 17 and a negative electrode 18 are arranged to face each other via separators 15 and 16 containing an electrolyte, and these are wound.

  A positive electrode lead 22 and a negative electrode lead (not shown) made of, for example, aluminum are connected to the positive electrode 17 and the negative electrode 18 of the wound body 11, respectively. The positive electrode lead 22 is welded to the safety valve mechanism 20 and electrically connected to the battery lid 14. The negative electrode lead is directly welded and electrically connected to the battery can 11.

  Here, the positive electrode 17 is, for example, a positive electrode current collector 25 having a first main surface 23 serving as an inner surface and a second main surface 24 serving as an outer surface in a winding structure. The material layer 26 and the outer-surface positive electrode active material layer 27 are formed on the second main surface 24 side, respectively.

  The inner-surface positive electrode active material layer 26 and the outer-surface positive electrode active material layer 27 are selected and configured according to the intended battery configuration and characteristics using a material that can be doped / undoped with lithium as described later. Is preferred. Further, it is not always necessary to provide both on the inner surface and the outer surface. The positive electrode current collector 25 can be made of, for example, aluminum (Al), nickel (Ni), stainless steel (SUS), or the like.

The inner surface positive electrode active material layer 26 and the outer surface positive electrode active material layer 27 include a positive electrode active material, and may include a conductive agent such as a carbonaceous material and a binder such as polyvinylidene fluoride as necessary. . As the positive electrode active material, for example, a lithium-containing metal composite oxide containing a sufficient amount of lithium (Li), for example, lithium represented by the general formula LixMo ₂ and a transition metal is preferable. Since the lithium-containing metal composite oxide can generate a high voltage and has a high density, it is possible to further increase the capacity of the secondary battery. In the general formula, M is one or more transition metals, and for example, at least one selected from the group consisting of cobalt, nickel, and manganese is preferable.

X in the general formula varies depending on the charge / discharge state of the battery, and is usually a value in the range of 0.053 ≦ x ≦ 1.10. Specific examples of such a lithium-containing metal composite oxide include LiCoO _{2 and} LiNO ₂ . In addition, any 1 type may be used for a positive electrode active material, and 2 or more types may be mixed and used for it. Further, as will be described later, the positive electrode 17 is formed of impurities in the inner surface positive electrode active material layer 26 and the outer surface positive electrode active material layer 27, that is, different from each other by the method for manufacturing the electrode plate for a nonaqueous electrolyte secondary battery according to this embodiment. Reduction of metal components and moisture is attempted.

  Further, the inner surface positive electrode active material layer 26 and the outer surface positive electrode active material layer 27 of the positive electrode 17 have a charge / discharge capacity equivalent to 250 mAh or more per 1 g of the negative electrode carbonaceous material in a steady state (for example, after repeating charge / discharge about 5 times). It is necessary to include Li, and it is desirable to include Li corresponding to a charge / discharge capacity of 300 mAh or more, and it is preferable to include Li corresponding to a charge / discharge capacity of 330 mAh or more.

  On the other hand, the negative electrode 18 is, for example, a negative electrode current collector 30 having a first main surface 28 serving as an inner surface and a second main surface 29 serving as an outer surface in a winding structure. The layer 31 is formed with an outer-surface negative electrode active material layer 32 on the second main surface 29 side.

  As a material constituting the inner surface negative electrode active material layer 31 and the outer surface negative electrode active material layer 32 constituting the negative electrode 18, a carbonaceous material capable of doping / dedoping (desorption / desorption) lithium, or lithium and an alloy can be formed. Or an alloy compound containing the metal. The negative electrode current collector can be made of, for example, copper (Cu).

  Examples of carbonaceous materials include non-graphitizable carbon, graphites such as artificial graphite and natural graphite, pyrolytic carbons, cokes (pitch coke, needle coke, petroleum coke, etc.), glassy carbons, organic high carbon At least one kind of carbonaceous material such as molecular compound fired body (phenol resin, furan resin, etc., fired at an appropriate temperature and carbonized), activated carbon, fibrous carbon, or the like can be used. Moreover, you may include the material which does not contribute to charging / discharging.

  As will be described later, the negative electrode 18 is produced by the method for manufacturing the electrode plate for a non-aqueous electrolyte secondary battery according to the present embodiment. Impurities in the inner surface negative electrode active material layer 31 and the outer surface negative electrode material layer 32, that is, different metal components And reduction of moisture.

Examples of the alloy compound include those containing at least one metal that can be alloyed with lithium. Specifically, when the metal element capable of forming an alloy with lithium is M, the chemical formula M _x M ′ _y Li _z (M ′ is one or more metal elements other than the Li element and the M element, _x > 0, _y As a compound having a composition of ≧ 0, _z ≧ O). Note that in this specification, elements such as B, Si, and As, which are semiconductor elements, are also included in the metal elements.

  Examples of such metals and metal compounds include Mg, B, Al, Ga, In, Si, Ge, Sn, Pb, Sb, Bi, Cd, Ag, Zn, Hf, Zr, and Y, and those. Alloy compounds of Li, Al-Li, Li-Al-M (M: 2A, 3B, 4B, consisting of one or more of transition metal elements), AlSb, CuMgSb, and the like.

In particular, it is preferable to use a group 4B typical element as an element capable of forming an alloy with lithium, and more preferably Si or Sn. For example, M _x Si, M _x Sn (M excludes Si or Sn, respectively) And compounds represented by one or more metal elements). Specifically, SiB ₄ , SiB ₆ , Mg ₂ Si, Mg ₂ Sn, Ni ₂ Si, TiSi ₂ , MoSi ₂ , CoSi ₂ , NiSi ₂ , CaSi ₂ , CrSi ₂ , Cu ₅ Si, FeSi ₂ , MnSi ₂ NbSi ₂ , TaSi ₂ , VSi ₂ , WSi ₂ , ZnSi _2, etc.

Moreover, in the nonaqueous electrolyte secondary battery 10 according to the present embodiment, the inner surface negative electrode active material layer 31 and the outer surface negative electrode active material layer 32 are configured by a 4B group compound other than carbon containing one or more nonmetallic elements. You can also Specifically, for example, SiC, Si ₃ N ₄ , Si ₂ N ₂ O, Ge ₂ N ₂ O, SiO _x (0 <x ≦ 2), SnO _x (0 <x ≦ 2), LiSiO, LiSnO, etc. Can be.

  Examples of the method for producing the negative electrode active material layer using these materials include a mechanical alloying method, a method in which raw material compounds are mixed and heat-treated in an inert atmosphere, a melt spinning method, a gas atomizing method, a water atomizing method, and the like. Although it is mentioned, it is not limited to these. In addition, each material may or may not be pulverized, or two or more materials may be mixed.

  The doping of lithium into the material of the negative electrode active material layer may be performed electrochemically in the battery after the battery is manufactured, or after the battery is manufactured or before the battery is manufactured, the positive electrode 17 or a lithium source other than the positive electrode May be supplied electrochemically, or may be electrochemically doped, synthesized as a lithium-containing material at the time of material synthesis, and contained in the negative electrode 18 at the time of battery production.

  The separators 15 and 16 are for preventing a short circuit due to physical contact between the positive electrode 17 and the negative electrode 18 while allowing lithium ions to pass through. For example, the separators 15 and 16 are made of a fine film such as a polyethylene film (PE) or a polypropylene film (PP). It is composed of a porous polyolefin film or the like. In order to ensure safety, these separators 15 and 16 preferably have a function of closing a hole by heat melting at a predetermined temperature (for example, 120 ° C.) or higher to increase resistance and cut off current.

  The separators 15 and 16 are impregnated with an electrolytic solution (not shown). The electrolytic solution in the present embodiment includes, for example, a nonaqueous solvent and a lithium salt that is an electrolyte salt dissolved in the solvent, and may include various additives as necessary.

  Examples of the non-aqueous solvent include propylene carbonate, ethylene carbonate, diethyl carbonate, methyl ethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3. -Dioxolane, 4-methyl-1,3-dioxolane, diethyl ether, sulfolane, methyl sulfolane, acetonitrile, propylnitrile, anisole, acetate or propionate.

  In addition, any 1 type of these may be used for a solvent, and 2 or more types may be mixed and used for it. When mixing and using, the structure which added asymmetrical chain carbonates, such as methyl ethyl carbonate and methyl propyl carbonate, as a 2nd component especially using ethylene carbonate as a main solvent is suitable. Furthermore, a mixed solvent of methyl ethyl carbonate and dimethyl carbonate can be used. In this case, the volume ratio to be mixed is preferably in the range of ethylene carbonate: second component hot metal = 7: 3 to 3: 7.

  Moreover, when using the above-mentioned mixed solvent as a 2nd component solvent, it is preferable to make a volume ratio into the range of methyl ethyl carbonate: dimethyl carbonate = 2: 8-9: 1. Addition of the second component suppresses decomposition of the main solvent, improves conductivity and improves current characteristics, reduces freezing point of electrolyte and improves low temperature characteristics, reaction with lithium metal The effect that safety | security falls and safety is improved is acquired.

As the electrolyte, LiPF ₆ is suitable, but any of those used in this type of battery can be used. For example, as a lithium salt, LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiCH ₃ SO ₃ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) 2, LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (C ₄ F ₉ SO ₂ ) (CF ₃ SO ₂ ), LiCl or LiBr. Among these, LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiCH ₃ SO ₃ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ or LiN (C ₄ F ₉ SO ₂ ) (CF ₃ SO ₂ ) is preferable, and LiPF ₆ or LiBF ₄ is particularly preferable. Any one of the lithium salts may be used, or a mixture of two or more may be used.

  Next, taking the case of obtaining such a nonaqueous electrolyte secondary battery 10 as an example, a method for manufacturing the electrode plate for a nonaqueous electrolyte secondary battery according to this embodiment will be described. In addition, the manufacturing method of the electrode plate for nonaqueous electrolyte secondary batteries which concerns on this invention is applicable to any of the positive electrode and negative electrode which comprise the nonaqueous electrolyte secondary battery 10. FIG. Further, as described above, the material, the amount thereof, and the like are appropriately selected according to the purpose. In the present embodiment, an example in which the negative electrode is manufactured using graphite as the main component of the active material pave will be described.

  With reference to FIG.3 and FIG.4, the manufacturing method of the electrode plate for nonaqueous electrolyte secondary batteries is demonstrated. FIG. 3 is an external perspective view for explaining a first method of the method for producing a nonaqueous electrolyte secondary battery electrode plate according to the present invention, and FIG. 4 is a method for producing a nonaqueous electrolyte secondary battery electrode plate according to the present invention. It is an external appearance perspective view explaining the 2nd method.

  As shown in FIG. 3, the first method of manufacturing the electrode plate for a nonaqueous electrolyte secondary battery is a mixture uncoated portion on the core side of the hoop in the electrode winding forward direction of the sheet-like electrode plate 101. A copper wire having a resistance equal to or less than that of the core material 102 is connected to both ends between the core material 102 and the uncoated solid portion 103 from which the aluminum foil has been removed as a current-carrying terminal 104. Then, a direct current is supplied from the direct current power source 105 to perform an energization heating process.

  As shown in FIG. 4, the second method of manufacturing the electrode plate for a nonaqueous electrolyte secondary battery includes a winding core side at both ends of the winding hoop width direction that is perpendicular to the electrode winding direction of the sheet electrode plate 101. A core material portion 106 that is a mixture uncoated portion is provided from the winding outer periphery side, and a material having a resistance equal to or less than that of the core material 102 is connected as an energization terminal to the core material 102 that is a mixture uncoated portion at both ends in the hoop width direction. Then, a direct current is supplied from the direct current power source 105 to perform an energization heating process.

Here, electric current density to the electrode cross-sectional area, the core material in the positive electrode plate is an aluminum (Al) ^{is, 0.02A / mm 2 ~8A / mm} 2, preferably 0.05A ^/ mm 2 ~8A ^/ In the negative electrode plate of mm ² and the core material of copper (Cu), it is 0.1 A / mm ^{2 to} 12 A / mm ² , preferably 0.5 A / mm ^{2 to} 12 A / mm ² , and these ranges 0.02 A / mm ^{2 to} 12 A / mm ² including the heat treatment is performed at 50 ° C. to 350 ° C. Further, the atmosphere is a fluid atmosphere or a vacuum reduced pressure atmosphere that is dried or heat-treated in an inert gas and has an oxygen concentration of 0% to 1%, and is a heat treatment atmosphere that combines a fluid atmosphere and a vacuum reduced pressure atmosphere. Then, at least one of heating from the inside of the winding core tube of the electrode winding hoop of the sheet-like electrode plate and heating from the outer periphery of the electrode winding is performed in combination with electrode energization heating.

  As a specific example of the method for producing a non-aqueous electrolyte secondary battery electrode plate, first, natural graphite is pulverized using a hammer mill, pin mill, ball mill, jet mill, etc., and finally the active material layer of the battery Graphite particles which are the main components of are obtained. Specifically, for example, when a hammer mill is used, it is preferable to perform pulverization for 20 minutes or more at a rotation speed of 4000 to 5000 rpm. The supply of natural graphite and the discharge of graphite particles are preferably performed by a method involving the graphite particles in an air stream.

  The obtained graphite particles are dispersed in 3 parts by weight of polyvinylidene fluoride (PVDF) as a binder and N-methyl-2-pyrrolidone (NMP) as a solvent to obtain a paste-like kneaded body (slurry). In this way, the kneaded body preparation step is performed.

Thereafter, the obtained kneaded body is applied onto a thin plate (strip-shaped) copper foil current collector, and then dried by a spray dryer, for example, at a temperature of 80 ° C. to 110 ° C. under nitrogen or an inert gas. Processing is performed, and the kneaded body is dried to obtain a negative electrode in which an active material layer is formed on the current collector. If necessary, you may press-mold according to the target volume density. It may be before press molding or after press molding, but with the wound negative electrode plate winding hoop, terminals are connected to the uncoated portion at the beginning and end of winding in the forward direction with respect to the electrode winding direction. Connection was performed, and direct current was applied at a current density of 1 A / cm ² in the electrode cross-sectional area direction, and heat treatment was performed for 1 hour. The atmosphere during the heat treatment was a nitrogen atmosphere.

  In this way, a negative electrode was produced. In the manufacturing method of the electrode plate for a nonaqueous electrolyte secondary battery according to the present embodiment, the negative electrode is manufactured by the above procedure.

Next, a mixture of lithium carbonate 0.5 molar and cobalt 1 mole carbonate, after obtaining the LiCoO ₂ was fired for 5 hours in a 900 ° C. in air, grinding the LiCoO _2, obtained by a laser diffraction method 50 A LiCoO ₂ powder having a% cumulative particle size of 15 μm was prepared. Thereafter, 91 parts by weight of a mixture comprising 95 parts by weight of LiCoO ₂ powder and 5 parts by weight of lithium carbonate powder, 6 parts by weight of graphite as a conductive agent, and 3 parts by weight of polyvinylidene fluoride as a binder were prepared to prepare a positive electrode mixture. And dispersed in a solvent (N-methylpyrrolidone) to form a slurry (paste).

This positive electrode mixture slurry was uniformly applied to both surfaces of a 20 μm-thick strip-shaped aluminum foil that finally became a positive electrode current collector, and dried and press-compressed to produce a thin plate-like positive electrode. It may be before press molding or after press molding, but with the wound positive electrode plate winding hoop, terminals are connected to the uncoated portion at the beginning and end of winding in the forward direction with respect to the electrode winding direction. Connection was performed, and a direct current was applied at a current density of 10 A / cm ² in the electrode cross-sectional area direction, and overheating was performed for 5 hours. The atmosphere during the heat treatment was a nitrogen atmosphere. In this way, a positive electrode was produced.

  Thereafter, the prepared negative electrode and positive electrode and a separator made of a microporous polypropylene film having a thickness of 25 μm were laminated in the order of the negative electrode, the separator, the positive electrode, and the separator and then wound many times, and the spiral winding with an outer diameter of 18 mm The body was made.

  This spiral wound body is housed in a nickel-plated iron battery can, insulating plates are provided on both the upper and lower surfaces of the spiral electrode, and the aluminum positive electrode lead is led out from the positive electrode current collector to the battery lid. The nickel negative electrode lead was led out from the negative electrode current collector and welded to the bottom of the battery can.

Thereafter, an electrolytic solution composition in which LiPF ⁶ is dissolved in a nonaqueous solvent (for example, an equal volume mixed solvent of ethylene carbonate and diethyl carbonate) at a rate of 1 mol / dm ³ in a battery can in which the wound body is housed. The positive electrode, the negative electrode, and the separator were impregnated with the electrolyte structure.

  Subsequently, the battery can was caulked through an insulating sealing gasket whose surface was coated with asphalt, thereby fixing the safety valve mechanism having a current interruption function, the PTC element, and the battery lid, and the inside was hermetically sealed. A nonaqueous electrolyte secondary battery was obtained.

(Example)
Next, examples carried out for confirming the effects of the method for producing the electrode plate for a nonaqueous electrolyte secondary battery according to the present invention will be described.

  In the embodiment, as shown in FIG. 5, a mode in which the mixture layer 4 is energized using the positive electrode plate 1, the terminal 2, and the DC power source 3 (mixture energization), as shown in FIG. 6. Two types were produced: a mode of energizing the core material 5 (core material energization). The electrode mixture area is 5 cm × 10 cm, the battery size is ICR18650 described in JIS C8711, and the battery capacity is 2500 mAh. In each embodiment, resistance measurement was performed between the points PQ and between the points RS. Here, the electrode plate mixture area S is S = W (5 cm) × L (10 cm), and the temperature immediately before the electrode plate experiment is 20 ° C. In addition, after battery preparation, after initial charge, and after performing aging at 45 degrees C or less, it implemented.

(Measurement of heat generation characteristics)

(Discharge rate measurement / low temperature characteristics)
Next, three types of Examples 1, 2, and 3 in which the positive electrode plate was energized and the negative electrode plate was energized, heated and vacuum heated, and the positive plate was heated with hot air. Three types of Examples 4, 5, and 6 in which current heating, hot air heating, and vacuum heating were performed on the negative electrode plate, vacuum heating on the positive electrode plate, and vacuum heating on the negative electrode plate The discharge rate measurement and low temperature characteristics of Comparative Example 1 were examined. The heating temperature is 130 ° C. for the positive electrode and 130 ° C. for the negative electrode.

(Measurement of moisture content in electrode)
Next, three types of Examples 1, 2, and 3 in which the positive electrode plate was energized and the negative electrode plate was energized, heated and vacuum heated, and the positive plate was heated with hot air. Three types of Examples 4, 5, and 6 in which current heating, hot air heating, and vacuum heating were performed on the negative electrode plate, vacuum heating on the positive electrode plate, and vacuum heating on the negative electrode plate The moisture content in each electrode of Comparative Example 1 was examined. The heating temperature was 130 ° C. for the positive electrode and 130 ° C. for the negative electrode. The moisture measurement was carried out using a Karl Fischer moisture meter, and the eviction temperature was 250 ° C.

(Cycle characteristic measurement)
Next, the cycle characteristics of Examples 1 and 4 and Comparative Example 1 were examined.
As is apparent from Table 1, in energization heating, the mixture energization is more efficient than the core energization due to the addition of resistance heating and electrolysis in the mixture layer in addition to the Joule heat generation of the core. It can be seen that heat treatment is achieved.

  Further, as is apparent from Table 2, when the heat treatment was performed on at least one of the positive electrode and the negative electrode, good tendency was obtained in terms of battery characteristics of discharge rate characteristics, low temperature characteristics and cycle characteristics. . In particular, in the electrical heating treatment for the positive electrode, the electrical characteristics as the positive electrode plate were improved, and the voltage drop due to IR drop at the initial stage of discharge at low temperature was suppressed, so the low temperature discharge characteristics were greatly improved. Furthermore, in terms of the heat treatment effect on each of the positive and negative electrode plates, the current heating treatment was generally good, and then the discharge characteristics and charge / discharge cycle characteristics improved in the order of hot air and vacuum. From this result, it is considered that the presence or absence of the heat conduction medium, the heat treatment efficiency, and the effect of improving the electrical characteristics as the electrode plate under the heat treatment appeared.

  Further, as is apparent from Table 3, those subjected to electrode current heating have extremely small residual moisture values. This is presumably because water was electrolyzed in addition to heat due to the mixture energization effect. Furthermore, since heat treatment is performed in the electrode state, the electrode core body is annealed and softened, so that the positive and negative electrode plates immediately before forming the battery are newly provided with stretchability (extended margin is generated). This well follows the expansion and contraction in the length direction of the electrode plate based on the expansion and contraction in the electrode thickness direction accompanying the charge / discharge cycle.

  As can be seen from FIG. 7, the cycle characteristics are reduced due to the reduction of bleeding into the electrolyte solution due to the loss of moisture in the electrode, that is, the reactivity improvement due to the acid content increase suppressing effect and the effect of imparting elongation to the electrode described above. Adhesiveness and followability between the current collector and the expansion / contraction of the mixture layer accompanying charging / discharging can be achieved. Thereby, it is guessed that the current collection effect as an electrode plate was maintained and the characteristics were improved. Therefore, it was shown that the electrode heat treatment method described in this embodiment is effective as a manufacturing method that enables the above-described effects.

  As described above, according to the method for manufacturing an electrode plate for a non-aqueous electrolyte secondary battery, the electrode quality, high rate discharge characteristics, temperature characteristics, and cycle characteristics are improved, and the non-aqueous electrolyte is more reliable. An electrode plate for a secondary battery can be obtained. Specifically, the moisture content in the electrode mixture can be reduced to less than 20 ppm, the improvement effect can be seen in the high-rate discharge characteristics and the bass characteristics, and the cycle characteristics can be improved.

  In addition, this invention is not limited to embodiment mentioned above, In the range which does not deviate from the summary of this invention, it can change suitably. In addition, the material, shape, dimension, numerical value, form, number, arrangement location, and the like of each component in the above-described embodiment are arbitrary and are not limited as long as the present invention can be achieved.

It is a partial fracture appearance perspective view of a nonaqueous electrolyte secondary battery manufactured using a manufacturing method of a nonaqueous electrolyte secondary battery electrode plate of one embodiment of the present invention. It is sectional drawing of the wound body in the non-aqueous electrolyte secondary battery shown in FIG. It is an external appearance perspective view explaining the 1st method of the manufacturing method of the electrode plate for nonaqueous electrolyte secondary batteries which concerns on this invention. It is an external appearance perspective view explaining the 2nd method of the manufacturing method of the electrode plate for nonaqueous electrolyte secondary batteries which concerns on this invention. It is sectional drawing of the mixture energization form used for the Example. It is sectional drawing of the core material electricity supply form used for the Example. It is a graph which shows cycling characteristics.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Nonaqueous electrolyte secondary battery 11 Battery can 12 Winding body 13 Center pin 14 Battery cover 15, 16 Separator 17 Positive electrode 18 Negative electrode 19 Thermal resistance element 20 Safety valve mechanism 21 Gasket 22 Positive electrode lead 25 Positive electrode collector (electrode plate)
26, 27 Positive electrode active material layer 30 Negative electrode current collector (electrode plate)
31, 32 Negative electrode active material layer

Claims (14)

In a sheet-like positive electrode plate or negative electrode plate obtained by applying a positive electrode mixture or a negative electrode mixture to a current collector, which is a metal foil of a nonaqueous electrolyte secondary battery, a residual solvent, a thickener or a binder at least in an electrode hoop state A method for producing an electrode plate for a non-aqueous electrolyte secondary battery related to heat treatment involving drying or heat denaturation of
A method for producing an electrode plate for a non-aqueous electrolyte secondary battery, wherein the drying or heat treatment is performed by heating at least a direct current through the electrode plate. The method for producing an electrode plate for a nonaqueous electrolyte secondary battery according to claim 1, wherein the energization current density is 0.02 A / mm ^{2 to} 12 A / mm ² with respect to the electrode cross-sectional area.   The method for producing an electrode plate for a nonaqueous electrolyte secondary battery according to claim 1, wherein the heat treatment is performed at 50C to 350C.   In the electrode winding forward direction of the sheet-like electrode plate, both ends between a core material which is a mixture uncoated portion on the winding core side of the hoop and a core material which is a mixture portion or a mixture uncoated portion on the winding outer peripheral side. Further, a material having a resistance equal to or less than that of the core material is connected as an energization terminal, and a direct current energization is performed between the winding core side and the winding outer peripheral side to perform energization heat treatment. The manufacturing method of the electrode plate for nonaqueous electrolyte secondary batteries of description.   A core material portion that is a mixture uncoated portion is provided from both the winding core side to the winding outer periphery side at both ends of the winding hoop width direction that is perpendicular to the electrode winding direction of the sheet-like electrode plate, and the mixture uncoated region at both ends of the hoop width direction 2. The non-aqueous electrolyte according to claim 1, wherein a material having a resistance equal to or less than that of the core material is connected to the core material, which is a part, as a current-carrying terminal, a direct current is applied, and a heat treatment is performed. A method for producing an electrode plate for a secondary battery.   The method for producing an electrode plate for a nonaqueous electrolyte secondary battery according to claim 1, wherein the drying or the heat treatment is performed in an inert gas.   The method for producing an electrode plate for a non-aqueous electrolyte secondary battery according to claim 1, wherein the drying or the heat treatment is performed in a fluid atmosphere having an oxygen concentration of 0% to 1%.   The method for producing an electrode plate for a nonaqueous electrolyte secondary battery according to claim 1, wherein the drying or the heat treatment is performed in a vacuum and reduced pressure atmosphere.   The non-aqueous electrolyte 2 according to claim 1, wherein the drying or the heat treatment is performed in a heat treatment atmosphere in which the fluid atmosphere according to claim 6 or 7 and the vacuum decompression atmosphere according to claim 8 are combined. A method for producing an electrode plate for a secondary battery.   A material for the winding core tube of the electrode hoop of the sheet-like electrode plate, which is connected between the electrode core tube and the electrode collector metal foil plain portion with lower resistance than the electrode current collector, The method for producing an electrode plate for a non-aqueous electrolyte secondary battery according to claim 1, wherein an energization heat treatment is performed by connecting an energization electrode terminal between the tube and at least a part of the electrode winding hoop.   2. The nonaqueous electrolyte according to claim 1, wherein at least one of heating from the inside of the core tube of the electrode winding hoop of the sheet electrode plate and heating from the outer periphery of the electrode winding is combined with electrode current heating. A method for producing an electrode plate for a secondary battery.   The method for producing an electrode plate for a nonaqueous electrolyte secondary battery according to claim 1 or 7, wherein the positive electrode current collector is an aluminum foil, and the negative electrode current collector is a copper foil or a nickel foil.   A positive electrode having a positive electrode mixture containing a positive electrode active material capable of occluding and releasing lithium and a positive electrode current collector, and a negative electrode mixture containing a negative electrode active material capable of occluding and releasing lithium and a negative electrode current collector The negative electrode which has, The separator arrange | positioned between these positive electrodes and a negative electrode, a nonaqueous electrolyte composition, and the exterior member which accommodates these, The any one of Claims 1-12 characterized by the above-mentioned. A method for producing an electrode plate for a nonaqueous electrolyte secondary battery according to one item.   The non-water according to any one of claims 1 to 13, wherein the electrode subjected to the heat treatment contains at least polyvinylidene fluoride, N-methylpyrrolidene, carboxymethylcellulose, and styrene butanediene rubber. Manufacturing method of electrode plate for electrolyte secondary battery.

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