KR20030066764A - Mechanically improved rechargeable battery - Google Patents

Abstract

The present invention relates to rechargeable batteries, modules and fluid cooled battery systems that are improved in mechanical and thermal aspects. The battery is in the form of a prism with an aspect ratio of optimal thickness to width to height, which, when compared to a prism battery that does not have an optimized aspect ratio, allows the battery to have balanced optimal characteristics. Optimized thickness, width and height allow for maximum capacity and power output and eliminate undesirable side effects. The battery case enables expansion in the one direction, which can be easily supplemented with external mechanical compressive force corresponding to either direction. In the module 32, the battery is bundled in module bundling / compression means under external mechanical compression that is maximized to balance external pressure due to expansion and provides additional internal compression to provide a distance between the positive electrode and the negative electrode. To decrease the overall battery power. The fluid cooling battery pack 39 includes a battery pack case 40 having a coolant inlet 41 and a coolant outlet 42; A battery module located within the case and spaced apart from the wall of the case and spaced apart from other battery modules in the case to form a coolant flow channel 43 along at least one surface of the bundled battery; And at least one coolant conveying means 44. The width of the coolant flow channel is configured to allow maximum thermal movement. Finally, the batteries, modules and packs are variable to portions of the rechargeable battery system that are most directly exposed to the standby state to maintain the temperature of the rechargeable battery system within a desired operating distance under variable standby conditions. Also included are means for providing thermal insulation.

Description

Mechanically Improved Rechargeable Battery {MECHANICALLY IMPROVED RECHARGEABLE BATTERY}

This application is partly filed in US Application No. 08 / 140,933, filed October 25, 1993.

The present invention relates generally to metal hydride batteries, battery modules made therefrom, and improvements to battery packs made from such modules. In particular, the present invention relates to mechanical and thermal improvements in battery design, battery module design and battery pack design.

Rechargeable prism batteries are used in many industrial and commercial applications such as fork lifts, golf carts, continuous power supplies and electric vehicles.

Rechargeable lead acid batteries are the most widely used battery type at present. Lead-acid batteries are a useful source of power for starting motors for internal combustion engines. However, these batteries have become impractical power sources for electric vehicles because of their low energy density of about 30 Wh / kg and the lack of adequate heat resistance. Electric vehicles using lead-acid batteries require recharging immediately after driving a short distance, and require about 6 to 12 hours to recharge and contain toxic substances. In addition, electric vehicles using lead-acid batteries have slow acceleration, are weak against rapid discharge and have only about 20,000 miles of battery life.

Nickel metal hydride batteries (hereinafter referred to as "Ni-MH batteries") are far superior to lead acid batteries, and Ni-MH batteries are the most likely battery type available for electric vehicles. For example, Ni-MH batteries, such as those disclosed in U.S. Patent Application No. 07 / 934,976, filed by Ovshinsky Fetcenko, which is a corresponding application of this application and disclosed below, exhibit much higher energy density than lead acid batteries, The electric vehicle can be powered by more than 250 miles before being recharged, recharged within 15 minutes and contains no toxic substances. Electric vehicles using Ni-MH batteries have exceptional acceleration and have a battery life of about 100,000 miles or more.

Extensive research has been made in the past to improve the power and charging capabilities of Ni-MH batteries in electrochemical aspects, which are described in US Pat. Nos. 5,096,667, 5,104,617, and US Pat. It is disclosed in detail in 934,976. The contents of all these references are clearly explained below.

For the first time, Ovshinsky and his team focused on metal hydride alloys that form negative electrodes. As a result of these efforts, they have been able to significantly improve the reversible hydrogen storage characteristics required for efficient and economical battery applications, and they are capable of high-density energy storage, efficient reversibility, high electrical efficiency, structural modifications, or no toxic effects. Has been able to produce batteries capable of hydrogen storage, long cycle life and repeated discharge and discharge. The improved properties of these so-called "Ovonic" alloys are now obtained by integrating selected modifier elements and host matrices to alter local chemical and local structural configurations. Disordered metal hydride alloys have very high density of catalytically active sites and storage sites compared to single or multiphase transparent materials. Improved efficiency of electrochemical charge / discharge and an increase in electrical energy storage capacity are obtained due to these additional sites. The nature and number of storage sites can be designed separately from catalytically active sites. In particular, these alloys are modified such that large capacity storage of hydrogen atoms decomposed at bond strength is possible within the range of reversibility suitable for use in secondary battery applications.

Some highly efficient electrochemical hydrogen storage materials are formed based on the disordered materials as described above. These are active materials of the Ti-V-Zr-Ni type, such as those disclosed in US Pat. No. 4,551,400 (hereinafter referred to as "'400 patent") by Sapru, Hong, Fetcenko, and Venkatesan, which are described below. It is disclosed as a document. These materials form hydrides in reverse to store hydrogen. All materials used in the '400 patent use a common Ti-V-Ni compound which is at least Ti, V, and Ni present and may be modified with Cr, Zr, and Al. This material of the '400 patent is a multiphase material including, but not limited to, one or more phases with crystal structures of C ₁₄ and C ₁₅ forms.

Other Ti-V-Ni alloys are also used for rechargeable hydrogen storage negative electrodes. Such types of materials are disclosed in US Pat. No. 4,728,586 (hereinafter referred to as “'586 Patent”) of Venkatesan, Reichman and Fetcenko, which is described below by reference. The '586 patent discloses Ti-V-Ni-Zr alloys of a particular subclass consisting of Ti, V, Zr, Ni and the fifth component, Cr. The '586 patent refers to the possibility of additives or modifiers in addition to alloys of Ti, V, Zr, Ni and Cr components, and can be predicted from certain additives and modifiers, the amounts of these modifiers and their interactions, and from them. There are some general advantages.

In comparison to the Ovonic alloys described above, the alloys are generally regarded as "order-in" materials with other chemical, microstructure and electrochemical properties. Initially, the performance of ordered materials was poor, but in the early 1980s, as the degree of deformation became stronger (ie, as the number and amount of basic modifiers increased), these performances began to improve significantly. This is due to the disorder provided by the modifier to the same extent as due to the modifier's electrical and chemical properties. The development of alloys from a particular class of "ordered" materials to current multi-component, multiphase "disordered" alloys can be found in the following patents: (i) US Patent No. 3,874,928; (ii) US Patent No. 4,214,043; (iii) US Patent No. 4,107,395; (iv) US Pat. No. 4,107,405; (v) US Pat. No. 4,112,199; (vi) US Pat. No. 4,125,688; (vii) US Pat. No. 4,214,043; (viii) US Pat. No. 4,216,274; (ix) US Pat. No. 4,487,817; (x) US Pat. No. 4,605,603; (xii) US Patent No. 4,696,873; And (xiii) US Pat. No. 4,699,856 (these references are comprehensively disclosed in US Pat. No. 5,096,667, the discussions of which are expressly incorporated by reference).

As briefly mentioned, for all metal hydride alloys, as the degree of change increases, the importance of the role of the initial ordered base alloys is less than the characteristics and disorder caused by special modifiers. In addition, analysis of current multi-component alloys that are available on the market and produced by various manufacturers shows that these alloys change following the guidelines set for Ovonic alloy systems. As a result, as mentioned above, very much modified alloys are disordered materials characterized by multiple components and multiphase, ie Ovonic alloys.

Clearly, the introduction of Ovonic alloy technology has made important advances in the electrochemical aspects of the activity of Ni-MH batteries. However, it should be noted that until recently the mechanical and thermal aspects of Ni-MH battery performance have been overlooked.

For example, in electric vehicles, battery weight is an important factor since it is the largest component of the vehicle weight. For this reason, reducing the weight of individual batteries has become an important consideration in designing batteries for electric propulsion vehicles. In addition to reducing the weight of the battery, the weight of the battery module must be reduced while still providing the necessary mechanical requirements of the module (ie, ease of transport, stiffness, etc.). In addition, when such a battery module is combined with a battery pack system (such as in an electric vehicle), the battery pack component should be as lightweight as possible.

It should be particularly noted that electric vehicle applications must have important requirements for thermal management. This is because the individual cells are close together and bundled together and many cells are electrically and thermally connected to each other. Therefore, since there is an inherent tendency to generate significant heat during charging and discharging, the operable battery design for an electric vehicle is determined depending on whether the generated heat can be sufficiently controlled.

The heat source consists mainly of three layers. First, atmospheric heat due to the operation of the vehicle in hot climates. Second, resistance or I ² R heating during charging and discharging, where I represents the current flowing into or out of the battery and R represents the resistance of the battery. Third, excessive amounts of heat are generated during overcharging due to gas recombination.

Although these parameters are generally common to all electric battery systems, they are particularly important for nickel-metal hydride battery systems. This is because Ni-MH has such a high specific energy and the charge and discharge currents are also high. For example, to charge a lead-acid battery within an hour, a current of 35 Amps is used, while a recharge of a Ni-MH battery uses a current of 100 Amps for the same hour of recharging. Second, heat release is more difficult than lead-acid batteries because Ni-MH has exceptional energy density (i.e. energy is stored very densely). This is because the surface area-to-volume ratio is considerably smaller than lead-acid batteries, which means that the heat generated is 2.5 times more for Ni-MH batteries than for lead-acid batteries, while the heat dissipation surface is reduced.

The following examples will help you understand the thermal management challenges you face when designing Ni-MH battery packs for electric vehicles. US Patent No. 5,378,555, which is hereby incorporated by reference to Patents General Motors, discloses an electric vehicle battery pack using a lead acid battery. A battery pack system using lead acid batteries has a capacity of about 13 kWh, a weight of about 800 pounds, and a transport distance of about 90 miles. By replacing lead-acid battery packs with Ovonic battery packs of the same size, the capacity increases to 35 kWh and the transportation distance increases by approximately 250 miles. This comparison shows that for 15 minutes of charging, the power supplied to the Ni-MH battery pack has a corresponding additional heat and is 2.7 times greater than the power supplied to the lead-acid battery pack. However, this situation is somewhat different during discharge. In order to power a vehicle with a constant speed on the highway, the current absorbed by the battery is the same whether it is a Ni-MH battery or a lead acid battery (or other power source). Basically, the electric motor that drives the vehicle does not know or care where it gets its energy or what type of battery it supplies. The difference between the heating of the Ni-MH battery and the lead acid battery during discharge is the discharge distance. That is, because Ni-MH batteries drive the vehicle 2.7 times farther than lead-acid batteries, they have more operating time before "cooling".

In addition, when small consumer batteries or relatively very large batteries are used alone for a limited time, the heat generated during charging and discharging of Ni-MH batteries is usually not a problem in them, while functioning as a continuous power source. Large batteries that generate sufficient heat during discharging and charging, especially when one or more are used in series or in parallel, such as in satellite or electric vehicles, will affect the ultimate performance of the battery module or battery pack system. .

As a result, batteries, battery modules, and battery pack system designs reduce their overall weight, implement thermal management, which is an essential requirement for the smooth operation of electric vehicles, without reducing energy storage capacity or power output, and It is necessary to improve the reliability of the, and reduce its cost.

A deficiency in prior art

Thermal management of electric vehicle battery systems using high energy batteries has never been proven before. Some techniques, such as Na-S, which operate at elevated temperatures, are such that they are completely insulated to maintain a specific operating temperature. This arrangement is undesirable due to the heavy burden on the overall energy density due to excessive load, high complexity and excessive cost of the thermal management device. In other systems, such as Ni-Cd, thermal management devices have also attempted to use water-cooled systems. In addition, this type of thermal management system carries weight, complexity and cost issues for battery packs.

As briefly stated, the prior art is based on an integrated battery structure / internal design, battery module and lightweight, inexpensive, low cost, thermal aspect that combines the mechanical support of the battery, module and pack with an air cooling thermal management system. It does not present a battery pack system that can be managed by.

Summary of the Invention

According to one aspect of the invention, the invention provides a mechanically improved rechargeable battery. The battery comprises: 1) a battery case having a battery positive electrode terminal and a battery negative electrode terminal; 2) at least one battery positive electrode positioned in the battery case and electrically connected to the battery positive electrode terminal; 3) at least one battery negative electrode positioned in the battery case and electrically connected to the battery negative electrode terminal; 4) at least one battery electrode separator positioned between the positive electrode and the negative electrode in the battery case to electrically insulate the positive electrode from the negative electrode but enable chemical interaction thereof; And 5) a battery electrolyte surrounding the positive electrode, the negative electrode, and the separator. The battery case is prismatic and has an optimum thickness to width to height aspect ratio.

According to another aspect of the present invention, the present invention includes an improved, high power battery module. The battery module of the present invention comprises: 1) a plurality of individual batteries; 2) a plurality of electrical interconnections connecting said individual batteries of said module to each other and providing means for electrically connecting separate battery modules to each other; And 3) battery module bundling / compression means. The battery is bundled within the module bundling / compression means under optimal external mechanical compression to balance external pressures caused by the expansion of battery components and provides additional internal compression on the battery electrodes in each cell. Therefore, the distance between the positive electrode and the negative electrode is reduced to increase the total cell power.

The module bundling / compression means 1) takes into account the required degree of battery compression; 2) performs the required mechanical functions of the module bundler with resistance to vibration; 3) Designed as lightly as possible.

According to another aspect of the present invention, the present invention provides a fluid cooling battery pack system having a lightweight mechanical structure. Most basically, the fluid cooling battery pack system of the present invention comprises: 1) a battery pack case having at least one coolant inlet and at least one coolant outlet; 2) conducting and conducting radioactive, convective from the battery to the coolant, the width of which is located within the case, spaced apart from the case wall and spaced apart from other battery modules in the case and along at least one surface of the bundled battery. At least one battery module configured to form a coolant flow channel having an optimal size that allows for maximum heat transfer through the heat transfer device of the apparatus; And 3) at least one coolant conveying means for allowing said coolant to flow into said coolant inlet means of said case to flow through said coolant flow channel and to be discharged through said coolant outlet means of said case. In a preferred embodiment, the battery pack system is cooled with air.

According to another aspect of the invention, the invention provides that the above mentioned mechanical design of the battery, module and battery pack system is designed to quickly charge the battery pack system while extending battery life with minimal overcharge and heat generation management. Electronically integrated via charger algorithm.

Finally, the batteries, modules and packs are at least one of the rechargeable battery systems most directly exposed to the standby heat state to maintain the temperature of the rechargeable battery system within a desired operating distance in a variable standby state. It also includes means for providing variable thermal insulation to that portion.

1 shows a cross-sectional view of a mechanically improved rechargeable battery according to the invention, in particular a battery electrode, a separator, a battery case and battery electrode terminals;

2 is a schematic cross-sectional exploded view showing a mechanically improved rechargeable battery according to the present invention, in particular battery components interacting upon coupling;

3 is an enlarged view of the terminal, can top, terminal seal and electrode comb shown in FIG. 2;

4 is a cross sectional view of a corrugated seal formed to seal a battery terminal on top of a battery can;

5 is a cross-sectional view showing one embodiment of the battery terminal, in particular how the pressure outlet can be integrated with the terminal;

6 is a cross-sectional view showing another embodiment of the battery terminal, in particular how the terminal can be integrated with an electrical lead connection device in the form of a socket;

7 shows an example of an electrode comb;

FIG. 8 is a top view of the battery module of the present invention, in particular the batteries that are bundled, including the end plate and the compression shaft, and the support bars and the support plate under constant directional, external mechanical compression;

FIG. 9 is a side view of the battery module of FIG. 8, in particular a metal bar set in a slot in the rib of the end plate; FIG.

10 shows a partial view of the battery module of FIGS. 8 and 9, in particular the end plate and the compression bar interacting with each other;

11 is a top view of a battery module of the invention, in particular a module spacer according to the invention and a spacer tab attached thereto;

FIG. 12 is a side view of the battery module of FIG. 11, in particular module spacers located on top and bottom of the battery module; FIG.

Figure 13a illustrates an embodiment of the end plate of the battery module according to the invention, in particular the end plate with ribs formed;

13B is a cross-sectional view of the ribbed end plate of FIG. 13A;

14 illustrates an embodiment of a braided cable interconnector useful in modules and battery packs, in particular flat braided cable electrical interconnectors, in accordance with the present invention;

15 is a top view of a matrix arrangement of battery modules in a pack case in which an embodiment of a fluid cooled battery pack according to the invention, in particular the module spacer, forms coolant flow channels, fluid inlet and outlet ports and fluid transfer means; ;

16 is a schematic diagram of battery temperature vs. downtime showing a temperature controlled fan algorithm that affects battery temperature during pack self discharge;

17 is a schematic showing battery resistance and battery thickness versus external compressive force, optimal functional range;

18 is an illustration of the temperature effect on a particular energy of a battery showing the composition of the battery temperature versus specific energy of Wh / kg;

19 is an illustration of the temperature effect on a specific power of a battery showing the configuration of the battery temperature vs. specific power of W / kg;

20 is a schematic diagram of the relationship between coolant volume flow rate and maximum heat transfer and coolant rate versus centerline spacing (relative to average width of coolant channel) for coolant flowing vertically through the coolant flow channel;

21 is a schematic diagram of the relationship between coolant volume flow rate and maximum heat transfer and coolant rate versus centerline spacing (relative to average width of coolant channel) for coolant flowing horizontally through the coolant flow channel;

Figure 22 is a schematic diagram of the temperature rise and pack voltage vs. time relationship from the atmosphere during charging and discharging using the "temperature compensated voltage lead" charging method;

Figure 23 is a schematic diagram of the temperature rise and pack voltage vs. time relationship from the atmosphere during charging and discharging using the "fixed voltage lead" charging method;

24 is a schematic diagram of a battery type relationship for an M-series battery versus a battery capacity measured at Ah;

25 is a schematic diagram of a battery type relationship for battery power measured at W versus M-series batteries;

FIG. 26 is a plot of battery type relationship for normalized battery capacity measured at mAh / cm ² versus M-series batteries. FIG.

27 is a schematic diagram of a battery type relationship for normalized battery power versus M-series batteries measured at mW / cm ² ;

28 is a schematic diagram of a battery type relationship for a specific battery power versus M-series batteries measured at W / Kg; And

29 is a schematic diagram of a battery type relationship for a specific battery energy versus M-series batteries measured at Wh / kg.

As generally shown in FIG. 1, one aspect of the invention provides a mechanically improved rechargeable battery. BACKGROUND OF THE INVENTION In the field of rechargeable batteries, such as nickel metal hydride battery systems, there is a great deal of importance on the electrochemical aspects of batteries with less time and energy in improving the mechanical aspects of batteries, modules and pack designs.

We have studied design improvements in the mechanical aspects of rechargeable battery systems while looking at aspects such as energy density (both volume and gravimetric), strength, durability, mechanical aspects of battery performance and thermal management.

In accordance with this study, the inventors provide a mechanically improved rechargeable battery 1. The battery comprises: 1) a battery case (2) having a battery positive electrode terminal (7) and a battery negative electrode terminal (8); 2) at least one battery positive electrode 5 positioned in the battery case 2 and electrically connected to the battery positive electrode terminal 7; 3) at least one battery negative electrode 4 located in the battery case 2 and electrically connected to the battery negative electrode terminal 8; 4) at least one battery electrode separator (6) positioned between the positive electrode and the negative electrode in the battery case (2) to electrically insulate the positive electrode from the negative electrode but to enable chemical interaction thereof; And 5) a battery electrolyte (not shown) surrounding and immersing the positive electrode 5, the negative electrode 4, and the separator 6. The battery case 2 is in the form of a prism and has an optimum thickness to width to height aspect ratio.

As used herein, the term "battery" refers to an electrochemical cell comprising a plurality of positive and negative electrodes, all of which are separated by a separator and sealed in a case having both positive and negative terminals externally, all connected to respective terminals. Point.

As discussed below, this optimized aspect ratio allows the battery to have balanced optimal characteristics when compared to prismatic batteries that do not have such an optimized aspect ratio. In particular, the thickness, width and height are all optimized to allow for maximum capacity and power output and to eliminate harmful side effects. In addition, this particular case is designed to allow for expansion in such a direction that can be easily supplemented by having external mechanical compression in the direction. The inventors have found that the optimal electrode thickness to width ratio is between about 0.1 to 0.75 and the optimal height to width ratio is between 0.75 to 2.1. Specific battery examples and their electrode height to width ratios are shown in Table 1 below.

Table 1

Battery type Height (mm) Width (mm) Rain (H / W) L 140 75 1.87 M 187 91 2.06 M-20 167 91 1.84 M-40 147 91 1.62 M-60 127 91 1.40

It should be noted that even within the optimum ratio range, there are also secondary optimal ranges that depend on the desired characteristics of the battery. 24 to 29 show how the different height to width aspect ratios of the M series batteries (shown in Table 1) provide various optimal effects depending on the specific characteristics desired. 24 and 25, which are schematics of the battery power versus battery type relationship measured at battery capacity and W at Ah, respectively, show that M cells are superior in terms of maximum capacity and power. However, as can be seen in FIGS. 26 and 27, which are the schematics of the normalized battery capacity measured at mAh / cm ² and the battery power versus battery type relationship measured at mW / cm ² , if capacity and power are normalized within the electrode range, If so, the M-40 cell is the best. Further, if the specific power of the battery is determined, the M-40 cell is also superior, as shown in Figure 28, which is a schematic diagram of the specific power versus battery type relationship of the battery measured at W / Kg. Finally, if the specific energy of the battery is important, the M-20 cell is superior, as shown in Figure 29, which is a schematic of the specific energy versus battery type relationship of the battery measured at Wh / Kg.

In determining the optimal ratio, the inventors have found that if the height of the battery is too high (large), the electrode tends to break apart upon expansion and contraction. In addition, the internal electrical resistance of the electrode is increased, and the weight separation of the electrolyte solution to the bottom of the battery causes a problem that the top of the electrode is dried. This latter problem reduces the capacity and power output of the battery. On the other hand, if the electrode is too short, the capacity and power of the battery will be reduced due to the lower content of the electrochemically active material and the specific energy density of the battery will be reduced due to the change in ratio of the self-weight battery component to the electrochemically active component.

In addition, if the battery is too wide, the electrode tends to split upon expansion and contraction. In addition, there is a problem that the internal electrical resistance of the electrode, which reduces the capacity and power output of the battery increases. However, if the electrodes are too narrow, the capacity and power of the battery will be reduced due to the lowered content of the electrochemically active material and the specific energy density of the battery will be reduced due to the change in ratio of the self-weighted battery component to the electrochemically active component.

Finally, if the battery is too thick, a problem arises in which heat dissipation is inappropriate from the center electrode, which reduces battery capacity and power. In addition, the phenomenon of deflection and damage to the battery case is increased, and the overall expansion of the electrode bundle is increased in the thickness direction to form a gap between the positive electrode and the negative electrode, thereby reducing battery power and capacity. This excessive expansion of the electrode bundle must be compensated for by external mechanical compression. However, when the battery is too thick, excessive external pressure is needed to compensate for the expansion and fragmentation of the electrode. On the other hand, if the battery is too thin, fewer electrodes will be present in the battery, and therefore the capacity and power of the battery will be reduced due to the lower content of the electrochemically active material and the specific energy density of the battery will depend on the self-weight battery component versus electricity. Due to a change in the proportion of chemically active components.

The term "expansion" within the present invention encompasses both thermal and electrochemical expansion. Thermal expansion is due to the heating of the battery components by such a mechanism as described above and the electrochemical expansion is due to the changes that occur between different lattice structures in the charged and discharged state of the electrochemically active material of the battery.

The battery case 2 is preferably formed from a material which is thermally conductive, mechanically strong and rigid and chemically inert to the battery chemistry, such as metal. Alternatively, a polymer or composite material may be used as the battery case material. In selecting such materials, heat transfer aspects must be considered. As described in detail in US application Ser. No. 08 / 238,570, filed May 5, 1995, disclosed herein by reference, the results of experiments with a plastic case indicate that the internal temperature of the metal hydride battery with the plastic case is The temperature rises about 80 ° C. from the atmosphere after cycling at C / 10 to 120% of the capacity, while the stainless steel case rises only 32 ° C. As a result, it can be seen that a case made of a thermally conductive polymer or a composite material is preferable. Most preferably, the case is formed of stainless steel. It is desirable to electrically insulate the outside of the metal case from the surrounding environment by coating the outside of the metal case with a nonconductive polymer coating (not shown). An example of such a coating layer is an insulating polymer tape layer made of a polymer such as polyester. The mechanical strength of the polymer tape and its rough surface are just as important as the insulating properties. It is also preferably inexpensive, uniform and thin.

In addition, the inside of the battery case 2 must be electrically insulated from the battery electrodes. This can be accomplished by coating an electrically insulating polymer (not shown) on the interior of the battery case or by placing the battery electrode and electrolyte in an electrically insulating polymer bag (not shown) that is inactive to the battery chemistry. The bag is then sealed and inserted into the battery case 2.

In the preferred embodiment of the present invention shown in FIG. 2, the battery case is positioned with the upper case 3 and the electrodes 4 and 5 to which the battery positive electrode terminal 7 and the battery negative electrode terminal 8 are attached. It includes a battery case can (9). FIG. 3 shows the upper case 3 with an opening 13, wherein the battery positive electrode terminal 7 and the battery negative electrode terminal 8 are connected to the battery electrode 4 and through the opening 13. 5) and electrical transmission relationship. The diameter of the opening 13 is slightly larger than the outer diameter of the terminals 7 and 8 but smaller than the outer diameter of the seal 10 used to seal the terminals 7 and 8 in the upper case 3. The terminals 7 and 8 comprise a sealing lip 11 which helps to seal the terminals 7 and 8 to the upper part 3 of the case using the seal 10. Typically the seal 10 is a sealing ring. The seal 10 has a sealing lip slot 12 through which the sealing lip 11 of the terminals 7 and 8 is fitted. This slot 12 forms a good pressure seal between the terminals 7 and 8 and the case top 3 and when the terminals 7 and 8 are crimped into the case top 3 Hold the seal 10. Preferably the seal 10 is, for example, an elastic polymer such as polysulfone and is made of an insulating hydrogen impermeable material. The case top 3 also has a shroud 14 which surrounds each of the openings 13 and extends outward from the case top 3. The shroud 14 has an inner diameter somewhat larger than the outer diameter of the seal 10. The shroud 14 is wrinkled around the seal 10 and the sealing lip 11 of the battery terminals 7 and 8 to form a non-conducting portion between the terminals 7 and 8 and the upper case 3. Will form a pressure seal. The crimped terminal seal provides resistance to vibration as compared to threaded threads in the prior art. The case top 3, case can 9 and annular shroud 14 may be formed with 304L stainless steel.

4 shows the shape of a part of the battery according to the invention, in particular the battery terminals 7 and 8, which are pleat-sealed into the upper part of the case 3. As shown, the shroud 14 of the upper case 3 is wrinkle-sealed around the seal 10 which is alternately sealed around the sealing lip 11 of the battery terminals 7 and 8. It is obvious. In this way a pressure seal is formed which is resistant to vibrations.

The method of attaching the terminals 7 and 8 to the upper case 3 is a method of wrinkle sealing the terminals 7 and 8 to the upper case 3. This wrinkle sealing method has many advantages over the prior art. Wrinkle seals can be made quickly on high speed machines, resulting in direct cost savings. In addition, this method uses less material than the prior art to reduce the weight of the terminal, providing indirect cost savings. The higher surface area of this design also combined with a reduced weight of material allows for increased heat dissipation from the terminals. Another advantage according to the invention is that it is possible to form the battery case and other components from any malleable material and in particular does not require laser sealing, specific ceramics for metal seals, or other specific (and thus expensive) methods. . In addition, there is no need for the total number of components and the need for highly machined and precisely manufactured components.

The battery terminals 7 and 8 are typically formed of copper or copper alloy material and are preferably made of sheet metal nickel for corrosion resistance. However, any electrically conductive material compatible with battery chemistry may be used. The battery terminals 7 and 8 disclosed in the context of the present invention have a small annular thickness and have a diameter larger than that of the prior art. As a result, the terminal of the present invention becomes a very efficient heat emitter, which makes a significant contribution to the thermal management of the battery.

The terminals 7 and 8 also comprise a central opening 15 which is axially aligned. The central opening 15 acts as a multipurpose. Importantly, this opening serves to reduce the weight of the battery. The opening also functions as an opening to allow the external electrical connection device to be fitted in a frictional manner. Cylindrical or annular battery lead connectors are inserted through the opening 15 in a frictional manner to enable external electrical connection to the battery. Finally, the opening serves as a pressure outlet for discharging excessive pressure from the inside of the battery. The opening 15 may extend in part through the terminal (if only functioning as a connector socket) or entirely through the terminal (if functioning as a connector socket including a pressure outlet).

When at least one of the terminals 7 and 8 includes a pressure outlet for discharging the internal pressure of the battery to the ambient atmosphere, the outlet may be attached to the axial opening in the terminal (see FIG. 5). . Most preferably the pressure outlet 16 comprises: 1) an outlet housing having a hollow inner region 21 which is gas-transmitted with the surrounding atmosphere and the interior of the battery case through the openings 15, 18 and 23. 17); 2) located in the hollow inner region 21 and sized to seal the axial opening 16 and having a seal slot 20 on the opposing surface of the axial opening 16; A pressure relief piston 19; 3) an elastic body which is formed to be capable of inserting almost one surface portion of the thread so as to be mounted in the thread slot to expose the surface portion of the uninserted thread, and the insulating thread (not shown); And 4) a compression spring 22 which causes the pressure relief piston 19 to compress the seal in the seal slot 20 and blocks the axial opening 18 in the terminals 7 and 8. . See US Pat. No. 5,258,242, issued November 2, 1993, which is incorporated by reference, and entitled " Electrochemical Cell Having Improved Pressure Vent ". In other words, the elastic and insulating yarn is preferably formed of a hydrogen impermeable polysulfone material. In addition, since the battery cans are generally rated at about 150 pounds at most per square inch, the outlet vents release internal pressure above about 120 pounds per square inch to ensure battery condition.

In addition to the resealable outlet as described above, other types of outlets can be used in the battery according to the invention. In particular, bursting discs, pressure plugs and partition outlets can be used. One such barrier rib outlet is disclosed in US Pat. No. 5,171,647, disclosed below by reference. It is also preferred that the pressure outlet is located in the hollow battery terminal, but the outlet can be formed anywhere on the top of the battery in its protective housing or can only be attached to an opening in the top of the battery case.

Another embodiment of the battery terminal is illustrated in FIG. 6 showing the terminals 7 and 8, in which an external battery lead connection device 24 can be fitted in a frictional manner. The connection device 24 is attached to an external battery lead 25. The lead 25 is a solid bar; Metal ribbons; Single or multiple stranded wires; Or any form generally known in the art, such as braided high current battery cables (as described above). Preferably, the lead connector 24 is a hollow annular barrel connector fitted in a frictional manner in the axially aligned central opening 15 of the battery terminals 7 and 8. The lead connector 25 is supported in the battery terminals 7 and 8 via the barrel connector web 26. Solid barrel connection devices are US Patent Nos. 4,657,335, dated April 14, 1987, and March 29, 1988, US Pat. No. 4,734,063, entitled "Radially Resilent Electrical Socket", each patented by Koch et al. The disclosure is described below by reference.

If desired, the embodiments of FIGS. 5 and 6 can be combined into one embodiment that incorporates the pressure outlet 16 and the external battery lead connection 24. In addition, a ruptured disc (ie, a non-resealable means for releasing excessive pressure) may be included instead of or in addition to the pressure outlet.

The pleated sealing terminal and the upper case are preferred embodiments according to the present invention, but other types of terminals and thus other types of upper case may be used. In particular, a screw may be used on the terminal that engages the seal in the form of an O-ring. In general, any known sealed terminal can be used if it can have the operating pressure of the battery and can withstand the electrochemical environment of the battery.

Any battery system would benefit from improvements in the battery, module and pack structure according to the invention, or it is preferred that the positive electrode is formed from nickel hydroxide and the negative electrode is formed from a hydrogen absorbing alloy. Preferably, the negative electrode material is an Ovonic metal-hydride alloy (ie, US Application No. 08 / 259,793, filed June 14, 1994 and US Patent No. 5,407,781, April 18, 1995 (both) Disordered multi-component metal hydride alloys, as disclosed in the entirety of the disclosure). The electrode is also separated by a nonwoven, felt nylon or polypropylene separator and the electrolyte is an alkaline electrolyte containing, for example, 45 wt /% potassium hydroxide. Such separators are disclosed in US Pat. No. 5,330,861, the contents of which are incorporated by reference.

Ni-MH batteries in consumer applications on the market used paste metal hydride electrodes to obtain sufficient gas reburn rates and to protect the base alloy from oxidation and corrosion. Such paste electrodes generally comprise an active material powder mixed with an active material powder and a plastic binder and other nonconductive hydrophilic materials. This process has the unintended consequence of significantly reducing the thermal conductivity of the electrode structure compared to the structure of the present invention consisting of 100% conductive active material compressed on a conductive substrate.

In a sealed prism Ni-MH battery according to the present invention, the heat increase generated during overcharging is avoided by using a cell bundle of thermally conductive metal hydride electrode material. This thermally conductive metal hydride electrode material contains metal hydride particles in intimate contact with each other. Oxygen gas generated during overcharging is combusted to generate moisture and heat on the surface of these particles. In the present invention, this heat extends along the thermally conductive negative electrode material to the current collector and then to the surface portion of the case. The thermal efficiency of the thermally conductive metal hydride electrode material bundle is further increased if the bundle of electrode material is in thermal contact with a battery case which is thermally conductive.

In the present invention, preferably, the thermally conductive metal hydride electrode material is prepared using sintering so that the Ni-MH particles have intimate thermal contact with each other; US Pat. No. 4,765,598; No. 4,820,481; No. 4,915,898; 5,507,761; 5,507,761; And US Application No. 08 / 259,793, the contents of which are disclosed by reference.

The positive electrode used in the present invention is formed of a nickel hydrogen material. The positive electrode is sintered as disclosed in US Pat. No. 5,344,728 (disclosed by reference), as well as nickel foam or nickel as disclosed in US Pat. No. 5,348,822 and its continuing application (disclosed by reference). It is attached to a fiber matte.

In a sealed Ni-MH battery through one aspect of the present invention, it will be appreciated that heat generation is particularly commercially desirable during overcharging and particularly high during rapid charging progression. It is worth noting that the heat generated during overcharging is due to the combustion of oxygen on the surface of the metal hydride electrode. Therefore, it is possible to use a thermally conductive metal hydride electrode in combination with a paste-treated positive electrode. This preferred embodiment is particularly useful for optimizing the specific energy, overall performance and cost of the battery. For further details on the use of sintered electrodes, see US Application No. 08 entitled “Optimized Cell Pack For Large Sealed Nickel-Metal Hydride Batteries,” filed May 5, 1994, which is incorporated herein by reference. See / 238,570.

As shown in FIG. 2, each of the electrodes 4 and 5 forming the electrode stack has an electrical connector tab 27 attached thereto. This tab 27 is used to move the current formed in the battery to the battery terminals 7 and 8. The tab 37 is electrically connected to the terminals 7 and 8 with a projection 28 for such attachment. Alternatively, the protrusions 28 can be used to electrically and physically connect the terminals 7 and 8 and the electrode tab collector comb 29. As shown in FIG. 7, typically, the comb 29 is electrically conductive comprising a plurality of series of electrode tab collection slots 30 supporting the electrode tabs 27 by friction, welding or soldering. It is with. 7 also shows the battery terminal connector opening 31 in the tab collection comb 29. The battery terminal welding / soldering lip 28 is pressurized into the opening 31 to be soldered or welded to the required or desired portion. The comb 29 provides a connection with resistance to vibration for transferring electrical energy from the electrodes 4 and 5 to the terminals 7 and 8. The comb 29 has a higher resistance to vibrations than the conventional method of bolting the collection tab 27 to the bottom projections 28 of the terminals 7 and 8. The conventional method of connecting the tabs 27 to the terminals 7 and 8 also requires longer tabs and cases (cases with larger head space). This increases the overall weight and size of the battery. Removal of the bolts significantly reduces the head space portion of the battery, resulting in an increase in the energy density of the volume. The comb 29 and the battery terminals 7 and 8 are preferably formed of copper or a copper alloy, and more preferably nickel coated with corrosion resistance. However, they can be made with electrically conductive materials that are compatible with the chemistry of the battery. Although the electrode tab collector comb is an ideal means of attaching the electrode tab to the battery terminal, other conventional means such as bolts, screws, welding or soldering may also be used, and therefore the present invention is limited to the above preferred embodiment. It doesn't work.

The battery positive and negative electrodes 4 and 5 may be formed in the battery case 2 so that each of the electrical collection tabs 27 is formed at positions opposite to each other on the top of the case. That is, all negative electrode electrical collection tabs are arranged on one side of the battery and all positive electrode electrical collection tabs are arranged on the opposite side of the battery. Preferably, the battery positive electrode and the negative electrode have a notched corner (not shown) in which electrode electrode collecting tabs of opposite polarities are located, thereby preventing a short circuit between the electrodes and removing unused self-weight electrode material. Such a short circuit occurs when the electrical collection tab of an electrode is twisted or has sharp protrusions that can penetrate the electrode separator and short the electrodes of opposite opposite polarities. The self-weighted electrode material is generated by the combination of the inactive electrode and the active material because the inactive electrode does not neighbor the counter electrode material.

Although the battery may have a predetermined number of electrodes depending on the thickness, the battery preferably has 19 positive electrodes and 20 negative electrodes arranged alternately in the case. That is, the electrode alternately arranges the positive electrode and the negative electrode while placing the negative electrode outside the electrode stack. This construction avoids short circuits that can occur when the battery is under external mechanical compression. That is, if there is a positive electrode and a negative electrode on the outside of the electrode stack, there will be a possibility that the electrode will form an electrical short circuit through the metal battery case when the battery is subjected to external mechanical compression.

It is necessary to have an electrode separator 6 surrounding a set of said battery electrodes (i.e., a separator around the negative electrode or only a separator around the positive electrode), but it is necessary to have a separator 6 surrounding each set of electrodes. Better than Data show that the use of double separators can reduce the self-emission level of the battery. In particular, the charge retention increased to about 80% after two days for a battery with a single separator or about 93% after two days with a battery with a double separator. The separator 6 is a typical polypropylene separator material well known in the art. They have a grain or slot of directionality caused by machine formation and the grain or slot of the polypropylene separator material is preferably aligned vertically along the electrode. This constant directionality reduces friction, and catching and attaching the grain or slot of one separator to the grain or slot of a neighboring separator can lead to breakage of the electrode, thus preventing such catching and attachment during mechanical compression or during expansion of the electrode. Prevent.

In another aspect according to the invention, the invention relates to an improved high power battery module, in particular defined as two or more electrically interconnected cells, shown below in FIGS. Module "). To be useful, the battery in the module must be compact, portable and mechanically stable when used. In addition, the materials used in the construction of the battery module (except the battery itself) should not add excessive self weight or energy density to the module. In addition, since the battery generates a large amount of heat during cycling, its constituent material must be thermally conductive and small enough not to prevent heat from moving far away from the battery and heat sinking and trapping within the battery and module. It must be small enough not to act as trapping heat. In order to meet these requirements, the present invention has led to the design of an improved high power battery module according to the present invention.

The battery module 32 of the present invention comprises: 1) a plurality of individual batteries 1; 2) a plurality of electrical interconnections (25) connecting the individual batteries (1) of the module (32) to each other and providing means for electrically connecting the separate battery modules (32) to each other; And 3) battery module bundling / compression means (disclosed below). The batteries are bundled together under external mechanical compression (the advantages of such compression will be described below) within the module bundling / compression means, which are thus fixed and moved around when mechanical vibrations occur during transport or use. Or stops moving.

Although a certain number of batteries are bundled into one module, generally two to fifteen batteries per bundle are bundled. The battery module 32 is typically a bundle of prismatic batteries of the present invention. Preferably the batteries are bundled so that they all have a certain orientation in the same manner as each battery with an electrical terminal located on top thereof (see FIGS. 8 and 12). The battery is oriented in a direction within the module such that the narrowest side faces the face of the module and its widest side (when the battery expands) is positioned adjacent to the other battery of the module. do. This arrangement allows for expansion in only one direction within the module, which is desirable.

The battery 1 is optimized to provide separate internal compression on the battery electrode within each battery to balance the external pressure due to the expansion of the battery components and to reduce the distance between the positive and negative electrodes to increase overall battery power. Bundled together in said module bundling / compression means under external mechanical compression.

As mentioned above, the expansion of the prism battery preferably used in the present invention takes place in a single direction, so that compression is required in this one direction to cancel such expansion (see compression direction arrow 33). If not offset, this expansion creates more space than the optimal separation space between the electrodes and the bending and warping of the outer casing of the battery, eventually reducing the battery power. In addition, overcompensation for such expansion is also useful to some extent. In other words, to some extent, excessive compression actually increases (reduces internal resistance) the power output of the bundled battery. However, excessively excessive compression results in rupture and short circuit of the electrodes in the battery. The increased power due to overcompression is believed to result from the compression of the positive electrode, which weakens its resistance by reducing the resistance due to contact between active material particles in the electrode and the electrode current collector. In addition, the compression of the separator allows the formation of shorter ion passages between the positive and negative electrodes, thereby reducing the interplate space between the positive and negative electrodes of the battery, which reduces the electrolyte resistance therebetween.

17 shows the correlation between module compression versus battery resistance. Modules with end plates (described below) are compressed using different amounts of force and the internal battery resistance (related to total power output and charging efficiency) and battery thickness are measured. As can be seen from FIG. And an optimum compression range is formed for these modules between 170 psi (about 1100-2600 pounds for an area of about 100 cm ² ) and about 50 to 180 psi (about 800 to 2800 pounds for an area of about 100 cm ²⁾ . The functional range is formed for these modules. For batteries used in such modules, it will be apparent that compression above the upper limit of the functional range and compression below the lower limit increase the internal resistance of the battery, thereby reducing power. Although the optimum and functional compression ranges appear differently for batteries of different sizes, the resistance versus compression relationship for these different sizes of batteries is similar in that both have the function and optimum compression range for proper cell performance.

1) the required compression run is possible; 2) to perform the required mechanical functions of the module bundling / compression means resistant to vibration; And 3) finding structures with the lightest weight / design possible. According to the present invention, the battery module is formed along four sides of the battery module 32 under high mechanical pressure and welded at four corners of the module to form a band 34 around the outside of the battery module. Preferably stainless steel). Preferably the welded metal bar 34 is located centrally between the top and bottom of the battery module, where the expansion occurs most vigorously. Battery compression in areas that do not include the electrode stack is not useful as such compression does not compress the electrode. In fact, this compression can be detrimental as it causes a short circuit of the electrode to the metal can via an internal insulator.

Although not readily seen in the figures, it should be noted that the thickness and width dimensions at the upper and lower borders of the battery case are about 0.5 and 1.0 mm smaller than the overall thickness and width dimensions. This reduction in size ensures that all compressive forces are transferred only to the electrode plate stack and separator.

The welded metal bars 34 comprise a set of two or three bars located centrally between the top and bottom of the battery module. If three sets of bars are used, the first set of bars is halfway between the top and bottom of the battery module, and the second set of bars is then between the first set of bars and the top of the battery module. And a third set of bars is located between the first set of bars and the bottom of the battery module. This allows for uniform compressive dispersion and relieves stress on the bar set. This compression dispersion also reduces the module's own weight by allowing the use of the smallest and lightest metal bars.

In another preferred design of the invention a metal end plate 35 is used on the end of the module. The stainless steel bar is formed along the face of the battery module, welded at the corner of the module and formed of rectangular metal tubing (45 in FIG. 9) to replace the end bar to properly replace the end plate 35. I support it. This design helps to distribute the compressive force. The end plate 35 is preferably formed of aluminum and has ribs 36 projecting perpendicularly to the plane of the end plate 35, increasing the strength of the plate 35 and making the material to be used lighter ( One embodiment of such an end plate is shown in FIGS. 13A and 13B, another embodiment is disclosed in US Application No. 08 / 238,570, filed May 5, 1995, which is incorporated by reference). When the end plate 35 has such ribs 36, slots (not shown, but see FIG. 9) need to be formed in such ribs to accommodate the rectangular metal tubing 45. Preferably the end plate 35 may be thermally isolated or thermally isolated from the battery bundled in the module 32 by a thermal insulating material such as a thermally insulating polymer layer or polymer foam. This insulation can prevent irregular battery temperature distribution within the module that may be caused by the action of the cooling fins of the rib 36 of the end plate 35. However, the ribs 36 allow the end plates 35 to neighboring batteries 1 to increase heat dissipation for the batteries 1 in the module 32 by a heat sink if necessary.

Each module 32 separately includes a module spacer 37 (see FIGS. 11 and 12) that supports the module 32 some distance from the other module 32 and the battery pack case. These module spacers 37 are formed on the top and bottom of the module 32 to form corners of the battery 1 in the module 32 and the electrical interconnects 25 and terminals of the battery 1. It protects against (7 and 8). More importantly, tabs 38 on each side of the spacer 37 support the module 32 away from the optimum distance. Preferably, the spacers 37 are formed of a lightweight, electrically nonconductive material, such as a durable polymer. In addition, it is important in the overall energy density that the spacer contain as small and light material as possible to perform the required function.

Batteries and modules according to the invention are preferably electrically interconnected by conductive leads 25 (see FIGS. 8 and 9) which provide low resistance passages between them. The total resistance, including lead resistance and contact resistance, should preferably not exceed 0.1 mohm. The lead is secured to the terminal by screws, bolts or preferably socket barrel connectors 24 as described above. The electrical interconnect 25 of the battery module 32 according to the invention is preferably a braided cable interconnect (see FIG. 14), which provides high heat dissipation and flexibility for the design / structure of the module. do. That is, the braided cable interconnect 25 performs two important functions within the battery module of the present invention (in addition to the general function of transferring electrical energy from the battery). First, the braided cable 25 is flexible to facilitate expansion and contraction of the individual battery 1, resulting in a change in distance between the terminals 7 and 8 of the individual battery 1 in the module 32. To come. Secondly, the braided cable interconnect 25 has a much higher surface area than a solid cable or bar. This is due to the fact that an electrical interconnect starts inside the battery and runs through the electrodes 4 and 5, the electrode tab 27, and the battery terminal 7 to connect the electrical interconnect 25. It is important in the thermal management of batteries, modules and packs according to the invention as it is part of the heat passage through it. Therefore, the higher the surface area of the electrical interconnect device 25, the greater the heat dissipation of the battery 1 and the better its thermal management. Preferably the braided cable electrical interconnect 25 is formed of copper or a copper alloy, preferably coated with nickel to have corrosion resistance.

Another aspect (shown in FIG. 15) of the present invention is a fluid cooled battery pack system (as used below, the term "battery pack" or "pack" refers to two or more electrically interconnected battery modules). It is in mechanical design. It should also be noted that during cycling of the battery, the battery generates a large amount of excess heat. This is especially true during charging of the battery. This heat may harm the battery system and even cause paralysis. Some of the negative characteristics that a battery system may experience when doing no or inadequate thermal management include: 1) low capacity and power; 2) increased self discharge; 3) unbalance in temperature between the battery and the module, resulting in battery misuse; And 4) reduction in battery cycle life. Therefore, it is clear that proper thermal management is necessary to use the battery pack system in an optimal state.

Some factors to consider in thermal management of battery pack systems are: 1) All batteries and modules must be kept below 65 ° C to prevent permanent damage to the battery; 2) all batteries and modules must be kept lower than 55 ° C. to obtain at least 80% of the battery's rated performance; 3) All batteries and modules must be kept below 45 ° C to have maximum cycle life; And 4) The temperature difference between individual batteries and battery modules should be kept below 8 ° C for optimal performance. A feature of the present invention is that the temperature difference between batteries can be controlled to about 2 ° C or less.

Thermal management of the battery pack system must provide adequate cooling to ensure optimum performance and durability of Ni-MH batteries under a wide variety of operating conditions. Atmospheric temperatures in the United States range from 49 states to at least -30 ° C to 43 ° C. It is necessary to maintain the battery in the optimal battery performance range from about −1 ° C. to 38 ° C., while attaining the operational utility of the battery pack in this ambient temperature range.

Nickel metal hydride batteries show a decrease in charging efficiency at very high temperatures of 43 ° C. or higher due to problems caused by oxygen generation in the nickel positive electrode. To avoid this inefficiency, the battery temperature during charging should ideally be kept below 43 ° C. Nickel metal hydride batteries also exhibit poor power performance at temperatures below -1 ° C due to performance degradation at the nickel negative electrode. To prevent this loss of power, the battery temperature must be maintained above about -1 ° C during discharge.

As mentioned above, in addition to the performance degradation at high and low temperatures, adverse effects may occur due to the temperature difference between the batteries in the module during charging. If the temperature difference is large, an imbalance occurs in the charging efficiency of the battery, in which the battery alternately causes an unbalance in the charging state, resulting in a decrease in capacity, and frequently causing severe overcharge and overdischarge phenomenon. In order to avoid this problem, the temperature difference between the batteries should be controlled to 8 ° C. or lower, preferably 5 ° C. or lower.

18 shows the relationship between battery specific energy and battery temperature measured in Wh / Kg of a nickel metal hydride battery according to the present invention. As shown, the specific energy of the battery begins to drop above about 20 ° C. and suddenly drops above about 40 ° C. 19 shows the relationship between battery specific power and battery temperature measured in W / Kg of a nickel metal hydride battery according to the present invention. As shown, the specific power of the battery rises with temperature but becomes stable above about 40 ° C.

Another factor in the design of a fluid cooled battery pack system is the mechanical part. For example, battery and module packing densities are as compact as possible to prepare for space in final production. Separately, certain materials added to the battery pack system for thermal management do not directly affect the electrochemical capacity of the battery itself, ultimately reducing the overall energy density of the battery system. To meet this need, the inventors have designed the fluid cooling battery pack system according to the present invention.

In the most basic form of the invention (the embodiment shown in FIG. 15), the fluid cooling battery pack system comprises: 1) a battery pack case having at least one coolant inlet 41 and at least one coolant outlet 42. 40; 2) located in the case 40 so that the battery module 32 is spaced apart from the wall of the case and is spaced apart from other battery modules 32 in the case 40 and along at least one surface of the bundled battery, At least one battery module that is convection from the battery to the coolant and forms a coolant flow channel 43 having a maximally efficient size that is conductive and allows maximum heat transfer through the radioactive heat transfer device (32); And 3) allowing the coolant to flow into the coolant inlet means 41 of the case 40 to flow through the coolant flow channel 43 and to be discharged through the coolant outlet means 42 of the case 40. At least one coolant transfer means 44 is provided. Preferably, the battery pack system 39 has a plurality of battery modules 32, generally 2 to 100 modules, arranged in a two-dimensional or three-dimensional matrix structure in the case. Such a matrix structure allows the coolant to flow over at least one surface of each of the battery modules 32 while having a high packing density.

Preferably, the battery pack case 40 is formed of an electrically insulating material. More preferably, the case 40 is formed of a lightweight, durable, electrically insulating polymer material. These materials must be electrically insulated so that they will not short circuit, even if the case is in contact with the battery and module. In addition, the material must have light weight to increase the overall pack energy density. Finally, the material must be durable to withstand repeated use of the battery pack. The battery pack case 40 is a specific fluid port and is preferably a simple hole in the battery pack case 40 through which one or more coolant inlets 41 and outlets 42 enter and discharge cooling air. It includes.

The fluid cooled battery pack system 39 is designed to use an electrically insulated coolant that is a gas or a liquid. Preferably the coolant is a gas and more preferably the coolant is air. When air is used as the coolant, the coolant delivery means 44 is preferably a forced air blower, more preferably a blower that provides an air flow rate of 1 to 3 SCFM air per cell in the pack.

The blower need not continuously provide cooling air into the battery pack, but need to be controlled to maintain the battery pack temperature in an optimal state. Fan control to turn the fan on / off, preferably fan control for controlling the speed of the fan, is required for efficient cooling during charging, driving and idle stand. Typically, cooling is most important during charging, but also during operation. The fan speed is controlled based on the temperature difference between the battery pack and the atmosphere, as well as in order not to cool the battery while the battery is cooled or to provide extra cooling when the battery is near the upper limit of the ideal temperature range. Controlled based on temperature. In nickel metal hydride batteries, a fan is also needed at rest time after charging. Intermittent cooling is needed to provide efficient cooling in this condition, resulting in net energy savings by maintaining the self-discharge rate below the fan's power consumption. Typical results (FIG. 16) show a fan at 2.4 hours after cooling after the initial charge. Typically the normal fan control process (discussed below) works well in this scenario. The use of efficient fans allows for efficient cooling when needed without sacrificing fan power over time to maintain high energy efficiency. The use of more efficient fans is beneficial in maintaining the optimum pack temperature, which allows for the optimization of pack performance and life.

If the maximum temperature of the battery is above 30 ° C and the ambient temperature is lower than the maximum temperature of the battery (preferably above 5 ° C), an example of the fan control process is that the fan is driven to drive more cooled air into the cooling channel. Circulate

Another useful fan control algorithm operates fans at various ratios according to certain criteria. These criteria are: 1) battery maximum temperature; 2) ambient temperature; 3) current battery usage (i.e. charging, charging standby, high temperature, high discharge depth during operation, standing, etc.); and 4) the voltage of the auxiliary battery powering on the cooling fan. The algorithm is shown in Table 2.

TABLE 2

IF (Tbatmax> = 25 ° C THENPWM = Minspeed + 5 ^* DeltaPWM = MIN (PWM, Maxspeed) ELSE PWM = MinspeedIF PWM <30 THEN PWM = 0IF (Vauxbat <13) and (PWM> = 30) THEN PWM = 30

In the algorithm of Table 2:

"Tbatmax" is the maximum module temperature;

"Tamb" is the ambient air temperature;

"Delta" is Tbatmax-Tamb (negative value assumed to be '0')

"PWM" is a fan pulse width modulation (PWM) rate control signal (0 = OFF, 100 = FULL POWER);

"Vauxbat" is the auxiliary fan battery voltage;

"Minspeed" is the minimum fan speed, 30% PWM if charging, charging standby, high temperature, high discharge dodging during operation; Or 0% PWM; And

"Maxspeed" is the maximum fan speed, 100% PWM, or 65% PWM if charging or waiting for charging.

The flow rate and pressure of the cooling fluid need to be sufficient to provide sufficient heat capacity and heat transfer to the pack. The flow rate of the fluid is required to be sufficient to remove the steady state of heat at the maximum expected sustained heat generation rate, resulting in an allowable temperature rise. In a typical Ni-MH battery pack, it has 5 to 10 W per cell generated during overcharge (maximum heat generation), and a flow rate of 1 to 3 CFM air per cell is simply needed to provide adequate cooling based on the heat capacity of the air. This results in an allowable temperature rise. Fans in the form of radiant blowers are used to provide the most effective airflow for thermal management. This is because the air pressure generated by these fans is higher compared to the air pressure generated by the fans in the axial direction. In general, a pressure drop of at least 0.5 "water is required at the operating point of the fan installed in the pack. To produce this pressure drop at high flow rates it is generally necessary to require a static pressure capacity of a fan of 1.5" to 3 "water. do.

In addition to using a fan to cool the battery pack when it is hot, the fan can heat it when it is too cold. In other words, if the battery pack is below the minimum optimum temperature and the atmosphere is warmer than such a battery pack, the fan is turned on to bring the warm atmosphere into the battery pack. The heat energy of the warm air then moves to the battery pack to warm the battery pack to at least the lower limit of the optimal temperature range.

One or more coolant conveying means 44 are formed at the coolant inlet 41 to introduce fresh coolant through the coolant flow channel 43 and from the coolant outlet 42 into the battery pack case 40. Can be. Alternatively, one or more coolant conveying means 44 are formed at the coolant outlet 42 and outflow the heated coolant from the battery pack case 40 so that fresh coolant passes through the coolant inlet 41. It flows into the battery pack case 40 and flows through the coolant flow channel 43.

The coolant flows in parallel to the longest coolant flow channel 43 (ie in the longitudinal direction of the battery module), or in a direction perpendicular to the longest coolant flow channel 43 ( Ie in the height direction of the battery module). It should be noted that the coolant is heated because the coolant recovers excess heat from the battery as it flows through the cooling channel 43. Therefore, it is preferable that the flow rate flows perpendicular to the longest size coolant flow channel 43. This is because as the coolant is heated, the temperature difference between the battery and the coolant is reduced and consequently the cooling rate is also reduced. Thus, the total heat dissipation is lowered. To reduce this phenomenon, the coolant flow passage must be shorter of the two, ie along the height of the battery.

While air is the most preferred coolant (which is readily available and easy to transport in and out of the case), other gases and liquids may be used. In particular, freon or ethylene glycol, as well as other commercially available fluorocarbons and non- Liquid coolants such as fluorocarbon base materials can be used. When such gas and liquid are used as coolant, the coolant conveying means 44 is preferably pumped. When using a coolant other than air, the coolant conveying means preferably comprises a coolant return line attached to the coolant outlet 42 for recirculating the coolant heated by a coolant retainer (not shown). From the coolant return line, the coolant is transferred to a coolant heat exchanger (not shown) to extract heat and finally re-delivered to the coolant pump 44 for recooling use of the battery pack 39.

The optimal cooling flow channel width has many factors. Some examples of these factors are the number of batteries, the energy density and capacity of the battery, the rate of charge and discharge of the battery, the direction, speed and volume flow rate of the coolant, the heat capacity of the coolant, and the like. Apart from these factors, it has been found that it is important to design the cooling channel 43 that obstructs or delays the amount of cooling fluid as it passes between modules. Ideally, the delay of the flow is predominantly due to friction with the cell cooling surface, which results in a flow reduction of 5-30% of the flow volume. When the spacing between modules forms a major flow constraint in the cooling fluid treatment system, this results in uniform and generally the same amount of cooling fluid flow in the spacing between all modules, resulting in the same cooling and uneven flow between the modules. To reduce the effects of other flow constraints (such as inlet or outlet). Moreover, the same area of each cell is exposed to the cooling fluid with similar speed and temperature.

The battery module is formed for efficient cooling of the battery cell by minimizing the velocity of the cooling fluid in order to obtain a high coefficient of heat transfer between the cell surface and the cooling fluid. This is accomplished by narrowing the space between the modules to such an extent that the cooling fluid flow begins to decrease but the fluid velocity still increases. The narrower space also helps to increase the coefficient of heat transfer as the shorter distance for heat transfer in the cooling fluid raises the cell to the degree of fluid temperature change.

The width of the optimal coolant flow channel is determined by the length of the flow passage in the flow direction as well as the area of the coolant flow channel on a plane perpendicular to the coolant flow. The optimal space depends somewhat slightly on the fan characteristics. The width of the coolant flow channel 43 with respect to air is between about 0.3-12 mm, preferably between 1-9 mm, more preferably between 3-8 mm. For vertical air flow through a 7 inch high module, the optimal average module spacing (width of the coolant flow channel 43) is about 3-4 mm (105 mm centerline spacing). For longitudinal horizontal air flow across four modules 16 inches long in a row of 64 inches away, the optimal average module spacing (width of the coolant flow channel 43) is about 7-8 mm (109). mm centerline spacing). The spacing between modules somewhat closer at the ends of these rows will result in higher air flow rates, which in turn will compensate for the lowering air temperatures by bringing a higher heat transfer coefficient. A secondary inlet or series of inlets along the horizontal cooling flow passage may also be used as a means for introducing additional coolant to make the heat transfer between the battery cells and the coolant more uniform along the entire flow passage.

It should be noted that the term “centerline spacing” may sometimes be used in a similar sense to the coolant flow channel width. This is because the width of the coolant flow channels cited above is an average number. The reason for such an average measurement is that the faces of the battery module forming the flow channel 43 are not evenly planar, the bands bundling the modules together, and the faces of the battery itself are determined by the width of the actual channel. Because it depends. Therefore, it may sometimes be convenient to describe the width, i.e., the centerline width, for the spacing between the centers of the individual modules that vary for different size batteries. Therefore, it is generally more useful to represent the average channel width applied to the battery module regardless of the actual battery size used in the present invention.

20 and 21 are plan views showing the relationship between the width of the coolant flow channel (ie, the centerline interval) to the coolant volume flow rate, the maximum coolant rate ratio and the maximum heat transfer rate for the vertical and horizontal coolant flows, respectively. These graphs use air as the coolant and assume rapid flow and 30% external constraints. As shown, there is clearly an optimal spacing that depends on the flow direction of the coolant. It is most efficient to operate within an optimum heat transfer range of ± 10%, but if necessary, the system can operate outside this range by increasing the volumetric flow rate of the coolant. In this figure, the curve indicated by the square symbol (■) represents the volume flow rate of the coolant (air) and can be read from the left coordinate, while the curve indicated by the triangle symbol (▲) and diamond symbol (◆) is maximum. The heat transfer rate and the maximum coolant flow rate ratio are respectively shown and can be read from the right coordinate.

In order to maintain the proper spacing of the modules within the pack case and to have electrical separation between the modules, each module is the module 32 at an optimum distance from the other module 32 and the battery pack case 40. And a coolant flow channel spacer 37 for supporting the coolant flow channel 43. As noted above, the coolant flow channel spacer 37 is preferably formed at the top and bottom of the battery module 32 such that the corners of the module 32, the battery terminals 7 and 8, and the electrical interconnection. It is to protect the connection device (25). More importantly, tabs on each side of the spacer 37 support the module apart at optimal intervals. Preferably, the spacers 37 are formed of a lightweight, electrically nonconductive material, such as a durable polymer. In addition, it is important for the overall pack energy density that the spacer contain as small and light material as possible to perform the required function.

As noted above, the Ni-MH batteries work best in certain temperature ranges. While the coolant system may maintain the battery pack system according to the present invention at an operating temperature lower than the high temperature range of the optimum temperature range (when the standby temperature is warmer than the battery or warmer than the low temperature range of the optimum temperature range, Sometimes, in order to operate above the low temperature range of such an optimum temperature range, there are still times when the battery pack system is colder than the lower limit of the optimum temperature range. There may be a need to provide variable thermal isolation for the module anyway.

In addition to the cooling system described above, another method of thermally controlling the battery pack system according to the present invention is the use of a heat dependent charging method. Thermally dependent charging allows efficient charging under various ambient temperatures. One way is to charge the battery in a continuously updated temperature dependent voltage lead that is supported until the current drops to a certain value and a particular charge input is applied in a constant current state. Another method involves a series of reduced constant current or constant power processes to a temperature compensated voltage limit prior to a particular charge input applied in a constant current or power state. Another method involves a series of reduced constant current or constant power processes terminated by the maximum rate of temperature rise prior to the particular charge input applied in the constant current or power state. Temperature-dependent voltage leads ensure uniform capacity over a wide range of temperatures and ensure charging with minimum temperature rise. For example, a fixed voltage charge lead results in a temperature rise of 8 ° C. when temperature compensated charging occurs at a temperature rise of 3 ° C. under similar conditions. The absolute limit temperature (60 ° C.) of the charging temperature is necessary to ensure that the battery avoids severe overheating that can occur if the charger and cooling system fail simultaneously. The detection of the rate of change of voltage with respect to time (dV / dt) on a pack or module basis causes the negative value of dV / dt to act as a charging terminator. This prevents excessive overcharging, acts as a separate safety limit, and improves battery operating efficiency.

An example of a temperature dependent charging method is shown in Table 3.

TABLE 3

1) Charge at full power until voltage lead ^{* 4} is reached. ^{* 1,2,3} 2) Reduce the current by 30% and charge until the voltage lead ^{* 4} is reached. ^{* 1,2,3} 3) Repeat step 2) above until current <5A. ^{* 1,2,3} 4) Complete charging at 5A constant current charge for 1 hour until recharge amperage is greater than 5Ah. ^{* 1,2,3} 5) Resume charging every 2 hours or every X hours (see equation below for X). ^{* 5} or resume charging if the battery module voltage falls below 15V, or resume charging if the battery voltage falls below the voltage lead minus an offset (e.g. 0.5V per module), or Float the battery to the voltage lead minus the offset. In all of the above cases, the maximum battery temperature should be below 50C before resuming charging. ^* 1) If the maximum battery temperature is above 40 ℃, the current should be limited to 10A. ^* 2) If the maximum battery temperature is above 60 ℃, stop charging.-If the maximum battery temperature drops below 50 ℃, resume charging. ^* 3) Limit full charge up to 95Ah for initial charge and up to 30Ah for resumption. ^* 4) Voltage lead = (16.65V-[0.024V / C] * Maximum battery temperature (° C)) * Module number ^* 5) For example, X = 20 ^* (1-Charge Minimum Allowed State (%)) ^{2 *} (60-max battery temperature)

22 and 23 show how the “temperature compensated voltage lead” charging scheme reduces the voltage rise during charging of the battery pack system. These figures show the relationship between the temperature rise of the battery pack and pack voltage versus time during pack charging and discharging. In FIG. 22 (time compensated voltage lead), the top curve represents the pack voltage and the bottom curve represents the pack temperature above atmospheric. FIG. 22 shows that at the end of the charging cycle, indicated by the peak of the voltage curve, the battery pack will have a temperature rise only 3 ° C. above the atmosphere. On the other hand, FIG. 23 shows a temperature rise of about 8 ° C. higher than the atmosphere when the “fixed voltage lead” charging scheme is applied. Here, the dotted line curve represents the pack voltage and the solid line curve represents the pack temperature. Therefore, it can be understood that most of the heat generated in conventional charging is removed by the "temperature compensated voltage lead" charging scheme.

As described above, in addition to having an upper limit on the battery operating temperature range of the present invention, it also has a lower limit. As also mentioned above, when the ambient temperature is higher than the battery temperature, the "cooling system" can be used as the heating system. However, if the battery pack temperature is low, the standby temperature will also be low and preferably much lower than the battery pack temperature. Therefore, there may be times when it is advantageous to thermally insulate a battery from the atmosphere during operation of the battery pack system. However, thermal insulation is not always necessary and may change rapidly, even in a very short time. Thus, the need for thermal insulation will be variable.

To meet these variable thermal insulation needs, the present invention includes means for providing variable thermal insulation. The variable thermal insulation means according to the invention can equally be used in individual batteries, battery modules and battery pack systems.

Most basically, the means provides variable thermal insulation to at least a portion of the rechargeable battery system that is most directly exposed to the ambient temperature condition to provide a temperature of the rechargeable battery system within a desired operating range in a variable standby state. Keep it.

To provide such variable thermal insulation, the present invention combines temperature sensor means, compressible thermal insulation means and means for compressing the compressible thermal insulation means in response to a temperature detected by the thermal sensor. The temperature sensor indicates that if the atmosphere is cold, thermal insulation is in the area required to insulate the range affected by the cold of the battery, module or battery pack system. When the atmosphere is warm, the temperature sensor allows the thermal insulation to be partially or wholly made such that the compressive insulation causes the insulation factor provided to the battery system to be partially or wholly removed.

The thermal sensor is an electronic sensor that provides information to a piston device that variably increases or decreases compression on a compressible foam or fiber insulator. Alternatively, (and more preferably in view of electrical energy utilization and mechanical reliability), the sensor and compression device may be combined in one mechanical device that performs variable compression on the thermal insulator in direct response to atmospheric thermal conditions. Can be. Such a combined sensor / compression device may be formed with a bimetallic material, such as a strip used in a thermostat. At low ambient temperatures, the bimetal device protects the battery system from cold atmospheric conditions by allowing thermal insulation to expand, but when the battery temperature or ambient temperature rises, the bimetal device reduces insulation to effect insulation from the battery system. Remove it.

The variable thermal insulator can be used across the entire battery, module or battery pack system, but need not always be so. The variable thermal insulator can only be effective when isolating problem parts of the system. For example, in the battery module and battery pack system according to the invention with ribbed end plates, it is only necessary to thermally insulate the ends of the modules most directly affected by low ambient temperatures. This standby state causes a large temperature imbalance between the batteries of the module (s), which results in poor performance of the module or pack system. By means of variable insulation on the temperature affected end (s) of the module (s), the temperature difference between batteries can be reduced or eliminated and the overall temperature of the module (s) can be controlled. Finally, the thermal insulator does not necessarily need to be in contact with the battery or module but may fall away from the module and leave a static air area near the battery or module that acts as an additional thermal insulator.

The foregoing disclosure is presented through the detailed embodiments described for a full disclosure of the invention, which details are to be interpreted without limiting the scope of the invention in the foregoing and the claims of the invention below. .

Claims (30)

A battery case having a battery positive electrode terminal and a battery negative electrode terminal; At least one battery positive electrode positioned in the battery case and electrically connected to the battery positive electrode terminal; At least one battery negative electrode positioned in the battery case and electrically connected to the battery negative electrode terminal; At least one battery electrode separator positioned between the positive electrode and the negative electrode in the battery case to electrically insulate the positive electrode from the negative electrode but to enable their chemical interaction; And Located within the battery case, the positive electrode, the negative electrode, and the battery electrolyte surrounding the battery electrode separator to be immersed, the battery case is characterized in that the prism form having an aspect ratio of the optimum thickness to width to height Mechanically improved rechargeable battery. The method of claim 1, And the battery case is thermally conductive and is formed of a mechanically strong and corrosion resistant material. The method of claim 2, And the prismatic battery case is formed of metal. The method of claim 3, wherein And the metal case is formed of stainless steel. The method of claim 1, And the case is formed of an upper case including the battery positive electrode and the battery negative electrode, and a battery case can in which the electrode is located. The method of claim 5, The case upper portion has an annular shroud defining an outer periphery of at least one opening through the upper portion and the terminal having a sealing lip around the terminal, wherein the terminal is pleated sealed into the annular shroud at the sealing lip. Mechanically improved rechargeable battery. The method of claim 6, And the case top, the case can, and the annular shroud are formed of 304L stainless steel. The method of claim 6, And a resilient insulating seal is located between the sealing lip and the annular shroud. The method of claim 8, And the resilient insulating seal is formed of a hydrogen impermeable polysulfone material. The method of claim 1, And a pressure outlet for releasing the internal pressure of the battery to the ambient atmosphere. The method of claim 10, And the pressure outlet is attached to an opening in the interior of at least one of the terminals. The method of claim 10, The pressure outlet; An outlet housing having a hollow inner region portion in which gas is communicated with the surrounding atmosphere and the inside of the case through the opening; A pressure relief piston located in the hollow inner region and sized to seal the axial opening and having a sealing slot on an opposing surface portion of the axial opening; An elastic body mounted in the sealing slot which is formed to be able to insert almost the surface portion of the sealing portion and leaves the surface portion of the sealing portion which is not inserted, exposed; And And a compression spring for causing said pressure relief piston to compress said seal in said seal slot and to block said axial opening in said terminal. The method of claim 12, And the resilient insulating seal is formed of a hydrogen impermeable polysulfone material. The method of claim 1, And at least one comb forming an electrical connection between the internal electrode tab and the terminal. The method of claim 14, And the at least one comb is an electrically conductive bar having a plurality of parallel slots in which the inner electrode tab is frictionally fitted. The method of claim 15, And the at least one comb is formed from copper, copper alloy, nickel coated copper or nickel coated copper alloy. The method of claim 1, And the terminal is formed of copper, copper alloy, nickel coated copper or nickel coated copper alloy. The method of claim 1, And the at least one battery electrode separator formed between the positive electrode and the negative electrode comprises separators surrounding each electrode. The method of claim 1, And the separators are formed of polypropylene with grain or slot structure in a direction. The method of claim 19, And the separators are arranged such that the grain or slot structure in the predetermined direction is aligned along the height direction of the at least one positive electrode and the at least one negative electrode. The method of claim 3, wherein And wherein the exterior of the metal prism battery case is electrically isolated from the surrounding environment by a nonconductive polymer coating. The method of claim 21, And wherein the nonconductive polymer coating is an electrically insulating polymer tape layer. The method of claim 1, And the battery positive electrode and the battery negative electrode are formed in the case such that the respective electrical collection tabs lie opposite each other on top of the case. The method of claim 23, wherein The battery positive electrode and the battery negative electrode have a notched corner in which electrode electrode collecting tabs having opposite polarities are located, thereby preventing short circuits between the electrodes and mechanically removing unused self-weight electrode material. Improved rechargeable battery. The method of claim 1, And the battery includes nineteen positive and twenty negative electrodes alternately formed in the case. The method of claim 3, wherein The interior of the metal prism battery case is electrically insulated from the electrode and electrolyte. The method of claim 26, The interior of the metal prism battery case is electrically insulated from the electrode and electrolyte by coating the interior of the battery case with an electrically insulated polymer material. The method of claim 26, The interior of the metal prism battery case is electrically insulated from the electrode and electrolyte by placing the electrode and electrolyte in a polymer bag that is sealed and inserted into the battery case. The method of claim 1, And the negative electrode is formed of a thermally conductive sintered metal hydride electrode material. The method of claim 29, And the thermally conductive sintered metal hydride electrode is in thermal contact with the battery case.