JP3968980B2 - Battery pack - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a battery pack including a plurality of single batteries, and more particularly to a battery pack including a temperature element for protecting a battery and a protection circuit. Specifically, the present invention relates to a battery pack suitable for use in a portable device.
[0002]
[Prior art]
In recent years, with the miniaturization of portable electronic devices such as portable radiotelephone devices, portable personal computers, portable video cameras, etc., secondary batteries such as lithium ion batteries having high energy density and excellent lightweight have become available. It has been put into practical use.
[0003]
If this lithium ion secondary battery is overcharged to a predetermined battery voltage or higher, deposition of lithium metal, decomposition of the positive electrode active material, decomposition of the organic electrolyte, etc. occur on the negative electrode, short circuit between the positive and negative electrodes, deterioration of battery performance, etc. It may cause. Conversely, when a lithium ion secondary battery is overdischarged below a predetermined battery voltage, the metal of the negative electrode current collector is ionized and eluted into the organic electrolyte, and the capacity due to the deterioration of the current collection function and the loss of the negative electrode active material It may cause a decrease.
[0004]
Therefore, in order to prevent overcharge and overdischarge of the lithium ion secondary battery, a printed wiring board on which a protection circuit is mounted is incorporated in the battery pack. For example, a battery pack (battery pack) in which a protective circuit and a secondary battery are housed in a molded case made of resin or the like is known.
[0005]
[Problems to be solved by the invention]
In recent portable devices such as portable audio devices, mobile phones, notebook personal computers, video recorders, digital cameras, etc., it is also required to reduce the size and weight of the battery as the power source.
[0006]
However, as the number of safety devices as described above is increased in order to increase the safety of the battery, the weight and size of the entire battery or the entire device using the battery increase, and the convenience decreases.
[0007]
An object of the present invention is to provide a battery pack in which the safety of the battery is high and the battery can be reduced in size and weight.
[0008]
[Means for Solving the Problems]
The battery pack of the present invention is a battery pack having a plurality of unit cells formed by encapsulating battery element in the outer package, and a temperature fuse or PTC element is connected to at least one of the unit cells of the positive electrode lead and negative electrode lead, and have a protection circuit which is common to each unit cell, the temperature fuse or PTC element, that the positive electrode and negative electrode leads of該Gaiso material is integrated into the part that is drawn out It is a feature.
[0009]
Severe conditions for which safety is a problem for a battery can be roughly classified into four types: overcharge, overcurrent, overdischarge, and overheat. The result of this overcharge or overcurrent always leads to an increase in battery temperature, so it is the simplest and versatile to detect the temperature increase and shut off the battery operation. Therefore, in the battery pack of the present invention, a thermal fuse or a PTC element (hereinafter referred to as “ temperature element ”) is provided for each battery unit. As a result, any battery, such as overcharge, overcurrent, or overheat, which is abnormal, is at least ultimately detected by a temperature rise and the battery function is shut off.
[0010]
By the way, considering the case where the temperature element stops operating, providing only the temperature element may cause a problem in safety. Therefore, in the battery pack of the present invention, a safety circuit common to each battery unit is provided after the temperature element, thereby detecting overcharge, overcurrent, and overdischarge, thereby further improving safety. . Since the temperature element itself is small and light, even if it is provided for each battery alone, the weight and volume do not increase that much. In addition, a relatively expensive protection circuit is not provided for each battery but is used in common for a single battery, so that the cost increase is minimal.
[0011]
In addition, when a current fuse is provided in the battery pack, the battery function can be reliably interrupted when an overcurrent occurs.
[0012]
Furthermore, by providing the protection circuit on the printed circuit board, not only the assembly of the protection circuit and thus the assembly of the battery pack can be facilitated, but also the protection circuit can be made smaller and the volume of the entire battery pack can be reduced. it can.
[0013]
In particular, the entire battery pack can be made more compact by stacking flat battery units in the thickness direction and further providing a printed wiring board so as to face the end face of the stack.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
The battery according to the embodiment will be described below with reference to the drawings. FIG. 1 is a block diagram according to the embodiment, FIG. 2 is a perspective view of a single battery of the battery pack, FIGS. 3A and 3B are exploded perspective views of the battery pack, and FIGS. FIGS. 8A and 8B are perspective views showing a stacking process of a single battery, and FIGS. 9A and 9B are views of the battery stack, connector, and circuit board. It is a perspective view which shows a connection structure.
[0015]
As shown in FIG. 3, a plurality (eight in the figure) of flat battery units 50 are stacked in the thickness direction, and the printed wiring board 60 faces the one end surface of the stacked body of the battery units 50. Be placed. A secondary battery protection circuit is mounted on the printed wiring board 60. As will be described later, each battery unit 50 is obtained by encapsulating a battery element with an exterior material, and a positive electrode lead 21 and a negative electrode lead 21 connected to the battery element are drawn out of the exterior material.
[0016]
One lead 21 is directly connected to the connector 63 (FIG. 9) via the wiring 61. One end of a thermal fuse 70 is connected to the other lead 21, and the other end of the thermal fuse 70 is connected to a connector 75 via a wiring 74. These connectors 63 and 75 are attached to the mating connectors 64 and 76 of the printed wiring board.
[0017]
As shown in FIG. 4, the wiring 61 is fixed through a metal connection chip fitting called a spectacle terminal 80. The eyeglass terminal 80 is well known, and the wiring 61 is inserted into the cylindrical portion 81 on one end side, and the wiring 61 and the eyeglass terminal 80 are fixed by caulking the cylindrical portion 81. A hole 82 is provided on the other end side of the eyeglass terminal 80, and a rivet 84 is inserted into the hole 83 of the lead 21 and the hole 82, and the tip of the rivet 84 is caulked so that the eyeglass terminal 80 and the lead 21 And are fixed. After this fixing, the leads 21 and the spectacle terminals 80 are covered with an insulating tape 86 as shown in FIG.
[0018]
As shown in FIGS. 6 and 7, one end of the thermal fuse 70 is fixed to the other lead 21 by a rivet 84.
[0019]
The temperature fuse 70 is formed by connecting a pair of terminal pieces 71 and 73 to both ends of a fuse body 72. The thermal fuse 70 is arranged in a direction parallel to the end of the battery unit 50, and one terminal piece 71 is fixed to the lead 21 by the rivet 84 as described above. The wiring 74 is fixed to the other terminal piece 73 by the spectacle terminal 80 and the rivet 84.
[0020]
As shown in FIG. 6, after connecting the terminal piece 71 of the thermal fuse 70 to the lead 21, an adhesive 78 is attached to the flap 4 </ b> F of the battery unit 50, and then the lead 21 is folded back 180 ° from the base side. Is adhered to the flap 4F. Thereby, the thermal fuse 70 and the battery unit 50 are integrated.
[0021]
The battery unit 50 in which the temperature fuses 70 are integrated in this way is laminated in the thickness direction of the battery unit 50 as shown in FIG. 3 and fixed by the adhesive tape 52 to form a rectangular parallelepiped laminate 51. A side support 53 made of a rubber sheet is applied to a pair of longitudinal side surfaces of the laminate 51, and an end support 54 made of a rubber sheet is applied to one end surface (side surface in the short direction).
[0022]
A printed wiring board 60 is disposed facing the remaining end face of the multilayer body 51 via a block-shaped terminal support 55.
[0023]
The laminated body 51 is housed in a battery pack casing 57 together with the supports 53, 54, 55 and the printed wiring board 60. The casing 57 is covered with a lid 57a and joined by ultrasonic welding or the like. It is said.
[0024]
As shown in FIG. 1, a protection circuit 66, a fuse 67 and a thermistor 68 are mounted on the printed wiring board 60, and a terminal 69 for energizing an external device such as a mobile phone is connected to the fuse 67. The fuse 67 is connected in parallel to each battery unit 50 via the protection circuit 66. The protection circuit 66 is configured to shut off the circuit when the temperature detected by the thermistor 68 exceeds a predetermined temperature. The protection circuit 66 is configured to shut off the circuit when an overcharge, overdischarge, or overcurrent is detected.
[0025]
The battery units 50 may be connected in series, but may be connected in parallel as shown in order to increase the battery capacity.
[0026]
In the embodiment of FIGS. 1 to 9, the laminated body 51 of the battery unit 50 is bundled with the adhesive tape 52. As shown in FIG. 10, the side support 53 is applied to both side surfaces of the laminated body 51, and the shrink film 58 is attached. After the circulation, the shrink film 58 may be heat-shrinked to bind the laminate 51.
[0027]
In the embodiment shown in FIGS. 1 to 9, a non-recoverable temperature fuse is used as a temperature element provided for each battery unit. However, this can be replaced with a resettable PTC element.
[0028]
Hereinafter, a preferred embodiment of the battery unit will be described with reference to FIG. 2 and FIGS. 13 is an exploded perspective view of the battery unit, FIG. 14 is a cross-sectional view of the main part of the battery unit, and FIG. 15 is a schematic perspective view of the battery element.
[0029]
This battery unit is obtained by housing the battery element 1 in the recess 2a of the exterior material 2 and then covering the exterior material 3 with the exterior material 2 and joining the peripheral portions 2a and 3a of the exterior materials 2 and 3 by vacuum sealing. is there.
[0030]
As shown in FIG. 13, the exterior material 2 has a flat plate shape. The outer packaging material 3 is a shallow, open box-like box having a housing portion 3b formed of a rectangular box-shaped concave portion and a peripheral edge portion 3a projecting outwardly in a flange shape from the four peripheral edges of the housing portion 3b.
[0031]
As shown in FIGS. 14 and 15, the battery element 1 is formed by stacking a plurality of unit battery elements. The tab 4a or 4b is pulled out from the unit battery element. The tabs 4a from the positive electrode are bundled (that is, overlapped with each other), and the positive electrode lead 21 is joined. The tabs 4b from the negative electrode are also bundled, and the negative electrode lead 21 is joined.
[0032]
The battery element 1 is accommodated in the accommodating portion 3b of the exterior material 3, and the exterior material 2 is covered. The pair of leads 21 extending from the battery element 1 are drawn out through the mating surfaces of the peripheral edges 2a and 3a of one side of the exterior materials 2 and 3, respectively. Thereafter, the peripheral edges 2a, 3a of the four peripheral edges of the outer packaging materials 2, 3 are hermetically joined by a technique such as thermocompression bonding or ultrasonic welding in a reduced pressure (preferably vacuum) atmosphere. 3 is enclosed.
[0033]
By joining the peripheral portions 2a and 3a, joined pieces (flaps) 4A and 4F are formed. The flaps 4A and 4F project outward from the enveloping portion 4B encapsulating the battery element 1. Therefore, the joining piece portion 4A is bent along the encapsulating portion 4B, and is fastened to the side surface of the encapsulating portion 4B with an adhesive, an adhesive tape (not shown), or the like.
[0034]
In FIG. 13, the exterior materials 2 and 3 are separate bodies. However, in the present invention, the exterior materials 2 and 3 may be integrated as a series as shown in FIG. In FIG. 17, one side of the exterior material 3 and one side of the exterior material 2 are connected, and the exterior material 2 has a lid shape that is connected to the exterior material 3 so as to be bendable. A concave portion of the accommodating portion 3b is formed from one side where the exterior materials 2 and 3 are continuous, and the same configuration as that of FIG. 13 is provided except that a flap (joining piece portion) is not formed on the one side.
[0035]
In FIGS. 13 and 16, the exterior material 3 having the accommodating portion 3b and the flat exterior material 2 are shown. However, in the present invention, as shown in FIG. 17, the shallow box-like accommodating portions 6b and 7b and Alternatively, the battery element 1 may be encapsulated by the exterior members 6 and 7 having the peripheral portions 6a and 7a protruding from the four peripheral edges of the housing portions 6b and 7b. In FIG. 17, the exterior materials 6 and 7 are integrated in series, but these may be separated as in FIG. 14.
[0036]
In the present invention, as shown in FIG. 18, one flat sheet-like exterior material 8 is folded back into two along the central piece 8a to form two pieces of the first piece 8A and the second side 8B, The battery element 1 is interposed between the first piece 8A and the second piece 8B, and the battery element 1 is sealed by joining the peripheral portions 8b of the first piece 8A and the second piece 8B as shown in FIG. May be.
[0037]
In this embodiment, since the bent flap (joining piece portion 4A) is fitted along the enveloping portion 4B and fixed with an adhesive or an adhesive tape, the strength and rigidity of the battery side surface are secured. Is expensive.
[0038]
However, in the present invention, this flap 4A may remain projecting laterally from the enveloping part 4B.
[0039]
FIG. 11 is a perspective view showing a configuration in the case where the battery unit 50 ′ having the overhanging encapsulating portion 4B is laminated, and FIG. 12 is a cross-sectional view of the battery pack. A support 53 ′ applied to both side surfaces of the stacked body 51 ′ of the battery unit 50 ′ has a plurality of concave strips 53 a on a plate surface facing the stacked body 51 ′. Each concave strip 53a is extended in parallel in the extending direction of the flap 4A. The flap 4A is received by the concave strip 53a and the support 53 ′ is applied to the side surface of the laminated body 51 ′. Then, the laminate 51 ′ and the support 53 ′ are wrapped around the shrink film 58, and the shrink film 58 is overheated and contracted so that the laminate 51 ′ and the support 53 ′ are bound and integrated. 11 and 12, the sponge 59 is applied to the upper and lower surfaces of the laminate 51, but the same sponge 59 is applied to the upper and lower surfaces of the laminate 59 in FIGS. 1 to 10. You may make it.
[0040]
The other structure of the laminated body of FIGS. 10-12 is the same as that of FIGS. 1-9, and this laminated body is made into a battery pack similarly to FIGS.
[0041]
The battery element 1 is a flat laminated battery element in which a plurality of flat unit battery elements having a positive electrode and a negative electrode are laminated in the thickness direction. Since the present invention is particularly suitable for application to a lithium secondary battery, a preferred configuration when the above battery element is a lithium secondary battery element will be described below.
[0042]
FIG. 20 shows a preferred example of the unit battery element of the lithium secondary battery element. This unit battery element is formed by laminating a positive electrode current collector 22, a positive electrode active material 23, a spacer (electrolyte layer) 24, a negative electrode active material 25, and a negative electrode current collector 26. Usually, the positive electrode active material 23 is bound on one side of the positive electrode current collector 22, and the negative electrode active material 25 is bound on one side of the negative electrode current collector 26.
[0043]
A plurality of unit battery elements are stacked to form a battery element. In this stacking, unit battery elements in a normal posture (FIG. 20) with the positive electrode on the upper side and the negative electrode on the lower side are reversed. Unit battery elements in a reverse posture (not shown) with the positive electrode on the lower side and the negative electrode on the upper side are alternately stacked. That is, the unit cell elements adjacent in the stacking direction are stacked so that the same polarity faces each other (that is, the positive electrodes and the negative electrodes) face each other.
[0044]
A positive electrode tab 4 a extends from the positive electrode current collector 22 of the unit battery element, and a negative electrode tab 4 b extends from the negative electrode current collector 26.
[0045]
In place of the unit battery element in which the positive electrode active material, the spacer, and the negative electrode active material are stacked between the positive electrode current collector and the negative electrode current collector as shown in FIG. 20, as shown in FIG. 21, the positive electrode current collector 15a or A positive electrode 11 and a negative electrode 12 are prepared by laminating a positive electrode active material 11a or a negative electrode active material 12a on both sides of a negative electrode current collector 15b as a core material, and the positive electrode 11 and the negative electrode 12 are connected to a spacer (electrolyte) as shown in FIG. Layers) 13 may be stacked alternately to form unit cell elements. In this case, a combination of a pair of positive electrode 11 and negative electrode 12 (strictly speaking, from the center in the thickness direction of current collector 15a of positive electrode 11 to the center in the thickness direction of current collector 15b of negative electrode 12) is a unit cell element. It corresponds to.
[0046]
As the positive electrode current collectors 15a and 22, metal foils such as aluminum, stainless steel and nickel can be used. Particularly, aluminum is preferable, and as the negative electrode current collectors 15b and 26, metal foils such as copper, stainless steel and nickel are used. In particular, copper is preferred. The thickness of the current collector is preferably about 1 to 30 μm.
[0047]
As the positive electrode active material, an inorganic compound or an organic compound can be used as long as it can occlude / release lithium ions. Examples of inorganic compounds include transition metal oxides, composite oxides of lithium and transition metals, transition metal sulfides, specifically transition metal oxides such as MnO, V ₂ O ₅ , V ₆ O1 ₁₃ , and TiO ₂ . Examples thereof include composite oxides of lithium and transition metals such as lithium nickelate, lithium cobaltate, and lithium manganate, transition metal sulfides such as TiS ₂ , FeS, and MoS ₂ . These compounds may be partially element-substituted in order to improve the characteristics. Examples of organic compounds include polyaniline, polypyrrole, polyacene, disulfide compounds, and polysulfide compounds. The positive electrode active material may be a mixture of these inorganic compounds and organic compounds. Particularly preferred is a composite oxide of lithium and at least one transition metal selected from the group consisting of cobalt, nickel and manganese.
[0048]
The particle size of the positive electrode active material may be appropriately selected in combination with other components of the battery, but the battery characteristics such as initial efficiency and cycle characteristics are usually 1 to 30 μm, particularly 1 to 10 μm. Since it improves, it is preferable.
[0049]
Examples of the negative electrode active material usually include carbon-based materials such as graphite and coke. This carbon-based material may be used as a mixture with a metal, a metal salt, an oxide, or the like, or as a cover. Negative electrode active materials include oxides and sulfates such as silicon, tin, zinc, manganese, iron, and nickel, lithium alloys such as lithium metal, Li—Al, Li—Bi—Cd, and Li—Sn—Cd, lithium transition Metal nitride, silicon, etc. can also be used. From the viewpoint of capacity, graphite or coke is preferable. The average particle diameter of the negative electrode active material is usually 12 μm or less, preferably 10 μm or less, from the viewpoint of improving battery characteristics such as initial efficiency, late characteristics, and cycle characteristics. If this particle size is too large, the electron conductivity is deteriorated. Moreover, it is 0.5 micrometer or more normally, Preferably it is 7 micrometers or more.
[0050]
In order to bind these positive electrode active material and negative electrode active material on the current collector, it is preferable to use a binder. As the binder, inorganic compounds such as silicate and glass, and various resins mainly composed of polymers can be used. Examples of the resin include alkane polymers such as polyethylene, polypropylene, and poly-1,1-dimethylethylene; unsaturated polymers such as polybutadiene and polyisoprene; polystyrene, polymethylstyrene, polyvinylpyridine, and poly-N-vinylpyrrolidone. Polymers having a ring such as polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, polymethyl acrylate, polyethyl acrylate, polyacrylic acid, polymethacrylic acid, polyacrylamide and the like; polyfluoride Fluorine-based resins such as vinyl, polyvinylidene fluoride, and polytetrafluoroethylene; CN group-containing polymers such as polyacrylonitrile and polyvinylidene cyanide; polyvinylidene such as polyvinyl acetate and polyvinyl alcohol Alcohol polymers; polyvinyl chloride, halogen-containing polymers such as polyvinylidene chloride; and conductive polymers such as polyaniline can be used. Further, a mixture such as the above-mentioned polymer, a modified body, a derivative, a random copolymer, an alternating copolymer, a graft copolymer, a block copolymer, and the like can be used.
[0051]
The blending amount of the binder with respect to 100 parts by weight of the active material is preferably 0.1 to 30 parts by weight, more preferably 1 to 15 parts by weight. If the amount of the resin is too small, the strength of the electrode may decrease. If the amount of the resin is too small, the capacity may be lowered or the rate characteristics may be lowered.
[0052]
In the positive electrode active material and the negative electrode active material, additives that exhibit various functions such as conductive materials and reinforcing materials, powders, fillers, and the like may be added as necessary.
[0053]
The conductive material is not particularly limited as long as it is capable of imparting conductivity by mixing an appropriate amount of the above active material. Usually, carbon powder such as acetylene black, carbon black, graphite, and various metal fibers and foils are used. Etc. Additives include trifluoropropylene carbonate, vinylene carbonate, 1,6-Dioxaspiro [4,4] nonane-2,7-dione, 12-crown-4-ether, etc., to increase the stability and life of the battery. Can be used. As the reinforcing material, various inorganic, organic spherical, fibrous fillers and the like can be used.
[0054]
As a method for forming an electrode on a current collector, for example, a powdered active material is mixed with a solvent together with a binder, and a dispersion paint is formed by a ball mill, sand mill, biaxial kneader, etc. A method of applying to the substrate and drying is preferably performed. In this case, the type of the solvent used is not particularly limited as long as it is inert to the electrode material and can dissolve the binder. For example, any of commonly used inorganic and organic solvents such as N-methylpyrrolidone can be used. Can also be used.
[0055]
Alternatively, the electrode material layer can be formed by pressure bonding or spraying on the current collector in a state where the active material is mixed with a binder and heated to be softened. Furthermore, it can also be formed by firing the active material alone on the current collector.
[0056]
An ion mobile phase is usually formed in the positive electrode and the negative electrode. The higher the proportion of the ion mobile phase in the electrode, the easier the ion movement, and this is preferable in terms of rate characteristics, while the lower one is higher in capacity. Preferably it is 10-50 volume%. As the material for the ion mobile phase, the same materials as those for the electrolyte phase described later can be used.
[0057]
The positive electrode active material and the negative electrode active material are preferably thicker in terms of capacity and thinner on the rate. The film thickness is usually 20 μm or more, preferably 30 μm or more, more preferably 50 μm or more, and most preferably 80 μm or more. The film thickness of the positive electrode and the negative electrode is usually 200 μm or less, preferably 150 μm or less.
[0058]
The spacers (electrolyte layers) 13 and 24 usually include various electrolytes such as a fluid electrolyte solution and a non-fluid electrolyte such as a gel electrolyte or a completely solid electrolyte. From the viewpoint of battery characteristics, an electrolytic solution or a gel electrolyte is preferable, and from the viewpoint of safety, a non-fluidic electrolyte is preferable. In particular, when a non-fluidic electrolyte is used, liquid leakage can be more effectively prevented with respect to a battery using a conventional electrolytic solution. Therefore, there is an advantage of using a case having shape changeability such as a laminate film described later. You can make the most of it.
[0059]
The electrolytic solution used for the electrolyte layer is usually a solution obtained by dissolving a supporting electrolyte in a non-aqueous solvent.
[0060]
The supporting electrolyte is a non-aqueous material that is stable with respect to the positive electrode active material and the negative electrode active material as an electrolyte, and that allows lithium ions to move for an electrochemical reaction with the positive electrode active material or the negative electrode active material. Any one can be used. Specific examples include lithium salts such as LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LiBF ₄ , LiClO ₄ , LiI, LiBr, LiCl, LiAlCl, LiHF ₂ , LiSCN, and LiSO ₃ CF ₂ . Of these, LiPF ₆ and LiClO ₄ are particularly preferable.
[0061]
The concentration in the case where these supporting electrolytes are used in a state dissolved in a non-aqueous solvent is preferably 0.5 to 2.5 mol / L. The non-aqueous solvent for dissolving the supporting electrolyte is not particularly limited, but a solvent having a relatively high dielectric constant is preferably used. Specifically, acyclic carbonates such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate, glymes such as tetrahydrofuran, 2-methyltetrahydrofuran and dimethoxyethane, lactones such as γ-butyllactone, One type or two or more types of sulfur compounds such as sulfolane and nitriles such as acetonitrile are exemplified.
[0062]
Of these, one or more solvents selected from cyclic carbonates such as ethylene carbonate and propylene carbonate, and acyclic carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate are particularly suitable. Moreover, you may add an additive etc. to these solvents. Examples of additives include trifluoropropylene carbonate, vinylene carbonate, 1,6-Dioxaspiro [4,4] nonane-2,7-dione, 12-crown-4-ether, etc., which improve battery stability and life. Can be used for purposes.
[0063]
The gel electrolyte that can be used for the electrolyte layer is usually formed by holding the electrolyte solution with a polymer. That is, the gel electrolyte is one in which the electrolyte is generally held in a polymer network and the fluidity is significantly reduced as a whole. Such a gel electrolyte exhibits characteristics such as ion conductivity that are close to those of a normal electrolyte solution, but its fluidity and volatility are remarkably suppressed and safety is enhanced. The ratio of the polymer in the gel electrolyte is preferably 1 to 50% by weight. If it is too low, the electrolytic solution cannot be retained, and liquid leakage may occur. If it is too high, the ionic conductivity tends to decrease and the battery characteristics tend to deteriorate.
[0064]
The polymer used in the gel electrolyte is not particularly limited as long as it is a polymer that can form a gel together with the electrolytic solution, and is produced by polycondensation such as polyester, polyamide, polycarbonate, polyimide, polyurethane, polyurea, etc. Such as those produced by polyaddition, and those produced by addition polymerization of acrylic derivatives such as polymethyl methacrylate and polyvinyls such as polyvinyl acetate, polyvinyl chloride, and polyvinylidene fluoride. Preferred examples of the polymer include polyacrylonitrile and polyvinylidene fluoride. Here, the polyvinylidene fluoride includes not only a homopolymer of vinylidene fluoride but also a copolymer with other monomer components such as hexafluoropropylene. Also, acrylic acid, methyl acrylate, ethyl acrylate, ethoxyethyl acrylate, methoxyethyl acrylate, ethoxyethoxyethyl acrylate, polyethylene glycol monoacrylate, ethoxyethyl methacrylate, methoxyethyl methacrylate, ethoxyethoxyethyl methacrylate, polyethylene glycol monomethacrylate, N , N-diethylaminoethyl acrylate, N, N-dimethylaminoethyl acrylate, glycidyl acrylate, allyl acrylate, acrylonitrile, N-vinyl pyrrolidone, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol acrylate, polyethylene glycol diacrylate, diethylene glycol The Methacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, acrylic polymer obtained by polymerizing an acrylic monomer such as polyethylene glycol dimethacrylate may also be used preferably.
[0065]
The weight average molecular weight of the polymer is usually in the range of 10,000 to 5,000,000. When the molecular weight is low, it is difficult to form a gel. If the molecular weight is high, the viscosity becomes too high and handling becomes difficult. The concentration of the polymer with respect to the electrolytic solution may be appropriately selected according to the molecular weight, but is preferably 0.1 to 30% by weight. If the concentration is too low, it is difficult to form a gel, and the retention of the electrolytic solution is lowered, which may cause problems of flow and liquid leakage. If the concentration is too high, the viscosity becomes too high, resulting in difficulty in the process, and the ratio of the electrolytic solution may be reduced, the ionic conductivity may be reduced, and battery characteristics such as late characteristics may be deteriorated.
[0066]
A completely solid electrolyte layer can also be used as the electrolyte layer. As such a solid electrolyte, various known solid electrolytes can be used. For example, it can be formed by mixing the polymer used in the gel electrolyte and the supporting electrolyte salt in an appropriate ratio. In this case, in order to increase conductivity, it is preferable to use a polymer having a high polarity and a skeleton having a large number of side chains.
[0067]
As the electrolyte layer, a material obtained by impregnating a porous sheet such as a porous film with the electrolyte may be used.
[0068]
The thickness of the electrolyte layer is usually 1 to 200 μm, preferably 5 to 100 μm.
[0069]
Specifically, a porous sheet having a thickness of usually 1 μm or more, preferably 5 μm or more, and usually 200 μm or less, preferably 100 μm or less is used. The porosity is usually 10 to 95%, preferably about 30 to 85%. As a material for the porous sheet, polyolefin or polyolefin in which a part or all of hydrogen atoms are fluorine-substituted can be used. Specifically, a microporous film, a nonwoven fabric, a woven fabric or the like formed using a synthetic resin such as polyolefin can be used.
[0070]
The planar shape of the electrode is arbitrary, and can be a square, a circle, a polygon, or the like.
[0071]
As shown in FIGS. 20 to 22, the current collectors 22, 26 or 15a, 15b are usually provided with lead coupling tabs 4a, 4b. When the electrode is square, a tab 4a protruding from the positive electrode current collector is usually formed near one side of one side of the electrode as shown in FIG. 20, and the tab 4b of the negative electrode current collector is near the other side. Form.
[0072]
Laminating a plurality of battery elements is effective in increasing the capacity of the battery. At this time, the tab 4a and the tab 4b from each battery element are usually joined in the thickness direction. Positive and negative lead coupling terminals are formed. As a result, a large capacity battery element 1 can be obtained.
[0073]
As shown in FIG. 14, the tabs 4a and 4b are coupled with leads 21 made of a flaky metal. As a result, the lead 21 and the positive electrode and negative electrode of the battery element are electrically coupled. The coupling between the tabs 4a and 4b and the coupling between the tabs 4a and 4b and the lead 21 can be performed by resistance welding such as spot welding, ultrasonic welding, or laser welding.
[0074]
In the present invention, it is preferable to use an annealed metal as at least one of the positive electrode lead and the negative electrode lead 21, preferably both. As a result, a battery excellent in not only strength but also bending durability can be obtained.
[0075]
Generally, aluminum, copper, nickel, SUS, or the like can be used as the type of metal used for the lead. A preferred material for the positive electrode lead is aluminum. A preferred material for the negative electrode lead is copper.
[0076]
The thickness of the lead 21 is usually 1 μm or more, preferably 10 μm or more, more preferably 20 μm or more, and most preferably 40 μm or more. If it is too thin, the mechanical strength of the lead such as tensile strength tends to be insufficient. The lead thickness is usually 1000 μm or less, preferably 500 μm or less, and more preferably 100 μm or less. If it is too thick, the bending durability tends to deteriorate, and the battery element tends to be difficult to seal with the case. The advantage of using an annealed metal to be described later for the lead is more conspicuous as the lead is thicker.
[0077]
The width of the lead is usually 1 mm or more and 20 mm or less, particularly about 1 mm or more and 10 mm or less, and the exposed length of the lead to the outside is usually about 1 mm or more and 50 mm or less.
[0078]
The exterior materials 2, 3, 6, 7, and 8 preferably have shape variability. As a result, it is possible to easily change the shape of the battery in various ways. Moreover, after the inside of the exterior material is evacuated, the peripheral portion of the exterior material is sealed, so that a pressing force can be applied to the battery element 1, and as a result, battery characteristics such as cycle characteristics are improved. be able to.
[0079]
As a material for the exterior material, a metal such as aluminum, nickel-plated iron or copper, a synthetic resin, or the like can be used. Preferably, a laminated composite material in which a metal and a synthetic resin are laminated is used. By using this laminated composite material, the exterior material can be made thinner and lighter, and the capacity of the entire battery can be improved.
[0080]
As the laminated composite material, a laminate in which a metal layer and a synthetic resin layer are laminated can be used. This metal layer is intended to prevent moisture from entering or maintain shape retention, and is composed of a single metal such as aluminum, iron, copper, nickel, titanium, molybdenum and gold, an alloy such as stainless steel and hastelloy, or a metal oxide such as aluminum oxide. It can be a thing. In particular, aluminum having excellent workability is preferable.
[0081]
Formation of a metal layer can be performed using metal foil, a metal vapor deposition film, metal sputtering, etc.
[0082]
The synthetic resin layer is used for protecting the case member or preventing the contact with the electrolyte, preventing the contact between the metal layer and the battery element, or protecting the metal layer. In the present invention, the synthetic resin layer is used. The elastic modulus and tensile elongation are not limited. Therefore, the synthetic resin in the present invention includes what is generally called an elastomer.
[0083]
As the synthetic resin, thermoplastic plastics, thermoplastic elastomers, thermosetting resins, and plastic alloys are used. These resins include those in which fillers such as fillers are mixed.
[0084]
In addition, the laminated composite material is provided with a synthetic resin layer on the outer surface of the metal layer to function as an outer protective layer, and prevents corrosion by the electrolyte and contact between the metal layer and the battery element on the inner surface. It can be set as the three-layer structure which laminated | stacked the synthetic resin layer which functions as an inner side protective layer for protecting.
[0085]
In this case, the resin used for the outer protective layer is preferably a resin excellent in chemical resistance and mechanical strength, such as polyethylene, polypropylene, modified polyolefin, ionomer, amorphous polyolefin, polyethylene terephthalate, and polyamide.
[0086]
As the inner protective layer, a chemical-resistant synthetic resin is used. For example, polyethylene, polypropylene, modified polyolefin, ionomer, ethylene-vinyl acetate copolymer, and the like can be used.
[0087]
Moreover, the composite material can also each provide an adhesive layer between the metal layer, the synthetic resin layer for forming the protective layer, and the synthetic resin layer for forming the corrosion resistant layer. Furthermore, in order to adhere the case members to each other, an adhesive layer made of a resin such as polyethylene or polypropylene that can be welded to the innermost surface of the composite material can be provided. A case is formed using these metals, synthetic resins, or composite materials. The case may be formed by fusing the periphery of a film-like body, or the sheet-like body may be drawn by vacuum forming, pressure forming, press forming or the like. It can also be formed by injection molding a synthetic resin. In the case of injection molding, the metal layer is usually formed by sputtering or the like.
[0088]
Providing the housing portion formed of a recess in the exterior material can be performed by drawing or the like.
[0089]
【The invention's effect】
As described above, the battery pack of the present invention has high safety against overcharge and overvoltage, and has a relatively small weight and volume.
[Brief description of the drawings]
FIG. 1 is a block diagram of a battery pack according to an embodiment.
FIG. 2 is a perspective view of a single battery of the battery pack according to the embodiment.
FIG. 3 is an exploded view of the battery pack according to the embodiment.
FIG. 4 is a perspective view showing wiring connection to a single battery in the embodiment.
FIG. 5 is a perspective view showing wiring connection to a single battery in the embodiment.
FIG. 6 is a perspective view showing thermal fuse connection to a single battery in the embodiment.
FIG. 7 is a perspective view showing wiring connection to a thermal fuse.
FIG. 8 is a perspective view showing a stack of single batteries.
FIG. 9 is a perspective view showing a battery stack, a connector, and a circuit board.
FIG. 10 is a perspective view showing a stack of single batteries and a support according to another embodiment.
FIG. 11 is a perspective view showing a stack of single batteries and a support according to still another embodiment.
12 is a cross-sectional view of the battery pack according to the embodiment of FIG. 11, wherein (a) is a cross-sectional view taken along line AA in FIG. (B), and (b) is B in FIG. A sectional view taken along line -B, and FIG. 5C is a sectional view taken along line CC in FIG.
FIG. 13 is an exploded perspective view of a single battery.
FIG. 14 is a cross-sectional view of the main part of a single battery.
FIG. 15 is a perspective view showing a battery element of a single battery.
FIG. 16 is a perspective view of another battery unit being manufactured.
FIG. 17 is a perspective view in the middle of manufacturing another battery unit.
FIG. 18 is a perspective view of another battery unit in the middle of manufacture.
19 is a plan view of the battery shown in FIG. 18 in the middle of production.
FIG. 20 is a schematic cross-sectional view of a unit battery element.
FIG. 21 is a schematic cross-sectional view of a positive electrode or a negative electrode.
FIG. 22 is a schematic cross-sectional view of a battery element.
[Explanation of symbols]
1 Battery element 2, 3, 6, 7, 8 Exterior material 4a, 4b Tab 4A, 4F Joint piece (flap)
4B Encapsulating part 11 Positive electrode 11a Positive electrode active material 12 Negative electrode 12b Negative electrode active material 13 Non-fluid electrolyte layer 15a Positive electrode current collector 15b Negative electrode current collector 21 Lead 22 Positive electrode current collector 23 Positive electrode active material 24 Spacer (electrolyte layer)
25 Negative electrode active material 26 Negative electrode current collector 50 Single battery 57 Casing 57a Lid 60 Printed circuit board 66 Protection circuit 67 Fuse 68 Thermistor 70 Thermal fuse 71, 73 Terminal piece 72 Thermal fuse body 78 Adhesive 80 Glasses terminal

Claims (7)

In a battery pack having a plurality of single batteries formed by encapsulating battery elements with an exterior material ,
A temperature fuse or PTC element is connected to at least one of the unit cells of the positive electrode lead and negative electrode lead, and have a protection circuit which is common to each unit cell,
The thermal fuse or the PTC element is integrated with a portion of the exterior material where the positive electrode lead and the negative electrode lead are drawn to the outside . 2. The battery pack according to claim 1, further comprising a current fuse common to each battery unit. 3. The battery pack according to claim 1, wherein the protection circuit is provided on a printed wiring board provided inside the battery pack. 4. The battery pack according to claim 1, wherein the single batteries are stacked in a thickness direction in a state of having a flat plate shape. 5. The battery pack according to claim 4, wherein the printed wiring board is provided so as to face an end face of the stack of single batteries. 6. The battery pack according to claim 1, wherein the battery element is a lithium secondary battery. 7. The battery pack according to claim 1, wherein the battery pack is for a portable device.

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