Battery block and battery module

A battery block includes a metal case including a side surface and a bottom surface, and a plurality of cells accommodated in the metal case, wherein each cell includes a first electrode and a second electrode which is electrically insulated from the first electrode, and also serves as a cell case of the cell, the plurality of cells are aligned with the first electrodes being in a same direction, the first electrodes of the plurality of cells are connected to a connector arranged to face an opening of the metal case, the second electrodes of the plurality of cells are connected to the bottom surface of the metal case, the height of the side surface of the metal case is substantially the same as the height of the cells, and the opening of the metal case is almost completely covered with the connector.

RELATED APPLICATIONS

This application is the U.S. National Phase under 35 U.S.C. §371 of International Application No. PCT/JP2011/02737, filed on May 17, 2011, which in turn claims the benefit of Japanese Application No. 2010-208899, filed on Sep. 17, 2010, the disclosures of which Applications are incorporated by reference herein.

TECHNICAL FIELD

The present invention relates to battery blocks including a plurality of cells connected to each other in parallel to output a large current, and to battery modules including the battery blocks.

BACKGROUND ART

In recent years, in view of savings in resources and conservation of energy, there have been increasing demands for nickel-hydrogen secondary batteries, lithium ion secondary batteries, etc. which can be used repeatedly. Among them, lithium ion secondary batteries are characterized by lightness in weight, high electromotive force, and high energy density. Thus, there are growing demands for the lithium ion secondary batteries as power sources for driving various kinds of portable electronic devices and mobile communication devices such as mobile phones, digital cameras, video cameras, and lap top computers.

On the other hand, to reduce used amount of fossil fuel, and to reduce the amount of emission of CO2, expectations for secondary batteries are growing to serve as power sources for driving motors such as vehicles.

A battery pack which is a set of such secondary batteries includes a plurality of batteries in order to obtain a preferable voltage and battery capacity, and has a configuration in which a plurality of battery blocks are provided, where each battery block includes the plurality of batteries connected to each other in parallel and/or in series. Such a battery block is described in, for example, Patent Document 1.

CITATION LIST

Patent Document

PATENT DOCUMENT 1: Japanese Translation of PCT International Application No. 2008-541386

SUMMARY OF THE INVENTION

Technical Problem

When a battery block including a plurality of batteries connected to each other in parallel is used as, for example, a power source for driving a motor of a vehicle, a large current flows through the batteries. Therefore, if electrical connection between the batteries is not ensured, no current may flow, or the resistance at a contact may increase, thereby generating heat, which inhibits flow of the large current. For this reason, not only bringing the batteries into contact with a connection member, but also ensuring good electrical connection by, for example, welding are required.

For example, when the connection member is connected to the batteries by welding, a welding method which can ensure high mechanical strength at welding sections has to be selected in view of materials, structures, and the like of negative electrode terminals (e.g., battery cases) and positive electrode terminals of the batteries and the connection member. In contrast, to reduce the electrical resistance of the connection member, the thickness and the width of the connection member have to be increased.

However, when the thickness and the width of the connection member are increased, the connection member occupies spatially large volume, so that the size and/or the weight of the battery block may be increased. In particular, when the battery block is used as a power source for driving a motor of a vehicle, the battery block has to be light in weight and small in size in order to extend the range. Thus, heavy big battery blocks have no commercial value.

In view of the foregoing, the present invention was devised. It is an objective of the invention to provide a battery block including a plurality of batteries connected to each other in parallel, wherein electrical resistance is small, and power loss is small even when a large current flows through the batteries.

Solution to the Problem

To solve the problems discussed above, an example battery block of the present invention includes: a metal case including a side surface and a bottom surface; and a plurality of cells accommodated in the metal case, wherein each cell includes a first electrode and a second electrode which is electrically insulated from the first electrode, and also serves as a cell case of the cell, the plurality of cells are aligned with the first electrodes being in a same direction, the first electrodes of the plurality of cells are connected to a connector arranged to face an opening of the metal case, the second electrodes of the plurality of cells are connected to the bottom surface of the metal case, a height of the side surface of the metal case is substantially the same as a height of the cells, and the opening of the metal case is almost completely covered with the connector.

With this configuration, a current from the second electrode (cell case) can be output to the metal case having a large cross-sectional area, so that it is possible to obtain a battery block having a large cross-sectional area and having small electrical resistance.

Advantages of the Invention

According to the present invention, it is possible to provide a battery block including a plurality of batteries connected to each other in parallel, wherein the electrical resistance is small, and power loss is small even when a large current flows through the batteries.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention will be described in detail below with reference to the drawings. In the drawings to follow, like reference numbers are used to designate elements having substantially the same function for the sake of brevity. The present invention is not limited to the embodiments below.

FIGS. 1A,1B are views illustrating a configuration of a battery module10of an embodiment of the present invention, whereFIG. 1Ais a perspective view, andFIG. 1Bis a transparent view of the housing ofFIG. 1A.

As illustrated inFIG. 1B, the battery module10includes a set of six battery blocks100, wherein three battery blocks100aligned in parallel are aligned to face the other three battery blocks100aligned in parallel, and the thus aligned six battery blocks100are accommodated in an insulating housing300. The six battery blocks100are electrically connected to each other in series, an output of the battery module10is output outside the housing300via a positive electrode output terminal400, and a negative electrode output terminal500.

FIG. 2is an exploded view illustrating the battery module10of the present embodiment disassembled into components.

As illustrated inFIG. 2, the three battery blocks100are connected to each other such that a connection terminal (not shown) of a first electrode (positive electrode) of a battery block100is connected to a connection terminal (not shown) of a second electrode (negative electrode) of an adjacent battery block100. Ends of groups each of which includes the three battery blocks100, and which face each other are connected to each other via a connection member200. The thus connected six battery blocks100are accommodated in a lower case310of the housing300, and sealed with a lid320. Output terminal openings311are formed in the lower case310. The positive electrode output terminal400connected to the connection terminals of the positive electrodes of the battery blocks100and the negative electrode output terminal500connected to the connection terminals of the negative electrodes of the battery blocks100are placed in the output terminal openings311.

FIG. 3is a perspective view schematically illustrating a configuration of the battery block100of the present embodiment.FIG. 4is an exploded view illustrating the battery block disassembled into components.

As illustrated inFIGS. 3,4, the battery block100includes a plurality of cells110which are aligned with their positive electrodes being in the same direction, and are accommodated in a metal case120having a side surface122and a bottom surface123. In the example illustrated inFIGS. 3,4, fourteen cells110are aligned in a hexagonal lattice configuration with three rows which include five cells, four cells, and five cells, respectively.

Each cell110is a cylindrical secondary battery including a power-generating element accommodated in a cell case. Each cell110includes a positive electrode, and a negative electrode which is electrically insulated from the positive electrode, and also serves as the cell case of the cell110.

The positive electrodes of the cells110are connected to a plate-like connector130arranged to face an opening of the metal case120via positive electrode lead plates132. Note that in the connector130, round holes133are formed at positions facing the positive electrodes of the cells110. In areas where the round holes133are formed, the positive electrode lead plates132can be welded to the positive electrodes of the cells110. Moreover, the negative electrodes (bottom surfaces of the cell cases) of the plurality of cells110are connected to the bottom surface123of the metal case120. In this way, the plurality of cells110are electrically connected to each other in parallel.

With this configuration, a current from the negative electrode (cell case) can be output to the metal case120having a large cross-sectional area, so that it is possible to obtain a battery block100having small electrical resistance.

Here, the height of the side surface122of the metal case120is substantially the same as the height of the cells110, and the opening of the metal case120is almost completely covered with the connector130. With this configuration, the metal case120and the connector130substantially form the housing of the battery block100, and protect the cells110accommodated in the battery block100.

A shoulder portion of the cell case close to the positive electrode of each cell110is provided with an insulating spacer112. Since the spacer112is provided between the cell case and the connector130, short-circuiting between the positive electrode (connector130) and the negative electrode (cell case) is prevented.

Moreover, the plurality of cells110are held by an insulating holder140accommodated in the metal case120. The holder140includes a holding section141in which a plurality of cylinder portions are integrally formed. Outer side surfaces of the cells110are brought into contact with inner side surfaces of the cylinder portions of the holding section141, so that the cells110are fixed by the holder140. Note that the holder140holds the cells110, and prevents short-circuiting between the positive electrode (connector130) and the negative electrode (metal case120).

Moreover, the holder140further includes fixing sections142extending along the side surface122of the metal case120. The holder140is fixed to the bottom surface of the metal case120at one end of each fixing section142by a screw150b. On the other hand, at the other end of each fixing section142, the holder140is fixed to the connector130by a screw150a.

Here, when the spacer112provided between the cell case of each cell110and the connector130is made of an elastic material (e.g., silicon lubber), the spacer112can serve as a cushion in fixing the cell110to the metal case120via the holder140. In this way, for example, fixing the cells110can be ensured even when the cells110have a length tolerance and variations of their arrangement. Moreover, it is possible to alleviate vibration applied to the battery block100.

FIG. 5Ais a cross-sectional view taken along the line A-A ofFIG. 3.FIG. 5Bis an enlarged view illustrating a part indicated by the arrow B ofFIG. 5A.

As illustrated inFIG. 5A, the connector130includes a positive electrode connection terminal (positive electrode external terminal)131outwardly extending beyond the side surface122of the metal case120. The side surface122of the metal case120includes a negative electrode connection terminal (negative electrode external terminal)121at an end portion of the opening of the metal case120(at a side of the metal case120facing the connector130). The negative electrode connection terminal121is outwardly bent to extend beyond the side surface122of the metal case120. The positive electrode connection terminal131and the negative electrode connection terminal121are located at positions opposite to each other.

When the positive electrode connection terminal131and the negative electrode connection terminal121are provided in such positions, a plurality of battery blocks100aligned to configure a battery module can be easily connected to each other in series by bringing the positive electrode connection terminal131of a battery block100into contact with the negative electrode connection terminal of an adjacent battery block100as illustrated inFIG. 6.

Note that the positive electrode connection terminal131is not necessarily formed by outwardly extending the connector130beyond the side surface122of the metal case120, but the connector130may extend in the periphery of the side surface122of the metal case120to such a position at which the connector130can be brought into contact with the negative electrode connection terminal121of the adjacent battery bock100.

Moreover, as illustrated inFIG. 5B, a shoulder portion161of the cell case close to a positive electrode160of each cell110is provided with the insulating spacer112. Since the spacer112is provided between the cell case and the connector130, short-circuiting between the connector (positive electrode)130and the cell case (negative electrode) is prevented.

Moreover, as illustrated inFIGS. 4,5B, the outer side surfaces of the cell cases of the cells110are covered with cylindrical heat transfer members111. Adjacent ones of the cells110are aligned such that their heat transfer members111are in contact with each other, and outer ones of the cells110are aligned such that their heat transfer members111are in contact with the side surface of the metal case120. With this configuration, heat generated in any one of the cells110is transferred to the adjacent cells110, and is further transferred via the outer cells110to the metal case120. Thus, the heat can be efficiently released. As the heat transfer member111, a metal member is preferably used, examples of which include aluminum (thermal conductivity 236 W/(m·K)), silver (thermal conductivity 420 W/(m·K)), copper (thermal conductivity 398 W/(m·K)), gold (thermal conductivity 320 W/(m·K)), and the like.

Note that the spacer112and the holder140are individually formed in the present embodiment, but the spacer112and the holder140may be integrally formed. In this case, when the spacer112and the holder140are integrally made of an elastic member, vibration applied to the battery block100can be further alleviated.

FIG. 7is a perspective view of the metal case120of the battery block100of the present embodiment.

As illustrated inFIG. 7, the metal case120includes the bottom surface123which is in contact with the cells110, and the four-face side surface122having a height substantially equal to the height of the cells100. The thickness of the metal case120is preferably larger than or equal to 1 mm in order to increase the cross-sectional area through which currents from the plurality of cells110flow. With this configuration, the area of the four-face side surface122is a conduction path of a current, and thus the electrical resistance can be small even when a large current flows. Therefore, heat generated at the metal case120is small, and power loss caused by the heat generation can be significantly reduced.

Moreover, the bottom surface123of the metal case120has a small thickness in areas124with which the bottom surfaces of the cell cases of the cells110are in contact. For example, the areas124can be recessed sections each of which has a size substantially equal to the contour size of the cell110. Here, it is preferable that the thickness of the areas (recessed sections)124be substantially the same as the thickness of the cell case of the cell110(e.g., 0.2 mm-0.3 mm). With this configuration, the cells110can be easily welded to the metal case120by laser welding. Moreover, the bottom surface123of the metal case120is provided with screw holes125in order to fix the metal case120to the fixing sections142of the holder140by the screws150b

FIG. 8is a view schematically illustrating the cell110of the present embodiment.

As illustrated inFIG. 8, the cell110is surrounded by the heat transfer member111made of an aluminum pipe having a height substantially equal to the height of the cell110. The spacer112made of silicon rubber is provided on a side close to the positive electrode160of the cell110.

FIG. 9is a perspective view illustrating an example of an alignment of the plurality of cells110included in the battery block100.

As illustrated inFIG. 9, fourteen cells110are aligned in a hexagonal lattice configuration with three rows which include five cells, four cells, and five cells, respectively. Adjacent ones of the cells110are aligned such that their heat transfer members111are in contact with each other. When the plurality of cells110aligned in this way are accommodated in the metal case120, the heat transfer members111of outer ones of the cells110are in contact with the side surface of the metal case120. Thus, heat generated in any one of the cells110is transferred to the adjacent cells110, and is further transferred via the outer cells110to the metal case120. Therefore, the heat can be efficiently released.

FIG. 10is a perspective view illustrating a variation of the metal case120ofFIG. 7.

As illustrated inFIG. 10, a metal case120bof the present variation includes semicircular recessed sections124and semicircular holes126. With this configuration, an electrode for resistance welding can be brought into contact with cell cases of cells110through the holes126. Thus, connection can be further ensured by performing the resistance welding of the cell cases to the metal case120b.

FIG. 11is a perspective view illustrating another variation of the metal case120ofFIG. 7.

As illustrated in11, a metal case120cof the present variation includes circular holes127formed in a surface in contact with negative electrodes (cell cases) of cells110, and negative electrode lead plates128having a thickness of 0.2 mm-0.3 mm are provided in the circular holes127. In this case, as illustrated inFIG. 12, fourteen circular holes127are formed in the metal case120c, and the negative electrode lead plates128are arranged on the surface in contact with the cells110. With this configuration, connection can be further ensured by performing the resistance welding with an electrode being in contact with the cell cases of the cells110and the negative electrode lead plates128. Here, when the negative electrode lead plates128and the metal case120care individual members, suitable types of metal can be selected for the negative electrode lead plates128and the metal case120c, and for example, nickel having good weldability may be selected for the negative electrode lead plates128, and aluminum having good heat dissipation characteristics may be selected for the metal case120c. Moreover, as the negative electrode lead plates128, a two-layer clad plate made of nickel and aluminum may be selected.

FIGS. 13A,13B,13C are views illustrating still another variation of the metal case120ofFIG. 7, whereFIG. 13Ais a perspective view illustrating an alignment of cells110,FIG. 13Bis a perspective view illustrating a metal case120d, andFIG. 13Cis a plan view illustrating the metal case120din which the cells110are accommodated.

As illustrated inFIGS. 13B,13C, the metal case120dof the present variation includes a side surface122formed along outer side surfaces of cell cases of the cells110. With this configuration, the entirety of the side surface122of the metal case120dis in contact with the outer side surfaces of the cell cases of the cells110arranged outside. Thus, heat generated in the cell110can be further efficiently transferred to the metal case120.

Although the present invention has been described above with reference to the preferable embodiments, the description is not intended to limit the invention, and of course, various modifications can be made. For example, in the above embodiment, the positive electrodes of the cells110are connected to the connector130, and the negative electrodes (cell cases) of the cells are connected to the bottom surface of the metal case120. However, the negative electrodes of the cells110may be connected to the connector130, and the positive electrodes (cell cases) of the cells may be connected to the bottom surface of the metal case120. Note that in this case, the cell cases of the cells110also serve as positive electrodes. Although the metal case120is rectangular in the above embodiment, the shape of the side surface122may be a polygon such as a hexagon, a circle, an ellipse, or the like when viewed from above.

INDUSTRIAL APPLICABILITY

The battery block of the present invention is useful to power sources having large electric capacitance capable of discharging a large current.

DESCRIPTION OF REFERENCE CHARACTERS