The patent's assignee is Iucf-hyu(industry-university
News editors obtained the following quote from the background information supplied by the inventors: "It was reported that a lithium-air battery using oxygen in the air as a positive electrode active material shows quite large discharge capacity because oxygen is always supplied from outside of the battery, and a large amount of lithium metal as a negative active material can be charged in the battery.
"Fundamental structure of the lithium-air battery is shown in FIG. 1. As shown In FIG. 1, the lithium-air battery has structure comprising: a gas diffusion-type oxygen electrode using carbon as a positive electrode 10, lithium metal or lithium compound as a negative electrode 20, and an organic electrolyte 30 between the positive electrode 10 and the negative electrode 20.
"In this lithium-air battery, the lithium metal (Li) of the negative electrode 20 Is dissolved in the organic electrolyte 30 to be lithium ion (Li.sup.++e.sup.-), the lithium ion reaches to the positive electrode 10, and then the ion reacts with oxygen (O.sub.2) in the air of the positive electrode, resulting in making lithium oxide (Li.sub.2O) for conducting discharging. Further, charging is conducted by reducing the lithium oxide (Li.sub.2O) produced as described above by applying high voltage between the two electrodes.
"Charging: Li.sup.++e.sup.-?Li 4OH.sup.-?O.sub.2+2H.sub.2O+4e.sup.-
"In the past, this air battery used organic solvent as an electrolyte, but there was a safety problem when using the battery for a long time because this organic solvent is volatile and mixed with water. Further, on the process supplying air to the positive electrode, the positive electrode is degraded by moisture, carbon dioxide and the like contained in the air, and the moisture, carbon dioxide and the like contained in the air is delivered to the negative electrode through the organic electrolyte and reacted with the lithium in the negative electrode, thereby degrading the negative electrode. As a result, there was a problem of reducing the charging/discharging characteristic of the air battery."
As a supplement to the background information on this patent application, NewsRx correspondents also obtained the inventors' summary information for this patent application: "In order to solve the above-mentioned problems, the present invention is objected to provide an air battery system, which can be safely operated for a long time by preventing degradation of a positive electrode and a negative electrode, resulting from preventing reduction of electrolyte or water permeation.
"In order to solve the above aspects, the present invention provides a lithium-air battery, which comprises: a positive electrode containing an electron-conducting material; a separator; a lithium salt-dissolved organic electrolyte; and a negative electrode, which can occlude and release lithium.
"In the present invention, the positive electrode may be a carbon cloth, a carbon paper or a carbon felt, which is coated with an electron-conducting material, or a selective oxygen permeable membrane. In the present invention, the positive electrode may contain a gas diffusion-type electrode, where electrochemical reaction of oxygen is conducted. For this, it does not used a separate collector, and it is possible to use a carbon cloth, a carbon paper or a carbon felt, which is coated with an electron-conducting material, or a selective oxygen permeable membrane. The selective oxygen permeable membrane may be a membrane, which can be used for manufacturing a gas diffusion layer of the conventional fuel battery.
"The gas diffusion-type positive electrode of the present invention can be manufactured by a method mixing an electron-conducting material and a hinder and then coating the above mixture on a collector such as metal mesh, or making the mixture of the electron-conducting material and the binder in the form of slurry and then coating on the metal mesh and drying thereof. One side of the gas diffusion-type positive electrode manufactured by the said method is exposed to the air, and the other side contacts to an electrolyte.
"Discharging reaction at the gas diffusion-type positive electrode by the present invention can be expressed as follows.
"or 2Li.sup.++1/2O.sub.2+2e.sup.-?Li.sub.2O (2)
"In the above formulas, the lithium ion Li.sup.+ moves from the negative electrode to the surface of the positive electrode through the electrolyte. Further, oxygen O.sub.2 is accepted from the air into inside of the gas diffusion-type electrode. When the Li.sub.2O.sub.2 or Li.sub.2O produced by the discharging reaction is separated on the positive electrode, and covers all reaction sites on the positive electrode, the discharging reaction is completed. Further, electrode reaction during charging is the counter reaction of the reaction formulas (1) and (2). Accordingly, the produced oxygen is released out of the battery, and the lithium ion is reinserted in the negative electrode though the electrolyte.
"In the present invention, the electron-conducting material may be selected from the group consisting of: carbon materials consisting of carbon black, ketjen black, acetylene black, active carbon powder, carbon molecular sieve, carbon nanotube, carbon nanowire, activated carbon having micropores, mesoporous carbon and graphite; metal powder consisting of copper, silver, nickel and aluminum; and polyphenylene derivatives. The electron-conducting material in the gas diffusion-type electrode increases the reaction sites on the positive electrode, and it is preferred to have particle diameter of 40 nm or less and surface area of 1000 m.sup.2/g or more for enhancing dispersion rate of a catalyst.
"In the present invention, the positive electrode may further comprise a metal collector. The collector may be aluminum (Al), nickel (Ni), iron (Fe), titanium (Ti), stainless and the like, but not limited thereto. The shape of the collector may be thin film-type, plate-type, mesh (or grid)-type, foam (or sponge)-type and the like, and it may be the foam (or sponge)-type having good collecting efficiency, preferably.
"In the present invention, the metal collector may be coated with the electron-conducting material like on the positive electrode, preferably, for increasing the reaction sites on the positive electrode.
"In the present invention, the organic electrolyte may be expressed by general formula of R.sup.1(CR.sup.3.sub.2CR.sup.4.sub.2O).sub.nR.sup.2, wherein, n may be 2 to 10, R.sup.1 and R2 may be each independently selected from H, alky, cycloalkyl, aryl, heterocyclyl, heteroaryl, alkoxy, silyl, substituted alkyl, substituted cycloalkyl, substituted aryl, substituted heterocyelyl, substituted heteroaryl, substituted alkoxy, substituted silyl and halogen.
"In the present invention, the R.sup.3 and R.sup.4 may be each independently H, halogen, alkyl, cycloalkyl, aryl, substituted alkyl or substituted aryl.
"In the present invention, the organic electrolyte may be polyethylene oxide, tetraethylene glycol diamine or dimethyl ether.
"In the present invention, the lithium salt may be at least one selected from the group consisting of LiBF.sub.4, LiClO.sub.4, LiPF.sub.6, LiAsF.sub.6, LiCF.sub.3SO.sub.3, Li(CF.sub.3SO.sub.2).sub.2N, LiC.sub.4F.sub.9SO.sub.3, Li(CF.sub.3SO.sub.2).sub.3C and LiBPh.sub.4. The lithium salt may be used alone or in combination. The concentration of the lithium salt may be 0.1 to 2.0 M, preferably.
"In the present invention, the positive electrode may further comprise a binder selected from the group consisting of PVDF, Kynar, polyethylene oxide, polyvinyl alcohol, Teflon, CMC and SBR. The binder plays roles of well adhering the positive electrode active material particles each other, and well adhering the positive electrode active materials on the collector. For example, it may be PVDF, Kynar, polyethylene oxide, polyvinyl alcohol, Teflon, CMC and SBR, but not limited thereto.
"In the present invention, the positive electrode may further comprise a catalyst selected from the group consisting of Pt, Pd, Ru, Rh, Ir, Ag, An, Ti, V, Cr, Mn, Fe, Ni, Co, Cu, Mo, W, Zr, Zn, Ce and La metals, and oxides thereof. The catalyst is an oxidation-reduction catalyst of oxygen, and helps oxidation-reduction of oxygen by being mixed with the conducting material of the gas diffusion-type electrode and coated.
"In the present invention, the separator may be a separator used in a general secondary battery, and it may be selected from a polyethylene or polypropylene polymer separator, or a glass fiber separator.
"In the present invention, the negative electrode may be a lithium metal, a lithium metal composite treated with organic compounds or inorganic compounds, or a lithiated metal-carbon composite.
"In the present invention, the metal of the lithiated metal-carbon composite may be selected from the group consisting of Mg, Ca, Al, Si, Ge, Sn, Pb, As, Bi, Ag, Au, Zn, Cd and Hg.
"In the present invention, the lithiated metal-carbon composite may be a lithiated silicon-carbon composite or a lithiated tin-carbon. The lithiated metal-carbon composite electrode form a stable composite by being inserted in carbon crystal structure while lithium forms alloy with metal at the same time. Accordingly, metal volume is changed little during a charging/discharging process, and therefore, it has effects that the charging/discharging efficiency is improved without reduction of the cycle characteristic, the irreversible capacity during the initial charging/discharging can be controlled, and it can replace the lithium metal negative electrode with low stability.
"In the present invention, the negative electrode may further comprise a binder selected from the group consisting of PVDF, Kynar, polyethylene oxide, polyvinyl alcohol, Teflon, CMC and SBR.
"The shape of the lithium-air battery of the present invention is not particularly limited, but it may be, for example, coin-type, button-type, sheet-type, stacked-type, cylinder-type, plane-type, horn-type and the like. Further, it is also possible to be applied to large-size batteries for electric cars."
For additional information on this patent application, see: Sun,
Keywords for this news article include: Alkenes, Polyenes, Chemistry, Chalcogens, Electrolytes, Hydrocarbons, Polyethylenes, Carbon Dioxide, Vinyl Compounds, Polyvinyl Alcohol, Inorganic Chemicals, Iucf-hyu(industry-university
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