Battery assembly and method of forming the same

A battery assembly includes a first cell and a second cell adjacent the first cell. A first insulator and a second insulator extend over and encapsulate first electrode and second electrode. A shell extends over the first and second insulators thereby encapsulating the first and second insulators. A mechanical connection is defined between the first insulator of the fist cell and the second insulator of the second cell.

FIELD OF THE INVENTION

The subject invention relates to battery packs, and more particularly to rechargeable battery pack assembly having electrical and mechanical components arranged to reduce overall battery pack size and increase reliability and improve safety characteristics.

BACKGROUND OF THE INVENTION

Motor vehicles, such as, for example, hybrid vehicles use multiple propulsion systems to provide motive power. This most commonly refers to gasoline-electric hybrid vehicles, which use gasoline (petrol) to power internal-combustion engines (ICEs), and electric batteries to power electric motors. These hybrid vehicles recharge their batteries by capturing kinetic energy via regenerative braking. When cruising or idling, some of the output of the combustion engine is fed to a generator (merely the electric motor(s) running in generator mode), which produces electricity to charge the batteries. This contrasts with all-electric cars which use batteries charged by an external source such as the grid, or a range extending trailer. Nearly all hybrid vehicles still require gasoline as their sole fuel source though diesel and other fuels such as ethanol or plant based oils have also seen occasional use.

Batteries and cells are important energy storage devices well known in the art. The batteries and cells are typically comprised of electrodes and an ion conducting electrolyte positioned therebetween. For example, the rechargeable lithium ion cell, typically comprises essentially two electrodes, an anode and a cathode, and a non-aqueous lithium ion conducting electrolyte therebetween. The anode (negative electrode) can be a carbonaceous, or metallic, or metal alloy electrode that is capable of intercalating lithium ions. The cathode (positive electrode), a lithium retentive electrode, is also capable of intercalating lithium ions. The anode comprises any of the various materials such as carbon (e.g., graphite, coke, carbon fiber, etc.), mixed metal oxides (such as Li4Ti5O12or silicon oxide), metals (such as Si or Sn), metal alloy (such as Si/Sn alloys) which are capable of reversibly storing lithium species, and which are bonded to an electrically conductive current collector (e.g., copper foil) by means of a suitable organic binder (e.g., polyvinylidine fluoride, PVdF). The cathode comprises such materials as transition metal oxides or chalcogenides that are bonded to an electrically conducted current collector (e.g., aluminum foil) by a suitable organic binder. Oxide of chalcogenide compounds include oxides, sulfides, selenides, and tellurides of such metals as vanadium, titanium, chromium, copper, molybdenum, niobium, iron, nickel, cobalt, and manganese. Lithiated transition metal oxides are, at present, the preferred positive electrode intercalation compounds.

Examples of suitable cathode materials include LiMnO2, LiCoO2, LiNiO2, and LiFePO4, their solid solutions and/or their combination with other metal oxides and dopant elements, e.g., titanium, magnesium, aluminum, boron, etc. The electrolyte in such lithium ion cells comprises a lithium salt dissolved in a non-aqueous solvent which may be (1) completely liquid, (2) an immobilized liquid (e.g., gelled or entrapped in a polymer matrix), or (3) a pure polymer. Known polymer matrices for entrapping the electrolyte include polyacrylates, polyurethanes, polydialkylsiloxanes, polymethacrylates, polyphosphazenes, polyethers, polyvinylidine fluorides, polyolefins such as polypropylene and polyethylene, and polycarbonates, and may be polymerized in situ in the presence of the electrolyte to trap the electrolyte therein as the polymerization occurs.

Known polymers for pure polymer electrolyte systems include polyethylene oxide (PEO), polymethylene-polyethylene oxide (MPEO), or polyphosphazenes (PPE). Known lithium salts for this purpose include, for example, LiPF6, LiClO4, LiSCN, LiAlCl4, LiBF4, LiN(CF3SO2)2, LiCF3SO3, LiC(SO2CF3)3, LiO3SCF2CF3, LiC6F5SO3, LiCF3CO2, LiBOB, LiAsF6, and LiSbF6. Known organic solvents for the lithium salts include, for example, both cyclic and linear carbonate esters (such as propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate), cyclic ethers, cyclic esters, glymes, cyclic esters, formates, esters, sulfones, nitrates, and oxazoladinones. The electrolyte is incorporated into pores in a separator layer between the anode and the cathode. The separator layer may be either a microporous polyolefin membrane or a polymeric material containing a suitable ceramic or ceramic/polymer material.

The art is replete with various designs of conventional lithium batteries, which present a polymer soft pack batteries that uses prismatic or cylindrical cans or rectangular boxes as a package for the battery cells as seen by reference to the U.S. Pat. No. 5,639,571 to Waters, et al.; U.S. Pat. No. 6,120,935 to Van Lerberghe; U.S. Pat. No. 6,368,743 to Guerin et al. and the United States Patent Publication Nos. 2002/0045096 to Sandberg et al.; 20050123828 to Oogami et al.; 20050271934 to Kiger et al.; and 20040115519 to Lee et al. disclose other designs of battery packs.

The United States Patent Publication No. 20050271934 to Kiger et al. teaches a low-profile battery pack having an electrolyte barrier. The pack includes a plurality of rechargeable cylindrical cells, being arranged in end to end pairs of two cells. A cleavage void formed by the convex geometry of the cells accommodates at least one insulator and a first circuit board. Tabs couple the cells to the first circuit board. A flexible substrate couples the first circuit board to a second circuit board. The assembly is then placed in a housing having a first compartment and a second compartment, such that the cells are placed in the first compartment and the second circuit board is placed in the second compartment. Between the first and second compartments exists an electrolyte barrier.

Due to this adjacent arrangement, the aforementioned cleavage void is formed between the intersection line and a plane running across the top of each cell so as to be tangent to the convex curvature of each cell. The cleavage void is essentially a triangular shaped space, where the triangle has two concave sides. Alluding to the above, the insulator taught by the United States Patent Publication No. 20050271934 to Kiger et al. is a plastic member that has a geometric cross-section that fits within the cleavage space. The cross sectional shape is generally triangular, with two of the sides having concave curvatures to mate between a pair of cylindrical cells. The insulator is a separate element and is not an integral part of the cells. The insulator taught by the United States Patent Publication No. 20050271934 to Kiger et al. is specific to the cells having circular configuration.

The United States Patent Publication No. 20050123828 to Oogami et al. teaches a unit cell, formed in a flat shape in the presently filed embodiment, internally includes an electric power generating element comprised of a positive electrode plate, a negative electrode plate and a separator, all of which are stacked in such order. The unit cell forms a secondary battery, such as a lithium ion secondary battery, employing a gel polymer electrolyte. With the unit cell, a laminate film with a three-layer structure is used as an outer sheath and formed in three layers that include an aluminum foil interposed between resin films each made of polyamide resin.

Alluding to the above, the unit cell has the positive electrode tab and the negative electrode tab as tabs forming output terminals extending in a direction perpendicular to the stack direction. The positive electrode tab and the negative electrode tab are extracted outside an outer sheath. Formed in the positive electrode tab and the negative electrode tab, respectively, are holes, to which insulator pins, each having a surface subjected to insulation treatment, are inserted. The unit cells are alternately stacked such that the electrode tabs have positive and negative polarities alternately arranged in the stack direction, i.e., the positive electrode tab and the negative electrode tab are alternately stacked. The electrically conductive washers and the insulation washes are alternately set through the insulator pins such that the positive electrode tabs and the negative electrode tabs are sandwiched. In particular, the insulation washer is interposed between the positive electrode tab and the negative electrode tab layered thereon, and the electrically conductive washer is interposed between the negative electrode tab and the positive electrode tab layered thereon.

The insulation washer is placed on the positive electrode tab and the electrically conductive washer is placed on the negative electrode tab. Incidentally, although the electrically conductive washer and the insulation washer are located on the positive electrode tab and the negative electrode tab of the unit cell remaining in the uppermost layer, respectively, in dependence on a sequence in which the electrode tabs are arranged, it doesn't matter if these component parts are dispensed with depending on circumstances. Similar to the unsulator taught by the United States Patent Publication No. 20050271934 to Kiger et al., the insulator of the United States Patent Publication Nos. 20050123828 to Oogami et al. present a separate element, which is not an integral part of the cells.

The United States Patent Publication Nos. 20050123828 to Oogami et al. and 20050271934 to Kiger et al. present several disadvantages such as failure to provide a battery assembly with self-locating mechanical elements aimed to increase structural integrity of the battery assembly required while individual cells of the battery assembly are transported between various locations and do not reduce the weight of the battery assembly.

But even to the extend of being effective in certain respects, there is a constant need in the area of the battery art for an improved design of a battery pack having effective packaging characteristics, structural integrity thereby eliminating problems associated with current designs of prior art battery packs.

SUMMARY OF THE INVENTION

A battery assembly of the present invention is adaptable to be utilized in various configurations including and not limited to an overlapping battery cell packaging configuration and a vertical stack battery cell packaging configuration. The battery assembly includes a first cell and a second cell adjacent the first cell. Each first and second cells have a first electrode adjacent a first current collector and a second electrode of the charge opposite from the first electrode and adjacent a second current collector.

A separator layer is positioned between the first and second electrodes with the first and second electrodes conducting electrolyte therebetween. A first insulator and a second insulator extend over and encapsulate the first electrode and the second electrode. A shell extends over the first and second insulators thereby encapsulating the first and second insulators. The shell terminates into a negative terminal and a positive terminal opposed the negative terminal.

A plurality of contacts, spaced from one another, are defined in each of the positive and negative terminals. The first and second cells present a mechanical connection defined therebetween. The mechanical connection presents a boss integral with and extending outwardly from the first insulator of the first cell through one of the contacts and beyond the shell of the first cell to mechanically engage a seat defined by the second insulator of the second cell as a tie rod or stud extends transversely through each contact thereby preventing relative movement between the first and second cells.

An advantage of the present invention is to provide a battery assembly presenting a self-locating mechanical connection that increases structural integrity of the battery assembly required while individual cells of the battery assembly are transported between various locations.

Another advantage of the present invention is to provide a battery assembly having efficient packaging characteristics.

Still another advantage of the present invention is to provide a battery assembly that reduces the weight by eliminating connecting hardware such as electrical studs and the like.

Still another advantage of the present invention is to provide a battery assembly that reduces manufacturing costs due to simplified assembly pattern.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the Figures, wherein like numerals indicate like or corresponding parts, a battery assembly or a battery pack of the present invention is generally shown at10. Preferably, the battery pack10includes four rows, generally indicated at12, of battery cells (the cell), generally indicated at14, connected with and extending along each row12in overlapping relationship. Each row12includes five stacks of the cells14. Each stack of the cells14are interconnected with one another in the pattern known to those skilled in the battery art and extend along each row12in overlapping relationship with one another. The battery pack10is supported by and connected to a tray16formed from a polymeric material. A battery pack10of the present invention is adaptable to be utilized in various configurations including and not limited to an overlapping battery cell packaging configuration, as illustrated inFIGS. 1,3,4, and6, a vertical stack battery cell packaging configuration, as illustrated inFIGS. 2 and 5.

Each cell14includes a plurality of battery components (not shown) co-acting between one and the other conducting electrolyte therebetween as known to those skilled in a lithium battery art. A first electrode is adjacent a first current collector and a second electrode of charge opposite from the first electrode is adjacent a second current collector. A separator layer is positioned between the first and second electrodes with the first and second electrodes conducting electrolyte therebetween.

As best illustrated inFIGS. 2,4and6, each battery cell14presents at least one positive terminal lip20and at least one negative terminal lip22. Three electrical contacts are provided for each polar contact to divide the current carrying capacity and to provide auxiliary paths for current flow in the event that one or more contacts24, as shown inFIG. 4, would develop high resistance or electrically open. Each contact24is further defined by an aperture or opening25defined in each terminal lip20and22includes extending therethrough to provide the means to guide the cells14over electrical studs or tie rods26. The contacts24are also provided with an electrical insulator (to be discussed as the description of the present invention proceeds) that extends outside the cell case or shell. The insulators are designed to ensure that the cells14, when stacked or overlapped, are mechanically interlocked to provide structural integrity.

The stud or the tie rod26extends through each opening24at each of the terminal lips20and22and is secured by a nut28in a vertical stack as shown inFIG. 2. A cover strip30extends along each of the upper negative terminal lip22and positive terminal lip20and between each nut28to distribute pressure generated by mechanical connection of the tie rod26and the nut28. The positive and negative electrical contacts of the cell are exposed on both sides of the cell14.

As illustrated inFIGS. 2,4and6, each cell14includes a shell32or packaging envelope formed from a sheet of packaging material, such as aluminum, which is placed under the aforementioned cell components including an individual cell busbar or tab and cell terminal34and a remaining part of the packaging shell is folded over the battery core to form the aforementioned shell32. Preferably, the shell30defines a vent (not shown) designed to function as an escape port or outlet for releasing any gas concentrated in the shell32due to overcharging or other conditions of the cell14. Those skilled in the lithium battery art will appreciate that the shell30may also be fabricated from any other suitable materials without limiting functional characteristics of the present invention.

As best illustrated inFIGS. 3 and 4, a first or upper insulator36and a second or lower insulator38, both formed from a polymeric material, extend over and encapsulate the first electrode tab and the second electrode tab. The shell32extends over the first and second insulators36and38thereby encapsulating the first and second insulators36and38. The shell32terminates into a negative terminal and a positive terminal opposed the negative terminal, i.e. the positive terminal lip20and at least one negative terminal lip22, respectively. A plurality of the contacts24spaced from one another are defined in each of the positive and negative terminal lips20and22.

The cells14present a mechanical connection defined therebetween and used in all of the packaging configurations as described above. A boss44is homogeneously integral with and extends outwardly from the upper insulator36surrounding the contacts24. In particular, the boss44of the first insulator36of one of the cells14extends through one of the contacts defined by the contacts24and beyond the shell32of the first cell to mechanically engage a seat or nest46defined by the second insulator38of the adjacent cell14as the tie rod or stud26extends transversely through each contact24thereby preventing relative movement between the cells14to form the vertical stack or overlapping set of the cells14. The outer diameter of the boss44is smaller the inner diameter of the nest46to allow male and female type of engagement between adjacent cells14. Alternatively, the second insulator38may also include a boss (not shown) homogeneously integral with and extending outwardly from the second insulator38and beyond the opening42of the shell32surrounding the contacts24. As such, the boss44of one cell14will frictionally engage the boss of another cell14.

As illustrated inFIGS. 3 and 4, the tray16utilizes over-molded conductive traces or mono-block busbars49or lines connected to each stud26thereby transmitting a bussing power and communications from the electrical string of battery cells14to a remote electronic controller (not shown). Various connecting patterns such as Zig-Zag, U-shaped, and S-shaped are utilized to conduct operative communication between individual stacks and cells14are not intended to limit the present invention. Multiple electrical contacts are used to connect bussing via connectors located on the controller.

As illustrated inFIGS. 2 and 5, as the battery assembly10is formed, the individual cells14are placed over the studs26at every other cell position on the tray16. An electrically conductive disk50is then placed over each stud26until resting on each cell contact surface. Preferably, the electrically conductive disk50is formed from copper. The remaining cells14are then placed over the studs14in the un-occupied positions of the tray16, overlapping the previously placed cells14. The nut28is applied to each stud26and is torqued to apply communications from an electrical string of battery cells14to a remote electronic controller (not shown). The cells14are placed over the studs26at every cell position on the tray16.

As illustrated inFIG. 5, an electrically insulating disk52, formed from a polymeric material, is placed over the remaining studs26, opposite polarity of where the electrically conductive disks50were placed. One additional cell14is then placed over the studs26at each position on the tray16along with the conductive and insulating disks50and52as previously described. This process is repeated until the proper number of cells14and the conductive and insulating disks50and52have been placed onto all cell positions of the tray16. The nut28applies compression and thus creates a solid cell stack. Alternatively, foam or other polymeric material may be introduced by injection or the like into voids or clearances defined between adjacent or stacked cells14as the stack is formed to add to structural integrity of the stack to form an encapsulated stack.

The novelty of the present inventive concept provides numerous advantages over prior art design. The battery assembly design presenting the aforementioned mechanical and electrical interlocking interface features provides the means for safe handling of individual charged cells14that may be vertically stacked or overlapped in multiple cell; series or parallel, configurations, as illustrated in Figures. Another novel feature of the present design presents an innovative cell design, which is incorporated into a low profile, low mass, and efficient space configuration for packaging multiple cells14in series or parallel configurations. Alluding to the above, the cell terminal34, yet sub-flush of the cell shell nearly eliminate the risk of short circuiting during manufacturing or any means of individual cell transport. The inventive battery assembly provides an efficient manufacturing process directed to reduce the need for costly sophisticated assembly equipment thereby promoting labor efficient and cost effective packaging configurations and reductions in pack mass.

The inventive concept of the present invention provides other advantages over the prior art. One of these advantages provides a battery assembly presenting a self-locating mechanical connection that increases structural integrity of the battery assembly required while individual cells of the battery assembly are transported between various locations. Still another advantage of the present invention is to provide a battery assembly having efficient packaging characteristics. Still another advantage of the present invention is to provide a battery assembly that reduces the weight by eliminating connecting hardware such as electrical studs and the like. Still another advantage of the present invention is to provide a battery assembly that reduces manufacturing costs due to simplified assembly pattern