Electrode precursor composition

Abstract

Disclosed is an electrode precursor composition suitable for preparing a gel electrode, the composition comprising an organic solvent, an alkali metal salt, an electrically insulating polymer, and a redox-active organic component, where the redox-active organic component is present at a smaller volume fraction than the electrically insulating polymer. The redox active organic component may be present in the electrode precursor composition in an amount of between 1 and 20 vol% based on the total volume of the electrode precursor composition. The redox-active organic component may be present in the electrode precursor composition in an amount of up to 8% by volume based on the total volume of the electrode precursor composition. The redox active organic component may be a redox active polymer.

Description

Technical Field

[0001] The present invention relates to an electrode precursor composition for an alkali metal ion secondary battery cell, an electrode, a battery cell and an energy storage device made from the precursor composition, and a method for preparing an electrode for an alkali metal ion secondary battery cell. Background Art

[0002] Lithium-ion secondary battery cells are the leading battery technology used today in applications ranging from small personal devices to electric vehicles. Lithium-ion batteries are favored for their high energy density and long cycle life. They contain multiple lithium-ion secondary battery cells.

[0003] Conventional lithium-ion battery components such as electrodes are made by a solvent casting process that uses sacrificial solvents. This is an energy-expensive step, so there is a need for processes that avoid the use of sacrificial solvents.

[0004] One way to avoid the use of sacrificial solvents is to prepare gel electrodes. These electrodes can be formed from a composition that is prepared by mixing the necessary components, such as an electrochemically active material, a polymer (usually an electrically insulating polymer), and a solvent or liquid electrolyte, and then processing the composition, such as extrusion, to form an electrode.

[0005] The use of gels in the preparation of electrodes using this processing must balance at least two opposing requirements. On the one hand, the electrode must have a high enough energy density to be practical to use. To this end, a higher solids content (higher content of electrochemically active material) is desirable. On the other hand, the gel must be soft enough to be handled to form an electrode. To this end, a lower solids content (lower content of electrochemically active material) is desirable so that the material exhibits sufficient fluidity to be handleable.

[0006] There is a need for electrode precursor compositions that meet the above criteria. Summary of the invention

[0007] In general, the present inventors propose to solve the above problems by utilizing redox-active organic molecules as part of the electrode precursor composition. In particular, the present inventors generally propose to replace a portion of the conventional electrically insulating polymer with the redox-active organic molecules. Since the electrically insulating polymer is a structural component that is generally swellable, the volume fraction of the redox-active organic component should be less than the volume fraction of the electrically insulating polymer.

[0008] In this way, the inventors believe that the energy density of the gel electrode can be increased compared to a corresponding gel electrode without a redox-active organic component. For example, if the electrode precursor composition requires a reduced amount of electrochemically active material for processability, then the presence of the redox-active organic component can at least partially compensate for the expected corresponding decrease in energy density. Similarly, if the electrode precursor composition does not require a reduced amount of electrochemically active material for processability, then the use of the redox-active organic component can increase the capacity and result in an electrode having a higher energy density than expected for a gel electrode without a redox-active organic component. The present invention is based on this discovery.

[0009] The use of redox-active polymers in electrodes is known, for example, as discussed by Poizot et al. (Chem. Rev. 2020, 120, 14, 6490-6557). For example, Duc et al. (ACS Appl. Polym. Mater. 2020, 2, 6, 2366-2379) disclose a long-range electron conductor based on PEO and PEDOT:PSS. The authors report that the extrusion of these blends introduces phase separation phenomena, requiring acidic post-treatment to restore electronic conductivity. US 9,722,249 B2 and DE102012022976 A1 disclose a composition comprising a complex of polythiophene and a polyanion, at least one lithium-containing compound and at least one solvent, wherein the composition comprises less than 1g of a material comprising elemental carbon based on 1g of polythiophene, or does not comprise a material comprising elemental carbon at all. JP 2004-158286 A discloses an electrode comprising PEDOT and PVDF as a binder produced by molding. JP 2011-100594 A discloses a composition comprising: a conductive polymer formed by polymerizing ethylenedioxythiophene or a derivative in the presence of at least one polymer sulfonic acid selected from polystyrene sulfonic acid, sulfonated polyester and phenolsulfonic acid novolac resin, the novolac resin containing the polymer sulfonic acid as a dopant; and an organic solvent and a carbonaceous conductive material, and an electrode mixture composition further comprising a binder and an electrode active material. CN 110429279A discloses an organic positive electrode material formed by copolymerization of a ruthenium or osmium derivative as a comonomer, comprising a conjugated aromatic fused ring as an electrochemical redox site.

[0010] However, these documents do not describe the concept of increasing the energy density of gel electrodes by using redox-active organic molecules at a lower volume fraction than the electrically insulating polymer.

[0011] The overall proposition of the present invention is therefore to provide a processable gel electrode precursor composition comprising a redox active organic component, an electrically insulating polymer, an alkali metal salt and an organic solvent. The composition can then be combined with an electrochemically active material and a conductive additive before further processing to form an electrode. Using this general process, the inventors have found that the electrode precursor composition is highly processable while also forming an electrode with increased energy density.

[0012] A first aspect of the present invention relates to an electrode precursor composition suitable for preparing a gel electrode, the composition comprising an organic solvent, an alkali metal salt, an electrically insulating polymer and a redox active organic component, wherein the redox active organic component is present in a smaller volume fraction than the electrically insulating polymer.

[0013] The resulting electrode precursor composition generally comprises a polymer gel matrix phase. As such, the electrode precursor composition generally has gel-like properties and can be processed into a thin film electrode.

[0014] Generally, it is difficult to obtain dense electrodes with more than 70% volume solids content, which leads to limitations in electrode energy density. Advantageously, the use of organic moieties as processing aids and active materials as a solution to this problem, as disclosed in this application, has not been described before.

[0015] According to a second aspect, the present invention relates to a method for preparing an electrode for an alkali metal ion secondary battery cell, the method comprising:

[0016] A providing step comprises providing an electrode precursor composition according to the first aspect; and

[0017] The processing step includes processing the electrode precursor composition to form an electrode.

[0018] Further aspects relate to electrodes for alkali metal ion secondary batteries prepared from the electrode precursor composition or method according to the invention, electrochemical secondary batteries such as alkali metal ion secondary batteries comprising electrodes according to the invention, electrochemical energy storage devices comprising electrochemical batteries according to the invention, and the use of redox-active organic components in a method for preparing electrodes for alkali metal ion secondary batteries using a high temperature treatment step. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagrams of theoretical electrodes with (a), (b) ideal filling of electrochemically active materials and (c), (d) non-ideal filling of electrochemically active materials. DETAILED DESCRIPTION

[0020] The preferred and / or optional features of the present invention will now be described. Unless the context otherwise requires, any aspect of the present invention may be combined with any other aspect of the present invention. Unless the context otherwise requires, any preferred and / or optional features of any aspect may be combined with any aspect of the present invention individually or in combination.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present disclosure belongs. Methods and materials for use in the present disclosure are described herein; other suitable methods and materials known in the art may also be used. The materials, methods, and examples are illustrative only and not restrictive. All publications, patent applications, patents, and other references mentioned herein are incorporated herein by reference in their entirety. In the event of a conflict, the present specification (including definitions) shall prevail.

[0022] The methods described herein generally employ typical laboratory ambient temperature, usually between 20 and 30°C, preferably about 25°C, at atmospheric pressure, unless different conditions are defined herein or are more general for, e.g., a particular apparatus.

[0023] The present invention generally describes the use of redox-active organic components in electrode precursor compositions. Redox-active organic components include molecules that can undergo reversible oxidation and reduction processes. Redox-active organic components can include one or more of redox-active organic small molecules and / or redox-active organic polymers. Depending on the nature of the redox-active organic component, particularly the polymer, a dopant can be used to achieve a practical useful effect.

[0024] It should be understood that the redox active organic component should be present in the electrode precursor composition in an amount sufficient to achieve the desired increase in energy density. Thus, in some embodiments, the redox active organic component is present in the electrode precursor composition in an amount of at least 1 volume %, such as at least 2 volume %, at least 3 volume %, or at least 5 volume %, based on the total volume of the electrode precursor composition.

[0025] In addition, the redox-active organic component is present in the electrode precursor composition in a smaller volume fraction than the electronically insulating polymer. Thus, in some embodiments, the redox-active organic component is present in the electrode precursor composition in an amount up to 20 volume %, such as up to 18 volume %, up to 15 volume %, up to 10 volume %, or up to 8 volume %, based on the total volume of the electrode precursor composition.

[0026] Therefore, in some embodiments, the redox-active organic component is present in the electrode precursor composition in an amount between 1 and 20 volume %, based on the total volume of the electrode precursor composition. Other combinations of the above values ​​can be combined to form a suitable range, such as between 2 and 18 volume %, between 2 and 10 volume %, or between 5 and 8 volume %.

[0027] Note that the total volume % of all ingredients in the electrode precursor composition is 100 volume %.

[0028] Redox-active organic components can undergo reversible oxidation and reduction processes. Therefore, they represent a particularly useful class of components because they have the ability to store charge. Therefore, compensation or improvement of the energy density of the electrode is achieved using redox-active organic components.

[0029] Figure 1 Used to schematically illustrate how the energy density of an electrode can be increased compared to a corresponding electrode without a redox-active organic component. Figure 1 In (a), a nearly ideal electrode is shown, with nearly complete filling of electrochemically active particles.

[0030] In theory, this has >73% solids filling (close to ideal), with about 68% volume of electrochemically active material (black circles), with the intervening space filled with gel (white). This can result in about 210 mAhg -1 The active material capacity is about 183 mAhg -1 The same electrode as (a) is shown in (b), but the redox-active conductive component (grey) is contained in the gel in the pores, which can be represented by, for example, PhenQ (1,10-phenanthroline-5,6-dione, a cationic molecule, which will be discussed further in this article). When other values ​​remain unchanged, the electrode capacity can be increased to 196 mAhg -1 .

[0031] A similar trend can be seen at lower filling efficiencies. Figure 1 (c) shows a non-ideal electrode, such as that more typically achieved by an extrusion process. This electrode has <73% solid filling and incomplete filling of electrochemically active particles of about 63% volume (black circles), with the intervening spaces filled with gel (white). This can result in a charge of about 210 mAhg -1 Active material capacity and 177mAhg -1 The same electrode as (c) is shown in (d), but the gel in the pores contains a redox-active conductive component, such as 1,8PhenQ (grey). When other values ​​remain unchanged, the electrode capacity can be increased to 196 mAhg -1. Thus, it can be seen that replacing some of the gel polymer with a redox-active organic component can slightly compensate for the loss of volumetric capacity and increase the electrode capacity. As a result, higher energies can be achieved. This is especially important for non-ideal examples, which already have a lower energy density.

[0032] In each of (a) to (d), other components such as conductive additives and electrically insulating polymers are not shown.

[0033] At the cathode, charge is stored by anion insertion. That is, compensation of energy density is achieved by anion doping reactions. The skilled person will be familiar with electrochemical storage mechanisms using redox-active organics; in this regard, further reference is made to Figure 9 and Table 1 of Poizot et al. (Chem. Rev. 2020, 120, 14, 6490-6557). Figure 9a of Poizot et al. shows an example of anion compensation for a p-type system, where a polymer containing conjugated double bonds (shown as ) can be used with anion A - Reversibly doped. The process is shown as two reversible doping steps (n=2). Each doping step involves the polymer losing one electron.

[0034] Thus, in embodiments using redox-active components that undergo anion doping reactions, such as redox-active polymers, the gel electrode can contain up to 8 vol% of the redox-active polymer, e.g., up to 7 vol%, up to 6 vol%, or up to 5 vol% of the redox-active polymer to avoid effective consumption of anions, thereby maintaining battery performance.

[0035] Many redox-active organic molecules (i.e., both small molecules and polymers) are known to technicians. They can be used in the present invention alone or in combination. As an example only and not as a limitation, the redox-active organic molecules suitable for the present invention include one or more of the following: poly (3,4-ethylenedioxythiophene) (PEDOT), polyaniline (PANI), polypyrrole (PPy), and their derivatives and doped derivatives, such as poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate (PEDOT-PSS). Further examples include polyacetylene, coronene, polydopamine, 4,5-PhenQ and others described in Table 2 of Poizot et al. (Chem.Rev.2020,120,14,6490-6557), all of which are incorporated herein by reference.

[0036] In some embodiments, the redox-active organic molecules used in the present invention have a capacity of about 100 mAhg -1 The minimum redox activity is about 2.5 V. In some embodiments, the redox activity is higher, such as about 150 mAhg-1 or about 200mAhg -1 No particular upper limit is envisioned, as higher redox activities are generally desired.

[0037] Redox activity can be measured using suitable methods known in the art.

[0038] The electrode precursor composition of the present invention also comprises an electrically insulating polymer. These polymers are not essentially conductive polymers and are non-conductive or have negligible conductivity. Typically, these polymers are substantially free of conjugated double bonds that allow electrons to flow through the polymer backbone.

[0039] The electrically insulating polymer used for the present electrode precursor composition is a polymer commonly used to prepare a gel electrode. They are generally swellable. They can be used alone or in combination in the present invention. Many are known to the technician. By way of example only and not limitation, the electrically insulating polymer suitable for the present invention includes one or more of the following: polyvinylidene fluoride (PVDF), polyethylene oxide (PEO), polymethyl methacrylate (PMMA) and polyacrylonitrile.

[0040] In some embodiments, the electrically insulating polymer is present in the electrode precursor composition in an amount of at least 5 volume %, such as at least 7 volume %, at least 10 volume %, or at least 15 volume %, based on the total volume of the electrode precursor composition.

[0041] In some embodiments, the electrically insulating polymer is present in the electrode precursor composition in an amount up to 30 volume %, such as up to 28 volume %, up to 25 volume %, or up to 20 volume %, based on the total volume of the electrode precursor composition.

[0042] Therefore, in some embodiments, the electrically insulating polymer is present in the electrode precursor composition in an amount between 5 and 30 volume %, based on the total volume of the electrode precursor composition. Other combinations of the above values ​​can be combined to form a suitable range, such as between 5 and 28 volume %, between 7 and 25 volume %, or between 10 and 20 volume %.

[0043] The electrode precursor composition of the present invention comprises at least one alkali metal salt.

[0044] The alkali metal of the at least one alkali metal salt can be any suitable alkali metal (Group I of the periodic table of elements). Typically, it can be lithium, sodium and potassium. In some embodiments, the at least one alkali metal of the alkali metal salt is lithium, which may be preferred in all embodiments of the present invention.

[0045] The anion of the at least one alkali metal salt may be any suitable anion. Typical anions are known to the skilled person and may be selected based on the nature of the alkali metal. In some embodiments, when the at least one alkali metal is lithium, the anion of the or each alkali metal salt is independently selected from: lithium borate salts, lithium imide salts, and lithium imidazole salts, or comprises a halogen, such as fluorine. Examples include BF 4 - ,PF 6 - ,TFSI - ,FSI - and TDI - .

[0046] Thus, in some embodiments, the at least one alkali metal salt comprises one or more of the following: lithium bis(oxalate)borate, lithium tetrafluoroborate, lithium difluoro(oxalate)borate (LiDFOB), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium 2-trifluoromethyl-4,5-dicyanoimidazole (LiTDI), and lithium hexafluorophosphate (LiPF). 6 ).

[0047] In some embodiments, the at least one alkali metal salt includes one or more of LiFSI, LiDFOB, and LiTDI.

[0048] In some particularly useful embodiments, the at least one alkali metal salt comprises LiBF 4 、LiPF 6 , LiTFSI, LiFSI and LiTDI.

[0049] According to the present invention, one or more alkali metal salts may be used. Typically, but not exclusively, when more than one alkali metal salt is used, they share a common alkali metal cation. Typically, but not exclusively, when more than one salt is present, they are each a lithium salt.

[0050] The organic solvent used in the present invention is an organic solvent generally used for manufacturing electrodes of alkali metal secondary batteries. The organic solvent should be appropriately miscible with the polymer and the redox-active organic component of the electrode precursor composition, for example, to form a solution.

[0051] In some embodiments, the organic solvent is non-aqueous. In some embodiments, the solvent includes one or more cyclic or linear carbonates, ethers or nitrile compounds. In some embodiments, the solvent includes one or more cyclic or linear carbonate compounds.

[0052] In certain embodiments, one or more linear or cyclic carbonate compounds include one or more cyclic carbonate compounds. In certain embodiments, the solvent includes one or more of: ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl carbonate-methyl ester, butylene carbonate, vinylene carbonate, fluoroethylene carbonate, fluoropropylene carbonate and gamma-butyrolactone.

[0053] In some embodiments, the alkali metal salt and the organic solvent together are present in an amount of at least 1 vol %, such as at least 5 vol %, at least 10 vol %, or at least 15 vol %, based on the total volume of the electrode precursor composition.

[0054] In some embodiments, the alkali metal salt and the organic solvent are present in an amount up to 50 volume %, such as up to 45 volume %, up to 35 volume %, or up to 25 volume %, based on the total volume of the electrode precursor composition.

[0055] Therefore, in some embodiments, based on the total volume of the electrode precursor composition, the alkali metal salt and the organic solvent are present in an amount between 1 and 50 volume %. Other combinations of the above values ​​can be combined to form a suitable range, such as between 5 and 45 volume %, between 5 and 35 volume % or between 10 and 25 volume %.

[0056] The skilled artisan will be aware of a large number of possible electrochemically active materials, including cathode active materials (also known as positive electrode active materials) and anode active materials (also known as negative electrode active materials), which may be used in the present invention.

[0057] The electrochemically active material is a particulate material, ie a material consisting of a plurality of discrete particles. The particles may include primary particles and / or secondary particles formed by the aggregation of a plurality of primary particles.

[0058] In some embodiments, the electrochemically active material is a positive electrode active material. That is, the electrode functions as a cathode.

[0059] In some embodiments, the positive electrode active material is a lithium transition metal oxide material. In some embodiments, the positive electrode active material is a lithium transition metal oxide material, or a lithium transition metal phosphate material, or a lithium transition metal sulfide material. These respectively contain mixed metal oxides, phosphates or sulfides of lithium and one or more transition metals, optionally further containing one or more other non-transition metals. In some embodiments, the positive electrode active material is a lithium transition metal oxide, phosphate or sulfide material containing lithium and one or more transition metals selected from nickel, cobalt and manganese. In some embodiments, the positive electrode active material is a lithium transition metal oxide material, which contains a mixed metal oxide of lithium and one or more transition metals, optionally further containing one or more other non-transition metals. In some embodiments, the positive electrode active material is selected from one or more of the following: lithium cobalt oxide (LCO), lithium manganese oxide (LMO), lithium nickel cobalt oxide (NCO), aluminum-doped lithium nickel cobalt oxide (NCA), lithium nickel manganese cobalt oxide (NMC), lithium nickel oxide (LNO), lithium nickel manganese oxide (LNMO), lithium iron phosphate (LFP), lithium manganese iron phosphate (LFP) and lithium nickel vanadate (LNV). In some embodiments, the positive electrode active material is lithium nickel manganese cobalt oxide (NMC), optionally doped with another metal, such as aluminum.

[0060] Such electrochemically active materials are commercially available or can be made by methods known to those skilled in the art, for example by precipitation of a mixed metal hydroxide intermediate from a reaction mixture containing various precursor metal salts, followed by calcination to form a mixed metal oxide, and optionally lithiation to incorporate lithium into the oxide.

[0061] The electrochemically active material may be undoped or uncoated, or may include one or more dopants and / or coatings. For example, the electrochemically active material may be doped with a small amount of one or more metallic elements. The electrochemically active material may include a carbon coating on the surface of the material particles.

[0062] In some embodiments, the electrochemically active material is present in an amount of at least 55 volume %, e.g., at least 56 volume %, at least 57 volume %, at least 58 volume %, at least 59 volume %, at least 60 volume %, at least 61 volume %, or at least 62 volume %, based on the total volume of the electrode precursor composition.

[0063] In some embodiments, the electrochemically active material is present in an amount up to 75 volume %, e.g., up to 74 volume %, up to 73 volume %, up to 72 volume %, up to 71 volume %, up to 70 volume %, up to 69 volume %, or up to 68 volume %, based on the total volume of the electrode precursor composition.

[0064] In some embodiments, the electrochemically active material is present in an amount of 55 to 75 volume %, based on the total volume of the electrode precursor composition. Other combinations of the above values ​​can be combined to form a suitable range, such as 55 to 70 volume %, 55 to 69 volume %, 55 to 68 volume %, 58 to 68 volume % or 60 to 68 volume %.

[0065] In some embodiments, the electrochemically active material comprises 62 to 75 volume %, eg, 62 to 70 volume %, 62 to 69 volume %, 62 to 68 volume %, or 62 to 69 volume % of the electrode precursor composition.

[0066] In some embodiments, the electrochemically active material is present in an amount of 62 to 75 volume %, such as 60 to 75 volume %, 60 to 72 volume %, 60 to 70 volume %, or 60 to 68 volume % of the electrode precursor composition.

[0067] In some embodiments, the electrode precursor composition further comprises a conductive additive, preferably conductive carbon. The conductive additive may be a particle.

[0068] In some embodiments, the conductive additive comprises one or more of carbon black, carbon nanotubes, graphene and graphite or consists thereof. In some embodiments, the conductive additive comprises carbon black or graphite, preferably carbon black, or consists thereof. Examples of commercially available carbon black include Ketjen Black and Super C65.

[0069] In some embodiments, the conductive additive is present in an amount of at least 1 volume %, such as at least 2 volume %, at least 3 volume %, or at least 4 volume %, based on the total volume of the precursor composition.

[0070] In some embodiments, the conductive additive is present in an amount up to 10 volume %, such as up to 9 volume %, up to 8 volume %, or up to 7 volume %, based on the total volume of the electrode precursor composition.

[0071] Therefore, in some embodiments, the conductive additive is present in an amount between 1 and 10 volume %, based on the total volume of the electrode precursor composition. Other combinations of the above values ​​can be combined to form a suitable range, such as between 1 and 9 volume %, between 1 and 8 volume %, between 2 and 8 volume %, or between 3 and 7 volume %.

[0072] In embodiments where the composition comprises a redox-active organic component (in an amount of q volume %), an electronically insulating polymer (in an amount of z volume %), an alkali metal salt, an organic solvent, and an electrochemically active material (together in an amount totaling x volume %), and a conductive additive (in an amount of y volume %), then x+y+z+q=100 volume %.

[0073] In some such embodiments, typically (x+y)>(q+z).

[0074] In some such embodiments, q / (q+z) is typically at least 0.25, such as at least 0.27 or at least 0.30. In further examples, q / (q+z) can be at least 0.32, at least 0.35, or at least 0.40. In some such embodiments, q / (q+z) is typically less than 0.5, such as up to 0.49, up to 0.47, up to 0.45, or up to 0.40. Thus, in some such embodiments, when x+y>70% by volume, then q / (q+z) is typically between 0.25 and less than 0.50. Other combinations of the above values ​​can be combined to form a suitable range, such as between 0.27 and less than 0.50, between 0.27 and 0.49, or between 0.30 and 0.45.

[0075] Also provided herein is a method for making an electrode precursor composition as described herein. Typically, the method comprises mixing a redox-active organic component, an electrically insulating polymer, an alkali metal salt, and an organic solvent. Typically, this blend forms a gel. Without wishing to be bound by theory, it is believed that cooling provides sufficient mechanical strength for the gel. These components can be mixed in any suitable manner, simultaneously or in any suitable order, for any suitable time. For example, each of the appropriate amounts can be added and mixed simultaneously.

[0076] Subsequently, the blend of organic solvent, alkali metal salt, electrically insulating polymer and redox-active organic component is mixed with electrochemically active material and conductive additive and optionally any other components. The electrochemically active material and conductive additive can be combined with the blend simultaneously or in any suitable order, at any suitable time, and in any suitable manner.

[0077] Typically, the components are mixed together using various standard mixing equipment such as planetary mixing to ensure good dispersion of the components. The mixture is then passed through a twin-screw extruder at high temperature (>110°C), which can combine the polymer and liquid into a viscous gel. Alternatively, each component can be fed into the extruder individually through a separate feeder and mixed inside the extruder. The material can then be extruded directly into a sheet through a die, or it can be roughly extruded before being calendered into a film. The film can be adhered to a metal foil and then assembled into a battery.

[0078] Any suitable equipment for preparing electrode precursor compositions can be used to prepare the electrode precursor compositions herein, such as standard mixing equipment.

[0079] The electrode precursor composition can then be processed into an electrode as described herein.

[0080] Also provided herein is a method for preparing an electrode for an alkali metal ion secondary battery. Typically, the method includes a providing step and a processing step, wherein the providing step includes providing an electrode precursor composition as described herein, and the processing step includes processing the electrode precursor composition to form an electrode. Therefore, it should be understood that the electrode precursor composition as described herein is used to prepare an electrode according to the present invention. Therefore, the steps for preparing the electrode precursor composition described elsewhere herein are also applicable to the providing step of the method for preparing an electrode.

[0081] In some embodiments, the processing step includes one or more of extrusion and heat treatment.

[0082] In some embodiments, the treatment step includes at least heat treatment. That is, the treatment step includes a step of applying high temperature during the fluidization process.

[0083] In some embodiments, the thermal treatment comprises passing the electrode precursor composition through a roller assembly at a temperature of at least 50° C., such as at least 60° C., at least 70° C., at least 80° C., at least 90° C., or at least 100° C. In some embodiments, the thermal treatment comprises passing the electrode precursor composition through rollers at a temperature of up to 150° C., such as up to 140° C. or up to 130° C. In some embodiments, the thermal treatment comprises passing the electrode precursor composition through rollers at a temperature of 50° C. to 150° C., such as 60° C. to 150° C., 70° C. to 150° C., 80° C. to 150° C., 80° C. to 140° C., 90° C. to 140° C., 100° C. to 140° C., or 110° C. to 130° C.

[0084] The roller assembly may include two rollers separated by a small distance so that the electrode precursor composition is pressed into a thin film as it passes over the rollers.

[0085] In some embodiments, the processing step comprises at least extruding the electrode, or extruding. In some embodiments, the processing step comprises extruding the electrode using an extrusion device, the extrusion device comprising one or more screw feed sections and an extrusion die. In some embodiments, extrusion is achieved using a twin screw extruder.

[0086] In some embodiments where extrusion and heat treatment are used in the processing step, the temperature of the die is at least 50° C., such as at least 60° C., at least 70° C., at least 80° C., at least 90° C., or at least 100° C. In some embodiments, the temperature of the die is up to 150° C., such as up to 140° C. or up to 130° C. In some embodiments, the temperature of the die is between 50° C. and 150° C., such as between 60° C. and 150° C., between 70° C. and 150° C., between 80° C. and 150° C., between 80° C. and 140° C., between 90° C. and 140° C., between 100° C. and 140° C., or between 110° C. and 130° C.

[0087] In some embodiments, the thickness of the electrode is less than 150 μm, such as less than 100 μm, less than 90 μm, less than 80 μm, or less than 70 μm. In some embodiments, the thickness of the electrode is 40 to 150 μm, such as 40 to 100 μm, 40 to 90 μm, 40 to 80 μm, 40 to 70 μm, or 50 to 70 μm. In a specific embodiment, the thickness of the electrode is 40 to 100 μm.

[0088] In some embodiments, the electrode has a thickness of 40 to 150 μm, e.g., 40 to 100 μm, 40 to 90 μm, 40 to 80 μm, 40 to 70 μm, or 50 to 70 μm, and comprises 60 to 75% by volume of the electrochemically active material, e.g., 60 to 70% by volume, 60 to 69% by volume, 60 to 68% by volume, or 62 to 69% by volume of the electrode precursor composition.

[0089] In some cases, the extruded electrode may form part of an extruded monolith that includes one or more additional layers present in an electrochemical cell. For example, the monolith may include a separator layer, and / or may include another electrode (i.e., the extruded monolith may include a cathode and an anode). Different layers may be coextruded and have different compositions from each other.

[0090] In some embodiments, the methods of the present invention further comprise shaping and / or cutting the electrode to form an electrode of a predetermined size.

[0091] In some embodiments, the electrode film has a thickness of 500 to 700 μm. In some embodiments, the method of the present invention further comprises performing a second heat treatment step on the cut film to reduce the thickness of the film to a range of 50 to 70 μm.

[0092] In some embodiments, the temperature during the heat treating step is 100 to 140°C.

[0093] As an aspect of the present invention, an electrode prepared by the method of the present invention or from the electrode precursor composition of the present invention is also provided herein. Typically, the electrode obtained by the method of the present invention is a gel electrode.

[0094] In some embodiments, the electrode prepared by the method of the present invention has a porosity of less than 10%, such as a porosity of less than 8%, a porosity of less than 5%, a porosity of less than 3%, or a porosity of less than 1%. In some embodiments, the electrode prepared by the method of the present invention has a porosity of 0%.

[0095] For example, electrode porosity can be determined by comparing theoretical density to observed density. That is, a technician can calculate the theoretical density of the electrode and then measure the actual electrode density using a suitable method. Subsequently, the actual density is subtracted from the theoretical density to obtain the porosity.

[0096] Without wishing to be bound by theory, the inventors believe that lower porosity is generally advantageous because it reduces the tortuosity of ions (e.g., lithium ions) moving through the electrode gel. Therefore, the initial rate performance of the electrode is expected to be higher than that of an electrode with higher porosity. For similar reasons, it is expected that electronic conductivity may be similarly affected. Therefore, the inventors expect that energy density is related to porosity.

[0097] One aspect of the present invention also provides an electrochemical secondary battery cell comprising such an electrode. The battery cell may be an alkali metal ion secondary battery cell, such as a sodium ion secondary battery cell or a lithium ion secondary battery cell. In some embodiments, the battery cell is a lithium ion secondary battery cell.

[0098] In some embodiments, the electrochemical secondary battery cell comprises a first electrode according to the present invention and an anode, wherein the first electrode is a cathode. In some embodiments, the electrochemical secondary battery cell comprises a second electrode according to the present invention and a cathode, wherein the second electrode is an anode. In some embodiments, the electrochemical secondary battery cell comprises a first and a second electrode according to the present invention, wherein the first electrode is a cathode and the second electrode is an anode. In each of these embodiments, the electrochemical secondary battery cell further comprises an electrolyte between the cathode and the anode. In some embodiments, the electrolyte is a liquid electrolyte. In some embodiments, the liquid electrolyte comprises or is a solution containing an alkali metal salt as described herein.

[0099] In some embodiments, an electrochemical secondary battery cell includes an electrode according to the present invention laminated with a current collector such as a metal foil.

[0100] As an aspect of the present invention, an electrochemical energy storage device comprising an electrochemical secondary battery cell of the present invention is also provided herein. In some embodiments, the electrochemical energy storage device is a battery. In some embodiments, the electrochemical energy storage device is a lithium-ion battery.

[0101] One aspect of the present invention also provides the use of a redox-active organic component in a method for preparing an electrode for an alkali metal ion secondary battery cell, the method using at least one of a heat treatment step or an extrusion step. The redox-active organic component of this aspect is preferably a redox-active organic component as described herein for the first aspect. The method for preparing the electrode of this aspect is preferably the method of the second aspect described herein.

[0102] In some embodiments, such use provides the electrode with increased energy density compared to a corresponding electrode without the redox-active organic component.

[0103] Example

[0104] The following are exemplary electrode precursor compositions for use in the present invention:

[0105]

Claims

1. An electrode precursor composition suitable for preparing a gel electrode, the composition comprising an organic solvent, an alkali metal salt, an electrically insulating polymer and a redox-active organic component, wherein: The redox active organic component is present in a smaller volume fraction than the electrically insulating polymer.

2. The electrode precursor composition according to claim 1, wherein The redox-active organic component is present in the electrode precursor composition in an amount between 1 and 20 volume %, based on the total volume of the electrode precursor composition.

3. The electrode precursor composition according to claim 2, wherein The redox-active organic component is present in the electrode precursor composition in an amount of up to 8 volume %, based on the total volume of the electrode precursor composition.

4. An electrode precursor composition according to any one of the preceding claims, wherein The redox-active organic component is a redox-active polymer.

5. The electrode precursor composition according to claim 4, wherein The redox-active polymer comprises one or more selected from the group consisting of poly(3,4-ethylenedioxythiophene), polyaniline, polypyrrole and doped derivatives thereof, such as poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate.

6. An electrode precursor composition according to any one of the preceding claims, wherein The electrically insulating polymer comprises one or more selected from the group consisting of polyvinylidene fluoride, polyethylene oxide, polymethyl methacrylate and polyacrylonitrile.

7. The electrode precursor composition according to claim 6, wherein The electrically insulating polymer is present in the electrode precursor composition in an amount between 5 and 30 volume % based on the total volume of the electrode precursor composition.

8. An electrode precursor composition according to any one of the preceding claims, wherein The alkali metal salt includes a lithium salt.

9. The electrode precursor composition according to claim 8, wherein The lithium salt includes one or more of LiBF4, LiPF6, LiTFSI, LiFSI or LiTDI.

10. An electrode precursor composition according to any one of the preceding claims, wherein The organic solvent comprises one or more of carbonate, ether or nitrile.

11. An electrode precursor composition according to any one of the preceding claims, further comprising an electrochemically active material.

12. The electrode precursor composition according to claim 10, wherein The electrochemically active material includes a positive electrode active material.

13. The electrode precursor composition according to claim 11 or 12, wherein The electrochemically active material is present in the electrode precursor composition in an amount of at least 60 volume % based on the total volume of the electrode precursor composition.

14. The electrode precursor composition of any one of the preceding claims, further comprising an additive comprising conductive carbon.

15. The electrode precursor composition according to claim 14, wherein The conductive carbon includes one or more of carbon black, carbon nanotubes, graphene and graphite.

16. The electrode precursor composition according to claim 14 or 15, wherein The conductive carbon is present in the electrode precursor composition in an amount between 1 and 10 volume % based on the volume of the electrode precursor composition.

17. A method for preparing an electrode for an alkali metal ion secondary battery cell, the method comprising: A providing step, comprising providing an electrode precursor composition according to any one of claims 1 to 16; as well as The processing step includes processing the electrode precursor composition to form an electrode.

18. The method according to claim 17, wherein: The processing step includes one or more of extrusion and heat treatment.

19. The method according to claim 17 or 18, wherein: The providing step comprises providing an electrode precursor composition according to any one of claims 1 to 10, followed by combining the electrode precursor composition with an electrochemically active material and conductive carbon.

20. The method according to any one of claims 16 to 19, wherein: The electrodes are gel electrodes.

21. An electrode for an alkali metal ion secondary battery cell, prepared from the electrode precursor composition according to any one of claims 1 to 16, or prepared by the method according to any one of claims 17 to 20.

22. An electrochemical secondary battery cell comprising the electrode according to claim 21.

23. An electrochemical energy storage device comprising the electrochemical cell according to claim 22.

24. Use of a redox-active organic component in a method for producing an electrode for an alkali metal ion secondary battery cell using a high temperature treatment step.

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