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  Electrochemical cell suitable for use in electronic deviceUSPTO Application #: 20060201801Title: Electrochemical cell suitable for use in electronic device Abstract: An electrochemical cell for a portable electronic device is provided, said cell having a positive electrode, a negative electrode and an electrolyte, characterised in that at least the positive electrode comprises a mesoporous structure having a periodic arrangement of substantially uniformly sized pores of cross-section of the order of 10−8 to 10−9 m. (end of abstract) Agent: Pearl Cohen Zedek, LLP - New York, NY, US Inventors: Philip Nigel Bartlett, John Robert Owen, Phillip A Nelson USPTO Applicaton #: 20060201801 - Class: 204284000 (USPTO) Related Patent Categories: Chemistry: Electrical And Wave Energy, Apparatus, Electrolytic, Elements, Electrodes, Perforated Or Foraminous The Patent Description & Claims data below is from USPTO Patent Application 20060201801. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] The present invention relates to a novel electrochemical cell, which may be a battery or a supercapacitor or both, and which is suitable for use in portable and other electronic devices, and specifically to such a cell having at least the positive electrode formed of a mesoporous material having a periodic arrangement of substantially uniformly sized pores of cross-section of the order of 10.sup.-8 to 10.sup.-9 m. [0002] It should be noted that the term "battery" is used herein in its common meaning of a device that converts the chemical energy contained in its active components directly into electrical energy by means of a redox (oxidation-reduction) reaction. The basic unit of a battery is an electrochemical cell, which will comprise at least a positive electrode, a negative electrode and an electrolyte, the whole contained within a casing. Other components, such as separators, may be included, as is well known in the art. A battery may consist of one or more such cells. [0003] Many portable electronic devices require power to be available as a steady flow at a relatively low level, interspersed with spikes or surges of much higher power drain. Most conventional batteries are unable to meet these requirements and so may be supplemented with a capacitor or supercapacitor, which stores power when it is not required by the device and releases it when required. Examples of devices having this type of power requirement include notebook computers, mobile telephones, PDAs (personal digital assistants--i.e. microcomputers), defibrillators and the like. However, in such portable devices a high premium is put on portability, which is a function of both weight and size. Any additional equipment in the device inevitably adds to both of these, rendering the device less portable and so less desirable. [0004] A consequent requirement of any electrochemical cell which is to function in such a portable device is that it should have both high power and high energy densities. In the past, it has only been possible to achieve one or the other of these at reasonable cost, and not both. [0005] We have now discovered that the technology of mesoporous films, disclosed, for example, in EP 993 512 or U.S. Pat. No. 6,203,925, may be applied to the production of one or both electrodes of an electrochemical cell, and that the resulting electrochemical cell, which may function as a battery, as a capacitor or as both, can be designed to have both high power density and high energy density. [0006] Thus, the present invention provides an electrochemical cell, which may, for example, be used in a portable electronic device, said cell having a positive electrode, a negative electrode and an electrolyte, characterised in that at least the positive electrode comprises a mesoporous structure having a periodic arrangement of substantially uniformly sized pores of cross-section of the order of 10.sup.-8 to 10.sup.-9 m. [0007] The invention also provides a portable electronic device containing such an electrochemical cell. [0008] The invention still further provides an automotive battery comprising a plurality of the electrochemical cells of the present invention. [0009] The electrochemical cell of the present invention maybe constructed to function as a battery, as a supercapacitor or as a combined battery/supercapacitor. For example, a supercapacitor having mesoporous positive and negative electrodes operates via the mechanism of proton shuttling between a mesoporous positive electrode, e.g. of Ni(OH).sub.2, and a hydrogen absorbing mesoporous negative electrode, e.g. of palladium, as illustrated in the schematic of FIG. 1. The mechanism is similar to that operating in Ni-MH batteries where the palladium is replaced by another hydrogen absorbing material such as LaNi.sub.5. [0010] Examples of portable electronic devices which may include the electrochemical cell of the present invention include: portable computers, including the so-called notebook computers, desktop replacement computers, ultraportable computers etc. (the present invention being of particular value in the smaller versions, such as the ultraportables); mobile telephones; cordless (landline) telephones; PDAs; portable hard disk drives; music players of various sorts, including CD players, cassette players, mini-disk players and other digitally recorded music players, including MP3 and like software-based music players; portable televisions; portable DVD players; portable radios; hybrid devices (i.e. devices serving two or more previously separate functions), such as PDA/mobile telephones, telephone/music players, hard disk storage/music players etc.; and medical devices, such as defibrillators. [0011] The electrochemical cells of the present invention may also be used in automotive batteries. [0012] All of the above devices require a steady supply of power at a relatively low level, interspersed with periodic demands for much higher power at essentially random intervals. They are, therefore especially suited for use with the electrochemical cells of the present invention. The specifics of the design and construction of these devices is well known and, beyond the incorporation of an electrochemical cell according to the present invention, does not form a part of the present invention. [0013] At least the positive electrode, the cathode, of the electrochemical cell of the present invention is formed of a mesoporous material. The material is preferably a metal, a metal oxide, a metal hydroxide, a metal oxy-hydroxide or a combination of any two or more of these. Examples of such metals include: nickel; alloys of nickel, including alloys with a transition metal, nickel/cobalt alloys and iron/nickel alloys; cobalt; platinum; palladium; and ruthenium. Examples of such oxides, hydroxides and oxy-hydroxides include: gold oxide; palladium oxide; nickel oxide (NiO); nickel hydroxide (Ni(OH).sub.2); nickel oxy-hydroxide (NiOOH); and ruthenium oxide. Of these, we most prefer nickel and its oxides and hydroxides. [0014] As is well known in the field, certain of these materials require "conditioning" before use. This may be achieved by putting the cell through several cycles of charging and discharging, as is conventional in the art. A typical material requiring such conditioning is nickel, which, as a result of the conditioning, will acquire a surface layer of an oxide. [0015] There is no limitation on the nature of the material used to manufacture the negative electrode, the anode, of the electrochemical cell of the present invention, and any material may be used having regard to the chemistry of the cell which is to be made. Examples of suitable materials include: carbon; cadmium; iron; a palladium/nickel alloy; an iron/titanium alloy; palladium; or a mixed metal hydride, for example LaNi.sub.5H.sub.x. These materials are preferably porous, and more preferably mesoporous. Of these, preferred materials are carbon and palladium. Mesoporous palladium is, however, not the preferred negative electrode material for low cost applications, due to its high cost. [0016] Preferred combinations of anode and cathode are Nickel/Palladium, Nickel/Carbon, Nickel/Iron and Nickel/Cadmium, of which Nickel/Carbon is most preferred. Where reference is made to nickel, the oxides and hydroxides thereof are also included. [0017] In particular, we prefer that the mesoporous structure of the positive electrode comprises nickel and an oxide, hydroxide or oxy-hydroxide of nickel selected from NiO, Ni(OH).sub.2 and NiOOH, said nickel oxide or hydroxide forming a surface layer over said nickel and extending over at least the pore surfaces, and the negative electrode comprises nanoparticulate carbon. [0018] Thus, preferably the positive electrode and the negative electrode each comprise a mesoporous structure having a periodic arrangement of substantially uniformly sized pores of cross-section of the order of 10.sup.-8 to 10.sup.-9 m. The positive electrode, and the negative electrode if it also is mesoporous, consists of or consists substantially of the mesoporous structure or structures as defined. [0019] By "mesoporous structure", "mesoporous material" and "mesoporous film" as referred to herein are meant structures, materials and films, respectively, that have been fabricated via a liquid crystal templating process, and that consequently are monolithic in nature, and contain a long range, regular arrangement of pores having a defined topology and a substantially uniform pore size (diameter). Accordingly, the mesoporous structures, materials and films may also be described as nanostructured or having nanoarchitecture. [0020] Therefore, the mesoporous materials used in accordance with the invention are distinct from poorly crystallised materials and from composites with discrete nano-sized solid grains, e.g. conventionally denoted `nanomaterials` that are composed of aggregated nanoparticulates. [0021] An advantage of using mesoporous materials, compared with nanomaterials, is that electron transport within the mesoporous material does not encounter grain boundary resistances, affording superior electronic conductivity and removing power losses associated with this phenomenon. Moreover, the ordered porosity of the mesoporous materials used here provides a continuous and relatively straight, non-tortuous path of flow with uniform diameter, encouraging the rapid and unhindered movement of electrolyte species. By contrast, conventional nanoparticulate systems have a disordered porosity with voids of varying cross section interconnected by narrower intervoid spaces. As such, substances moving within the pore structure encounter a considerably tortuous path, impeding reaction rates. [0022] The mesoporous material is preferably in the form of a film of substantially constant thickness. Preferably, the mesoporous film thickness is in the range from 0.5 to 5 micrometers. [0023] Preferably, the mesoporous material has a pore diameter within the range from about 1 to 10 nanometres, more preferably within the range from 2.0 to 8.0 nm. [0024] The mesoporous material may exhibit pore number densities in the range from 1.times.10.sup.10 to 1.times.10.sup.14 pores per cm.sup.2, preferably from 4.times.10.sup.11 to 3.times.10.sup.13 pores per cm.sup.2, and more preferably from 1.times.10.sup.12 to 1.times.10.sup.13 pores per cm.sup.2. Continue reading... Full patent description for Electrochemical cell suitable for use in electronic device Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Electrochemical cell suitable for use in electronic device patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. 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