HK1131470A - Prismatic battery with novel inter-cell connection - Google Patents

Description

Square battery pack with novel inter-battery connection

Technical Field

The present invention relates to a prismatic battery (prismatic batteries), and more particularly, to a prismatic battery including a plurality of prismatic battery cells (prismatic batteries). More particularly, and certainly not exclusively, the invention relates to a rechargeable battery pack having prismatic cells.

Background

Batteries (batteries) and battery cells (battery cells) having a prismatic shape are generally referred to as prismatic batteries and prismatic battery cells, respectively. Although most prismatic batteries and battery cells have a rectangular or circular cross-section, prismatic batteries may be any suitable prismatic shape without loss of generality.

Prismatic batteries or battery modules are generally constructed of a plurality of prismatic batteries. Each cell is formed from an electrode plate group including a positive cell plate group and a negative cell plate group. Typically, each cell plate group includes a plurality of electrode plates stacked in parallel. The same-polarity electrode plates are electrically connected together along the lateral sides to be connected to the current collector, and the different-polarity electrode plates are alternately stacked. A typical current collector comprises an elongated metal member, such as a metal rod, that extends along the entire length of the electrode plate. This differs from a cylindrical battery cell in that the electrode plates are spirally wound or spirally wound into an electrode plate group. The positive and negative electrode cell plate groups are connected to positive and negative current collectors, respectively.

In general, the term "prismatic battery cell" (prismatic battery cell) is understood by those skilled in the art as a battery cell comprising a plurality of positive and negative electrode plates stacked in parallel with a separator between an adjacent pair of positive and negative electrode plates. Each battery cell is then connected to the adjacent cell via a current collector as a connector. Then, the battery assembly including the electrode plate groups and the positive and negative current collectors is sealed in a prismatic case to prevent leakage of electrolyte, and the packaged battery cell has a prismatic shape as a whole, and thus is referred to as a "prismatic battery cell".

Prismatic batteries typically include a plurality of prismatic battery cells connected or bundled (bundled) together in parallel and/or series. The plurality of prismatic cells are typically mounted in a molded plastic housing comprising a plurality of cell compartments, wherein adjacent cell compartments are separated by partition walls. The battery pack has a prismatic shape as a whole, and is thus generally referred to by the term "square".

In this specification, the term "prismatic battery cell" is used to generically refer to a type of battery and is not intended to be bound or limited to the exact prismatic battery cell. More specifically, the term is used to describe a battery cell having positive and negative electrode plate groups, wherein each of the electrode plate groups comprises a plurality of electrode plates stacked in parallel. Typically, the electrode plates of an electrode plate group of a certain polarity are electrically connected together along a lateral side and electrically bundled (bound) on the other, opposite side. The other side is normally held in place by being clamped by the electrode plates of the opposite plate set. The positive electrode plates and the negative electrode plates of the electrode plate groups of the battery cells are alternately stacked with respect to each other such that the electrode plates of one electrode plate group are sandwiched between a pair of electrode plates of the electrode plate group having opposite polarities except for the outermost electrode plate. A separator is disposed between an adjacent pair of positive and negative electrode plates in a manner generally known to those skilled in the art or as desired. It should be understood that while it is common for prismatic battery cells to have rectangular electrode plates, the electrode plates need not, and need not, be rectangular.

Batteries with prismatic cells are used in most high current applications or applications where high power density is required. For example, a rechargeable prismatic battery pack, such as a nickel metal hydride (NiMH) battery pack, has been widely used as a power source to drive Electric Vehicles (EV) or Hybrid Electric Vehicles (HEV), because of its excellent energy density characteristics.

Generally, in the example of a NiMH battery, electrical energy is generated by a chemical reaction between a positive electrode plate set and a negative electrode plate set in the presence of a liquid or fluid electrolyte, such as potassium hydroxide (KOH). The electrical energy thus generated is first delivered to the load via the current collector and then through the connection terminal. In order to meet the rated power requirements, a plurality of battery cells are typically connected together to form a battery unit or a battery module. The battery cells are usually connected together by bonding or welding the corresponding free upper and/or lower ends of the current collectors of adjacent electrode plate groups. It is well known that the contact resistance between adjacent battery cells is a major internal source of impedance for the battery. High internal impedance means high power consumption and heat dissipation problems. Such energy consumption and heat generation are particularly undesirable for high current applications such as electric vehicles or hybrid electric vehicles because the efficiency of the battery pack can be adversely affected and the internal heat so generated needs to be dissipated to avoid premature failure due to overheating or damage to the battery.

In the conventional prismatic battery shown in fig. 1, the inter-cell connection is generally formed by resistance welding a pair of counterpart connectors, which are respectively disposed in their respective battery cells and are respectively connected to the current collectors of the corresponding electrode cell plate groups. A typical mating inter-cell connector comprises a rigid metal plate on which indentations are formed, for example by stamping, of a size comparable to or smaller than the size of the inter-cell aperture. The indentation on one side of the metal plate protrudes as a convex cap on the other side. The depth of the indentation or height of the raised cap is such that when a pair of mating connectors are welded together, the two mating connectors, together with a pair of O-rings, form an inter-cell connection for a pair of adjacent cells, while sealing the inter-cell aperture. The formation of a skirt between the raised cap and the base of the metal plate creates a region of progressively increasing resistance in the inter-cell connection path. Furthermore, it is known that the welding between the opposing surfaces of the two raised caps of the counterpart connector causes additional resistance and it is difficult to ensure the quality of the welding at the junction. Furthermore, high temperature welding of the raised caps may damage or permanently deform the sealing rings. Furthermore, it is also desirable that each cell compartment be sealed, as it is known that electrolyte flow through the cells can shorten the life of the battery.

It is therefore desirable to provide prismatic batteries having improved inter-cell connections to eliminate the drawbacks of conventional prismatic batteries.

Disclosure of Invention

According to the present invention there is provided a battery comprising a plurality of interconnected prismatic battery cells, wherein an adjacent pair of prismatic battery cells are connected by at least one inter-cell connector, each said inter-cell connector comprising an inter-cell conductive portion extending through an inter-cell aperture between said adjacent pair of prismatic battery cells, the battery being characterised in that the physical properties of said inter-cell connector across (across) said inter-cell aperture are continuous or substantially continuous.

The physical properties may include, for example, conductivity (conductivity), conductance (conductivity), conductive area (conductive area), conductive shape (conductive shape), resistance (resistance), resistivity (resistance), and/or metal particle properties (metallic particle properties) of the conductor, and/or other physical properties related to current conduction between cells.

For example, the conductivity and/or conductance of the inter-cell connector across the inter-cell aperture may be constant or substantially constant.

For example, the conductivity or conductance of the inter-cell connector across the inter-cell aperture may be constant or substantially constant.

As another example, the conductivity or resistivity of the inter-cell connector across the inter-cell aperture is uniform or substantially uniform.

The physical properties of the inter-cell conductor across the inter-cell aperture are substantially continuous, which generally means that the physical properties of the inter-cell conductor across the inter-cell aperture are not abrupt. Typically, this is the criterion for the minimum resistance or maximum conductance of the optimal inter-cell connection.

Furthermore, the use of a conductor that is physically substantially continuous across the inter-cell aperture also means that the conductive area or conductive cross-section is substantially continuous across the inter-cell aperture.

According to one aspect of the present invention, there is provided a battery comprising a plurality of prismatic battery cells, wherein prismatic battery cells immediately adjacent to each other are connected by at least one inter-cell connector extending through an inter-cell aperture through which said adjacent prismatic battery cells communicate; the battery is characterized by a continuous electrical conductivity and/or a continuous electrical conductance across said inter-cell aperture.

Because the resistance of the inter-cell connector is determined in large part by the maximum impedance of the inter-cell connector in the inter-cell circuit due to the series nature of the inter-cell connector, an inter-cell connector comprising an inter-cell conductor of constant or substantially constant resistance and/or resistivity across the inter-cell aperture means that the conductivity of the inter-cell connector is not determined by the resistance or resistivity of a stepped contact such as a raised peripheral skirt or a welded contact between opposing raised caps of a conventional inter-cell connection.

In another aspect of the invention, there is provided a battery comprising a plurality of prismatic battery cells, wherein prismatic battery cells immediately adjacent to each other are connected by at least one inter-cell connector extending through an inter-cell aperture through which said adjacent prismatic battery cells communicate; the battery is characterized in that said inter-cell connector is continuous across the conductive area of said inter-cell aperture.

An inter-cell connector that has a constant or substantially constant conductance and/or conductive area across the inter-cell aperture means that an adjacent pair of prismatic battery cells can be connected by an inter-cell connector having the optimum or maximum possible conductivity relative to the size of the inter-cell aperture. Thus, the inter-cell aperture of a battery pack having a relatively large current rating may be relatively small.

For example, the conductive area of the inter-cell connector may be constant or substantially constant across the inter-cell aperture.

In an exemplary embodiment, the battery pack may include a case having a plurality of cell compartments for accommodating the plurality of prismatic cells such that one of the prismatic cells is accommodated in one of the cell compartments, adjacent ones of the prismatic cells being connected by at least one of the inter-cell connectors extending through a partition wall partitioning adjacent ones of the cell compartments through one of the inter-cell apertures through which the cell compartments accommodating the adjacent ones of the prismatic cells communicate.

At least the portion of the inter-cell connector extending through the inter-cell aperture may be integrally formed or formed as a single piece.

When using integrally formed conductors as bridging portions of an inter-cell connector, there is no need to deform the current collectors to form raised caps by metal stamping, for example, in preparation for inter-cell welding in a conventional manner. An undeformed or integrally formed conductor for an inter-cell connector would significantly eliminate the drawbacks of conventional forming of raised caps for forming inter-cell connections, since deforming the current collector would necessarily change the physical properties of the current collector, such as thinning the current collector in the skirt region and/or damaging the protective layer (e.g., nickel coating).

The portion of the inter-cell connector extending through the inter-cell aperture may form a fluid seal preventing leakage of electrolyte through the inter-cell aperture.

At least the portion of the inter-cell connector extending through the inter-cell aperture is tapered and may also be configured as a fluid seal to prevent leakage of electrolyte through the inter-cell aperture.

At least the portion of the inter-cell connector extending through the inter-cell aperture is tapered, and the inter-cell connector may be configured such that one longitudinal end of the inter-cell connector is insertable into the inter-cell aperture, while the other longitudinal end has a transverse cross-section configured to seal the inter-cell aperture.

Each of the prismatic cells may include an electrode plate group having a positive current collector and a negative current collector, and the corresponding current collectors of an adjacent pair of prismatic cells are connected by at least one of the inter-cell connectors.

Conductance of said inter-cell connector across said inter-cell aperture is at a maximum in terms of the size of said inter-cell aperture.

End flanges may be formed at respective longitudinal ends of the inter-cell connectors so as to cover the inter-cell aperture.

The inter-cell aperture may be formed in a dividing wall separating two adjacent cell compartments, the flange being in compressive engagement with the dividing wall.

The inter-cell conductor may include first and second ends located in different cell compartments, and immediately adjacent prismatic battery cells are joined at the first and second ends.

An adjacent pair of prismatic battery cells may be connected using at least one inter-cell connector by forming contacts outside the inter-cell aperture.

Each of the contacts is formed by welding, soldering or other fusing methods.

Electrical connection between an adjacent pair of prismatic cells and an inter-cell connector may be made by forming contacts at opposite ends of the inter-cell connector such that portions of the inter-cell connector between the contacts are not welded.

Each of the inter-cell connectors may include a fastener for fastening (fastened) and sealing (righted) the inter-cell connector to a cell compartment wall.

A circumferential flange may be formed at a longitudinal end of the inter-cell connector, the other longitudinal end of the inter-cell connector having threads for receiving threaded fasteners, the inter-cell connector being sealed to the cell compartment wall by cooperation with the circumferential flange and the threaded fasteners.

The threaded fastener may comprise a threaded fastening nut.

The inter-cell connector may taper towards a longitudinal end away from the flange, the inter-cell connector being dimensioned such that a distal end of the inter-cell connector is insertable into the inter-cell aperture, and wherein the cell dividing wall is interposed between the distal end and the flange end of the inter-cell connector when the inter-cell connector is fastened and sealed to the cell dividing wall.

The current collector of the prismatic battery cell has a C-shaped cross-section, and the inter-cell connector is coupled to the current collector at the middle of the C-shaped cross-section.

The battery may be a nickel metal hydride battery with a potassium hydroxide electrolyte.

An adjacent pair of prismatic battery cells may be joined by a plurality of said inter-cell connectors at a plurality of locations distributed along the length of the respective pair of current collectors.

According to the present invention, there is also described a method of forming an inter-cell connection between a pair of adjacent prismatic battery cells of a battery, the method comprising:

a. attaching and securing an inter-cell connector to the cell partition wall; and

b. the inter-cell connector is connected to the current collectors of an adjacent pair of prismatic battery cells.

The method may further comprise the step of forming an electrically conductive contact between said inter-cell connector and said current collectors of an adjacent pair of prismatic battery cells outside the inter-cell aperture.

In applications, the inter-cell connector may comprise an inter-connector (inter-connector) having opposite ends, and the method further comprises forming a pair of electrically conductive contacts between an adjacent pair of prismatic battery cells at the opposite ends.

Drawings

Preferred embodiments of the invention will now be described in more detail, by way of example, with reference to the accompanying drawings, in which:

fig. 1 is a perspective view showing a particularly exploded and partially disassembled view of a prismatic battery pack having conventional inter-cell connections;

FIG. 1A is an enlarged cross-sectional view of the inter-cell connection of FIG. 1;

FIG. 2 shows an exploded view of a molded battery housing showing the inter-cell connectors of the present invention disassembled;

FIG. 2A is an enlarged cross-sectional view of the inter-cell connection of FIG. 2 formed in part;

FIG. 2B is an exploded view of the inter-cell connector;

FIG. 2C shows a cross-sectional view of an alternative preferred embodiment of an inter-cell connector;

FIG. 3 shows an exploded view of a partially disassembled battery pack showing the inter-cell connectors of the present invention;

FIG. 3A is an enlarged cross-sectional view showing the connection between the batteries of FIG. 3;

fig. 3B is an enlarged perspective view showing the area on the current collector corresponding to the conductive contact.

Detailed Description

In the following description, although specific reference is made to nickel metal hydride batteries as a convenient exemplary embodiment, since nickel metal hydride (NiMH) rechargeable batteries are widely used and known to have excellent power density characteristics, reasonable price, and appropriate battery life, those skilled in the art will understand that the principles and inventions described in the present specification can be applied to other types of prismatic batteries, particularly rechargeable prismatic batteries including battery cells having electrode plates stacked in parallel, with appropriate modifications, without loss of generality.

A typical prismatic battery or prismatic battery module 10 shown in fig. 1 comprises a plurality of prismatic battery cells 100, which prismatic battery cells 100 are connected together, for example to meet appropriate power rating requirements. Each battery cell 100 includes an electrode plate group 110, and the electrode plate group 110 includes a positive electrode plate group and a negative electrode plate group. Each electrode plate group comprises a plurality of electrode plates, and the positive electrode plate group and the negative electrode plate group together form an electrode plate group of the square battery. Positive and negative electrode plates from the positive electrode plate group and the negative electrode plate group, respectively, are alternately stacked in parallel with a separator interposed between an adjacent pair of the electrode plates. Thus, the electrode plate groups of the prismatic battery cell include a positive electrode plate group and a negative electrode plate group 110 separated by a separator (not shown). More specifically, the electrode plate groups are arranged such that positive electrode plates and negative electrode plates are alternately arranged with separators interposed between each pair of positive and negative electrode plates. The corresponding longitudinal edges of the positive electrode plates on one side of the positive electrode plate group are connected along their length and then to the positive current collector. The corresponding longitudinal edges of the negative electrode plates of the negative electrode plate group, which are located opposite to the connected longitudinal edges of the positive electrode plate group, are connected along their length and then connected together to a negative current collector. Each electrode plate includes an active region and a lead region. The corresponding active areas of a pair of positive and negative plates substantially overlap and interact in the presence of an electrolyte to convert chemical energy into electrical energy. The active area of the electrode plates of a typical prismatic battery cell is substantially rectangular with one long or longitudinal side adjacent to the lead portion. The lead portion is located on one lateral side of the electrode plate, is elongated, and is substantially the same length as the longitudinal side of the active region. The rectangular active areas of the electrode plates are typically formed from the same base material. The active area and the lead portion have substantially the same length. Of course, the lead portion may be shorter or longer. Further, it should be understood that while the workspace is generally rectangular, it is not absolutely required and that other shaped workspaces may be used without loss of generality.

In a typical conventional nickel-metal hydride rechargeable battery, the working area of the positive electrode plate is made of nickel-foamed metal (nickel-metal) coated with nickel hydroxide (nickel hydroxide). The active region of the negative electrode plate is made of a nickel stamped metal plate coated with a negative electrode constituent material, such as a hydrogen-absorbing alloy (hydrogen-absorbing alloy). Since the electrogenic reaction is essentially performed on the surface, the electrode plates are typically very thin to reduce material cost and weight. Current collector 120 is typically nickel plated copper or steel for good thermal and electrical conductivity. For prismatic battery cells in which the electrode plates are connected to the current collector by electron beam welding, resistance welding or carbon dioxide laser welding, the current collector is typically a thin nickel-plated metal plate, since the actual welding point is located behind the near-surface of the welding source.

In forming the electrode plate group 110, the corresponding lead portions of the electrode plates are first bundled together. Bundling in this context includes, but is not limited to, pressing, packaging, gathering, welding or fastening together the individual lead portions of the electrode plate groups. The bundled lead portions may then be held in shape by brazing, welding, or mechanical fastening devices such as rivets. Furthermore, the electrode plate groups are typically already in a staggered configuration with adjacent electrode plates of different polarity in a close packed relationship before the lead portions are bundled together.

After the electrode plates are bundled together, they are sub-assembled with the current collector. This subassembly (sub-assembly) is then inserted into the prismatic battery housing 140, and adjacent battery cells 110 are connected together by inter-cell connections to form a battery or battery module when filled with electrolyte.

To make the inter-cell electrical connection, the current collector was processed so that an annular indentation with a rising cap was formed in the middle. The raised caps of the respective pairs of adjacent current collectors are welded together to form the inter-cell electrical connection, while the annular portions are fitted with O-rings 122 for inter-cell sealing. The raised cap is shaped and dimensioned to be received within the inter-cell aperture 136 and to form a weld within the inter-cell aperture 136.

Referring to fig. 2, 2A, 3 and 3A, an exemplary prismatic battery 20 of the present invention includes a plurality of battery cells 200 connected together. Each battery cell includes an electrode plate group 210 having a positive current collector 220 and a negative current collector 220 on opposite sides. The electrode plate group 210 is the same as the conventional electrode plate group 110 described above. Each electrode plate group 210 is inserted into the cell compartment 230 of the battery housing 240 such that each cell plate group is spaced apart from each other, and adjacent cell plate groups are electrically connected via respective current collectors 220 by inter-cell connectors 270.

The battery pack housing 240 is molded, for example, from a hard plastic or resin, and is preformed with a plurality of battery compartments 230 having a plurality of partition walls 232 separating adjacent battery compartments. As shown more particularly in fig. 2, each cell compartment 230 is generally rectangular, with generally rectangular partition walls 232 defining the lateral boundaries of each cell compartment. In other words, the housing 240 is generally rectangular, comprising a plurality of rectangular battery compartments with parallel partition walls 232. The bottom end of each cell compartment is open or partially open with an opening 234 adjacent each partition wall to facilitate welding or brazing between the inter-cell connectors and the current collectors as described below. The upper end of the battery compartment is completely open and covered by the top cover after the assembly is completed. An inter-cell hole 236 is formed near the upper and lower ends of the partition wall 232 to provide a guide path for inter-cell connection between a pair of adjacent prismatic battery cells as described below.

Referring to fig. 2 and 2A, an inter-cell connector for forming an inter-cell connection between an adjacent pair of prismatic battery cells is shown in more detail. The inter-cell connector 270 includes a first portion and a second portion that together form a conductive fastening means for forming an inter-cell electrical connection. The first part of the inter-cell connector comprises a headed inter-cell conductor having a solid conductive portion 272 extending from a flanged end 274 with the free end thereof furthest from the flanged end. The solid conductive portion is substantially a conductive shaft having a cross-section comparable to or slightly larger than the cross-section of the inter-cell aperture 236 such that the inter-cell aperture is filled or substantially filled by the solid conductive portion after the inter-cell connection is made. For example, the solid conductive portion may have a circular cross-section for a circular inter-cell aperture. The first portion of the inter-cell connector has a T-shaped longitudinal cross-section as shown in fig. 2A, corresponding to the inter-cell aperture having a cylindrical cross-section. The second portion of the inter-cell connector includes a locking nut 276 for securing the first portion of the inter-cell connector to the dividing wall 232. The free end 278 of the first portion of the inter-cell connector has threads (e.g., external threads) for coupling to couple with internal threads on the locking nut to form a complete electrically conductive fastening means through the separation wall 232. To enhance the inter-cell seal, a sealing member, such as an O-ring 280, is interposed between the locking nut 276, the dividing wall 232, and the portion of the conductive shaft of the first section that just protrudes from the dividing wall, thereby forming a fluid-tight seal around the inter-cell aperture 236 at the juncture where the solid conductive shaft of the first section protrudes from the dividing wall 232. The first portion may be a single piece of metal made of, for example, copper alloy, nickel plated copper, nickel plated steel, or other electrically conductive material. The locking nut may be made of a similar conductive or non-conductive substance, as its main task is to securely fasten the first part to the separation wall 232. The seal ring may be a rubber, silicon or other polymer seal ring.

First, the inter-cell connector 270 is inserted over the inter-cell aperture 236 and then secured to the dividing wall 232 by the lock nut 276, thereby forming an electrically conductive inter-cell conductive path between an adjacent pair of cell compartments. After the inter-cell conductive paths are formed, the electrode plate groups 210 are inserted into the cell compartments 230.

As shown in fig. 3, 3A and 3B, each electrode plate group 210 includes a pair of current collectors 220 arranged on opposite lateral sides, with the free ends of the current collectors 220 protruding over the longitudinal ends of the electrode plate group. In this particular embodiment, each current collector protrudes beyond the longitudinal ends of the electrode plate groups, so that an inter-cell connection can be made at both the upper and lower ends of the current collector. The current collector may extend beyond only one longitudinal end, e.g., the upper or lower end, if only a single inter-cell connector is required between an adjacent pair of battery cells.

In the preferred embodiment shown in fig. 2B, the solid conductive shaft 272 of the first portion is tapered toward its free end 278 so that the solid conductive shaft can additionally operate as an inter-cell plug, blocking the inter-cell hole with increased tightness as the inter-cell connector is tightened through the dividing wall.

After the inter-cell connectors 270 are assembled to the pack case by fastening to the inter-cell partition walls, the electrode plate groups 210 are placed in the cell compartments. The set of battery plates 210 is arranged and configured such that a pair of current collectors on both lateral sides of the set of motor plates will be in close proximity or in actual frictional contact with corresponding inter-cell connectors of adjacent battery cells when the set of electrode plates is in place in a cell compartment, or with a terminal connector when the set of electrode plates is in the first or last cell compartment. In other words, the separation between the free outer surfaces of the pair of current collectors 220 on the lateral sides of the electrode plate group is substantially the same as the separation between the free ends of the pair of opposing inter-cell connectors on the opposing partition walls of the intermediate cells.

In this preferred embodiment, the current collector has a C-shaped cross-section forming longitudinal channel ends along its length. The longitudinal channels are configured such that when the electrode plate groups are inserted into the cell compartments with the channel openings aligned with the flange heads of a pair of opposing inter-cell connectors on the partition walls, the electrode plate groups are guided into position by the flange ends aligned with the protruding ends of the current collectors. The current collector may be made of, for example, copper alloy, nickel-plated copper, nickel-plated steel, or other conductive materials such as alloys, as compared to conventional current collectors. A further advantage of using a current collector with a C-shaped cross-section is that the lead portions of the electrode plate groups can be attached to both sides of the current collector as shown in fig. 3.

After the electrode plate groups are inserted into the cell compartments as shown in fig. 3, inter-cell connections will be made. The inter-cell connection is formed by bonding an inter-cell connector to an adjacent pair of prismatic battery cells, for example, by a welding method such as brazing, or a welding method such as resistance welding, spot welding, laser welding, or the like. As shown more particularly in fig. 2A and 2B, the inter-cell connector includes a solid conductive portion in the form of a solid conductive shaft extending transversely across the adjacent cell compartments, with the longitudinal free ends of the solid conductive portion projecting beyond the edge of the partition wall and into contact with the corresponding current collectors. The inter-cell electrical connection is established when both ends of the solid conductive portion of the inter-cell connector are electrically connected to corresponding current collectors as shown in more detail in fig. 3A. In this application of the inter-cell connector of the present invention, the solid conductor extends entirely between a pair of current collectors of adjacent prismatic battery cells. The term "solid" is used in this specification to mean substantially solid. "solid conductor" in this specification includes solid conductors having an axial bore, particularly when the cross-sectional area of the bore is less than the cross-sectional area of the conductive portion.

With the inter-cell connector of the present invention, the effective cross-sectional area for inter-cell current conduction is significantly greater than that of an inter-cell connection formed according to conventional methods, since the contact is located at the free end of the solid conductive portion. Furthermore, a solid conductor with a cross-sectional dimension comparable to the inter-cell aperture means a larger thermal mass, so that the temperature rise near the contact is smaller compared to a contact formed according to a conventional method. As is well known, high temperature welding can change the metallic properties near the contacts, and such an inter-cell connection method provides further advantages.

After bonding the inter-cell connectors to the current collectors, the bottom of the previous case is sealed, the battery case is filled with electrolyte, and then the top of the battery case is sealed, thereby forming a complete sealed battery.

Although the inter-cell conductors are shown as solid inter-cell conductors, it should be understood that the inter-cell conductors may not be solid, may be a unitary member with a hole, or may be a set of conductors. Preferably, the area of the conductive portion of the inter-cell conductor in the inter-cell hole exceeds 50% of the area of the hole.

For electrode plate groups at the end of the battery, one of the current collectors may be connected to an end terminal through a terminal connector 280 to form an external electrical connection. As shown more specifically in fig. 3B, the hatched portions represent the vicinity of the contact points between the free end, the inter-cell connector, and the current collector.

Although the present invention has been described with reference to the above preferred embodiments, it should be understood that these embodiments are shown only as examples to aid understanding of the present invention, and are not intended to limit the scope and spirit of the present invention. Variations or modifications which are obvious or trivial to persons skilled in the art, as well as improvements made on the basis of the present invention, should be considered as equivalents of the present invention.

Further, while the invention has been described with reference to a quadrangular prismatic NiMH battery pack, it is to be understood that the invention may be applied to other prismatic battery packs, with or without modification, without loss of generality.

Claims (29)

1. A battery comprising a plurality of prismatic battery cells, wherein prismatic battery cells immediately adjacent to each other are connected by at least one inter-cell connector, said inter-cell connector extending through an inter-cell aperture through which said adjacent prismatic battery cells communicate; the battery is characterized by a continuous conductivity and/or a continuous conductance across said inter-cell aperture.

2. A battery according to claim 1, wherein the conductivity and/or conductance of said inter-cell connector across said inter-cell aperture is constant or substantially constant.

3. A battery according to claim 1 or 2, wherein the conductivity or conductance of the inter-cell connector across the inter-cell aperture is constant or substantially constant.

4. A battery according to any of claims 1 to 3, wherein the conductivity or resistivity of said inter-cell connectors across said inter-cell aperture is uniform or substantially uniform.

5. A battery comprising a plurality of prismatic battery cells, wherein prismatic battery cells immediately adjacent to each other are connected by at least one inter-cell connector, said inter-cell connector extending through an inter-cell aperture through which said adjacent prismatic battery cells communicate; the battery is characterized in that the conductive area of the inter-cell connector is continuous across the inter-cell aperture.

6. The battery of claim 5, wherein the conductive region of the inter-cell connector is constant or substantially constant across the inter-cell aperture.

7. A battery according to any of the preceding claims, wherein said battery comprises a housing having a plurality of cell compartments for receiving said plurality of prismatic cells such that one said prismatic cell is received in one said cell compartment, immediately adjacent said prismatic cells being connected by at least one said inter-cell connector extending through a said inter-cell aperture through a dividing wall separating adjacent said cell compartments, said cell compartments receiving immediately adjacent said prismatic cells being in communication through said inter-cell aperture.

8. A battery according to any of the preceding claims, wherein at least the part of said inter-cell connector extending through said inter-cell aperture is integrally formed or formed in one piece.

9. A battery according to any of the preceding claims, wherein the portion of said inter-cell connector extending through said inter-cell aperture forms a fluid seal preventing leakage of electrolyte through said inter-cell aperture.

10. A battery according to any of the preceding claims, wherein at least the portion of said inter-cell connector extending through said inter-cell aperture is tapered and is further configured as a fluid seal to prevent leakage of electrolyte through said inter-cell aperture.

11. A battery according to any of the preceding claims, wherein at least the portion of said inter-cell connector extending through said inter-cell aperture is tapered, and said inter-cell connector is configured such that one longitudinal end of said inter-cell connector is insertable into said inter-cell aperture and the other longitudinal end has a transverse cross-section configured to seal said inter-cell aperture.

12. A battery according to any of the preceding claims, wherein each of said prismatic cells comprises an electrode plate group having a positive current collector and a negative current collector, the corresponding current collectors of an adjacent pair of prismatic cells being connected by at least one of said inter-cell connectors.

13. A battery according to any of the preceding claims, wherein the conductance of said inter-cell connector across said inter-cell aperture is at a maximum in terms of the size of said inter-cell aperture.

14. A battery according to any of the preceding claims, wherein end flanges are formed at respective longitudinal ends of said inter-cell connectors so as to cover said inter-cell aperture.

15. The battery pack of claim 14, wherein the inter-cell aperture is formed on a dividing wall separating two adjacent cell compartments, the flange being in compressive engagement with the dividing wall.

16. A battery according to any of the preceding claims, wherein said inter-cell conductor comprises a first end and a second end located in different cell compartments, and immediately adjacent prismatic battery cells are joined at said first end and said second end.

17. A battery according to any of the preceding claims, wherein an adjacent pair of prismatic battery cells are connected by at least one inter-cell connector by forming contacts outside said inter-cell aperture.

18. The battery pack of claim 17 wherein each of the contacts is formed by welding, soldering or other fusing methods.

19. A battery according to any of the preceding claims, wherein the electrical connection between an adjacent pair of prismatic cells and an inter-cell connector is made by forming contacts at opposite ends of the inter-cell connector such that the portion of the inter-cell connector between the contacts is not welded.

20. A battery according to any of the preceding claims, wherein said inter-cell connector comprises a fastener for fastening and sealing said inter-cell connector to a cell compartment wall.

21. A battery according to any of the preceding claims, wherein a circumferential flange is formed at a longitudinal end of the inter-cell connector, the other longitudinal end of the inter-cell connector having a thread for receiving a threaded fastener, the inter-cell connector being sealed to the cell compartment wall by cooperation with the circumferential flange and the threaded fastener.

22. The battery pack of claim 21 wherein the threaded fastener comprises a threaded fastening nut.

23. The battery of claim 21 or 22, wherein said inter-cell connector is tapered towards a longitudinal end away from said flange, said inter-cell connector being dimensioned such that a distal end of said inter-cell connector is insertable into said inter-cell aperture and a cell partition wall is interposed between said distal end and flange end of said inter-cell connector when said inter-cell connector is fastened and tightened onto said cell partition wall.

24. A battery according to any of the preceding claims, wherein the current collectors of said prismatic battery cells have a C-shaped cross-section, and said inter-cell connectors are joined to said current collectors in the middle of said C-shaped cross-section.

25. A battery according to any preceding claim, wherein the battery is a nickel metal hydride battery with potassium hydroxide electrolyte.

26. A battery according to any of the preceding claims, wherein adjacent pairs of prismatic battery cells are joined by a plurality of said inter-cell connectors at a plurality of locations distributed along the length of the respective pair of current collectors.

27. A method of forming an inter-cell connection between a pair of adjacent prismatic battery cells of a battery, the method comprising:

i. attaching and securing the inter-cell connector to the cell partition wall; and

connecting the inter-cell connector to the current collectors of an adjacent pair of prismatic battery cells.

28. The method of claim 27, wherein the method further comprises the steps of: an electrically conductive contact is formed outside the inter-cell aperture and between said inter-cell connector and said current collectors of an adjacent pair of prismatic battery cells.

29. The method of claim 27, wherein the inter-cell connector comprises an intermediate connector having opposite ends, the method further comprising forming a pair of electrically conductive contacts between an adjacent pair of prismatic battery cells and at the opposite ends.