JP5387062B2 - Secondary battery - Google Patents

Description

  The present invention relates to a secondary battery in which a battery element is sealed inside by an exterior member.

  In order to discharge the gas generated inside the battery to the outside, a bridging structure part in which the bonding strength is weaker than in other areas in a part of the bonding area where the exterior member is bonded, and a gas for releasing the gas to the outside A secondary battery including an open chamber is known (see, for example, Patent Document 1).

International Publication No. 2006-098242

  If peeling starts in the above-mentioned crosslinked structure part, the performance of the secondary battery may be greatly reduced in a short time.

  The problem to be solved by the present invention is to provide a secondary battery capable of maintaining the performance for a long time.

The present invention relates to a seal portion bonded to the outer member, is sealed in the sealing portion, and a gas suction portion for sucking the gas, provided to extend from the inner circumference of the seal portion in the entire region up to the gas suction part, of the seal portion The first opening portion having relatively lower opening strength than other portions, the opening strength being relatively weaker than other portions of the seal portion, and the opening strength being relatively lower than that of the first opening portion. The above-mentioned problem is solved by providing a gas discharge part having a strong second opening part.

  According to the present invention, the gas generated in the battery can be first guided to the gas adsorbing portion by the first opening portion whose opening strength is relatively weaker than other portions in the sealing portion. And, since the opening strength of the second opening part is relatively weaker than other parts of the seal part and relatively stronger than the first opening part, the gas adsorbing part sufficiently adsorbs the gas. Later, the second opening can be opened and the gas discharged. For this reason, the time until the gas is discharged to the outside can be extended, and the performance of the secondary battery can be maintained long.

FIG. 1 is a plan view showing a laminated battery according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line II-II in FIG. FIG. 3 is a cross-sectional view taken along line III-III in FIG. FIG. 4 is an enlarged plan view showing the IV portion of FIG. FIG. 5 is a cross-sectional view taken along line VV in FIG. FIG. 6 is a plan view showing a gas discharge part of the laminated battery in the second embodiment of the present invention. FIG. 7 is a plan view showing a gas discharge part of the laminated battery in the third embodiment of the present invention. FIG. 8A is a diagram showing a state in which the laminated battery in the first embodiment of the present invention discharges gas (part 1). FIG. 8B is a diagram showing a state in which the laminated battery in the first embodiment of the present invention discharges gas (part 2). FIG. 8C is a diagram showing a state in which the laminated battery in the first embodiment of the present invention discharges gas (part 3). FIG. 8D is a diagram showing a state in which the laminated battery in the first embodiment of the present invention discharges gas (part 4).

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

<< First Embodiment >>
1 is a plan view showing a laminated battery according to a first embodiment of the present invention, FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1, and FIG. 3 is a cross-sectional view taken along line III-III in FIG. is there.

  First, a laminated battery 10 according to an embodiment of the present invention is a flat (thin) lithium ion secondary battery that can be stacked. As shown in FIGS. 1 to 3, the laminate battery 10 includes three positive plates 101, five separators 102, three negative plates 103, a positive terminal 104, a negative terminal 105, and an upper portion. It is comprised from the exterior member 106, the lower exterior member 107, and the electrolyte which is not specifically illustrated, for example, has a total thickness of 10 mm or less. In the present embodiment, the positive electrode plate 101, the separator 102, the negative electrode plate 103, and the electrolyte are particularly referred to as a power generation element 108.

  As shown in FIGS. 2 and 3, the positive electrode plate 101 of the power generation element 108 is respectively provided on the positive electrode side current collector 101a extending to the positive electrode terminal 104 and both main surfaces of a part of the positive electrode side current collector 101a. And formed positive electrode layers 101b and 101c.

  The positive electrode side current collector 101a is made of an electrochemically stable metal foil such as an aluminum foil, an aluminum alloy foil, a copper foil, or a nickel foil.

The positive electrode layers 101b and 101c are formed by mixing a positive electrode active material, a conductive agent such as carbon black, and an adhesive such as an aqueous dispersion of polytetrafluoroethylene with a part of the positive electrode side current collector 101a. It is formed by applying to both main surfaces, drying and rolling. Examples of the positive electrode active material include lithium composite oxides such as lithium nickelate (LiNiO ₂ ), lithium manganate (LiMnO ₂ ), and lithium cobaltate (LiCoO ₂ ), and chalcogen (S, Se, Te) compounds. Etc.

  The negative electrode plate 103 of the power generation element 108 includes a negative electrode side current collector 103a extending to the negative electrode terminal 105, and negative electrode layers 103b and 103c respectively formed on both main surfaces of a part of the negative electrode side current collector 103a. have.

  The negative electrode side current collector 103a is made of an electrochemically stable metal foil such as a nickel foil, a copper foil, a stainless steel foil, or an iron foil.

  The negative electrode layers 103b and 103c are prepared by mixing an aqueous dispersion of styrene butadiene rubber resin powder as a precursor material of an organic fired body with the negative electrode active material that absorbs and releases lithium ions of the positive electrode active material, and then drying the negative electrode active material. By pulverizing, the main material is carbonized styrene butadiene rubber supported on the surface of the carbon particles, and a binder such as an acrylic resin emulsion is further mixed therewith, and this mixture is mixed with one of the negative electrode side current collector 103a. It is formed by applying to both main surfaces of the part, drying and rolling. Examples of the negative electrode active material include amorphous carbon, non-graphitizable carbon, graphitizable carbon, and graphite.

  In particular, when amorphous carbon or non-graphitizable carbon is used as the negative electrode active material, the flatness of the potential during charge / discharge is poor and the output voltage decreases with the amount of discharge. Although unsuitable, it is advantageous because there is no sudden drop in output used as a power source for electric vehicles.

  The separator 102 of the power generation element 108 prevents a short circuit between the positive electrode plate 101 and the negative electrode plate 103 and may have a function of holding an electrolyte. The separator 102 is a microporous film made of a polyolefin such as polyethylene (PE) or polypropylene (PP), for example. When an overcurrent flows, the pores of the layer are blocked by the heat generation, thereby blocking the current. It also has a function.

  The separator in the present invention is not limited to a single-layer film such as polyolefin, but may be a three-layer structure in which a polypropylene film is sandwiched with a polyethylene film, or a laminate of a polyolefin microporous film and an organic nonwoven fabric or the like. it can. Thus, by forming the separator in multiple layers, various functions such as an overcurrent prevention function, an electrolyte holding function, and a separator shape maintenance (stiffness improvement) function can be provided.

  In the power generation element 108 described above, the positive electrode plates 101 and the negative electrode plates 103 are alternately stacked via the separators 102. The three positive plates 101 are respectively connected to the positive terminal 104 made of metal foil via the positive current collector 101a, while the three negative plates 103 are connected to the negative current collector 103a. In the same manner, each is connected to a negative electrode terminal 105 made of metal foil.

  The positive electrode plate 101, the separator 102, and the negative electrode plate 103 of the power generation element 108 are not limited to the above number in the present invention. For example, one positive plate, three separators, one negative plate However, the power generation element can be configured, and the number of positive plates, separators, and negative plates can be selected and configured as necessary.

  The positive electrode terminal 104 and the negative electrode terminal 105 are not particularly limited as long as they are electrochemically stable metal materials. Examples of the positive electrode terminal 104 include, for example, an aluminum foil and an aluminum alloy, similar to the positive electrode side current collector 101a described above. A foil, copper foil, nickel foil, etc. can be mentioned. Moreover, as the negative electrode terminal 105, nickel foil, copper foil, stainless steel foil, iron foil, etc. can be mentioned similarly to the above-mentioned negative electrode side collector 103a, for example. In the present embodiment, the metal foil itself constituting the current collectors 101 a and 103 a of the electrode plates 101 and 103 is extended to the electrode terminals 104 and 105, so that the electrode plates 101 and 103 are directly connected to the electrode terminals 104 and 105. Although connected, the current collectors 101a and 103a of the electrode plates 101 and 103 and the electrode terminals 104 and 105 are connected by materials and parts different from the metal foils constituting the current collectors 101a and 103a. Also good.

  The power generation element 108 is accommodated between an upper exterior member 106 molded into a cup shape as shown in FIGS. 2 and 3 and a flat lower exterior member 107. Further, the upper exterior member 106 and the lower exterior member 107 are sealed by the seal portion 20 in which the opposing outer edge portions are bonded together. Both the upper exterior member 106 and the lower exterior member 107 in the present embodiment are made of a laminate material (laminate film) made of an inner resin layer, a metal layer, and an outer resin layer, although not particularly illustrated.

  The inner resin layer of the laminate material is made of a resin film excellent in electrolytic solution resistance and heat fusion properties such as polyethylene, modified polyethylene, polypropylene, modified polypropylene, or ionomer. The metal layer is made of a metal foil such as aluminum. The outer resin layer is made of, for example, a resin film excellent in electrical insulation, such as a polyamide resin or a polyester resin.

  In order to maintain the sealing performance inside the laminated battery 10, a seal film made of, for example, polyethylene or polypropylene may be interposed in the seal portion 20. It is preferable from the viewpoint of heat-sealability that the sealing film is made of the same system as the synthetic resin material constituting the inner resin layer of the exterior members 106 and 107 in both the positive electrode terminal 104 and the negative electrode terminal 105. .

  These exterior members 106 and 107 enclose part of the power generation element 108 and the electrode terminals 104 and 105 described above, and in the space formed by the exterior members 106 and 107, lithium perchlorate or borofluoride is added to the organic liquid solvent. While injecting a liquid electrolyte in which a lithium salt such as lithium or lithium hexafluorophosphate as a solute is injected, the space is evacuated, and the outer peripheral portions of the exterior members 106 and 107 are heat-sealed by a hot press and sealed. Part 20 is formed. Thereby, a part of the power generation element 108 and the electrode terminals 104 and 105 are accommodated in the exterior members 106 and 107 and sealed.

  Examples of the organic liquid solvent include ester solvents such as propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), and methyl ethyl carbonate. The organic liquid solvent of the present invention is not limited to this, and an organic liquid solvent prepared by mixing and preparing an ether solvent such as γ-butylactone (γ-BL) or dietoshietane (DEE) in an ester solvent. It can also be used.

  4 is an enlarged plan view showing an IV portion of FIG. 3, and FIG. 5 is a cross-sectional view taken along line VV of FIG.

  As shown in FIGS. 4 and 5, a gas adsorbing portion 21 that adsorbs the gas generated by the battery element 108 and a first gas that leads the gas to the gas adsorbing portion 21 are provided at a substantially central portion of the long side of the seal portion 20. An opening portion 22 and a gas discharge portion 23 for discharging gas to the outside of the battery are provided. In the present embodiment, the gas adsorption unit 21, the first opening unit 22, and the gas discharge unit 23 may be provided on the short side portion of the seal unit 20.

  The gas adsorbing unit 21 is a member that adsorbs gas generated by the battery element 108 due to electrolyte decomposition due to long-time use of the battery or use in a high temperature area. The gas adsorption unit 21 can be configured using, for example, activated carbon, carbon nanotubes, carbon sheets, silica gel, activated alumina zeolite, or the like. The gas adsorbing portion 21 is disposed in the seal portion 20 approximately in the middle between the inner peripheral edge and the outer peripheral edge, and is sealed in the seal portion 20 formed by heat-sealing the exterior members 106 and 107.

  The first opening portion 22 is set to have the weakest opening strength (fusion strength, peel strength) in the seal portion 20, and is opened first in the seal portion 20 due to the increase in the internal pressure of the gas generated by the battery element 108. Thus, the gas is positively guided to the gas adsorption unit 21. For example, when the exterior members 106 and 107 are heat-sealed, the first opening portion 22 has a second temperature lower than the first temperature T1 when heat-sealing other portions of the seal portion 20. It is formed by heat fusion at T2 (T1> T2). In addition, a sheet film having a higher melting point than those of the inner resin layers or a mesh material subjected to crosslinking treatment is interposed between the exterior members 106 and 107, or the inner resin layer of at least one of the exterior members 106 and 107 is crosslinked. Thus, the first opening portion 22 may be formed.

  The first opening portion 22 is disposed between the inner peripheral edge of the seal portion 20 and the gas adsorption portion 21. In the present embodiment, the first opening portion 22 extends over the entire area from the inner peripheral edge of the seal portion 20 to the gas adsorption portion 21. Is provided. On the other hand, in the longitudinal direction of the laminated battery 10, the width is narrower than that of the gas adsorption unit 21 in the present embodiment, but the width may be the same as that of the gas adsorption unit 21, or from the gas adsorption unit 21. It is good also as a shape which spreads toward the inner periphery of the seal | sticker part 20. As shown in FIG.

  The gas discharge part 23 has a second opening part 231 that is opened next to the first opening part 22, and a through hole 232 that penetrates the exterior members 106 and 107.

  The second opening portion 231 is set to have a lower opening strength next to the first opening portion 22 in the seal portion 20 and discharges the gas after the gas adsorbing portion 21 has sufficiently adsorbed the gas. For example, when the exterior members 106 and 107 are heat-sealed, the second opening portion 231 is heated at a third temperature T3 that is lower than the first temperature T1 and higher than the second temperature T2. It is formed by fusing (T1> T3> T2). In addition, a sheet film having a higher melting point than those of the inner resin layers or a mesh material subjected to crosslinking treatment is interposed between the exterior members 106 and 107, or the inner resin layer of at least one of the exterior members 106 and 107 is crosslinked. Thus, the second opening portion 231 may be formed.

  In the present embodiment, the second opening portion 231 is disposed between the gas adsorption portion 21 and the outer peripheral edge of the seal portion 20. In the present embodiment, the width of the laminated battery 10 is narrower than that of the gas adsorbing portion 21. However, the width may be the same as that of the gas adsorbing portion 21. It is good also as a shape which spreads toward 20 outer periphery. Further, as shown in FIG. 6, the second opening portion 231 is disposed at a position offset from the first opening portion 22 and the gas adsorption portion 21, and one end thereof is connected to the inner peripheral edge of the seal portion 20. Also good.

  As shown in FIGS. 4 and 5, the through-hole 232 penetrates the exterior members 106 and 107 in the second opening portion 231, and when the first opening portion 22 and the second opening portion 231 are opened, The inside of the battery communicates with the outside through the through hole 232. Note that the through hole 232 may penetrate only one of the exterior members 106 and 107. Further, as shown in FIG. 7, the gas discharge part 23 is not provided with the through hole 232, and the second opening part 231 is directly connected to the outer peripheral edge of the seal part 20, and the second opening part 231 is the seal part. The gas may be discharged to the outside by opening at the outer end face of 20.

  The operation will be described below.

  8A to 8D are views showing how the laminated battery in the first embodiment of the present invention discharges gas.

  As shown in FIG. 8A, when the battery element 108 generates gas and the internal pressure rises, the exterior members 106 and 107 receive pressure, and a stress in the peeling direction is applied to the inner peripheral edge of the seal portion 20. The Here, since the opening strength of the first opening portion 22 is set to be the weakest in the seal portion 20, the stress in the peeling direction received by the seal portion 20 is concentrated on the first opening portion 22, and the seal In the part 20, the 1st opening part 22 peels first. The peeling of the first opening portion 22 progresses from the inner peripheral edge of the seal portion 20 toward the gas adsorption portion 21.

  As shown in FIG. 8B, when the peeling of the first opening portion 22 reaches the gas adsorbing portion 21 and the first opening portion 22 is opened, the gas generated inside the battery reaches the gas adsorbing portion 21, and the gas The adsorption part 21 adsorbs gas. As a result, an increase in the internal pressure of the battery due to the gas is suppressed.

  As shown in FIG. 8C, when the amount of gas generation exceeds the adsorption allowable amount of the gas adsorption unit 21, the seal unit 20 receives the stress in the peeling direction again. In the seal part 20, the second opening part 231 is set to have a weaker opening strength next to the first opening part 22, so that after the opening of the first opening part 22, the stress in the direction to be peeled off is applied. It concentrates on the 2nd opening part 231, and the 2nd opening part 231 peels. The peeling of the second opening portion 231 progresses toward the outer peripheral edge of the seal portion 20. Moreover, peeling of the 2nd opening part 231 is accelerated | stimulated also by the increase in the thickness and temperature of the gas adsorption part 21 accompanying gas adsorption.

  As shown in FIG. 8D, when the peeling of the second opening portion 231 reaches the through hole 232, the second opening portion 231 is also opened, and the battery is opened via the first opening portion 22 and the second opening portion 231. The inside and the through hole 232 communicate with each other, and the gas is discharged to the outside of the battery through the through hole 232.

  As described above, in the present embodiment, the gas generated inside the battery can be first guided to the gas adsorbing portion 21 by the first opening portion 22 having relatively lower opening strength than the other portions in the seal portion 20. Since the opening strength of the second opening portion 231 is relatively weaker than the other portions in the seal portion 20 and relatively stronger than the first opening portion 22, the gas adsorbing portion 21 has sufficient gas. The second unsealing part 231 can be unsealed and the gas can be discharged after adsorbing to the gas. For this reason, it is possible to lengthen the time from the start of peeling of the seal portion 20 until the gas is discharged to the outside, and the performance of the laminated battery 10 can be maintained long.

  For example, in an environment of 55 ° C., charging at 1 [C] from 2.5 [V] to 4.2 [V] and 1 [C] from 4.2 [V] to 2.5 [V] C] is repeated, the conventional structure in which the gas discharge unit is simply provided discharges the gas to the outside in 100 days, whereas in the structure of this embodiment, the gas is discharged to the outside until 120 days. There wasn't. This also shows that the performance of the laminate battery 10 of this embodiment can be maintained for a long time.

  Further, in the present embodiment, the first opening portion 22 is disposed inside the battery with respect to the second opening portion 231, so that the first opening portion 22 is first formed when the internal pressure increases due to the generation of gas. The gas can be positively guided to the gas adsorbing portion 21 by being opened.

  Furthermore, by disposing the gas adsorption part 21 between the first opening part 22 and the second opening part 231, the first opening part 22 reliably guides the gas to the gas adsorption part 21, It can be adsorbed by the gas adsorption part 21.

  In the present embodiment, the through hole 232 is provided in the second opening portion 231, or the second opening portion 231 is exposed at the outer end surface of the seal portion 20, whereby the gas can be discharged to the outside.

DESCRIPTION OF SYMBOLS 10 ... Laminate battery 101 ... Positive electrode plate 101a ... Positive electrode side collector 101b, 101c ... Positive electrode layer 102 ... Separator 103 ... Negative electrode plate 103a ... Negative electrode side collector 103b, 103c ... Negative electrode layer 104 ... Positive electrode terminal 105 ... Negative electrode terminal 106 ... Upper exterior member 107 ... Lower exterior member 108 ... Power generation element 20 ... Sealing part 21 ... Gas adsorption part 22 ... First opening part 23 ... Gas discharge part 231 ... Second opening part 232 ... Through hole

Claims (5)

It is a secondary battery that seals the battery element inside by a seal portion to which an exterior member is bonded,
The seal portion is
A gas discharge part for discharging the gas generated by the battery element to the outside;
A gas adsorbing part that is sealed in the seal part and adsorbs the gas;
A first opening part that is provided over the entire area from the inner peripheral edge of the seal part to the gas adsorbing part, and has a relatively lower opening strength than other parts of the seal part,
The gas discharge part has a second opening part whose opening strength is relatively weaker than other parts of the sealing part and whose opening strength is relatively stronger than that of the first opening part. Secondary battery.
The secondary battery according to claim 1,
The secondary battery is characterized in that the first opening part is disposed inside the battery with respect to the second opening part. The secondary battery according to claim 2,
The secondary battery according to claim 1, wherein the gas adsorbing portion is disposed between the first opening portion and the second opening portion. The secondary battery according to any one of claims 1 to 3,
The gas discharge part has a through-hole penetrating the exterior member,
The secondary battery is characterized in that the second opening portion can communicate with the through hole. The secondary battery according to any one of claims 1 to 3,
The secondary battery is characterized in that the second opening portion is exposed at an outer end face of the seal portion.

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