Chip-type ultracapacitor

Abstract

To provide an energy storage device suitable for mounting on a printed circuit board using a solder reflow process.SOLUTION: An electric double layer capacitor (chip cap 100) includes a hermetically sealed housing body 101 with positive and negative internal contacts (metal contact pads) and a lid 102. A capacitor including a chip cap storage cell 105 immersed in or wetted by an electrolyte 126 is disposed within the body 101 and the lid 102.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of previously filed provisional application No. 62 / 567,752, entitled “Chip Ultracapacitor,” filed under 37 CFR § 1.53(b), and also filed under 35 U.S.C. § 1.119(e), which is hereby incorporated by reference in its entirety for all purposes.

[0002] The invention disclosed herein relates to energy storage devices, and more particularly to ultracapacitors adapted for mounting on electrical circuit boards. [Background technology]

[0003] A myriad of devices utilize electronic devices that have components located on circuit boards. As with all electronic devices, an effective power source is a necessary requirement to power those components. One technique for providing local power on a circuit board involves the use of energy storage devices such as batteries or capacitors.

[0004] Typically, conventional capacitors deliver a specific energy of less than about 360 joules per kg, while conventional alkaline batteries have a density of about 590 kJ / kg. Ultracapacitors (also called supercapacitors) can be charged and discharged much faster and can withstand many more charge-discharge cycles than rechargeable batteries. This makes implementing ultracapacitors an attractive solution for electrical engineers.

[0005] The first design obstacle is that a typical ultracapacitor can be significantly larger than a conventional battery for a given charge. Even with increased power density, another problem is the process oriented: assembly of the electrical circuit requires soldering components to a circuit board. This "reflow process" generates heat large enough to degrade or destroy conventional ultracapacitors. Thus, while the use of ultracapacitors may be an attractive solution for powering electronic devices mounted on a circuit board, this solution is not available for compact designs that require high power output. Yet another problem with existing ultracapacitor technology is the limited lifespan of such components. Summary of the Invention [Problem to be solved by the invention]

[0006] What is needed is an ultracapacitor that is useful for powering electrical components located on a circuit board, preferably one that provides a compact design suitable for the ever-shrinking sizes of components, can withstand reflow processes, and provides a useful operating life. [Means for solving the problem]

[0007] In one embodiment, an energy storage device suitable for mounting on a printed circuit board using a solder reflow process is disclosed. In some embodiments, the device includes a hermetically sealed housing body (e.g., a lower body with a lid attached) having positive and negative internal contacts (e.g., metal contact pads) disposed within the body and in electrical communication with positive and negative external contacts, respectively. Each of the external contacts provides electrical communication to the exterior of the body and may be disposed on an exterior surface of the body. An electric double layer capacitor (EDLC) (also referred to herein as ultracapacitor or supercapacitor) energy storage cell is disposed within a cavity within the body that includes a stack of alternating electrode layers and electrically insulating separator layers. An electrolyte is disposed within the cavity and wets the electrode layers. A positive lead electrically connects a first group of one or more electrode layers to the positive internal contacts, and a negative lead electrically connects a second group of one or more electrode layers to the negative internal contacts.

[0008] In some embodiments, each of the electrode layers includes an energy storage medium that is primarily a carbonaceous material and is substantially free of binder. In some embodiments, the energy storage medium includes a network of carbon nanotubes that define voids, and a carbonaceous material (e.g., activated carbon) disposed in the voids and bound by the network of carbon nanotubes. In some embodiments, at least one electrode layer includes a double-sided electrode layer having an energy storage medium disposed on opposing sides of a conductive current collector layer.

[0009] In some embodiments, a surface of the energy storage cell that is in physical contact with the body is made of an electrically insulating material (e.g., a layer separator material, or in some embodiments, an insulating envelope barrier disposed around the cell).

[0010] In some embodiments, each of the electrode layers includes a conductive tab attached to one of the positive and negative leads. For example, the positive electrode group may include a tab connected to the positive lead (and similarly for the negative electrodes) using, for example, ultrasonic welding or other suitable techniques.

[0011] In various embodiments, it is desirable to prevent corrosion and other related deleterious effects by insulating electrochemically active portions of the device that may come into contact with the electrolyte during operation. Accordingly, some embodiments include one or more anti-corrosion features, e.g., a feature disposed near one of the internal contacts and configured to limit electrochemical reaction between the internal contact and the electrolyte during operation. In some embodiments, the internal contact includes a first material having a relatively high electrochemical activity with the electrolyte, and the anti-corrosion feature includes a protective layer of a second material having a relatively lower electrochemical activity with the electrolyte than the first material, the protective layer disposed to prevent contact between the first material and the electrolyte. In some embodiments, the protective layer includes, for example, a layer of a sealant of the type described herein. In some embodiments, the protective layer includes a metal layer disposed on a surface of the first material. In some embodiments, the protective layer includes a metal layer disposed on a surface of the first material and a sealant layer disposed on the metal layer. In some embodiments, the metal layer includes a metal shim secured or partially secured (e.g., to the internal contact) by the sealant layer. In some embodiments, the inner surface of the body includes a recess configured to receive at least a portion of the corrosion protection feature. In some embodiments, a portion of the positive or negative lead extends through the corrosion protection feature to connect to one of the internal contacts. In some embodiments, the corrosion protection feature includes an aluminum metal layer. In some embodiments, the corrosion protection feature includes an epoxy sealant.

[0012] Some embodiments include an electrically insulating envelope barrier surrounding the energy storage cell and electrolyte configured to prevent contact between the electrolyte and the energy storage cell and surfaces of the cavity. In some embodiments, the leads extend through the barrier from the energy storage cell to the internal contacts. In some embodiments, the barrier is heat sealed to the die leads to prevent leakage of the electrolyte from within the barrier envelope.

[0013] In some embodiments, the body is a chip configured for surface mounting on a printed circuit board (e.g., a ceramic-based microchip package), where when so mounted, the chip extends above a major surface of the printed circuit board by about 5.0 mm, 4.0 mm, 3.5 mm, 3.0 mm, or less.

[0014] In some embodiments, the device may have an operating voltage of at least 2.0V, 2.1V, 2.2V 2.3V, 2.4V, 2.5V, 3.0V, or more. In some embodiments, the device may have a capacitance of at least 300mF, 400mF, 450mF, 500mF, or more. In some embodiments, the device may have an energy density of at least 4.0J / cc, 4.5J / cc, 5.0J / cc, 5.1J / cc, or more. In some embodiments, the device may have a peak density of at least 15W / cc, at least 20W / cc, at least 22W / cc, or more. In some embodiments, the device may have an equivalent series resistance of 500mΩ or less, an equivalent series resistance of 400mΩ or less, or an equivalent series resistance of 300mΩ or less. In some embodiments, the device may have an operating temperature rating of at least 65° C., 75° C., 85° C., 100° C., 125° C., 150° C., or more.

[0015] In some embodiments, the device may have an operational lifetime of at least 2,000 hours at an operating voltage of at least 2.0 V (or at least 2.1 V or greater) and an operating temperature of at least 65° C., while exhibiting less than 30% capacitance degradation and less than 100% equivalent series resistance increase. In some embodiments, the device may have an operational lifetime of at least 1,000 hours, at least 1,500 hours, at least 2,000 hours, at least 3,000 hours, or more at an operating voltage of at least 2.0 V (or at least 2.1 V or greater) and an operating temperature of 85° C., while exhibiting at least 30% capacitance degradation and less than 100% equivalent series resistance increase. In some embodiments, the device may have an operational life of at least 1,000 hours, at least 1,500 hours, at least 2,000 hours, at least 3,000 hours, or more, at an operating voltage of at least 2.0 V (or at least 2.1 V or more) and an operating temperature of 100° C., while exhibiting a capacitance degradation of at least 30% and an equivalent series resistance increase of less than 100%. In some embodiments, the aforementioned operational life occurs after the device is soldered to a printed circuit board using a reflow process having at least 1, 2, 3, 4, 5, 6, or more temperature cycles of at least 30 seconds, 60 seconds, 120 seconds, 180 seconds, 240 seconds, 360 seconds, or more, at a peak temperature of at least 100° C., 200° C., 250° C., 300° C., or more.

[0016] In some embodiments, the energy storage cell provides power (back-up power) to at least one additional component (eg, a solid-state memory device) mounted on the circuit board.

[0017] In some embodiments, the electrolyte includes an ionic liquid, which may be mixed with a salt and / or a solvent, for example, of the type described herein.

[0018] In some embodiments, the housing body is hermetically sealed. For example, in some embodiments, a metal lid may be attached (e.g., fused) to a ceramic element to form the housing body, as described in detail herein.

[0019] In some embodiments, the total concentration of halide ions within the cavity of the housing body containing the energy storage cells is maintained at about 1,000 ppm, 500 ppm, 200 ppm, 100 ppm or less. In some embodiments, the total concentration of metal species impurities within the cavity of the housing body containing the energy storage cells is maintained at about 1,000 ppm, 500 ppm, 200 ppm, 100 ppm or less. In some embodiments, the total concentration of bromoethane, ethyl chloride, 1-bromobutane, 1-chlorobutane, 1-methylimidazole, ethyl acetate, and methylene chloride impurities within the cavity of the housing body containing the energy storage cells is maintained at about 1,000 ppm, 500 ppm, 200 ppm, 100 ppm or less. In some embodiments, moisture is maintained at about 1,000 ppm, 500 ppm, 200 ppm, 100 ppm, 50 ppm, 10 ppm or less within the cavity of the housing body containing the energy storage cell. In some embodiments, halide impurities are maintained at about 1,000 ppm, 500 ppm, 200 ppm, 100 ppm, 50 ppm, 10 ppm or less within the cavity of the housing body containing the energy storage cell.

[0020] In some embodiments, the device includes a single energy storage cell contained in a hermetically sealed housing body, i.e., one energy storage cell per chip, while in other embodiments, each chip may include multiple energy storage cells arranged, for example, together in a common cavity, or in separate cavities, or a combination thereof.

[0021] In another aspect, a method of making an energy storage device suitable for mounting on a printed circuit board using a solder reflow process is disclosed. In some embodiments, the method includes forming an electric double layer capacitor (EDLC) energy storage cell including a stack of alternating electrode layers and electrically insulating separator layers, disposing the energy storage cell in a housing body having a positive electrode internal contact and a negative electrode internal contact disposed therein, at least partially filling the body with an electrolyte to wet the electrode layers, electrically connecting a positive electrode lead from a first group of one or more electrode layers to the positive electrode internal contact, electrically connecting a negative electrode lead from a second group of one or more electrode layers to the negative electrode internal contact, and sealing the housing body with the energy storage cell disposed within the cavity. In some embodiments, sealing the housing body includes hermetically sealing the housing body (e.g., providing a low impurity condition as described herein).

[0022] In another aspect, a method of providing energy to a device mounted on a printed circuit board is disclosed. In some embodiments, the method may include mounting a device of the type described herein to a printed circuit board using a solder reflow process, and repeatedly charging and discharging the device at an operating voltage and temperature to provide energy to the device. In some embodiments, the operating voltage is at least 2.0V, 2.1V, 2.2V, 2.3V, 2.4V, 2.5V, 2.75V, 3.0V, or more. In some embodiments, the operating temperature is at least 65°C, at least 85°C, at least 100°C, at least 125°C, at least 150°C, or more. In some embodiments, the method includes repeatedly charging and discharging the device at an operating voltage and temperature to provide energy to the device for at least 2,000 hours, during which the device exhibits less than 30% capacitance degradation and less than 100% equivalent series resistance increase.

[0023] Various embodiments may include any of the above features and elements described herein, either alone or in any suitable combination.

[0024] The features and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings. [Brief description of the drawings]

[0025] [Figure 1] FIG. 1 is a schematic diagram depicting an exemplary embodiment of an ultracapacitor. [Diagram 2] FIG. 2 is an isometric view of an embodiment of a tip cap in accordance with the teachings herein. [Diagram 3] FIG. 3 is an exploded view of the tip cap of FIG. 2 (from an opposite angle). [Figure 4] 4A, 4B and 4C, collectively referred to herein as FIG. 4, are illustrations of electrodes for the tip cap of FIG. [Diagram 5] FIG. 5 is a depiction of a stack of energy storage media for use in a storage cell for the tip cap of FIG. [Figure 6] FIG. 6 is an isometric view of a storage cell for the tip cap of FIG. [Figure 7] FIG. 7 is an isometric view of a body for the tip cap of FIG. [Figure 8] FIG. 8 is a bottom view of the main body of FIG. [Figure 9] FIG. 9 is an isometric view of the storage cell of FIG. 6 disposed within the body of FIG. [Figure 10] FIG. 10 is a partial schematic cross-sectional view of the body of FIG. 7 in preparation for the incorporation of a storage cell. [Figure 11] FIG. 11 is a top down view of the assembly of FIG. [Figure 12] FIG. 12 is a cross-sectional view of the assembly shown in FIG. 11, the cross-section being taken along the axis labeled "A." [Figure 13] FIG. 13 is a graph depicting a time-temperature profile for reflow of the chip cap of FIG. [Figure 14]14-16 are graphs depicting aspects of performance data for example tip caps. [Figure 15] Same as above. [Figure 16] Same as above. [Figure 17] 17A-17B are graphs depicting aspects of performance data for example tip caps. [Figure 18] 18A-18B are graphs depicting aspects of performance data for example tip caps. [Figure 19] FIG. 19 is a schematic diagram illustrating a system for utilizing the tip cap of FIG. [Figure 20] FIG. 20 is a schematic diagram illustrating a process flow for making the tip cap of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Disclosed herein is an energy storage device useful for providing energy to a circuit board. The energy storage device, commonly referred to as a "chip cap," is a specialized ultracapacitor configured in a form factor suitable for surface mounting to a circuit board. Advantageously, the chip cap can withstand the demands associated with manufacturing and assembly of circuitry on a board, and subsequently provide superior performance over existing energy storage devices.

[0027] Before introducing energy storage devices, some terminology is provided to provide background for the teachings herein.

[0028] An embodiment of an energy storage device is referred to herein as an "ultracapacitor" or even as a "chip cap." The term "chip cap" generally refers to an embodiment of an ultracapacitor that is suitable for surface mounting on a printed circuit board (PCB). In general, the term "chip cap" refers to conventional microchip-type components that can be mounted on a circuit board (i.e., a chip) and the ultracapacitor technology contained therein.

[0029] As used herein, the term "reflowable" generally refers to the ability of the energy storage devices disclosed herein to withstand manufacturing processes associated with surface mounting to a circuit board. The manufacturing processes may include soldering (i.e., reflow processing) involving heating cycles that heat the components to process temperatures of 150 degrees Celsius or higher, and in some cases up to 200 degrees Celsius, and perhaps even up to 220 degrees Celsius. Such heating cycles may last for periods of 30, 60, 90, 120, 240, 360 seconds, and more. Thus, as discussed herein, a "reflowable" component is one that can withstand heating cycles appropriate for incorporation of the component into a board-mounted circuit without experiencing substantial future performance degradation. In some embodiments, the components described herein may withstand multiple such reflow cycles, e.g., 2, 3, 4, 5 or more such cycles.

[0030] In some embodiments, the reflowable components may actually exhibit degraded performance, however, the degradation may be expected and the final installation (i.e., the assembled or mounted components) may exhibit a predicted performance level that is deemed acceptable.

[0031] Before introducing the chip cap, some general aspects of an electrochemical double layer capacitor (EDLC) are described below in conjunction with Figure 1. The examples presented herein are not intended to be limiting of the technology, but are merely illustrative and provided for illustrative purposes.

[0032] FIG. 1 illustrates concepts associated with an exemplary embodiment of an electrochemical double layer capacitor (EDLC) 10, also referred to as an "ultracapacitor." The ultracapacitor 10 includes two electrodes, a negative electrode 3 and a positive electrode 4, with each electrode 3, 4 having a double layer of charge at the electrolyte interface. In some embodiments, multiple electrodes are included. However, for purposes of discussion and illustration, only two electrodes 3, 4 are shown in FIG. 1. As a convention herein, each of the electrodes 3, 4 uses a carbon-based energy storage medium (as discussed further herein) to provide energy storage.

[0033] Each of the electrodes 3, 4 includes a respective current collector 2. In the ultracapacitor 10, the electrodes 3, 4 are separated by a separator 5. Typically, the separator 5 is a thin structural material (usually a sheet) used to separate the electrodes 3, 4 into two or more compartments.

[0034] At least one form of electrolyte 6 is included. The electrolyte 6 fills the spaces within and between the electrodes 3, 4 and separator 5. Typically, the electrolyte 6 is a chemical compound that dissociates into electrically charged ions. A solvent in which the chemical compound dissolves may be included in some embodiments. The resulting electrolyte conducts electricity by transport of ions.

[0035] For convenience, the combination of electrodes 3, 4, separator 5, and electrolyte 6 is referred to as a "rechargeable cell 12." In some embodiments, the term "rechargeable cell" simply refers to the electrodes 3, 4 and separator 5 without the electrolyte 6.

[0036] Generally, the exemplary ultracapacitor 10 is packaged within a housing 7 (which may simply be referred to as a "housing 7"), as discussed further herein. The housing 7 is hermetically sealed. In various examples, the package is hermetically sealed by techniques utilizing laser, ultrasonic, and / or welding techniques. The housing 7 (also referred to as a "case") includes at least one terminal 8. Each terminal 8 provides electrical access to the energy stored in the energy storage medium 1.

[0037] In the exemplary EDLC 10, the energy storage medium 1 may be provided by or may include activated carbon, carbon fiber, rayon, graphene, aerogel, carbon fiber cloth, and / or carbon nanotubes. The activated carbon electrode may be produced, for example, by performing a first activation process on a carbon material obtained by carbonization of a carbon compound to produce a carbon substrate, adding a binder to the carbon substrate to produce a molded body, carbonizing the molded body, and finally performing a second activation process on the carbonized molded body to produce an activated carbon electrode.

[0038] Carbon fiber electrodes can be produced, for example, using paper or fabric preforms with high surface area carbon fibers.

[0039] In one particular example, multi-walled carbon nanotubes (MWNTs) on various substrates using chemical vapor deposition (CVD) are fabricated for use in the electrodes 3, 4. In one embodiment, low pressure chemical vapor deposition (LPCVD) is used. The fabrication process may use a gas mixture of acetylene, argon and hydrogen, with an iron catalyst deposited on the substrate using electron beam evaporation and / or sputtering deposition.

[0040] In some embodiments, the materials used to form the energy storage medium 1 may include materials other than pure carbon. For example, various combinations of materials to provide a binder may be included. Generally, however, the energy storage medium 1 is formed substantially from carbon and is therefore referred to as a "carbonaceous material."

[0041] In summary, energy storage medium 1 is formed primarily from carbon, but may include any form of carbon and any additives or impurities deemed appropriate or acceptable to provide the desired functionality as energy storage medium 1.

[0042] The electrolyte 6 includes multiple pairings of cations 9 and anions 11, and in some embodiments may include a solvent, various combinations of each of which may be used. In the exemplary EDLC 10, the cation 11 may include 1-(3-cyanopropyl)-3-methylimidazolium, 1,2-dimethyl-3-propylimidazolium, 1,3-bis(3-cyanopropyl)imidazolium, 1,3-diethoxyimidazolium, 1-butyl-1-methylpiperidinium, 1-butyl-2,3-dimethylimidazolium, 1-butyl-3-methylimidazolium, 1-butyl-4-methylpyridinium, 1-butylpyridinium, 1-decyl-3-methylimidazolium, 1-ethyl-3-methylimidazolium, 3-methyl-1-propylpyridinium, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, and combinations thereof, as well as other equivalents deemed suitable.

[0043] Additionally, in the exemplary EDLC 10, anion 9 may include bis(trifluoromethanesulfonate)imide, tris(trifluoromethanesulfonate)methide, dicyanamide, tetrafluoroborate, hexafluorophosphate, trifluoromethanesulfonate, bis(pentafluoroethanesulfonate)imide, thiocyanate, trifluoro(trifluoromethyl)borate, spiro-(1,1')-bipyrrolidinium tetrafluoroborate salts, other potential salts such as tetraethylammonium tetrafluoroborate, and combinations thereof, as well as other equivalents as deemed suitable.

[0044] The solvent may include acetonitrile, amides, benzonitrile, butyrolactone, cyclic ethers, dibutyl carbonate, diethyl carbonate, diethyl ether, dimethoxyethane, dimethyl carbonate, dimethylformamide, dimethylsulfone, dioxane, dioxolane, ethyl formate, ethylene carbonate, ethyl methyl carbonate, lactones, linear ethers, methyl formate, methyl propionate, methyltetrahydrofuran, nitriles, nitrobenzene, nitromethane, n-methylpyrrolidone, propylene carbonate, sulfolane, sulfones, tetrahydrofuran, tetramethylenesulfone, thiophenes, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, carbonates, gamma-butyrolactone, nitriles, tricyanohexane, butyronitrile, ethylene carbonate, methylene dichloride, and any combination thereof, or other materials that exhibit suitable performance characteristics.

[0045] Separator 5 may be made from non-woven glass. Separator 5 may also be made from fiberglass, fluoropolymers, Teflon (PTFE), and ceramics. For example, using non-woven glass, separator 5 may include main fibers and binder fibers, each having a smaller fiber diameter, that allow the main fibers to be bonded together.

[0046] The above description of the concepts related to ultracapacitor 10 provides a background for the chip caps disclosed and discussed herein.

[0047] 2 and 3, the tip cap 100 includes a body 101 and a lid 102 mounted thereon. Disposed within the body 101 and lid 102 is a capacitance 103 including a tip cap storage cell 105 immersed in or wetted by an electrolyte 126. The body 101 may also be referred to as part of the housing 7, or as a "container" or "package," or by other similar terms. In general, the tip cap storage cell 105 operates according to the principles described above with respect to the ultracapacitor storage cell 12. Further aspects of the tip cap storage cell 105 (hereinafter referred to as "storage cell 105") are described below.

[0048] In some embodiments, the body 101 and the lid 102 mounted thereto may have dimensions selected as suitable for microelectronic applications. For example, in some embodiments, the body 101 and the lid 102 mounted thereto are configured for surface mounting on a printed circuit board, where when surface mounted, the body 101 and the lid 102 extend above a major surface of the die printed circuit board by about 5.0 mm, 4.0 mm, 3.5 mm, 3.0 mm, or less. In some embodiments, the body 101 has a maximum lateral dimension of about 5.0 cm, 4.0 cm, 3.0 cm, 2.0 cm, 1.0 cm, 0.5 cm, 0.25 cm, or less. In some embodiments, the body 101 has a maximum lateral dimension of about 25.0 cm, 4.0 cm, 3.0 cm, 2.0 cm, 1.0 cm, 0.5 cm, 0.25 cm, or less. 2 , 16.0cm 2 , 9.0cm 2 , 1.0cm 2 , 0.25cm 2 , 0.1cm 2 , 0.075cm 2 , 0.05cm 2 or occupies a horizontal area less than or equal to that.

[0049] In some embodiments, the side of the lid 102 facing the inside of the body 101 may include a corrosion-resistant coating or layer (e.g., of a polymeric or plastic material such as PTFE or polyimide) to prevent unwanted physical or electrical contact between the lid and the storage cells 105.

[0050] The process of constructing the tip cap 100 begins with the manufacturing of the storage cells 105 and the creation of the body 101.

[0051] The first step in the construction of the energy storage cell 105 involves the creation of the electrodes. An example of a double-sided electrode 600 is shown in Figure 4A. Generally, and as shown in Figure 4A, each double-sided electrode 600 includes a current collector 2 with an energy storage medium 1 disposed on one side thereof.

[0052] Some embodiments of the electrode include five main components, including an aluminum current collector 2, a polymeric primer layer (also referred to as the "active material") provided to promote adhesion of the energy storage medium 1, and a ternary active material. The active material may include, for example, activated carbon (to improve capacitance), carbon black (to provide high electrical conductivity and reduce equivalent series resistance (ESR)), and a polymeric binder (to bind the powder together).

[0053] In some embodiments, carbon nanotubes (CNTs) are used as an alternative material to provide for adhesives and bonding matrices. That is, primers may be replaced with CNT adhesion layers (ALs) and polymeric binders for active materials may also be replaced with CNTs. CNTs may also reduce or replace carbon black as a conductive aid. The resulting electrodes (i.e., electrodes that do not contain polymers or other adhesives) are "binder-free." Such binder-free electrodes may advantageously operate under extreme conditions (e.g., high pressure and / or high temperature) without degradation due to electrochemical reactions between the binder and the surrounding materials (e.g., electrolyte). Without wishing to be bound by theory, it is understood that in some embodiments, electrostatic attraction (e.g., van der Waals bonds) between carbons in binder-free electrodes provides sufficient adhesion and cohesion to maintain the integrity of the electrode even under harsh conditions. For example, in some embodiments, the binder-free electrodes may exhibit little or no detrimental delamination even when subjected to a reflow process (as detailed herein) or when subjected to operating voltages of at least 2.0 V, or at least 2.1 V or more, at operating temperatures of 65° C., 85° C., 100° C., 125° C., 150° C. or more.

[0054] In some embodiments of binder-free electrodes, the active medium includes activated carbon (or other types of carbonaceous materials) bound by a matrix of carbon nanotubes (CNTs), and the active layer is a matrix of carbon nanotubes (CNTs) that does not include other fillers. Advantageously (e.g., to reduce manufacturing costs), in some embodiments, the weight concentration of CNTs in the active layer may be relatively low, e.g., less than 50%, 40%, 30%, 20%, 10%, 7.5%, 5.0%, 2.5%, or less, depending on the desired performance characteristics of the electrode.

[0055] In some embodiments, the matrix is ​​achieved by dispersing activated carbon powder and / or powder containing carbon nanotubes (CNTs) in isopropyl alcohol using sonication and sufficient energy to debundle the carbon nanotubes (CNTs) from one another. Successful dispersion can be characterized by material separation and appearance, for example, whether the CNT material separates from the solvent and appears as a smooth film when dried.

[0056] The bond and adhesion strength of the active medium and active layer, respectively, are both affected by the dispersion performance of the CNTs within their slurries (along with CNT characteristics, drying time, layer thickness, substrate material, substrate texture, etc.). The dispersion of the CNTs is affected by the choice of solvent (and CNT characteristics, concentration, material purity, use of surfactants, batch size, dispersion settings such as sonicator amplitude, duty cycle, temperature, probe depth, agitation performance, etc.).

[0057] The adhesion of the active medium to the current collector 2 can be improved by adding an adhesion layer (AL) of carbon nanotubes (CNTs) to the current collector 2. This may be done by casting a layer of active medium on a stainless steel (SS) plate, drying it, and using a roll-to-roll machine compressing a different plate with vertically aligned carbon nanotubes against the aluminum carbide coated current collector 2 to transfer the CNTs, and then pressing the plate with active medium against the current collector 2 / CNT layer to form an electrode.

[0058] In some embodiments, electrode fabrication is accomplished by casting a thin layer of carbon nanotube (CNT) slurry directly onto a current collector 2, drying the thin layer, and then casting the active medium slurry on top of it.

[0059] Several techniques may be used to place all layers of active media on the electrode. In one example involving calendaring, a layer of active media is cast on a stainless steel (SS) plate and dried, then a roll-to-roll machine is used to compress a different plate with vertically aligned carbon nanotubes (VACNTs) against an aluminum carbide coated current collector 2 to transfer the vertically aligned carbon nanotubes (VACNTs), and then the plate with active media is pressed against an aluminum carbide coated current collector 2 hosting the vertically aligned carbon nanotubes (VACNTs) to form the electrode. In another example, a thin layer of carbon nanotubes (CNTs) is cast as a slurry directly onto the current collector 2, dried, and the active media is cast as a slurry on top of the thin layer of carbon nanotubes (CNTs).

[0060] The selection of activated carbon involves an evaluation of capacitance versus lifetime; that is, it was found that there is often a trade-off between the highest capacitance material and the longest lifetime material. In general, it was found that the quality of the activated carbon should be determined empirically. Also, with regard to the selection of the active CNT powder, it was found that the longer the CNT, the stronger the matrix; the lower the CNT walls, the better the density efficiency; high purity of the CNT avoids reactive content; pores can be oxidized to expose the inner surface of the CNT, but this may result in the addition of impurities. With regard to the selection of the adhesive layer powder, it was found that for length, cohesion versus adhesion should be evaluated, as too long CNTs will be too self-adhesive and will peel off from the current collector 2, and a thinner layer of CNTs will mitigate the risk of peeling off from the current collector 2. With regard to the calendaring technique, the carbon nanotube (CNT) matrix may be "activated" by applying pressure so that it is less powdery after the CNTs are bonded, and higher pressures provide better density, but with diminishing returns; starting the calendaring process at low pressure and gradually increasing it with additional passes seems to help bond the layers together in some cases. Care should be taken to avoid overuse, as this can lead to delamination. More calendar passes can increase density slightly, but the risk of overusing or wrinkling the current collector 2 will increase.

[0061] The adhesive layer may include carbon nanotubes (CNTs), carbon nanofibers, metal nanowires, and ceramic nanofibers. For the active material, coffee (bonded) carbon nanotubes (CNTs) may be used, as well as carbon nanofibers, metal nanowires, and / or ceramic nanofibers. For the active material energy storage, activated carbon may be used, and / or other forms of carbon may be used, such as carbon black, additional carbon nanotubes (CNTs), soot, jet black, buckyballs, fullerenes, graphite, graphene, nanohorns, nanoonions. The carbon nanotubes (CNTs) used may be single-walled, double-walled, multi-walled, or of any length, diameter, purity, crystallinity, or other configuration as deemed appropriate.

[0062] In various embodiments, the size (dimension) of the electrode ranges between about 20 μm and about 350 μm. In various embodiments, the thickness of the current collector ranges between about 10 μm and about 50 μm. In various embodiments, the thickness of the adhesive layer ranges between about 2 μm and about 10 μm or more. The thickness of the active material disposed on the adhesive layer may be between about 5 μm and about 150 μm or more. In some embodiments, the carbon nanotubes (CNTs) used in the adhesive layer have a diameter between about 1 nm and about 200 nm, a length between about 1 μm and about 1000 μm, and a number of walls (layers) between about 1 and 100. In some embodiments, the carbon nanotubes (CNTs) used in the active material have a diameter between about 1 nm and about 200 nm, a length between about 1 μm and about 1000 μm, and a number of walls (layers) between about 1 and 100. In some embodiments, the active agent comprises substantially spherical particles exhibiting diameters between about 2 μm and about 30 μm.

[0063] In some embodiments, compression of the energy storage medium is applied after drying. Typically, this helps to lock the carbon nanotubes (CNTs) in place. A roll press, hydraulic press, or other type of press may be used. Care should be taken to avoid damaging the current collectors.

[0064] In various embodiments, the electrode layer may be formed using any of the techniques described in International Application Publication No. WO / 2018 / 102652, published June 7, 2018, the entire contents of which are incorporated herein by reference.

[0065] To collect current from groups of positive and negative electrodes, a plurality of left-handed ( FIG. 4B ) and right-handed ( FIG. 4C ) double-sided electrodes 600 are fabricated. Typically, each of the left-handed or right-handed double-sided electrodes 600 includes an energy storage medium 1 disposed on either side thereof, and a conductive tab 602 that is substantially free of the energy storage medium 1.

[0066] The electrodes may be stamped from the sheet material using a suitable press. The electrodes stamped from the sheet material exhibit suitable dimensions for use in the energy storage cell 105. Once the electrodes are cut to the appropriate dimensions, they may be fabricated. Fabrication of the electrodes to the appropriate dimensions may include, for example, calendaring each electrode to ensure retention of the energy storage medium 1, trimming edges, and heat treating to promote migration and reduction of any impurities. After fabrication, the electrodes may be moved to a suitable environment in preparation for assembly.

[0067] Once manufactured and suitable for use, the double-sided electrode 600 is incorporated into a stack assembly. To proceed to assembly of the stack, a suitable separator 5 is provided. The separator 5 may be manufactured from a separator material.

[0068] In some embodiments, separator 5 is cut from a supply of separator material, which in one embodiment is a supply of polytetrafluoroethylene (PTFE). PTFE is a synthetic fluoropolymer of tetrafluoroethylene (commonly known as TEFLON®, available from Chemours, Delaware). PTFE is a polymeric compound composed entirely of carbon and fluorine, and is therefore a fluorocarbon solid. In an exemplary embodiment, separator 5 is 25 μm thick. An example of an active stack assembly with a single separator 5 is shown in FIG. 5.

[0069] 5 depicts an embodiment of the concept of a "z-fold" arrangement of energy storage medium 1. In a z-fold embodiment, a layer of separator 5 is formed from a single piece of separator material that is folded in a z-fold. The z-fold separator 5 includes opposing positive and negative electrodes 4 and 3 and associated current collectors 2 folded thereon. Generally, as referred to herein, the multiple layer assembly of electrodes, current collectors, and separators is referred to as a "stack 201," and may also be referred to as an "active stack," or other similar terminology.

[0070] To produce the z-fold stack 201, once the separator 5 is cut, a first of the double-sided electrodes 600 is placed on one end of the separator 5. The separator 5 is then folded over and one opposing double-sided electrode 600 is placed on the separator 5. The process continues until a completed stack 201 is provided. In one embodiment, the completed stack 201 includes fifteen double-sided electrodes 600. In this example, the completed stack 201 would have eight (8) layers of negative electrodes and seven (7) layers of positive electrodes. In this embodiment, each double-sided electrode 600 has an area of ​​energy storage material 1 of approximately 6 mm by 8 mm. The exposed portion of the current collector 2, which serves as an integral tab, has dimensions of approximately 1.5 mm by 8 mm.

[0071] In general, the stack 201 is configured to provide a desired level of electrical performance. It is not required or necessary that the stack 201 be provided in a z-fold configuration. In some embodiments, each layer of the stack 201 is separated by an individual separator 5. In some embodiments, each layer of the stack 201 may be contained within an envelope of separator material (i.e., surrounded by separator material).

[0072] Similarly, all of the storage cells 105 may be provided within an envelope of separator material or other suitable protective barrier (e.g., an electrically insulating thermoplastic material or other suitable material). In some embodiments, this envelope may contain an electrolyte that wets the stack 201 and prevents the electrolyte from contacting elements external to the barrier. In some such embodiments, a conductive tab 602 may extend outwardly through the envelope to provide electrical communication between the stack 201 and the leads (123, 124). Alternatively, in some embodiments, the leads (123, 124) may extend through the envelope for connection to the tab 602. Typically, the envelope may be hermetically sealed (e.g., heat sealed) around such electrical connections to prevent leakage of the electrolyte from the envelope.

[0073] In various embodiments, the storage cell 105 may be formed using any of the techniques described in International Application Publication No. WO2015102716A8 published on November 26, 2015, or International Application Publication No. WO / 2016057983A3 published on June 30, 2016, the contents of which are incorporated herein by reference in their entireties.

[0074] In some embodiments, stack 201 is constructed by cutting (e.g., using a blade or cutting laser) or stamping electrode layers from a sheet of electrode material. The electrode material may include a sheet of material suitable for use as a current collector 2 with energy storage material 1 disposed on either side. Alternating layers in stack 201 make up the negative and positive electrodes. Separator material is interleaved between each layer and wrapped around the final assembly to form the completed stack 201.

[0075] As the stack 201 includes multiple layers of electrodes, there are multiple conductive tabs 602. The multiple conductive tabs 602 extend beyond the energy storage medium 1 to provide electrical contact. In the stack 201, the conductive tabs 602 are grouped by polarity and formed into a single negative lead 123 and a single positive lead 124. Collectively, assembly of the stack 201 with the negative lead 123 and positive lead 124 provides a storage cell 105. An illustration of the storage cell 105 in its assembled form is provided in FIG. 6.

[0076] In some embodiments, the grouping of the conductive tabs 602 into one each of the single negative lead 123 and the single positive lead 124 is performed by pre-bending the conductive leads prior to assembly of the storage cell 105. When the storage cell 105 is placed within the body 101, the groups of conductive tabs 602 are welded to their respective pads 110 (FIG. 7), thereby forming integral leads (123, 124). The welding may be performed, for example, by ultrasonic welding or laser welding.

[0077] 7 depicts an embodiment of the body 101. The body 101 of the tip cap 100 may be fabricated from a dielectric material, such as various forms of ceramic materials. Contained within the body 101 are electrical pads 110 for conducting electrical current from the storage cell 105 once placed therein. The electrical pads 110 may also conduct electrical current to the storage cell 105 for recharging the tip cap 100.

[0078] In the illustration of Figure 7, the body 101 generally includes a base 111 and four walls 112 that extend around the periphery of the base 111. The body 101 thus provides a container within which the energy storage cells 105 may be placed. The underside of this example of the body 101 is shown in Figure 8.

[0079] As shown in FIG. 8 , the underside of the bottom 111 of the body 101 includes electrical contacts 121 separated by a dielectric 120. At least some of the contacts 121 are in electrical communication with the electrical pads 110, allowing for energy transfer from the chip cap storage cells 105 to a circuit board on which the chip cap 100 may be mounted. Generally, energy is transferred from the electrical pads 110 to the contacts 121 through conductors or vias (not shown) housed within the body 101 and surrounded by the dielectric 121. For example, in some embodiments, the body may house one or more conductive slabs (e.g., embedded within the bottom 110 of the body 101) that establish electrical communication between the electrical pads 110 and the contacts 121. These slabs may be made of, for example, tungsten or other suitable conductive material.

[0080] Thus, for each double-sided electrode 600, a conductive path is formed from the current collector 2 through the conductive tab 602 and each lead (123, 124) to each electrical pad 110, and from the electrical pad 110 through conductive vias in the body 101 to one or more contacts 121 on the bottom surface of the body 101.

[0081] The internal electrical pads 110 are exposed to a capacitance 103 (also referred to herein as a "cavity") within the body 101. The lid 102 may comprise a compatible material such as a ceramic or metallic material. During assembly of the tip cap 100, the lid 102 is hermetically sealed to the body 101 by being sealed with a seal ring 114. The resulting hermetic seal provides environmental integrity by preventing environmental ingress into the tip cap 100 as well as leakage of electrolyte from the tip cap 100. A hermetic seal includes any type of seal that renders the tip cap 100 substantially airtight (blocking the passage of electrolyte, air, oxygen, or other gaseous substances) to ensure proper performance at the intended service interval.

[0082] Examples of devices suitable for use as body 101 include devices in the surface mount device (SMD) product line available from NTK Technologies of Nagoya, Japan. Other examples are available from Schott AG of Landshut, Germany, and Adtech Ceramics Company of Chattanooga, Tennessee, USA.

[0083] In some embodiments, the body 101 is a high temperature co-fired ceramic device. Generally, a co-fired ceramic device is a monolithic ceramic microelectronic device in which the entire ceramic support structure and any conductive, resistive and dielectric materials are fired simultaneously in a kiln.

[0084] Typically, co-fired ceramic devices are made by processing multiple layers independently and assembling them into a device as a final step. Co-firing may be divided into low temperature (LTCC) and high temperature (HTCC) applications; that is, low temperature devices are manufactured at sintering temperatures below 1,000 degrees Celsius (1,830 degrees Fahrenheit), while high temperature is around 1,600 degrees Celsius (2,910 degrees Fahrenheit). Compared to LTCC, HTCC has a more resistive conductive layer.

[0085] HTCC packages typically contain multiple layers of alumina oxide (Al2O3) with tungsten (W) and molybdenum manganese (MoMn) metallization. Advantages of HTCC include mechanical rigidity and hermeticity, both of which are important in high reliability and environmentally stressful applications. Another advantage of HTCC technology is its heat dissipation capabilities.

[0086] A typical ceramic package uses alumina ceramic (Al2O3) in various purities and compositions to support different applications. A typical ceramic package is made up of 90-94 percent alumina, the remainder may consist of alkaline earth silicates or other binders, such as magnesia (MgO) or silica (SiO2), to control grain size and to bind the alumina together.

[0087] The body 101 may be provided as a multi-layer ceramic package with a metallization layer that carries power from the storage cells 105 to the external contacts 121. This metallization layer can be made of tungsten (W) or molybdenum manganese (MoMn) in the case of high temperature co-fired ceramics (HTCC), or gold (Au) or copper (Cu) in the case of low temperature co-fired ceramics (LTCC).

[0088] Typically, a plating process is performed over the metallization layer to protect it from oxidation. If a metallization process such as the gold (Au) metallization process used in LTCC is used, no additional plating is necessary. Typically, the plating layer includes nickel (Ni) as a base, followed by a thin (0.3 μm) layer of gold (Au) for oxidation protection. Alternative plating metals include titanium (Ti) and palladium (Pd). The selected combination of plating metals may be directed to the formation of strong and reliable wire bonds.

[0089] Notably, when the storage cells 105 are disposed within the body 101 (FIG. 9), the components of the stack 201 (i.e., the current collectors 2 and the energy storage medium 1) may be separated from the body 101 (and / or the lid 102) by a layer of separator material. This embodiment, referred to as an "isolated stack," provides substantial protection from potential failure due to shorting of the storage cells 105. In some embodiments, the isolated stack is achieved by providing the storage cells 105 within an electrically insulating envelope, such as an envelope made from a separator material. Once the storage cells 105 are manufactured, they may be set aside for subsequent installation within the body 101.

[0090] The body 101 may be manufactured according to desired specifications (such as dimensions, electrical design, environmental constraints, etc.) At least one pocket or well may be added to confine the sealant to the area surrounding the electrical pad 110.

[0091] 10, in some embodiments, electrical pads 110 are disposed within each well 205. Each of the wells 205 represents a depression in the upper surface of the base 111. In general, the space provided by each well 205 may be used to fold a portion of each lead (123, 124), thereby maximizing the available volume for the stack 201. It should be noted that the term "well" may be used interchangeably with other terms, such as "recess," "recess," "pocket," and other similar terms.

[0092] Each electrical pad 110 may be a homogenous material. For example, electrical pad 110 may be one of tungsten (W), aluminum (Al), gold (Au), or other conductive materials. In some embodiments, electrical pad 110 is plated with any plating material. The plating layer, or simply plating 131, may include, for example, gold (Au), nickel (Ni), or copper (Cu). In some further embodiments, electrical pad 110 is layered. For example, electrical pad 110 may include an underlayer of tungsten (W) with an overlayer of nickel (Ni). The overlayer of nickel (Ni) further includes a gold (Au) plating 131.

[0093] Generally, the materials used in the electrical pads 110 and optional plating 131 are selected as a balance of electrical conductivity and low reactance with the selected electrolyte 126. Limited electrolyte interaction is further achieved by proper construction of the body 101 and bonding of the leads (123, 124). At least one sealant may be used as part of such construction and bonding.

[0094] Gold (Au), nickel (Ni) and tungsten (W) may corrode in the presence of common electrolytes, especially under potential differences. The resulting corrosion of the plated or metallized layers would cause premature degradation of the electrolyte and reduced performance of the welded joint of the tip cap 100. Therefore, a non-reactive sealant may be used to prevent contact between the plated / metallized layers and the electrolyte. As discussed herein, the term "non-reactive" refers to a level of reactivity that is generally believed to result in relative performance enhancement.

[0095] For each of the electrical pads 110, a conductive leader 210 may be bonded to the electrical pad 110. The bonding may be performed, for example, by welding. The welding may be laser welding, ultrasonic welding, or resistance welding. In some other embodiments, a conductive epoxy may be used to bond the conductive tabs 210 to the electrical pads 110. In some embodiments, the conductive leader 210 is formed from aluminum (Al). The configuration of the conductive leader 210 may vary depending on, for example, the location of the respective electrodes and the configuration of the body 101.

[0096] In one embodiment, the conductive leader 210 is one of the leads (123, 124) for the electrode stack 201. In these embodiments, it may be such that only welding is required to join the electrode stack 201 to the body 101. In another embodiment, the conductive leader 210 is an intermediate material that is initially separate from each lead (123, 124) and the electrical pad 110, and the conductive leader 210 is then joined to each lead (123, 124) after a sealant is applied.

[0097] Once the conductive tab 210 is bonded to the electrical pad 110, a sealant may be poured onto the area around the perimeter of the pad 110 and the conductive tab 210. The sealant is then cured. Curing methods may include the use of heat, ultraviolet radiation, water / oxygen, evaporation, or other techniques to harden a suitable sealant material.

[0098] In various embodiments, other sealant technologies may be used. For example, in some embodiments, a conformal layer of sealant may be placed on the desired portion of the package. Generally, the conformal layer includes a thin film that "fits" the contours of the body 101 to accommodate any imperfections and limit its permeability. The conformal layer may be provided as a highly viscous component that is easy to flow.

[0099] In general, for any conformal coating method used to passivate the interior electrical pads 110, care is taken to ensure that the conformal coating does not cover exterior features, seal rings, and other suitable features, as appropriate. In some embodiments, the material selected for the conformal coating does not interfere with bonding processes (such as welding).

[0100] In one embodiment, the conformal coating comprises a high temperature thermoplastic polyimide. The high temperature thermoplastic polyimide may be provided as a material that exhibits a viscosity slightly higher than water and can be dispensed via a syringe. The resulting insulating layer of material is between about 3-20 μm thick and exhibits strong bonding with ceramic, aluminum, gold, silicone, and other materials. In some embodiments, the high temperature thermoplastic polyimide may include silver or other metal flakes to make the material conductive. In one embodiment, the high temperature thermoplastic polyimide is stored at about minus 40 degrees Celsius, operated at ambient temperature, and subjected to a cure cycle at about 150 degrees Celsius for about 10 minutes. The cure cycle will cause the high temperature thermoplastic polyimide to crystallize and release most of the excess materials (NMP and H20) in the form of gas. An additional heating cycle of about 2 minutes and about 250 degrees Celsius may be performed to remove the excess materials. The process results in a conformal coating with high insulating properties and very low thermal expansion.

[0101] One example of a suitable material is available from MATERION, Buffalo, NY, USA, and sold as BONDFLOW. BONDFLOW contains RM 1-methyl-2-pyrrolidone (CAS 872-50-4).

[0102] Once the stack 201 is placed within the body 101 and electrically connected to the electrical pads 110 , an electrolyte 126 is added to the remaining capacitance 103 within the body 101 .

[0103] In some embodiments, the electrolyte 126 is a combination of an ionic liquid, an ionic salt, and a solvent. Typically, the ionic liquid and the solvent are mixed to achieve a mixture. The mixture may be entirely ionic liquid with no solvent. In some embodiments, the electrolyte is about 20 percent ionic liquid and 80 percent solvent (by volume). Mixtures of subranges may also be used.

[0104] Generally, ionic salts may be added to the ionic liquid as an additional ion storage source, with different cation and anion sizes provided to increase efficiency given the surface area presented by the electrode. Ionic salts may be added to the mixture in the range of about 0 M to 2 M (molar concentration, or moles salt / liter of solution).

[0105] The body 101 and storage cells 105 installed therein may then be weighed and filled with an appropriate amount of electrolyte. Filling may be done, for example, by use of a micropipette. Once filled, the combination of body 101 and storage cells 105 may be placed in a low pressure environment (i.e., under a vacuum). The low pressure facilitates the movement of electrolyte 126 into storage cells 105. The assembly may then be weighed again to ensure a steady supply of electrolyte 126. If the assembled body 101, storage cells 105 and electrolyte assembly is within the desired parameters, the assembly is sent for welding of the lid 102. The lid 102 may then be welded to the body 101. The welding may be performed in an inert environment, for example, using a seam welder.

[0106] In various embodiments, care is taken to avoid unwanted impurities in the volume 103 housing the energy storage cells 105. In some embodiments, the total concentration of halide ions is maintained at about 1,000 ppm, 500 ppm, 200 ppm, 100 ppm or less in the cavity of the housing body containing the energy storage cells. In some embodiments, the metal species impurities are maintained at about 1,000 ppm, 500 ppm, 200 ppm, 100 ppm or less in the cavity of the housing body containing the energy storage cells. In some embodiments, the impurities of bromoethane, ethyl chloride, 1-bromobutane, 1-chlorobutane, 1-methylimidazole, ethyl acetate, and methylene chloride are maintained at about 1,000 ppm, 500 ppm, 200 ppm, 100 ppm or less in the cavity of the housing body containing the energy storage cells. In some embodiments, moisture is maintained at about 1,000 ppm, 500 ppm, 200 ppm, 100 ppm, 50 ppm, 10 ppm or less within the cavity of the housing body containing the energy storage cell. In some embodiments, halide impurities are maintained at about 1,000 ppm, 500 ppm, 200 ppm, 100 ppm, 50 ppm, 10 ppm or less within the cavity of the housing body containing the energy storage cell.

[0107] In various embodiments, the electrolyte may be of any type described in International Publication No. WO2015102716A8, published November 26, 2015, and International Publication No. WO / 2016204820A2, published December 22, 2016, the contents of which are incorporated by reference in their entireties. For example, in some embodiments, the electrolyte may include a gel or solid electrolyte of the type described in the aforementioned documents.

[0108] Figure 11 provides a top-down view of the assembly of Figure 9. In Figure 11, the storage cell 105 and the body 101 are bisected by an imaginary axis -A. Figure 12 is a cutaway depiction of the storage cell 105 and the body 101 along the imaginary axis -A.

[0109] As shown in FIG. 12, the storage cell 105 includes multiple layers. Protruding from the multiple layers are a number of conductive tabs 602. In this cross section, the multiple conductive tabs 602 are grouped together to collectively provide the negative lead 123. During assembly, the negative lead 123 is formed into the appropriate shape and bonded to each one of the electrical pads 110, and the same process is performed for the positive lead 124 (not shown in this cross section). The body 101 is then filled with an embodiment of an electrolyte 126 suitable for the tip cap 100. The electrolyte 126 wets the leads (123, 124) and the contents of the storage cell 105.

[0110] In some embodiments, the energy storage cell 105 may be a symmetric EDLC with equal masses of active material on the positive and negative electrodes of the capacitor. However, having equal electrode masses may prevent the EDLC from having the maximum possible specific capacitance when the anions and cations in the electrolyte are of different sizes, because the electrodes and electrolyte may not be fully utilized. In some embodiments, this problem can be solved by balancing the masses by adjusting the electrode masses according to the size of the ions, e.g., increasing the specific capacitance of the EDLC. In some embodiments, the stack 201 may include an unequal number of positive and negative electrode layers to provide improved mass balancing.

[0111] The resulting chip cap 100 is robust to manufacturing processes that typically destroy competitive devices. One example of such a manufacturing process is that of "reflow." In a reflow process, components are heated to a temperature sufficient to cause solder to flow. Efficient mass production of electronic components generally requires the use of a reflow process. Additionally, compact designs often utilize surface mount devices to limit the space used by components, and also rely on the reflow process.

[0112] In one embodiment, the chip cap 100 is mounted to a printed circuit board according to a recommended solder reflow profile. A graphical illustration of temperature versus time is provided in FIG. 13. In the example of FIG. 13, the temperature is increased at three (3) degrees Celsius per second to a preheat stage (called "soak"). In the preheat stage, the chip cap 100 is maintained at a temperature between about 150 degrees Celsius and about 160 degrees Celsius for about 100 seconds. The temperature is then increased at three (3) degrees Celsius per second to a reflow temperature (called "reflow"). The reflow temperature may be reached at about 260 degrees Celsius. Generally, the time above 200 degrees Celsius should be less than about 60 seconds, after which the mounted chip cap 100 is cooled at a rate of about 6 degrees Celsius or less.

[0113] In some embodiments, the tip cap 100 may exhibit a capacitance degradation of 10%, 5%, 2.5% or less in response to 1, 2, 3, 4 or more reflow cycle processes. In some embodiments, the tip cap 100 may exhibit an ESR increase of 10%, 5%, 2.5% or less in response to 1, 2, 3, 4 or more reflow cycle processes. In some embodiments, the reflow process may advantageously increase the capacitance and / or decrease the ESR of the tip cap, essentially acting as a seasoning process for the device.

[0114] Evaluation of the tip cap 100 demonstrated excellent performance. To provide some context for the evaluation, some terminology is introduced.

[0115] Electrical circuit theory deals with ideal resistors, capacitors, and inductors, each of which is assumed to contribute simply resistance, capacitance, or inductance to a circuit. However, all components have nonzero values ​​of each of these parameters. In particular, all physical devices are constructed from materials that have finite electrical resistance, and as a result, physical components have some resistance in addition to other properties. The physical cause of ESR depends on the device in question.

[0116] In non-electrolytic and electrolytic capacitors with solid electrolytes, the metal resistance of the leads and electrodes and dielectric losses cause the ESR. Typical estimates of ESR for ceramic capacitors are 0.01 to 0.1 ohms. The ESR of non-electrolytic capacitors tends to be fairly stable over time, i.e., for most purposes, practical non-electrolytic capacitors can be treated as ideal components.

[0117] Aluminum and tantalum electrolytic capacitors with non-solid electrolytes have very high ESR values, up to several ohms. Prior art electrolytic capacitors of higher capacitance have lower ESR. ESR decreases with frequency up to the self-resonant frequency of the capacitor. A significant problem, especially with aluminum electrolytes, is that ESR increases over time with use. Even if the measured capacitance remains within tolerances, the ESR may increase enough to cause circuit failure and even component damage. While this occurs with normal aging, high temperatures and large ripple currents exacerbate the problem. In circuits with significant ripple currents, increased ESR will increase heat dissipation, thereby accelerating aging.

[0118] Electrolytic capacitors that are rated for high temperature operation and are of higher quality than basic consumer grade parts are less likely to fail prematurely due to increased ESR. Inexpensive electrolytic capacitors may be rated for less than 1000 hours of life at 85°C. Higher grade parts are typically rated for thousands of hours at the maximum rated temperature. Where ESR is important, some specifications with higher temperature ratings, "low ESR", or larger capacitance as otherwise required may be advantageous.

[0119] Tip caps of the type herein have demonstrated superior performance under demanding conditions. In some embodiments, the tip caps may have an operating voltage of at least 2.0V, 2.1V, 2.2V 2.3V, 2.4V, 2.5V, 3.0V, or more. In some embodiments, the tip caps may have a capacitance of at least 300mF, 400mF, 450mF, 500mF, or more. In some embodiments, the tip caps may have an energy density of at least 4.0J / cc, 4.5J / cc, 5.0J / cc, 5.1J / cc, or more. In some embodiments, the tip caps may have a peak power density of at least 15W / cc, at least 20W / cc, at least 22W / cc, or more. In some embodiments, the device may have an equivalent series resistance of 500mΩ or less, an equivalent series resistance of 400mΩ or less, or an equivalent series resistance of 300mΩ or less. In some embodiments, the device may have an operating temperature rating of at least 65° C., 75° C., 85° C., 100° C., 125° C., 150° C., or more. In general, the aforementioned performance parameters may be achieved using a tip cap housing a single energy storage cell. Extended performance (e.g., higher voltage operation) may be achieved by using multiple tip caps and / or tip caps incorporating multiple energy storage cells.

[0120] In abuse tests, tip caps of the type described herein may demonstrate an operational life of at least 1,000, at least 1,500, at least 2,000 hours, or more, at an operating voltage of at least 2.0V or 2.1V or more (e.g., 2.5V, 3.0V, or more) and an operating temperature of 65° C., 85° C., 100° C., or more, while exhibiting at least less than 30% capacitance degradation and less than 100% equivalent series resistance increase. In some embodiments, the aforementioned operational life may be demonstrated after soldering the device to a printed circuit board using a reflow process having at least 1, 2, 3, 4, 5, 6, or more temperature cycles of at least 30 seconds, 60 seconds, 120 seconds, 180 seconds, 240 seconds, 360 seconds, or more, with a peak temperature of at least 100° C., 200° C., 300° C., or more. Advantageously, the aforementioned levels of abuse test performance are expected to equate to operational lives well in excess of 2,000 hours under non-abuse conditions. For example, in some representative applications (e.g., providing sustained power for solid-state drives in an enterprise computing environment), the tip cap may have an operational life of 5,000 hours, 7,500 hours, 10,000 hours, 12,500 hours, or more, even under conditions requiring thousands, tens of thousands, hundreds of thousands, or millions of charge-discharge cycles.

[0121] 14-16 depict performance aspects for an embodiment of the tip cap 100. FIG. 14 depicts ESR performance data for a sample tip cap operated at 85° C. As shown in the graph, for 3800 hours at that temperature, the ESR degradation of the tip cap performance is 98 percent. Comparative data is provided in FIG. 15, which shows a substantially greater ESR degradation relative to the prior art device. Additional performance data for the tip cap is provided in FIG. 16. In FIG. 16, the 85° C. capacitance degradation data is only 72% of the initial cell performance after 3800 hours of testing.

[0122] 17A-17B show performance aspects for an embodiment of the tip cap 100. FIG. 17A shows ESR performance data for a sample tip cap operated at 85° C. with a voltage of 2.1 V. As shown in the graph, the ESR degradation of the tip cap performance is less than 40 percent for 2,500 hours at that temperature and voltage. Additional performance data for the tip cap is provided in FIG. 17B. In FIG. 17B, the capacitance degradation data at 85° C. with a voltage of 2.1 V is less than 14% of the initial cell performance after 2,500 hours of testing. Note that the testing was performed after the tip cap was successfully subjected to a solder reflow process.

[0123] 18A-18B show performance aspects for an embodiment of the tip cap 100. FIG. 18A shows ESR performance data for a sample tip cap operated at 100° C. with a voltage of 2.1 V. As shown in the graph, the ESR degradation of the tip cap performance is less than 65 percent for 1,500 hours at that temperature and voltage. Additional performance data for the tip cap is provided in FIG. 18B. In FIG. 18B, the capacitance degradation data at 100° C. with a voltage of 2.1 V is less than 14% of the initial cell performance after 1,500 hours of testing. Note that the testing was performed after the tip cap was successfully subjected to a solder reflow process.

[0124] Referring to FIG. 19, an example of a computing device 500 that may utilize the tip cap 100 is shown. The computing device 500 may be any one of a personal computer (PC) 501, a laptop 502, a tablet 503, a mobile device (such as a smartphone), and a server 505. Other types of computing devices may be included. Examples include controllers for industrial systems, residential systems (appliances, home electronics, etc.), as well as automotive systems. In short, a computing device utilizing the tip cap 100 may include any electronic device where board level power is required (e.g., solid state drives used in enterprise computing). In some embodiments, the tip cap may be used in extreme downhole conditions known in the field of oil and gas drilling and production, for example, if the tip has an operating temperature rating of 100° C., 125° C., 150° C., or higher.

[0125] In the illustrated diagram, tip cap 100 is used to provide power to computer memory 501. Storage device 510 can be any type of memory. Power converters and controllers suitable for converting power from tip cap 100 are not shown here as such devices are known in the art.

[0126] Referring to FIG. 20, a process flow for assembling a tip cap of the type disclosed herein is shown. In step 2001, an electrode roll is provided. The electrode roll may be a double-sided electrode roll having a carbonaceous energy storage medium on the opposite side of a metal foil current collector. In step 2002, a portion of the carbonaceous energy storage medium is removed (e.g., by scraping) to expose a strip of current collector. In step 2003, left-handed and right-handed electrode layers are punched or cut from the roll, with conductive tabs formed from the exposed portions of the roll. In step 2004, the punched electrode layers are assembled with a separator to form a stack of the type described in detail herein. In step 2005, any excess separator is cut off and the stack is clamped so that the conductive tabs extend from the stack. In step 2006, the electrode stack is vacuum dried to remove moisture. In step 2007, the stack is moved into the open body of the respective package. In step 2008, electrical connections are made from the stack to contact pads in the package, as detailed herein. In step 2009, the stack is placed into the package. In step 2010, electrolyte is dispensed to wet the electrode layers of the stack. In step 2011, a lid is placed on the package. In step 2012, the lid is welded to the package to form a hermetic seal. In step 2013, the completed chip cap is visually inspected and electrically tested. In step 2014, the chip cap is packaged, for example, by taping and rolling the package in a format suitable for pick-and-place installation techniques well known in the art.

[0127] Generally, as used herein, the term "memory" refers to computer hardware integrated circuits that store information for immediate use by a computer, and is synonymous with the term "primary storage device." Computer memory operates at high speeds, such as random access memory (RAM), and is distinct from storage devices that provide slower access information but higher capacity.

[0128] The terms "storage", "primary storage", "main memory", "system memory" and other similar terms are often associated with addressable semiconductor memories, i.e., integrated circuits containing silicon-based transistors used, for example, as primary storage but also for other purposes in computers and other digital electronic devices. There are two main types of semiconductor memories: volatile and non-volatile. Examples of non-volatile memory are flash memory (used as secondary storage) and ROM, PROM, EPROM and EEPROM memories (used to store firmware such as BIOS). Examples of volatile memory are primary storage, typically dynamic random access memory (DRAM), and high-speed CPU cache memory, typically static random access memory (SRAM), which is fast but consumes energy and offers lower storage density than DRAM.

[0129] Volatile memory is computer memory that requires power to maintain stored information. Most modern semiconductor volatile memories are either static RAM (SRAM) or dynamic RAM (DRAM). SRAM retains its contents as long as power is connected. Dynamic RAM is more complicated to interface and control, and requires regular refresh cycles to prevent losing its contents.

[0130] Non-volatile memory is computer memory that can retain stored information even when it is not powered. Examples of non-volatile memory include read-only memory (see ROM), flash memory, most types of magnetic computer storage devices (e.g., hard disk drives, floppy disks, and magnetic tape), optical disks, and earlier computer storage methods such as paper tape and punched cards. Near-term non-volatile memory technologies include FeRAM, CBRAM, PRAM, STT-RAM, SONOS, RRAM, Racetrack memory, NRAM, 3D Crosspoint, and Millipede memory.

[0131] The third category of storage device is "semi-volatile". The term "semi-volatile" generally refers to memory that has some limited non-volatile duration after power is removed, but after which data is eventually lost. The typical goal when using semi-volatile memory is to provide the high performance / endurance / etc. associated with volatile memory, while still offering some of the advantages of true non-volatile memory.

[0132] A solid-state drive (SSD) is a solid-state storage device that uses integrated circuit assemblies as memory to persistently store data. SSDs have no moving mechanical parts. This distinguishes them from traditional electromechanical drives such as hard disk drives (HDDs) or floppy disks, which contain spinning disks and movable read / write heads. Compared to electromechanical drives, SSDs are typically more resistant to physical shocks, operate quieter, and have faster access times and lower latency.

[0133] As of 2017, most SSDs use NAND-based flash memory, a type of non-volatile memory that retains data even when power is lost. For applications that require fast access but not necessarily persistence of data after power loss, SSDs may also be composed of random access memory (RAM). Such devices may use a battery as an integrated power source to retain data for some period of time after loss of external power.

[0134] However, all SSDs still store data in an electrical charge that will slowly leak over time if left without power. This will wear out the storage device (exceeding its endurance rating) and typically cause the data within the storage device to eventually start to be lost. Therefore, current SSDs are not suitable for archival purposes.

[0135] Thus, the performance of SSDs can be substantially improved with the addition of improved power supplies. Many SSDs use capacitors to provide backup power to DRAM modules for writing volatile memory to non-volatile memory. Unfortunately, available capacitors are large and exhibit poor performance.

[0136] In short, the SSD environment presents unique challenges not only to ultracapacitor technology but to all capacitive energy storage. Capacitive storage devices are used as built-in electrical energy backup to transfer data stored in volatile memory (SRAM / DRAM) into non-volatile memory (NAND, FLASH®). Their operation is critical to ensure that data is not lost in the event of a power grid failure. As computing storage becomes more and more critical to almost every commercial sector, the need for highly reliable memory backup solutions is paramount.

[0137] Having thus introduced embodiments of an energy storage device for powering an electrical circuit, some additional aspects are now presented.

[0138] Various other components may be included or required to provide aspects of the teachings herein. For example, additional materials, combinations of materials, and / or omissions of materials may be used to provide additional embodiments within the scope of the teachings herein.

[0139] Various modifications of the teachings herein may be made. Generally, modifications may be designed according to the needs of a user, designer, manufacturer, or other similar interested party. The modifications may be intended to meet particular criteria of performance deemed important by that party.

[0140] No appended claim or claim element should be construed as invoking 35 U.S.C. §112(f) unless the words "means for" or "step for" are expressly used in a particular claim.

[0141] When introducing elements of the invention or embodiments thereof, the articles "a," "an," and "the" are intended to mean that there are one or more of the element. Similarly, the adjective "another," when used to introduce an element, is intended to mean one or more of the element. The terms "including" and "having" are intended to be inclusive so that there may be additional elements other than the listed elements. The term "exemplary" is not intended to mean the best example. Rather, "exemplary" refers to an embodiment that is one of many possible embodiments.

[0142] Although the invention has been described with reference to illustrative embodiments, those skilled in the art will recognize that various modifications can be made and equivalents can be substituted for elements without departing from the scope of the invention. Those skilled in the art will recognize that many modifications can be made to adapt a particular equipment, situation or material to the teachings of the invention without departing from essential scope. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims

1. 1. An energy storage device suitable for mounting on a printed circuit board using a solder reflow process, comprising: a sealed housing body, the housing body including positive and negative internal contacts disposed within the body and in electrical communication with a positive and negative external contact, respectively, each of the external contacts providing electrical communication to an exterior of the body; an electric double layer capacitor (EDLC) energy storage cell disposed within the cavity of the body and comprising a stack of alternating electrode layers and electrically insulating separator layers; an electrolyte disposed within the cavity and wetting the electrode layer; a positive lead electrically connecting a first group of one or more of the electrode layers to the positive inner contact; a negative electrode lead electrically connecting a second group of one or more of the electrode layers to the negative electrode inner contact; An energy storage device comprising:

2. 10. The apparatus of claim 1, wherein each of the electrode layers comprises an energy storage medium that is primarily carbonaceous material substantially free of binder.

3. 3. The apparatus of claim 2, wherein the energy storage medium comprises a network of carbon nanotubes defining a void space, and a carbonaceous material disposed in the void space and bound by the network of carbon nanotubes.

4. 4. The device of claim 3, wherein at least one electrode layer comprises a double-sided electrode layer having an energy storage medium disposed on an opposing side of an electrically conductive current collector layer.

5. 13. The device of any preceding claim, wherein a surface of the energy storage cell in physical contact with the body is made of an electrically insulating material.

6. 10. The device of any preceding claim, wherein each of the electrode layers comprises a conductive tab attached to one of a positive lead and a negative lead.

7. 13. The apparatus of any preceding claim, comprising a corrosion protection feature disposed near one of the internal contacts and configured to limit electrochemical reaction between the internal contact and the electrolyte during operation of the apparatus.

8. 8. The apparatus of claim 7, wherein the internal contact comprises a first material having a relatively high electrochemical activity with respect to the electrolyte, and the corrosion protection feature comprises a protective layer of a second material having a relatively lower electrochemical activity with respect to the electrolyte than the first material, the protective layer being positioned to prevent contact between the first material and the electrolyte.

9. The apparatus of claim 8 , wherein the protective layer comprises a layer of sealant.

10. The apparatus of claim 8 , wherein the protective layer comprises a metal layer disposed on a surface of the first material.

11. The apparatus of claim 8 , wherein the protective layer comprises a metal layer disposed on a surface of the first material and a sealant layer disposed on the metal layer.

12. The apparatus of claim 11 , further comprising a metal shim in the metal layer covering at least a portion of the inner contact and secured by the sealant layer.

13. The apparatus of any one of claims 7 to 12, wherein an inner surface of the body comprises a recess configured to receive at least a portion of the corrosion protection feature.

14. The device of any one of claims 7 to 13, wherein a portion of the positive or negative lead extends through the corrosion protection feature to connect to one of the internal contacts.

15. The apparatus of any one of claims 7 to 14, wherein the corrosion protection feature comprises an aluminium metal layer.

16. The apparatus of any one of claims 7 to 15, wherein the anti-corrosion feature comprises an epoxy sealant.

17. 13. The apparatus of any preceding claim, further comprising an electrically insulating envelope barrier surrounding the energy storage cell and the electrolyte configured to prevent contact of the electrolyte and the energy storage cell with a surface of the cavity.

18. 20. The device of claim 17, wherein the leads extend through the barrier from the energy storage cells to the internal contacts.

19. 20. The apparatus of claim 18, wherein the barrier is heat sealed to the leads to prevent leakage of electrolyte from within the barrier envelope.

20. 13. The device of any preceding claim, wherein the body is a chip configured for surface mounting on a printed circuit board, and wherein when so mounted, the chip extends no more than about 5.0 mm above a major surface of the printed circuit board.

21. 13. The device of any preceding claim, wherein the body is a chip configured for surface mounting on a printed circuit board, and wherein when so mounted, the chip extends no more than about 4.0 mm above a major surface of the printed circuit board.

22. 13. The device of any preceding claim, wherein the body is a chip configured for surface mounting on a printed circuit board, and wherein when so mounted, the chip extends no more than about 3.0 mm above a major surface of the printed circuit board.

23. 13. The device of any preceding claim having an operating voltage of at least 2.0V.

24. 13. The device of any preceding claim having an operating voltage of at least 2.1V.

25. 13. The device of any preceding claim having an operating voltage of at least 2.5V.

26. 13. The device of any preceding claim having an operating voltage of at least 3.0V.

27. 10. A device according to any preceding claim, having a capacitance of at least 300mF.

28. 10. A device according to any preceding claim, having a capacitance of at least 400mF.

29. 13. The device of any preceding claim having an energy density of at least 4.0 J / cc.

30. 13. The apparatus of any preceding claim having a peak power density of at least 15 W / cc.

31. 13. The apparatus of any preceding claim having a peak power density of at least 20 W / cc.

32. 13. The apparatus of any preceding claim having a peak power density of at least 22 W / cc.

33. 13. The device of any preceding claim, having an equivalent series resistance of 500 mΩ or less.

34. 13. The device of any preceding claim, having an equivalent series resistance of 400mΩ or less.

35. 10. The device of any preceding claim, having an equivalent series resistance of 300mΩ or less.

36. 13. The device of any preceding claim, having an operational life of at least 2,000 hours at an operating voltage of at least 2.0 V and an operating temperature of at least 65° C., while exhibiting less than 30% capacitance degradation and less than 100% equivalent series resistance increase.

37. 13. The device of any preceding claim, having an operational life of at least 2,000 hours at an operating voltage of at least 2.0 V and an operating temperature of at least 85° C., while exhibiting less than 30% capacitance degradation and less than 100% equivalent series resistance increase.

38. 13. The device of any preceding claim, having an operational life of at least 2,000 hours at an operating voltage of at least 2.0 V and an operating temperature of at least 100° C., while exhibiting less than 30% capacitance degradation and less than 100% equivalent series resistance increase.

39. 39. The device of any one of claims 36 to 38, wherein said operational life occurs after said device is soldered to a printed circuit board using a reflow process having at least one temperature cycle of at least 30 seconds with a peak temperature of at least 200°C.

40. 36. The device of any one of claims 35, wherein the operational life occurs after the device is soldered to a printed circuit board using a reflow process having at least four temperature cycles of at least 30 seconds each with a peak temperature of at least 200°C.

41. 13. The apparatus of any preceding claim, wherein the energy storage cell provides backup power to at least one additional component mounted on the circuit board.

42. 20. The device of any preceding claim, wherein the electrolyte comprises an ionic liquid.

43. 43. The apparatus of claim 42, wherein the electrolyte further comprises a salt.

44. 44. The apparatus of claim 42 or claim 43, wherein the electrolyte further comprises a solvent.

45. 10. The apparatus of any preceding claim, wherein the housing body is hermetically sealed.

46. 10. The apparatus of any preceding claim, wherein within the cavity of the housing body enclosing the energy storage cell, a total concentration of halide ions is maintained below about 1,000 ppm.

47. 10. The apparatus of any preceding claim, wherein metallic impurities are maintained below about 1,000 ppm within the cavity of the housing body enclosing the energy storage cell.

48. 13. The apparatus of any preceding claim, wherein within the cavity of the housing body enclosing the energy storage cell, the impurities of bromoethane, ethyl chloride, 1-bromobutane, 1-chlorobutane, 1-methylimidazole, ethyl acetate, and methylene chloride are maintained below about 1,000 ppm.

49. 10. The apparatus of any preceding claim, wherein moisture is maintained below about 100 ppm within the cavity of the housing body enclosing the energy storage cell.

50. 10. The apparatus of any preceding claim, wherein halide impurities are maintained below about 200 ppm within the cavity of the housing body containing the energy storage cell.

51. 13. The apparatus of any preceding claim, wherein the apparatus comprises a single energy storage cell housed within the hermetically sealed housing body.

52. 13. The device of any preceding claim, having an operating temperature of at least 65°C at an operating voltage of 2.1V.

53. 13. The device of any preceding claim, having an operating temperature of at least 85°C at an operating voltage of 2.1V.

54. 13. A device according to any preceding claim, having an operating temperature of at least 100°C at an operating voltage of 2.1V.

55. 20. The device of any preceding claim, wherein the electrolyte comprises a cation selected from the list consisting of 1-(3-cyanopropyl)-3-methylimidazolium, 1,2-dimethyl-3-propylimidazolium, 1,3-bis(3-cyanopropyl)imidazolium, 1,3-diethoxyimidazolium, 1-butyl-1-methylpiperidinium, 1-butyl-2,3-dimethylimidazolium, 1-butyl-3-methylimidazolium, 1-butyl-4-methylpyridinium, 1-butylpyridinium, 1-decyl-3-methylimidazolium, 1-ethyl-3-methylimidazolium, 3-methyl-1-propylpyridinium, and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide.

56. The device of any preceding claim, wherein the electrolyte comprises an anion selected from the list consisting of bis(trifluoromethanesulfonate)imide, tris(trifluoromethanesulfonate)methide, dicyanamide, tetrafluoroborate, hexafluorophosphate, trifluoromethanesulfonate, bis(pentafluoroethanesulfonate)imide, thiocyanate, trifluoro(trifluoromethyl)borate, spiro-(1,1')-bipyrrolidinium tetrafluoroborate salt, another potential salt tetraethylammonium tetrafluoroborate, and combinations thereof, as well as other equivalents as deemed suitable.

57. 13. The device of any preceding claim, wherein the electrolyte comprises a solvent selected from the list consisting of acetonitrile, amides, benzonitrile, butyrolactone, cyclic ethers, dibutyl carbonate, diethyl carbonate, diethyl ether, dimethoxyethane, dimethyl carbonate, dimethylformamide, dimethylsulfone, dioxane, dioxolane, ethyl formate, ethylene carbonate, ethyl methyl carbonate, lactones, linear ethers, methyl formate, methyl propionate, methyltetrahydrofuran, nitriles, nitrobenzene, nitromethane, n-methylpyrrolidone, propylene carbonate, sulfolane, sulfones, tetrahydrofuran, tetramethylenesulfone, thiophenes, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, carbonates, gamma-butyrolactone, nitriles, tricyanohexane, butyronitrile, ethylene carbonate, and methylene dichloride.

58. 10. The device of any preceding claim, wherein the electrolyte comprises a gel.

59. 13. The device of any preceding claim, wherein the electrolyte comprises a solid electrolyte.

60. 13. The device of any preceding claim, wherein the stack includes unequal numbers of positive and negative electrode layers configured to promote mass balancing of the stack based on the relative sizes of cations and anions in the electrolyte.

61. 1. A method for making an energy storage device suitable for mounting on a printed circuit board using a solder reflow process, comprising: forming an electric double layer capacitor (EDLC) energy storage cell comprising a stack of alternating electrode layers and electrically insulating separator layers; disposing the energy storage cell within a housing body including a positive internal contact and a negative internal contact disposed within the body; at least partially filling the body with an electrolyte solution to wet the electrode layers; electrically connecting a positive lead from one or more of said first group of electrode layers to said positive inner contact; electrically connecting a negative lead from one or more of the second group of electrode layers to the negative electrode inner contact; and sealing the housing body having the energy storage cell disposed therein; A method for providing the above.

62. 62. The method of claim 61, wherein sealing the housing body comprises hermetically sealing the housing body.

63. 1. A method for providing energy to a device mounted on a printed circuit board, comprising: Mounting a device according to any one of claims 1 to 60 on said printed circuit board using a solder reflow process; and repeatedly charging and discharging the apparatus at an operating voltage and temperature to provide energy to a device. The method, wherein the operating voltage is at least 2V and the operating temperature is at least 65°C.

64. 64. The method of claim 63, wherein the operating temperature is at least 85°C.

65. 65. The method of any of claims 63-64, comprising repeatedly charging and discharging the device at operating voltages and temperatures to provide energy to the device for at least 2,000 hours while the device exhibits less than 30% capacitance degradation and less than 100% equivalent series resistance increase.

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