CN119542428A

CN119542428A - Batteries with metallized film current collectors having low internal resistance

Info

Publication number: CN119542428A
Application number: CN202411225624.3A
Authority: CN
Inventors: 布莱恩·G·莫林; 卡尔·C·胡
Original assignee: Sotria Battery Innovation Group
Current assignee: Sotria Battery Innovation Group
Priority date: 2019-11-27
Filing date: 2020-11-10
Publication date: 2025-02-28
Also published as: AU2020391409A1; EP3853930A1; WO2021108119A1; JP2023504032A; JP2023504031A; WO2021108118A1; KR20220122644A; CN113196532A; KR20220120583A; AU2020391357A1; EP3853931A1; CN113196533A; CA3162966A1; CA3163083A1

Abstract

The present invention provides a lithium electrochemical energy generation and storage device comprising a negative electrode, a positive electrode, at least one separator between the negative electrode and the positive electrode, an electrolyte, and at least one current collector in contact with at least one of the negative electrode and the positive electrode, wherein the current collector exhibits a resistivity of greater than 0.005 ohm/square, wherein the electrochemical device exhibits a 2C capacity of greater than 70% of the capacity measured at 0.5C, such current collector further comprising an insulating support layer coated with at least one conductive layer, wherein the conductive layer has a thickness of less than 2 microns.

Description

Battery with metallized film current collector having low internal resistance

The application is a divisional application of application number 202080006057.6, which is the application of "a battery with a metallized film current collector having low internal resistance", which is the application number 2020, 11 and 10.

Technical Field

The present technology relates to improvements in the structural components and physical characteristics of lithium battery articles, providing lower electrical resistance than standard rechargeable battery types (e.g., high power lithium ion battery types as one example). This structural modification involves a thinner metal current collector structure that increases the internal resistance level of the battery cell and accompanies a decrease in the internal resistance of the battery cell by modifying the electrode coating as a matter of adjustment. With low thickness electrodes, high porosity electrodes, higher conductivity electrode coatings, multilayer electrode coatings with different levels of conductive material, and patterned coatings with different resistive regions for orientation results, all of which function in this regard simultaneously with a thin metallized current collector. The invention also provides battery articles including these improvements and methods of use thereof. The present technology relates to a battery with a metallized thin film current collector having low internal resistance for reducing the internal resistance of a lithium ion battery.

Background

Rechargeable power cells (e.g., without limitation lithium ion cells) are still popular as a power source throughout the world, and are of increasing importance in numerous products. From rechargeable power tools to electric vehicles to ubiquitous cellular phones (e.g., tablet computers, handheld computers, etc.), lithium batteries (of different ion types) are used as the primary power source due to reliability, the recharging capability mentioned above, and long service life.

These problems are mainly due to manufacturing problems, whether a single cell assembly is made or such an assembly is itself configured as a single cell. By careful observation, lithium batteries are currently made of six main components, a positive electrode material, a positive electrode current collector (e.g., aluminum foil) coated with the positive electrode material, a negative electrode current collector (e.g., copper foil) coated with the negative electrode material, a separator between each negative electrode and the positive electrode layer, typically made of a plastic material, and an electrolyte as a conductive organic solvent saturating the other materials, thereby providing a mechanism for conducting ions between the negative electrode and the positive electrode. These materials are typically wound together in cans (as shown in prior art fig. 1) or stacked together. There are many other configurations that may be used for such battery production purposes including pouch cells, prismatic cells, button cells, cylindrical cells, wound prismatic cells, wound pouch cells, to name a few. These batteries can be charged and discharged thousands of times with proper fabrication and light weight and without any significant safety issues. However, as mentioned above, certain events, in particular certain defects, can lead to internal short circuits between the internal conductive materials, leading to heating and internal thermal runaway, which are known to be the ultimate cause of fires in such lithium batteries. As noted above, such events may also be caused by internal defects, including the presence of metal particles within the cell, burrs on the current collector material, fine points or holes in the separator (whether contained during subsequent processing or caused during subsequent processing), misalignment of the cell layers (leaving open undesirable electrical conductivity), penetration into the cell (such as road debris impacting a running vehicle), breakage and/or destabilization of the cell itself (e.g., due to an accident), charging of the cell in a confined space, and the like. In general, these types of defects are known to result in a small electron conduction path between the negative and positive electrodes. When such an event occurs, if the battery is subsequently charged, such a conductive path may result in discharge of the battery cell, which ultimately generates excessive heat, thereby damaging the battery structure and compromising the underlying device to which power is supplied. In combination with the presence of flammable organic solvent materials as battery electrolytes, which are generally necessary for battery operability, this excessive heat has been shown to cause ignition thereof, ultimately resulting in a very dangerous situation. Such problems are difficult to control at least once at the beginning and have resulted in serious injury to the consumer. By providing a battery that delivers electrical energy without damaging the flammable organic electrolyte in this manner, such potentially catastrophic situations can certainly be avoided.

The generation of excessive heat inside may further cause shrinkage of the plastic separator, causing it to move away from the battery, separate, or otherwise increase the short circuit area within the battery. In such cases, a larger exposed short circuit area within the cell may result in a sustained current and increased heat therein, resulting in high temperature events that can cause significant damage to the cell, including bursting, venting, or even flames and fires. Such damage is particularly problematic because of the possibility of fire and worse results that may occur quickly and may cause the battery and potentially underlying devices to be subject to explosion, thereby also presenting a significant hazard to the user.

Lithium batteries (of various types) are particularly prone to problems associated with short circuits. As mentioned above, typical batteries tend to exhibit increased discharge rates under high temperature exposure, sometimes resulting in uncontrolled (uncontrolled) combustion and ignition as described above. Because of these possibilities, certain regulations have been in effect to manage the actual use, storage, or even transportation of such battery items. Of course, the ability to implement the appropriate protocol to prevent runaway events associated with shorts is very important. However, as to how to actually solve such problems, particularly when part production is provided from numerous suppliers and many different locations around the world, problems still remain.

Some previous disclosures mention the use of metallized films as current collector structures in lithium ion batteries, including japanese patent application No. 11410796. Such disclosures, and others recently made, are very limited in providing internal resistance within the target power cell itself, without any other structural modifications as adaptations thereto. For example CATL has recently taught the use of current collecting films (metallizations) for safety purposes, however, as mentioned above, such use is limited to the effect of very thin metal coatings which are required to result in high internal resistances. Therefore, the present CATL disclosure is limited to defining the level required for the internal resistance R of the battery in relation to the battery capacity CAP as the product of r×cap is higher than a certain parameter, which is 40 in this case. However, in the present invention, and in all cases involving "capacity" of the battery, such measurements were made at a rate of 0.2C or less. Such high internal resistance may contribute to good safety performance of the lithium ion battery, because such an internal resistance level may reduce current when there is a short circuit caused by an internal short circuit or damage. Of course, the higher the internal resistance, the lower the current, which reduces the rate of heat generation due to short circuits, thereby reducing the possibility of thermal runaway of the battery being driven. Thus, it has now been recognized that such metallized film current collectors may be used in conjunction with power generation cells while exhibiting low internal resistance, which is quite novel and contrary to this particular CATL teaching (achieving high safety associated with the use of ultra-thin metal coatings on metallized films with high resistance results).

Therefore, it is generally believed that such a reduced amount of metal (e.g., from bulk to metallized film) necessarily contributes to increasing the internal resistance of the target power cell, thereby improving its safety. Thus, the only way to achieve such safety levels (e.g., to prevent thermal runaway) is to provide a battery with high internal resistance, and such high resistance levels are a source of increased safety in this regard, as a result of standards involving such metallized film utilization within lithium ion batteries, and the like.

However, it has been found that low internal resistance batteries are necessary to deliver or receive high power, essentially allowing for improved safety, but at the same time giving the industry the power levels required for the viability of such rechargeable batteries. For example, when referring to electric vehicles, there are indeed events that show problems associated with thermal runaway, due to short circuits caused by the manufacture and/or damage of the rechargeable battery itself. With the use of high internal resistance metallized film current collectors, this tendency for thermal runaway to occur is reduced, but the power is lost, thereby reducing the effectiveness and/or duration of effectiveness of recharging of the rechargeable battery, whereby high levels of activation and utilization are substantially compromised. In other words, to achieve efficient and quick charging in such an electric vehicle, high power reception is basically required. Also, it is difficult to achieve the feasibility and safety of the use with the sole goal of providing high internal resistance in such high power battery applications. Hybrid electric vehicles also require extremely fast charging capability, and therefore similar high power charge levels (while also requiring increased safety). In this regard, electric aircraft such as drones, taxis and the like require very high power levels to lift and land, at least for safety reasons. The same problem arises because it relates to the ability to rapidly charge batteries in cell phones, notebook computers and other devices, and of course to safety concerns that may be caused by short circuits and thermal runaway. In other words, the required safety needs to be achieved by a thinner metal current collector structure, but the latest technology in this respect compensates for the overcompensation in a way that the power level is too much impaired, making such limited thin film current collectors considered as a solution in the rechargeable power cell industry.

Furthermore, the ability to reduce the weight of the initial current collector structure by reducing the total weight of the target cell would certainly be helpful in some respects. Nevertheless, such limited modifications do not allow for high power enhancement, as such structural modifications would create high internal resistance in the target battery without further compensating for the power generation shortfall. This would be an unexpected advance as the weight is reduced and the ability to produce energy is further enhanced. However, to date, as mentioned above, the only weight saving of such power cells has been safety-related only by a high internal resistance increase. The present invention provides a very desirable solution that makes lithium batteries very safe, reliable and suitable for high power devices in multiple markets.

Accordingly, there is a need for a new and improved battery having a low internal resistance metallized film current collector that can be used to reduce internal resistance in lithium ion batteries. In this regard, the present technology essentially meets this need. In this regard, the low internal resistance battery with metallized thin film current collector in accordance with the present technology substantially departs from the conventional concepts and designs of the prior art and does so to provide a means developed primarily for reducing internal resistance in lithium ion batteries.

Disclosure of Invention

In view of the above-mentioned drawbacks inherent in energy storage devices of the type known in the art, the present technology provides an improved battery having a metallized thin film current collector with low internal resistance and overcomes the above-mentioned drawbacks and shortcomings of the prior art. Accordingly, the general purpose of the present technology (which will be described in more detail below) is to provide a new and improved battery and method of metallized thin film current collector with low internal resistance that has all of the advantages of the prior art described above and many new features that result in a battery having metallized thin film current collector with low internal resistance that is not anticipated, obvious, taught, or suggested by the prior art (either alone or in any combination thereof).

According to one aspect, the present technology may include a lithium electrochemical energy generation and storage device comprising a negative electrode, a positive electrode, at least one separator between the negative electrode and the positive electrode, an electrolyte, and at least one current collector in contact with at least one of the negative electrode and the positive electrode. The current collector exhibits a resistivity greater than 0.005 ohm/square. The electrochemical device exhibits a 2C capacity of greater than 70% of the capacity measured at 0.5C. The current collector also includes an insulating support layer coated with at least one conductive layer having a thickness of less than 2 microns.

According to another aspect, the present technology may include a lithium electrochemical energy generation and storage device comprising a negative electrode, a positive electrode, at least one separator between the negative electrode and the positive electrode, an electrolyte, and at least one current collector in contact with at least one of the negative electrode and the positive electrode. The current collector may exhibit a resistivity greater than 0.005 ohm/square. At least one of the negative electrode or the positive electrode is configured to achieve low resistivity by including at least one of a) an electrode having a thickness of less than 70 microns, b) an electrode coating including greater than 6 wt% conductive additive, c) an electrode coating exhibiting greater than 35% porosity, d) an electrode coating having multiple layers, and e) an electrode coating exhibiting a dispersed pattern of coating material. At least one component of the pattern includes a high energy, low conductivity region and at least one other component of the pattern includes a higher conductivity region. The conductivity may be obtained from a high conductive material content or the presence of a high porosity material.

According to another aspect, the present technology may include an energy storage device including a negative electrode and a positive electrode, a first separator interposed between the negative electrode and the positive electrode, an electrolyte, a first current collector in contact with at least one of the negative electrode and the positive electrode, a second current collector in contact with at least one of the negative electrode and the positive electrode, at least one electrode of the second current collector being opposite to at least one electrode of the first current collector, and a second separator in contact with the second current collector. At least one of the first current collector and the second current collector exhibits a resistivity greater than 0.005 ohm/square.

In some or all embodiments, the device may exhibit a resistance of less than 15 milliohms.

In some or all embodiments, the device may exhibit an electrode area energy density of less than 4.0mAh/cm ².

In some or all embodiments, the device may exhibit a product of the capacity CAP and the resistance R, where CAP R is less than 40mOhm-Ah.

Some or all embodiments may further include a tab connected to the first current collector and configured to contact the external contact.

In some or all embodiments, the first current collector and the second current collector each include a metal film coated thereon.

In some or all embodiments, the metal film of the first current collector is a different metal than the metal film of the second current collector.

In some or all embodiments, the metal film of at least one of the first current collector and the second current collector may have a coating thickness of less than 5 microns in total.

In some or all embodiments, the negative electrode and the positive electrode may be porous, exhibiting a porosity of at least 35%.

In some or all embodiments, the negative electrode and the positive electrode may each include an electrode coating containing greater than 6 wt% conductive additive.

In some or all embodiments, the negative electrode and the positive electrode may each have multiple layers, including a top layer having a higher electrical conductivity than each of the successive lower layers.

In some or all embodiments, the negative electrode and the positive electrode may each have multiple layers, including a top layer that exhibits a higher porosity than each of the successive lower layers.

In some or all embodiments, the positive electrode is a patterned electrode, wherein a portion of the positive electrode comprises a first region interspersed with a second region, wherein the first region has a first energy or first conductivity property and the second region has a second energy or second conductivity property that is greater than the first region, thereby creating a conductivity gradient.

According to another aspect, the present technology may include an electrochemical energy generation and storage device (power cell, rechargeable battery, etc.) comprising a negative electrode, a positive electrode, at least one separator between the negative electrode and the positive electrode, an electrolyte, and at least one current collector in contact with at least one of the negative electrode and the positive electrode. The current collector exhibits a resistivity of greater than 0.005 ohm/square (preferably greater than 0.01, more preferably greater than 0.015, and most preferably at least 0.025 ohm/square). The device exhibits a capacity CAP and a resistance R such that the product CAP x R is less than 40mOhm-Ah (preferably less than 35, more preferably less than 30, more preferably less than 25, most preferably less than 20 mOhm-Ah). The electrochemical device exhibits a 2C capacity (where 2C represents a 30 minute discharge and 0.2C represents a 5 hour discharge) of greater than 70% of the capacity measured at 0.2C (preferably greater than 75%, more preferably greater than 80%, still more preferably greater than 85%, and most preferably greater than 90%).

In some or all embodiments, the device may exhibit a resistance of less than 15 milliohms (preferably less than 12, more preferably less than 10, more preferably less than 8, even more preferably less than 6, most preferably less than 4 milliohms). Of course, larger batteries naturally exhibit lower internal resistances, and thus batteries with high capacity and low internal resistances are desired. Thus, the battery may have both a low resistance target and a capacity target, with higher resistance allowing lower capacity limits. The capacity may be limited to less than 5Ah, preferably less than 20Ah, more preferably less than 40Ah, even more preferably less than 100Ah, most preferably less than 200Ah. Examples of this may include batteries with limited capacities below 10Ah and resistances below 10 mOhms.

In some or all embodiments, the device may exhibit an electrode area energy density of less than 4.0mAh/cm ² (preferably less than 3.5mAh/cm ², more preferably less than 3.0mAh/cm ², more preferably less than 2.5mAh/cm ², even more preferably less than 2.0mAh/cm ², more preferably less than 1.5, most preferably less than 1.0mAh/cm ²). In such unique devices, the current collector exhibits a certain increased resistance while the overall device exhibits a certain reduced resistance, or alternatively, the capacitance and/or electrode area energy density meets certain limitations that have not been done in the past. This difference between the increase in resistance of the current collector and the different physical properties of the device associated with the electrode structure provides this novel measurement data, which simultaneously provides higher power (for charging and discharging) for the entire device with high resistance (low thickness and weight of the current collector).

In another aspect, the present technology may provide an electrode structure with a non-conductive current collector assembly that is a polymeric film or fabric having a metal layer on each of its top and bottom surfaces, wherein the negative electrode and/or the positive electrode (as an electrode, one of which is in contact with the current collector) is provided with one or more physical structures that a) a porous electrode exhibiting a porosity of at least 35% (more preferably at least 40%, more preferably at least 45%, even more preferably at least 50%, most preferably at least 55%), b) an electrode coating, wherein such coating comprises a higher loading or a higher conductivity additive within the electrode material, wherein the conductivity additive may be graphite, carbon, or the like, and is present at a loading of greater than 6 wt% (preferably greater than 8 wt%, more preferably greater than 10 wt%, most preferably greater than 12 wt%), and/or wherein the high conductivity material may further comprise metal particles and/or high conductivity materials (e) a high aspect ratio of the carbon nano-tube and/or carbon nano-fiber), c) an electrode exhibiting a higher conductivity gradient of the electrode material (e) a higher conductivity of the top layer or a higher conductivity additive is present at a higher than a higher conductivity gradient than a top layer of the top layer, a continuous region, or by different porosity measurements (where there is a higher and lower gradient).

In some or all embodiments, the patterned coating may be laid down by a variety of printing techniques, which are well known, that allow patterns of different materials to be obtained. Such a multilayer structure may be produced by multiple passes, one layer deposited per pass, or by co-extrusion of multiple layers of material through a single orifice or printhead.

According to another aspect, the present technology may provide an initial metallized thin film current collector that greatly limits the transfer time of the current level applied to the target current collector surface through the probe tip (so as to controllably simulate internal manufacturing defects, dendrites, or external events that cause internal shorts within the subject cell) to less than 1 second, preferably less than 0.01 seconds, more preferably less than 1 millisecond, most preferably perhaps even less than 100 microseconds, especially for larger currents.

In some or all embodiments, the current will be limited to an internal voltage of the battery of 5.0V, 4.5V, 4.2V or less, e.g., 4.0V or 3.8V, but a minimum of 2.0V.

In some or all embodiments, a metallized film current collector may be provided having a total thickness (overall metallized polymer substrate) of less than 20 microns, possibly preferably less than 15 microns, possibly more preferably less than 10 microns, possibly even more preferably less than 8 microns, possibly still more preferably less than 6 microns, possibly most preferably less than 4 microns, all resistivity measurements being greater than 0.005 ohm/square (preferably greater than 0.01 ohm/square, more preferably greater than 0.015 ohm/square, most preferably at least 0.025 ohm/square).

In some or all embodiments, the thin component may be configured to allow a short circuit to react with the metal coating and to be relative to the total resistance level to create a localized region of metal oxide immediately preventing current from moving further therefrom, creating excessive temperatures due to current spikes during such a short circuit. However, since the thin structure shows such a physical result, the resistance level remains high.

Some or all embodiments may include a temperature dependent metallic (or metallized) material that shrinks due to a heat source during a short circuit or that readily degenerates to a non-conductive material (e.g., aluminum oxide degenerated by an aluminum current collector, as one example) at specific material locations (as mentioned in a different manner above).

In some or all embodiments, the current collector may be configured to become thermally weak, in sharp contrast to aluminum and copper current collectors in use today, which are very thermally stable to high temperatures. As a result, alloys of metals having lower intrinsic melting temperatures may degrade at lower short circuit current densities, thereby improving the safety advantages of the disclosed lithium-based energy devices.

In some or all embodiments, the capacity of the battery may be limited to less than 10Ah, and the resistance less than 10 milliohms.

In some or all embodiments, the current collector may include a layer of conductive material, such as copper or aluminum, coated on a fiber or film that exhibits a relatively high shrinkage at a relatively low temperature.

In some or all embodiments, the current collector may include a thermoplastic film having a melting temperature of less than 250 ℃, or even 200 ℃, and may include polyethylene terephthalate, nylon, polyethylene, or polypropylene, as non-limiting examples.

In some or all embodiments, the current collector may include a layer of conductive material, such as copper or aluminum, coated on the fibers or films, which may expand or dissolve in the electrolyte when the material is heated to a temperature relatively high compared to the operating temperature of the battery but low compared to the temperature that may cause thermal runaway, as described above.

In some or all embodiments, the polymer configured to swell in the lithium ion electrolyte may be polyvinylidene fluoride or polyacrylonitrile.

In some or all embodiments, the internal electrical fuse generation process may coat a metal (e.g., aluminum) on a substrate configured to oxidize under heat, the total metal thickness being much lower than that typically used for lithium batteries. The thin aluminum current collector may include a coating having a total thickness of less than 5 microns, less than 2 microns, less than 1 micron, or less than 700nm or 500 nm. The coating may include a sufficient amount or thickness of metal to provide sufficient conductivity to energize the battery. The thickness may be greater than 10nm, preferably greater than 50nm, or even greater than 100nm, or greater than 200nm.

In some or all embodiments, the areal density may be less than 30 grams per square meter, preferably less than 25 grams per square meter, more preferably less than 20 grams per square meter, and most preferably less than 15 grams per square meter.

In some or all embodiments, the opening of the conductive path may be achieved by providing a current collector of limited conductivity that will degrade at high current densities around the short circuit, similar to the degradation found in commercial fuses today. This may be achieved by providing a thin film metallized film current collector having a resistivity greater than 5 milliohms/square, or 10 milliohms/square, or potentially preferred greater than 20 milliohms/square, or potentially preferred greater than 50 milliohms/square.

In some or all embodiments, the opening of the conductive path may be achieved by providing a current collector that will oxidize to a non-conductive material at a temperature below that of aluminum, rendering the current collector inert in the short circuit region before the separator degrades.

In some or all embodiments, the metal in the thin current collector layer capacitance may be any metal that exhibits electrical conductivity, including but not limited to gold, silver, vanadium, rubidium, iridium, indium, platinum, and other metals (basically, by a very thin current collector layer, the costs associated with the use of such metals may be substantially reduced without sacrificing electrical conductivity, but still allowing for prevention of thermal runaway potentials during a short circuit or similar event). Likewise, layers of different metals may be used, or even discrete metal regions deposited internally or as a separate layer assembly may be used.

In some or all embodiments, one side of the coated current collector substrate may include a different metal species than the opposite side, and may also have a different layer thickness in comparison.

In some or all embodiments, the interface to the metal of the metallized substrate that allows high current may be achieved by face-to-face contact, thereby providing a high surface area between the device that makes electrical contact through the housing and the metallized substrate. The surface area may be higher than 1 square millimeter (10 ^-12 square meters), or higher than 3 square millimeters, or even higher than 5 square millimeters or more preferably higher than 10 square millimeters.

Many objects, features and advantages of the present technology will be apparent to those of ordinary skill in the art upon reading the following detailed description of the presently preferred, but nonetheless illustrative, embodiments of the present technology in conjunction with the accompanying drawings. In this regard, before explaining the present embodiments of the technology in detail, it is to be understood that the technology is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The inventive technique can be implemented and realized in numerous ways, as well as in other embodiments. Further, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

Thus, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present technology. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present technology.

It is another object of the present technology to provide a new and improved battery with a metallized film current collector that has low internal resistance and is easy to manufacture and sell efficiently.

It is another object of the present technology to provide a new and improved battery with a metallized film current collector that has low internal resistance, has lower manufacturing costs in terms of materials and labor, and is therefore easy to sell to consumers at a low price, thereby making such a battery with a metallized film current collector having low internal resistance economically available to purchasers.

It is another object of the present technology to provide a novel battery with a low internal resistance metallized thin film current collector that provides several advantages in the prior art apparatus and methods while overcoming some of the disadvantages normally associated therewith.

These and other objects of the present technology, as well as various novel features of the present technology, are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the technology of the present invention, its operating advantages and specific objects attained by its uses, reference should be had to the accompanying drawings and descriptive matter in which there are illustrated embodiments of the technology of the present invention.

Drawings

The present invention will be better understood and other objects than those set forth above will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings wherein:

fig. 1 is a prior art schematic view of the structure of a wound battery, such as 18650 battery.

Fig. 2 is a prior art diagram of a side perspective view of the use of thick-coated electrodes on a metallized thin film current collector.

Fig. 3 is a side perspective view of a thin-coated electrode for use in a metallized thin-film current collector of the present disclosure.

Fig. 4 is a top cross-sectional view of a gel rolled lithium ion rechargeable battery including the electrode/metallized film current collector of fig. 3.

Fig. 5 is a prior art diagram of a side perspective view of the use of a low porosity coated electrode on a metallized thin film current collector.

Fig. 6 is a side perspective view of a high porosity coated electrode for use in a metallized thin film current collector in accordance with the present disclosure.

Fig. 7 is a top cross-sectional view of a jelly-roll lithium-ion rechargeable battery including the high porosity electrode/metallized thin film current collector of fig. 6.

Fig. 8 is a side perspective view of a multilayer electrode for use on a metallized film current collector in accordance with the present disclosure.

Fig. 9 is a top cross-sectional view of a jelly-roll lithium-ion rechargeable battery including the multi-layer electrode/metallized film current collector of fig. 8.

Fig. 10 is a side perspective view of a patterned coated electrode for use in a metallized thin film current collector in accordance with the present disclosure.

Fig. 11 is a top cross-sectional view of a jelly-roll lithium-ion rechargeable battery including the patterned electrode/metallized film current collector of fig. 10.

Like reference symbols in the various drawings indicate like elements.

Detailed Description

A significant advantage of the present invention is the ability to provide a mechanism by the structural members to shut off the conductive path when an internal short circuit occurs, thereby stopping or greatly reducing the current that may generate heat within the target cell.

Another advantage is the ability to provide such a protective form within a lithium battery cell, which also provides beneficial weight and cost improvements for overall battery manufacturing, transportation and utilization. Thus, another advantage is that the internal fuse structure is created and maintained within the target cell until it is needed to be activated. Another advantage is to provide a low internal resistance high power battery with a high resistance thin metal current collector for rapid charge and discharge capability. Yet another advantage is the ability to utilize flammable organic electrolyte materials within the battery without any significant propensity to fire during short circuits or similar events.

Accordingly, the present disclosure includes an electrochemical energy generation and storage device (power cell, rechargeable battery, etc.) comprising a negative electrode, a positive electrode, at least one separator between the negative electrode and the positive electrode, an electrolyte, and at least one current collector in contact with at least one of the negative electrode and the positive electrode, wherein the current collector exhibits a resistivity of greater than 0.005 ohm/square (preferably greater than 0.01 ohm/square, more preferably greater than 0.015 ohm/square, most preferably at least 0.025 ohm/square), wherein the device exhibits a capacity CAP and a resistance R such that the product CAP×R is less than 40mOhm-Ah (preferably less than 35, more preferably less than 30, more preferably less than 25, most preferably less than 20 mOhm-Ah), wherein the electrochemical device exhibits a 2C capacity (wherein 2C represents a 30 minute discharge, 0.2C represents a 5 hour discharge) of greater than 70% of the capacity measured at 0.2C (preferably greater than 75%, more preferably greater than 80%, more preferably greater than 85%, most preferably greater than 90%). Or such a device may exhibit a resistance of less than 15 milliohms (preferably less than 12 milliohms, more preferably less than 10 milliohms, more preferably less than 8 milliohms, even more preferably less than 6, most preferably less than 4 milliohms). Of course, larger batteries naturally exhibit lower internal resistances, and thus it is desirable to obtain batteries of high capacity and low internal resistances. Thus, the battery may have both a low resistance target and a capacity target, with higher resistance allowing for lower capacity limitations. The capacity may be limited to below 5Ah, preferably below 20Ah, more preferably below 40Ah, even more preferably below 100Ah, and most preferably below 200Ah. Such examples may include cells with capacity limited below 10Ah and resistance below 10 milliohms. Or such devices may also exhibit less than 4.0mAh/cm ² (preferably less than 3.5mAh/cm ², more preferably less than 3.0mAh/cm ², more preferably less than 2.5mAh/cm ²), Even more preferably less than 2.0mAh/cm ², more preferably less than 1.5mAh/cm ², and most preferably less than 1.0mAh/cm ²). In this unique device, the current collector exhibits some increased resistance while the overall device exhibits some reduced resistance, or alternatively, the capacity and/or electrode area energy density meets certain limitations that have not been done in the past. This difference between the increase in resistance of the current collector and the different physical characteristics of the device associated with the electrode structure provides this novel measure, which at the same time provides higher power (for charging and discharging) for the whole device with high resistance (low thickness and weight of the current collector).

Regarding such electrochemical power generation and storage devices, it has further been considered and unexpectedly found that the ability to provide electrode structures with non-conductive current collector components such as polymer films or fabrics, each having a metal layer on their upper and lower surfaces, wherein the negative electrode and/or the positive electrode (as electrode in contact with the current collector) is provided with one or more physical structures of a) porous electrodes having a porosity of at least 35% (more preferably at least 40%, more preferably at least 45%, even more preferably at least 50%, most preferably at least 55%), b) electrode coatings, wherein such coatings comprise a higher loading or higher conductivity additive within the electrode material, wherein the conductivity additive may be graphite, carbon, etc., and wherein the loading is greater than 6% by weight (preferably greater than 8% by weight, more preferably greater than 10% by weight, most preferably greater than 12%) and/or wherein the high aspect ratio conductive material may further comprise metal particles and/or high aspect ratio conductive materials (e.g. nanotubes and/or carbon nanofibers), c) electrodes, wherein the top layer (or each layer) has a higher conductivity than a measured value of each layer of the top layer exhibits a higher conductivity, wherein the high conductivity is not a gradient of the same type as the top layer is achieved by a higher conductivity of the continuous region, in which there is a higher and lower gradient. Such patterned coatings may be laid down by various printing techniques that allow patterns of different materials to be achieved, as is well known in the art. Such a multilayer structure may be produced by multiple passes, each depositing one layer, or by coextrusion of multiple layers of material through a single orifice or printhead.

It is therefore another significant advantage of the present invention to provide an initial metallized thin film current collector that greatly limits the transfer time of the current level applied to the target current collector surface (so as to controllably simulate the effects of internal manufacturing defects, dendrites, or external events that cause internal shorting of the target cell) by the probe tip for less than 1 second, preferably less than 0.01 seconds, more preferably less than 1 millisecond, most preferably, perhaps even less than 100 microseconds, especially for larger currents. Of course, such current would be limited to the internal voltage of the battery, which may be 5.0V, or 4.5V, or 4.2V or even lower, e.g., 4.0V or 3.8V, but a minimum of 2.0V.

Metallized thin film current collectors may be provided having a total thickness (overall metallized polymer substrate) of less than 20 microns, possibly preferably less than 15 microns, possibly more preferably less than 10 microns, possibly even more preferably less than 8 microns, possibly still more preferably less than 6 microns, possibly most preferably less than 4 microns, all resistivity measurements being greater than 0.005 ohm/square (preferably greater than 0.01 ohm/square, more preferably greater than 0.015 ohm/square, most preferably at least 0.025 ohm/square). Typical current collectors may exhibit these characteristics, but are much heavier than current collectors made with reinforced polymer substrates, and do not have the inherent safety advantages of such disclosed variants. For example, a 10 micron thick copper foil may weigh 90 grams per square meter. However, the weight of the copper-plated foil can be as low as 50 g/square meter, even as low as 30 g/square meter, even below 20 g/square meter, all while providing the proper electrical performance required for proper operation of the battery (although the device itself has a high internal resistance). However, in this alternative construction, the very thin component also allows the short to react with the metal coating and create localized areas of metal oxide relative to the total resistance level that immediately resist further current movement therethrough, creating excessive temperatures during such short-circuiting due to current spikes. However, as thin structures exhibit such physical results, the resistance level remains high.

Another possible option for such high resistance current collectors is to provide a temperature dependent metallic (or metallized) material that shrinks in a short time due to a heat source or that is easily degraded to a non-conductive material (e.g., aluminum oxide degraded by an aluminum current collector as an example) at a specific material location (as mentioned in a different manner above). In this way the current collector becomes thermally weak, in sharp contrast to the aluminium and copper current collectors used today, which are very stable at high temperatures. As a result, alloys of metals having lower intrinsic melting temperatures may degrade at lower short circuit current densities, thereby improving the safety advantages of the disclosed lithium-based energy devices. Another option is to manufacture the current collector by coating a layer of conductive material (e.g. copper or aluminum) on a fiber or film that exhibits a relatively high shrinkage at relatively low temperatures. Examples include thermoplastic films having a melt temperature of less than 250 ℃ or even 200 ℃, which may include polyethylene terephthalate, nylon, polyethylene, or polypropylene as non-limiting examples. Another possible way to achieve this result is to manufacture the current collector by coating a layer of conductive material (e.g. copper or aluminum) on the fibres or films as described above, which will expand or dissolve in the electrolyte when the material is heated to a relatively high temperature compared to the operating temperature of the battery but low compared to a temperature that may lead to thermal runaway. Examples of such polymers that can expand in lithium ion electrolytes include polyvinylidene fluoride and polyacrylonitrile, but other polymers known to those skilled in the art also exist. Another way to achieve this alternative internal electrical fuse creation process is to coat the substrate with a metal such as aluminum that oxidizes under heat, with a much lower total metal thickness than is commonly used for lithium batteries. For example, very thin aluminum current collectors in use today may be 20 microns thick. Coatings with a total thickness of less than 5 microns will interrupt the circuit faster, while coatings with a total thickness of less than 2 microns, or even less than 1 micron, or even less than 700 nanometers or less than 500 nanometers will interrupt the circuit faster. Such a coating must also have sufficient metal to provide sufficient conductivity to excite the cell, and therefore should be greater than 10nm thick, preferably greater than 50nm thick, even greater than 100nm thick, or most preferably greater than 200nm thick. The use of such a thin conductive coating, when combined with a low thickness polymer substrate, will result in an extremely low current collector area density. Thus, the areal density may be less than 30 grams per square meter, preferably less than 25 grams per square meter, more preferably less than 20 grams per square meter, most preferably less than 20 grams per square meter. Even so, another way to achieve a conductive path interruption is to provide a current collector with limited conductivity that will degrade at high current densities around the short circuit, similar to the degradation found in commercial fuses today. This may be achieved by providing a thin metallized film current collector having a resistivity greater than 5 milliohms/square, or 10 milliohms/square, or potentially preferred greater than 20 milliohms/square, or potentially preferred greater than 50 milliohms/square. As described above, such a resistor also produces a high internal resistance that may itself, without any compensation, impair the power generation and transport capabilities of the target battery. To overcome this challenge of high resistance, past improvements simply changed the resistance of the current collector. These relate to thickness and material and do not take into account any changes to the electrode type, thickness, material, or for that matter, it is possible to further select different resistivities for batteries designed for high power, batteries that may use relatively low resistance compared to batteries designed for low power and high energy, and/or that may use relatively high resistance. Another way to achieve a break in the conductive path is to provide a current collector that will oxidize to a non-conductive material at a temperature well below that of aluminum, rendering the current collector inert in the short-circuit area before the separator degrades. Certain aluminum alloys oxidize faster than aluminum itself, and these alloys degrade the conductive path faster or at lower temperatures. As a possible alternative, any type of metal that has such a thin collector layer capacity and exhibits conductivity may be used, including but not limited to gold, silver, vanadium, rubidium, iridium, indium, platinum, and others (basically, having a very thin collector layer, the costs associated with the use of such metals may be substantially reduced without sacrificing conductivity, but still allowing for prevention of thermal runaway potentials during a short circuit or similar event). Likewise, layers of different metals may be used, or even discrete metal regions deposited internally or as a separate layer assembly may be used. Of course, as such, one side of such a coated current collector substrate may comprise a different metal species from the opposite side and may also have a different layer thickness in comparison.

In any event, the ability to utilize metallized thin film current collectors (relative to thick metal structures) helps reduce the likelihood of thermal runaway of the rechargeable battery (e.g., as disclosed in co-pending U.S. patent application No. 15/700077, the entire contents of which are incorporated herein by reference). However, as also previously described, such thin structures create high resistance levels for the target electrochemical cell (battery, etc.), which compromises the ability of the device to provide high power, fast charge and fast discharge as desired in certain end use applications. It is therefore desirable to provide a method of reducing the overall resistance of the device itself, particularly when liquid electrolyte batteries are involved. The present invention is directed to such improvements in this respect. Standard electrochemical cells include a current collector structure, a separator, and electrodes (negative and positive) for generating an electrical charge. The application of metallized films as current collectors is limited to standard structures with typical electrode structures and separators (note the japanese references cited above). These typical electrodes are metal layers of significant thickness to provide overall stability of the cell (device) and to allow for high resistance levels inside. However, in contrast to these standard cells (electrochemical devices), it has been unexpectedly found that certain unexplored electrode material coatings are used on metallized thin film current collectors. Thus, different ways of providing such thin current collectors on such current collectors for safety (and high resistance levels) are now presented, with such material coatings thereon to provide an effective resistance reducing structure for rapid power generation and so rapid movement to external devices.

For this reason, as noted above, materials found to be relevant to such unexpectedly and abnormally used resistance-reducing electrodes depend on the coatings applied to the metallized current collector film, including those having a specific thickness, a high level of porosity, a high level of conductivity, a multi-layer structure having a conductive gradient, and patterned coatings having regions of different conductive gradients. In each instance, this new approach not only provides lower internal resistance of the target electrochemical cell, but also provides the possibility of significantly reducing the weight of such structures (in this regard, as well as in combination with the current collector film), thereby compensating not only for the increase in resistance associated with the thin current collector metallized film, but also providing an attractive weight saving for the overall cell (device).

These advantages allow for low weight, high safety levels, and high power generation (charge and discharge) rechargeable electrochemical cells (lithium ion cells, as non-limiting examples, etc.) that heretofore have not been available in the relevant industry. In any of the alternative configurations discussed herein, such metallized film current collectors act superficially as internal fuses within a target energy storage device (e.g., lithium battery, capacitor, etc.). In each case (alternative), the electrode coating applied thereto enhances the overall thin structure to a level that gives sufficient strength to the structural stability within the target cell (device), but at the same time has the ability to reduce the internal resistance of the overall cell relative to the resistance of the increased metallized film current. Thus, the ability to simultaneously provide safety measures related to short circuits and potential thermal runaway events and produce significantly high power generation results meets a heretofore unexplored need.

These methods and structures are discussed in more detail below.

The ion storage material may be, for example, a positive or negative electrode material of a lithium ion battery, as is well known in the art. The positive electrode material may include lithium cobalt oxide LiCoO ₂, lithium iron phosphate LiFePO ₄, lithium manganese oxide LiMn ₂O₄, lithium nickel manganese cobalt oxide LiNi _xMn_yCo_zO₂, lithium nickel cobalt aluminum oxide LiNi _xCoAl_zO₂, or mixtures thereof, or other materials known in the art. The negative electrode material may include graphite, lithium titanate Li ₄Ti₅O₁₂, hard carbon, tin, silicon, or mixtures thereof or other materials known in the art. Further, the ion storage material may include materials used in other energy storage devices (e.g., supercapacitors). In such supercapacitors, the ion storage material will include activated carbon, activated carbon fibers, carbide derived carbon, carbon aerogel, graphite, graphene, and carbon nanotubes.

The coating process may be any coating process known in the art. Knife rolls and slot dies are common coating processes for lithium ion batteries, but other processes may be used, including electroless plating. In the coating process, the ion storage material is typically mixed with other materials, including binders such as polyvinylidene fluoride or carboxymethyl cellulose or other film forming polymers. Other additives of the mixture include carbon black and other conductive additives.

The means of connection in electrical contact with the metallized substrate may include conventional means such as welding, tape bonding, clamping, stapling, riveting or other mechanical means. Since the metal of the metallized substrate can be very thin to achieve an interface that allows high current flow, face-to-face contact is often required to provide a high surface area between the manner in which electrical contact is made through the housing and the metallized substrate. In order to carry sufficient current, the surface area should be greater than 1 square millimeter (10 ^-12 square meters), but may need to be greater than 3 square millimeters, even 5 square millimeters or more preferably 10 square millimeters.

The liquid electrolyte is typically a combination/mixture of a polar solvent and a lithium salt. As described above, the common polar solvents include propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and the like, but other polar solvents including ionic liquids and even water may also be used. Lithium salts commonly used in the industry include, but are not limited to LiPF ₆、LiPF₄、LiBF₄、LiClO₄ and the like. The electrolyte may also contain additives known in the art. In many cases, the electrolyte may be flammable, wherein the safety features of the metallized substrate current collector of the present invention may be advantageous in preventing dangerous thermal runaway events that result in fires and damage to the cell and the outside of the cell.

Although embodiments of a battery having a metallized film current collector with low internal resistance have been described in detail, it will be apparent that modifications and variations thereof are possible, all of which are within the true spirit and scope of the present technology. With respect to the above description, it will be realized that the optimum dimensional relationships for the parts of the technology, to include variations in size, material, shape, form, function and manner of operation, assembly and use, are deemed readily apparent and obvious to one skilled in the art, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed by the present technology.

The following description and examples are merely representative of potential embodiments of the invention. Those of ordinary skill in the art will readily understand the scope of this disclosure and its breadth in the following claims.

As noted above, the present invention is a significant transition and is contrary to all previous understanding and remedies within the lithium battery (and other energy storage device) industry. Conversely, the novel devices described herein provide a number of beneficial results and properties within this area that have not heretofore been explored (not to mention unexpected). Initially, although by way of comparison, it is important to note the significant differences involved between the existing devices and the devices presently disclosed and broadly contemplated by the present invention.

Such counterintuitive examples and the results produced thereby are related to the heretofore unexplored significant changes in the application and use of unique coupling of electrode materials to metallized thin film current collectors within electrochemical cells (rechargeable batteries, capacitors, etc.). Examples of such novelty include at least five different alternatives, as detailed below.

Alternative 1-thin electrode coating

The electrode is typically produced by applying an electrode material on a current collector. In general, very high power batteries can be manufactured by using a thick metal foil and coating a thin electrode coating thereon, thereby reducing the internal resistance of the battery to such an extent that power can be introduced and removed quickly.

However, in contrast, this standard practice is to use a metallized thin film current collector and apply it with an extremely thin coating of electrode material, as disclosed herein. As discussed in the present invention, this counterintuitive approach and practice results in an unexpectedly effective reduction in the internal resistance of the target cell, particularly compared to the results typically obtained using thick metal current collectors. This is in contrast to current practice where thick coatings are combined with thin metal plates to form high energy density cells, while thin coatings are applied to thick metal plates to form high power cells. Thus, the combination of an ultra-thin current collector metal coating and a thin electrode material is also contrary to the current technology and results in an unexpectedly safe battery with low internal resistance for very high power potentials. Furthermore, according to the most advanced standard practice, thicker coatings are utilized to reduce the surface area of the target current collector, thereby reducing the overall weight of the battery in kWh energy storage form. Also counterintuitive, it has been unexpectedly found that the electrode coating thickness can also be significantly reduced when compared to foil-type current collectors using a current collector with a greatly reduced weight, resulting in the above-described reduction in internal resistance of the cell without increasing the total weight per kWh of the target cell. Such results, and the low level of resistance obtained by the application of thin electrode coatings to ultra-thin current collectors, are not intended to be bound by any particular scientific theory, and are clearly related to the ability of ions and electrons to rapidly pass through the thin electrode (conductive) coating, thereby reducing its resistance to the high power result levels required by the target cell itself.

To achieve such a result, the electrical resistivity of the metallized film (thin) current collector must be greater than 0.005 ohm/square (preferably greater than 0.01 ohm/square, more preferably greater than 0.015 ohm/square, most preferably greater than 0.025 ohm/square, and up to about 0.5 ohm/square). Thus, current collector resistivity is also a feature of the target electrochemical cell in which such current collectors are present, as low measurements are the starting point before any further adjustments and modifications of the electrode coating application.

In terms of electrode area energy density, application of the electrode coating is performed in the alternative method of cell resistance reduction of the present invention (less than 4mAh/cm ², preferably less than 3.5, more preferably less than 3, still more preferably less than 2.5, even more preferably less than 2, still more preferably less than 1.5, most preferably less than 1), electrode coating thickness (preferably less than 70 microns, more preferably less than 60 microns, more preferably less than 50 microns, even more preferably less than 40 microns, most preferably less than 30 microns), and/or electrode coating area density less than 150g/m ², preferably less than 120g/m ², more preferably less than 100g/m ². In other words, the use of electrode materials exhibiting such area energy densities, coating thicknesses, and/or coating area densities provides unexpected results that yield low cell internal resistances, even in the presence of high resistance ultrathin current collectors.

This combination of an ultra-thin current collector and an ultra-thin electrode coating provides an electrochemical device exhibiting a product of capacity CAP and resistance R, CAP x R being less than at most 40mOhm-Ah (preferably at most 35, more preferably at most 30, more preferably at most 25, most preferably at most 20). Other ultra-thin current collector electrochemical cell devices require high electrical resistance associated with cell capacity. Contrary to this previous teaching, however, the use of extremely thin electrode coatings provides an overall low resistance even in the simultaneous presence of high resistance ultrathin current collectors. Thus, the thin electrode coating on the disclosed ultra-thin current collector further yields an electrochemical device with a total (overall) resistance measurement of less than 15 milliohms, preferably less than 12, more preferably less than 10, still more preferably less than 8, even more preferably less than 6, still more preferably less than 4, most preferably less than 2. Likewise, as an alternative measure of the capacity of such a high safety/low resistance electrochemical cell (or device) is a capacity where the measured capacity at 2C (30 minutes discharge) is > P x 0.5C capacity (measured at 2 hours discharge) (where P is at least 90%, preferably at least 85%, more preferably at least 80%, more preferably at least 75%, most preferably at least 70%). Also, another measurement for this novel high safety/low resistance (high power) electrochemical device is where the 4C (15 minute discharge) capacity > P x 0.5C capacity, where P is the measurement as described above.

Of further interest is the ability of lithium ion batteries to achieve safety goals with ultra-thin current collectors, however, as noted above, such structures suffer from high internal resistance and subsequent high voltage drop at high currents. As mentioned above, this disadvantage is unexpectedly and again effectively compensated for with low coating thickness electrodes. For capacity C of a lithium ion battery cell, the current can be measured as a C ratio (commonly referred to as the ratio of the current used to the current required to drain the battery in 1 hour). High internal resistance batteries perform poorly at C-rates greater than 1C, with significantly lower capacities measured at 2C or 4C. Therefore, it is difficult to realize that a battery made of a very thin metal current collector exhibits high capacity at 2C or 4C. In contrast, however, the application of a thin electrode coating to an ultra-thin current collector has a surprisingly opposite effect, allowing for significantly improved and viable high capacity measurements. To date, no other way is to achieve such results than to effectively provide reduced internal resistance by the methods and operations disclosed herein for such batteries.

This combination of measurement and physical properties with ultra-thin current collectors has not been achieved in the past. Thus, by applying such thin electrode coatings as described above to such ultra-thin current collectors, the safety aspects associated with such current collectors are preserved, but the internal resistance of the target cell is unexpectedly and effectively reduced to achieve high power charging and discharging, as is required for end-use rechargeable electrochemical cells that are at least not currently available.

Fig. 2 shows a prior art structure of a thick-coated electrode 11 applied to an ultra-thin current collector 12. Again, this structure will exhibit high resistivity inside an electrochemical cell (lithium ion cell, as one non-limiting example).

Fig. 3 thus shows a reduction in the thickness 15 of the electrode coating applied to the ultra-thin current collector 16. As described above, this counterintuitive operation (within the state and criteria of the rechargeable electrochemical cell) compensates for the high resistance exhibited by the ultra-thin current collector by imposing an internal low resistance (as shown in fig. 4) within the target cell.

Fig. 4 thus shows the inclusion of such an ultra thin aluminized current collector 21 within a battery cell 20. Applied to the collector 21 is shown a thin positive electrode coating 22, a first separator 23 and an opposing thin negative electrode coating 24. Also present are a second ultra-thin copper plated film current collector 21a and a second separator 23a. Connected to the aluminized current collector 21 is an inner tab 25 for contact with an external contact (not shown) for charge transfer. As described throughout, such a battery 20 exhibits a safety level associated with the presence of ultra-thin current collectors and a high power capacity associated with counterintuitive use and application of thin electrode coatings on such current collector surfaces.

The above-described measurements, points of interest and illustrations of the metallized film current collector of alternative 1 should also be understood to be the same as the other alternatives provided below. Thus, the current collectors described herein should at least be considered identical for all such alternatives in terms of structure and physical properties (in particular avoiding the repetition of the same paragraph above).

Alternative 2-high porosity coating

It has also been found that the ability to reduce the electrical path length required for ions and electrons to pass through an electrode coating by reducing the coating thickness can also be achieved by applying a high porosity electrode coating to such ultra-thin current collector surfaces. In this way, without intending to be bound by any scientific theory in particular, it appears that this low total resistivity of the target cell is achieved by ions and electrons to regulate the majority of the travel distance through such electrode coating by the porous structure, as opposed to the typical low porosity type. This structural adjustment also appears to allow more liquid electrolyte to penetrate deeper into the electrode, thereby significantly allowing electron transport through the positive electrode solids to be reduced while still maintaining the high energy density associated with thicker coatings (even though the energy storage of the coating may be somewhat reduced).

In general, the porosity of lithium ion electrode materials is desirably low, as high porosity increases the electrolytic mass used and increases the volume used for a given amount of energy storage. Thus, current typical battery practices use batteries with calendered electrode coatings (at very high pressures) that exhibit high coating densities (or conversely low coating porosities). For the electrode coatings discussed above, typical high energy density cells using ultra-thin metallized current collector films include (particularly target) electrodes that exhibit high coating density (low porosity). Thus, for high porosity electrode coatings, the thin electrode coatings described above are counterintuitive according to current practice.

High porosity can be achieved, for example, by using a relatively large particle size material as the electrode coating. Such large particles form relatively large spaces between the particles, thereby increasing the porosity of the solid coating structure. Lower porosity layers can be achieved by using smaller particle sizes, which will achieve smaller inter-particulate spaces. Or a particle size distribution comprising small particles will also achieve a low density.

Such high porosity structures may be measured from tap densities of such electrode materials, from which the porosity is calculated. The true density is the theoretical density of the material, or the volume normalized theoretical density of the mixture. Tap density was obtained by mechanically tapping a graduated cylinder containing the sample until a small additional volume change was observed. The powder porosity is calculated by the following equation 1:

powder porosity = 1-tap density/true density equation 1

The bulk density of the coating was calculated as the coating weight/m ² divided by the volume/m ². Thus, a coating of 20g/m ² and thickness 20 microns was measured/displayed having a bulk density of 1.0g/cm ³. Thus, the porosity of the coating is calculated by the following equation 2:

coating porosity = 1-bulk density/true density equation 2

The application of such high porosity coated electrodes to ultra-thin current collectors (as defined and described for resistivity measurements above) provides the target electrochemical cell with a conventional measure of low internal resistance as the thin electrode coating alternatives described above.

Fig. 5 shows a prior art structure of a low porosity coated electrode 31 applied to an ultra-thin current collector 32. Again, this structure will exhibit high resistivity inside the electrochemical cell (as one non-limiting example, a lithium ion cell).

Fig. 6 thus shows a reduction in the thickness 35 of the electrode coating applied to the ultra-thin current collector 36. As described above, this counterintuitive operation (within the state and criteria of the rechargeable electrochemical cell) compensates for the high resistance exhibited by the ultra-thin current collector by imposing an internal low resistance (as shown in fig. 7) within the target cell.

Fig. 7 thus shows the inclusion of such an ultra-thin aluminized current collector 41 within a battery cell 40. Applied to the current collector 41 is illustrated a high porosity positive electrode coating 44, a first separator 43, and an opposing high porosity negative electrode coating 42. Also present are a second ultrathin copper-plated film current collector 41a and a second separator 43a. Connected to the aluminized current collector 41 is an inner tab 45 for contact with an external contact (not shown) for charge transfer. As described throughout, such a battery 40 exhibits a safety level associated with the presence of ultra-thin current collectors and a high power capacity associated with counterintuitive use and application of thin electrode coatings on such current collector surfaces.

Alternative 3-highly conductive electrode coating

Since most electrode materials have limited conductivity, conductive additives such as carbon black or graphite are important components of lithium ion batteries. However, since the conductive additives do not themselves store lithium and therefore do not contribute to the energy storage capacity of the battery, their use is minimized to make room for the maximum amount of lithium storage material (e.g., NMC positive electrode material). The content of the conductive additive in the coating of the modern lithium ion battery is only 3%, wherein 3-5% of the conductive additive is very common.

In general, the energy density of typical, recent electrochemical cells is maximized in combination with the low porosity electrode coating described above having a low conductive carbon content. As described above, this structure maximizes the active conductive material (e.g., lithium ion structure) in the coating. Achieving such a low porosity, low carbon content electrode coating with an ultra-thin current collector (e.g., a metallized film) will produce the same high resistivity battery results as described above. Although such high internal resistance may also lead to high safety levels (again, as described above), the lack of low resistance within the battery itself would compromise its end use capabilities, thereby greatly limiting the power supply potential. However, the ability to increase carbon content (conductive material level) has not been achieved in the rechargeable chemical battery industry. Thus, according to this alternative, it would be possible to achieve a low level of internal resistance suitable for high volumetric power capability, superficially accommodating for faster conductivity by increasing the carbon content within such electrode materials. This counterintuitive operation and method allows combining a high resistance ultrathin current collector structure with a low resistance electrode material that is made by using more carbon in the coating and has higher porosity.

Alternative 4-layered electrode coating

Another potential structural improvement of such electrochemical cells includes the use of multiple layers of electrodes with different gradients. A common electrode material is made of a single layer of electrode material coated on a current collector. The above-described single thin electrode coating alternatives provide unexpectedly effective results for the target cell with low internal resistance, particularly in combination with high resistivity, safety rating, ultra-thin current collectors (and coatings applied thereon). However, during charging and discharging, the portion of the electrode material that is remote from the current collector will produce more resistive and ohmic heating than the portion of the electrode material that is very close to the current collector. It is therefore advantageous to have the material be remote from the current collector in a configuration that has higher ionic and electronic conductivity than the material near the current collector. Also, such a structure will produce a lower resistance inside the target cell.

Such a structure and physical result may be achieved by a multilayer coating process wherein the first applied coating (closest to the ultrathin current collector surface) has a lower porosity and/or a lower content of conductive particles (carbon or graphite) and the porosity and/or the content of conductive particles increases with subsequent layers (preferably, the porosity and the concentration of conductive particles increase simultaneously with the subsequent layers). The increase in porosity may be achieved by reducing the pressure used during calendering of each successive layer. The content of the conductive particles can be increased by increasing the proportion of the conductive particles in the mixture.

One configuration, as shown in fig. 8, is that the first layer (layer 1) 51B is closest to the substrate (current collector 52), is very thin and has high conductivity, the second layer (layer 2) 51A, which is a low porosity, low carbon content layer, and the third layer (layer 3) 51, which has a higher content of conductive particles and even a high porosity. Further layers may be applied in a similar manner, as described above, each subsequent layer having a higher content of conductive particles and a higher porosity in a stepwise manner. In another configuration, the conductive "primer" layer is eliminated and the lowest porosity, lowest conductive particle content layer is layer 1, with the porosity and/or conductive particle content of each subsequent layer increasing.

Fig. 9 thus shows the application of a multi-layer positive electrode coating 64 (represented by layers 1,2, 3;51, 51A, 51B of fig. 8) applied to an ultra-thin aluminized current collector 61 within a battery cell 60. Further provided is a first separator 63 and an opposing multi-layer negative electrode 64a (of the same construction as the positive electrode 64 but made of a negative electrode material, as is well known to those of ordinary skill). Such a negative electrode is applied to the second ultrathin copper-plated film current collector 61a and the second separator 63a. Connected to the aluminized current collector 61 is an inner tab 65 for contact with an external contact (not shown) for charge transfer. As described throughout, such a battery 60 exhibits a safety level associated with the presence of ultra-thin current collectors and high power capabilities associated with the counterintuitive utilization and application of multi-layer conductive gradient electrode coatings on the surface of such current collectors.

Alternative 5-patterned electrode coating

Another method of achieving low internal resistance by varying the electrode material (unlike methods commonly employed in the industry) involves the use of electrode materials having a specific pattern of conductive structures that contact the surface of the target ultrathin current collector. In this way, the first coating may be applied in discrete areas (whether linear rows, linear columns, diagonal lines, dots, such as cubes, cylinders, or any other geometric three-dimensional shape, etc.), with at least the second coating applied in areas of the target ultra-thin current collector surface where the first coating has not been applied. The various coatings of such electrode materials may include any of the structural limitations and requirements described above, including but not limited to a first coating exhibiting high porosity, a second coating exhibiting high conductivity, and any number of other coatings having different physical results in terms of conductivity, etc., as desired to provide a structure that compensates for the high level of resistivity imparted by the ultra-thin current collector itself, as described above. Thus, with such patterned coatings, different gradients may be created in terms of resistance measurements in these regions, allowing certain regions to drive ions and electrons faster than others.

Thus, in more detail, fig. 10 shows an ultra-thin current collector 73 (again, providing a higher safety level for the target cell, but at the same time also a lower resistivity) to which a first coating 71 provided in three-dimensional lines has been applied and having one type of electrode configuration (e.g. a high energy density made by using a lower content of conductive particles, or a lower porosity obtained by means such as a smaller particle size material), and a second coating 72, the second coating 72 being interspersed in three-dimensional alternating lines to the first coating 71, having an energy density and/or a higher concentration/content of conductive particles than the first coating 72. In this case, the higher porosity and/or higher conductive particle content regions may act as "highways" for ions and electrons, reducing the overall resistance inside the target cell, while maintaining the high energy density of the low porosity, low conductive particle content regions, depending on the particular purpose (if desired).

Fig. 11 thus shows the inclusion of such an ultra-thin aluminized current collector 81 within a battery cell 80. Applied to current collector 81 is shown a patterned coated positive electrode 82, a first separator 83, and an opposing negative electrode coating 82a. The patterned positive electrode coating 82 includes the regions as defined in fig. 10 above (71 and 72). Such a negative electrode is applied to the second ultra-thin copper-plated film current collector 84 and the second separator 83a. Connected to the aluminized current collector 81 is an inner tab 85 for contact with an external contact (not shown) for charge transfer. As described throughout, such a battery 80 exhibits a safety level associated with the presence of ultra-thin current collectors and high power capabilities associated with the counterintuitive utilization and application of patterned electrode coatings on the surfaces of such current collectors.

Thus, the above example has been demonstrated to exhibit the desirable thickness, metal coating and conductivity results required to prevent thermal runaway in electrolyte-containing cells, thereby not only providing a safer and more reliable type, but also requiring less internal weight components than ever without sacrificing safety, but in fact improving performance. However, in addition, the ability of such ultra-thin current collectors to high resistivity levels is compensated for by the application of different types of electrodes described herein that have heretofore not been disclosed or explored in the relevant electrochemical cell industry. The ability to internally transfer such low resistance to the target cell through this unique combination of electrodes and ultra-thin current collectors thereby allows for significant improvements in terms of safety not only due to thermal runaway potentials within rechargeable and similar types of batteries and power cells, but also in terms of ensuring that high power charging and discharging (as needed) of such electrochemical cells for certain end use applications is not compromised.

Having described the invention in detail, it will be apparent to those skilled in the art that variations and modifications can be made to the invention without departing from the scope of the invention. Accordingly, the scope of the invention should be determined only by the following claims.

Accordingly, the foregoing is considered as illustrative only of the principles of the present technology. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the technology to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the technology.

Claims

1. A lithium electrochemical energy generation and storage device comprising a negative electrode, a positive electrode, at least one separator between the negative electrode and the positive electrode, an electrolyte, and at least one current collector in contact with at least one of the negative electrode and the positive electrode, wherein the current collector exhibits a resistivity greater than 0.015 ohm/square, wherein the electrochemical device exhibits a 2C capacity of greater than 70% of the capacity measured at 0.5C, wherein the current collector further comprises an insulating support layer coated with at least one conductive layer, wherein the at least one conductive layer has a thickness of less than 2 microns.

2. The lithium electrochemical energy generation and storage device of claim 1, wherein the device exhibits an electrode area energy density of less than 4mAh/cm ².

3. A lithium electrochemical energy generation and storage device comprising a negative electrode, a positive electrode, at least one separator between the negative electrode and the positive electrode, an electrolyte, and at least one current collector in contact with at least one of the negative electrode and the positive electrode, wherein the current collector exhibits a resistivity greater than 0.005 ohm/square and a thickness of no greater than 2 microns, wherein at least one of the negative electrode or positive electrode is configured to achieve a low resistivity by comprising at least one of:

a. An electrode having a thickness of less than 70 microns;

b. an electrode coating comprising greater than 6 wt% conductive additive;

c. An electrode coating having a porosity greater than 35%;

d. having a multilayer electrode coating, and

E. An electrode coating exhibiting a spreading pattern of a coating material, wherein at least one component of the spreading pattern of the coating material comprises regions of high energy, lower conductivity and at least one other component of the spreading pattern of the coating material comprises regions of higher conductivity, wherein such conductivity is caused by the presence of a high conductive material content or a high porosity material.

4. An energy storage device, comprising:

A negative electrode and a positive electrode;

A first separator interposed between the negative electrode and the positive electrode;

An electrolyte;

A first current collector in contact with at least one of the negative electrode and the positive electrode;

a second current collector in contact with at least one of the negative electrode and the positive electrode, at least one electrode of the second current collector being opposite to at least one electrode of the first current collector, and

A second separator in contact with the negative electrode or the positive electrode;

wherein at least one of the first current collector and the second current collector exhibits a resistivity greater than 0.005 ohm/square.

5. The energy storage device of claim 4, further comprising a tab connected to the first current collector and configured to contact an external contact.

6. The energy storage device of claim 4, wherein the first and second current collectors each comprise a metal film coated thereon.

7. The energy storage device of claim 6, wherein the metal film of the first current collector is a different metal than the metal film of the second current collector.

8. The energy storage device of claim 7, wherein the metal film of at least one of the first and second current collectors has a total coating thickness of less than 5 microns.

9. The energy storage device of claim 4, wherein the negative electrode and the positive electrode are porous, exhibiting a porosity of at least 35%.

10. The energy storage device of claim 4, wherein the negative electrode and the positive electrode each comprise an electrode coating containing greater than 6 wt% conductive additive.

11. The energy storage device of claim 4, wherein the negative electrode and the positive electrode each have a plurality of layers including a top layer having a higher electrical conductivity than each successive lower layer.

12. The energy storage device of claim 4, wherein the negative electrode and the positive electrode each have a plurality of layers including a top layer having a higher porosity than each successive lower layer.

13. The energy storage device of claim 4, wherein the positive electrode is a patterned electrode, a portion of the positive electrode comprising a first region interspersed with a second region, wherein the first region has a first energy or first conductivity property and the second region has a second energy or second conductivity property that is greater than the first region, thereby creating a conductivity gradient.