Polytetrafluoroethylene and polyacrylonitrile as active material in an electrode

Abstract

Polytetrafluoroethylene (PTFE) is a common binder in the positive electrode for alkaline metal (including alkaline earth metal) batteries; however, in this invention we claim the use of PTFE as an active material in alkaline batteries, thereby converting the fluorine in the polymer into lithium fluoride. PTFE becomes an active material by partially removing fluorine from the polymer chain, thereby facilitating lithiation thereof. Thermal treatment of PTFE may include mixing with polyacrylonitrile (PAN). We claim that, after heat treatment, the mixture of PTFE and PAN becomes a cathode active material.

Description

[0001] Description

[0002] Technical field

[0003] The scope of the invention pertains to the application of alkali metal batteries, particularly lithium batteries, and corresponding cells and batteries. It also relates to a method for preparing a cathode material for alkaline batteries and energy storage.

[0004] Context

[0005] Lithium-ion batteries are successful energy storage devices used in electronic vehicles and electrical products, as well as renewable sources. However, with the growing demand for higher specific capacity, conversion batteries are promising candidates for increasing the amount of energy storage in the positive electrode (hereinafter referred to as the cathode). Examples of conversion cathodes are lithium-air batteries, lithium-sulfur batteries, and lithium-fluoride batteries, such as carbon monofluoride (CF). X, where 0 <X<4). Enquanto as baterias de lítio- ar e de lítio-enxofre diminuem rapidamente a capacidade específica devido à presença de água ou ao transporte do polissulfeto no eletrólito, o monofluoreto de carbono tem uma baixa quantidade de flúor e, consequentemente, uma capacidade específica relativamente baixa.

[0006] PTFE has a high concentration of fluorine (-CF2-), is thermodynamically and chemically stable, is an insulator, and is commonly used as a binding agent in positive electrodes. During cathode paste mixing, the binder is mixed with an electrically conductive material (e.g., super P carbon) and the active material. For example, in lithium-sulfur batteries, sulfur is the active material in a carbon host material. Therefore, the binder, the electrically conductive material, and the active material are all components of the positive electrode. Because PTFE does not conduct electrons, the material cannot be reduced by lithium fluoride, which produces lithium. Therefore, chemical treatment is required to activate PTFE as a cathode material for alkaline batteries.

[0007] Disclosure of the invention

[0008] This invention is a cathode material used for alkali metal cells, e.g., lithium, sodium, and magnesium batteries, and can be classified as metal-fluorine batteries, e.g., lithium-fluorine, sodium-fluorine, and magnesium-fluorine.

[0009] An alkali metal cell can be defined as an electrochemical cell, which includes a battery cell or a rechargeable battery cell, that electrochemically charges and discharges alkali metals. Examples of alkaline / alkaline cells are lithium, sodium, and / or magnesium cells. An alkali metal-fluorine cell can be understood as an electrotechnical cell that reacts electrochemically with alkali ions, with fluorine participating in the reaction. For example, lithium, sodium, or magnesium react with fluorine. The alkali metal-fluorine can be, for example, lithium-fluorine, sodium-fluorine, and / or magnesium-fluorine.

[0010] Fluoride can be understood as a chemical compound that includes negatively charged fluorine, for example, F". The discharge of the cell may include at least one alkali metal and / or at least one metal ion. After discharge, at least one metal may be reduced to the elemental or metallic form. In particular, the active material, in the charged state, includes at least one metal fluoride and, in the discharge state, includes at least one metal ion or at least one reduced metal that can contribute to the discharge, and at least one metal in the oxidized state can increase electrical conductivity due to conductive or semiconductor properties.

[0011] At least one active material of the positive electrode (cathode) may contain fluorine and / or a fluorinated polymer. For example, the at least one active material comprises or may consist of a covalently bonded or ionic polymer of fluorine. The active material of the cathode may include fluorinated polymers that react electrochemically with alkali metals, in particular, polytetrafluoroethylene with fluorine partially removed from the polymer structure, PTFE, perfluoropolyether, and / or fluorinated polyacetylene.

[0012] At least one of the cathode active materials may include or consist of an electronically conductive polymer optionally blended with a fluorinated polymer. The electronically conductive polymer may incorporate cyclized polyacrylonitrile (cPAN), polypyrrole, polyparaphenylene, and / or polyacetylene, and the electronically conductive polymer may be fluorinated or partially fluorinated, e.g., fluorinated polyacrylonitrile (FPAN), fluorinated polypyrrole, fluorinated polyparaphenylene, and / or fluorinated polyacetylene. A fluorinated polymer may be a polymer with fluorine covalently or ionically bonded to the polymer. For example, the electrically conductive polymer may provide electrons to induce alkali metal reactions with fluorine in the polymer backbone. For example, cPAN in a PTFE matrix, in the discharge state, the alkali metal can be ionically bonded to the polymer and / or fluorine, while in the charge state, the polymer and / or fluorine can be reduced.

[0013] In the context of cathode active material, the active material during battery discharge will capture electrons from the circuit and react with alkali metals, for example, lithium cobalt oxide, lithium nickel oxide, sulfurized polyacrylonitrile and / or sulfur.

[0014] In the context of fluorinated polymers and electrically conductive polymers, the fluorinated polymer may be wholly or partially composed of an electrically conductive polymer. In particular, heat treatment of PAN at temperatures above 300°C, primarily in the range of 300°C to 650°C, forms a conjugated polymer system in which a nitrogen-carbon pair forms an aromatic structure and, consequently, an electronically conductive polymer. Furthermore, heat treatment of PAN releases gases containing hydrogen, ammonia, hydrocyanic acid, or other gases.

[0015] Polymer defluorination can be understood as the chemical reaction of a fluorinated polymer that reduces the amount of fluorine. For example, PTFE can have its fluorine partially or completely removed by gaseous reaction. Particularly in PTFE, defluorination is achieved by heat treatment at temperatures above 200°C, especially in the range of 200°C to 650°C, using gases such as hydrogen gas, ammonia, and / or hydrocyanic acid. Defluorination of PTFE tends to form a sigma-pi conjugated structure in the polymer, tending to form a fluorinated polymer structure.

[0016] Alternatively, or in addition, the defluorination of a polymer may be encompassed by PAN. For example, PAN incorporated with at least one fluorinated polymer, e.g., PTFE, perfluoropolyether, and / or fluorinated polyacetylene, may induce defluorination through heat treatment at temperatures above 200°C, especially in the range of 200°C to 800°C. In this context, particularly the PAN embodiment and at least PTFE (Teflon), hereinafter referred to as PANflon, is heat treated above 200°C, especially in the range of 200°C to 800°C. In this context, the heat treatment may take less than 24 hours, especially less than 6 hours. Optionally, the heat treatment procedure may be carried out in an inert gas, such as argon and / or nitrogen. Mechanical processes that induce heat, for example, a ball mill, may also be considered heat treatment.

[0017] PANflon can be understood as PTFE incorporated or not with at least PAN and terminally treated with gases and / or with at least PAN, as mentioned above. Pure PTFE with some of the fluorine removed from the PTFE can also be understood as PANflon. In this context, PANflon is the mixture of PAN in PTFE in a proportion of 0% to 100%.

[0018] In this context, the cathode active material may be incorporated with at least PANflon. Alternatively, or in addition, the cathode material may comprise at least the cathode active material and / or an electrically conductive material, e.g., carbon structures such as super P carbon and / or carbon nanotubes. Therefore, the cathode active material may alternatively be surrounded by an electrically conductive material.

[0019] Within the scope of the active material modality, in the first step of the method, PTFE is defluorinated. This method is performed by chemical reaction with at least one gas, such as hydrogen, and / or other gases, such as ammonia. In this context, PTFE can be defluorinated through a chemical reaction with at least one other material, such as polyacrylonitrile. In this context, PAN releases gas containing hydrogen and ammonia during heat treatment, while simultaneously behaving as an electrically semiconductor material and / or potentially as a cathode active material together with PTFE.

[0020] The polymer precursor may include an inherently electrically conductive polymer, such as polyaniline (PAni). Additionally, the polymer precursor, such as polyacrylonitrile (PAN), can be adapted to form an inherently electrically conductive polymer, specifically cyclized and dehydrogenated polyacrylonitrile (cPAN) or polyaniline (PAni). The polymer precursor may be reacted into a corresponding polymer after heat treatment, for example, cPAN. The polymers in the cathode material may include or be a homopolymer and / or a copolymer.

[0021] The invention also relates to a cathode material, in particular at least the cathode active material, and may optionally include additives, conductive material, and / or binder. In this context, another material may be incorporated into the cathode active material, in particular an electrolyte, for example, a polymer electrolyte for conducting alkali / alkali ions and / or a solid-state electrolyte.

[0022] Within the scope of a specific embodiment, the method further includes mixing at least one electrically conductive material, specifically selected from the group consisting of graphite, carbon fibers, and carbon nanotubes. In another specific embodiment, the method further includes mixing at least one binding agent, e.g., polyvinylidene fluoride and / or PTFE. In this context, PTFE has not necessarily been treated or activated as the cathode active material. The binding agent may be mixed with the composite material and / or the electrically conductive material. The order in which the composite cathode material is mixed may be different; e.g., the cathode active material, the electrically conductive material, and / or the binding agent may be mixed optionally and in different orders.Within the scope of another specific embodiment, in the method, cathode active materials, e.g., PANflon, may be optionally mixed with other cathode active materials, e.g., sulfur and / or lithium cobalt oxide.

[0023] Within the scope of another specific embodiment, in the method, the cathode active materials may be mixed from 0.1% to 95% by weight with electrically conductive additives. Also, in the method, another specific incorporation of 0.1% to 99% by weight with binding agents is mixed. In addition, in the method, another specific embodiment of 0.1% to 99.5% by weight with at least one other cathode active material, for example, sulfur, sulfurized polyacrylonitrile, and / or lithium cobalt oxide.

[0024] The cathode material, especially for preparing the cathode material paste, may be coated with at least one solvent, e.g., N-Methyl-2-pyrrolidone, and spread onto a collector, e.g., by a doctor blade, to transport the material onto a collector such as aluminum foil. Preferably, the solvent is removed after treatment, especially by drying. Alternatively, the cathode material, especially for drying methods, may be compressed to produce a solid material for cathode cells.

[0025] Subsequently, the cathode material system can undergo additional stamping or cutting to produce multiple cathodes. Cathode material units can be installed on the alkali metal anode in the form of plates or sheets.

[0026] The present invention relates to cathode materials for alkaline batteries, particularly lithium, sodium, and / or magnesium anodes, e.g., lithium metal foil or plate. Within the scope of another specific embodiment, the alkaline battery particularly includes at least one electrolytic solution agent and at least one conductive salt, and / or at least one solid electrolyte.

[0027] The electrolyte solution agent may belong to the group consisting of ethers, carbonates, lactones, and ionic liquids. The electrolyte solution may include 1,3-dioxolane (DOL), ethylene carbonate (EC), diethylene carbonate (DEC), dimethoxyethane (DME), dimethyl carbonate (DMC), propylene (PC), and / or a combination thereof. The conductive salt may consist of alkaline salts, for example, lithium salts, which include bis(trifluoromethylsulfonyl)imide, hexafluorophosphate, tetrafluoroborate, trifluoromethanesulfonate, chlorate, oxalate-borate, nitrate, hexafluoroarsenate, and combinations thereof. The solid-state electrolyte may be composed, for example, of at least Li7La3Zr20i2, Li6.4La3Zr1.4Tao.6O12, Lii.4Alo.4Tii.6(P04)3, Lii.5Alo.5Gei.5(P04)3 and / or poly(ethylene oxide)-based electrolytes.

[0028] Another subject matter related to the present invention is its application as an energy storage device, which may be a mobile or stationary energy storage device, including alkaline / alkaline batteries. In this context, the energy storage may, for example, be energy storage for a cell phone, electric vehicle, laptop, power tools, portable computers, or greenhouse power supplies.

[0029] In this context of the present invention, Figure 1 shows the characterization of PANflon after heat treatment. Figure 2 shows a schematic representation of the defective PTFE structure, in which two carbon atoms have one less fluorine atom in the polymer structure. Figure 3 is the characterization of the battery's charge and discharge. Figure 4 is the cyclic voltammetry of PANflon. Figure 5 is a demonstration of the PANflon cathode connecting three LEDs.

Claims

MODIFIED CLAIMS Received by the International Bureau on November 17, 2024 (17.11.2024) 1. Characterized by a cathode material for an alkali metal battery, comprising at least one cathode active material that contains defective or chemically modified polytetrafluoroethylene, with partially removed fluorine.

2. Characterized by a cathode material for an alkali metal / alkali battery, comprising at least one cathode active material containing PANflon, therefore a mixture of polytetrafluoroethylene and polyacrylonitrile.

3. Characterized by the cathodic material of claim 1, wherein at least one cathodic active material is surrounded by at least one more material, including more cathodic active materials and / or conductive materials and / or binder material.

4. Characterized by the cathodic material of claim 2, wherein the at least one cathodic active material is surrounded by at least more than one material, including cathodic active materials and / or electrically conductive materials and / or binder materials.

5. Characterized by a method for preparing a cathode material for an alkaline cell, including at least a mixture of polytetrafluoroethylene and polyacrylonitrile, or pure polytetrafluoroethylene.

6. Characterized by the method described in claim 5, in which the PANflon is prepared and reacted at a temperature above 200 °C.

7. Characterized by the method described in claim 5, in which the PANflon is defluorinated with gases, such as hydrogen and / or ammonia.

8. Characterized by the method described in claim 5, claim 6 and / or claim 7, wherein at least one PANflon is mixed with an electrically conductive additive, including at least one of the following elements: graphite, carbon fiber, super-P carbon, carbon nanotubes and / or another electrically conductive additive.

9. Characterized by the method described in claim 5, claim 6 and / or claim 7, wherein at least one PANflon is mixed with a binding agent that includes at least one polyvinylidene fluoride, polytetrafluoroethylene and / or another binding agent.

10. Characterized by an alkaline battery, comprising a negative electrode (anode) containing alkali metal and a positive electrode (cathode), the cathode including at least PANflon, and including an electrolyte composed of at least one electrolytic solution agent and / or solid state electrolyte and / or with a conductive salt.

11. Characterized by a method of mixing polyacrylonitrile and polytetrafluoroethylene, using solvent or mechanical methods, thus preparing PANflon for heat treatment, as described in claim 6.

12. Characterized by a method of mixing polyacrylonitrile and polytetrafluoroethylene, using mechanical methods, for example, a grinding machine, thus preparing the PANflon for heat treatment, as described in claim 6.

13. Characterized by a battery cited in claim 10 being part of an energy storage. [0001]Declaration under Article 19(1) [0002]First, I would like to thank those responsible for the report and the excellent work presented. I would like to highlight the inventive features of this submitted patent. The invention is characterized by the use of defective polytetrafluoroethylene (PTFE) as the active material in the cathode of alkaline batteries, e.g., lithium batteries.[0003]I would like to emphasize that simple heat treatment of PTFE is not capable of modifying its chemical structure up to 550°C, when the polymer degrades. Therefore, simple heat treatment of PTFE is not capable of transforming it into an active cathode material. In this case, PTFE can only serve as an adhesive. To activate PTFE for batteries, and thus to create defective PTFE with a change in its chemical structure, the presence of a reagent is necessary. In this case, this reagent can be polyacrylonitrile (PAN), which during heat treatment releases gases such as hydrogen and ammonia, which react with PTFE, producing, among other things, hydrogen fluoride. Therefore, it is possible, as already stated in the patent description, to use other products besides PAN to activate PTFE, such as coke or hydrogen gas. However, the use of PAN offers other advantages, as it presents conductivity and also activity during the battery charging and discharging processes. [0004]Therefore, I would like to emphasize again that the defective PTFE-containing cathode is an invention of the present patent. And I would like to inform you that the descriptive part of the patent has been modified to better exemplify this. However, no claim has been changed. [0005]Thank you for your attention, Samuel Bertolini da Silva Oliveira

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