JP5135805B2 - Battery pack - Google Patents

Description

  The present invention relates to a battery pack applied to, for example, a lithium ion secondary battery, and more particularly to a battery pack in which a cover is attached to a top opening and a bottom opening of an exterior material.

  In recent years, many portable electronic devices such as a camera-integrated VTR (Videotape Recorder), a mobile phone or a laptop computer have appeared, and their size and weight have been reduced. Along with this, the demand for batteries used as power sources for portable devices is growing rapidly, and the design of battery packs that are connected to devices is light, thin, and within the devices to achieve smaller and lighter devices. It is required to efficiently use the storage space. As a battery that satisfies such requirements, a lithium ion battery having a large energy density and output density is most suitable.

  Among them, lithium ion polymer secondary batteries using a gel polymer electrolyte are widely used in order to prevent liquid leakage that becomes a problem when conventional liquid electrolytes are used. Lithium ion polymer secondary battery is a laminate film made by laminating a belt-like positive electrode and negative electrode with electrode terminals connected and gel electrolyte applied on both sides via a separator and then winding in the longitudinal direction The battery cell is packaged with

  As an example of a battery pack, as shown in FIG. 13, a thin battery 50 is a film outer package 51, and a protruding recess 52 is provided at an end, and a printed circuit board 53 is disposed in parallel to the bottom surface of the protruding recess 52. Then, there is known one in which the temperature protection element 54 is fixed to the surface of the printed circuit board 53 facing the bottom surface portion, and the insulating sheet 55 is disposed between the temperature protection element 54 and the bottom surface portion (for example, patents). Reference 1).

  In Patent Document 1, in order to increase the external impact strength, a thin battery 50 is housed in a plastic case 56 to form a battery pack.

  As another example of the battery pack, there is a battery pack that secures external impact strength by changing the radius of curvature of the cover (see, for example, Patent Document 2).

Japanese Patent No. 3625773 JP 2006-202652 A

  However, in the conventional battery pack disclosed in Patent Document 1, since the thin battery 50 is housed in the plastic case 56, it is a value calculated by integrating the discharge voltage with the current, There is a possibility that the volume energy density, which is a value obtained by dividing the energy that can be stored by the volume of the battery (including the exterior), is lowered.

  Moreover, in the conventional battery pack disclosed in the above-mentioned Patent Document 2, since the bonding between the battery and the cover is only the adhesion between the resin and the resin, the bonded portion is easily peeled off by an external impact. There is a risk of peeling.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a battery pack that can increase the strength against external impact and does not decrease the yield when the cover is inserted. .

In order to achieve the above object, the battery pack according to the present invention includes:
An exterior material formed of a laminate film having a metal layer, and a battery element that is housed in the exterior material and includes a positive electrode and a negative electrode, and is fixed along the exterior material formed of the laminate film. of the opening of the opening and the bottom side of the top side a battery pack arranged resin cover, at least one area of the opening of the opening及beauty bottom-side of the top-side, the battery element accommodating the 70% to 90% with respect to the cross-sectional area including the outer Paneling part, the cover is a length of 0.5mm or more in the axial direction of the outer package, at least a notch or width 0.5mm 2 It is characterized by having more than one .

  According to the battery pack having the above configuration, the cross section of the injected resin becomes larger as it approaches the battery element, so that the strength against external impact can be increased by the anchor effect.

  The area of the opening on the top side and the opening on the bottom side described above is 70% to 90% with respect to a cross-sectional area including the exterior material portion.

  According to the battery pack having the above configuration, since the cross section of the solidified resin becomes larger as it approaches the battery element, the anchor effect increases the strength against external impact, and in addition, the exterior material matching portion that bends along the arc. Does not increase and the radius of the arc does not decrease, so that the yield at the time of inserting the cover is not lowered.

  The cover described above is characterized in that it has at least two notches having a length of 0.5 mm or more and a width of 0.5 mm or more in the axial direction of the exterior material.

  According to the battery pack having the above configuration, the resin is easily filled between the outside of the cover and the exterior material through the notch, and since there are two notches, it is difficult to form a portion that is not sufficiently filled.

  According to the battery pack of the present invention, it is possible to provide a battery pack that can increase the strength against external impact and does not reduce the yield when the cover is inserted.

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

  FIG. 1 is an exploded perspective view of a battery pack according to an embodiment of the present invention, FIG. 2 is a cross-sectional view taken along the line I-I including the cross section taken along the line II-II of FIG. 4A, 4B, and 4C are a plan view, a front view, a right side view, and FIG. 5 showing the periphery of the exterior material including the battery element shown in FIG. It is sectional drawing of the soft laminate material of the exterior material used for a battery pack. 6 is a cross-sectional view of the hard laminate material of the exterior material used in the battery pack shown in FIG. 1, FIG. 7 is an external perspective view of the exterior material wound around the battery element shown in FIG. 3, and FIG. FIG. 9 to FIG. 11 are sectional views corresponding to the section taken along the line II-II of FIG. 1, and FIG. 12 is an assembled external perspective view of the battery pack of FIG. is there. Table 1 is a comparison table of the drop test and production yield of the examples.

  As shown in FIG. 1, a battery pack 10 according to an embodiment of the present invention includes an exterior material 11 having both ends opened, a battery element (see FIG. 3) 12 housed in the exterior material 11, and an exterior. A battery pack for a rectangular or flat lithium ion polymer secondary battery including a top cover 13 fitted to the opened front end of the material 11 and a bottom cover 14 fitted to the rear end. . In the following description, the side on which the top cover 13 is fitted is referred to as the top side, and the side on which the bottom cover 14 is fitted is referred to as the bottom side.

  The exterior material 11 is plate-shaped as a whole, and is rectangular when viewed from the surface direction. The openings 15 and 16 at both ends of the exterior material 11 have a rectangular shape as a whole, and are formed so as to bulge so that both short sides form an elliptical arc toward the outside.

  The battery element 12 is, for example, a rectangular or flat wound battery element.

  The top cover 13 and the bottom cover 14 are formed into shapes that can be fitted into the openings 15 and 16 at both ends of the exterior material 11, and specifically, when viewed from the front, the top cover 13 and the bottom cover 14 are rectangular as a whole. Both short sides bulge and form so as to form an elliptical arc toward the outside.

  The bottom cover 14 is formed with a pair of notches 17 at symmetrical positions on both short sides thereof. The notch 17 has a length L1 of 0.5 mm or more in the axial direction of the exterior material 11 and a width L2 of 0.5 mm or more. The notch 17 has a function of facilitating filling of the resin injected for bonding the bottom cover 14 and the exterior material 11 between the outside of the bottom cover 14 and the exterior material 11.

  At this time, when the notch 17 has a length and width smaller than 0.5 mm, the resin is not sufficiently filled between the outside of the bottom cover 14 and the exterior material 11, and the bottom cover 14 is peeled off by an external impact. Incidence increases. Accordingly, the length L1 is preferably 1.0 mm or more and the width L2 is preferably 1.0 mm or more.

  Further, if the cutout portion 17 is provided at one place, the resin is not sufficiently filled, and the rate of occurrence of peeling of the bottom cover 14 due to external impact is increased. The notch 17 may be formed in the top cover 13 in the same manner as the bottom cover 14 in addition to the bottom cover 14.

  As shown in FIG. 2, the area AR <b> 1 of the bottom opening 16 is set to 70% to 90% with respect to the cross-sectional area AR <b> 2 including the outer peripheral portion 18 of the exterior member 11 that houses the battery element 12. Therefore, the opening 16 on the bottom side is smaller than the outer peripheral portion 18 of the exterior member 11 that houses the battery element 12.

  At this time, when the area AR1 of the opening 16 on the bottom side is set to a value exceeding 90% with respect to the cross-sectional area AR2 including the outer peripheral portion 18 of the exterior member 11 that stores the battery element 12, the battery element 12 is stored. Since the deviation between the cross-sectional area AR2 of the outer peripheral portion 18 of the exterior material 11 and the area AR1 of the opening 16 on the bottom side is small, the injected resin is solidified, and the rate of occurrence of peeling of the bottom cover 14 due to external impact is caused by the anchor effect. descend.

  On the contrary, when the area AR1 of the opening 16 on the bottom side is set to a value not exceeding 70% with respect to the cross-sectional area AR2 including the outer peripheral portion 18 of the exterior member 11 that houses the battery element 12, the bottom cover 14 is Workability when mounting is significantly reduced. Therefore, the area AR1 of the opening 16 on the bottom side is preferably 80% to 90%, and most preferably 85% to 90% with respect to the cross-sectional area AR2 including the outer peripheral portion 18 of the exterior member 11 that houses the battery element 12. . Such a ratio can also be applied to the opening 15 on the top side.

Next, with reference to FIGS. 3 to 6, the batteries element 12 used in the battery pack 10, an exterior member 11, a top cover 13, a bottom cover 14, will be described in more detail.

As shown in FIG. 3, batteries element 12, together with the belt-shaped positive electrode and a strip-shaped anode are wound in a longitudinal direction while being laminated through a polymer electrolyte and / or separator, positive electrode lead from the positive electrode and the negative electrode 19 And the negative electrode lead 20 is led out.

  In the positive electrode, a positive electrode active material layer is formed on a strip-shaped positive electrode current collector, and a polymer electrolyte layer is further formed on the positive electrode active material layer. In the negative electrode, a negative electrode active material layer is formed on a strip-shaped negative electrode current collector, and a polymer electrolyte layer is further formed on the negative electrode active material layer. The positive electrode lead 19 and the negative electrode lead 20 are joined to the positive electrode current collector and the negative electrode current collector by spot welding, resistance welding, or the like, respectively. In addition, as a positive electrode active material, a negative electrode active material, and a polymer electrolyte, the material already proposed can be used suitably.

The positive electrode can be composed of a metal oxide, a metal sulfide or a specific polymer material as the positive electrode active material depending on the type of the target battery. For example, in the case of constituting a lithium ion battery, as the positive electrode active material, LiXMO ₂ (wherein M represents one or more transition metals, X varies depending on the charge / discharge state of the battery, and usually 0.05 or more and 1 .10 or less) may be used. As the transition metal M constituting the lithium composite oxide, cobalt (Co), nickel (Ni), manganese (Mn) and the like are preferable.

Specific examples of such a lithium ion composite oxide include LiCoO ₂ , LiNiO ₂ , LiNiyCo ₁ -yO ₂ (where 0 <y <1), LiMn ₂ O _{4 and the} like. . These lithium composite oxides can generate a high voltage and have an excellent energy density. Also, as the positive electrode active _{material, TiS 2, MoS 2, NbSe} 2, V 2 O no lithium metal sulfides such as ₅ or may be used oxides. A plurality of these positive electrode active materials may be used in combination for the positive electrode. Further, when forming the positive electrode using the positive electrode active material as described above, a conductive agent, a binder or the like may be added.

As the negative electrode material, a material capable of doping and dedoping lithium can be used. For example, a non-graphite carbon material or a carbon material such as a graphite material can be used. More specifically, pyrolytic carbons, cokes (pitch coke, needle coke, petroleum coke), graphites, glassy carbons, organic polymer compound fired bodies (phenolic resin, furan resin, etc.) at an appropriate temperature. Carbon materials such as those obtained by firing and carbonization), carbon fibers, activated carbon, and the like can be used. Furthermore, as a material that can be doped or undoped with lithium, a polymer such as polyacetylene or polypyrrole or an oxide such as SnO ₂ can be used. When forming the negative electrode from such a material, a binder or the like may be added.

  The polymer electrolyte is obtained by incorporating a polymer electrolyte, an electrolytic solution, and an electrolyte salt into a polymer into a gel. The polymer material has a property compatible with the electrolytic solution, such as silicon gel, acrylogen, acrylonitrile gel, polyphosphazene modified polymer, polyethylene oxide, polypropylene oxide, and composite polymers, cross-linked polymers, modified polymers thereof, etc. Alternatively, as the fluorine-based polymer, for example, a polymer material such as poly (vinylidene fluoride), poly (vinylidene fluoride-co-hexafluoropropylene), or poly (vinylidene fluoride-co-trifluoroethylene), and Mixtures of these are used.

As the electrolyte component, the above-described polymer material can be dispersed, and as an aprotic solvent, for example, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), or the like is used. As the electrolyte salt, one that is compatible with a solvent is used, and a combination of a cation and an anion is used. As the cation, an alkali metal or an alkaline earth metal is used. As the anion, Cl ⁻ , Br ⁻ , I ⁻ , SCN ⁻ , ClO ₄ ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , CF ₃ SO ₃ ^{− and the} like are used. Specifically, lithium hexafluorophosphate or lithium tetrafluoroborate is used in the electrolyte salt at a concentration at which it can be dissolved in the electrolytic solution.

  As shown in FIGS. 4A, 4B, and 4C, the exterior material 11 includes a soft laminate material 22 provided with a recess 21 for housing the battery element 12, and a soft laminate material 22 on the soft laminate material 22. And a hard laminate 23 that is overlapped so as to cover the recess 21. For example, the recess 21 is formed according to the shape of the battery element 12 by drawing with a mold in advance. A heat welding sheet 24 is provided on the outer surface at a position corresponding to the bottom surface of the recess 21.

  The soft laminate material 22 has a rectangular shape, and has a top side long side 25 and a bottom side long side 26 having the same length, and a left side short side 27 and a right side short side 28 having the same length. Similarly, the hard laminate material 23 is also rectangular, and has a top-side long side 29 and a bottom-side long side 30 having the same length, and a left short side 31 and a right short side 32 having the same length. Note that the left and right in the description indicate the positional relationship as viewed toward FIG.

  The lengths of the top long side 29 and the bottom long side 30 of the hard laminate material 23 are such that the left short side 31 and the right short side 32 are in contact with each other in a state where the concave portion 21 in which the battery element 12 is housed is wrapped. Or are set to face each other with a slight gap. The lengths of the top side long side 25 and the bottom side long side 26 of the soft laminate material 22 are set shorter than the lengths of the top side long side 29 and the bottom side long side 30 of the hard laminate material 23. For example, the battery In a state in which the concave portion 21 in which the element 12 is accommodated is wrapped, the left short side 27 and the right short side 28 are in contact with each other or are opposed to each other with a slight gap. Here, the gap of the soft laminate material 22 is not limited to a slight width, and may have a certain width.

  The left short side 27 and the right short side 28 of the soft laminate material 22 are set shorter than the left short side 31 and the right short side 32 of the hard laminate material 23. Therefore, the soft laminate material 22 and the hard laminate material 23 can be laminated so that only the hard laminate material 23 exists on the top side. In this case, it is possible to obtain an advantage that the periphery of the top cover 13 provided in the opening 15 on the top side can be thermally welded by the polypropylene layer of the hard laminate material 23. It should be noted that the adhesive layer of the hard laminate material 23 is also exposed on the bottom side so that the periphery of the bottom cover 14 provided in the opening 16 on the bottom side can be thermally welded by the polypropylene layer of the hard laminate material 23. Anyway.

  The soft laminate material 22 is suitable for forming the concave portion 21 into which the battery element 12 is inserted by drawing and is softer than the hard laminate material 23.

  As shown in FIG. 5, the soft laminate material 22 includes a polypropylene (PP) layer 33 as an adhesive layer, a soft aluminum metal layer 34 as a metal layer, and a nylon layer or PET (polypropylene terephthalate) layer 35 as a surface protective layer. The polypropylene layer 33 is the inner side (the side in contact with the hard laminate material 23).

  The polypropylene layer 33 has a function of preventing alteration of the polymer electrolyte. As the polypropylene layer 33, for example, non-axially stretched polypropylene (CPP) or the like is used. The thickness of the polypropylene (PP) layer 33 is, for example, about 30 μm.

  The soft aluminum metal layer 34 has a function of preventing moisture from entering inside. As a material of the soft aluminum metal layer 34, for example, annealed aluminum (JIS A8021P-0) or (JIS A8079P-0) can be used. Moreover, the thickness of the soft aluminum metal layer 34 is selected in the range of about 30 μm to 130 μm, for example. The nylon layer or the PET layer 35 has a surface protecting function. For example, the thickness of the nylon layer or the PET layer 35 is set in a range of about 10 μm to 30 μm.

  As shown in FIG. 6, the hard laminate material 23 maintains the shape after bending and can withstand deformation from the outside. The hard laminate material 23 has a laminated structure in which a polypropylene (PP) layer 36 as an adhesive layer, a hard aluminum metal layer 37 as a metal layer, and a nylon layer or PET (polypropylene terephthalate) layer 38 as a surface protective layer are sequentially laminated. .

The polypropylene layer 36 and the nylon layer or PET layer 38 of the hard laminate material 23 are the same as the soft laminate material 22.

  The hard aluminum metal layer 37 is made of, for example, annealed aluminum (JIS A3003P-H18) or (JIS A3004P-H18) or the like and having a thickness in the range of about 30 μm to 130 μm. In addition, the thickness of each layer of the soft laminate material 22 and the hard laminate material 23 is selected in consideration of the total thickness.

  Referring to FIG. 1, the top cover 13 is provided with a circuit board, and a positive electrode lead 19 and a negative electrode lead 20 drawn from the battery element 12 are electrically connected to the circuit board. The circuit board is mounted with a protection circuit including a temperature protection element such as a fuse, PTC, and thermistor, an ID resistor for identifying the battery pack 10, and a plurality of, for example, three contact portions 39 are provided. It has been. In addition, the protection circuit includes an IC that controls monitoring of the secondary battery and control of the field effect transistor (FET), and a charge / discharge control FET.

  The PTC is connected in series with the battery element 12, and when the temperature of the battery element 12 becomes higher than the set temperature, the electrical resistance increases rapidly and substantially blocks the current flowing through the battery. A fuse and a thermistor are also connected in series with the battery element 12, and when the temperature of the battery element 12 becomes higher than the set temperature, the current flowing through the battery is cut off.

  In addition, the protection circuit including the IC for controlling the battery element 12 and controlling the FET and the charge / discharge control FET, the terminal voltage of the battery element 12 exceeds 4.3V to 4.4V. Since there is a risk of a dangerous state, the voltage of the battery element 12 is monitored, and if it exceeds 4.3 V to 4.4 V, the charge control FET is turned off and charging is prohibited. On the other hand, if the terminal voltage of the battery element 12 is over-discharged to the discharge prohibition voltage or lower and the secondary battery voltage becomes 0 V, the battery element 12 may be in an internal short-circuit state and recharging may not be possible. The battery voltage is monitored, and if it falls below the discharge inhibition voltage, the discharge control FET is turned off to inhibit discharge.

  Further, the top cover 13 is provided with one or more, preferably two or more through holes 40 penetrating from the surface facing the battery element 12 toward the surface opposite thereto. By providing two or more through-holes 40, at least one through-hole 40 can be used for venting air between the battery element 12 and the bottom cover 14 at the time of resin injection. Can be improved.

  Referring to FIG. 1, the bottom cover 14 closes the opening 16 on the bottom side. When viewed from the front, the bottom cover 14 has a rectangular shape as a whole, and both sides on the short side are elliptical toward the outside. It swells to form an arc. A side plate 41 for fitting into the opening 16 on the bottom side is provided on the surface of the bottom cover 14 on the battery element 12 side. The side plate 41 is provided along part or all of the outer periphery of the bottom cover 14.

  The bottom cover 14 is provided with one or more, preferably two or more through holes 42 penetrating from the surface facing the battery element 12 toward the surface opposite thereto. By providing two or more through-holes 42, at least one through-hole 42 can be used for venting air between the battery element 12 and the bottom cover 14 at the time of resin injection. Can be improved.

  Next, with reference to FIGS. 7-12, the manufacturing method of the battery pack 10 which concerns on one Embodiment of this invention is demonstrated.

  First, for example, a positive electrode, a negative electrode, and a separator each having a gel electrolyte layer formed on both surfaces are sequentially laminated in the order of the negative electrode, the separator, the positive electrode, and the separator, and this laminate is wound around a flat plate core and wound many times in the longitudinal direction. Thus, the wound battery element 12 shown in FIG. 3 is produced.

  Next, for example, the concave portion 21 for inserting the battery element 12 is formed in the soft laminate 22 by drawing in advance. At this time, referring to FIG. 4A, the battery element storage recess 21 of the soft laminate 22 is formed at a position slightly shifted to the right side with respect to the center position, for example. Then, the battery element 12 is accommodated in the recess 21 formed in the soft laminate material 22.

  Next, similarly, referring to FIG. 4A, the hard laminate material 23 is laminated at a position slightly shifted to the right side with respect to the soft laminate material 22. Thereby, in the state where the soft laminate material 22 and the hard laminate material 23 are laminated, a left region where only the soft laminate material 22 is located and a right region where only the hard laminate material 23 is located are generated. As described later, the positions are shifted in this way after the end portions of the soft laminate material 22 and the hard laminate material 23 are folded toward the outside of the bottom surface of the concave portion 21 of the soft laminate material 22, and then the soft laminate material 22. This is because the polypropylene layer 33 and the polypropylene layer 36 of the hard laminate material 23 are bonded with a certain width.

  Next, in the state of arrangement as shown in FIG. 4A, the four sides around the opening of the recess 21 are thermally welded while reducing the pressure. In this case, the entire portion where the polypropylene layers 33 and 36 overlap may be heat-welded. In this way, the battery element 12 is sealed by thermally welding the periphery of the recess 21.

  Next, referring to FIG. 4A, a heat welding sheet 24 having a predetermined shape is provided outside the bottom surface of the recess 21. The heat welding sheet 24 is an auxiliary member for bonding the nylon layer or the PET layer 35 of the soft laminate material 22 by applying a high temperature. Preferably, the thickness is about 10 to 60 μm and has a melting point of about 100 ° C. in view of the total thickness. The melting point of the heat welding sheet 24 is preferably such that it does not affect the battery element 12 by heat.

  Next, as shown in FIG. 7, both ends of the soft laminate material 22 and the hard laminate material 23, that is, the short sides 27 and 28 and the short sides 31 and 32, are directed to the outside of the bottom surface of the concave portion 21 of the soft laminate material 22. Fold it in. Then, the end portions of the soft laminate material 22 and the hard laminate material 23 are heat-welded, and the soft laminate material 22 is heat-welded to the outside of the bottom surface of the recess 21. As a result, the soft laminate material 22 and the hard laminate material 23 are fixed in a closed state so as to wrap around the recess 21 in which the battery element 12 is accommodated, thereby forming the top-side opening 15 and the bottom-side opening 16. Is done.

  As shown in FIG. 8, in a state where the battery element 12 is wrapped, the short side 31 and 32 of the hard laminate material 23 are in contact with each other, or a seam L5 in which the end faces face each other through a slight gap is formed. Arise. Further, a seam L6 is formed inside the hard laminate material 23, where the short sides 27 and 28 of the soft laminate material 22 are in contact with each other or their end faces are opposed to each other through a slight gap. Here, the case where the short sides 27 and 28 of the soft laminate 22 are in contact with each other or their end faces are opposed to each other with a slight gap is illustrated, but the gaps of a certain width are used. These end faces may be opposed to each other.

  Further, the nylon layer or the PET layer 35 of the soft laminate material 22 is positioned in contact with the upper side of the heat welding sheet 24. Therefore, the nylon layer or the PET layer 35 has a structure in which the heat welding sheet 24 is sandwiched, and the nylon layer or the PET layer 35 can be bonded to each other by applying heat from the outside. In addition, since the polypropylene layers 33 and 36 of the soft laminate 22 and the hard laminate 23 face each other, the polypropylene layers 33 and 36 can be bonded by applying heat from the outside.

  As described above, the battery pack 10 in which the laminate materials 22 and 23 also serve as the exterior material 11 is manufactured without using a resin box-shaped case and without arranging resin frames on both sides. The

  Next, a top cover fitting process is performed. In the top cover fitting process, the positive electrode lead 19 and the negative electrode lead 20 are connected to the top cover 13 by, for example, resistance welding or ultrasonic welding. The width of the top cover 13 is set to a value slightly smaller than the inner dimension of the height of the opening 15 on the top side end face of the exterior material 11.

  Next, the top cover 13 is pushed toward the opening 15 on the top side while bending the positive electrode lead 19 and the negative electrode lead 20. Since the width of the top cover 13 is set to a value slightly smaller than the inner size of the opening 15 on the top side as described above, the top cover 13 is accommodated in a space formed by the hard laminate material 23 near the end surface of the exterior material 11. be able to.

  Next, as shown in FIGS. 9 to 11, a bottom cover fitting step is performed. In the bottom cover fitting step, in order to reduce the area of the opening 16 on the bottom side, the arc portion of the bottom exterior material 11 is bent inward to form a wedge-shaped cutout 43, and the two wedge-shaped sides are formed. Together, the exterior material matching part 44 is formed, and the exterior material matching part 44 is bent along an arc. Then, the bottom cover 14 slightly smaller than the size of the bottom opening 16 is pushed into the bottom opening 16 formed. As a result, the side plate 41 of the bottom cover 14 is fitted to the bottom side opening 16, and the bottom side opening 16 is covered by the main body of the bottom cover 14.

  Next, a heat welding process is performed. In the thermal welding process, thermal welding is performed by pressing the entire length with a jig. That is, a heater block made of a metal such as copper is pressed from above and below near the top side end of the exterior material 11 to thermally weld the peripheral surface of the top cover 13 and the polypropylene layer 36 on the inner surface of the hard laminate material 23. .

  Next, a resin press-fitting process is performed. In the resin press-fitting step, the molten resin is filled between the battery element 12 and the top cover 13 through the through hole 40 of the top cover 13 and solidified. Thereby, the top cover 13 is bonded to the end surface of the battery element 12. As the molten resin, a hot melt adhesive, an epoxy resin, a urethane resin, or the like is appropriately used.

Next, the molten resin is filled between the battery element 12 and the bottom cover 14 through the through hole 42 of the bottom cover 14 and solidified. Thereby, the bottom cover 14 is bonded to the end surface of the battery element 12. The resin is sufficiently injected between the bottom cover 14 and the battery element 12, and the area AR1 of the bottom side of the open mouth portion 16, the cross-sectional area AR2 including an outer peripheral portion 18 of the outer package 11 for housing the battery element 12 On the other hand, since it is set to 70% to 90%, the cross section of the solidified resin becomes larger as it approaches the battery element 12, so that the anchor effect increases the strength against external impact. The resin to be filled is not particularly limited as long as it has a low viscosity state at the time of press-fitting. For example, polyamide-based hot melt, polyolefin-based hot melt, nylon, PP, PC, ABS or the like is used. be able to.

  As shown in FIG. 12, the battery pack 10 is manufactured through the above steps.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited only to these Examples.

Example 1
In Example 1, the battery pack 10 having a thickness of 4.3 mm and a width of 35 mm was manufactured using the steps as described above. Area AR1 of the bottom side of the open mouth portion 16, 90% with respect to the cross-sectional area AR2 including an outer peripheral portion 18 of the outer package 11 for housing the battery element 12, the bottom cover 14 has a width 1.0 mm, height 1. Two 0 mm cutouts 17 were provided.

(Example 2)
Example 2, except that the area AR1 of the bottom side of the open mouth portion 16, 85% with respect to the cross-sectional area AR2 including an outer peripheral portion 18 of the outer package 11 for housing the battery element 12, Example 1 above A battery pack 10 was produced in the same manner as described above.

(Example 3)
Example 3, except that the area AR1 of the bottom side of the open mouth portion 16, 80% with respect to the cross-sectional area AR2 including an outer peripheral portion 18 of the outer package 11 for housing the battery element 12, Example 1 above A battery pack 10 was produced in the same manner as described above.

Example 4
Example 4 except that the area AR1 of the bottom side of the open mouth portion 16, 70% with respect to the cross-sectional area AR2 including an outer peripheral portion 18 of the outer package 11 for housing the battery element 12, Example 1 above A battery pack 10 was produced in the same manner as described above.

(Example 5)
In Example 5, the battery pack 10 was produced in the same manner as in Example 1 except that the bottom cover 14 had the notch 17 having a width of 0.5 mm and a height of 0.5 mm.

(Comparative Example 1)
Comparative Example 1 does not reduce the area AR1 of the opening in the bottom side, the area AR1, except that 100% with respect to the cross-sectional area AR2 containing exterior material periphery portion, in the same manner as in Example 1 described above A battery pack was prepared.

(Comparative Example 2)
Comparative Example 2, the area AR1 of the opening in the bottom side, except for the 95% cross-sectional area AR2 containing exterior material periphery portion to produce a battery pack in the same manner as in Example 1 described above.

(Comparative Example 3)
Comparative Example 3, the area AR1 of the opening in the bottom side, except for the 65% cross-sectional area AR2 containing exterior material periphery portion to produce a battery pack in the same manner as in Example 1 described above.

(Comparative Example 4)
In Comparative Example 4, a battery pack was produced in the same manner as in Example 1 except that the bottom cover had a notch with a width of 1.0 mm and a height of 0.3 mm.

(Comparative Example 5)
In Comparative Example 5, a battery pack was manufactured in the same manner as in Example 1 except that the bottom cover had a notch with a width of 0.3 mm and a height of 1.0 mm.

(Comparative Example 6)
In Comparative Example 6, a battery pack was produced in the same manner as in Example 1 except that the bottom cover had one notch.

(Drop test)
For each of the obtained battery packs of Examples 1 to 5 and Comparative Examples 1 to 6, a random drop test from a height of 70 cm was repeated 50 times, and the number of batteries with the bottom cover peeled off was recorded. The peel occurrence rate (%) was calculated, and the results are shown in Table 1.

(Production yield)
1000 pieces of each of the obtained battery packs of Examples 1 to 5 and Comparative Examples 1 to 6 were produced, the yield (%) at that time was calculated, and the results are shown in Table 1.

As is evident from Table 1, the area AR1 of the opening in the bottom side, not more than 90% with respect to the cross-sectional area AR2 containing exterior material outer peripheral portion, a bottom cover, width 0.5mm or more, the height 0 In the battery packs of Examples 1 to 5 and Comparative Example 3 having two cutout portions of 5 mm or more, the bottom cover was not peeled off in the drop test.

This is because the area AR1 of the opening of the bottom side is smaller than the cross sectional area AR2 containing exterior material peripheral portion, since the cross section of the injected resin becomes larger as closer to the battery element 12, by its anchoring effect, against external impact It is estimated that the strength has increased. Moreover, since the size of the notch portion is sufficient, it can be seen that the resin is easily filled between the outside of the bottom cover and the exterior material, and since there are two notch portions, it is difficult to form a portion that is not sufficiently filled.

For these, the area AR1 of the opening in the bottom side, in the battery pack of the cross-sectional area AR2 against greater than 90% Comparative Example 1-2 containing the exterior material outer peripheral portion, the peeling of the bottom cover has occurred. Further, in the battery packs of Comparative Examples 4 to 6 in which the width and height of the notch portions are smaller than 0.5 mm and the comparative example 6 in which the number of notch portions is small, the bottom cover is peeled off due to insufficient resin filling. Occurred.

  Further, as is clear from Table 1, the yield at the time of manufacturing the battery pack is that the area AR1 of the opening on the bottom side is 70% or more with respect to the cross-sectional area AR2 including the outer peripheral portion of the exterior material. 5 and Comparative Examples 1-2 and Comparative Examples 4-6 were good. However, in Comparative Example 3 in which the area ratio is less than 70%, the exterior material matching portion that is bent along the arc increases, and the radius of the arc decreases, making it difficult to bend. Decreased.

Therefore, no peeling of the bottom cover is in drop test, the range for the cross-sectional area AR2 of the yield includes a sheathing material peripheral portion of the area AR1 of the opening in the good bottom side is 70% to 90%, the preferred range Is 80% to 90%. More preferably, it is 85% to 90%.

  And in the drop test of the width and height of the notch portion of the bottom cover, the bottom cover is not peeled and the range in which the yield is good is 0.5 mm or more. Preferably it is 1.0 mm or more. The number of notches is preferably 2 or more. The above-described embodiment is not limited to the bottom side, and the same effect can be obtained on the top side.

  As described above, according to the battery pack 10 of one embodiment of the present invention, the cross section of the injected resin becomes larger as the battery element 12 is approached, so that the strength against external impact is increased by the anchor effect. Can do.

  Moreover, according to the battery pack 10, since the cross section of the solidified resin becomes larger as the battery element 12 is approached, the anchor effect increases the strength against external impact, and in addition, the exterior material matching portion that bends along an arc. Since 44 does not increase and the radius of the arc does not decrease, the yield when the bottom cover 14 is inserted is not lowered.

  Further, according to the battery pack 10, the resin is easily filled between the outside of the bottom cover 14 and the exterior material 11 through the cutout portion 17, and since there are two cutout portions 17, it is difficult to form a portion that is not sufficiently filled. .

  In addition, this invention is not limited to embodiment mentioned above, In the range which does not deviate from the summary of this invention, it can change suitably. In addition, the material, shape, dimension, numerical value, form, number, arrangement location, and the like of each component in the above-described embodiment are arbitrary as long as the present invention can be achieved, and are not limited.

It is a disassembled perspective view of the battery pack of one Embodiment of this invention. It is the II sectional view taken on the line including the II-II sectional view of FIG. It is an external appearance perspective view of the battery element used for the battery pack shown in FIG. (A) is a top view around the exterior material including the battery element shown in FIG. 3, (B) is a front view of (A), and (C) is a right side view of (A). It is sectional drawing of the soft laminate material of the exterior material used for the battery pack shown in FIG. It is sectional drawing of the hard laminate material of the exterior material used for the battery pack shown in FIG. It is the external appearance perspective view which wound the exterior material around the battery element shown in FIG. It is sectional drawing of the exterior material of FIG. FIG. 2 is a cross-sectional view corresponding to a cross section taken along line II-II of FIG. 1 in the battery pack assembly process shown in FIG. 1. FIG. 2 is a cross-sectional view corresponding to a cross section taken along line II-II of FIG. 1 in the battery pack assembly process shown in FIG. 1. FIG. 2 is a cross-sectional view corresponding to a cross section taken along line II-II of FIG. 1 in the battery pack assembly process shown in FIG. 1. FIG. 2 is an assembled external perspective view of the battery pack of FIG. 1. It is the schematic of the conventional battery pack.

Explanation of symbols

10 Battery pack 12 Battery element 13 Top cover (cover)
14 Bottom cover (cover)
15 Opening on the top side 16 Opening on the bottom side 17 Notch 21 Recessed part 22 Soft laminate (laminate film)
23 Hard laminate (laminate film)
34 Soft aluminum metal layer (metal layer)
37 Hard aluminum metal layer (metal layer)

Claims (1)

An exterior material formed of a laminate film having a metal layer, and a battery element that is housed in the exterior material and includes a positive electrode and a negative electrode, and is fixed along the exterior material formed of the laminate film. A battery pack in which a resin cover is disposed in the opening on the top side and the opening on the bottom side,
The area of at least one of the opening part on the top side and the opening part on the bottom side is 70% to 90% with respect to a cross-sectional area including the exterior material part that houses the battery element ,
The battery pack , wherein the cover has at least two notches having a length of 0.5 mm or more and a width of 0.5 mm or more in the axial direction of the exterior material .

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