Systems and methods for monitoring one or more characteristics of an ultracapacitor

Abstract

A method for monitoring one or more characteristics of an ultracapacitor is provided. The method includes obtaining a plurality of voltage measurements. Each of the voltage measurements may be obtained sequentially at one of a plurality of intervals. Further, each of the voltage measurements may indicate a voltage across the ultracapacitor. The method may include determining an actual voltage step of the ultracapacitor based on two consecutive voltage measurements of the plurality of voltage measurements. The method may further include determining whether the actual voltage step exceeds a threshold voltage step for the ultracapacitor. Further, in response to determining that the actual voltage step exceeds the threshold voltage, the method may include providing a notification associated with performing a maintenance action on the ultracapacitor.

Description

Technical Field

[0001] Priority Claim This application claims the benefit of priority of U.S. Provisional Patent Application No. 63 / 033,390, filed on June 2, 2020, entitled "System and Method for Monitoring One or More Characteristics of an Ultracapacitor", which is incorporated herein by reference.

Background Art

[0002] Electrical energy storage cells are widely used to power electronics, electromechanical, electrochemical, and other useful devices. For example, a double-layer ultracapacitor can use a pair of polarized electrodes containing carbon particles (e.g., activated carbon) impregnated with a liquid electrolyte. Due to the effective surface area of the particles and the small spacing between the electrodes, a large capacitance value can be achieved. Individual double-layer capacitors can be combined together to form a module with an increased output voltage or an increased energy capacity. Further, for example, Patent Document 1 discloses a method for balancing an ultracapacitor cell.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Means for Solving the Problems

[0004] One aspect of the present disclosure relates to a method for monitoring one or more characteristics of an ultracapacitor. The method includes obtaining a plurality of voltage measurements via a control circuit. Each voltage measurement of the plurality of voltage measurements can be obtained sequentially at one of a plurality of intervals. Additionally, each of the plurality of voltage measurements can indicate the voltage across the ultracapacitor. The method can include determining, via the control circuit, an actual voltage step of the ultracapacitor based on two consecutive voltage measurements of the plurality of voltage measurements. The method can further include determining, via the control circuit, whether the actual voltage step exceeds a threshold voltage step of the ultracapacitor. Further, in response to determining that the actual voltage step exceeds the threshold voltage step, the method can include providing, via the control circuit, a notification related to performing a maintenance action on the ultracapacitor.

[0005] Another aspect of the present disclosure relates to a system for monitoring one or more characteristics of an ultracapacitor. The system includes one or more switching devices configured to selectively couple the ultracapacitor to a power source or a load. The system further includes a control circuit communicatively coupled to the one or more switching devices. The control circuit is configured to obtain a plurality of voltage measurements. Each of the plurality of voltage measurements can be obtained sequentially at one of a plurality of intervals. Further, each of the plurality of voltage measurements can indicate the voltage across the ultracapacitor. The control circuit is further configured to determine an actual voltage step of the ultracapacitor based on two consecutive voltage measurements of the plurality of voltage measurements. The control circuit is further configured to determine whether the actual voltage step exceeds a threshold voltage step of the ultracapacitor. Further, in response to determining that the actual voltage step exceeds the threshold voltage step, the control circuit is configured to provide a notification related to performing a maintenance action on the ultracapacitor.

[0006] Other features and aspects of the present disclosure are described in further detail below.

[0007] A complete and enabling disclosure of the present disclosure, directed to those of ordinary skill in the art, including its best mode, is set forth in more detail in the remainder of this specification with reference to the accompanying drawings.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Best Mode for Carrying Out the Invention

[0009] The repeated use of reference numerals in this specification and the drawings is intended to represent the same or similar configurations or elements of the present disclosure.

[0010] Those of ordinary skill in the art will understand that this discussion is merely an explanation of exemplary embodiments and is not intended to limit the broader aspects of the present disclosure, which broader aspects are implemented in exemplary configurations.

[0011] Exemplary aspects of the present disclosure relate to systems and related methods for monitoring one or more characteristics of an ultracapacitor, such as capacitance, equivalent series resistance (ESR), etc. The system can include a control circuit configured to monitor a voltage step (e.g., a change in the voltage across the ultracapacitor over time) to determine one or more characteristics of the ultracapacitor. For example, the control circuit can be configured to obtain a plurality of voltage measurements indicative of the voltage across the ultracapacitor. Each of the plurality of voltage measurements can be obtained sequentially at one of a plurality of intervals. For example, in some embodiments, the control circuit can be configured to obtain a voltage measurement approximately every 2 milliseconds. As used herein, the term "about" refers to a range of values within 10% of the recited numerical value.

[0012] The control circuit can be configured to determine an actual voltage step of the ultracapacitor during one of the plurality of intervals based on two consecutive voltage measurements. For example, the control circuit can obtain a first voltage measurement and a second voltage measurement. The first voltage measurement can indicate the voltage across the ultracapacitor at a first point in time. The second voltage measurement can indicate the voltage across the ultracapacitor at a second point in time occurring after the first point in time by an amount of time corresponding to the interval. The control circuit can be configured to determine the actual voltage step of the ultracapacitor based at least in part on the first voltage measurement and the second voltage measurement. For example, the control circuit can be configured to determine the difference between the first voltage measurement and the second voltage measurement to determine the actual voltage step of the ultracapacitor with respect to the time interval (e.g., the amount of time elapsed between the first voltage measurement and the second voltage measurement).

[0013] The control circuit can be configured to determine the threshold voltage step of the ultracapacitor. For example, in some embodiments, the control circuit can be configured to determine the threshold voltage step based at least in part on a time interval and the magnitude of the current supplied to the ultracapacitor during the time interval. Alternatively or additionally, the threshold voltage step of the ultracapacitor can be based at least in part on the maximum voltage across the ultracapacitor due to the current and can be determined. More specifically, the maximum voltage change due to the current can be determined based at least in part on the capacitance of the ultracapacitor and the equivalent series resistance (ESR) of the ultracapacitor. In some embodiments, the threshold voltage step can be about two or three times the maximum voltage change of the ultracapacitor due to the current.

[0014] The control circuit can further be configured to determine whether the actual voltage step of the ultracapacitor exceeds the threshold voltage step of the ultracapacitor. For example, the control circuit can be configured to compare the magnitude of the actual voltage step with the magnitude of the threshold voltage step to determine whether the actual voltage step exceeds the threshold voltage step.

[0015] In response to determining that the actual voltage step of the ultracapacitor exceeds the threshold voltage step of the ultracapacitor, the control circuit can be configured to perform an electronic communication indicating the need to perform a maintenance procedure on the ultracapacitor. For example, in some embodiments, the electronic communication can be a text message or an email. Alternatively or additionally, the electronic communication can be an audible alarm or notification (e.g., an automated phone call). In this way, the notification can prompt a person (e.g., a technician) to repair or replace the ultracapacitor.

[0016] In some embodiments, the control circuit may further be configured to provide one or more control signals related to controlling the operation of one or more switching devices in response to determining that the actual voltage step of the ultracapacitor exceeds the threshold voltage step of the ultracapacitor. More specifically, one or more control signals may be related to controlling the operation of one or more switching devices to disconnect the ultracapacitor from a power source (e.g., a DC power source). In this way, when a person arrives and performs maintenance on the ultracapacitor, the ultracapacitor can be disconnected from the power source. Additionally, in some embodiments, one or more control signals may be related to disconnecting the power source from an electrical load. In this way, when a person arrives and performs maintenance on the ultracapacitor, the ultracapacitor can be disconnected from the electrical load.

[0017] Systems and related methods for monitoring one or more characteristics of an ultracapacitor can provide a number of technical effects and benefits. For example, the control circuit can determine one or more characteristics of the ultracapacitor based at least in part on a plurality of voltage measurements that the control circuit has already received. In this way, one or more characteristics of the ultracapacitor can be determined without the need for additional hardware. Further, the control circuit can determine one or more states of the ultracapacitor without the need to take the ultracapacitor offline (e.g., disconnect it from the power source). In this way, one or more characteristics of the ultracapacitor can be determined even while the ultracapacitor is online (e.g., coupled to the power source).

[0018] Next, referring to the figures, FIG. 1 shows a system 100 for monitoring one or more characteristics of an ultracapacitor 110 according to an exemplary embodiment of the present disclosure. As shown, the ultracapacitor 110 can be coupled between a power source 130 (e.g., direct current) and a load 132. In this way, the power source 130 can charge the ultracapacitor 110. Further, the ultracapacitor 110 can supply (e.g., discharge) current to the load 132.

[0019] As shown, the system 100 can include a control circuit 140. In some embodiments, the control circuit 140 can include a processing circuit (not shown). As used herein, the terms "processor" or "processing circuit" refer not only to integrated circuits that are referred to in the art as being included in a computer, but also to controllers, microcontrollers, microcomputers, programmable logic controllers (PLCs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), and other programmable circuits.

[0020] The control circuit 140 can be configured to acquire a plurality of signals 150 indicating the voltage across the ultracapacitor 110. Further, the control circuit 140 can be configured to determine one or more characteristics (e.g., capacitance, ESR (equivalent series resistance), etc.) of the ultracapacitor 110 based at least in part on the plurality of signals 150. For example, the control circuit 140 can be configured to determine that the capacitance of the ultracapacitor 110 is decreasing based at least in part on the magnitude of the change in the voltage across the ultracapacitor 110 over a time interval between two consecutive voltage measurements. Alternatively, the control circuit 140 can be configured to determine that the ESR of the ultracapacitor 110 is increasing based at least in part on the magnitude of the change in the voltage across the ultracapacitor 110 over a time interval. In either case, the control circuit 140 can be configured to provide an electronic communication to prompt a person (e.g., a technician) to perform a maintenance action on the ultracapacitor 110.

[0021] Next, referring to FIG. 2, another embodiment of the system 100 according to an exemplary embodiment of the present disclosure is provided. As shown, the system 100 can include a first switching device 120 coupled between the ultracapacitor 110 and a power supply 130 (e.g., a direct current (DC) power supply). The first switching device 120 can be configured to be settable in a first state (FIG. 1) in which the ultracapacitor 110 is disconnected from the power supply 130 and a second state (not shown) in which the ultracapacitor 110 is coupled to the power supply 130. When the ultracapacitor 110 is coupled to the power supply 130 via the first switching device 120, the ultracapacitor 110 can draw power from the power supply 130. In this way, when the first switching device 120 is in the second state, the power supply 130 can charge the ultracapacitor 110.

[0022] System 100 can further include a second switching device 122 coupled between the ultracapacitor 110 and the load 132. The second switching device 122 can be set to be changeable in a first state (FIG. 1) where the ultracapacitor 110 is disconnected from the load 132 and a second state (not shown) where the ultracapacitor 110 is coupled to the load 132 via the second switching device 122. When the second switching device 122 is in the second state, the ultracapacitor 110 can supply current to the load 132.

[0023] In some embodiments, the first switching device 120 and the second switching device 122 can include transistors (e.g., field effect transistors). However, it should be recognized that the first switching device 120 and the second switching device 122 can include any suitable device configured to selectively couple the ultracapacitor 110 to the power supply 130. It should also be recognized that the load 132 that draws power from the power supply 130 can include a suitable load.

[0024] The control circuit 140 can be communicatively coupled to the first switching device 120 and the second switching device 122. In this way, the control circuit 140 can communicate with the first switching device 120 and the second switching device 122, respectively , one or more control signals 160, 162 can be provided. More specifically, the one or more control signals 160, 162 can each be related to controlling the operation of the first switching device 120 and the second switching device 122. For example, the control circuit 140 can provide one or more control signals 160 related to coupling the ultracapacitor 110 to the power supply 130 via the first switching device 120 to control the charging of the ultracapacitor. Alternatively, the control circuit can provide one or more control signals 160 related to disconnecting the ultracapacitor 110 from the power supply 130 and / or one or more control signals 162 related to coupling the ultracapacitor 110 to the load 132 to control the discharging of the ultracapacitor.

[0025] Figure 3 shows a graphical representation of the charge-discharge curve 200 of an ultracapacitor according to an exemplary embodiment of the present disclosure. More specifically, the change in voltage of the ultracapacitor over time during two charge-discharge cycles is shown. As illustrated, the measured voltage across the ultracapacitor increases with time during the charge cycle. Conversely, the measured voltage across the ultracapacitor decreases with time during the discharge cycle. Further, each time the ultracapacitor switch toggles between the charge cycle and the discharge cycle, a voltage step 210 occurs, which is at least partially due to the equivalent series resistance (ESR) of the ultracapacitor.

[0026] As illustrated, the charge-discharge curve 200 can include a plurality of voltage measurements 220 indicative of the voltage across the ultracapacitor 110 (FIGS. 1 and 2). The plurality of voltage measurements 220 can be obtained sequentially at one of a plurality of intervals 230. For example, each of the plurality of voltage measurements can be obtained sequentially at a uniform time interval (e.g., every 2 milliseconds).

[0027] However, it should be understood that the plurality of voltage measurement values can be obtained at any suitable time interval. For example, in some embodiments, each of the plurality of voltage measurement values can be obtained sequentially at odd intervals (e.g., every 3 milliseconds). It should be further understood that in some embodiments, the duration of each of the plurality of time intervals can be made the same. For example, each interval can be about 2 milliseconds. As discussed in more detail below, with reference to FIGS. 1 and 2, the control circuit 140 of the system 100 discussed above can obtain a plurality of voltage measurement values 220 and determine whether the voltage step of the ultracapacitor 110 for the interval 230 exceeds the threshold voltage step of the ultracapacitor 110 for the interval 230, thereby determining one or more characteristics of the ultracapacitor 110.

[0028] FIG. 4 shows a flowchart of a method 300 according to an exemplary embodiment of the present disclosure. The method 300 can be implemented, for example, using the system shown in FIGS. 1 and 2. FIG. 4 shows steps executed in a particular order for illustration and discussion. Those skilled in the art will understand that, using the disclosure provided herein, various steps of any of the methods disclosed herein can be omitted, rearranged, executed simultaneously, extended, modified, and / or adapted in various ways without departing from the scope of the present disclosure.

[0029] (302) In, the method 300 can include obtaining a plurality of voltage measurement values via a control circuit. In particular, each of the plurality of voltage measurement values can be obtained sequentially at one of the plurality of time intervals. Further, each of the plurality of voltage measurement values can indicate the voltage across the ultracapacitor at a given instant.

[0030] (304) In, the method 300 is obtained via a control circuit in (302) It can include a step of determining the actual voltage step of the ultracapacitor based at least in part on two consecutive voltage measurement values among a plurality of voltage measurement values. For example, in some embodiments, the control circuit can be configured to determine the actual voltage step based at least in part on a first voltage measurement value indicating the voltage across the ultracapacitor at a first point in time and a second voltage measurement value indicating the voltage across the ultracapacitor at a second instant. More specifically, the control circuit can be configured to determine the difference between the first voltage measurement value and the second voltage measurement value to determine the actual voltage step of the ultracapacitor with respect to a time interval (e.g., the elapsed time between the first voltage measurement and the second voltage measurement).

[0031] (306) In some embodiments, method 300 can include a step of determining the threshold voltage step of the ultracapacitor based at least in part on the capacitance of the ultracapacitor and the current supplied to the ultracapacitor via a control circuit. In some embodiments, the threshold voltage step can be determined by supplying a current to the ultracapacitor. In such embodiments, the threshold voltage step can be determined based at least in part on the capacitance of the ultracapacitor and the magnitude of the current supplied to the ultracapacitor. More specifically, the maximum voltage change of the ultracapacitor while receiving the current can be determined based at least in part on the capacitance of the ultracapacitor and the ESR of the ultracapacitor. In some embodiments, the threshold voltage step can be about two or three times greater than the maximum voltage change of the ultracapacitor while receiving the current.

[0032] In (308), method 300 can include determining whether the actual voltage step of the ultracapacitor determined in (304) exceeds the threshold voltage step of the ultracapacitor determined in (306). For example, the control circuit can be configured to compare the magnitude of the actual voltage step of the ultracapacitor with the magnitude of the threshold voltage step of the ultracapacitor. If the magnitude of the actual voltage step of the ultracapacitor exceeds the magnitude of the threshold voltage step of the ultracapacitor, the control circuit can determine that the capacitance of the ultracapacitor is decreasing or the ESR of the ultracapacitor is increasing. Further, if the actual voltage step of the ultracapacitor exceeds the threshold voltage step of the ultracapacitor, the method proceeds to (310). Otherwise, method 300 returns to (302).

[0033] In (310), method 300 can include providing electronic communication related to performing maintenance on the ultracapacitor via one or more processors in response to determining in (308) that the actual voltage step of the ultracapacitor exceeds the threshold voltage step of the ultracapacitor. In some embodiments, the electronic communication can include a visual notification (e.g., an SMS message, an email, etc.). Alternatively or additionally, the electronic communication can include an audible notification (e.g., an audible alarm, an automated phone call, etc.). In this way, the electronic communication can prompt a person (e.g., an operator) to perform maintenance on the ultracapacitor. For example, the electronic communication can prompt a person to repair the ultracapacitor. Alternatively, the electronic communication can prompt a person to change (i.e., replace) the ultracapacitor with another ultracapacitor.

[0034] At (312), the method 300 can include providing one or more control signals associated with controlling the operation of one or more switching devices to disconnect the ultracapacitor from the power source. In this manner, the ultracapacitor can be disconnected from the power source when personnel arrive to perform maintenance procedures on the ultracapacitor. Additionally, in some implementations, the one or more control signals can be associated with controlling the operation of one or more switching devices to disconnect the ultracapacitor from the power source. The ultracapacitor may be connected to a power supply that controls operation of one or more switching devices to disconnect the ultracapacitor from the electrical load. In this way, when personnel arrive to perform maintenance procedures on the ultracapacitor, the ultracapacitor can be disconnected from the electrical load.

[0035] Any of a variety of different individual ultracapacitors may generally be used in modules according to exemplary aspects of the present disclosure. However, in some embodiments, the ultracapacitor includes an electrode assembly and an electrolyte, optionally hermetically sealed, contained within a housing. The electrode assembly may be electrically coupled to, for example, a first current collector. A first electrode including a first carbonaceous coating (e.g., activated carbon particles), and a second electrode including a second carbonaceous coating (e.g., activated carbon particles) electrically coupled to a second current collector. If desired, particularly when the ultracapacitor includes a number of energy storage cells, it should be understood that additional current collectors may be further used. The current collectors may be formed from the same or different materials. Nevertheless, each current collector is typically formed from a conductive metal, such as aluminum, stainless steel, nickel, silver, palladium, etc., and a substrate including alloys thereof. Aluminum and aluminum alloys are particularly suitable for use in the present disclosure. The substrate may be in the form of a foil, sheet, plate, mesh, etc. The substrate may further have a relatively small thickness, for example, about 200 micrometers or less, in some embodiments from about 1 to about 100 micrometers, in some embodiments from about 5 to about 80 micrometers, and in some embodiments from about 10 to about 50 micrometers. Although not necessarily required, the surface of the substrate may optionally be roughened by washing, etching, blasting, etc.

[0036] In some embodiments, at least one, preferably both, of the first current collector and the second current collector can further include a plurality of fiber-like whiskers protruding outwardly from the substrate. Without being limited by theory, it is believed that these whiskers can effectively increase the surface area of the current collector and further improve the adhesion of the current collector to the corresponding electrode. This can enable the use of a relatively low binder content in the first electrode and / or the second electrode, which can improve charge transfer and reduce interfacial resistance, resulting in a very low ESR value. The whiskers are typically formed from a material containing carbon and / or a reaction product of carbon and a conductive metal. In one embodiment, for example, the material can include a carbide of a conductive metal such as aluminum carbide (Al4C3). Generally, a plurality of whiskers protrude outwardly from the substrate. Optionally, the whiskers can protrude from a seed portion embedded within the substrate, if desired. Similar to the whiskers, the seed portion can also be formed from a material containing carbon and / or a reaction product of carbon and a conductive metal, such as a carbide of a conductive metal (e.g., aluminum carbide).

[0037] The method by which such whiskers are formed on the substrate may vary as desired. In one embodiment, for example, the conductive metal of the substrate is reacted with a hydrocarbon compound. Examples of such hydrocarbon compounds include, for example, paraffinic hydrocarbon compounds such as methane, ethane, propane, n-butane, isobutane, pentane, etc.; olefinic hydrocarbon compounds such as ethylene, propylene, butene, butadiene, etc.; acetylenic hydrocarbon compounds such as acetylene; and derivatives or combinations of any of the foregoing. Generally, the hydrocarbon compound is desirably in gaseous form during the reaction. Thus, it may be desirable to use hydrocarbon compounds such as methane, ethane, and propane that are in gaseous form when heated. Although not necessarily required, the hydrocarbon compound is typically in the range of about 0.1 part by weight to about 50 parts by weight, based on 100 parts by weight of the substrate. , in some embodiments, it is used in the range of about 0.5 part by weight to about 30 parts by weight. Car To initiate the reaction between the hydrocarbon and the conductive metal, the substrate is generally heated in an atmosphere at a temperature of about 300 °C or higher, in some embodiments 400 °C or higher, and in some embodiments in the range of about 500 °C to about 650 °C. The heating time depends on the exact temperature selected but is typically in the range of about 1 hour to about 100 hours. The atmosphere typically contains a relatively small amount of oxygen to minimize the formation of a dielectric film on the surface of the substrate. For example, the oxygen content of the atmosphere can be about 1% by volume or less.

[0038] The first and second carbonaceous coatings are further electrically coupled to the first and second current collectors, respectively. They may be formed from the same or different types of materials and may include one or multiple layers, but each of the carbonaceous coatings typically includes at least one layer containing activated particles. In certain embodiments, for example, an activated carbon layer may be positioned directly on the current collector and, optionally, may be the only layer of the carbonaceous coating. Examples of suitable activated carbon particles can include, for example, coconut shell-based activated carbon, petroleum coke-based activated carbon, pitch-based activated carbon, polyvinylidene chloride-based activated carbon, phenol resin-based activated carbon, polyacrylonitrile-based activated carbon, and activated carbon from natural sources such as coal, charcoal, or other natural organic sources.

[0039] In certain embodiments, it may be desirable to selectively control certain aspects of the activated carbon particles, such as particle size distribution, surface area, and pore size distribution, to assist in improving the ion mobility of a certain type of electrolyte after being subjected to one or more charge-discharge cycles. For example, at least 50 volume% (D50 size) of the particles can have sizes in the range of about 0.01 to about 30 micrometers, in some embodiments about 0.1 to about 20 micrometers, and in some embodiments about 0.5 to about 10 micrometers. Similarly, at least 90 volume% (D90 size) of the particles can have sizes in the range of about 2 to about 40 micrometers, in some embodiments about 5 to about 30 micrometers, and in some embodiments about 6 to about 15 micrometers. The BET surface can range from about 900 m 2 / g to about 3000 m 2 / g, in some embodiments from about 1000 m 2 / g to about 2500 m 2 / g, and in some embodiments from about 1100 m 2 / g to about 1800 m 2 / g.

[0040] In addition to having a specific size and surface area, the activated carbon particles can further include pores having a specific size distribution. For example, the amount of pores with a size of less than about 2 nanometers (i.e., "micropores") can be defined as about 50 volume % or less of the total pore volume, in some embodiments about 30 volume % or less, and in some embodiments a pore volume of from 0.1 volume % to 15 volume %. Similarly, the amount of pores with a size between about 2 nanometers and about 50 nanometers (i.e., "mesopores") can be from about 20 volume % to about 80 volume %, in some embodiments from about 25 volume % to about 75 volume %, and in some embodiments from about 35 volume % to about 65 volume %. Finally, the amount of pores with a size greater than about 50 nanometers (i.e., "macropores") can be from about 1 volume % to about 50 volume %, in some embodiments from about 5 volume % to about 40 volume %, and in some embodiments from about 10 volume % to about 35 volume %. The total pore volume of the carbon particles can range from about 0.2 cm 3 / g to about 1.5 cm 3 / g, and in some embodiments from about 0.4 cm 3 / g to about 1.0 cm 3 / g, and the median pore width can be about 8 nanometers or less, in some embodiments from about 1 to about 5 nanometers, and in some embodiments from about 2 to about 4 nanometers. The pore size and total pore volume can be measured using nitrogen adsorption and analyzed by the Barrett-Joyner-Halenda ("BJH") technique.

[0041] If desired, the binder can be present in the first and / or second carbonaceous coating in an amount of about 60 parts or less per 100 parts of carbon, in some embodiments 40 parts or less, and in some embodiments from about 1 to about 25 parts. The binder can be, for example, a carbonaceous coating It can constitute about 15% by weight or less, in some embodiments about 10% by weight or less, and in some embodiments about 0.5% to about 5% by weight of the total weight of the ring. Any of various suitable binders can be used for the electrode. For example, water-insoluble organic binders such as styrene-butadiene copolymers, polyvinyl acetate homopolymers, vinyl acetate-ethylene copolymers, vinyl acetate-acrylic copolymers, ethylene-vinyl chloride copolymers, ethylene-vinyl chloride-vinyl acetate terpolymers, acrylic polyvinyl chloride polymers, acrylic polymers, nitrile polymers, fluoropolymers such as polytetrafluoroethylene or polyvinylidene fluoride, polyolefins, etc., and mixtures thereof, etc., can be used in certain embodiments. Water-soluble organic binders such as polysaccharides and their derivatives can also be used. In one particular embodiment, the polysaccharide is a non-ionic cellulose ether such as an alkyl cellulose ether (e.g., methyl cellulose and ethyl cellulose); a hydroxyalkyl cellulose ether (e.g., hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl hydroxybutyl cellulose, hydroxyethyl hydroxypropyl cellulose, hydroxyethyl hydroxybutyl cellulose, hydroxyethyl hydroxypropyl hydroxybutyl cellulose, etc.); an alkyl hydroxyalkyl cellulose ether (e.g., methyl hydroxyethyl cellulose, methyl hydroxypropyl cellulose, ethyl hydroxyethyl cellulose, ethyl hydroxypropyl cellulose, methyl ethyl hydroxyethyl cellulose, and methyl ethyl hydroxypropyl cellulose); a carboxyalkyl cellulose ether (e.g., carboxymethyl cellulose); and the like, and protonated salts of any of the foregoing such as sodium carboxymethyl cellulose, etc. can be used.

[0042] Other materials can be further used within the activated carbon layer of the first and / or second carbonaceous coatings and / or within other layers of the first and / or second carbonaceous coatings. For example, in certain embodiments, a conductivity promoter can be used to further increase the conductivity. Exemplary conductivity promoters can include, for example, carbon black, graphite (natural or artificial), graphene, carbon nanotubes, nanowires or nanotubes, metal fibers, graphene, and the like, as well as mixtures thereof. Carbon black is particularly suitable. When used, the conductivity promoter typically constitutes about 60 parts or less per 100 parts of the activated carbon particles in the carbonaceous coating, in some embodiments 40 parts or less, and in some embodiments about 1 to about 25 parts. The conductivity promoter can, for example, constitute about 15 wt% or less of the total weight of the carbonaceous coating, in some embodiments about 10 wt% or less, and in some embodiments about 0.5 wt% to about 5 wt%. The activated carbon particles likewise typically constitute 85 wt% or more of the carbonaceous coating, in some embodiments about 90 wt% or more, and in some embodiments about 95 wt% to about 99.5 wt%.

[0043] Specific techniques for applying the carbonaceous coating to the current collector may vary, such as printing (e.g., rotogravure), spraying, slot-die coating, drop coating, dip coating, etc. Regardless of the application technique, the resulting electrode is typically dried at a temperature of about 100 °C or higher, in some embodiments about 200 °C or higher, and in some embodiments from about 300 °C to about 500 °C to remove moisture from the coating. The electrode may also be compressed (e.g., calendared) to optimize the volumetric efficiency of the ultracapacitor. After any optional compression, the thickness of each carbonaceous coating may typically vary based on the desired electrical performance and operating range of the ultracapacitor. However, typically, the coating thickness is from about 20 to about 200 micrometers, from 30 to about 150 micrometers, and in some embodiments from about 40 to about 100 micrometers. The coating may be present on one or both sides of the current collector. Nevertheless, the thickness of the entire electrode (including the current collector and the carbonaceous coating after any optional compression) is typically from about 20 to about 350 micrometers, in some embodiments from about 30 to about 300 micrometers, and in some embodiments from about 50 to about 250 micrometers.

[0044] The electrode assembly further typically includes a separator positioned between the first electrode and the second electrode. If desired, other separators may further be used in the electrode assembly. For example, one or more separators may be positioned on the first electrode, the second electrode, or both. The separator can help prevent electrical short circuits by electrically insulating one electrode from another, while still allowing ion transport between the two electrodes. In certain embodiments, for example, the separator may be made of a cellulose fiber material (such as an airlaid paper web, a wet-laid paper web, etc.), a nonwoven fiber material (such as a polyolefin nonwoven web), a woven fabric, a film (such as a polyolefin film), etc. Cellulose fiber materials that include natural fibers, synthetic fibers, etc. are particularly suitable for use in ultracapacitors. Specific examples of cellulose fibers suitable for use as separators can include, for example, hardwood pulp fibers, softwood pulp fibers, rayon fibers, regenerated cellulose fibers, etc. Regardless of the specific material used, the separator typically has a thickness of from about 5 to about 150 micrometers, in some embodiments from about 10 to about 100 micrometers, and in some embodiments from about 20 to about 80 micrometers.

[0045] The components of the electrode assembly may be combined together in various ways. For example, the electrodes and separator may first be folded, rolled up, stacked, or otherwise brought into contact together to form the electrode assembly. In one particular embodiment, the electrodes, separator, and optional electrolyte may be rolled up into an electrode assembly having a "jelly roll" configuration.

[0046] To form an ultracapacitor, the electrolyte is placed in ionic contact with the first and second electrodes before, during, and / or after the electrodes and separator are combined to form the electrode assembly. The electrolyte is typically essentially non-aqueous and thus contains at least one non-aqueous solvent. To help extend the operating temperature range of the ultracapacitor, typically the non-aqueous solvent has a relatively high boiling temperature, for example about 150 °C or higher, in some embodiments about 200 °C or higher, and in some embodiments about 220 °C to about 300 °C, etc. Particularly suitable high-boiling solvents can include, for example, cyclic carbonate solvents such as ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, etc. Of course, other non-aqueous solvents may also be used alone or in combination with cyclic carbonate solvents. Examples of such solvents can include, for example, open-chain carbonates (e.g., dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, etc.), aliphatic monocarboxylates (e.g., methyl acetate, methyl propionate, etc.), lactone solvents (e.g., butyrolactone, valerolactone, etc.), nitriles (e.g., acetonitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, 3-methoxypropionitrile, etc.), amides (e.g., N,N-dimethylformamide, N,N-diethylacetamide, N-methylpyrrolidinone), alkanes (e.g., nitromethane, nitroethane, etc.), sulfur compounds (e.g., sulfolane, dimethyl sulfoxide, etc.); and the like.

[0047] The electrolyte may further include at least one ionic liquid dissolved in the non-aqueous solvent. The concentration of the ionic liquid can vary, but typically it is desirable for the ionic liquid to be present at a relatively high concentration. For example, the ionic liquid may be present in an amount of about 0.8 moles per liter (M) or more of the electrolyte, in some embodiments about 1.0 M or more, in some embodiments about 1.2 M or more, and in some embodiments about 1.3 to about 1.8 M.

[0048] Ionic liquids are usually salts having a relatively low melting temperature, for example, about 400 °C or lower, in some embodiments about 350 °C or lower, in some embodiments about 1 °C to about 100 °C, in some embodiments about 5 °C to about 50 °C, and the like. The salt contains a cationic species and a counter ion. The cationic species includes compounds having at least one heteroatom (e.g., nitrogen or phosphorus) as a "cation center". Examples of such heteroatom compounds include, for example, unsubstituted or substituted organic quaternary ammonium compounds, such as ammonium (e.g., trimethylammonium, tetraethylammonium, etc.), pyridinium, pyridazinium, pyrazinium, imidazolium, pyrazolium, oxazolium, triazolium, thiazolium, quinolinium, piperidinium, pyrrolidinium, quaternary ammonium spiro compounds in which two or more rings are connected together by a spiro atom (e.g., carbon, heteroatom, etc.), quaternary ammonium condensed ring structures (e.g., quinolinium, isoquinolinium, etc.), and the like. In one particular embodiment, for example, the cationic species may be an N-spiro bicyclic compound, such as a symmetric or asymmetric N-spiro bicyclic compound having a cyclic ring. An example of such a compound is the following structure of

[0049] [Chemical formula] having, where m and n are independently numbers from 3 to 7, and in some embodiments 4 to 5 (e.g., pyrrolidinium or piperidinium).

[0050] Similarly, suitable counterions for the cationic species include halogens (e.g., chloride, bromide, iodide, etc.); sulfates or sulfonates (e.g., methyl sulfate, ethyl sulfate, butyl sulfate, hexyl sulfate, octyl sulfate, hydrogen sulfate, methane sulfonate, dodecylbenzene sulfonate, dodecyl sulfate, trifluoromethane sulfonate, heptadecafluorooctane sulfonate, sodium dodecylethoxysulfate, etc.); sulfosuccinates; amides (e.g., dicyanamide); imides (e.g., bis(pentafluoroethyl - sulfonyl)imide, bis(trifluoromethylsulfonyl)imide, bis(trifluoromethyl)imide, etc.); borates (e.g., tetrafluoroborate, tetracyano - borate, bis[oxalato]borate, bis[salicylato]borate, etc.); phosphates or phosphinates (e.g., hexafluorophosphate, diethyl phosphate, bis(pentafluoroethyl)phosphinate, tris(pentafluoroethyl)-trifluorophosphate, tris(nonafluorobutyl)trifluorophosphate, etc.); antimonates (e.g., hexafluoroantimonate); aluminates (e.g., tetrachloroaluminate); fatty acid carboxylates (e.g., oleate, isostearate, pentadecafluorooctanoate, etc.); cyanates; acetates; and the like, as well as combinations of any of the foregoing.

[0051] Some examples of suitable ionic liquids can include, for example, spiro-(1,1’)-bipyrrolidinium tetrafluoroborate, triethylmethylammonium tetrafluoroborate, tetraethylammonium tetrafluoroborate, spiro-(1,1’)-bipyrrolidinium iodide, triethylmethylammonium iodide, tetraethylammonium iodide, methyltriethylammonium tetrafluoroborate, tetrabutylammonium tetrafluoroborate, tetraethylammonium hexafluorophosphate, etc.

[0052] As described above, the ultracapacitor further includes a housing in which the electrode assembly and the electrolyte are held and optionally hermetically sealed. The nature of the housing may vary as desired. In one embodiment, for example, the housing can include a metal container (a "can") formed from tantalum, niobium, aluminum, nickel, hafnium, titanium, copper, silver, steel (e.g., stainless), their alloys, their composites (e.g., a metal coated with a conductive oxide), and the like. Aluminum is particularly suitable for use in the present disclosure. The metal container may have any of a variety of different shapes, such as cylindrical, D-shaped, etc. A cylindrical container is particularly suitable.

[0053] In another embodiment, for example, the housing can be in the form of a flexible package that seals the components of the ultracapacitor. The package generally includes a substrate that extends between two ends and has edges where the ends and the overlapping side portions are fixedly and hermetically abutted against each other (e.g., by heat welding). In this way, the electrolyte can be held within the package. The substrate typically has a thickness in the range of from about 20 micrometers to about 1000 micrometers, in some embodiments from about 50 micrometers to about 800 micrometers, and in some embodiments from about 100 micrometers to about 600 micrometers.

[0054] The substrate can include any number of layers desired to achieve the desired level of barrier properties, e.g., one or more, in some embodiments two or more, and in some embodiments, two to four layers. Typically, the substrate includes a barrier layer that can include a metal such as aluminum, nickel, tantalum, titanium, stainless steel, etc. Such a barrier layer is generally impermeable to the electrolyte so as to prevent leakage of the electrolyte, and further is generally impermeable to water and other contaminants. Optionally, the substrate can further include an outer layer that functions as a protective layer of the package. In this way, the barrier layer is positioned between the outer layer and the electrode assembly. The outer layer can be formed from a polymer film such as, for example, those formed from polyolefins (e.g., ethylene copolymers, propylene copolymers, propylene homopolymers, etc.), polyesters, etc. Particularly suitable polyester films can include, for example, polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, etc.

[0055] If desired, the substrate can further include an inner layer positioned between the electrode assembly and the barrier layer. In certain embodiments, the inner layer can include a heat-sealable polymer. Suitable heat-sealable polymers can include, for example, vinyl chloride polymers, vinyl chloridine polymers, ionomers, and combinations thereof. Ionomers are particularly suitable. In one embodiment, for example, the ionomer can be a copolymer comprising α-olefin and (meth)acrylic acid repeat units. Specific α-olefins can include ethylene, propylene, 1-butene; 3-methyl-1-butene; 3,3-dimethyl-1-butene; 1-pentene; 1-pentene having one or more methyl, ethyl, or propyl substituents; 1-hexene having one or more methyl, ethyl, or propyl substituents; 1-heptene having one or more methyl, ethyl, or propyl substituents; 1-octene having one or more methyl, ethyl, or propyl substituents; 1-nonene having one or more methyl, ethyl, or propyl substituents; ethyl, methyl, or dimethyl-substituted 1-decene; 1-dodecene; and styrene. Ethylene is particularly suitable. As described above, the copolymer can also have (meth)acrylic acid repeat units. As used herein, the term "(meth)acrylic" includes acrylic monomers and methacrylic monomers, as well as salts or esters thereof, such as acrylate monomers and methacrylate monomers. Examples of such (meth)acrylic monomers are methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acry Rate, n-butyl acrylate, s-butyl acrylate, i-butyl acrylate, t-butyl acrylate, n-amyl acrylate, i-amyl acrylate, isobornyl acrylate, n-hexyl acrylate, 2-ethylbutyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, n-decyl acrylate, methylcyclohexyl acrylate, cyclopentyl acrylate, cyclohexyl acrylate, methyl methacrylate, ethyl methacrylate, 2-hydroxyethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, i-propyl methacrylate, i-butyl methacrylate, n-amyl methacrylate, n-hexyl methacrylate, amyl methacrylate, s-butyl methacrylate, t-butyl methacrylate, 2-ethylbutyl methacrylate, methylcyclohexyl methacrylate, cinnamyl methacrylate, crotyl methacrylate, cyclohexyl methacrylate, cyclopentyl methacrylate, 2-ethoxyethyl methacrylate, isobornyl methacrylate, etc., and combinations thereof can be included. Typically, the α-olefin / (meth)acrylic acid copolymer is at least partially neutralized with metal ions to form an ionomer. Suitable metal ions can include, for example, alkali metals (such as lithium, sodium, potassium, etc.), alkaline earth metals (such as calcium, magnesium, etc.), transition metals (such as manganese, zinc, etc.), and combinations thereof. The metal ions can be provided by ionic compounds such as metal formates, acetates, nitrates, carbonates, bicarbonates, oxides, hydroxides, alkoxides, etc.

[0056] Within the module, the ultra-capacitor may be connected in various ways. For example, the ultra-capacitor may be connected using interconnections that are attached or connected to respective terminals of the ultra-capacitor. The interconnections may be fabricated from a conductive material such as a conductive metal. In one embodiment, the interconnections may be relatively flat or may be those with an increased surface area. In the latter case, the interconnections may have protrusions / projections or may further be formed from wires, braids, coils, etc. In this regard, the specific dimensions and configurations of the interconnections are not necessarily limited. Regardless of its form, any of a variety of different conductive materials such as copper, tin, nickel, aluminum, etc., as well as alloys and / or coated metals, may be used. If desired, the conductive material may optionally be insulated using a sheath material.

[0057] The ultra-capacitors may be electrically connected together in series or in parallel depending on the particular desired properties. For example, in one particular embodiment, the ultra-capacitors may be electrically connected in series such that the terminal of a particular polarity (e.g., positive) of one ultra-capacitor is connected to the terminal of the opposite polarity (e.g., negative) of another ultra-capacitor. For example, the positive terminal may extend from the top of the first ultra-capacitor and the negative terminal may extend from the bottom of the second ultra-capacitor.

[0058] Ultracapacitors and modules including them can be used to store large amounts of charge. As a result, the modules and ultracapacitors of the present disclosure can be used in a variety of applications. For example, they can be used in a variety of energy applications including, but not limited to, wind turbines, solar turbines, solar panels, and fuel cells. In addition, they can be used in a variety of transportation applications including, but not limited to, vehicles (e.g., battery-propelled electric vehicles, buses, engine starting, hybrid electric vehicles including power and brake recovery systems, etc.), trains and trams (e.g., linear motor cars, line switching, starter systems, etc.), and aerospace (e.g., door actuators, escape shoots, etc.). They also have a variety of industrial applications including automation (e.g., robotics, etc.), vehicles (e.g., forklifts, cranes, electric carts, etc.). They also have a variety of applications in household appliances (e.g., portable media players, handheld devices, GPS, digital cameras, etc.), computers (e.g., laptop computers, PDAs, etc.), and communication systems. The modules and ultracapacitors can also have a variety of military applications (e.g., motor starting for tanks and submarines, phased array radar antennas, laser power supplies, wireless communication, avionics displays and instrumentation, GPS guidance, etc.), and medical applications (e.g., defibrillators, etc.).

[0059] These and other changes and modifications of the present invention may be practiced by those skilled in the art without departing from the spirit and scope of the present invention. In addition, it should be understood that aspects of the various embodiments may be exchanged, both in whole or in part. Furthermore, those skilled in the art will recognize that the foregoing description is merely illustrative and is not intended to limit the present invention as further described in the appended claims.

Claims

1. A method for monitoring one or more characteristics of an ultracapacitor, the method comprising: obtaining a plurality of voltage measurements via a control circuit, each of the plurality of voltage measurements being obtained sequentially at one of a plurality of intervals, each of the plurality of voltage measurements indicating a voltage across the ultracapacitor; determining, via the control circuit, an actual voltage step of the ultracapacitor that occurs when the ultracapacitor switches between a charging cycle and a discharging cycle based on two consecutive voltage measurements of the plurality of voltage measurements; determining, via the control circuit, whether the actual voltage step exceeds a threshold voltage step of the ultracapacitor when switching between the charging cycle and the discharging cycle; providing, via the control circuit, a notification related to performing a maintenance procedure on the ultracapacitor in response to determining that the actual voltage step exceeds the threshold voltage step. A method comprising the above steps.

2. determining, via the control circuit, the threshold voltage step of the ultracapacitor based at least in part on the capacitance of the ultracapacitor and the magnitude of the current supplied to the ultracapacitor. The method according to claim 1, further comprising the above step.

3. The method according to claim 2, wherein the step of determining the threshold voltage step of the ultracapacitor comprises determining, via the control circuit, a maximum voltage change across the ultracapacitor due to the current.

4. The method according to claim 3, wherein the threshold voltage step is approximately twice as large as the maximum voltage change across the ultracapacitor.

5. The method according to claim 1, wherein each of the plurality of intervals has the same duration.

6. The method according to claim 1, wherein when the actual voltage step of the ultracapacitor exceeds the threshold voltage step of the ultracapacitor, the capacitance of the ultracapacitor is decreasing.

7. The method according to claim 1, wherein when the actual voltage step of the ultracapacitor exceeds the threshold voltage step of the ultracapacitor, the equivalent series resistance (ESR) of the ultracapacitor is increasing.

8. The method according to claim 1, wherein the step of determining whether the actual voltage step exceeds the threshold voltage step includes, via the control circuit, determining whether the magnitude of the actual voltage step exceeds the magnitude of the threshold voltage step.

9. The method according to claim 1, wherein the notification includes electronic communication.

10. The method according to claim 1, wherein the maintenance measure includes replacing the ultracapacitor.

11. In response to determining that the actual voltage step of the ultracapacitor exceeds the threshold voltage step of the ultracapacitor, providing, via the control circuit, one or more control signals related to controlling the operation of one or more switching devices to disconnect the ultracapacitor from the power supply The method according to claim 1, further comprising.

12. A system for monitoring one or more characteristics of an ultracapacitor, the system comprising: one or more switching devices configured to selectively couple the ultracapacitor to a power supply or a load; a control circuit communicatively coupled to the one or more switching devices, the control circuit being configured to: acquire a plurality of voltage measurements, each of the plurality of voltage measurements being acquired sequentially at one of a plurality of intervals, each of the plurality of voltage measurements indicating the voltage across the ultracapacitor; determine an actual voltage step of the ultracapacitor that occurs when the ultracapacitor switches between a charging cycle and a discharging cycle based on two consecutive voltage measurements of the plurality of voltage measurements; determine whether the actual voltage step exceeds a threshold voltage step of the ultracapacitor when switching between the charging cycle and the discharging cycle; and provide a notification related to performing a maintenance measure on the ultracapacitor in response to determining that the actual voltage step exceeds the threshold voltage step. A system comprising.

13. The control circuit further comprises Determine the threshold voltage step based at least in part on the capacitance of the ultracapacitor and the current supplied to the ultracapacitor The system according to claim 12, configured to be like this

14. The system according to claim 12, wherein the duration of each of the plurality of intervals is the same

15. The system according to claim 12, wherein when the actual voltage step of the ultracapacitor exceeds the threshold voltage step of the ultracapacitor, the capacitance of the ultracapacitor is decreasing

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