JP2006228515A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery with excellent heat resistance and charge and discharge characteristics, through restraint of deterioration of the electrolyte secondary battery due to heat. <P>SOLUTION: The nonaqueous electrolyte secondary battery, provided with electrodes each consisting of an electrode active material and a binder, of which, the binder is of water-soluble polyacrylamide. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a non-aqueous electrolyte secondary battery.

  The use of electrolyte secondary batteries is increasing due to the characteristics such as high energy density and light weight, and various characteristics are required.

  In particular, improvement in heat resistance is required for non-aqueous electrolyte secondary batteries.

  A small electrolyte secondary battery such as a coin type (button type) uses reflow soldering when mounted on a substrate. Solder used for reflow is being replaced by lead-free solder that does not contain lead, and the reflow temperature is further increased.

  The conventional non-aqueous electrolyte secondary battery does not use a material that takes heat resistance into, and thus has a drawback of causing deterioration of charge / discharge characteristics during reflow soldering. Apply solder cream etc. to the part to be soldered on the printed circuit board and place the part on the part, or supply the solder balls to the soldered part after placing the part, and the soldered part is soldered A method is used in which soldering is performed by melting a solder by passing a printed circuit board on which components are mounted in a furnace in a high temperature atmosphere set to be 200 to 260 ° C., for example, at a melting point of 200 to 260 ° C. or higher. (Hereinafter referred to as reflow soldering) This is because the temperature in the battery reaches 200 ° C. or higher for several minutes and further reaches 240 to 260 ° C. for several seconds to several tens of seconds due to reflow. Even at such a high temperature, the conductive agent is required to have extremely high stability that does not cause a chemical reaction with other substances in an electrolyte to which a voltage is applied.

  In addition, large-sized nonaqueous electrolyte secondary batteries such as a cylindrical shape and a box shape are also required to be stored and used in a high temperature environment, and improvement in heat resistance is required. For this reason, there is a need for a conductive agent that is stable even at high temperatures.

  Among them, the binder has many required properties such as being insoluble in the electrolyte solution in addition to heat resistance, not causing swelling and shape change, and having wettability of the electrolyte solution. .

On the other hand, polyacrylic acid (PAC) is a commonly used binder for non-aqueous electrolyte secondary batteries.
), And various polyacrylic acid neutralized products, polyvinyl alcohol, carboxymethyl cellulose, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyamideimide, styrene butadiene rubber, polyolefins (polyethylene, polypropylene), etc. Molecule is used. (For example, see Patent Document 1).
JP-A-2004-335188 (3rd to 4th terms, Fig. 1)

  Commonly used binders used in conventional non-aqueous electrolyte secondary batteries are polyacrylic acid (PAC), neutralized polyacrylic acid, polyvinyl alcohol (PVA), carboxymethylcellulose , Polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyamideimide, styrene butadiene rubber, polyolefins (polyethylene, polypropylene), and the like.

  However, when a non-aqueous electrolyte secondary battery is manufactured using a heat-resistant battery component using the binder used in these non-aqueous electrolyte secondary batteries and heated, the battery resistance value increases. Battery characteristics such as battery capacity reduction and cycle characteristic deterioration. The degree of deterioration of battery characteristics due to heating varies greatly depending on the type of binder. This is because the type and physical properties of the binder greatly affect the deterioration of battery characteristics due to reflow heating.

  An object of the present invention is to solve the above problems and provide a non-aqueous electrolyte secondary battery excellent in heat resistance and charge / discharge characteristics.

  The nonaqueous electrolyte secondary battery of the present invention is a nonaqueous electrolyte secondary battery having an electrode composed of an electrode active material and a binder, wherein the binder is a water-soluble polyacrylamide. .

  The nonaqueous electrolyte secondary battery of the present invention is a nonaqueous electrolyte secondary battery having a positive electrode made of a positive electrode active material and a positive electrode binder, and a negative electrode made of a negative electrode active material and a negative electrode binder. In addition, at least one of the positive electrode binder and the negative electrode binder is water-soluble polyacrylamide.

  The present invention has a great feature in that water-soluble polyacrylamide is used as a binder. By using this binder, deterioration of the battery due to heat can be suppressed, the battery capacity is improved over the conventional non-aqueous electrolyte secondary battery compatible with reflow soldering, cycle characteristics are good, and high temperature storage characteristics are achieved. In addition, a non-aqueous electrolyte secondary battery compatible with reflow soldering can be provided.

  FIG. 1 shows a cross-sectional view of a nonaqueous electrolyte secondary battery according to the present invention.

  Positive electrode 101 made of positive electrode active material and binder for positive electrode, positive electrode case 102, negative electrode 103 made of negative electrode active material and binder for negative electrode, negative electrode case 104, lithium foil 105, separator 106 for separating positive and negative electrodes, gasket 107 and electrolyte 108. The positive electrode or the negative electrode includes an electrode active material that occludes and releases lithium ions and a binder present between particles of the active material.

  The binder, which is a feature of the present invention, is one of the composite materials contained in the positive electrode and the negative electrode. Commonly used binders used in conventional non-aqueous electrolyte secondary batteries are polyacrylic acid (PAC), polyacrylic acid neutralized product, polyvinyl alcohol (PVA), carboxymethylcellulose , Polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyamideimide, styrene butadiene rubber, polyolefins (polyethylene, polypropylene), and the like. However, if the binder used in these non-aqueous electrolyte secondary batteries is used in non-aqueous electrolyte secondary batteries that can be reflow soldered, the resistance value increases after reflow soldering due to heating during reflow soldering, Deterioration due to heat has occurred, such as a decrease in the temperature and the failure to obtain a good cycle.

  For this reason, various binders have been studied. The properties required for binders of non-aqueous electrolyte secondary batteries with conventional binders (heat resistance, non-flammability, chemical stability, physical stability) , Electrochemical stability) was not found. Therefore, a non-aqueous electrolyte secondary battery with better battery characteristics could be obtained by using polyacrylamide with excellent chemical and physical stability for organic solvents as the binder material. .

  Polyacrylamide (PAA), like polyvinyl alcohol (PVA), is easily soluble in water and difficult to dissolve in organic solvents, so it does not swell due to electrolyte infiltration, and therefore the positive and negative electrodes inside the battery. This is thought to be due to the fact that the decrease in mechanical strength caused by swelling of the binder of the mixture and the capacity deterioration due to deformation of the positive / negative electrode mixture are remarkably suppressed. In addition, since electrolyte infiltration and swelling are further affected by heating such as reflow, battery characteristics deteriorate after reflow soldering with a binder that easily infiltrates and swells in an organic solvent or has low heat resistance. On the other hand, using polyacrylamide as the binder seems to have suppressed deterioration caused by heat.

  The bulk specific gravity of polyacrylamide used as a binder was measured according to JIS K 6721. As the binder, the present invention was particularly effective when the bulk specific gravity by this measurement was 0.5 to 0.7.

The molecular weight of polyacrylamide was determined by dissolving poacrylamide in a 1 mol / l sodium nitrate solution and measuring the viscosity at 30 ° C. with an Ubbelohbe viscometer to determine the intrinsic viscosity (η). From the intrinsic viscosity (η), the average molecular weight (MW) was obtained from Formula 1.
η [dl / g] = 3.73 * 10 ⁻⁴ (MW) ^0.66 (Expression 1)
The present invention was particularly effective when the molecular weight measured by this method was 10 million to 18 million.

  The present invention does not particularly specify a positive electrode active material, but the positive electrode active material preferably contains any of Mn oxide, Mo oxide, Ti oxide, and niobium pentoxide.

  The present invention is effective even when the negative electrode active material is a Li—Al alloy and the binder is only the positive electrode. Moreover, although it is preferable to use SiO as a negative electrode active material, it is not limited to this.

Hereinafter, the present invention will be described in detail by way of examples.
Example 1
Example 1 is a case where MoO ₃ is used as the positive electrode active material and SiO is used as the negative electrode active material. A positive electrode, a negative electrode and an electrolytic solution prepared as described below were used. The battery was 4 mm in outer diameter and 1.4 mm in thickness.

The positive electrode active material is obtained by pulverizing commercially available MoO ₃ , graphite as a conductive agent, polyacrylamide (PAA) having a molecular weight of 13 million and a bulk specific gravity of 0.6 as a positive electrode binder, and a weight ratio of MoO ₃ : graphite: polyacrylamide = 50. : 45: 5 was mixed to make a positive electrode mixture, and then 7 mg of this positive electrode mixture was pressure-molded into ² ton / cm ² pellets with a diameter of 2.5 mm. Thereafter, the negative electrode 103 obtained in the same manner as the positive electrode mixture was bonded and integrated with the negative electrode case 104 using an electrode current collector made of a conductive resin adhesive containing carbon as a conductive filler (negative electrode unit). Thereafter, heat treatment was performed in the atmosphere at 250 ° C. for 12 hours. Further, a lithium foil 105 punched out to a diameter of 2.0 mm and a thickness of 0.2 mm was pressure-bonded on the pellet to obtain a lithium-negative electrode laminated electrode.

A nonwoven fabric made of glass fiber having a thickness of 0.2 mm was dried and then punched out to a diameter of 3.0 mm to obtain a separator 106. A gasket 107 made of PEEK was used. As the electrolytic solution 108, first, a solvent in which ethylene carbonate (EC): γ-butyllactone (γBL) was mixed at a volume ratio of 1: 1 was prepared. Thereto was dissolved 1.0 mol / l of lithium borofluoride (LiBF ₄ ) to prepare an electrolytic solution. 4.2 μL of this electrolytic solution was put in a battery can, the positive electrode unit and the negative electrode unit were stacked, and caulked and sealed to produce a battery.
(Examples 2 to 4)
In the same manner as in Example 1, positive electrodes having positive electrode active materials of Li ₄ Mn ₅ O ₁₂ , Li ₄ Ti ₅ O ₁₂ , and Nb ₂ O ₅ were produced, and batteries were produced.
(Example 5)
In the same manner as in Example 1, the negative electrode active material was Li—Al alloy, and the Li—Al alloy was directly pressed onto the negative electrode case 104 to form a negative electrode, thereby producing a battery.
(Example 6)
In the same manner as in Example 1, an electrolyte solution having a solute of LiCF ₃ SO ₃ was produced, and a battery was produced.
(Example 7)
In the same manner as in Example 1, an electrolyte was prepared in which the solute was LiCF ₃ SO ₃ and the electrolytic solvent was ethylene carbonate (EC): tetraethylene glycol dimethyl ether (TG) = 1: 1, to prepare a battery.

In order to investigate whether or not each of the 10 batteries produced as described above can withstand the reflow temperature, a reflow test was performed by heating at preheating 180 ° C. for 10 minutes and heating at 260 ° C. for 1 minute. The sample after heating was subjected to measurement of battery height, internal resistance, battery capacity and cycle characteristics in order to examine swelling. The reflowed battery was connected to a 2V power source and held in a constant temperature bath at 60 ° C for 20 days, then removed and measured for battery height measurement, internal resistance measurement, battery capacity, and withstand voltage storage characteristics. . The charge and discharge conditions in the battery capacity and cycle characteristics were as follows. Charging was performed by a constant current low voltage method with a maximum current of 25 μA, a constant voltage of 3.3 V, and a charging time of 72 hours, and discharging was performed at a constant current of 5 μA and a final voltage of 1 V.
(Examples 8 to 9)
In the same manner as in Example 1, pellets were prepared by using polyacrylic acid having a bulk specific gravity of 0.4 and 0.8 as the binder used for the positive electrode / negative electrode active material, respectively, to prepare a battery.
(Examples 10 to 13)
In the same manner as in Example 1, pellets using binders used for the positive electrode / negative electrode active material with molecular weights of 1 million, 10 million, 18 million, and 20 million were produced to produce batteries.
(Comparative Examples 1-3)
In the same manner as in Example 1, pellets were produced using polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and polyacrylic acid (PAC) as the binder materials used for the positive and negative electrode active materials. A battery was produced.

  Table 1 shows the production conditions and experimental results of the examples and comparative examples.

  In Table 1, ◎ indicates good characteristics, ○ indicates that there is no problem in practical use, △ indicates that there are some problems such as slight swelling of the battery and slight deterioration of capacity, and × indicates a problem in characteristics. It is not in practical use.

As shown in Examples 1 to 4 in Table 1, when the binder is made of polyacrylamide (PAA) and has a bulk height of 0.6 and a molecular weight of 13 million, any positive electrode active material can be used for reflow. There was no increase in internal resistance or deterioration in capacity due to. Also, as shown in Example 5, good characteristics were obtained even when a Li—Al alloy was used as the negative electrode active material. Furthermore, as shown in Examples 6 to 7, good characteristics were obtained even when the solvent and solute of the electrolytic solution were changed. As for the withstand voltage storage characteristics of Examples 1 to 13, the capacity and the like were hardly deteriorated, and good characteristics were obtained. In addition, the swelling of the batteries was 0.03 mm or less, and there was no problem. Similarly, good results were obtained with an electrolyte solution in which the solute was LiCF ₃ SO ₃ and the electrolytic solvent was ethylene carbonate (EC): tetraethylene glycol dimethyl ether (TG) = 1: 1.

  On the other hand, as shown in Comparative Examples 1 and 2 in Table 1, when the material of the binder is polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), or polyacrylic acid (PAC), polyacrylamide is used. The increase in internal resistance and degradation of capacity after reflow were greater than when (PAA) was used.

  From the above, it was found that when water-soluble polyacrylamide was used as the binder, a nonaqueous electrolyte secondary battery having excellent heat resistance was obtained. In particular, it is preferable to use water-soluble polyacrylamide having a bulk specific gravity of 0.5 to 0.7 and a molecular weight of 10 million to 18 million.

As shown in Table 1, the material used as the binder is particularly preferably water-soluble polyacrylamide (PAA) having a bulk specific gravity of 0.5 to 0.7 and a molecular weight of 10 to 18 million.
The following is desired for the parts other than the binder of the nonaqueous electrolyte secondary battery.

  As an electrolyte of the electrolytic solution, γ-butyl lactone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl formate, 1,2-dimethoxyethane, tetrahydrofuran, dioxofuran, dimethylformamide, A single solvent such as diethylene glycol / dimethyl ether, tetraethylene glycol / dimethyl ether, or a mixed solvent can be used.

  In order to perform reflow soldering, it is known that it is stable at the reflow temperature to use a nonaqueous solvent having a boiling point of 200 ° C. or higher at normal pressure as the electrolytic solution. In combination with the positive and negative electrodes, it was favorable to use alone or in combination selected from ethylene carbonate (EC) and γ-butyllactone (γBL).

  In addition to the organic solvent, a polymer can be used. As the polymer, those conventionally used in general can be used. For example, polyethylene oxide (PEO), polypropylene oxide, polyethylene glycol diacrylate cross-linked product, polyvinylidene fluoride, polyphosphazene cross-linked product, polypropylene glycol diacrylate cross-linked product Body, polyethylene glycol methyl ether acrylate crosslinked body, and polypropylene glycol methyl ether acrylate crosslinked body are preferably used.

  Examples of main impurities present in the electrolytic solution (nonaqueous solvent) include moisture and organic peroxides (for example, glycols, alcohols, carboxylic acids). Each of the impurities is considered to form an insulating film on the surface of the active material and increase the interface resistance of the electrode. Therefore, the cycle life and capacity may be affected. In addition, self-discharge during storage at high temperatures (60 ° C or higher) may increase. Room temperature molten salt is particularly greatly deteriorated by moisture. For this reason, it is preferable to reduce the impurities as much as possible in the electrolytic solution containing a non-aqueous solvent. Specifically, the moisture is preferably 50 ppm or less, and the organic peroxide is preferably 1000 ppm or less.

Supported salts include lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium borofluoride (LiBF ₄ ), lithium arsenic hexafluoride (LiAsF ₆ ), lithium trifluoromethanesulfonate (LiCF ₃ One or more salts such as SO ₃ ), bistrifluoromethylsulfonylimide lithium [LiN (CF ₃ SO ₂ ) ₂ ], lithium salts (electrolytes) such as thiocyanate and aluminum fluoride can be used.
In reflow soldering, lithium hexafluorophosphate (LiPF ₆ ), lithium borofluoride (LiBF ₄ ), and lithium trifluoromethanesulfonate (LiPF ₄ ), which are fluorine-containing supporting salts such as LiClO ₄ LiCF ₃ SO ₃ ) is stable both thermally and electrically. The amount dissolved in the non-aqueous solvent is preferably 0.5 to 3.0 mol / l.
In the present invention, the positive electrode active material is not particularly selected. As the positive electrode active material, titanium oxide, lithium-containing titanium oxide, molybdenum oxide, manganese oxide, lithium-containing manganese oxide, lithium-containing cobalt oxide, niobium An oxide, a lithium-containing niobium oxide, or the like can be used.

Further, the present invention does not select the type of the negative electrode active material, but the negative electrode includes lithium alloys such as lithium-aluminum, carbon doped with lithium, metal oxide doped with lithium (for example, SiO, WO ₂ , WO ₃ )), effective for lithium-doped carbon, lithium-doped Si, and the like.

  In particular, the use of silicon oxides such as SiO and Si as SiOy (0 <y <2) as the negative electrode active material minimizes the deterioration of the negative electrode due to charge / discharge, and the battery has very good charge / discharge cycle characteristics. Can be produced. In addition, when a battery is made using a metal oxide such as SiO as a negative electrode, a lithium-containing silicon oxide represented by LixSiOy (x ≧ 0, 2> y> 0) in which lithium ions to be moved are previously stored in SiO and There is a need to. In this case, by increasing the lithium content, the potential on the negative electrode side decreases, and the charge / discharge curve tilts. At the same time, the battery can be charged even at a high voltage, and can be charged in a wide voltage range. If too much lithium is added, lithium metal will be abnormally deposited on the electrode during charging, so x is particularly preferably in the range of 4.0 ≦ x ≦ 4.5. In this way, even when lithium-contacted or electrochemically doped silicon oxide is used for the negative electrode, rapid reaction does not occur even at reflow temperatures exceeding 200 ° C due to the inclusion of ionic liquid in the electrolyte. It was.

  As the separator, an insulating film having a large ion permeability and a predetermined mechanical strength is used. The range of the hole diameter of the separator is generally used for batteries. For example, 0.01 to 10 μm is used. The thickness of the separator is generally used in the range for batteries. For example, 5 to 300 μm is used.

  Gaskets include polyphenylene sulfide, polyethylene terephthalate, polyamide, liquid crystal polymer (LCP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin (PFA), polyether ether ketone resin (PEEK), polyether nitrile resin (PEN), polyether Ketone resin (PEK), polyamideimide, polyarylate resin, polybutylene terephthalate resin, polycyclohexanedimethylene terephthalate resin, polyethersulfone resin, polyaminobismaleimide resin, polyetherimide resin, fluororesin can be destroyed at the reflow temperature. Moreover, there was no problem of leakage due to deformation by the gasket even in storage after reflow.

  In particular, resins with a heat distortion temperature of 230 ° C or higher, polyphenylene sulfide, liquid crystal polymer (LCP), polyetheretherketone resin (PEEK), polyethernitrile resin (PEN), polyamideimide resin, or tetrafluoroethylene-perfluoroalkyl The vinyl ether copolymer resin was excellent in terms of leakage resistance. Moreover, what added glass fiber, my cow whisker, ceramic fine powder, ceramic whisker, etc. with the addition amount of about 40 weight% or less to this material can be used. In particular, those using potassium titanate whiskers were good.

As a method for manufacturing the gasket, there are an injection molding method, a thermal compression method, and the like.
The thermal compression method is a method of obtaining a final molded product by performing thermal compression molding at a temperature equal to or lower than the melting point using a plate material having a thickness larger than the gasket shape of the molded product as a material molded product.

  Generally, when a temperature is applied to a thermoplastic resin molded product molded by hot compression molding at a temperature below the melting point from the material molded product, there is a property of returning to the shape of the original material molded product. As a result, a gap is formed between the outer can and the inner can (metal) and the gasket (resin). Alternatively, by using this gasket for non-aqueous electrolyte secondary batteries that should not have sufficient stress for sealing between the can and the gasket, the outer can and can can be expanded due to expansion of the gasket due to heat treatment (reflow soldering, etc.). A gap cannot be formed between the (metal) and the gasket (resin), or a sufficient stress can be obtained for sealing between the can and the gasket.

  Further, it has a property of returning to the original shape of the molded material over time, and is effective in batteries other than reflow soldering.

In particular, in gaskets using tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin (PFA), the heat compression molding itself, which is produced by heating and pressurizing a sheet-like material, is better sealed. The property was good. This is because PFA has rubber elasticity and injection molded products shrink at the reflow temperature, whereas hot compression molded products try to return to the thickness of the sheet before molding at the reflow temperature. This is because the internal pressure of the portion increases, and further sealing confidentiality can be achieved.
On the other hand, the injection molding method is the most common molding method for gaskets. However, in the case of sacrificing molding accuracy due to cost reduction or the like, it is essential to use a liquid sealant to supplement confidentiality.

In the case of coins and button batteries, one or a mixture of liquid sealants such as asphalt pitch, butyl rubber, fluorinated oil, chlorosulfonated polyethylene, and epoxy resin is used between the gasket and the positive and negative electrode cans. When the liquid sealant is transparent, it is colored to clarify the presence or absence of application. Examples of the method for applying the sealant include injection of the sealant into the gasket, application to the positive / negative electrode can, and dipping of the gasket into the sealant solution.
When the battery shape is a coin or a button, the electrode shape is used by compressing a mixture of a positive electrode active material and a negative electrode active material into a pellet shape. In the case of a thin coin or button, an electrode molded into a sheet shape may be punched out. The thickness and diameter of the pellet are determined by the size of the battery.

As the pellet pressing method, a generally adopted method can be used, but a die pressing method is particularly preferable. The press pressure is not particularly limited, but is preferably 0.2 to 5 t / cm ² . The pressing temperature is preferably room temperature to 200 ° C.

  In addition to the binder, a conductive agent or a filler can be added to the electrode mixture. The kind of the conductive agent is not particularly limited and may be a metal powder, but a carbon-based one is particularly preferable. Carbon materials are the most common, and natural graphite (scale-like graphite, scale-like graphite, earth-like graphite, etc.), artificial graphite, carbon black, channel black, thermal black, furnace black, acetylene black, carbon fiber, etc. are used. As the metal, metal powder such as copper, nickel, silver, or metal fiber is used. Conductive polymers are also used.

  The amount of carbon added varies depending on the electrical conductivity of the active material, the electrode shape, and the like, and is not particularly limited. However, in the case of the negative electrode, 1 to 50% by weight is preferable, and 2 to 40% by weight is particularly preferable.

  When the carbon particle size is in the range of 0.5 to 50 μm, preferably 0.5 to 15 μm, more preferably 0.5 to 6 μm in terms of average particle size, the contact between the active materials is improved, and the network of electron conduction is formed. The active material that does not participate in the electrochemical reaction is reduced.

  Any filler can be used as long as it is a fibrous material that does not cause a chemical change in the constructed battery. In the present invention, fibers such as carbon and glass are used. Although the addition amount of a filler is not specifically limited, 0-30 weight% is preferable.

  It is desirable to use a metal plate having a low electric resistance as a can serving also as an electrode active material final collector. For example, in addition to stainless steel, nickel, aluminum, titanium, tungsten, gold, platinum, calcined carbon, etc. as materials for the positive electrode, the surface of aluminum or stainless steel treated with carbon, nickel, titanium, or silver is used. It is done. As for stainless steel, duplex stainless steel is effective against corrosion. In the case of a coin or button battery, nickel plating is performed on the outside of the battery. Treatment methods include wet plating, dry plating, CVD, PVD, clad formation by pressure bonding, coating, and the like.

  In addition to stainless steel, nickel, copper, titanium, aluminum, tungsten, gold, platinum, baked carbon, etc., the negative electrode can was treated with carbon, nickel, titanium, or silver on the surface of copper or stainless steel. Or Al-Cd alloy is used. Treatment methods include wet plating, dry plating, CVD, PVD, clad formation by pressure bonding, coating, and the like.

  It is also possible to fix the electrode active material and the current collector can with a conductive adhesive. As the conductive adhesive, a resin in which carbon or metal powder or fiber is added to a resin dissolved in a solvent, or a conductive polymer dissolved therein is used.

  In the case of a pellet-shaped electrode, it is applied between the current collector and the electrode pellet, and the electrode is fixed. The conductive adhesive in this case often includes a thermosetting resin.

  The application of the non-aqueous electrolyte secondary battery of the present invention is not particularly limited, but is optimal for a backup power source such as a mobile phone or a pager.

  The battery of the present invention is preferably assembled in a dehumidified atmosphere or an inert gas atmosphere. Moreover, it is preferable to dry the parts to be assembled in advance. As a method for drying or dehydrating pellets, sheets and other parts, it is preferable to use hot air, vacuum, infrared rays, far infrared rays, electron beams and low-humidity air alone or in combination. The temperature is preferably in the range of 80 to 350 ° C, particularly preferably in the range of 100 to 300 ° C. The water content is preferably 2000 ppm or less for the entire battery, and preferably 50 ppm or less for each of the positive electrode mixture, the negative electrode mixture and the electrolyte from the viewpoint of improving charge / discharge cycle performance.

  The present invention supports reflow soldering in coin-type (button-type) non-aqueous electrolyte secondary batteries that use lithium-ion conductive non-aqueous electrolytes with materials capable of occluding and releasing lithium as negative electrode and positive electrode active materials. The present invention relates to a heat-resistant nonaqueous electrolyte secondary battery.

It is sectional drawing which shows the Example of the electrolyte secondary battery of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Positive electrode case 3 Negative electrode 4 Negative electrode case 5 Lithium foil 6 Separator 7 Gasket 8 Electrolyte

Claims (5)

  A nonaqueous electrolyte secondary battery having an electrode comprising an electrode active material and a binder, wherein the binder is water-soluble polyacrylamide.   A non-aqueous electrolyte secondary battery having a positive electrode made of a positive electrode active material and a positive electrode binder, and a negative electrode made of a negative electrode active material and a negative electrode binder, the positive electrode binder and the negative electrode binder. A non-aqueous electrolyte secondary battery, wherein at least one of the adhering agents is water-soluble polyacrylamide.   The nonaqueous electrolyte secondary battery according to claim 1 or 2, wherein the water-soluble polyacrylamide has a bulk specific gravity of 0.5 to 0.7 and a molecular weight of 10 million to 18 million.   The non-aqueous electrolyte secondary battery according to claim 2, wherein the positive electrode active material includes any one of Mn oxide, Mo oxide, Ti oxide, and niobium pentoxide.   The non-aqueous electrolyte secondary battery according to claim 2, wherein the negative electrode active material is SiO.

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