JP2015141821A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress firing of a nonaqueous electrolyte secondary battery in an emergency.SOLUTION: A plate group is housed in a battery can together with an electrolyte, and a terminal and a cleavage type safety valve are provided on the cover plate of the battery can, in a nonaqueous electrolyte secondary battery. The safety valve is constituted of an exhaust passage leading from the inside to the outside of a battery, and a metal thin film cleaving with a predetermined internal pressure of the battery. The exhaust passage has an inner diameter tapered to spread from the battery inside open end toward the battery outside open end, and a metal foil film covers the battery inside open end of the exhaust passage. The exhaust passage is composed of a cylinder penetrating the cover plate, for example, and the battery outside open end of the exhaust passage is projecting from the cover plate surface. Preferably, the battery outside open end of the exhaust passage is projecting higher than the upper end of the terminal.

Description

  The present invention relates to a non-aqueous electrolyte secondary battery, and more particularly to a non-aqueous electrolyte secondary battery provided with a cleaving-type safety valve that cleaves a metal thin film at a predetermined battery internal pressure.

  Non-aqueous electrolyte secondary batteries such as lithium ion batteries are subject to severe conditions such as overcharge / overdischarge, excessive current flow, physical shock, external short circuit, and abnormally high temperatures. When placed underneath, the electrochemical reaction in the battery may run away, and in extreme cases, the internal pressure of the battery will increase, resulting in a very high temperature that may ignite or rupture. For this reason, the non-aqueous electrolyte secondary battery needs to be provided with an internal pressure release mechanism in case the battery internal pressure increases.

  Patent Document 1 discloses a non-aqueous electrolyte secondary battery in which an electrode plate group is housed in a battery can together with an electrolyte, and a terminal and a cleavage-type safety valve are provided on a cover plate of the battery can. The cleavable safety valve includes an exhaust passage that communicates from the inside of the battery to the outside of the battery, and a metal thin film that is cleaved at a predetermined battery internal pressure. The exhaust passage is configured by directly providing a through hole having a uniform inner diameter from the battery inner open end to the battery outer open end. Further, the metal foil film is formed by forming at least one horseshoe-like thin groove in a disc-shaped thin film made of SUS304, and covers and closes the open end of the exhaust passage inside the battery.

Japanese Patent No. 3637806

  Even when the technique disclosed in Patent Document 1 is used, when the internal pressure of the battery rises at the time of abnormality, the metal thin film is cleaved at the thin groove, and the generated flammable gas is discharged to the outside of the battery at an early stage. Can rupture. However, since the flammable gas is released from the exhaust passage at a high speed, the flammable gas may be ignited by frictional heat with the wall surface of the exhaust passage.

  An object of the present invention is to provide a nonaqueous electrolyte secondary battery that further reduces the risk of ignition of flammable gas to be released and further enhances safety.

  The non-aqueous electrolyte secondary battery which is the subject of the present invention stores the electrode plate group together with the electrolyte in a battery can, and is provided with a terminal and a cleavage-type safety valve on the cover plate of the battery can. The safety valve includes an exhaust passage that communicates from the inside of the battery to the outside of the battery, and a metal thin film that is cleaved at a predetermined battery internal pressure. The exhaust passage has an inner diameter that tapers from the battery inner open end toward the battery outer open end, and the metal foil film covers the battery inner open end of the exhaust passage. With the exhaust passage having such a shape, the release rate of the flammable gas released from the exhaust passage is moderated from the open end of the battery toward the open end of the battery, and the flammable gas is rubbed against the wall of the exhaust passage. It is possible to suppress ignition by heat.

  The exhaust passage can be provided directly in the lid plate. However, preferably, the exhaust passage is configured by a cylindrical body penetrating the lid plate, and the battery outside open end of the exhaust passage projects from the lid plate surface. When the exhaust passage is constituted by the cylindrical body, more preferably, the battery outside open end of the exhaust passage protrudes higher than the upper end of the terminal. If the battery outside open end of the exhaust passage protrudes from the cover plate surface, it is possible to suppress the released flammable gas from adhering to the cover plate surface and the terminal and causing a short circuit and a ground fault.

  As described above, according to the present invention, when an abnormality occurs in the battery, the internal pressure of the battery increases, and the flammable gas is released, the ignition of the flammable gas can be suppressed.

It is sectional drawing which cut | disconnected the cylindrical lithium ion battery to which this invention is applied along the longitudinal direction. It is a perspective view which shows the state which winds an electrode group. In embodiment of this invention, it is sectional drawing of the positive electrode side cover board which provided the cleavage type safety valve. In other embodiment of this invention, it is sectional drawing of the positive electrode side cover board which provided the cleavage type safety valve. FIG. 6 is a partially cutaway cross-sectional view of a cylindrical lithium ion battery showing still another embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative positional relationships, and the like of the component parts described below are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.

  FIG. 1 is a cross-sectional view of a cylindrical lithium ion battery to which the present invention is applied, cut along the longitudinal direction. In FIG. 1, a part of the cross section of the electrode plate group 9 is not shown. The cylindrical lithium ion battery 1 includes a battery can 3, a positive electrode side cover plate 5, a negative electrode side cover plate 7, an electrode plate group 9 infiltrated with an electrolyte, a positive electrode current collector 11, and a negative electrode current collector. And a body 13. The battery can 3 has a cylindrical shape with both ends opened by a nickel-plated steel material. Openings at both ends of the battery can 3 are respectively closed by the positive side cover plate 5 and the negative side cover plate 7.

  The positive electrode side cover plate 5 and the negative electrode side cover plate 7 are closed by the split safety valves 6 and 8. The cleavage type safety valves 6 and 8 generate gas in the battery can 3 and release the generated gas when the pressure in the battery can 3 exceeds a certain level. Screw portions are formed on the outer peripheral portions of the terminals 15 and 17, and nut members 21 are screwed into the screw portions, respectively. An insulating washer 23 is disposed between the nut member 21 and the positive electrode side cover plate 5 and the negative electrode side cover plate 7. Note that a screw member 25 as a sealing member is screwed to the positive electrode side cover plate 5 at a liquid injection port for containing an electrolytic solution.

  A non-aqueous electrolyte is infiltrated into the electrode plate group 9. In the cylindrical lithium ion battery 1, a solution obtained by dissolving lithium hexafluorophosphate (LiPF6) as an electrolyte in a mixed solvent of ethylene carbonate, dimethyl carbonate, and diethyl carbonate is used as a nonaqueous electrolytic solution.

  FIG. 2 is a view showing a state in which the electrode plate group 9 is wound. The electrode plate group 9 is configured by winding a belt-like positive electrode plate 27 and a belt-like negative electrode plate 29 in a spiral shape with a hollow cylindrical shaft core 33 as a center through a separator 31. In this specification, the hollow cylindrical shaft core includes a substantially cylindrical shaft core in which a concave portion is provided along the axis on a part of the outer peripheral surface or inner peripheral surface of the shaft core. The positive electrode plate 27 has a configuration in which a positive electrode mixture containing lithium manganate, which is a lithium transition metal double oxide, is applied almost uniformly on both surfaces of an aluminum foil as a positive electrode current collector plate. On one side extending in the longitudinal direction of the aluminum foil, an uncoated portion 35 that is not coated with the positive electrode mixture is formed. The uncoated part 35 is cut out in a comb-like shape, and a plurality of positive electrode lead pieces 37 are formed by the remaining part cut out. The negative electrode plate 29 has a configuration in which a negative electrode mixture containing carbon powder capable of occluding and releasing lithium ions as a negative electrode active material is applied almost uniformly on both surfaces of a rolled copper foil as a negative electrode current collector plate. On one side extending in the longitudinal direction of the copper foil, an uncoated portion 39 that is not coated with the negative electrode mixture is formed. The uncoated part 39 is notched in a comb-like shape, and a plurality of negative electrode lead pieces 41 are formed by the notched remaining part. In FIG. 1, a plurality of positive electrode lead pieces 37 are located on the positive electrode side cover plate 5 side, and a plurality of negative electrode lead pieces 41 are located on the negative electrode side cover plate 7 side. The separator 31 is formed of a polyethylene porous material through which lithium ions can pass. The separator 31 allows the passage of ions and prevents the positive electrode plate 27 and the negative electrode plate 29 from contacting each other. The shaft core 33 is made of polypropylene resin. Note that the detailed configuration of the positive electrode plate 27, the negative electrode plate 29, and the separator 31 is not related to the gist of the present invention, and thus detailed description thereof is omitted.

  Between the positive electrode side cover plate 5 and the end portion of the electrode plate group 9, a positive electrode current collector 11 to which a plurality of positive electrode lead pieces 37 are connected is disposed adjacent to the end portion of the electrode plate group 9. . Between the negative electrode side cover plate 7 and the end portion of the electrode plate group 9, a negative electrode current collector 13 to which a plurality of negative electrode lead pieces 41 are connected is disposed adjacent to the end portion of the electrode plate group 9. ing. The positive electrode current collector 11 and the negative electrode current collector 13 have substantially the same shape.

  The positive electrode current collector 11 includes a columnar portion 47 that is inserted into the shaft core 33 of the electrode plate group 9 on the side opposite to the side on which the output terminal portion 15 of the current collector body 43 is provided. By inserting the columnar portion 47 into one end portion of the shaft core 33, the positional relationship between the positive electrode current collector 11 and the electrode plate group 9 is established. The ends of the plurality of positive electrode lead pieces 37 are ultrasonically welded to the outer peripheral portion of the current collector body 43 of the positive electrode current collector 11.

  As shown in FIG. 1, the negative electrode current collector 13 has substantially the same shape as the positive electrode current collector 11. Also in the negative electrode current collector 13, the columnar portion 53 is inserted into the shaft core 33 of the electrode plate group 9, and the positional relationship between the negative electrode current collector 13 and the electrode plate group 9 is determined. The ends of the plurality of negative electrode lead pieces 41 are ultrasonically welded to the outer peripheral portion of the current collector body 49 of the negative electrode current collector 13. Since the negative electrode current collector 13 has substantially the same shape as the positive electrode current collector 11, the description thereof is omitted.

  FIG. 3 shows a cross-sectional view of the positive-side cover plate 5 in which the cleavage-type safety valve 6 is provided directly on the positive-side cover plate 5 in the embodiment of the present invention. The exhaust passage 6a has an inner diameter that tapers from the battery inner open end toward the battery outer open end. And the battery inner side open end of the exhaust passage 6a is covered and covered with the metal thin film 6b. The metal thin film 6b may be a commonly used one. The negative side cover plate 7 is also provided with a cleavable safety valve 8 that is substantially the same as that provided on the positive side cover plate 5.

  FIG. 4 shows a cross-sectional view of the positive-side cover plate 5 in which the cleavable safety valve 6 is provided on the positive-side cover plate 5 in another embodiment of the present invention. The exhaust passage 6 a is configured by a cylindrical body 6 c that penetrates the positive electrode side cover plate 5, and the battery outer open end protrudes from the surface of the positive electrode side cover plate 5. Specifically, the cylindrical body 6 c is screwed to the positive electrode side cover plate 5, and the rubber packing 19 is interposed between the flange 6 d of the cylindrical body 6 c and the surface of the positive electrode side cover plate 5. The exhaust passage 6a has an inner diameter that tapers from the battery inner open end toward the battery outer open end. The degree of expansion of the taper shape is appropriately adjusted according to the battery capacity and the amount of gas that will be released. And the battery inner side open end of the exhaust passage 6a is covered and covered with the metal thin film 6b. The negative side cover plate 7 is also provided with a cleavable safety valve 8 that is substantially the same as that provided on the positive side cover plate 5.

  FIG. 5 is a partially cutaway sectional view showing still another embodiment of the present invention. In the above embodiment in which the exhaust passage 6a is configured by the cylinder 6c, the battery outer open end of the exhaust passage 6a protrudes higher than the upper end of the terminal 15.

  Although the lithium ion battery has been described in the above embodiment, the present invention can of course be applied to other nonaqueous electrolyte secondary batteries.

DESCRIPTION OF SYMBOLS 1 Cylindrical lithium ion battery 3 Battery can 5 Positive side cover plate 6 Cleavage-type safety valve 6a Exhaust passage 6b Metal thin film 6c Cylindrical body 6d Ridge part 7 Negative side cover plate 8 Cleavage-type safety valve 9 Electrode plate group 11 Positive electrode collector 13 Negative electrode Current collector 15 Terminal 17 Terminal 19 Rubber packing 21 Nut member 23 Insulating washer 25 Screw member 27 Positive electrode plate 29 Negative electrode plate 31 Separator 33 Shaft core 35 Uncoated portion 37 Positive electrode lead piece 39 Uncoated portion 41 Negative electrode lead piece 43 Electrical body 47 Columnar part 49 Current collector body 53 Columnar part

Claims (4)

In the non-aqueous electrolyte secondary battery in which the electrode plate group is stored in the battery can together with the electrolyte, and the terminal plate and the cleavage-type safety valve are provided on the cover plate of the battery can,
The safety valve is composed of an exhaust passage that leads from the inside of the battery to the outside of the battery, and a metal thin film that is cleaved at a predetermined battery internal pressure,
The exhaust passage has an inner diameter that tapers from the battery inner open end toward the battery outer open end,
The non-aqueous electrolyte secondary battery, wherein the metal foil film covers a battery inner open end of an exhaust passage.   The nonaqueous electrolyte secondary battery according to claim 1, wherein the exhaust passage is provided directly in the cover plate.   2. The nonaqueous electrolyte secondary battery according to claim 1, wherein the exhaust passage is constituted by a cylindrical body penetrating the lid plate, and the battery outer open end protrudes from the lid plate surface.   4. The nonaqueous electrolyte secondary battery according to claim 3, wherein the battery outer open end of the exhaust passage projects higher than the upper end of the terminal.

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