Corrosion protection using protected electron collector

(Cross-reference of related applications) This application is incorporated herein by reference in its entirety, with US Patent Provisional Applications Serial Numbers 60 / 553,443 and 60 / 553,636, both filed on March 16, 2004, and 2004. Claims priority over No. 60 / 571,776 filed May 17, 2014.

The present invention relates to a battery, and more particularly to a current collector used in a rechargeable lithium battery.

Molten salt electrolytes are considered to be safer than conventional organic electrolytes, especially in automotive applications. However, corrosion of the current collector seriously affects the performance of batteries with molten salt electrolytes, reducing cycle capacity and high speed performance. Corrosion results from the oxidation of the molten salt electrolyte on the surface of the metal collector, typically aluminum (Al) or iron (Fe), during charging or discharging. Corrosion can significantly reduce battery life.

Therefore, if the corrosion of the current collector can be reduced, it becomes possible to use a safer lithium ion (Li-ion) battery, for example, in an automobile application.

U.S. Pat. No. 5,518,839 granted to Olsen describes a nickel-coated aluminum current collector in a solid-state electrochemical cell. However, this does not describe the protection of current collectors in Li-ion batteries with molten salt electrolytes. The patents cited herein are incorporated herein by reference.

<patcit num="1"><text>U.S. Patent Provisional Application Serial Number 60 / 553,443</text></patcit><patcit num="2"><text>U.S. Patent Provisional Application Serial Number 60 / 553,636</text></patcit><patcit num="3"><text>U.S. Patent Provisional Application Serial Number 60 / 571,776</text></patcit><patcit num="4"><text>U.S. Pat. No. 5,518,839</text></patcit><patcit num="5"><text>U.S. Pat. No. 6,224,824</text></patcit><patcit num="6"><text>U.S. Pat. No. 4,448,611</text></patcit><patcit num="7"><text>U.S. Pat. No. 5,938,914</text></patcit><patcit num="8"><text>U.S. Pat. No. 5,591,544</text></patcit><patcit num="9"><text>U.S. Pat. No. 6,402,795</text></patcit><patcit num="10"><text>U.S. Pat. No. 3,639,100</text></patcit><patcit num="11"><text>U.S. Pat. No. 4,463,071</text></patcit><patcit num="12"><text>U.S. Pat. No. 5,552,241</text></patcit><patcit num="13"><text>U.S. Pat. No. 5,589,291</text></patcit><patcit num="14"><text>U.S. Pat. No. 6,326,104</text></patcit><patcit num="15"><text>U.S. Pat. No. 6,365,301</text></patcit><patcit num="16"><text>U.S. Pat. No. 6,544,691</text></patcit>

<p num="0007"> The battery includes a first electrode, a second electrode, an electrolyte such as a molten salt electrolyte, and a current collector associated with the first electrode. The current collector has a surface treatment that reduces corrosion of the current collector due to the molten salt electrolyte. The surface treatment can be a protective layer such as a protective layer containing oxygen, nitrides, sulfides, phosphides, and / or carbides. The protective layer has substantially better corrosion resistance than a current collector such as tungsten or a surface alloy formed on the material of the current collector, such as an aluminum alloy formed on an aluminum current collector. It can be a metal film. The protective layer can include one or more materials selected from the group of materials consisting of metals, metal alloys, metal carbides, metal oxides, and metal phosphates, these examples of which are tungsten, Includes titanium carbide, tantalum carbide, aluminum oxide, titanium oxide, nickel oxide, copper phosphide, nickel phosphide, iron phosphide, and iron nitrides.</p><p num="0008"> The surface treatment can also be an anodic oxidation of the current collector or a treatment that substantially lowers the surface potential of the current collector. In one embodiment, the current collector is substantially an aluminum metal and the protective layer is an aluminum alloy with a lower aluminum content than the current collector.</p><p num="0009"> In one embodiment, the battery is a lithium ion battery with a molten salt electrolyte, however, the improved current collectors described herein can be used, for example, in other battery technologies based on other cation species. it can.</p><p num="0010"> The improved battery includes a current collector having a protective layer on the surface of the current collector. In one embodiment, the current collector is an aluminum foil, and the protective layer is an oxide having at least one element belonging to groups 2 to 14 of the 3rd or subsequent period of the periodic table as its constituent elements. And charcoal having at least one element belonging to groups 2 to 14 of the 3rd or subsequent period of the periodic table as its constituent elements, and the 3rd or subsequent period of the periodic table as its constituent elements. Includes materials such as electron conductive materials selected from the group consisting of nitrides and tungsten having at least one element belonging to groups 2-14. Examples include tin oxide, titanium oxide, indium tin oxide, tantalum oxide, tungsten oxide, chromium oxide, and thallium oxide. The protective layer can also contain magnesium oxide, barium titanate, titanium oxide, zirconium oxide, aluminum oxide, and silica, which have excellent electrochemical stability. Other exemplary protective layers include oxides, carbides, nitrides of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W, as well as oxynitrides, acid carbides, mixed metal compounds (oxides, Includes combinations of materials discussed herein, such as nitrides and carbides), and the like.</p>

A protective layer containing one or more electronically conductive materials should be used in a protective layer placed on a surface that would otherwise be in contact with the molten salt to prevent or delay surface corrosion. Can be done. For example, the surface of the Al current collector in a molten salt Li-ion battery carries a protective layer containing one or more electron conductive materials to substantially protect the Al surface from corrosion by the molten salt electrolyte. be able to.

Improved electronically conductive materials have been developed for use as protective layers. An electron conductive material for a protective layer used in a Li ion battery having a molten salt electrolyte is described. These protective layers can reduce or eliminate decomposition of the surface on which they are placed, such as the surface of the current collector. Electromagnetic materials have properties including high electron conductivity, non-reactivity with molten salts, fine particle types (such as nanoparticles with an average diameter in the range of 0.5 nanometers-1 micron), and high density. be able to.

Conductive materials are generally at least 1x10 under normal operating conditions and operating temperatures of the battery.^-2S / cm, more preferably at least 1x10³It can have a conductivity of S / cm.

A protective layer that can reduce or eliminate the problem of corrosion of the current collector due to the molten salt electrolyte in the lithium ion battery is described. The current collector can include aluminum, iron, other metals, or other conductive materials. Techniques include physical coating of the current collector with an electron conductive material, chemical coating (eg, reduction of the Al surface potential with an oxidation additive), and / or provision of an Al alloy thin film to the accelerated Al.

The new methods and materials form a protective layer on the surface of the component (electrode collector, negative electrode, positive electrode, other electrical component, or housing component) in contact with the molten salt electrolyte to form a protective layer on the surface of the component. It is described to delay or prevent corrosion.

FIG. 1 shows a Li-ion battery structure showing current collectors 10 and 22, electrolytes of negative electrode layers (anode layers) 12, 14 and 18, separator 16 and positive electrode 20. The positive electrode contains a cathode electroactive material, an electron conductive material, and a binder material, and the negative electrode contains an anode electroactive material, an electron conductive material, and a binder material. The current collector is covered by the protective layers shown in 24 and 26, respectively.

When the electrolyte is a molten salt electrolyte and each collector contains aluminum foil (often in a conventional Li-ion battery), the electrolyte decomposes on the aluminum foil.

Some examples described herein describe the provision of a protective layer to an Al current collector in a molten salt Li ion battery. By providing a protective layer on the surface of the Al current collector, corrosion of the Al current collector by the molten salt electrolyte can be substantially prevented, and the cycle capacity of the molten salt Li ion battery can be improved. it can.

However, the present invention is not limited to providing a protective layer to the Al current collector. Current collectors made of other materials can be provided with a protective layer according to the present invention. Protective layers of the same or different composition may also be applied to the surface of the negative and / or positive, or other battery components that would otherwise be in contact with the molten salt.

A protective current collector that alleviates the problem of corrosion of the current collector due to the molten salt electrolyte in the battery, such as a lithium ion battery, is described. The current collector can include aluminum, iron, another metal, or other conductive material. The method of forming the protective layer is to physically coat the current collector with an electron conductive material, chemically coat it (for example, reduce the Al surface potential with an oxidation additive), and / or apply an Al alloy thin film to accelerated Al. Including offer.

In one approach, the protective layer is provided to the current collector, for example, by a physical coating method. The protective layer transmits electrons toward or from the current collector. The protective layer can include a conductive polymer.

For example, current collectors used in rechargeable lithium-based battery systems can be coated with one or more protective layers. Exemplary protective layers are Tungsten (W), Platinum (Pt), Titanium Carbide (TiC), Tantalum Carbide (TaC), Tungsten Carbide (WC), Titanium Oxide (eg Ti).₄O₇), Copper Phosphate (Cu₂P₃), Nickel Phosphate (Ni₂P₃), Iron phosphide (FeP), and the like. The chemical formulas given are exemplary. For example, the term titanium oxide is also TiO₂, And non-stoichiometric compounds of titanium and oxygen, as well as similar ones with the other compounds mentioned above.

Improved current collectors are on the surface of aluminum, or other metals susceptible to corrosion by molten salt electrolytes, and aluminum (or other current collector materials) that act to reduce current collector corrosion. Protective layer can be included. Therefore, the improved battery includes a molten salt electrolyte, electrodes (positive and negative electrodes), and a current collector having a surface treatment that reduces corrosion of the current collector by the molten salt electrolyte.

Surface treatments on the current collector can include chemical and / or physical deposition processes, chemical bathing techniques, anodic oxidation techniques, or combinations of other processes or processes. The current collector can include aluminum, copper, iron, steel (such as stainless steel), nickel, zinc, conductive polymers, metal polymers (such as metal mylar), and the like.

The protective layer can be a polyalkylene oxide (such as polyethylene oxide), a conductive polymer (such as polyethylene oxide), a conductive polymer (polypyrrole, polyaniline, polythiophene, polyvinylidene fluoride, derivatives thereof, or other conductive layers. Polymers such as), polycarbonate, PVDF, polymer composites, and the like can be included.

(Protective layer composition) In other embodiments, the protective layer applied to the current collector is a metal or metal alloy, boride, carbide, nitride, oxide, fluoride, other halide, silicide, phosphide, sulfide ( Or other carbogenides) can be included. Examples include metal boroides, metal carbides, metal nitrides, metal oxides, metal fluorides (and other metal halides), metal silicides, metal phosphates, and metal chalcogenides. The compound can be, for example, a mixed metal compound containing two or more metal species. The protective layer can also contain oxynitrides, acid carbides, or other compounds containing one or more atoms from the C, N, O, Si, P, and S groups.

The protective layer can include layers of solid electrolytes, glass materials, crystalline materials, amorphous materials, elastomers, sol-gels, and the like. The protective layer (such as polyethylene oxide) polyalkylene oxide, conductive polymers (such as polypyrrole), polycarbonate DOO, PVDF, polymer composites (e.g., the lithium compound), and similar polymers, such as those Can be included. Certain compounds can be classified into one or more categories considered herein.

The iron-based protective layer can provide corrosion resistance to molten salt-containing alkaline oxides. Such an iron-based material, such as steel, can be used to protect the current collector in the battery according to the present invention. The protective layer can also include nickel-containing alloys as described in US Pat. No. 6,224,824 granted to Zhang.

Iron (or iron-containing) current collectors can be nitrided to reduce electrolyte corrosion, so the protective layer contains iron nitride. Current collectors such as iron current collectors can be surface treated with an oxidizing bath that reduces surface corrosion, for example, using an oxidizing bath as described in US Pat. No. 4,448,611, granted to Grellet et al. it can. The protective layer can include, for example, copper, silver, or a copper-silver alloy as described in US Pat. No. 5,938,914 granted to Dawless et al.

U.S. Pat. No. 5,591,544, granted to Fauteux et al., Describes methods for reducing the interfacial impedance of aluminum current collectors, including coating with an undercoat material. Such materials can be used in place of or in addition to other techniques to reduce current collector corrosion.

The current collector can be coated with, for example, a metal film such as an electroplated metal film using the electroplating technique described in US Pat. No. 5,518,839 granted to Olsen. Nickel-plated or other metal or alloy-plated current collectors can be used in Li-ion batteries with molten salt electrolytes.

Alternatively, one or more oxidation additives are placed on the surface of the current collector to reduce the surface potential of the current collector and reduce its corrosion by the molten salt electrolyte. For example, using an aluminum current collector, Al₂O₃Alternatively, the NiO thin film can reduce the Al oxidation potential.

Alternatively, the current collector can be coated with a thin alloy membrane, which alloy is resistant to electrolyte corrosion. For example, the aluminum current collector can be coated with an aluminum alloy. The aluminum alloy can be an alloy between aluminum and one or more transition metals.

U.S. Pat. No. 6,402,795 granted to Chu et al. Can be used as a protective layer for electrodes and can also be used in embodiments of the present invention, such as lithium ion permeable materials such as lithium phosphate nitrides. Is disclosed. The lithium ion permeable material used for the electrode protective layer can also be used as a protective layer for a current collector. For example, the protective layer can include lithium compounds (such as lithium salts), lithium alloys (such as LiAl alloys), lithium oxide, hydroxides, or other lithium compounds. The protective layer can contain compounds that form an interlayer compound with lithium ions (such as titanium disulfide) or other sulfides.

In another embodiment, the oxidative coating can be formed on the surface of the current collector by forming a halide coating on the current collector, which is subsequently exposed to a combination of heat and oxygen, It is formed by other chemical treatments and / or exposure of the halide layer to the molten salt electrolyte in the battery. The halide layer can be formed, for example, by using a process sourced from that described in US Pat. No. 3,639,100, granted to Rick. A protective layer of titanium dioxide can be formed on the current collector by a process involving the formation of a titanium halide layer on the current collector, followed by heating in air.

The protective layer contains a mixture of a first conductive material and a second material, such as a composition. The first conductive material can be a metal, a conductive polymer, or another conductive material. The second material can be an oxide (such as a metal oxide), a carbide, a sulfide, a nitride, or another material. Two or more compositions as described herein can be used as a protective layer.

In other embodiments, the protective layer can include a material that is non-reactive (eg, non-catalytic) to the molten salt electrolyte. The protective layer can be an inorganic electron conductive material (such as metals, metal oxides, metal carbides, and the like), an organic electron conductive material such as a conductive polymer, or a combination of organic and inorganic materials (mixed with an organic polymer). (Like inorganic particles) or organically modified silicates can be included.

The protective layer can contain both organic and inorganic components. For example, the protective layer can contain a mixture of inorganic particles (such as TiC, TaC, or W particles) and an electron conductive polymer.

The protective layer can include metals (such as transition metals), metal alloys, metal oxides, metal carbides, metal nitrides, metal oxides, metal oxynitrides, metal acid carbides, or metal phosphates. Examples are W, Pt, TiC, TaC, WC, or Ti.₄O₇including.

The protective layer includes oxides, other oxygen-containing compounds (such as phosphates or sulfates), carbides, phosphates, nitrides, nitrides, sulfides, metals and one or more other elements (S). , N, O, C, and elements selected from the group consisting of P), halides, conductive glass, silicon compounds, semiconductors, conductive plastics, ceramics, alloys, or other conductive (semi-) Can include materials (including conductive).

The protective layer is, for example, an oxide having at least one element belonging to Group 2 to Group 14 of the Periodic Table 3 or the following period as its constituent element, and the third or 3rd element of the Periodic Table as its constituent element. It has a charcoal having at least one element belonging to groups 2 to 14 of the period following it, and at least one element belonging to groups 2 to 14 of the third or subsequent period of the periodic table as its constituent elements. It can be a material such as an electron conductive material, which is a material selected from the group consisting of nitrides and tungsten. In the examples, SnO has a relatively high oxidation number of the metal in the oxide and therefore has good resistance to oxidation.₂, Ti₄O₇, In₂O₃/ SnO₂(ITO), Ta₂O₅, WO₂, W₁₈O₄₉, CrO₂, And Tl₂O₃including. Examples also include MgO, BaTiO, which has excellent electrochemical stability.₃, TiO₂, ZrO₂, Al₂O₃, And SiO₂including. Other examples include oxides, carbides, nitrides of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W, as well as (oxynitrides, acid carbides, mixed metal compounds (oxides, nitrides). , And carbides), and the like) include the material combinations discussed herein. The protective layer can be non-conductive in bulk, but when used as a thin film, the cell impedance does not increase beyond the permissible value.

The protective layer can include transition metal alloys, aluminum alloys (which can be alloys containing aluminum and one or more transition metals), or other alloys, or alloys such as intermetallic compounds. The alloy can be made more resistant to electrolyte corrosion than the underlying surface. For example, the aluminum current collector can be coated with an aluminum alloy. The aluminum alloy can be an alloy between aluminum and one or more transition metals.

The protective layer can contain non-metal oxides or other non-metal compounds. The protective layer thickness can be a monolayer, nanoscale or less, nanoscale (0.5 nanometer-1 micron) or microscale (1 micron-1 mm).

The electron conductive material can be in the form of a film or particles deposited on the surface of the current collector. The protective layer can include granules, spheres, rods, flakes, or other particle forms. The electron conductive material can have a size distribution in the case of fine particles, or can be substantially monodisperse. The particle size scale can be nanoscale, microscale, or millimeter scale depending on the desired battery size or advantageous properties. The electron conductive particles can also be provided with a coating to prevent or reduce decomposition problems. The particle protective layer or other protective layer may further contain a binder or filler, for example to increase mechanical strength and / or reduce gaps.

The non-conductive or conductive particle core can be coated with a conductive coating of a second conductive material to provide an improved electronically conductive material. The thickness of the thin film on the particles can be substantially smaller than the effective dimensions (eg diameter) of the particles. The film thickness can be selected to allow substantial electron transmission through the coating.

The carbon film or carbon particles can be additionally coated with a thin oxide, nitride, carbide, or tungsten film. For example, carbon coated with metal oxides, metal nitrides, metal carbides, or other transition metals such as tungsten or platinum can be used as a protective layer. For example, TiO₂A thin metal oxide film such as the above can be used as a protective layer.

The protective layer can also be formed by treating the surface of the component. For example, the aluminum surface of the current collector can be treated to induce the formation of a protective layer on the aluminum substrate. For example, surface reaction between aluminum and reactants, or surface alloying can be used to form a protective aluminum alloy coating.

One or more oxidation additives can be placed on the surface of the current collector to reduce the surface potential of the current collector and reduce its corrosion by the molten salt electrolyte. For example, Al₂O₃Alternatively, the NiO thin film can lower the Al oxidation potential by using an aluminum current collector. The protective layer can function by reducing the surface potential by another mechanism or by some combination of mechanisms by preventing contact between the molten salt and the surface.

The protective layer applied to the current collector can be a lithium compound (such as a lithium salt), a lithium alloy (such as a LiAl alloy), an oxide (eg, a transition metal oxide, a lithium oxide, or a mixed oxide). Metal oxides), hydroxides, other transition metal compounds (such as transition metal chalcogenides), compounds that form interlayer compounds with lithium ions (such as titanium disulfide), other sulfides, layers of solid electrolytes, It can include glass materials, crystalline materials, amorphous materials, elastomas, solgels, and the like. Protective layers include polymers such as polyalkylene oxides (such as polyethylene oxide), conductive polymers (such as polypyrrole), polycarbonates, PVDFs, polymer composites (eg with lithium compounds), and the like. be able to. Certain compounds can be classified into one or more of the categories mentioned above.

The improved protective layer described herein can be applied to the surface of one or more components such as a negative electrode, a positive electrode, an electrode collector, or other component of a molten salt battery. The improved protective layer described herein can also include other materials such as conventional binders, as is well known in battery technology.

The electron conductive materials disclosed herein can also be used in combination with other electrolytes (ie, non-molten salt electrolytes) or in other systems as needed.

Therefore, a material that is non-reactive with the molten salt can be coated on a current collector, such as an Al current collector, to improve performance compared to, for example, a carbon coated Al-Rexam sheet. it can. The protective layer can be applied to both the current collector and the positive electrode.

Two or more of the materials or methods described herein can be combined to enhance the corrosion resistance of the current collector.

(Protective layer formation) The protective layer can be formed as a result of surface treatment of the current collector. Surface treatments include physical or chemical deposition processes, chemical bath treatments, acid treatments, galvanic plating (electroplating), metal deposition using organic carriers (such as polymers or composites) followed by heating, solvents, Alternatively, it may be the removal of organic components by other means, or other processes or combinations of processes.

The protective layer can contain oxides of metals different from those found in current collectors, for example an aluminum current collector can have a titanium dioxide protective layer. A metal film can be deposited and then oxidized.

The current collector can be pretreated before the formation of the protective layer, for example by depositing a monolayer (eg, a metal monolayer) or another thin film to enhance the adhesion of the protective layer.

The protective layer can be formed as a reactant between the current collector and the electrolyte, or between the current collector and a suitable additive inside the electrolyte. The protective layer collects electricity using chemical or physical deposition methods such as evaporation, sublimation, physical deposition, chemical deposition, plasma treatment, sputtering, heat treatment, photochemical treatment, monosilane treatment, anodic oxidation, and the like. It can be deposited on the body.

The protective layer can also be a conductive polymer such as polyaniline, polypyrrole, polythiophene, polyvinylidene fluoride, derivatives thereof, or other conductive polymers.

The protective layer can be formed by any thin film coating or deposition process, alloying process, or other process. The protective layer can be used with suitable molten salt electrolytes or other battery components, or can be formed by interaction.

The protective layer can be formed by adding a small amount of aqueous or organic material to the molten salt electrolyte, can be formed by the reaction of the current collector and the components of the molten salt electrolyte, or forms a protective film. It can be formed by treatment of the current collector, such as vapor deposition of components that react with the material of the current collector.

In another embodiment, the electrodes in contact with or in close proximity to the current collector may include components that interact with the current collector to form a protective layer on the current collector. The protective layer can be formed by the reaction between the material in the molten salt electrolyte and the current collector during the initial charge or discharge of the cell.

The protective layer can be in the form of a sheet or can be deposited as particles such as a nanoparticle film. The protective layer can be laid as a slurry containing an inorganic component and an organic component (such as a solvent). The solvent can be removed thermally after the protective layer is formed.

(Molten salt electrolyte) A molten salt electrolyte is an electrolyte that contains one or more salts that are melted (ie, liquid) at the operating temperature of the device using the electrolyte. The molten salt electrolyte can also be described as a molten, non-aqueous electrolyte that does not require an aqueous solvent.

The molten salt electrolytes that can be used in the embodiments of the present invention are granted to US Pat. No. 4,463,071 granted to Giftord, No. 5,552,241 granted to Mamantov et al., No. 5,589,291 granted to Carlin et al., Caja et al. No. 6,326,104, No. 6,365,301 given to Michot, and No. 6,544,691 given to Guidotti.

The molten salt electrolyte of the present invention includes onium such as ammonium, phosphonium, oxonium, sulfonium, amidinium, imidazolium, and pyrazolium, and PF.₆^-, BF₄^-, CF₃SO₃^-, (CF₃SO₂) N^-, (FSO₂)₂N^-And other low basic anions can be included. The molten salt electrolyte of the present invention is also Y⁺N^-(-SO₂Rf²) (-XRf³) Can include Y in the formula⁺Is a cation selected from the group consisting of imidazolium ion, ammonium ion, sulfonium ion, pyridinium, (n) (iso) thiazolyl ion, and (n) (iso) oxazolium ion, which is the cation. Is-CH₂Rf₁Or -OCH₂Rf₁(Rf in the formula is C_1-10Has at least one substituent (which is a polyfluoroalkyl) and has Rf₂And Rf₃Is alone C_1-10Perfluorophenyl or both C_1-10Can consist of perfluoroalkylene, X is -SO₂-Or -CO-, optionally C_1-10C with alkyl or ether bond_1-10Can be replaced with alkyl. In lithium-based batteries, the molten salt electrolyte also includes the following LiPF:₆, LiAsF₆, LiSbF₆, LiBF₄, LiClO₄, LiCF₃SO₃, Li (CF)₃SO₂)₂N, Li (C₂F₅SO₂)₂N, LiC₄F₉SO₃, Li (CF)₃SO₂)₃C, LiBPh₄, LiBOB, and Li (CF)₃SO₂) (CF₃Lithium salts, such as one or more of CO) N, can be included.

(Protective layer formation) The protective layer can be formed as a reactant between the negative electroactive material and the electrolyte, or between the negative electroactive material and a suitable additive inside the electrolyte. The protective layer uses chemical or physical deposition methods such as evaporation, sublimation, physical deposition, chemical deposition, plasma treatment, sputtering, heat treatment, photochemical treatment, monosilane treatment, solgel treatment, anodic oxidation, and the like. Can be deposited on the negative electrode.

The protective layer can be formed by any thin film coating or deposition process, alloying process, or other process. The protective layer can be used with suitable molten salt electrolytes or other battery components, or can be formed by interaction.

The protective layer can be formed by depositing a polymerizable material on the surface of the negative electrode and polymerizing in situ to form the protective layer. The term polymerization as used herein includes a copolymerization process. For example, a solid polymer electrolyte layer can be formed by depositing precursor molecules and then polymerizing with, for example, UV. The precursor molecule can be an organic substance (such as a polymerizable organic molecule) or an inorganic substance (such as a silane derivative).

Protective layer formation can be performed at low temperatures (such as liquid nitrogen temperature) or in anoxic atmosphere so as to suppress the reaction of negative electroactive materials during the formation of the protective layer.

The protective layer can be formed by adding a small amount of aqueous or organic material to the molten salt electrolyte, or can be formed by the reaction of the lithium electrode and the components of the meltable electrolyte, or a component that reacts with Li. It can be formed by treatment of a Li metal electrode, such as depositing to form a protective film. The protective layer can be further (or as an alternative) formed on the positive electrode, eg, using a composition or forming process as described herein. The protective layer can be formed by the reaction between the material in the molten salt electrolyte and the current collector during the initial charge or discharge of the cell.

Therefore, in the embodiment of the present invention, the current collector can be protected against the reaction with the electrolyte by using a protective layer. The protective layer can be in the form of a uniform thin film or can be deposited as particles such as nanoparticle membranes.

(Positive electrode) The positive electrode of the battery (cathode of battery discharge) can be formed from any suitable material. The positive electrode for lithium-ion batteries is lithium cobalt oxide (Li)._XCoO₂), Lithium manganese oxide (Li_XMn₂O₄), Lithium Nickel Oxide (Li_XNiO₂), Other lithium transition metal oxides, lithium metal phosphates, lithium fluoride metal phosphates, and other lithium metal chalcogenides, where the metal can be a transition metal. The lithium content of the positive or negative electrode can vary substantially depending on the battery charge. The positive electrode can further include an electron conductive material and a binder.

(Other electrode elements) The electrode (negative electrode or positive electrode) can further include a non-electrically active material such as an electron conductive material. Non-electroactive materials do not interact substantially with the electrolyte under normal operating conditions.

The electron conductive material can include a carbon-containing material such as graphite. Other exemplary electronically conductive materials include polyaniline or other conductive polymers, carbon fibers, carbon black (such as acetylene black or ketjen black), and cobalt, copper, nickel, other metals, or metals. Includes non-electroactive metals such as compounds (eg, in lithium ion batteries). Electronically conductive materials are in the form of particles (as used herein, the term includes granules, flakes, powders and the like), fibers, meshes, sheets, or other two-dimensional or three-dimensional frameworks. Can be.

The electrode can further include a binder such as polyethylene. The binder can be a fluoropolymer such as polytetrafluoroethylene. The binder may contain one or more inactive materials for the purpose of improving the mechanical properties of the electrode and facilitating the manufacture or processing of the electrode, or for other purposes. Exemplary binder materials are fluoropolymers (polytetrafluoroethylene, polyvinylidene fluoride (PVdF), and the like), polyolefins and derivatives thereof, polyethylene oxides, acrylic polymers (including polymethacrylates), Includes synthetic rubber and similar.

The electrode may further include an ionic conduction protective layer for separating the negative electrode from the region of the electrolyte and / or the electrolyte or one or more other components. Electrodes can further include non-conductive, non-electroactive materials such as inert oxides, polymers, and similar.

(Battery configuration) An exemplary battery includes a positive electrode, a negative electrode, an electrolyte, an electrolyte containing a lithium salt, and first and second current collectors associated with each of the negative and positive electrodes. Examples of the present invention also include a molten salt electrolyte battery, as well as other non-aqueous electrolyte secondary (rechargeable) batteries. An exemplary battery can further include a lead wire and a suitable package such as a closed container that conducts with the first and second current collectors to form electrical contact.

The battery may further include one or more separators installed between the negative electrode and the positive electrode for the purpose of preventing direct contact between the negative electrode and the positive electrode. The separator is optional and the solid electrolyte can provide the same function. The separator can be a porous material, including materials such as polymers (such as polyethylene or polypropylene), sol-gel materials, organically modified silicates, glass, ceramics, glass ceramics, or other materials, such as porous sheets, meshes. , Fibrous mat (cloth), or other form. The separator can be attached to the surface of one or both electrodes.

(Other uses) Other uses of the negative electrode described herein include other alkaline ionized batteries, other rechargeable batteries, other electrochemical devices, and the like.

The above embodiment generally relates to a lithium ion battery having a molten salt electrolyte. However, the techniques described can be adapted to work with other battery technologies, as will be apparent to those skilled in the art of battery technology. For example, it is possible to provide a protective layer that allows other ions to pass through, as needed, for battery technology or for functions by other forms of electrolytes such as organic electrolytes.

The above examples are applicable to various forms of current collectors. The current collector can include aluminum, copper, iron, steel (such as stainless steel), nickel, zinc, conductive polymers, metal polymers (such as metal mylar), and the like.

The current collector can take any physical form, such as a sheet (flat or curved), rod, mesh, porous, granular, two-dimensional or three-dimensional lattice, or any other form.

(Example of battery cycle test) (Example 1) The laminated cell was composed of the following materials. Cathode Cathode active material: LiCoO₂ Electronic Conductive Material: Acetylene Black Binder: PVdF Current Collector: Coated Aluminum Foil Coating Paste: Distributed Acetylene Black and PVdF in NMP anode Anode active material: Li₄Ti₅O₁₂ Electronic Conductive Material: Acetylene Black Binder: PVdF Current collector: Aluminum foil Electrolytes Solvent: EMI-FSI Lithium salt: Li-TFSI (1.0M) Separator: PP porous film Cycle test conditions After adjustment, 1Ccc-cc charge-discharge in 100 cycles

(Example 2) Apply WC powder instead of acetylene black to coat the cathode current collector. Other conditions are the same as in Example 1.<u style="single">Control 1</u>Aluminum foil is used as the cathode current collector. Other conditions are the same as in Example 1.<u style="single">Control 2</u>A nickel blade is used as the cathode current collector. Other conditions are the same as in Example 1.<img id="000002" he="36" wi="139" file="JP5259179B2_D0001.tif" img-format="tif" img-content="drawing" /> Table 1 above shows this result, showing that the capacitance retention is highest when WC is used as the protective layer for the current collector.

The present invention is not limited to the exemplary examples described above. Examples do not limit the scope of the invention. The methods, devices, compositions, and the like described herein are merely exemplary and do not limit the scope of the invention. Changes and other uses here will be recalled to those skilled in the art. The scope of the present invention is defined by the technical scope of the claims.

Patents, patent applications, or publications referred to herein are incorporated herein by reference to the same extent, as each individual document is specifically and individually indicated as incorporated by reference. Is done. Specifically, U.S. Patent Provisional Applications Serial Numbers 60 / 553,443 and 60 / 553,636, both filed on March 16, 2004, and 60 / 571,776, filed May 17, 2004. Is incorporated herein by reference in its entirety.

<figref num="1">It is a figure which shows the structure of the battery which contains the current collector which each has a protective layer.</figref>

Code description

008810, 22 current collector 12 Anode layer 14, 18 electrolyte 16 Separator 20 Cathode layer 24, 26 protective layer