Lithium energy storage device with internal fuse

Abstract

To provide an energy storage device that can prevent and suppress the occurrence of thermal damage caused by an internal short circuit or the like in a lithium battery.SOLUTION: An energy storage device is constituted by a thin metallized current collector (aluminum and / or copper, as examples), a high shrinkage material, a material that becomes non-conductive when exposed to high temperatures, and combinations thereof, and provision of an internal fuse placed within the battery itself gives it the ability to withstand certain drawbacks within a targeted lithium battery (dendrites, unexpected electrical surges, etc.), and this prevents undesirable high temperatures resulting from short circuits. A battery product and a method of use thereof that include such improvements are also encompassed by this disclosure.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The technology described herein relates to improvements in the structural components and physical properties of lithium battery products. For example, standard lithium-ion batteries are prone to certain phenomena associated with short circuits, resulting in high temperatures and eventual ignition. Structural concerns regarding battery components have been found to be the cause of such problems. Improvements provided herein include the use of thin metallized current collectors (e.g., aluminum and / or copper), high shrinkage rate materials, materials that become nonconductive when exposed to high temperatures, and combinations thereof. These improvements provide the lithium battery with the ability to withstand certain defects within the target lithium battery (e.g., dendrites, unexpected electrical surges) by providing a superficial internal fuse within the lithium battery itself, thereby preventing undesirable high temperatures resulting from short circuits. Battery products incorporating these improvements and methods of use thereof are also included in this disclosure. [Background technology]

[0002] Lithium batteries are widely used as a power source in countless products worldwide. From rechargeable power tools to electric vehicles and ubiquitous mobile phones (and tablets, handheld computers, etc.), lithium batteries (various types of ions) are used as the primary power source due to their reliability, rechargeability, and long service life. However, such a widely used power source has several problems, some of which have proven to be more serious. In particular, safety issues have become apparent, and certain defects within such lithium batteries, whether due to initial manufacturing defects or time-related disassembly issues, make them susceptible to the possibility of ignition during short-circuit events. Essentially, internal defects in the conductive materials have been found to generate undesirable high heat within such battery structures, ultimately leading to ignition. As a result, certain products that utilize lithium batteries, from handheld computer devices (Samsung Galaxy Note 7, one of the less well-known cases) to entire aircraft (Boeing 787), have been banned from sale and / or use until solutions are provided for the lithium batteries used in and with them (and in cases where the Samsung Galaxy Note 7 is banned from all aircraft in certain regions). Even Tesla's electric vehicles have exhibited significant problems with lithium battery components, leading to major news stories of these expensive cars exploding like fireballs due to battery issues. Therefore, widespread recalls or complete bans in connection with such lithium battery problems still exist, highlighting the great need to overcome these issues.

[0003] These problems exist primarily from the perspective of the individual battery components that are manufactured, or because such components are constructed as individual batteries themselves, resulting in manufacturing issues. Looking in more detail, lithium batteries currently consist of six main components: cathode material, a cathode current collector (such as aluminum foil) coated with the cathode material, anode material, an anode current collector (such as copper foil) coated with the anode material, a separator located between each anode and cathode layer and typically made of a plastic material, and an electrolyte as a conductive organic solvent that saturates other materials, thereby providing a mechanism for conducting ions between the anode and cathode. These materials are typically rolled together in a can or stacked, as shown in Figure 1 of the prior art. There are many other configurations that are used or could be used for the purpose of manufacturing such batteries, such as pouch cells, prismatic cells, button cells, cylindrical cells, wound prismatic cells, and wound pouch cells, and even more configurations. These battery cells, when properly manufactured and handled gently, can provide energy for various applications for thousands of charge-discharge cycles without any noticeable safety issues. However, as suggested above, certain events, particularly certain defects, can cause internal short circuits between internal conductive materials, which can lead to overheating and internal thermal runaway. These are known to be the ultimate cause of the risk of fire in such lithium batteries. These events can be further caused by internal defects such as the presence of metal particles in the battery, burrs in the current collector material, thin spots or holes in the separator (which are present or occurred during subsequent processing), misalignment of battery layers (leaving them "open" to allow unwanted conductivity), penetration of the battery by external debris (such as road debris colliding with a moving vehicle), shattering and / or destabilization of the cell itself (e.g., due to an accident), and charging of the cell in a confined space. Generally, these types of defects are known to create small electron conduction paths between the anode and cathode.If such an event occurs, the next time the cell is charged, these conductive paths can cause the cell to discharge, ultimately generating excessive heat that damages the battery structure and endangers the underlying devices to which it is supplied with power. Combined with the presence of flammable organic solvent materials as the battery electrolyte (which is generally necessary for the battery's operation), it has been shown that such excessive heat can cause the battery to ignite, ultimately leading to a very dangerous situation. Once such problems begin, they are difficult to control and can cause serious harm to consumers. These potential destructive situations should be avoided by providing batteries that supply electrical energy without damaging the flammable organic electrolyte in this manner.

[0004] Excessive heat generated internally can cause further contraction of the plastic separator, which can lead to it separating, detaching, or increasing the short-circuit area within the battery. In such situations, a larger exposed short-circuit area within the battery allows current to continue flowing, causing heat to rise and leading to high-temperature events that can cause serious damage to the cell, such as rupture, venting, and even flames and fire. Such damage is particularly problematic because the possibility of ignition and deterioration can occur rapidly, potentially leading to the explosion of the battery and potentially underlying devices, putting users at serious risk.

[0005] Lithium batteries (of many different types) are particularly susceptible to problems related to short circuits. Typical batteries tend to exhibit increased discharge rates when exposed to high temperatures, which, as mentioned above, can lead to uncontrolled (runaway) flares and ignition. Because of these potentials, certain regulations are in place to control the actual use, storage, and even transportation of such battery products. The ability to implement appropriate protocols to prevent such runaway events related to short circuits is indeed crucial. However, there remains a challenge in how to actually solve these problems, especially when components are manufactured from countless suppliers and many different locations around the world.

[0006] In some cases, efforts focus on providing appropriate and / or improved separators as a means to help mitigate the possibility of such lithium batteries igniting. Plastic films with low melting points and / or shrinkage rates can increase the likelihood of such batteries igniting. The general idea is to include certain coatings on these separator materials without reducing their electrolyte separation ability during actual use. For example, ceramic particles are used as polypropylene and / or polyethylene film coatings as a means to improve the dimensional stability of such films (e.g., raising the melting point). Binder polymers are also included as components to improve the cohesive force between ceramic particles and their adhesion to the plastic film. However, in practice, it has been found that the increase in heat imparted to the overall film structure by ceramic particle coatings is relatively small, and therefore, the main cause of problems with such separators is considered to be the actual separator material(s) themselves.

[0007] As a result, separator materials that are far more thermally stable than the polyethylene and polypropylene porous films that constitute the base layer of typical ceramic-coated separators have been designed and implemented, at least to some extent. These low-shrinkage, dimensionally stable separators exhibit less than 5% shrinkage when exposed to temperatures of at least 200°C (up to 250°C, 300°C and above), which is considerably higher than the high shrinkage rates exhibited by bare polymer films (approximately 40% at 150°C) and ceramic-coated films (more than 20% at 180°C) (a comparison of such shrinkage measurements is shown in Figure 2 of the Prior Art). Such low-shrinkage materials can alter the thermal decomposition mechanism within the target cell when a short circuit occurs. Heat is always generated when a short circuit occurs in such a battery cell. If the separator does not shrink in relation to such a short-circuit event, the heat continues to be generated and "accumulate" until another material in the battery decomposes. This phenomenon has been simulated in industry-standard nail-piercing tests. For example, even when using a separator containing para-aramid fibers and exhibiting shrinkage stability below 550°C, the test batteries in question showed a tendency for the circuit to short-circuit, along with their own internal results. These cells were examined more closely after being opened, excess electrolyte evaporated, the cells filled with epoxy, and then cut perpendicular to a nail remaining inside the cell. Scanning electron microscope images were taken using backscatter electron imaging (BEl), which allowed for mapping of various battery elements and demonstrated the effect of nail penetration activity. These are shown in prior art figures 3A and 3B.

[0008] Note that in Figure 3A of the prior art, the copper layer is consistently closer to the nail than the aluminum layer. Also note that the highly stable separator remains intact between the electrodes. Figure 3B of the prior art shows that one end of the aluminum layer is at a higher magnification and terminates in a cracked gray matter layer. This was investigated by BEl and the resulting material was found to be aluminum oxide, which is an insulating ceramic. With this evidence, it was proposed that if the separator itself is thermally stable, the aluminum current collector will oxidize and effectively interrupt the circuit (once insulating aluminum oxide is formed, any short circuit will stop). Once the circuit is interrupted, the flow of current stops, no heat is generated, the stability of the separator decreases, and the process that would lead to thermal runaway is reversed.

[0009] However, these conceivable solutions are limited to simply replacing the separator with one having higher shrinkage characteristics. While such a simple decision seems highly valuable, other manufacturing procedures and specific components (such as ceramic-coated separator types) remain that may be difficult to replace in widely used and approved battery products. Thus, despite the obvious advantages of using and incorporating thermally stable separators, and especially despite the obvious advantages of using and incorporating thermally stable separators, undesirable battery ignition can still occur, particularly when ceramic-coated separator products are considered safe for this purpose. Therefore, in addition to the use of such highly thermally stable separator materials, it has been found that there must be at least another internal battery cell-only structural mechanism that can improve or at least reduce the opportunity for heat generation due to internal short circuits. In such a situation, if a short circuit occurs in such a battery cell, the internal circuit is completely shut down by the formation of an internal fuse, thus preventing harmful high-temperature damage. However, to date, lithium battery technology has not offered any proposals that easily solve these problems. This disclosure provides such highly desirable improvements, making lithium battery cells extremely safe and reliable in multiple markets.

[0010] Therefore, there is a need for a new and improved lithium energy storage device equipped with an internal fuse that can be used to withstand specific defects in the target lithium battery by providing a superficial internal fuse within the lithium battery itself to prevent undesirable high temperatures resulting from a short circuit. In this regard, the present technology substantially fulfills this need. In this respect, the lithium energy storage device with an internal fuse according to the present technology substantially deviates from the conventional concepts and designs of the prior art, thereby providing a device primarily developed for the purpose of withstanding specific defects in the target lithium battery by providing a superficial internal fuse within the lithium battery itself to prevent undesirable high temperatures resulting from a short circuit. [Overview of the Initiative] [Problems that the invention aims to solve]

[0011] Currently, considering the aforementioned drawbacks inherent in known types of lithium batteries existing in the prior art, this technology provides an improved lithium energy storage device with an internal fuse, overcoming the aforementioned disadvantages and drawbacks of the prior art. Therefore, the general objective of this technology, described in more detail below, is to provide a new, improved lithium energy storage device and method with an internal fuse that possesses all the advantages and many novel features of the prior art mentioned to date. The result is a lithium energy storage device with an internal fuse, either alone or in any combination thereof, that was not anticipated, revealed, suggested, or even implied by the prior art. [Means for solving the problem]

[0012] A clear advantage of this disclosure is that a mechanism for interrupting the conductive path when an internal short circuit occurs can be provided through structural components, thereby stopping or significantly reducing the flow of current that could generate heat within the target battery cell. Another advantage is that such a protective structure can be provided within a lithium battery cell, which also results in weight and cost improvements that are beneficial to the manufacture, transport, and use of the entire cell. Thus, another advantage is that an internal fuse structure is formed and maintained within the target battery cell until its activation is required. Another advantage is that a lighter battery can be provided by utilizing a thin-film-based current collector that prevents thermal runaway during short circuits or similar events. Yet another advantage is that flammable organic electrolyte materials can be used within the battery without any apparent tendency to ignite during short circuits or similar events.

[0013] Accordingly, the disclosure of the present invention encompasses an energy storage device comprising an anode, a cathode, at least one polymer or fiber separator present between the anode and the cathode, and at least one current collector in contact with at least one of the anode or cathode, wherein the anode or cathode is positioned between at least a portion of the current collector and the separator, the current collector comprising a conductive material coated on a polymer material substrate, and the current collector thereby deactivates conductivity at the contact point when exposed to a short circuit at the operating voltage of the energy storage device, the operating voltage being at least 2.0 volts. One example is a current density at the contact point of 0.1 amperes / square millimeter and a tip size of 1 square millimeter or less. Naturally, for larger cells, the required current density threshold may be higher, in which the cell may only deactivate conductivity at current densities of at least 0.3 amperes / square millimeter, e.g., at least 0.6 amperes / square millimeter, or even at least 1.0 ampere / square millimeter. Methods for utilizing such beneficial current collector components (such as lithium-ion batteries, capacitors, etc.) within energy storage devices are also included in this disclosure.

[0014] Furthermore, very large current densities can be maintained for very short periods or within very small tip probes. In these situations, larger currents, such as 5 amperes, 10 amperes, or even 15 amperes, can be connected for very short periods (e.g., less than 1 second, or less than 0.1 seconds, or even less than 1 millisecond (0.001 seconds)). Within this disclosure, it may be possible to measure larger currents, but the delivery time of such currents is sufficiently short so that the total energy delivered is very small and not enough to generate enough heat to cause a thermal runaway event in the target battery cell. For example, it has been shown that a short circuit in a conventional architecture cell can generate 4.2 volts and 10 amperes in 30 seconds, resulting in the delivery of 1200 joules of energy to a small localized area within such a battery. Measurements of this result show that the temperature of a 1-gram portion of the battery in question rises by approximately 300°C. This temperature is high enough to not only melt the conventional separator material present inside, but also to bring the entire cell into a thermal runaway state (which, as mentioned above, can damage the electrolyte material present within, potentially causing destruction not only to the battery in question, but also to the device / packaging in which it resides and the surrounding environment). Therefore, even if complete prevention is not possible, there is certainly the possibility of reducing the duration of the short circuit, the resulting energy levels associated with low joule measurements within such short circuits, and avoiding thermal runaway (and the associated potential disasters). For example, by reducing the residence time of the short circuit in the current collector to less than 1 millisecond, the amount of energy subsequently delivered can be reduced to about 0.04 joules (in contrast to the 1200 joules mentioned above, which would be excessively high, for example, above 300°C within a 1-gram local area of ​​the battery in question). Therefore, at such low levels, only a temperature increase of 0.01°C occurs within such a 1-gram local area of ​​the battery, thereby preventing thermal runaway within the target cell and thus the entire battery.

[0015] Therefore, another important advantage of this disclosure is to provide a battery with a current collector that significantly limits the delivery time of the current level applied to the target current collector surface via the probe tip (to controllably emulate the effects of internal manufacturing defects, dendrites, or external events causing internal short circuits within the battery in question) to less than 1 second, preferably less than 0.01 seconds, more preferably less than 1 millisecond, and most preferably perhaps even less than 100 microseconds, especially for very large currents. Naturally, such currents are limited to the internal voltage of the cell and may be 5.0V, 4.5V, or 4.2V, or less, such as 4.0V or 3.8V, but with a minimum of 2.0V.

[0016] These new current collector components are actually counterintuitive to the components typically found in lithium (and other types) batteries and energy storage devices today. The standard current collectors offered are conductive metal structures, such as aluminum and / or copper panels of a certain thickness, which are thought to provide some form of protection to the structure, such as the entire battery. These typical current collector structures are designed to achieve the maximum possible conductivity within weight and space constraints. However, this idea is actually misleading, as the thick panels prevalent in today's energy storage devices not only arc when a short circuit occurs, but also contribute significantly to runaway temperatures when such a situation arises. Such short circuits can be caused, for example, by dendritic formation within the separator. Such deformation (whether during or after manufacturing, or as a result of prolonged use, with the possibility of decomposition) can cause voltage to unexpectedly pass from anode to cathode, resulting in an increase in current, which in turn can cause a temperature rise wherever this occurs. In fact, one source of short circuits that can cause defects is burrs that form on the edges of these thick, typical current collectors when they are slit or cut by a wear blade during the repeated manufacturing process of multiple products (which is common now). However, standard current collector materials tend to simply generate sparks, allowing temperature rises, which further allows current present during such events to continue through the device, thereby enabling free generation and movement. It has been repeatedly analyzed and understood that there is no means to interrupt the rise in current and temperature levels. This problem directly leads to runaway high-temperature consequences, and in the absence of any internal means to prevent such situations, there is usually an imminent possibility of fire, and ultimately the burning and destruction of the device. Furthermore, the current path (charge direction) of a standard current collector remains fairly static both before and during a short circuit event, essentially exhibiting the same potential charge movement that would be expected if it moved horizontally along the current collector from cathode to anode and then in a particular direction.However, in a short circuit, this current path cannot prevent, or at least interrupt or delay, such charge movement; in other words, rapid discharge becomes possible in a way that causes the entire battery to run out of control. Combined with the high temperatures associated with such rapid discharge, this leads to the catastrophic problems mentioned above (fire, explosion, etc.).

[0017] Conversely, and quite unexpectedly, and contrary to the typical structure and configuration of lithium batteries, the use of the current collector of this disclosure results in very high current density measurements (due to the reduced thickness of the conductive element) and prevents the movement of charge (e.g., in the direction of no charge) during short-circuit events. In other words, certain structural limitations imposed on the current collector components disclosed herein result in a very high resistance level, but the current density increases to the extent that it suppresses the generation of high temperatures in the short circuit. Thus, this resistance level allows the conductive material (e.g., aluminum and / or copper as an example) to receive the short-circuit charge, but the structural formation provided herein allows the conductive material to react immediately to such high-temperature local charges. Combined with other structural considerations of these current collector components, namely the actual lack of dimensionally stable polymer material in contact with these conductive material layers, the conductive material oxidizes immediately at its charge point, remaining non-conductive, such as aluminum or cupric oxide. Because the non-conductive material is instantaneously created in this way, there is no direction in which it can move, and therefore the short-circuit charge is thought to dissipate. Thus, in the current collector described herein, the occurrence of an internal short circuit immediately stops the current, and the high temperature result immediately caused by such a short circuit is effectively utilized to create a barrier to further charge movement. Therefore, when there is a further shortage of current throughout the body of the energy storage device (naturally, in relation to the short circuit), the undesirable event disappears to the extent that the short circuit is completely suppressed, and thereafter no runaway current or high temperature result occurs. Perhaps most importantly, even with the presence of localized non-conductive material, when the energy storage device (such as a battery) is operating as intended, it does not result in any significant reduction in current, so the current collector remains functional for its original purpose and protective purposes. Furthermore, because the non-conductive material is created in a relatively small area, there is still a significant surface area in the current collector that can be further utilized without the need for any repair, replacement, or other improvement.While not always the case, and certainly necessary to ensure such conditions are met, the likelihood of such high-temperature exposure and destructive events occurring without specific precautions and modifications, as disclosed herein, remains in fact far higher than normally acceptable. Therefore, the entire current collector acts as a two-dimensional electrical fuse due to its instability under short-circuit conditions, preventing potentially catastrophic high currents associated with the short circuit by using the instantaneous effect of its high current to destroy the current collector's ability to conduct current at the short-circuit point.

[0018] These advantages are possible with respect to such novel resulting current collectors, where similar final results may be provided through multiple different alternatives. In any of these alternative configurations, the current collectors described herein function, on the surface, as an internal fuse within the target energy storage device (e.g., lithium battery, capacitor, etc.). However, in each case (alternative), there is a current collector comprising a polymer layer, one or both sides of which are metallized, with at least one metallized side in contact with the anode or cathode of the target energy storage device. One alternative is where the total thickness of the metallized (coated) polymer substrate of the entire current collector is less than 20 microns, and the resistance measurement is less than 1 ohm / square. A typical current collector may exhibit these features even if it is much heavier than one made of a reinforced polymer substrate and does not have the inherent safety advantages of the disclosure of this invention. However, in this alternative structure, because the components are so thin, a short circuit with excessively high temperatures may occur in reaction with the metal coating and in relation to the overall resistance level. This is due to current spikes in localized areas of the metal oxide that immediately prevent any further current movement from that area during such short circuits.

[0019] Another possible alternative to these new current collectors is to provide temperature-dependent metallic (or metallized) materials. These materials shrink from the heat source during a short circuit or readily decompose at specific material locations to become non-conductive materials (e.g., aluminum oxide from an aluminum current collector) (as mentioned above in different ways). Thus, the current collectors become thermally weaker, in stark contrast to the currently used aluminum and copper current collectors, which are very thermally stable at high temperatures. As a result, the manufacturing safety of current collectors can be improved by coating a layer of a conductive material, such as copper or aluminum, onto a fiber or film that can decompose at low short-circuit current densities and exhibit a relatively high shrinkage rate at relatively low temperatures, in alloys of metals with low intrinsic melting points. Another possible way to achieve these results is to manufacture current collectors by coating a layer of a conductive material, such as the copper or aluminum mentioned above, onto a fiber or film that can swell or melt in the electrolyte when the material is heated to a temperature that is relatively high compared to the cell's operating temperature but low compared to the temperature at which thermal runaway can occur. Examples of such polymers that can swell in lithium-ion electrolytes include polyvinylidene fluoride and polyacrylonitrile, but others are known to those skilled in the art. Yet another way to achieve such alternative internal electrical fuse generation processes is to coat a substrate with a metal that can be oxidized under heating, such as aluminum, with a total metal thickness much thinner than that typically used in lithium batteries. For example, very thin aluminum current collectors used today can be as thick as 20 microns. If the coating thickness is less than 5 microns in total, the circuit will be interrupted faster, and if it is less than 2 microns, or even less than 1 micron, the circuit will be interrupted faster. Furthermore, another way to obtain interruption in the conductive path is to provide a current collector with limited conductivity that decomposes under high current density surrounding the short circuit, similar to the decomposition seen in commercial fuses today.This can be achieved by providing a current collector having a resistivity of 5 milliohms / square, or 10 milliohms / square, or potentially preferably 20 milliohms / square or more, or potentially more preferably 50 milliohms / square or more. For batteries designed for high power, which may use relatively low resistance and / or relatively high resistance compared to cells designed for low power and high energy, the use of current collectors with different resistivity can be further separately selected. Yet another way to achieve isolation of the conductive path is to provide a current collector that oxidizes to a non-conductive material at a much lower temperature than aluminum, thereby allowing the current collector to become inert in the short-circuit region before the separator decomposes. Certain alloys of aluminum oxidize faster than aluminum itself, and these alloys also cause decomposition of the conductive path faster or at lower temperatures. As possible alternatives, but not limited to, gold, silver, vanadium, rubidium, iridium, indium, platinum, and any other metal exhibiting conductivity can be used in such thin-layer capacitances (essentially, in very thin layers, the costs associated with using such metals can be significantly reduced without sacrificing conductivity, and furthermore, protection from the possibility of thermal runaway during events such as short circuits can be provided). Similarly, layers of different metals can be used, or even separate areas of metal deposited within or as separate layer components can be utilized. Indeed, one side of such a coated current collector substrate may contain a different type of metal than the other side, and similarly may have different layer thicknesses when compared.

[0020] One way to improve the electrical properties of a cell is to ensure that the coated current collector has two conductive coated sides. This allows conductivity from one coating to the other on the surface. Such a result is not possible with, for example, an uncoated polymer film. However, it is recognized that such bifacial conductive throughput can be achieved, as a non-limiting example, by nonwoven fabrics such as nonwoven fabrics with a certain percentage of conductive fibers, or nonwoven fabrics to which conductive materials have been added, or nonwoven fabrics made from conductive materials (such as carbon fibers or metal fibers), or nonwoven fabrics containing fibers coated with conductive materials (such as fibers with a metal coating on the surface), as described above. Another type of novel thin current collector material exhibiting top-to-bottom conductivity may be a film made conductive by using an intrinsic conductive material (e.g., conductive polymers such as polyacetylene, polyaniline, or polyvinylpyrrolidine) or by adding conductive materials (such as graphite or graphene, or metal particles or fibers) during or after film manufacturing. Furthermore, another conceivable thin, double-sided current collector material is a polymer substrate with small through-holes whose sides are coated with metal (aluminum or copper) during the metallization process. The conductivity obtained from one side to the other does not need to be as conductive as the conductive coating.

[0021] Therefore, such alternative configurations that obtain the same collector results and physical properties on the surface include the following: a) the total thickness of the coated polymer substrate is less than 20 microns and the resistance is less than 1 ohm / square; b) a collector comprising a conductive material coated on a substrate containing a polymer material, the polymer material exhibiting at least 5% thermal shrinkage at 225°C; c) the metallized polymer material of the collector swells in the electrolyte of the battery, such swelling increasing as the polymer material is heated; d) the total thickness of the conductive material of the collector is less than 5 microns when applied to the polymer substrate; e) the conductivity of the collector is between 10 milliohms / square and 1 ohm / square; f) the metallized polymer substrate of the collector exhibits a porosity of up to 60%. Utilization of any of these alternative configurations within an energy storage device equipped with a separator exhibiting less than 5% thermal shrinkage after 1 hour at 225°C is within the scope of the present disclosure. The overall utilization (method of use) of this type of energy storage device (such as a battery, capacitor, etc.) is also included herein.

[0022] The primary advantage of the present invention is improved cell safety, but as suggested above, there are other advantages, such as a reduction in the overall weight of the energy storage device due to the reduction in the metal weight associated with such current collector components. In this case as well, it is entirely counterintuitive to use a thin polymer layer with a metal coating, especially one with poor dimensional stability, as a current collector in such a battery product. The current thinking in this industry is that a large amount of actual metal and / or insulating components are needed to achieve the desired protective results (especially from potential short-circuit events). Unexpectedly, it is now recognized that not only is this paradigm incorrect, but that effective countermeasures against short-circuit problems in lithium batteries, etc., involve reducing rather than increasing the amount of metal, and bonding the metal to a thermally unstable base layer. Thus, quite unexpectedly, it is understood here that a thin metal layer with such an unstable base layer not only functions to effectively stop discharge events in short circuits, but the overall effect is a much safer and more reliable result, with a significant reduction in the overall weight and volume of these components. Therefore, the unexpected benefit of lower weight and volume requirements within energy storage products (such as batteries) and improved performance is being recognized by the industry far more than initially understood.

[0023] As further explanation, the weight of aluminum with a thickness of 20 microns and a density of 2.7 g / cm³ is 54 g / m². However, the weight of the same metal coated with a 1-micron layer on a 10-micron thick polypropylene film (density 0.9 g / cm³) is 11.7 g / m². Reducing the weight of this current collector can reduce the overall weight of the energy storage device in question (e.g., a battery), thereby increasing mobility, fuel efficiency, or electric range, and generally enhancing its value in mobile electrical applications.

[0024] Furthermore, since the film has high strength, it can be made thinner in the above example. For example, when the total thickness is reduced from 20 microns to 11 microns, the volume of the cell decreases, thereby effectively increasing the energy density. In this way, a current collector with a total thickness of less than 15 microns, preferably less than 12 microns, more preferably less than 10 microns, and most preferably less than 8 microns can be produced and used for such purposes and functions.

[0025] When the bulk resistivity of aluminum is 2.7x10-8 ohm-m and the resistivity of copper is 1.68x10-8 ohm-m, a thin coating can be applied at less than 1 ohm / square, or less than 0.5 ohm / square, or even less than 0.1 ohm / square, or less than 0.05 ohm / square. The thickness of these conductive coatings can be less than 5 microns, preferably less than 3 microns, more preferably less than 2 microns, and potentially most preferably even less than 1 micron. When standard materials commonly used in the market contain 10 microns or more of metal, it is very counterintuitive that much less metal can be used to obtain suitable performance. In fact, most of the metals present in typical storage devices are included to impart mechanical properties suitable for high-speed automated processing. Providing mechanical properties using lower-density polymer materials is one of the advantages of the present invention, which enables the thickness of the metal to be reduced to a level where the safety of the cell is improved. This is because the current collector cannot support a dangerously high current density that would cause an internal electrical short circuit, resulting in thermal runaway, smoke, and fire.

[0026] Furthermore, these conductive layers may be made up of multiple layers. For example, the aluminum layer may be a base layer coated with a thin layer of copper. In this way, bulk conductivity can be provided by lightweight and expensive aluminum, which can be easily deposited by vapor deposition techniques. Copper can provide additional conductivity and passivation to the anode without adding significant additional cost and weight. This example is given for illustrative purposes only, and those skilled in the art can provide many other multilayer conductive structures, any of which are excellent examples of the present invention.

[0027] These thin metal coatings generally result in higher resistance than conventionally implemented aluminum or copper current collectors, which is a distinguishing feature of the present invention when compared. Such novel and suitable current collectors can be manufactured with resistances exceeding 10 milliohms / square meter, preferably exceeding 20 milliohms / square meter, more preferably exceeding 50 milliohms / square meter, and most preferably exceeding 100 milliohms / square meter.

[0028] Furthermore, if the separator has high thermal stability, cells made from the above-mentioned thermally weak current collectors may be safer, as they may exhibit low shrinkage rates at high temperatures, such as less than 5% shrinkage after exposure to 200°C for 1 hour, preferably 250°C for 1 hour, and more preferably 300°C for 1 hour. Existing separators are made from polyethylene with a melting point of 138°C and polypropylene with a melting point of 164°C, and these materials exhibit more than 50% shrinkage at 150°C, as shown in Figure 2. These results are too high for use in thin current collectors, as described herein. To solve these problems, it has been found that there is a need to use specific separators that shrink less than 50%, even less than 30%, or less than 10% at 150°C, as measured by NASA TM-2010-216099 Section 3.5. Even ceramic-coated separators show significant shrinkage at relatively moderate temperatures, either completely blocking or shrinking by more than 20% at 180°C. Therefore, it is desirable to use a separator that does not break during testing when measured with the same test standard and does not shrink by more than 20%, more preferably more than 10%, at 180°C (at least). In the most preferred embodiment, a separator that shrinks by less than 10% when exposed to temperatures of 200°C, 250°C, or even 300°C is used.

[0029] For any of these metallized substrates, it is desirable to have a thin thickness to facilitate the increase in the energy density of the cells. Such a thickness can be achieved using any means, such as calendering, compression, hot pressing, or ablation of the material from the surface in a way that reduces the total thickness. These thickness reduction processes can be carried out before or after metallization. Therefore, it is desirable to have a total thickness of less than 25 microns, preferably less than 20 microns, more preferably less than 16 microns, and potentially most preferably less than 14 microns for the metallized substrate. Commercially available polyester films have been realized with thicknesses of up to 3 microns, and even thinner, 1.2 microns. These types serve as suitable substrates and can reduce the total thickness of the current collector to less than 10 microns, preferably less than 6 microns, and more preferably less than 4 microns. Such ultrathin current collectors (with suitable conductivity as described above and throughout) enable much higher energy density and improved safety performance. These are results that have not been explored before.

[0030] It is also desirable that these metallized substrates be lightweight. This can be achieved, for example, by using low-density polymer materials such as polyolefins, or other low-density polymers such as polyethylene, polypropylene, and polymethylpentene. It can also be achieved by having an open structure in the substrate, or even by utilizing a low-basis-weight substrate. Therefore, the density of the polymer used in the substrate material may be less than 1.4 g / cm³, preferably less than 1.2 g / cm³, and potentially more preferably less than 1.0 g / cm³. The surface density of the substrate material may also be less than 20 g / m², preferably less than 16 g / m², and most preferably less than 14 g / m². Furthermore, the surface density of the metal-coated polymer substrate material may be less than 40 g / m², preferably less than 30 g / m², more preferably less than 25 g / m², and most preferably less than 20 g / m².

[0031] Lightweight materials can also be made from porous polymer substrates. However, the porosity should not be too high for these materials. High porosity results in low strength and increased thickness, effectively negating the objectives of the material. Therefore, such substrate materials exhibit a porosity of less than about 60%, preferably less than 50%, and potentially more preferably less than 40%. Since solid materials can be used for this type of metal-coated current collector, there is no lower limit to the porosity.

[0032] High strength is required to process materials into batteries at high speed. This can be achieved by using stretched polymers, either from stretched fibers or from uniaxially or biaxially stretched films.

[0033] Energy storage devices such as batteries, capacitors, and supercapacitors are manufactured and provided in accordance with this disclosure, as shown below in the attached drawings and in their detailed description. Here, two separate current collectors are provided upon which a short circuit contacts the cathode, anode, or both, as well as at least one current collector exhibiting properties related to no perceptible current movement after contact with a separator and an electrolyte (all of which reside within and are sealed in a standard (preferred) energy storage device container). In most components, the cathode, anode, container, electrolyte, and, in some cases, the separator and components are all standard. However, the current collectors used with and within this specification are, as disclosed, new and unexplored within the scope of this art and counterintuitive to actual energy storage device components. This will also be discussed in detail below.

[0034] As described above, in order to reduce the chances of this happening, if thermal runaway within the battery cell (especially in lithium-ion rechargeable batteries, but of course possible in other types as well) cannot be completely prevented, it is necessary to specifically induce some kind of short circuit within it so that it essentially exists within a short time, thereby shortening the residence time within or on the current collector in question, and ultimately resulting in the minimum joule level energy level (i.e., less than 10, preferably less than 1, and most preferably less than 0.01). In such situations, as previously mentioned, for electrical paths where a thin conductive current collector is placed from anode to cathode and through a separator, and a flammable organic electrolyte is present, it has been observed that a thin, low-weight current collector can lead to these desirable results, particularly in that there is no obvious temperature rise that would impending ignition of electrolyte components, and undesirable charge dissipation on the current collector surface. Surprisingly, and without being bound by any particular scientific explanation or theory, it is thought that due to the conductivity of the thin current collector material, short-circuit charges only reach the thin conductive current collector, and a short-duration, high-energy event occurs instantly as the metal on the current collector surface reacts with the charge itself. This creates metal oxides, which form at specific points on the current collector surface. The metal oxides provide insulation against further electrical activity, and although there is still a possibility that the applied current will dissipate instantaneously and the current collector itself may deform, the aforementioned metal oxides are there to protect against any further charge activity at that particular location. Thus, the other current collector remains intact and can provide the same function as before, and thus provides such protection to any further potential short circuits or similar phenomena. In the case of thermal runaway in prior art battery products, the anode, cathode, current collector, and separator, for example, generate heat, causing sparks and forming an electrical path for igniting the cell in response to a short circuit. Thus, the presence of an ion-transporting flammable electrolyte further creates a significant hazard due to the high temperature consequences associated with such unexpected charges. Essentially, the heat generated by the current collector of prior art triggers an initial electrochemical reaction within the electrolyte material, ultimately leading to an uncontrolled ignition of the electrolyte material itself.Therefore, the current collectors of the present invention disclosed herein are particularly valuable when used in battery cells such as those containing flammable electrolytes. Examples of such electrolytes include organic solvents such as propylene carbonate, ethylene carbonate, ethylmethyl carbonate, diethyl carbonate, and dimethyl carbonate. These electrolytes typically exist as mixtures of the above materials, and possibly together with other solvent materials, such as various types of additives. These electrolytes also have lithium salt components, an example being lithium hexafluorophosphate, LiPF6. While such electrolytes are preferred in the battery industry, as described above, they contribute to potentially hazardous situations. Here again, the current collectors of the present invention, in conjunction with other battery components, greatly and remarkably mitigate these concerns.

[0035] One way in which this current collector demonstrates its usefulness is in the following test. A current source with both voltage and current limits can be set to a voltage limit similar to the operating voltage of the energy storage device in question. The current can then be adjusted, and the current collector can be tested in two configurations. First, a short strip of the current collector of known width is brought into contact with the sample via two metal connectors that contact the entire width of the sample. The current limit of the current source can be increased to see if there is a limit to the material's ability to carry current. This ability can be measured as the total current divided by the width, yielding a result (A / cm) which is shown herein as the horizontal current density. In the second configuration, the ground of the current source is brought into contact with one of the full-width metal contacts, and then the tip of a probe (approximately 0.25 mm²) is placed along the strip of current collector. If the current is too high, a localized area will burn out and no current will flow. If the current is not too high for the current collector, the full current will flow up to the current source's limit. The result is the current limit (A / mm²), which is here referred to as the vertical current density. Thus, a current collector capable of reaching high currents in both configurations is similar to the prior art, and a current collector capable of holding horizontal currents when in full-width contact, but not vertical currents when in point contact, is an example of the present invention as described herein.

[0036] For example, it may be desirable for a current collector to be able to maintain a horizontal current density of 0.1 A / cm, 0.5 A / cm, 1 A / cm, 2 A / cm, or even 5 A / cm. Conversely, for a current collector capable of maintaining the above horizontal current densities, it is desirable that it does not maintain a vertical current density of 0.1 A / mm², 0.5 A / mm², 1 A / mm², 2 A / mm², or even 5 A / mm².

[0037] Such thin lithium-ion battery films may require specific processing steps due to their inherent qualities. However, many processing steps well known in the art may also be used. Generally, the process for manufacturing a lithium-ion battery using the film of the present invention includes the following steps: a. Providing an electrode having at least one metallized substrate having a coating of an ion storage material, b. The step of providing a counter electrode, c. A step of stacking electrodes and opposing electrodes on opposite sides, and a separator component interposed between the electrodes and the opposing electrodes, d. A step of providing a package material including an electrical contact component, wherein the contact includes a portion located inside the package material and a portion located outside the package material. e. The step of electrically connecting electrical contacts to a metallized substrate, and f. The step of introducing at least one liquid electrolyte containing ions into the inside of the package material. g. The step of sealing the above package material, and

[0038] The metallized substrate may be any substrate described in this disclosure.

[0039] Ion storage materials can be, for example, cathode or anode materials for lithium-ion batteries, as is well known in the art. Examples of cathode materials include lithium cobalt oxide (LiCoO2), lithium iron phosphate (LiFePO4), lithium manganese oxide (LiMn2O4), lithium nickel manganese cobalt oxide (LiNixMnyCozO2), lithium nickel cobalt aluminum oxide (LiNixCOyAlzO2), or mixtures of the above or other known in the art. Examples of anode materials include graphite, lithium titanate (Li4Ti5Oi2), hard carbon, tin, silicon, or mixtures thereof, or other known in the art. Furthermore, ion storage materials can be used in other energy storage devices, such as supercapacitors. In such supercapacitors, ion storage materials include activated carbon, activated carbon fibers, carbide-derived carbon, carbon aerogels, graphite, graphene, and carbon nanotubes.

[0040] The coating process can be any coating process commonly known in the art. Knife-over-roll and slot-die coatings are commonly used for lithium-ion batteries, but other coating processes such as electroless plating may also be used. In the coating process, the ion storage material is generally mixed with other materials such as a binder, such as polyvinylidene fluoride or carboxymethylcellulose, or other film-forming polymers. Other additives to the mixture include carbon black and other conductive additives.

[0041] The counter electrode includes other electrode materials having a different electrochemical potential from the ion storage material. Generally, if the ion storage material is a lithium-ion anode material, the counter electrode is made from a lithium-ion cathode material. If the ion storage material is a lithium-ion cathode material, the counter electrode may be a lithium-ion anode material. If the ion storage material is a supercapacitor material, the counter electrode can be made from the supercapacitor material, or optionally from a lithium-ion anode material or lithium-ion cathode material. In any case, the counter electrode includes an ion storage material coated on a current collector material, which may be a metal foil or metallized film as in the present invention.

[0042] In the lamination process, the electrodes of the present invention are laminated together with counter electrodes comprising opposing electrode materials and porous separators between them. As is generally known in the art, both sides of the electrodes may be coated, and the stack of electrodes formed by the electrodes of the present invention and the counter electrodes alternates between the layers. Alternatively, as is also known in the art, strips of electrode material may be stacked as described above and then wound into a cylindrical shape.

[0043] Examples of packaging materials include hard packages such as cylindrical cell cans, flat hard cases, or polymer pouches. In any case, two means of making an electrical connection may be required via cases that can hold different voltages and conduct current. In some cases, one means may be a part of the case itself, while the other is a different part of the case that is electrically insulated from the first part. In other examples, the case may be nonconductive, but two metal conductors may protrude from the case, which are often referred to as tabs.

[0044] Common methods for connecting the metallized substrate to the means for electrical connection include welding, taping, clamping, stapling, riveting, or other mechanical means. Because the metal of the metallized substrate can be very thin, surface-to-surface contact is generally required to enable an interface that can carry large currents, resulting in a large surface area between the means for electrical connection and the metallized substrate via the case. To carry sufficient current, this surface area needs to be greater than 1 square millimeter (10-12 square meters), but may need to be greater than 3 square millimeters, even 5 square millimeters, and even more preferably 10 square millimeters.

[0045] Liquid electrolytes are typically combinations / mixtures of a polar solvent and a lithium salt. Commonly used polar solvents include propylene carbonate, ethylene carbonate, dimethyl carbonate, and diethyl carbonate, as mentioned above, but other polar solvents, including ionic liquids or even water, may also be used. Lithium salts commonly used in this industry include, but are not limited to, LiPF6, LiPF4, LiBF4, and LiCl04. Electrolytes may contain additives known in the art. In many cases, electrolytes can be flammable, and the safety features of the current collectors in the metallized substrates of the present invention can be advantageous in preventing dangerous thermal runaway events that could cause fire and damage both inside and outside the cell.

[0046] One embodiment of this technology may be an energy storage device comprising an anode, a cathode, at least one separator interposed between the anode and the cathode, at least one liquid electrolyte, and at least one current collector in contact with at least one of the anode and the cathode. The current collector may include a top and a bottom surface. The separator may be of polymer, ceramic, or nonwoven fabric construction. The current collector may be a nonconductive material having conductive coatings on both sides thereof. The current collector may exhibit the ability to carry a useful current density when operating normally along a current path horizontally along the current collector. When subjected to the shrinkage test described in NASA TM-2010-216099 Section 3.5, the polymer or fiber separator will not break or shrink by more than 20% at 180°C.

[0047] Another aspect of this technology is an energy storage device comprising an anode, a cathode, at least one separator interposed between the anode and the cathode, at least one liquid electrolyte, and at least one current collector in contact with at least one of the anode and the cathode. The current collector may include a top surface and a bottom surface. The separator may be of polymer, ceramic, or nonwoven fabric structure. The current collector may be a substrate of a nonconductive material having conductive coatings on both sides thereof. The current collector may exhibit the ability to carry a useful current density when operating normally along a current path horizontally along the current collector. The nonconductive material substrate may be conductive from the conductive material coated on one side to the conductive material coated on the opposite side.

[0048] Another aspect of the present technology is a process for manufacturing an energy storage device, comprising the steps of: providing an electrode having at least one metallized substrate coated with an ion storage material; providing a counter electrode; laminating an electrode and a counter electrode on opposite sides of each other, and a separator component interposed between the electrode and the counter electrode; providing a package material including an electrical contact component, wherein the contact comprises a portion located inside the package material and a portion located outside the package material; electrically connecting the electrical contact to the metallized substrate; introducing at least one liquid electrolyte containing ions inside the package material; and sealing the package material.

[0049] These, along with other objectives of the present invention and various features of the novelty that characterize the invention, are detailed in the claims attached to and forming part of this disclosure. For a better understanding of the present invention, its operational advantages, and the specific purposes achieved by its use, please refer to the accompanying drawings and descriptions illustrating exemplary embodiments of the present invention. [Brief explanation of the drawing]

[0050] [Figure 1] This diagram illustrates the prior art architecture of wound cell types such as the 18650 cell. [Figure 2] This figure depicts prior art shrinkage correlated with temperature, measured by dynamic mechanical analysis of several lithium-ion battery separators, as measured according to NASA / TM-2010-216099, "Battery Separator Characterization and Evaluation Procedures for NASA's Advanced Lithium Ion Batteries" (incorporated herein by reference). This includes first-generation separators (Celgard PP, Celgard tri-layer), second-generation separators (ceramic PE), and third-generation separators (Silver, Gold, Silver AR). [Figure 3A] This figure shows a scanning electron microscope (SEM) image of a cross-section of a prior art pouch-type cell that underwent a nail-piercing test. The layers are aluminum and copper, mapped by BE1 (backscattered electron imaging). The nail is vertical on the left side. In both cases, the aluminum layer recedes from the nail, leaving behind an insulating aluminum oxide "skin." [Figure 3B] This is a magnified view of one of the layers shown in Figure 3A of the prior art. A close-up of the aluminum oxide layer is shown, clearly demonstrating that there is no separator shrinkage whatsoever and that the electrodes are separated to the extreme. [Figure 4] This figure illustrates the present invention, in which a thin layer of conductive material is present on the outside, and the central substrate is a thermally unstable layer at the temperature required for thermal runaway. This substrate may be a molten layer, a shrinking layer, a dissolved layer, an oxidized layer, or any other layer that undergoes thermal instability at temperatures between 100°C and 500°C. [Figure 5A] This is a diagram of prior art for thick aluminum current collectors, which are generally 12 to 20 microns thick. [Figure 5B] This diagram illustrates the present invention, showing a 14-micron thick substrate with 1-micron aluminum on both sides. While thick current technology can carry large currents associated with short circuits, the current collector of the present invention cannot carry large currents associated with short circuits. [Figure 6A] This figure shows an image of Comparative Example 1 after being applied to the tip of a high-temperature soldering iron. [Figure 6B] This figure shows an image of Comparative Example 2 after being exposed to the tip of a high-temperature soldering iron. In Comparative Example 2, there is no change even after the high-temperature soldering iron is applied. [Figure 7A] The image shows Example 1 after being applied to the tip of a high-temperature soldering iron. [Figure 7B] The image shows Example 2 after being applied to the tip of a high-temperature soldering iron. [Figure 7C] The image of Example 3 after being exposed to the tip of a high-temperature soldering iron is shown. Examples 1 to 3 all exhibit the shrinkage described in this disclosure for the metallized substrate. [Figure 8A] The image shows Example 4 after it has been applied to the tip of a high-temperature soldering iron. [Figure 8B] The image shows Example 45 after being applied to the tip of a high-temperature soldering iron. [Figure 8C] The image of Example 6 after being applied to the tip of a high-temperature soldering iron is shown. The images of Examples 4-6 after being applied to the tip of a high-temperature soldering iron are shown. Example 4 shows a metallized substrate exhibiting the shrinkage described in this disclosure. Example 5 has fibers that dissolve under heating in a lithium-ion electrolyte. Example 6 is an example of a thermally stable substrate that requires a thin conductive layer to function in accordance with the present invention. [Figure 9] These are SEM cross-sectional images at two magnifications, one of which shows the metallized surface of one possible embodiment of a current collector currently disclosed as described in Example 9. The metal is clearly much thinner than the original substrate, which is 20 microns thick. [Figure 10A] This is an optical microscope image of Comparative Example 3 after a short circuit. [Figure 10B] These are optical microscope images of Comparative Example 4 after short-circuiting. These images show the ablation in the short-circuited but hole-free region. [Figure 11A] These are optical microscope images of two regions in Example 14 after short-circuiting. [Figure 11B] These are optical microscope images of two regions of Example 14 after a short circuit. These images show the transparent holes in the material caused by the high current density of the short circuit. [Figure 12] This figure shows the size and shape of the current collector used in the following example. [Modes for carrying out the invention]

[0051] The following descriptions and examples merely illustrate potential embodiments of the present disclosure. The scope and breadth of such disclosure with respect to the following claims will be readily apparent to those skilled in the art.

[0052] As stated above, this disclosure represents a significant departure and is counterintuitive to all previous understandings and improvements within the lithium battery (and other energy storage device) industry. Conversely, the novel devices described herein offer several beneficial results and characteristics that are not only unexpected but also previously unexplored within this domain. However, it is important to first note, for comparison, the distinct differences between previous devices and the devices currently disclosed and broadly covered herein.

[0053] Comparative Example 1 The cathode of the lithium iron phosphate battery was obtained from GB Systems (China). As an example of a commercially available current collector, an aluminum tab was removed and its thickness, surface density, and resistance were measured. The results are shown in Table 1 below. Next, a hot soldering iron was applied to the aluminum foil for 5 seconds. This was measured using an infrared thermometer and had a temperature of 500-525°F. Applying the soldering iron to the current collector had no effect. Thickness, surface density, and resistance were measured. This material was placed in a 175°C oven for 30 minutes and its shrinkage was measured. A photograph was taken as illustrated in Figure 6A. Figure 5A provides an example of a conventional current collector in such a comparative battery.

[0054] Comparative Example 2 The anode for the lithium iron phosphate battery was obtained from GB Systems (China). As an example of a commercially available current collector, a copper tab was removed, and its thickness, surface density, and resistance were measured. The results are shown in Table 1 below. Subsequently, a high-temperature soldering iron was applied to the copper foil, as in Example 1. There was no effect from applying the soldering iron to the current collector. Thickness, surface density, and resistance were measured. This material was placed in a 175°C oven for 30 minutes, and shrinkage was measured. A photograph was taken as illustrated in Figure 6A. Similar to Comparative Example 1, Figure 5A shows a representation of the internal structure of such a battery. The thickness of the current collector is important because it is a monolithic metal structure, not the thin type currently disclosed. [Examples]

[0055] Polypropylene lithium battery separator material was obtained from MTI Corporation. The material (product number 2500) was manufactured by Celgard. Thickness, surface density, and resistance were measured, and the results are shown in Table 1 below. Next, a high-temperature soldering iron was applied to the separator in the same manner as in Example 1. When a thermometer was applied to the current collector, a small hole was formed. The diameter was measured and is included in Table 1. Thickness, surface density, and resistance were measured. This material was placed in an oven at 175°C for 30 minutes, and shrinkage was measured. Photographs were taken as illustrated in Figure 7A. [Examples]

[0056] Ceramic-coated polyethylene lithium battery separator material was obtained from MTI Corporation. Thickness, surface density, and resistance were measured and are shown in Table 1 below. Next, a high-temperature soldering iron was applied to the separator in the same manner as in Example 1.

[0057] Small holes were formed by applying a soldering iron to the current collector. The diameter was measured and is included in Table 1. Thickness, surface density, and resistance were measured. The material was placed in a 175°C oven for 30 minutes and shrinkage was measured. Photographs were taken as illustrated in Figure 7A. [Examples]

[0058] Ceramic-coated polypropylene lithium battery separator material was obtained from MTI Corporation. Thickness, surface density, and resistance were measured and are shown in Table 1 below. Next, a high-temperature soldering iron was applied to the separator in the same manner as in Example 1. Small holes were formed by applying the soldering iron to the current collector. The diameter was measured and is included in Table 1. Thickness, surface density, and resistance were measured. The material was placed in a 175°C oven for 30 minutes, and shrinkage was measured. Photographs were taken as illustrated in Figure 7B. [Examples]

[0059] The aluminum-coated biaxially oriented polyester film was obtained from All Foils Inc. and is designed for use in helium-filled party balloons. The aluminum coating retains helium for a longer period, extending the loft of the party balloons. Thickness, surface density, and resistance were measured and are shown in Table 1 below. The film was then subjected to a high-temperature soldering iron, as in Example 1. Small holes were formed by applying the soldering iron to the current collector. The diameter was measured and is included in Table 1. Thickness, surface density, and resistance were measured. The material was placed in a 175°C oven for 30 minutes and shrinkage was measured. Photographs were taken as illustrated in Figure 8A. Compared to Comparative Example 1, a commercially available aluminum current collector, this material is 65% thinner, 85% lighter, and recedes heat, thereby having the effect of blocking internal short circuits in lithium-ion cells with internal short circuits. [Examples]

[0060] We obtained Dreamweaver Silver 25, a commercially available lithium-ion battery separator. This is made by blending cellulose, polyacrylonitrile nanofibers, and polyester microfibers in a papermaking process and calendering it to a thin thickness. Next, a high-temperature soldering iron was applied to the separator in the same manner as in Example 1. No holes were formed when a thermometer was applied to the current collector. Thickness, surface density, and resistance were measured. The material was placed in an oven at 175°C for 30 minutes and shrinkage was measured. Compared to Comparative Examples 3-5 of the prior art, these materials have the advantage of not melting or shrinking in the presence of heat, so in lithium-ion batteries with internal short circuits, they do not retract and create a larger, more uniform internal short circuit, as shown in Figure 8B. [Examples]

[0061] We obtained a commercially available prototype lithium-ion battery separator, Dreamweaver Gold20. This was fabricated in a papermaking process by blending cellulose, para-aramid nanofibers, and polyester microfibers, and then calendered to a thin thickness. Next, a high-temperature soldering iron was applied to the separator in the same manner as in Example 1. No holes were formed when a thermometer was applied to the current collector. Thickness, surface density, and resistance were measured. The material was placed in a 175°C oven for 30 minutes, and shrinkage was measured. The advantages of this separator compared to the prior art separator are the same as in Example 2.

[0062] [Table 1]

[0063] Comparative Examples 1 and 2 are existing current collector materials that exhibit very low resistance, high surface density, and no reaction to exposure to high-temperature solder tips or to any shrinkage at 175°C.

[0064] Examples 1-3 are materials that have infinite resistance, low surface density, and melt when exposed to either 175°C or a high-temperature solder tip. They are excellent substrates for metallization according to the present invention.

[0065] Example 4 is an example of an aluminized polymer film exhibiting moderate resistance, low surface density, and shrinkage when exposed to 175°C or a high-temperature solder tip. This is an example of a potential cathode current collector composite film according to the present invention. In practice, and as shown in further examples, it may be desirable to impart a higher level of metallic coating for higher-power batteries.

[0066] Examples 5-6 are materials that have infinite resistance and low surface density, but exhibit very little shrinkage when exposed to 175°C or a high-temperature solder tip. They are examples of polymer substrates in the present invention when the metallized coating is thin enough that the thickness of the metallized coating decomposes under high-current conditions associated with short circuits. Furthermore, cellulose nanofibers and polyester microfibers undergo oxidation, shrinkage, and ablation at temperatures far lower than the melting temperatures of metal current collectors currently in use.

[0067] Example 5 further involves a polymer substrate made from a fiber, polyacrylonitrile, which swells upon exposure to a conventional lithium-ion carbonate electrolyte. This is also an example of the polymer substrate of the present invention, where swelling increases under heating, causing cracks in the metallized coating. As a result, the conductive paths are interrupted, improving cell safety by eliminating or significantly reducing the uniform conductive paths of the current collector when exposed to heat within the battery. [Examples]

[0068] The materials used in Example 5 were placed in the deposition position of the MBraun vacuum deposition system using an intermetallic crucible and aluminum pellets. The chamber was 3 x 10 -5 The chamber was evacuated to mbar. Power was increased until the aluminum melted, then the power was set so that the deposition rate was 3 angstroms / second. The deposition was run for 1 hour, with four samples rotating on the deposition plate. This process was repeated three times, so the total deposition time was 4 hours. The weight, thickness, and resistance (measured at DC and 1 kHz, with a 1-inch strip between electrodes 1 inch apart) of the samples were measured. These are shown in Table 2 below. Point resistance was also measured using a Hioki 3555 battery HiTester at 1 kHz, with the probe tip 1 inch away. The weight of added aluminum was calculated by dividing the weight added during the process by the area of ​​the sample. This was then divided by the density of the material to determine the average thickness of the coating. [Examples]

[0069] The nonwoven polymer substrate is made from polyethylene terephthalate microfibers with a flat cross-section, and processed using the Tappi T206 process at a rate of 20 g / m². 2 The material was produced by fabricating hand sheets. These hand sheets were then calendered using a 250°F hardened steel roll at a pressure of 2000 lbs / inch at 10 m / min. This material was then metallized according to the process of Example 7, and the same measurements were performed, which are reported in Table 2. [Examples]

[0070] The material from Example 5 was deposited according to the process of Example 7, except that the coating was performed for 60 minutes at a setting of 5 angstroms / second. The sample was then flipped over and the reverse side was coated using the same procedure. These materials were imaged using a scanning electron microscope (SEM) on both the surface and in cross-section, and the images are shown in Figure 9. [Examples]

[0071] The material was prepared according to the procedure of Example 9, except that the deposition time on each side was only 20 minutes. [Examples]

[0072] The polymer substrate of Example 8 was prepared, except that the sheet was not calendered. Aluminum deposition was performed at 5 angstroms / second for 20 minutes on each side. Because the material was not calendered, it had very high porosity and a very high resistance value with a thin coat weight. Comparing Example 11 to Example 8, the unexpectedly high advantages of calendering are demonstrated.

[0073] [Table 2] [Examples]

[0074] The aluminum-coated polymer substrate of Example 9 was coated with an N-methyl-2-pyrrolidone solution containing a mixture of 97% NCM cathode material (NCM523 obtained from BASF), 1% carbon black, and 2% PVDF binder. The coating weight was 12.7 mg / cm². 2 The thickness was 71 microns. This material was cut to fit the 2032 button cell and coated with a graphite anode (6 mg / cm³) on a copper foil current collector. 2 It was paired with 96.75% graphite (BTR), 0.75% carbon black, 1.5% SBR, and 1% CMC. The anode, separator (Celgard 2320), and NCM-coated material were placed in the cell, filled with electrolyte (60 μL, EC:DEC:DMC = 4:4:2vol + 2w%VC containing 1.0 M LiPF6), and the shell was pressed to seal the cell and fabricate a single-layer button cell. To obtain proper conductivity, a portion of the aluminum-coated polymer substrate from Example 9 was left uncoated with the cathode material, folded, and brought into contact with the shell of the button cell to complete the conductive path. The cell was formed by charging it to 4.2V with a constant current of 0.18 mA, and then charging it at a constant voltage (4.2 V) until the current decreased to 0.04 mA. The cell was cycled three times between 4.2V and 3.0V at 0.37mA, yielding an average discharge capacity of 1.2mAh. [Examples]

[0075] The cells were fabricated according to the procedure, using the materials of Example 12, except that the separator used was Dreamweaver Silver20. The cells were formed by charging them to 4.2V with a constant current of 0.18mA, and then charging them at a constant voltage (4.2V) until the current dropped to 0.04mA. The cells were cycled three times between 4.2V and 3.0V at 0.37mA to obtain an average discharge capacity of 0.8mAh. Thus, in this example and the previous examples, operable rechargeable lithium-ion cells were fabricated with an aluminum thickness of less than 1 micron.

[0076] Comparative Example 3 In Comparative Example 1, an aluminum tab approximately 2cm x 4cm in size was connected to the ground of the current source via a metal connector that made contact with the entire width of the sample. The voltage limit was set to 4.0V and the current limit to 1.0A. A probe connected to the high voltage of the current source was first touched to the metal connector that made contact with the entire width of the sample, and then touched to the aluminum tab multiple times, creating a short circuit at 1.0A. The tip of the probe was approximately 0.25mm. 2 The area was as follows. When the entire width was in contact, current flowed normally. When the probe was first touched to the tab, a spark was generated, indicating a very high initial current density. The resulting defects in the current collector sometimes resulted in small holes, and in other cases, there was ablation, but the current collector remained intact. In all cases, the circuit remained short-circuited with a current of 1.0A. Micrographs of ablated defects without holes were taken and are shown in Figure 10A. The experiment was repeated with current source limits set to 5.0, 3.0, 0.6A, 0.3A, and 0.1A, and in all cases, when the entire width of the current collector was in contact, and the tip size was approximately 0.25mm. 2 In all cases using the point probe, the result was continuous current at the test current limit.

[0077] Comparative Example 4 A copper tab of similar dimensions from Comparative Example 2 was tested in the same manner as in Comparative Example 3. When the entire width was in contact, current flowed normally. When the probe was first touched to the tab, a spark was generated, indicating a very high initial current density. The resulting defects in the current collector sometimes resulted in small holes, and in other cases, ablation occurred, but the current collector remained intact. In all cases, the circuit remained short-circuited with a current of 0.8A. Micrographs of ablated defects without holes were taken and are shown in Figure 10A. The experiment was repeated with current source limits set to 5.0, 3.0, 0.6A, 0.3A, and 0.1A, and in all cases, when the entire width of the current collector was in contact and the tip size was approximately 0.25mm. 2 In all cases using the point probe, the result was continuous current at the test current limit. [Examples]

[0078] A similarly sized aluminum-coated polymer substrate material of the present invention in Example 7 was tested using the same method as in Comparative Examples 3-4. When the probe was in full-width contact, current flowed normally. When the probe was directly applied to the current collector of the present invention, far fewer sparks were generated, and the current stopped flowing after the first spark, remaining in an open circuit. In all cases, the resulting defect was a hole. Micrographs of some examples of holes are shown in Figures 11A and 11B. The experiment was repeated with current source limits set to 5.0, 3.0, 0.6A, 0.3A, and 0.1A, and in all cases, when contact was made through the full-width connector, current flowed continuously, but when the probe was directly applied to the current collector of the present invention, no current flowed through the example of the present invention.

[0079] The main invention demonstrated is that, when exposed to a short circuit as in Comparative Examples 3-4 and Example 14, the prior art results in a continuous short circuit, whereas the inventive material results in an open circuit with no continuous current (i.e., no detectable current movement). Therefore, the short circuit in the prior art generates heat, melts the separator and dissolves the SEI layer, potentially leading to thermal runaway of the cell. The open circuit of the current collector of the present invention does not generate heat, thus providing a cell that can maintain an internal short circuit without allowing thermal runaway and the resulting smoke, heat, and flames. Examples 15 and 16 and Comparative Examples 5 and 6

[0080] Two metallized films were produced on a 10-micron polyethylene terephthalate film by a roll-to-roll process. In this process, a roll of film was placed in a vacuum metallization machine (an example of which is the Top Met 4450 available from Applied Materials), and the chamber was evacuated to a reduced pressure vacuum. The roll was passed at high speed, for example 50 m / min, over a heated boat containing molten aluminum. Above the heated boat containing molten aluminum, there was a plume of aluminum gas that deposited on the film at a deposition rate controlled by the speed and the aluminum temperature. A roll with a length of approximately 500 m and a width of 70 cm was produced in multiple passes until the aluminum coating reached -300 nm. The coating process was repeated to coat the opposite side of the film, and the resulting product was used as Example 15 in this specification (the current collector of the present invention in FIG. 4 depicts what was used in this example). In this way, Example 16 was produced in the same manner except that the metal in the boat was copper (including the figure in FIG. 5B representing the current collector utilized within the structure of this invention). The basis weight, thickness, and conductivity of each film were measured and reported in Table 3 below. The coating weight was calculated by subtracting 13.8 g / m 2 which is the basis weight of the 10-micron polyethylene terephthalate film. The "calculated coating thickness" was calculated by dividing the coating weight by the density of the material (2.7 g / cm 3 for aluminum and 8.96 g / cm 3 for copper) and assuming that the coating on each side was equal.

[0081] Comparative Example 5 is a commercially available aluminum foil with a thickness of 17 microns. Comparative Example 6 is a commercially available copper foil with a thickness of 50 microns. Comparative Example 7 is a commercially available copper foil with a thickness of 9 microns.

[0082]

Table 3

[0083] Examples 15, 16, Comparative Example 5, and Comparative Example 6 further tested the ability to carry very high current densities. A test apparatus was prepared that held a polished copper wire with a radius of 0.51 mm (24 AWG gauge) in contact with the film or foil of the current collector. The film or foil to be tested was grounded using an aluminum contact that was held in contact with the film or foil to be tested, with a contact area of ​​1 square centimeter or more. The probe was connected in series with a 0.335 ohm high-power 400 W resistor and connected to a Volteq HY3050EX power supply set to control the current. The current collector to be measured was placed in the setup using a polished wire that contacted the surface of the current collector with a zero input current. The current was increased in increments of 0.2 amperes, held for 30 seconds with each increment while the voltage across the resistor was measured. When the voltage dropped to zero, indicating that no more current was flowing, the sample was indicated to have failed. The tests for Examples 15, 16, Comparative Example 5, and Comparative Example 6 were performed respectively. Example 15 failed at 7A (average of two measurements). Example 16 failed at 10.2A (average of two measurements). Comparative Examples 5 and 6 both failed at less than 20A. Both Examples 15 and 16 showed holes with a radius of more than 1 mm in the current collector, but neither Comparative Example 5 nor Comparative Example 6 showed any damage to the foil. Tests in this example demonstrate the advantage of having a current collector that cannot carry currents exceeding 20A, preferably exceeding 15A, and more preferably exceeding 12A.

[0084] In another test, the current collectors of these inventions were intended to simulate a tab connecting the electrode stack of a cell to an electrical device in use (either inside or outside the cell), and Examples 15 and 16, as well as Comparative Examples 5 and 6, were subjected to current capacity testing along a strip. To prepare the test specimens, the current collectors were cut into the shape shown in Figure 12. This consisted of a 4 cm x 1 cm (4cm x 1cm) strip of material, with the ends of the strip being right-hand isosceles triangles with sides of 4 cm cut off. Each triangle of the test specimen was brought into contact with an aluminum piece with a contact area of ​​more than 1 cm. One side was connected via a 400 W, 0.335 ohm resistor, and this circuit was connected to a Volteq HY3050EX power supply. The voltage across the resistor was measured to measure the current, and it was shown that the test specimen failed when this voltage dropped to zero. In each test, the test specimen was connected with the power supply set to zero current, and the current was increased by 0.2A increments, with a 30-second interval between each new voltage until the specimen failed and the current flow dropped to zero. The test was configured so that measurements could be taken by contacting either one or both sides of the metallized current collector. The current at failure is shown in Table 4 below. For materials tested in 4cm x 1cm strips, it is advantageous to provide an internal fuse by limiting the amount of current that can flow at either one-sided or both-sided contacts to less than 20A, preferably less than 15A, and more preferably less than 10A.

[0085] [Table 4]

[0086] Examples 17-19 and Comparative Example 8 Cells were fabricated by coating standard foil current collectors and the metallized PET film current collectors of Examples 15 and 16 with electrode material. The NMC523 cathode material was prepared using an NMP solvent containing BASF NMC523 (97%), carbon black (2%), and PVDF (1%), and coated onto an aluminum current collector (15 micron aluminum current collector). Example 15 had a basis weight of 220 g / m². 2 And it's 3.3mAh / cm². 2 This corresponds to the cathode loading density. The anode material was prepared using an NMP solvent containing graphite BTR-918S (94%), carbon black (5%), and PVDF (1%), and loaded onto a copper current collector (18 micron copper current collector) at a density of 118 g / m². 2 It is coated with this, and this has an anode loading density of 4.0 mAh / cm². 2 This corresponds to the following. Four double-sided cathodes, three double-sided anodes, and two single-sided anodes were prepared. These were laminated with Celgard 2500 separators to form small pouch-type cells, which were filled with electrolyte and sealed with a design capacity of 1 Ah. The four types of cells were fabricated with various combinations of foil materials, and their capacities were measured at C / 10 and C / 5 (i.e., 0.1 A and 0.2 A). The cells were formed by charging them to 4.2 V at 100 mA and held at 4.2 V until the current dropped to 10 mA. Next, the weight of the fully formed cells was measured, and their capacities were tested by discharging at C / 10, then charging at C / 10, and then discharging at C / 5. These results are shown in Table 5 below.

[0087] [Table 5]

[0088] Therefore, the above example exhibits the desired thickness, metal coating, and conductivity required to prevent thermal runaway within batteries containing electrolytes, thereby providing a component that is not only far safer and more reliable, but is actually improved without sacrificing safety, and requires far less internal weight than before.

[0089] Although the present invention has been described in detail, it will be apparent that those skilled in the art can make changes and modifications without departing from the scope of the invention. Therefore, the scope of the invention should be determined solely by the claims appended herein.

[0090] Although the present invention has been described in detail, it will be apparent that those skilled in the art can make changes and modifications without departing from the scope of the invention. Therefore, the scope of the invention should be determined solely by the claims appended herein.

[0091] One aspect of the present technology is a method or process for manufacturing an energy storage device, comprising the steps of: providing an electrode having at least one metallized substrate having a coating of an ion storage material; providing a counter electrode; laminating an electrode and a counter electrode on opposite sides of each other and a separator component interposed between the electrode and the counter electrode; providing a package material comprising an electrical contact component, wherein the contact includes a portion located inside the package material and a portion located outside the package material; electrically connecting the electrical contact to the metallized substrate; introducing at least one liquid electrolyte containing ions inside the package material; and sealing the package material.

[0092] One embodiment of this technology is that the energy storage device may be a lithium-ion battery.

[0093] In some embodiments of this technology, the metallized substrate may be a current collector comprising a film having at least one metal coating, wherein the current collector has a total thickness of less than 20 microns. The metal may be, but is not limited to, copper or a transition metal such as aluminum.

[0094] Some embodiments of this technology are 50 grams / m². 2 It may have a total surface density of less than .

[0095] Embodiments of this technology may have at least one of the metallized substrates having a resistance greater than 5 milliohms / square and less than 1 ohm / square, and a coating thickness of less than 5 microns.

[0096] Some embodiments of this technology may have separators configured to not be destroyed when exposed to shrinkage tests below 200°C and to exhibit a shrinkage rate of less than 10% before 200°C, as described in Section 3.5 of NASA TM-2010-216099.

[0097] Embodiments of this technology may include an electrolyte containing an organic solvent.

[0098] Some embodiments of this technology may have a separator made of a polymer, ceramic, or nonwoven fabric structure.

[0099] Some embodiments of this technology may have an ion storage material coated on both sides of a metallized substrate.

[0100] Embodiments of this technology may have an electrical connection between an electrical contact and a metallized substrate having a surface area of ​​more than 1 square millimeter.

[0101] While embodiments of lithium energy storage devices with internal fuses have been described in detail, modifications and variations thereto are possible, and it is clear that all of them fall within the true spirit and scope of the present invention. With regard to the above description, the optimal dimensional relationships of the components of the present invention, including various sizes, materials, shapes, forms, functions, and methods of operation, assembly, and use, are considered to be readily apparent to those skilled in the art, illustrated in the drawings, and it should be understood that all equivalent relationships described in the specification are intended to be encompassed in this art.

[0102] Therefore, the foregoing should be considered merely illustrative of the principles of the present invention. Furthermore, since numerous modifications and changes are readily apparent to those skilled in the art, it is not desirable to limit the present invention to the exact structure and operation illustrated and described, and therefore all suitable modifications and equivalents can be used and are within the scope of the present invention.

Claims

1. An energy storage device comprising a sealed energy storage device container, the energy storage device container comprising, within the energy storage device container, an anode, a cathode, at least one polymer or fiber separator present between the anode and the cathode, at least one current collector in contact with at least one of the anode or the cathode but not in contact with the at least one polymer or fiber separator, and at least one liquid electrolyte, An energy storage device wherein at least one current collector comprises a conductive material coated on a polymer material substrate, and when operating normally along a current path horizontally along the current collector, the current collector exhibits the ability to carry a useful current density, and when exposed to a short circuit, the current collector is unable to hold a similar current through point contacts on the surface of the current collector, the polymer material is polyvinylidene fluoride or polyacrylonitrile configured to swell in the electrolyte, the swelling increases as the polymer material is heated, and the energy storage device does not exhibit a senseable current path.

2. The current along the horizontal path is at least 0.1 A / cm, and the current passing through the point contact is at most 5 A / mm². ２ The energy storage device according to claim 1.

3. The energy storage device according to claim 1, wherein the total thickness of the coated polymer substrate is less than 20 microns and the resistance is less than 1 ohm / square.

4. The energy storage device according to claim 3, wherein the conductive material has a total thickness of less than 5 microns.

5. The energy storage device according to claim 3, wherein the conductivity of the current collector is 1 milliohm / square meter to 1 ohm / square meter.

6. The energy storage device according to claim 1, wherein the device further comprises a separator, the separator exhibiting less than 5% thermal shrinkage after 1 hour at 200°C.

7. The energy storage device according to claim 3, wherein the device further comprises a separator, the separator exhibiting less than 5% thermal shrinkage after 1 hour at 200°C.

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