JP5098278B2 - Assembled battery - Google Patents

Description

  The present invention relates to an assembled battery formed by connecting a plurality of unit cells.

  The exterior member made of a sheet-like member is heat-sealed along the outer peripheral edge thereof to accommodate and seal the electrode plate, and the electrode terminals connected to the electrode plate are led out from the outer peripheral edge of the exterior member. Secondary batteries are known (see Patent Document 1). The output of this type of unit cell correlates with the total area of the electrode, and the unit cell capacity (full charge capacity) correlates with the amount of active material interposed between the electrodes.

  By the way, a conventional assembled battery in which a plurality of unit cells are connected is a combination of unit cells having the same capacity, and a dark current that flows to a load connected to the assembled battery, for example, a cell motor or an electrical component of an automobile (when the switch is OFF). The number of unit cells to be combined is determined according to the sum of the flowing currents), and the number of unit cells to be combined is determined according to the maximum output (maximum power consumption) of these loads.

  Therefore, even in a quantity that can sufficiently satisfy the sum of the dark currents flowing through the load, it is necessary to combine a larger number of single cells in order to satisfy the maximum output of the load. As a result, there has been a problem that the assembled battery is unnecessarily increased in size, weight, and cost.

JP 2005-56654 A

  An object of the present invention is to provide an assembled battery in which a suitable amount of single cells according to the dark current and output of a connected load are connected.

To achieve the above object, the battery pack of the present invention will become more unit cells connected in series, the assembled battery in which a plurality of loads are connected, the battery pack includes a plurality of first unit cells a first cell group formed by connecting a, and a second cell group formed by connecting a plurality of second unit cells and the output density is greater smaller capacity than the first unit cell is constructed by connecting in series, the relatively large load than dark current in the other loads of the plurality of loads, the first is connected only to a single cell group Rutotomoni, among the plurality of loads A load having a relatively low dark current compared to other loads is connected to the entire first cell group and the second cell group .

Further, in an assembled battery in which a plurality of unit cells are connected in series and a plurality of loads are connected, the assembled battery includes a first group of unit cells formed by connecting a plurality of first unit cells , A plurality of second unit cells connected by connecting a plurality of second unit cells having a smaller capacity and a higher output density than the first unit cells, and the plurality of loads A load that constantly consumes power is connected only to the first cell group, and a load that consumes power only at a specific moment among the plurality of loads is the first cell group and the second cell. It is connected to the whole cell group .

  In the present invention, the unit cell group is divided into a group having a large battery capacity and a small output density and a group having a small battery capacity and a large output density. Alternatively, a load that constantly consumes power is connected, while a load with a small dark current or a load that does not always consume power is connected to the entire battery pack.

  That is, according to the present invention, the first single cell group having a large battery capacity and a small output density is configured according to the dark current of the connected load, while the battery capacity is decreased according to the maximum output of the connected load. A second cell group having a high density is formed.

Since the battery capacity correlates with the amount of active material and the battery output correlates with the total electrode area, reducing the amount of active material by making the electrode total area equal reduces the battery capacity to the same battery capacity. The battery capacity is relatively small, but the battery is small, light and low cost.

The dark current of the connected load can be handled by the first unit cell group, and the maximum output of the connected load is the entire assembled battery including the first unit cell group and the second unit cell group. Can respond.

BEST MODE FOR CARRYING OUT THE INVENTION

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

FIG. 1 is a plan view showing an entire thin cell according to an embodiment of the present invention, FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1, and FIG. 3 (A) is an assembled battery according to an embodiment of the present invention. FIG. 3B is a side view showing a conventional assembled battery.

First, the structure of the unit cell will be described with reference to FIGS. The figure shows one thin single battery 10 (unit battery), and an assembled battery having a desired output and capacity is formed by stacking a plurality of thin batteries 10.

  The thin unit cell 10 of this example is a lithium-based thin secondary battery, and as shown in the figure, three positive plates 101, five separators 102, three negative plates 103, The positive electrode terminal 104, the negative electrode terminal 105, the upper exterior member 106, the lower exterior member 107, and an electrolyte not specifically shown are configured. Among these, 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.

  The positive electrode plate 101 constituting the power generation element 108 includes a positive electrode current collector 101a extending to the positive electrode terminal 104, and positive electrode layers 101b and 101c formed on both main surfaces of a part of the positive electrode current collector 101a, respectively. And having.

  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 positive electrode current collector 101a. It is formed by applying to both main surfaces of the part, 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 constituting 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 formed on both main surfaces of a part of the negative electrode side current collector 103a, respectively. And have.

  The negative electrode side current collector 103a of the negative electrode plate 103 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 pulverized after mixing and drying an aqueous dispersion of styrene butadiene rubber resin powder as a precursor of an organic fired body into the negative electrode active material that absorbs and releases lithium ions of the positive electrode active material. Thus, the main material is a carbon particle surface supporting carbonized styrene butadiene rubber, and a binder such as an acrylic resin emulsion is further mixed therewith, and this mixture is used as a part of the negative electrode side current collector 103a. It is formed by applying to both main surfaces, drying and rolling. Specific 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 when used as a power source for an electric vehicle because there is no sudden drop in output.

  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, 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 via a positive current collector 101a, while the three negative plates 103 are connected to a negative electrode via a negative current collector 103a. Each is connected to a terminal 105.

  The number of positive electrode plates, separators, and negative electrode plates constituting the power generation element is not limited to the above number in the present invention. For example, a power generation element can also be configured with one positive plate, three separators, and one negative plate, and the number of positive plates, separators, and negative plates can be selected as necessary. Can do.

  In particular, since the output (watt W = V · A) of the unit cell 10 correlates with the total area of the electrode and the full charge capacity (Coulomb Q = A · h) correlates with the amount of active material, for example, the total area of the electrode And by reducing the amount of active material, it is possible to obtain a unit cell 10 having a relatively small capacity but the same output. Since the battery 10 has a small amount of active material, the thickness of the battery is reduced, and a lightweight and inexpensive battery can be obtained. On the other hand, by making the amount of active material equal and reducing the total area of the electrodes, it is possible to obtain a unit cell 10 having a small output but the same capacity. That is, by changing the amount of active material and the total electrode area, the output per unit volume (output density) and the capacity (capacity density) can be changed.

  In the above unit cell 10, a unit cell in which the total area of the electrodes is made equal while the amount of the active material is reduced to, for example, about one-eighth is manufactured, and an assembled battery in which two types of unit cells 10a and 10b are combined is formed. . For example, the unit cell 10b in which the electrodes have the same size, the thickness is reduced to about one-fourth, the number of stacked layers is halved, and the active material amount is one-eighth, the battery capacity is 8 minutes. However, as shown in FIG. 3A, the thickness tb is thinner (ta> tb) and the weight wb is lighter (wa> wb) than the unit cell 10a. Further, the cost is reduced as the amount of the active material is reduced. Therefore, as compared with the assembled battery combining only the unit cells 10a shown in FIG. 5B, the thickness (size) of the entire assembled battery is reduced although the output is the same, and it is light and inexpensive. A high-capacity cell 10a is a unit cell having a relatively large capacity, a unit cell having the same output and a relatively small capacity, in other words, a unit cell having a relatively large output density (output per volume). 10b.

  Next, an example of an electric circuit using two types of cells, that is, the assembled battery 1 in which the high-capacity cell 10a and the high-power cell 10b are combined will be described. 4 to 7 are embodiments of an electric circuit using the assembled battery 1 according to the present invention, each of which includes three single cells 10a (corresponding to the first battery group of the present invention) and one single cell. The assembled battery 1 is configured by connecting a total of four unit cells of the battery 10b (corresponding to the second battery group of the present invention) in series. In addition, the quantity of the single cells 10a and 10b constituting the assembled battery 1 is merely an example, and can be configured with an arbitrary quantity.

  First, in the example shown in FIG. 4, the vehicle load 2 </ b> A and the vehicle load 2 </ b> B are driven by the assembled battery 1. The vehicle load 2A has no dark current, such as a cell motor or a watch, or a relatively small load, whereas the vehicle load 2B has a CPU that consumes current even when the switch is turned off, for example. Or a load such as a memory that has a relatively large dark current. The vehicle load 2B having a relatively large dark current is connected to both ends of the three high-capacity single cells 10a, and the vehicle load 2A includes the three high-capacity single cells 10a and one high-power single cell 10b. Connected to the whole.

  As described above, the high-capacity single cell 10a has a higher capacity than the high-power single cell 10b, and therefore has a capacity that can handle the dark current of the vehicle load 2B. On the other hand, the vehicle load 2A includes a load that has a small dark current but requires a high output (a large current) instantaneously. In this example, the vehicle load 2A is connected to both ends of four unit cells 10a and 10b having the same output. Therefore, the required high output can be accommodated.

  As described above, the load 2B having a large dark current is connected to the high-capacity single battery 10a, and the load 2A having a small dark current and a high output required includes the high-capacity single battery 10a and the high-power single battery 10b. Since it is connected to the whole, it is possible to cope with both the dark current of the load 2B and the high output of the load 2A, and at the same time, the assembled battery can be reduced in size, weight and cost.

  In the example shown in FIG. 5, the capacity adjustment circuit 3 is provided in the high-power single cell 10 b in addition to the example shown in FIG. 4. The capacity adjustment circuit 3 includes, for example, a voltage detection circuit that detects the voltage of the high-power single battery 10b and a discharge circuit that discharges the high-power single battery 10b, and has a remaining capacity (SOC) equal to that of the high-capacity single battery 10a. The high-power unit cell 10b is discharged so that As a result, even if the remaining capacity (SOC) of the high-capacity single cell 10a decreases while continuing to be used, even if a variation with the remaining capacity (SOC) of the high-power single cell 10b occurs, this capacity adjustment circuit Since the capacity can be made equal to 3, overdischarge and overcharge can be prevented, and the battery life can be extended.

  In the example shown in FIG. 6, the vehicle load 2 </ b> A is not always turned on, in other words, it is turned on only at a specific moment, such as a cell motor, that is, a load that selectively consumes power, and the dark current is zero. It is a load. Therefore, the vehicle load 2A is connected to the entire assembled battery 1, but is not always turned on. Therefore, the switch 4 is provided between the high-power single cell 10b and the high-capacity single cell 10a and only operates the vehicle load 2A. Switch 4 is turned on.

  On the other hand, the vehicle load 2B having a relatively large dark current is connected to the three high-capacity single cells 10a as in the examples shown in FIGS.

  In the example shown in FIG. 7, the charger 5 is connected to the high-power single cell 10b instead of the capacity adjustment circuit 3 shown in FIG. The charger 5 is, for example, a charger that is operated by the vehicle load 2B, and charges the high-power single cell 10b when the remaining capacity (SOC) of the high-power single cell 10b decreases. As a result, even if the remaining capacity (SOC) of the high-power single cell 10b decreases while the use continues, even if a variation with the remaining capacity (SOC) of the high-capacity single cell 10a occurs, the charger 5 Since the capacity can be made equal, overdischarge and overcharge can be prevented, and the battery life can be extended.

  The embodiment described above is described for facilitating the understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

It is a top view which shows the whole thin unit cell which concerns on embodiment of this invention. It is sectional drawing which follows the II-II line of FIG. (A) is a side view which shows the assembled battery which concerns on embodiment of this invention, (B) is a side view which shows the conventional assembled battery. It is an example of the electric circuit using the assembled battery which concerns on embodiment of this invention. It is another example of the electric circuit using the assembled battery which concerns on embodiment of this invention. It is a further another example of the electric circuit using the assembled battery which concerns on embodiment of this invention. It is a further another example of the electric circuit using the assembled battery which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Assembly battery 10 ... Thin battery 10a ... High capacity | capacitance single cell 10b ... High output single cell 101 ... Positive electrode plate 101a ... Positive electrode side collector 101b, 101c ... Positive electrode layer 102 ... Separator 103 ... Negative electrode plate 103a ... Negative electrode side current collector Body 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 2A, 2B ... Vehicle load

Claims (5)

In an assembled battery in which a plurality of cells are connected in series and a plurality of loads are connected,
The assembled battery connects a first group of cells formed by connecting a plurality of first cells and a plurality of second cells having a smaller capacity and a higher output density than the first cells. configured and second cell group which is formed by the connected in series,
The relatively large load than dark current in the other loads of the plurality of loads is connected only to the first cell group Rutotomoni,
The assembled battery, wherein a load having a relatively small dark current compared to other loads among the plurality of loads is connected to the entire first cell group and the second cell group . And wherein the power consumption during the driving of the plurality of load is relatively large load than the other load is connected to the entirety of the first cell group and the second cell group The assembled battery according to claim 1. In an assembled battery in which a plurality of cells are connected in series and a plurality of loads are connected,
The assembled battery connects a first group of cells formed by connecting a plurality of first cells and a plurality of second cells having a smaller capacity and a higher output density than the first cells. configured and second cell group which is formed by the connected in series,
A load that constantly consumes electric power among the plurality of loads is connected only to the first cell group ,
The assembled battery, wherein a load that consumes power only at a specific moment among the plurality of loads is connected to the entire first cell group and the second cell group . The assembled battery according to any one of claims 1 to 3 , wherein means for adjusting a battery capacity is provided in the second cell group. The assembled battery according to any one of claims 1 to 4 , wherein means for charging a battery is provided in the second cell group.

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