Patent Description:
The disclosure relates to electrochemical cells and in particular to a hybrid electrochemical cell having an energy density typical of a battery and a power density typical of a supercapacitor.

Batteries are used to power portable electronics such as smartphones, tablets, and laptop computers. Batteries have affected various aspects of modern living. There are numerous applications for batteries. Moreover, batteries are integral for renewable energy production from the sun and wind as well as the development of electric and hybrid electric vehicles. Batteries store a large amount of charge through electrochemical reactions and typically take hours to recharge. What is needed is a hybrid electro-chemical cell that is quickly rechargeable like a supercapacitor and that stores a large amount of charge like a battery. <CIT> discloses a hybrid energy storage device including first, second, and third electrodes, a first electrolyte disposed between the first and second electrodes, and a second electrolyte disposed between the second and third electrode. The first electrode, the first electrolyte, and the second electrode form a battery, and the second electrode, the second electrolyte, and the third electrode form a capacitor. The first and third electrodes are directly connected together so that the battery and capacitor are in parallel within the hybrid energy storage device. <CIT> discloses a hybrid electrochemical cell including a continuous anode, a multi-sectional cathode and an electrolyte contacting both the anode and the multi-sectional cathode. The multi-sectional cathode includes a battery cathode section and a capacitor cathode section. <CIT> discloses electrochemical capacitors having at least one electrode made up of an interconnected corrugated carbon-based network (ICCN).

According to the present invention, there is provided a hybrid electrochemical cell according to claim <NUM>.

In some embodiments, the hybrid electrochemical cell further includes a separator between the first conductor and the second conductor to prevent physical contact between the first conductor and the second conductor, while facilitating ion transport between the first conductor and the second conductor. Moreover, at least one exemplary embodiment of the hybrid electrochemical cell relies on lithium-ion (Li-Ion) chemistry. Other exemplary embodiments of the hybrid electrochemical cell are based upon nickel-cadmium (Ni-Cd) and nickel-metal hydride (Ni-MH) chemistries. Further still, some embodiments of the hybrid electrochemical cell are sized to power electric vehicles for transportation, while other embodiments are sized small enough to power implantable medical devices.

Generally described herein is an energy storage technology comprising a supercapacitor designed to store charge on the surface of large surface area materials. In some applications, the disclosed supercapacitor captures and releases energy in seconds and can do so through millions of cycles. Further described herein is an improvement that provides greater charge storage capacity using, for example, power systems that combine supercapacitors and batteries that provide for a high charge storage capacity of batteries and the quick recharge of supercapacitors. Indeed, the inventors have identified, and have described methods, devices, and systems that solve several long-felt and unmet needs for devices that include electrochemical energy storage having relatively fast energy recharge times in contrast to batteries with relatively slow recharge times that limit mobility of a user.

In certain aspects, described herein are power systems, methods, and devices based upon combinations of supercapacitors and batteries for various applications, including by way of non-limiting examples electric and hybrid electric vehicles. For example, electric vehicles are often powered by one of the following energy storage systems: fuel cells, batteries, or supercapacitors. However, installing only one type of conventional energy storage is often insufficient.

In addition, the running cost of the normally available supercapacitor and battery-based power systems is expensive and they are relatively bulky in size. As a result, such power systems are not usable in a practical manner with portable electronics, such as smartphones, tablets, and implantable medical devices.

Advantages of the subject matter described herein are robust and numerous. For example, one advantage of the subject matter described herein is a hybrid electrochemical cell that provides the high energy density of a battery with the high power density of a supercapacitor. In some embodiments, the hybrid electrochemical cells provided herein do not require an electronic converter and/or bulky packaging. As another example, the subject matter described herein provides a hybrid electrochemical cell that combines a supercapacitor and battery that does not necessarily require wiring a battery to a supercapacitor in parallel, nor does it necessarily require expensive electronic converters that are required to control power flow between the battery and supercapacitor.

According to the present invention, there is also provided a method of manufacturing a hybrid electrochemical cell according to claim <NUM>.

The accompanying drawings incorporated in and forming a part of this specification illustrate several aspects of the disclosure, and together with the description, serve to explain the principles of the disclosure.

Upon reading the following description in light of the accompanying drawings, those skilled in the art will understand the concepts of the disclosure and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications are non-limiting and fall within the scope of the disclosure and the accompanying claims.

A feature of the subject matter described herein is a hybrid electrochemical cell. In certain embodiments, the hybrid electrochemical cells described herein comprise nickel-cadmium (Ni-Cd), nickel-metal hydride (Ni-MH) and/or lithium-ion (Li-lon) batteries. <FIG>, for example, depicts a non-limiting structure of a Li-lon based hybrid electrochemical cell <NUM> in accordance with the present disclosure. The hybrid electrochemical cell <NUM> includes a first conductor <NUM> having a single portion <NUM> that is both a first capacitor electrode and a first battery electrode. In the Li-lon based chemistry of the hybrid electrochemical cell <NUM>, the first conductor <NUM> is negative and is doped with lithium ions. The hybrid electrochemical cell <NUM> includes a second conductor <NUM> having at least one portion that is a second capacitor electrode <NUM> and at least one other portion that is a second battery electrode <NUM>. An electrolyte <NUM> is in contact with both the first conductor <NUM> and the second conductor <NUM>. A separator <NUM> between the first conductor <NUM> and the second conductor <NUM> prevents physical contact between the first conductor <NUM> and the second conductor <NUM>, while facilitating ion transport between the first conductor <NUM> and the second conductor <NUM>. The second capacitor electrode <NUM> and the second battery electrode <NUM> are delineated by a horizontal dashed line <NUM> in <FIG>. As shown, a ratio between the portion of the second capacitor electrode <NUM> and the second battery electrode <NUM> is about <NUM>:<NUM>. However, it is to be understood that the ratio between the portion of the second capacitor electrode <NUM> and the second battery electrode <NUM> can range from <NUM>:<NUM> to <NUM>:<NUM> (inclusive of all ratios in between those endpoints, including but not limited to, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, and <NUM>:<NUM>). As the portion of the second capacitor electrode <NUM> increases relative to the second battery electrode <NUM>, the power density of the hybrid electrochemical cell <NUM> increases and the energy density decreases. Likewise, as the portion of the second battery electrode <NUM> increases relative to the second capacitor electrode <NUM>, the energy density of the hybrid electrochemical cell <NUM> increases and the power density decreases. The ratio of the second capacitor electrode <NUM> relative to the second battery electrode <NUM> is predetermined for a given application. For example, a larger ratio of the second capacitor electrode <NUM> relative to the second battery electrode <NUM> is desirable to capture energy quickly in a regenerative braking system, while a smaller ratio of the second capacitor electrode <NUM> relative to the second battery electrode <NUM> might be desirable for energizing a power tool such as a portable electric drill.

In understanding the hybrid electrochemical cell <NUM>, it is helpful to note that a typical lithium ion battery comprises a graphite negative electrode and a layered metal oxide positive electrode. In contrast, a lithium ion capacitor is made of a graphite negative electrode and an activated carbon positive electrode. Since the negative electrode in both designs is graphite, these two devices can be integrated into one cell by connecting internally the battery and capacitor positive electrodes in parallel. The capacitor electrode would act as a buffer to prevent high rate charge and discharge of the battery. This can potentially extend the lifetime of the battery portion of the hybrid cell by a factor of ten, leading to energy storage systems that may never need to be replaced for the lifetime of a product being powered by the hybrid electrochemical cell <NUM>. In addition, given that the positive electrodes of the battery and the capacitor have the same operating voltage and current collector, it is possible to blend them together in one positive electrode as shown in <FIG>. As a result, the hybrid electrochemical cell <NUM>, in certain embodiments, has only two electrodes instead of the four electrodes used in traditional power systems having battery and supercapacitor combinations. The simplified structure and design of the present disclosure's hybrid electrochemical cell <NUM> reduces the manufacturing cost and make powering hybrid automobiles energy efficient. Moreover, the hybrid electrochemical cell <NUM> combines battery technology and supercapacitor technology into a single cell using one type of electrolyte, thereby eliminating extra current collectors, electrolytes, and packaging. This means that the hybrid electrochemical cell <NUM> provides a higher energy density than traditional power systems that combine batteries and supercapacitors with interfacing electronics for power flow control between the batteries and supercapacitors. The hybrid electrochemical cell <NUM> is fabricated using commercial electrode materials, collectors, separators, binders, and electrolytes, which allows for fabrication processes that are readily scalable to industrial levels.

In some embodiments, the first battery electrode material used comprises graphite. Other materials are also suitable. For example, in some embodiments, the first battery electrode comprises hard carbon, silicon, composite alloys Sn(M)-based and Sn(O)-based, and combinations thereof.

In certain embodiments, the second battery electrode material comprises: lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide.

, lithium nickel manganese cobalt oxide, lithium nickel cobalt aluminum oxide, lithium titanium oxide, and/or lithium iron phosphate, and combinations thereof.

The second capacitor electrode <NUM> comprises interconnected corrugated carbon-based network (ICCN) <NUM> and comprises a conformal coating of an active material throughout the three-dimensional structure of the ICCN. The second capacitor electrode <NUM> may further be redox active to store charge via intercalation pseudo-capacitance. In at least one embodiment, the second capacitor electrode <NUM> comprises niobium pentoxide (Nb<NUM>O<NUM>).

Another advantage of the subject matter described herein are methods, devices, and systems that provide for the increased movement of ions, including for example, lithium ions, into and out of the electrodes. A problem with pure lithium ion batteries is the slow movement of lithium ions in and out of the battery electrodes. As described herein, in some applications, the insertion of a supercapacitor electrode in the lithium ion-based hybrid electrochemical cell <NUM> speeds up the charge-discharge process by storing charge via adsorption of ions on the surface of a carbon electrode or through fast redox reactions near the surface of an oxide electrode instead of the bulk of a layered battery material. For example, in a carbon supercapacitor electrode, the charge is stored in an electric double at the interface between the carbon and electrolyte. Here, and in these applications of the methods, devices, and systems described herein, an interface between the electrodes and electrolyte is thought of as an electrical double layer composed of the electrical charge at the surface of the carbon electrode itself and the charge of the ions disbursed in the solution at a small distance from the electrode surface. This electrical double layer is formed when a potential is applied to the electrode and causes a charging current (non-faradaic current) to pass through the hybrid electrochemical cell <NUM>. These reactions are described below.

The following equations describe the charge storage mechanism of certain embodiments of the hybrid electrochemical cell <NUM>, for example, when using graphite as the first battery electrode and lithiated metal oxide as the second battery electrodes and carbon as the second capacitor electrode. At the positive electrode charge storage occurs through a combination of double layer adsorption capacitance and lithium ion insertion. <CHM>
<CHM>.

In this scheme, LiMO<NUM> represents a metal oxide positive material, such as LiCoO<NUM>, x is a fraction <NUM> < x < <NUM>, C is a high surface area form of carbon, e+ is a hole, A- is an electrolyte anion, and ( <MAT>) refers to an electric double layer (EDL) formed at the interface between the carbon electrode and electrolyte.

At the negative electrode, lithium ion insertion into and out of graphite is described by the following equation:
<CHM>.

<FIG> is a non-limiting illustration of a line drawing of a sample of an interconnected corrugated carbon-based network (ICCN) <NUM>, which is made up of a plurality of expanded and interconnected carbon layers that include corrugated carbon layers such as a single corrugated carbon sheet <NUM>. In one embodiment, each of the expanded and interconnected carbon layers comprises at least one corrugated carbon sheet that is one atom thick. In another embodiment, each of the expanded and interconnected carbon layers comprises a plurality of corrugated carbon sheets <NUM>. In this specific example, the thickness of the ICCN <NUM>, as measured from cross-sectional scanning electron microscopy (SEM) and profilometry, was found to be around about <NUM>. In one embodiment, a range of thicknesses of the plurality of expanded and interconnected carbon layers making up the ICCN <NUM> is from around about <NUM> to about <NUM>. In some embodiments, the thickness of the plurality of expanded and interconnected carbon layers making up the ICCN <NUM> is from around about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from <NUM> to about <NUM>, from about <NUM> to about <NUM>, <NUM> to about <NUM>, <NUM> to about <NUM>, <NUM> to about <NUM>, <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>.

In some embodiments, hybrid electrochemical cells in accordance with the present disclosure are also made on a micro-scale which will enable a relatively large number of applications for a new generation of electronics. For example, a micro-hybrid electrochemical cell, in some embodiments, are integrated into implantable medical devices, smart cards, radio frequency identification (RFID) tags, wireless sensors, and even wearable electronics. Integrated micro-hybrid electrochemical cells, in some applications, also serve as a way to better extract energy from solar, mechanical, and thermal sources and thus make more efficient self-powered systems. Micro-hybrid electrochemical cells, in certain embodiments, are also fabricated on the backside of solar cells in both portable devices and rooftop installations to store power generated during the day for use after sundown, helping to provide electricity around the clock when connection to the grid is not possible. Each of these applications is made possible by the subject matter described herein based in part on the flexibility in size and shape of the micro-hybrid electrochemical cells described herein.

<FIG> is a non-limiting diagram illustrating a lithium ion-based micro-hybrid electrochemical cell <NUM>. The micro-hybrid electrochemical cell <NUM> includes a first conductor <NUM> having a single portion <NUM> that is both a first capacitor electrode and a first battery electrode. In the lithium ion-based chemistry of the micro-hybrid electrochemical cell <NUM>, the first conductor <NUM> is negative and is doped with lithium ions. The micro-hybrid electrochemical cell <NUM> includes a second conductor <NUM> having at least one portion that is a second capacitor electrode <NUM> and at least one other portion that is a second battery electrode <NUM>. An electrolyte <NUM> is in contact with both the first conductor <NUM> and the second conductor <NUM>. The second capacitor electrode <NUM> and the second battery electrode <NUM> each have electrode digits with a length L, a width W, and an interspace I. In an exemplary millimeter scale embodiment, the length L is around about <NUM>, the width W ranges from around about <NUM> to around about <NUM>, and the interspace I is typically around about <NUM>. While these dimensions are exemplary, it is to be understood that a further miniaturization of the width W of the electrode digits and the interspace I between the electrode digits in the micro-hybrid electrochemical cell <NUM> would reduce ionic diffusion pathways, thus leading to the micro-hybrid electrochemical cell <NUM> having even higher power density. In an exemplary centimeter scale embodiment, the length L is around about <NUM>, the width W ranges from around about <NUM> to around about <NUM>, and the interspace I is typically around about <NUM>.

In some embodiments, the micro-hybrid electrochemical cell <NUM> is integrated by growing porous positive and negative electrode materials on ICCN interdigitated patterns. In general, methods for producing the micro-hybrid electrochemical cell <NUM> having electrodes made of a patterned ICCN typically include an initial step of receiving a substrate having a carbon-based oxide film. Once the substrate is received, a next step involves generating a light beam having a power density sufficient to reduce portions of the carbon-based oxide film to an ICCN. Another step involves directing the light beam across the carbon-based oxide film in a predetermined pattern via a computerized control system while adjusting the power density of the light beam via the computerized control system according to predetermined power density data associated with the predetermined pattern. Exemplary light sources for generating the light beam include but are not limited to a <NUM> laser, a green laser, and a flash lamp. The light beam emission of the light sources may range from near infrared to ultraviolet wavelengths.

An exemplary process for fabricating the micro-hybrid electrochemical cell <NUM> is schematically illustrated in <FIG>. In some embodiments, the ICCN pattern is created using a consumer-grade digital versatile disc (DVD) burner drive. In a first step, a graphite oxide (GO) dispersion in water is dropcast onto a DVD disc and dried in air to form a graphite oxide film <NUM> (step <NUM>). A micro-pattern made with imaging or drafting software is directly printed onto the GO-coated DVD disc <NUM> (step <NUM>). The GO film absorbs the energy from a laser <NUM> and is converted into an ICCN pattern. With the precision of the laser <NUM>, the DVD burner drive renders the computer-designed pattern onto the GO film to produce the desired ICCN circuits. In certain applications, the ICCN pattern is designed to have three terminals: an ICCN supercapacitor-like electrode and two battery electrodes. In some embodiments, the capacity of the supercapacitor electrode is boosted by the electrophoretic deposition of activated carbon micro-particles.

In further or additional embodiments, anode and/or cathode materials are sequentially electrodeposited on the ICCN scaffold. Voltage-controlled and current-controlled electrodeposition is used to ensure conformal coating of the active materials throughout the three-dimensional (3D) structure of the ICCN. For example, manganese dioxide (MnO<NUM>) is electrodeposited on the ICCN microelectrodes making up the second battery electrode <NUM> (<FIG>) that forms a portion of a cathode and is followed by a lithiation of MnO<NUM> in molten lithium nitrate (LiNO<NUM>) and lithium hydroxide (LiOH) (step <NUM>). In some embodiments, polyaniline is used as an alternative to the cathode material. Next, a nickel-tin alloy, silicon, or even graphite micro-particles are electrodeposited onto ICCN corresponding to the anode (step <NUM>). To complete the micro-hybrid electrochemical cell <NUM>, a drop of electrolyte <NUM> is added to provide ions that allow continuous electron flow when the micro-hybrid electrochemical cell <NUM> is under load (step <NUM>).

In some embodiments, the micro-hybrid electrochemical cell <NUM> is realized using nickel-cadmium (Ni-Cd) and nickel-metal hydride (Ni-MH) chemistries in a similar manner to that of the lithium ion-based hybrid electrochemical cell <NUM> (see <FIG>) except that the chemistry of Ni-Cd or Ni-MH batteries is combined with a Ni-carbon asymmetric supercapacitor.

<FIG> depicts a non-limiting structure for a hybrid electrochemical cell <NUM> for Ni-Cd and Ni-MH chemistries in accordance with the present disclosure. In some embodiments, the hybrid electrochemical battery cell <NUM> includes a first conductor <NUM> having a single portion <NUM> that is both a first capacitor electrode and a first battery electrode. In some embodiments, in either of the Ni-Cd and/or Ni-MH based chemistries of the hybrid electrochemical cell <NUM>, the first conductor <NUM> is positive and includes nickel oxyhydroxide (NiOOH) that reduces to nickel hydroxide (Ni(OH)<NUM>) during discharge. In some embodiments, the hybrid electrochemical cell <NUM> includes a second conductor <NUM> having at least one portion that is a second capacitor electrode <NUM> and at least one other portion that is a second battery electrode <NUM>. In some embodiments, the ions that collect on the second battery electrode <NUM> comprise a metal hydride represented by X in the metal hydride case or Cd(OH)<NUM> represented by Y in the Ni-Cd case. In certain applications, an electrolyte <NUM> is in contact with both the first conductor <NUM> and the second conductor <NUM>, whereby a separator <NUM> between the first conductor <NUM> and the second conductor <NUM> prevents physical contact between the first conductor <NUM> and the second conductor <NUM>, while facilitating ion transport between the first conductor <NUM> and the second conductor <NUM>. In some embodiments, the second capacitor electrode <NUM> and the second battery electrode <NUM> are delineated by a horizontal dashed line <NUM> in <FIG>. As shown, a ratio between the portion of the second capacitor electrode <NUM> and the second battery electrode <NUM> is <NUM>:<NUM>. However, it is to be understood that the ratio between the portion of the second capacitor electrode <NUM> and the second battery electrode <NUM> can range from <NUM>:<NUM> to <NUM>:<NUM> (inclusive of all ratios in between those endpoints, including but not limited to, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, and <NUM>:<NUM>).

In some embodiments, as the portion of the second capacitor electrode <NUM> increases relative to the second battery electrode <NUM>, the power density of the hybrid electrochemical cell <NUM> increases and the energy density decreases. Likewise, in further or additional embodiments, as the portion of the second battery electrode <NUM> increases relative to the second capacitor electrode <NUM>, the energy density of the hybrid electrochemical cell <NUM> increases and the power density decreases. In certain applications, the ratio of the second capacitor electrode <NUM> relative to the second battery electrode <NUM> is predetermined for a given application. For example, a larger ratio of the second capacitor electrode <NUM> relative to the second battery electrode <NUM> is desirable to capture energy quickly in a regenerative braking system, while a smaller ratio of the second capacitor electrode <NUM> relative to the second battery electrode <NUM> might be desirable for energizing a power tool such as a portable electric drill.

In certain applications this design uses a negative electrode made of activated carbon in which the charge is stored in the electric double layer, while the positive electrode is pseudocapacitive (typically NiOOH) where the charge is stored through redox reactions in the bulk of the material. An aqueous alkaline solution is used as an electrolyte in the same way as in Ni-Cd and Ni-MH batteries. Because the positive electrode in Ni-Cd and Ni-MH batteries is NiOOH, the same as in traditional Ni-Cd asymmetric supercapacitors, in certain embodiments, provided is an integration of both devices into one cell by connecting the battery and capacitor negative electrodes in parallel. In further or additional embodiments, also provided is a blend of the battery and capacitor negative electrodes into one electrode.

<FIG> is a non-limiting diagram depicting a micro-hybrid electrochemical cell <NUM> based on either Ni-Cd or Ni-MH chemistries. In some embodiments, the micro-hybrid electrochemical battery cell <NUM> includes a first conductor <NUM> having a single portion <NUM> that is both a first capacitor electrode and a first battery electrode. In further or additional embodiments, during fabrication of the micro-hybrid electrochemical cell <NUM>, the first conductor <NUM> is positive and is doped with NiOOH for use with either Ni-Cd or Ni-MH chemistries. In some embodiments, the micro-hybrid electrochemical cell <NUM> includes a second conductor <NUM> having at least one portion that is a second capacitor electrode <NUM> and at least one other portion that is a second battery electrode <NUM>. In some embodiments, an electrolyte <NUM> is in contact with both the first conductor <NUM> and the second conductor <NUM>. For example, the second capacitor electrode <NUM> and the second battery electrode <NUM> each have electrode digits with a length L, a width W, and an interspace I. In an exemplary embodiment the length L is around about <NUM>, the width W ranges from around about <NUM> to around about <NUM>, and the interspace I is typically around about <NUM>. While these dimensions are exemplary, it is to be understood that a further miniaturization of the width W of the electrode digits and the interspace I between the electrode digits in the micro-hybrid electrochemical cell <NUM> would reduce ionic diffusion pathways, thus leading to the micro-hybrid electrochemical cell <NUM> having even higher power density.

Similar to the fabrication of the Li-lon based micro-hybrid electrochemical cell <NUM>, the micro-hybrid electrochemical cell <NUM>, based on either Ni-Cd or Ni-MH chemistries, in certain embodiments is integrated by growing porous positive and negative electrode materials on ICCN interdigitated patterns. An exemplary process for fabricating the micro-hybrid electrochemical cell <NUM> is schematically illustrated in <FIG>. Steps <NUM> and <NUM> are completed the same as shown in <FIG>. However, new steps are added after step <NUM> to accommodate the Ni-Cd or Ni-MH chemistries to sequentially electrodeposit anode and cathode materials on the ICCN scaffold. As with the fabrication of Li-Ion based micro-hybrid electrochemical cell <NUM>, voltage-controlled and current-controlled electrodeposition is used to ensure conformal coating of the active materials throughout the 3D structure of ICCN. A metal such as lanthanum nickel (LaNis) or palladium (Pd) is electrodeposited on ICCN microelectrodes making up the second battery electrode <NUM> that forms a portion of an anode (step <NUM>). Next, Cd(OH)<NUM> is added to the ICCN corresponding to the anode (step <NUM>). To complete the micro-hybrid electrochemical cell <NUM>, a drop of electrolyte <NUM> is added to provide ions that allow continuous electron flow when the micro-hybrid electrochemical cell <NUM> is under load (step <NUM>).

The electrochemical reactions of the Ni-MH and Ni-Cd based hybrid electrochemical cells are described in the following:.

The metal, M, in the negative electrode of a Ni-MH cell, is actually a hydrogen storage alloy. It comes from a new group of intermetallic compounds which can reversibly store hydrogen. Many different compounds have been developed for this application, but the most extensively adopted are rare earth-based ABs-type alloys. In this type of alloy, the A component consists of one or more rare earth elements, and B is mainly composed of transition metals such as Ni, Co, Mn, and Al. The capacitor electrode stores charge in an electric double layer. ( <MAT>) refers to an electric double layer (EDL) formed at the interface between the carbon electrode and electrolyte, where e- is an electron from the electrode side and <MAT> is a cation from the electrolyte side. In the Ni-MH hybrid electrochemical cell, nickel oxyhydroxide (NiOOH), is the active material in the charged positive electrode. During discharge, it reduces to the lower valence state, nickel hydroxide, Ni(OH)<NUM>, by accepting electrons from the external circuit. These reactions reverse during charging of the cell.

In the Ni-Cd based hybrid electrochemical cell, the negative electrode consists of cadmium metal and high surface area carbons. During charge, Ni(OH)<NUM> is oxidized to the higher valence state and releases electrons to the external circuit. These electrons are stored in the negative electrode by reducing Cd(OH)<NUM> to elemental cadmium and in electric double layers.

<FIG> is a charge-discharge graph of voltage versus time for a prior art lithium ion capacitor. The charge rate and the discharge rate are relatively steep in comparison to a lithium ion battery charge rate and discharge rate shown in <FIG> is a non-limiting charge-discharge graph of voltage versus time for a hybrid electrochemical cell of the present disclosure. Notice that in this case, and in certain embodiments of the present disclosure, the hybrid electrochemical cell has charge rates and discharge rates that are commensurate with both the lithium ion capacitor and the lithium ion battery. As a result, the hybrid electrochemical cells of this disclosure share the best properties of both the lithium ion capacitor and the lithium ion battery and therefore can be thought of as being "super-batteries.

The shape of the charge-discharge graph of the hybrid electrochemical cell is controlled by the type of the second capacitor electrode. For example, <FIG> describes the case when using a double layer capacitor electrode such as ICCN <NUM> or activated carbon. However, when using redox active Nb<NUM>O<NUM>, the behavior is illustrated in <FIG>. Other materials are also suitable.

<FIG> is a graph depicting a charge-discharge curve for a prior art nickel-carbon supercapacitor. In contrast, <FIG> is a graph depicting a charge-discharge curve for both a prior art Ni-Cd battery and a prior art Ni-MH battery. <FIG> is a non-limiting illustration of a charge-discharge graph of voltage versus time for either of the Ni-Cd and the Ni-MH chemistries for embodiments comprising hybrid electrochemical cells of the present disclosure. In essence, the charge-discharge graph of <FIG> can be thought of as the result of a combination of the electrochemical properties of nickel-carbon supercapacitor and Ni-Cd or Ni-MH battery.

A Ragone plot is useful to highlight the improved electrochemical storage ability of the hybrid electrochemical cells of the present disclosure. <FIG> is a Ragone plot comparing the performance of hybrid electrochemical cells with different energy storage devices designed for high-power demanding loads. The Ragone plot shows the gravimetric energy density and power density of the packaged cells for all the devices tested. The Ragone plot reveals a significant increase in performance for energy density in comparison to traditional supercapacitors. Remarkably, compared with lithium ion supercapacitors, hybrid electrochemical cells of certain embodiments of the subject matter described herein store up to ten times more energy and around about the same to slightly greater power density than lithium ion supercapacitors. For example, the hybrid electrochemical cells of the present disclosure have an energy density that ranges between <NUM> watt-hour/kilogram (Wh/kg) to around about <NUM> Wh/kg. Furthermore, although lithium ion batteries can provide high energy density, they have limited power performance that is nearly two orders of magnitude lower than the hybrid electrochemical cells of the present disclosure. For example, the hybrid electrochemical cells of the present disclosure have a power density that ranges between nearly <NUM><NUM> watt/kilogram (W/kg) to about <NUM><NUM> W/kg. This superior energy and power performance of the hybrid electrochemical hybrids will compete, completely replace, and/or complement batteries and supercapacitors, including lithium ion supercapacitors in a variety of applications. Moreover, a further miniaturization of the width of the micro-electrodes and the space between micro-electrodes in micro-hybrid electrochemical cells would reduce ionic diffusion pathways, thus leading to micro-hybrid electrochemical cells with even higher power density.

Applications for the disclosed embodiments of a micro-hybrid electrochemical cell are diverse. The following list is only exemplary. For example, <FIG> is a non-limiting, illustrative depiction of an implantable medical device <NUM> having the micro-hybrid electrochemical cell <NUM> integrated within. <FIG> is a non-limiting, illustrative depiction of a smart card <NUM> having the micro-hybrid electrochemical cell <NUM> integrated within. <FIG> is a non-limiting, illustrative depiction of a radio frequency identification (RFID) tag <NUM> having the micro-hybrid electrochemical cell <NUM> of the present disclosure integrated within. <FIG> is a non-limiting, illustrative depiction of a wireless sensor <NUM> having the micro-hybrid electrochemical cell <NUM> of the present disclosure integrated within. <FIG> is a non-limiting, illustrative depiction of the wearable device <NUM> having a micro-hybrid electrochemical cell <NUM> of the present disclosure integrated within. <FIG> is a non-limiting, illustrative depiction of a solar cell <NUM> having the micro-hybrid electrochemical cell <NUM> of the present disclosure integrated with the solar cell <NUM> to realize a self-powered system. Other self-powered systems that will benefit from integration with the present embodiments include but are not limited to vibrational type energy harvesting systems, wind energy harvesting systems, and temperature differential type energy harvesting systems.

Claim 1:
A hybrid electrochemical cell (<NUM>) comprising:
(a) a first conductor (<NUM>) having at least a one portion (<NUM>) that is both a first capacitor electrode and a first battery electrode;
(b) a second conductor (<NUM>) having at least one portion that is a second capacitor electrode (<NUM>) and at least one other portion that is a second battery electrode (<NUM>); and
(c) an electrolyte (<NUM>) in contact with both the first conductor and the second conductor,
characterized in that the second capacitor electrode comprises an interconnected corrugated carbon-based network, ICCN (<NUM>), having a three-dimensional (3D) structure, wherein the ICCN comprises a plurality of expanded and interconnected carbon layers that include a corrugated carbon layer, wherein each of the plurality of expanded and interconnected carbon layers comprises at least one corrugated carbon sheet that is about one atom thick, and wherein the ICCN comprises a conformal coating of an active material throughout the three-dimensiona (3D) structure of the ICCN.