JP2010153167A - Flat type nonaqueous electrolyte battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flat type nonaqueous electrolyte battery suppressing deterioration of battery characteristics caused by moisture infiltrating from the outside under humid environments by improving its sealing performance, and having excellent reliability for a long period of time. <P>SOLUTION: In this flat type nonaqueous electrolyte battery, a generating element constituted of a positive electrode and a negative electrode disposed face to face through a separator is housed in a battery case together with a nonaqueous electrolyte, the opening part of the battery case is sealed by a sealing part through a gasket, and a resin material made up by tetra-fluoroethylen-perfluoroalkyl vinyl ether copolymer having crystallinity of 25-45% is used for the gasket. Thereby, air tightness is improved to suppress infiltration of moisture from the outside, and the battery has high reliability without causing deterioration of air tightness due to surface peeling of the gasket 6. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an improvement in long-term reliability of a flat type non-aqueous electrolyte battery, and more particularly to a flat type non-aqueous electrolyte battery excellent in battery reliability in humid storage.

  In recent years, cordless and portable personal information terminals such as mobile phones and PDAs have rapidly become more and more demanded for non-aqueous electrolyte batteries having high energy density as demand for further downsizing and weight reduction increases. . Under such circumstances, the market of flat type (button type, coin type, flat rectangular type) non-aqueous electrolyte batteries is widened in terms of size, mountability, cost, etc., and its applications are diverse.

  Conventionally, as a gasket material for a flat type non-aqueous electrolyte battery, a general-purpose resin such as inexpensive polypropylene (PP) that is excellent in chemical resistance, elasticity, creep resistance, good moldability, and easy to produce by injection molding is used. Widely used.

  On the other hand, flat non-aqueous electrolyte batteries used for memory backup power supplies often require automatic mounting on a circuit board by reflow soldering, so high-temperature gasket materials are required, and polyphenylene sulfide ( Heat-resistant engineering plastics such as PPS) and fluorine-based resins are used.

In addition, flat type nonaqueous electrolyte batteries used for main power supply of equipment are required to have high reliability over a long period of time. In actual use, they may be used not only in high-temperature environments but also in humid environments. It is also important to take measures against humidity. However, unlike the aqueous battery, the flat type non-aqueous electrolyte battery has a very weak surface against moisture, and has a problem that the battery characteristics are deteriorated at an early stage due to moisture intrusion from the outside. For this reason, fluorine resin such as tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) or tetrafluoroethylene-ethylene copolymer (ETFE) with low moisture permeability is used as the gasket material, so that moisture can enter from the outside. A method for preventing this problem has been studied (for example, Patent Document 1). In particular, PFA resins have been attracting attention because of their high fluorine content and very low moisture permeability.
JP 2006-147159 A

  However, when this PFA resin is used as a gasket material for a flat type non-aqueous electrolyte battery, the sealing part of the flat type non-aqueous electrolyte battery is a caulking seal. In addition, there is a problem that moisture permeates through the gap between the sealing plate or gasket and the battery case, and the reliability of the battery cannot be secured. This is considered to be because the atomic force between the fluorine atoms constituting the molecule of the fluororesin is weak, so that the molecules are separated from each other with a slight pressure, and peel off as a surface layer. .

  In this way, in flat type non-aqueous electrolyte batteries using PFA resin as a gasket material, maintaining high reliability for storage in a humid environment and preventing deterioration of confidentiality due to surface peeling of the gasket Is a very important issue in increasing the demand of this type of battery as a practical battery.

An object of the present invention is to solve these problems and provide a flat non-aqueous electrolyte battery having high reliability.

  In order to solve the above problems, the flat type nonaqueous electrolyte battery of the present invention accommodates a power generation element composed of a positive electrode, a negative electrode, and a nonaqueous electrolyte solution disposed in a battery case so as to face each other through a separator, In a flat type nonaqueous electrolyte battery hermetically sealed with a gasket and a battery case, the gasket is composed of a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer having a crystallinity of 25% to 45%. It is characterized by this.

  According to the present invention, there is provided a flat non-aqueous electrolyte battery having high reliability by improving the confidentiality of the flat non-aqueous electrolyte battery, greatly suppressing deterioration of battery characteristics due to moisture ingress from the outside in a humid environment. it can.

  The flat type nonaqueous electrolyte battery of the present invention accommodates a power generation element composed of a positive electrode, a negative electrode, and a nonaqueous electrolyte disposed opposite to each other with a separator in a battery case, and is sealed with a sealing plate, a gasket, and a battery case. In the flat type nonaqueous electrolyte battery, the gasket is made of a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer having a crystallinity of 25% to 45%.

  As a result of various studies, the use of PFA resin having a crystallinity of 25% or more and 45% or less greatly suppresses moisture ingress in a humid environment without causing a decrease in confidentiality due to surface peeling during sealing. It has been found that a flat non-aqueous electrolyte battery with high reliability can be provided.

  By increasing the crystallinity to 25% or more, gaps between molecular chains can be eliminated, and the amount of water that permeates through the resin can be greatly suppressed. Further increasing the crystallinity is effective in reducing moisture permeability, but when the crystallinity is increased to 45% or higher, the molecular chains are regularly arranged in parallel to each other, and the intermolecular force is increased by fluorine atoms. This is because the ratio depending on the interatomic force increases, causing surface peeling at the time of sealing.

  Hereinafter, an example of a flat type nonaqueous electrolyte battery according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a cross-sectional view of a flat type nonaqueous electrolyte battery of the present invention. A battery case 4 that also serves as a positive electrode terminal via a current collector 7, a sealing plate 5 that also serves as a negative electrode terminal, and a battery case 4 and a sealing plate 5 that are made of a positive electrode 1 and a negative electrode 2, a separator 3, and a non-aqueous electrolyte. In the flat type non-aqueous electrolyte battery housed and sealed by the gasket 6 that insulates, the gasket 6 is made of a PFA resin having a crystallinity of 25% or more and 45% or less.

  The positive electrode 1 is an electrode molded into a pellet shape, and the positive electrode active material is not particularly limited, and examples thereof include a lithium-containing transition metal oxide that can accept lithium ions. Specifically, for example, a 3V class active material such as manganese dioxide, vanadium pentoxide, molybdenum trioxide, lithium manganese composite oxide, or lithium cobaltate, lithium nickelate, spinel type lithium manganate containing lithium 4V class active material, such as these. It is also preferable that magnesium or aluminum is added to these oxides. However, only when manganese dioxide, vanadium pentoxide, molybdenum trioxide, lithium manganese composite oxide, etc. that do not contain reversible lithium are used for the positive electrode, lithium is chemically or electrochemically used for the negative electrode 2 when the battery is constructed. Need to be inserted into.

The negative electrode 2 is also an electrode formed into a pellet shape, and the negative electrode active material is not particularly limited, and examples thereof include a material capable of electrochemically inserting and extracting lithium ions and metallic lithium. Examples of substances capable of electrochemically inserting and extracting lithium ions include metal oxides such as Li ₄ Ti ₅ O ₁₂ , SiO, SnO, Nb ₂ O ₅ , and WO ₂ , and carbon such as graphite and coke. Examples of the material include lithium alloys such as lithium-aluminum alloy, lithium-lead alloy, and lithium-tin alloy.

  For the separator 3, it is preferable to use conventionally used polyethylene, polypropylene, engineering plastics such as cellulose and polyphenylene sulfide.

Solutes constituting the non-aqueous electrolyte include simple substances such as LiPF ₆ , LiBF ₄ , LiClO ₄ , LiCF ₃ SO ₃ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , and LiN (C ₂ F ₅ SO ₂ ) _2. Alternatively, a plurality of components can be mixed and used. In addition, as a solvent constituting the nonaqueous electrolytic solution, propylene carbonate, ethylene carbonate, butylene carbonate, vinylene carbonate, dimethyl carbonate, diethyl carbonate, sulfolane, dimethoxyethane, diethoxyethane, tetrahydrofuran, dioxolane, γ-butyrolactone, or the like Multiple components can be used, but are not limited thereto.

  The current collector 7 is obtained by applying a conductive carbon paint to the inner surfaces of the battery case 4 and the sealing plate 5.

Hereinafter, embodiments of the present invention will be described more specifically with reference to the drawings and tables.
Example 1
The positive electrode 1 is obtained by mixing LiCoO ₂ with carbon black as a conductive agent and fluororesin powder as a binder in a mass ratio of 90: 5: 5, and forming into a pellet shape having a diameter of 10 mm and a thickness of 0.5 mm. What was dried at 200 ° C. for 24 hours was used.

After the negative electrode 2 was mixed with lithium titanate (Li ₄ Ti ₅ O ₁₂ ) in a mass ratio of 93: 5: 2, carbon black and fluororesin powder were molded into a pellet having a diameter of 10 mm and a thickness of 0.5 mm. What was heat-treated at 120 ° C. for 24 hours was used.

  The separator 3 is made of polypropylene nonwoven fabric, and the battery case 4 and the sealing plate 5 are made of stainless steel.

  A PFA resin having a crystallinity of 30.5% is used for the gasket 6, and a toluene solvent in which butyl rubber is dissolved as a sealant material is applied to the surface of the gasket 6. 1 was used for drying for 1 hour and removing the solvent to form a sealant layer on the surface of the gasket 6.

The current collector 7 was obtained by applying a conductive carbon paint to the inner surfaces of the battery case 4 and the sealing plate 5 and then drying the battery case at 150 ° C. for 6 hours in order to remove moisture from the coating film. The non-aqueous electrolyte was prepared using a solvent in which ethylene carbonate and methyl ethyl carbonate were mixed at a volume ratio of 1: 3, and LiPF ₆ was dissolved as a solute at a ratio of 1 mol / l. A flat nonaqueous electrolyte battery having the structure shown in FIG. 1 was designated as battery A1.

  Moreover, flat type nonaqueous electrolyte batteries produced in the same manner as the battery A1 except that the crystallinity of the gasket material was changed as shown in Table 1 were designated as batteries A2 to A3 and B1 to B4. All of these batteries have a diameter of 16 mm and a thickness of 1.6 mm.

  About these flat type non-aqueous electrolyte batteries, after assembling, charging was performed at a constant voltage of 2.6 V for 24 hours (protection resistance 50Ω). Further, the discharge capacity of these batteries after storage for 30 days in a high temperature and high humidity environment of 70 ° C. and 90% was confirmed. The discharge capacity was a constant resistance discharge of 2 kΩ up to 2.0 V, and the capacity at this time was calculated. These results are shown in (Table 1).

  The crystallinity was measured by an X-ray diffraction method using an X-resolution diffractometer (Spectris). The peak observed by X-ray diffraction was separated into a peak area (Ic) due to the crystalline component and a peak area (Ia) due to the amorphous component, and expressed as crystallinity (%) = 100 × Ic / (Ic + Ia). Is.

  As can be seen from the results of (Table 1), the batteries A1 to A3 using the PFA resin having a crystallinity of 25% or more and 45% or less have a sufficient discharge capacity. On the other hand, the batteries B1 and B2 having a crystallinity of less than 25% and the batteries B3 and B4 having a crystallinity of more than 45% showed a large deterioration in discharge capacity. After the test, these B1 to B4 batteries were confirmed to generate hydrogen gas from the inside of the battery, which seems to be due to intrusion moisture, and this was assumed to be the cause of the deterioration of the discharge capacity. As a result of further disassembling investigation, peeling of the gasket surface was observed in the B3 and B4 batteries, which resulted in a decrease in confidentiality, which was considered to cause moisture intrusion into the battery.

  From these results, the batteries A1 to A3 have a surface detachment of the gasket while suppressing moisture intrusion due to high crystallinity for long-term storage in a severe environment of high temperature and high humidity compared to the batteries B1 to B4. It can be seen that high reliability can be realized without degrading the confidentiality due to.

  The flat non-aqueous electrolyte battery of the present invention is useful as a main power source or backup power source for electronic devices and the like.

Sectional drawing of the flat type nonaqueous electrolyte battery in one embodiment of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Separator 4 Battery case 5 Sealing plate 6 Gasket 7 Current collector

Claims (1)

In a flat nonaqueous electrolyte battery in which a power generation element composed of a positive electrode, a negative electrode, and a nonaqueous electrolyte solution, which are arranged to face each other via a separator, is housed in a battery case, and is sealed with a sealing plate, a gasket, and a battery case, the gasket A flat non-aqueous electrolyte battery comprising a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer having a crystallinity of 25% to 45%.

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