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Electrode, electrochemical device, and method of making electrodeRelated Patent Categories: Metal Working, Method Of Mechanical Manufacture, Electrical Device MakingElectrode, electrochemical device, and method of making electrode description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20050241137, Electrode, electrochemical device, and method of making electrode. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to an electrode usable in electrochemical devices such as primary batteries, secondary batteries (lithium-ion secondary batteries in particular), electrolytic cells, and capacitors (electrochemical capacitors in particular), an electrochemical device equipped therewith, and a method of manufacturing an electrode. [0003] 2. Related Background Art [0004] Electrochemical devices such as high-energy batteries typified by lithium ion secondary batteries and electrochemical capacitors typified by electric double layer capacitors have widely been in use in portable devices and the like. Such an electrochemical device mainly comprises a pair of electrodes and an electrolyte (e.g., a liquid electrolyte or solid electrolyte) interposed between the electrodes. [0005] In general, such an electrode of the electrochemical device comprises an active material containing layer stacked on a planar collector, whereas the active material containing layer includes a number of particles containing an active material. Proposed as a method of manufacturing such an electrode is one comprising the steps of preparing a kneaded product including a particle containing an active material, a binder, and a conductive auxiliary agent particle; extending the kneaded product wit a hot roller machine or hot press machine, so as to yield an active material containing sheet, and bonding the active material containing sheet to the collector (see, for example, Japanese Patent Application Laid-Open No. 2004-2105). SUMMARY OF THE INVENTION [0006] However, the electrode manufactured by the above-mentioned method has been found to exhibit a relatively high contact resistance between the particle containing the active material and the collector. When such an electrode is used in an electrochemical device, the internal resistance of the electrochemical device becomes higher, whereby the electrochemical device may be obstructed from achieving higher output or higher energy density. [0007] A view of the problem mentioned above, it is an object of the present invention to provide an electrode which can filly lower the contact resistance between a particle containing an active material and a collector, an electrode equipped therewith, and a method of manufacturing the electrode. [0008] The inventors conducted diligent studies in order to achieve the above-mentioned object and, as a result, have found the following. Namely, the conventional active material containing sheet formed by expanding a material kneaded product with a pair of rollers has a relatively smooth surface, whereby the conventional electrode comprises such an active material containing sheet having a relatively smooth surface and a planar collector bonded thereto. Therefore, the contact area between the active material containing sheet and the collector is not sufficient, whereby the contact resistance between the particle containing the active material and the collector is high. [0009] Therefore, m one aspect, the present invention provides an electrode comprising a planar collector, and an active material containing layer disposed on the collector; wherein the active material containing layer comprises a plurality of particles containing an active material and a binder for binding the particles containing the active material to each other and the particles containing the active material to the collector, the collector having a surface depressed in conformity to a form of the particles containing the active material. [0010] In another aspect, the present invention provides an electrochemical device comprising a pair of electrodes and an electrolyte interposed between the electrodes; wherein at least one of the pair of electrodes includes an active material containing layer comprising a plurality of particles containing an active material, and a binder for binding the particles containing the active material to each other and the particles containing the active material to the collector, the collector having a surface depressed in conformity to a form of the particles containing the active material. [0011] In such an electrode, the collector is depressed in conformity to the form of particles containing an active material whereby the contact area between the particles containing the active material and the collector can be made larger than the conventional one. This can lower the internal resistance of the electrochemical device using such an electrode, thereby enabling the electrochemical device to raise its power and improve its energy density. [0012] It will be preferred if the binder in the active material containing layer includes a conductive auxiliary agent particle, since a conduction path is further formed thereby between the particles containing the active material and the collector, whereby the contact resistance can further be lowered. This is also more preferable in that a conduction path is further formed between the particles containing the active material, so that the contact resistance between the particles containing the active material can be reduced, whereby the resistance of the active material containing layer itself can greatly be lowered. [0013] Preferably, the particles containing an active material in the active material containing layer have a particle size of 0.1 to 500 .mu.m. When the particle size of the particles containing the active material is smaller than 0.1 .mu.m the particles containing the active material tend to flocculate and thus are less likely to disperse uniformly in the active material containing layer. When the active material containing layer includes a conductive auxiliary agent particle in particular, the contact between the particles containing the active material and the conductive auxiliary agent particle may become uneven, and the contact between the particles containing the active material, the conductive auxiliary agent particle, and the binder may become uneven, whereby problems may occur in their adhesions. When the particles containing the active material have a particle size exceeding 500 .mu.m, on the other hand, the electrolyte and the like in the particles containing the active material tend to exhibit a greater resistance to diffuse, whereas the specific surface area of the particles containing the active material tends to become smaller. Therefore, the capacity of the electrochemical device is harder to [0014] In still another aspect, the present invention provides a method of manufacturing an electrode, the method comprising a particle layer forming step of forming a particle layer including a binder meltable by heating and a plurality of particles containing an active material on a planar collector; and a rolling step of heating the particle layer and extending the particle layer by passing the collector and the particle layer between rotating rollers, so as to bind the particles containing the active material to each other with the binder and bind the particles containing the active material to the collector with the binder. [0015] In the rolling step in this aspect of the present invention, the particles containing the active material are pressed against the collector, so as to dent the surface of the collector. Therefore, the electrode having a surface depressed in conformity to the form of the particles containing the active material such as the one mentioned above can be manufactured favorably. Since the forming of the active material containing layer and the binding (bonding) of the active material containing layer and collector can be carried out at the same time, the number of steps can be made smaller than that conventionally required, whereby the cost can be cut down. [0016] When the particle layer further includes a conductive auxiliary agent particle in the particle layer forming step, the electrode whose binder includes the conductive auxiliary agent particle as mentioned above can be obtained. Such an electrode is more preferable in that it can further reduce the contact resistance between the particles containing the active material and the collector, and can also lower the contact resistance between the particles containing the active material. [0017] Here, it will be preferred if the particle layer includes a plurality of composite particles each comprising the particles containing the active material integrated with each other beforehand by the binder including the conductive auxiliary agent particle. [0018] This can favorably disperse the particles containing the active material and the conductive auxiliary agent particle in the composite particle beforehand Hot-rolling such a particle layer including the composite particles can form a quite favorable electronic conduction path in the active material containing layer. Therefore, the resistance of the active material containing layer can further be reduced. [0019] It will be preferred if the rolling step is carried out by passing the collector and the particle layer between heated rollers, since this allows a single apparatus to perform the heating and rolling. [0020] It will be preferred if a line pressure of 200.times.10.sup.2 to 2000.times.10.sup.2 N/m (about 20 to 200 kgf/cm) is applied between the rollers in the rolling step. When the line pressure the rollers is less than 200.times.10.sup.2 N/n, the particles containing the active material are less likely to dent the collector sufficiently. When the line pressure of the rollers exceeds 2000.times.10.sup.2 N/m, on the other hand, the active material containing layer is consolidated so much that the electrolyte is harder to diffuse in the active material containing layer. Accordingly, the above range of the line pressure can reduce the impedance sufficiently. [0021] It will be preferred in the particle layer forming step if a binder layer, meltable by heating, including a conductive auxiliary agent particle is disposed beforehand on a surface of the collector, and the particle layer is formed on the binder layer. [0022] In this case, the binder layer is also molten at the time of hot rolling, whereby the particles containing the active material and the collector can be bound to each other more favorably. Here, the particles containing the active material dent the molten binder layer, and then the collector. Since the binder layer includes the conductive auxiliary agent particle, employing such a binder layer can also sufficiently lower the contact resistance between the particles containing the active material and the collector. Continue reading about Electrode, electrochemical device, and method of making electrode... Full patent description for Electrode, electrochemical device, and method of making electrode Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Electrode, electrochemical device, and method of making electrode 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. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Electrode, electrochemical device, and method of making electrode or other areas of interest. ### Previous Patent Application: Techniques for providing a structure with through-holes that may be used in a sub-assembly for micro components Next Patent Application: Method for making sensors, and sensors made therefrom Industry Class: Metal working ### FreshPatents.com Support Thank you for viewing the Electrode, electrochemical device, and method of making electrode patent info. IP-related news and info Results in 0.23531 seconds Other interesting Feshpatents.com categories: Canon USA , Celera Genomics , Cephalon, Inc. , Cingular Wireless , Clorox , Colgate-Palmolive , Corning , Cymer , pbckp |
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