JP2012195129A - Coin-shaped battery and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coin-shaped battery capable of enhancing adhesiveness among an active material, carbon and a binder by containing a small amount of a surface active agent added thereto, and thereby can improve high-load current characteristics, and to provide a method for manufacturing the same.SOLUTION: The method for manufacturing the coin-shaped battery comprises the steps of: kneading the fine-powdered active material and a nonionic surface active agent; adding a conductive agent, the binder and a solvent to the kneaded mixture and kneading them; drying and fracturing the mixture and pressure-molding the fractured substance to form pellet-shaped electrodes 1 and 2; drying the electrodes; and placing the electrodes that are arranged so as to face each other through a separator 3 in an outer package body together with an electrolyte.

Description

  The present invention relates to a coin-type battery used as a power source for various electronic devices and a method for manufacturing the same.

  In recent years, lithium batteries and lithium secondary batteries, which are batteries using a non-aqueous electrolyte, have been used as power sources for many electronic devices as batteries with high output and high energy density. Batteries using these non-aqueous electrolytes have a higher discharge voltage and superior low-temperature characteristics and long-term storage characteristics as compared with batteries in which the electrolyte is an aqueous solution, and batteries having various shapes have been put into practical use. In particular, a coin-shaped battery having a coin shape is small and lightweight.

  Coin-type batteries include primary batteries and secondary batteries. The primary batteries are mainly used in many electronic devices as lithium manganese dioxide batteries with a positive electrode made of manganese oxide and a negative electrode made of lithium metal. In recent years, it has begun to be used for in-vehicle applications that are used at high temperatures, and its fields are expanding.

  On the other hand, in the secondary battery, a lithium manganese secondary battery mainly using lithium manganate for the positive electrode and a lithium aluminum alloy for the negative electrode is used as a memory backup power source for small electronic devices. However, when a lithium aluminum alloy is used for the negative electrode, if a charge / discharge cycle that discharges to a depth of 100% of the discharge capacity is performed, the surface of the negative electrode becomes brittle and the conductivity cannot be obtained. It is not suitable for main power supply.

  Therefore, for main power supplies that require charge / discharge cycles of 100 cycles or more, lithium manganate, lithium cobaltate, lithium nickelate, etc. are used for the positive electrode, and lithium titanate, silicon oxide, graphite, etc. are used for the negative electrode. Many secondary batteries have been developed. In these secondary batteries, lithium is easily inserted and removed between the layers of the negative electrode active material structure, so that the discharge capacity is 100 cycles or more even when the charge / discharge cycle is discharged to a depth of 100% of the discharge capacity. .

  In addition, main load applications often require high load current such as radio wave transmission of equipment. One method of increasing the surface area per unit mass of the active material or conductive agent in order to improve the high load current characteristics is to reduce the particle size of the material. In the case of this method, the smaller the particle size of the active material, the lighter the mass per single particle, the greater the influence of charging between the active material particles due to intermolecular forces or static electricity, and aggregation between the active materials, It is not easy to obtain the effect of increasing the surface area by reducing the particle size.

  As a method of improving aggregation / dispersion, a method of mixing and kneading using a surfactant has been proposed (for example, see Patent Document 1). However, when a surfactant is used, if the heat treatment is performed at a high temperature of 200 ° C. or higher in an atmospheric pressure (atmospheric pressure) atmosphere, oxygen of the manganese dioxide that is the positive electrode active material is deprived by the surfactant (oxygen deficiency), and the discharge performance. The effective manganese dioxide is reduced and the discharge performance is greatly affected. Therefore, it is proposed that its use is preferably 0.1% to 1.0% by weight.

JP 2005-310522 A

  As described above, in the conventional mixing / kneading method, the smaller the active material particle size, the greater the influence of charging between the active material particles due to intermolecular force or static electricity, and the active material aggregates. In order to suppress the agglomeration and improve the dispersibility, it was necessary to add a large amount of surfactant.

  The present invention provides a coin-type battery and a method for producing the same that can improve the high load current characteristics by improving the adhesion between the active material, carbon, and the binder at least as much as in the past with the addition amount of the surfactant less than the conventional one. It is intended to provide.

  In order to achieve the above-mentioned object, the present invention kneaded after adding a conductive agent, a binder and a solvent to a pre-kneaded active material and a nonionic surfactant in advance, pulverized after drying This is a coin-type battery in which one is formed by pressure molding to form one pellet-shaped electrode, this electrode is dried, placed opposite to the other electrode via a separator, and enclosed in an outer package together with an electrolytic solution .

  In addition, the present invention is a method in which a finely powdered active material and a nonionic surfactant are kneaded in advance, further kneaded by adding a conductive agent, a binder and a solvent, dried, and then pulverized. This is a method for producing a coin-type battery in which one pellet-shaped electrode is formed, this electrode is dried, placed opposite to the other electrode through a separator, and enclosed in an outer package together with an electrolytic solution.

  ADVANTAGE OF THE INVENTION According to this invention, the coin-type battery which the adhesiveness of a fine powdery active material, a electrically conductive agent, and a binder improves, and a high load current characteristic improves can be provided.

Sectional drawing of the coin-type battery which concerns on one embodiment of this invention

  According to the first aspect of the present invention, a finely powdered active material and a nonionic surfactant are kneaded in advance, further kneaded by adding a conductive agent, a binder and a solvent, dried, and then pulverized. This is a coin-type battery in which one electrode in the form of pellets is formed by pressure molding, this electrode is dried, placed opposite to the other electrode through a separator, and enclosed in an outer package together with an electrolytic solution.

  In other words, by kneading the finely powdered active material and the nonionic surfactant in advance, the nonionic surfactant enters between the finely powdered active material to suppress aggregation and further kneading while incorporating the conductive agent. In addition, an electrode with improved adhesion between a fine powdery active material, a conductive agent and a binder can be formed, and a coin-type battery with improved high load current characteristics can be provided.

  A second invention according to the present invention is the coin-type battery according to the first invention, wherein the nonionic surfactant is of a polyoxyethylene alkyl ether type.

  By using polyoxyethylene alkyl ether, the adhesion between fine powdery active material, conductive agent and binder is further improved, and it is fully decomposed by high-temperature heat treatment at 200 ° C or higher, so the battery characteristics are not deteriorated and the load is high. A coin-type battery with improved current characteristics can be provided.

A third invention of the present invention is the coin-type battery according to the first invention, wherein the nonionic surfactant is added in an amount of 0.1% by mass to 0.4% by mass with respect to the solid content of the electrode.

  By setting the addition amount within this range, it is possible to provide a coin-type battery in which high load current characteristics are improved with a smaller amount than in the past.

  A fourth invention of the present invention is the coin-type battery according to the first invention, wherein the active material has an average particle size of 0.5 μm or more and 10 μm or less.

  By providing the average particle size of the active material within this range, the surface area of the active material is increased, and the number of contact portions between the active material, the conductive agent, and the binder is increased, so that a coin-type battery with improved high load current characteristics is provided. be able to.

  According to a fifth aspect of the present invention, a finely powdered active material and a nonionic surfactant are kneaded in advance, further kneaded by adding a conductive agent, a binder and a solvent, dried, and then pulverized. A coin-shaped battery manufacturing method in which one electrode in the form of pellets is formed by pressure molding, this electrode is dried, placed opposite to the other electrode through a separator, and enclosed in an outer package together with an electrolyte. is there.

  By kneading the fine powdered active material and the nonionic surfactant in advance, the nonionic surfactant enters the fine powdery active material to suppress aggregation, and further kneading while incorporating the conductive agent. An electrode with improved adhesion between a fine powdery active material, a conductive agent, and a binder can be formed, and a coin-type battery with improved high load current characteristics can be provided.

  A sixth invention of the present invention is a method for manufacturing a coin-type battery, wherein the drying temperature of the pellet-shaped electrode is 200 ° C. or higher and 300 ° C. or lower.

  By setting the drying temperature of the electrode within this range, the nonionic surfactant is thermally decomposed without becoming a resistance component on the surface of the active material, and a coin-type battery superior in high load current characteristics can be provided. .

  Hereinafter, an embodiment of the present invention will be described. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.

  FIG. 1 is a cross-sectional view of a coin battery of the present invention.

  In the coin-type battery using the non-aqueous electrolyte used in the present invention, the negative electrode 2 is installed inside the sealing plate 5 and the gasket 4 and then the separator 3 is inserted, and the non-aqueous electrolyte is inserted into the separator 3. After impregnating, the positive electrode 1 is installed, and after the positive electrode case 6 is fitted, it is fabricated by bending and sealing.

  The positive electrode 1 includes an active material, a surfactant, a conductive agent, and a binder. The manufacturing method kneads an active material and a surfactant, and then kneads a conductive agent and a binder. In this kneading, ion exchange water may be appropriately added to such an extent that it does not become a slurry. Then, after drying the kneaded material, it is weighed and pressure-molded to form a pellet, and after the pellet is formed, it is further dried to produce the positive electrode 1.

In this way, by kneading the fine powdered active material and the nonionic surfactant, the surfactant enters the fine powdery active material to suppress aggregation and further knead while incorporating the conductive agent. In addition, an electrode with improved adhesion between the fine powdery active material, the conductive agent and the binder can be formed, and a coin-type battery with improved high load current characteristics can be provided. When the active material and the conductive agent are kneaded first, the active material and the conductive agent are aggregated at the time when the surfactant is mixed. Therefore, if the surfactant is added later, the active material and the conductive agent are added. A large amount of surfactant is required to suppress both aggregations. However, when the active material and the surfactant are mixed first, aggregation is suppressed with a small amount of the surfactant, and the opportunity for the active material to adhere to the conductive agent increases. It is considered that good results can be obtained because of the combination.

The active material may be any metal oxide having a crystal structure capable of occluding and releasing lithium, or a metal oxide obtained by firing at 500 ° C. or higher, such as manganese dioxide, lithium cobaltate, manganese. Examples thereof include lithium acid lithium, lithium nickel acid, V ₂ O ₅ , and Nb ₂ O ₅ .

  Any surfactant can be used as long as it is a nonionic surfactant. In particular, the use of a polyoxyethylene alkyl ether system improves the adhesion between the active material, the conductive agent and the binder, and further heat treatment at 200 ° C. or higher. Therefore, it is possible to provide a coin-type battery with improved high load current characteristics without degrading battery characteristics.

  Further, the addition amount is most preferably 0.1% by mass or more and 0.4% by mass or less with respect to the electrode solid content. In manganese dioxide, oxygen vacancies in manganese dioxide occur as the amount added increases.

  The average particle size of the active material is most preferably 0.5 μm or more and 10 μm or less. The average particle diameter here indicates the median diameter. When the average particle size is smaller than 0.1 μm, the active materials are strongly aggregated, so that the adhesiveness with the conductive agent and the binder is insufficient and the high-load discharge characteristics are deteriorated. On the other hand, when it is larger than 20 μm, the cohesiveness is weak and the high load discharge characteristics are the same level as when no nonionic surfactant is added, and the effect is small.

  As for the drying temperature of an electrode, 200 to 300 degreeC is more preferable. In this temperature range, the nonionic surfactant can be thermally decomposed, and the reactivity can be maintained without becoming a resistance component on the surface of the active material, so that the high load current characteristics are excellent. If it is less than 200 ° C., the surfactant remains on the surface of the active material without being decomposed and becomes a resistance component, so that the high load current characteristic is deteriorated. When the temperature is higher than 300 ° C., the binder is decomposed, so that the adhesion between the active material and the conductive agent is lowered, and the high load current characteristics are lowered.

  Carbon is mainly used as the conductive agent, and examples thereof include chain-structured acetylene black and carbon black.

  Examples of the binder include fluorine-based, rubber-based, and acrylic acid-based binders. In particular, a fluorine type having excellent heat resistance is preferable.

  Examples of the negative electrode 2 include lithium metal in a metal system, lithium aluminum alloy in an alloy system, and an alloy obtained by adding metal to silicon oxide.

  Further, any metal oxide having a layered structure or a crystal structure capable of occluding and releasing lithium can be used. In particular, graphite, lithium titanate, silicon oxide and the like which are suitable for lithium intercalation can be mentioned.

  Carbon is mainly used as the conductive agent, and examples thereof include chain-structured acetylene black and carbon black.

Examples of the binder include fluorine-based, rubber-based, and acrylic acid-based binders. In particular, a fluorine type having excellent heat resistance is preferable.

  When a metal oxide having a layered structure or a crystal structure capable of inserting and extracting lithium is used as the active material, the electrode can be manufactured by the same manufacturing method as that for the positive electrode 1.

  The separator 3 may be any material as long as it insulates the negative electrode 2 and the positive electrode 1, and examples thereof include polypropylene, polyethylene, and polyphenylene sulfide (PPS).

  The gasket 4 is made of a fluorine-containing polymer material such as tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA) or polytetrafluoroethylene (PTFE) having a high melting point and excellent heat resistance.

  The sealing plate 5 may be anything as long as it is stainless steel, and when an alloy of lithium and aluminum is used for the negative electrode 2, stainless steel having a structure in which aluminum is disposed on the inner surface may be used.

  The positive electrode case 6 is made of stainless steel, aluminum steel, or the like.

The nonaqueous electrolytic solution may be any one as long as an electrolyte is dissolved in a nonaqueous solvent solution. Examples of the non-aqueous solvent liquid include propylene carbonate, ethylene carbonate, butylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, dimethoxyethane, and gamma butyl lactone. Examples of the electrolyte include LiPF ₆ , LiBF ₄ , LiNCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiClO _{4 and the} like.

  Hereinafter, the present invention will be specifically described based on examples.

(Production of battery A)
The positive electrode 1 includes 90% by mass of fine powder lithium cobaltate LiCoO ₂ having an average particle size of 10 μm as a positive electrode active material, 0.1% by mass of polyoxyethylene alkyl ether as a surfactant, and a conductive agent. It is composed of 5% by mass of powdered carbon black and 5% by mass of polytetrafluoroethylene dispersed in ion-exchanged water as a binder.

  In the production method, fine powdery lithium cobaltate and polyoxyethylene alkyl ether are kneaded while adding ion-exchanged water so as not to form a slurry. Polytetrafluoroethylene dispersed in carbon black and ion-exchanged water is added to the kneaded material and further kneaded. And after drying at 80 degreeC for 24 hours, it grind | pulverizes and it is set as a positive electrode mixture.

  30 mg of this positive electrode mixture was weighed and pressure-molded into a pellet shape having a diameter of 3.8 mm and a thickness of 0.90 mm, and then dried with hot air at 250 ° C. for 24 hours to prepare the positive electrode 1.

The negative electrode 2 _kneads 90% by mass of lithium titanate Li _4/3 Ti _5/3 O ₄ as a negative electrode active material, 5% by mass of carbon black, and 5% by mass of styrene butadiene rubber. And after drying at 80 degreeC for 24 hours, it was set as the negative mix. 24 mg of this negative electrode mixture was weighed and pressure-molded into a pellet having a diameter of 4.0 mm and a thickness of 0.85 mm, and then dried at 100 ° C. for 24 hours to prepare a negative electrode 2.

After this negative electrode 2 is installed inside a sealing plate 5 integrated with a gasket 4, a separator 3 made of polypropylene is inserted. The separator 3 is impregnated with a non-aqueous electrolyte solution in which LiPF ₆ is dissolved at a concentration of 1 mol / l in a solvent in which ethylene carbonate and ethyl methyl carbonate are mixed at a ratio of 1: 3. Thereafter, the positive electrode 1 was installed, the positive electrode case 6 was fitted and sealed, and a battery A having a diameter of 6.8 mm and a thickness of 2.1 mm was produced.

(Production of battery B)
Battery B was produced in the same manner as Battery A, except that 0.05% by mass of the nonionic surfactant was added per electrode solid content.

(Production of Battery C)
A battery C was produced in the same manner as the battery A, except that 0.2% by mass of the nonionic surfactant was added based on the solid content of the electrode.

(Production of battery D)
A battery D was produced in the same manner as the battery A, except that 0.4% by mass of the nonionic surfactant was added per electrode solid content.

(Production of battery E)
Battery E was produced in the same manner as Battery A, except that 1.0% by mass of the nonionic surfactant was added per electrode solid content.

(Production of battery G)
In the production method, 90% by mass of finely powdered lithium cobaltate and 5% by mass of carbon black are mixed, and then ion-exchanged water is added so that 0.1% by mass of polyoxyethylene alkyl ether does not become a slurry. Knead while adding. To the kneaded product, polytetrafluoroethylene dispersed in ion-exchanged water is added and further kneaded. And after drying at 80 degreeC for 24 hours, it grind | pulverized and the battery G was produced like the battery A except having set it as the positive mix.

(Production of Battery F)
A battery F was produced in the same manner as the battery G, except that 0.05% by mass of the nonionic surfactant per electrode solid content was added.

(Production of battery H)
Battery H was produced in the same manner as Battery G, except that 0.2% by mass of the nonionic surfactant was added per electrode solid content.

(Production of Battery I)
Battery I was made in the same manner as Battery G, except that 0.4% by mass of the nonionic surfactant was added per electrode solid content.

(Production of Battery J)
Battery J was produced in the same manner as Battery G, except that 1.0% by mass of the nonionic surfactant was added per electrode solid content.

  Ten batteries A to J manufactured as described above were prepared and charged at 2.6 V, and then the battery voltage after 5 seconds was confirmed at −10 ° C. with a discharge current of 5 mA.

  The results are shown in (Table 1).

  In the batteries A to E in which the surfactant is mixed first, the same discharge test results are higher in voltage than the batteries F to J in which the surfactant is mixed later. This is because when the active material and the conductive agent are kneaded first, the active material and the conductive agent are aggregated at the time when the surfactant is mixed, so that not only the active material but also the conductive agent is aggregated. This is considered to be because the surface active agent has been used to suppress the phenomenon, and the opportunity for the active material to adhere to the conductive agent has decreased.

  In batteries A, C, and D, a high load current characteristic of 1.65 V or more was obtained. In the batteries B and E to which 0.05% by mass and 1.0% by mass of the nonionic surfactant were added, the high load current characteristics were lower than 1.55V.

  In the batteries A, C, and D in which the addition of the nonionic surfactant is 0.1% by mass or more and 0.4% by mass or less, the fine powdery active material and the nonionic surfactant are kneaded first, A surfactant enters between the powdery active materials to suppress aggregation of the active materials. Thereafter, kneading while incorporating the conductive agent, an electrode having improved adhesion between the fine powdered active material, the conductive agent, and the binder was formed, and the high load current characteristics were improved.

  In the battery E in which the addition of the nonionic surfactant is 1.0% by mass, the amount of the surfactant is large, so that not only the aggregation of the active material but also the aggregation of the conductive agent is suppressed. It is considered that the high load current characteristics deteriorated due to the large expansion after pressure forming into pellets and drying with hot air, although the surfaces increased because of the increased surface.

  Subsequently, the average particle size of the active material was examined.

(Production of battery K)
A battery K was produced in the same manner as the battery D except that an active material having an average particle diameter of 0.1 μm was used.

(Production of battery L)
A battery L was produced in the same manner as the battery D, except that an active material having an average particle diameter of 0.5 μm was used.

(Production of battery M)
A battery M was produced in the same manner as the battery D, except that an active material having an average particle diameter of 5.0 μm was used.

(Production of battery N)
A battery N was produced in the same manner as the battery D, except that an active material having an average particle diameter of 10 μm was used.

(Production of battery O)
A battery O was produced in the same manner as the battery D, except that an active material having an average particle diameter of 20 μm was used.

  The results are shown in (Table 2).

  In the batteries L, M, and N, a high load current characteristic of 1.65 V or more was obtained. In the battery K in which the average particle diameter of the active material is 0.1 μm and in the battery O in which the average particle diameter of the active material is 20 μm, it is lower than 1.6V.

  When the average particle size of the active material was 0.5 μm or more and 10 μm or less, aggregation of the active materials was suppressed, and the surface area of the active material was increased, and thus high load current characteristics were high.

  In the battery K in which the average particle diameter of the active material is 0.1 μm, it is considered that the high load current characteristics are deteriorated because the particles of the active material are small and the aggregation is too strong.

  In the battery O in which the average particle diameter of the active material is 20 μm, it is considered that the high load current characteristics are deteriorated because the active material particles are large.

  Subsequently, the drying temperature of the pellet-shaped electrode was examined.

(Production of battery P)
A battery P was produced in the same manner as the battery D, except that the drying temperature of the pellet-shaped electrode was 150 ° C.

(Production of battery Q)
A battery Q was produced in the same manner as the battery D except that the drying temperature of the pellet-shaped electrode was 200 ° C.

(Production of battery R)
A battery R was produced in the same manner as the battery D, except that the drying temperature of the pellet-shaped electrode was 300 ° C.

(Production of battery S)
A battery S was produced in the same manner as the battery D, except that the drying temperature of the pellet-shaped electrode was 400 ° C.

  The results are shown in (Table 3).

  In the batteries Q and R, a high load current characteristic of 1.65 V or more was obtained. In the battery P performed at an electrode drying temperature of 150 ° C. and the battery S performed at 400 ° C., the high load current characteristics were lower than 1.6V.

  When the drying temperature of the electrode was 200 ° C. or higher and 300 ° C. or lower, the nonionic surfactant in the electrode was decomposed and did not become a resistance component on the active material surface, and high load current characteristics were high.

  In the battery P having a drying temperature of 150 ° C., the nonionic surfactant is not sufficiently decomposed, so that it becomes a resistance component on the surface of the active material, and it is considered that the high load current characteristics are deteriorated.

  In the battery S having a drying temperature of 400 ° C., the binder is decomposed, so that the adhesion between the active material and the conductive agent is lowered, and the high load current characteristic is considered to be lowered.

  From the above results, a fine powdery active material and a nonionic surfactant are kneaded, and a conductive agent, a binder, and a solvent are added thereto, kneaded, dried, pulverized, and then pressure-molded into pellets After forming the upper electrode and drying this electrode, the other electrode and the separator placed opposite to each other through the separator are sealed in the outer package together with the electrolyte, thereby improving conductivity and excellent high load current characteristics. Batteries can be provided.

  ADVANTAGE OF THE INVENTION According to this invention, the adhesiveness of an active material, a electrically conductive agent, and a binder improves, the coin-type battery excellent in the high load current characteristic can be provided, and it is useful as a power supply etc. of various electronic devices.

1 Positive electrode 2 Negative electrode 3 Separator 4 Gasket 5 Sealing plate 6 Positive electrode case

Claims (6)

In addition, a powdered active material and a nonionic surfactant are kneaded in advance, a conductive agent, a binder and a solvent are further added, kneaded, dried and then pulverized, and then one of the pellets is pressure-molded. After forming this electrode, and drying this electrode, it arrange | positions facing through the other electrode and a separator, and is coin-type battery enclosed with the exterior body with electrolyte solution. The coin-type battery according to claim 1, wherein the nonionic surfactant is of a polyoxyethylene alkyl ether type. The coin-type battery according to claim 1, wherein the nonionic surfactant is added in an amount of 0.1% by mass to 0.4% by mass with respect to the electrode solid content. The coin-type battery according to claim 1, wherein the active material has an average particle size of 0.5 μm to 10 μm. In addition, a powdered active material and a nonionic surfactant are kneaded in advance, a conductive agent, a binder and a solvent are further added, kneaded, dried and then pulverized, and then one of the pellets is pressure-molded. A method for manufacturing a coin-type battery in which an electrode is formed, dried, and placed opposite to the other electrode with a separator interposed between the electrode and an electrolyte. The method for producing a coin-type battery according to claim 5, wherein a drying temperature of the pellet-shaped electrode is 200 ° C or higher and 300 ° C or lower.