Electrode precursor composition

Abstract

An electrode precursor composition for an alkali metal ion secondary battery is described. The electrode precursor composition comprises a polymer-electrolyte gel matrix phase, a dispersed phase comprising an electrochemically active material and a conductive additive. The conductive additive contains a tubular carbon material as a main component. An electrode of the same composition, a method of producing the electrode, an electrochemical secondary battery incorporating the electrode, and an electrochemical energy storage device incorporating the battery are also described.

Description

[0001] BACKGROUND

[0002] Lithium-ion secondary batteries are the leading battery technology currently used in applications from small personal devices to electric vehicles. Among other benefits, lithium-ion batteries are favored for their high energy density and long cycle life. They contain a plurality of lithium-ion secondary cells, which are an example of alkali metal ion secondary cells.

[0003] Conventional lithium-ion battery components, such as electrodes, are made from solvent cast processes that use sacrificial solvents. This is an energy intensive step, so processes that avoid the use of sacrificial solvents are desirable.

[0004] One way to avoid the use of sacrificial solvents is to make gel electrodes. These electrodes can be formed from a composition made by mixing the necessary components, such as electrochemically active material, conductive additive, polymer, and liquid electrolyte, and then subjecting the composition to a heat treatment.

[0005] Battery manufacturing costs are reduced because gel components can be produced by simpler processing steps, without the slow and energy intensive drying of solvents required for solvent cast electrodes.

[0006] SUMMARY

[0007] Despite the advantages of gel electrode based solid state batteries, it has been found that gel electrode based solid state batteries can have reduced battery performance compared to some conventional batteries.

[0008] The present inventors have realized that replacing some or all of the conventional conductive additives used in gel electrode based solid state batteries with tubular carbon materials can provide potential for improved performance of gel electrode based solid state batteries.

[0009] Accordingly, in a first aspect, the present invention provides an electrode precursor composition for an alkali metal ion secondary cell, comprising:

[0010] a polymer-electrolyte gel matrix phase; and

[0011] a dispersed phase comprising an electrochemically active material and a conductive additive;

[0012] wherein the conductive additive comprises a tubular carbon material as a major component.

[0013] The term "major component" is used herein to define that the component makes up at least 50 wt% of the conductive additive. Preferably, the conductive additive is 60 wt% or more, 70 wt% or more, 80 wt% or more, 90 wt% or more, 95 wt% or more, 99 wt% or more tubular carbon. The component can also make up at least 50 vol% of the conductive additive, for example 60 vol% or more, 70 vol% or more, 80 vol% or more, 90 vol% or more, 95 vol% or more, 99 vol% or more tubular carbon.

[0014] In some embodiments, the conductive additive consists essentially of, or consists of, tubular carbon material. In such embodiments, the electrode precursor composition can not comprise an alternative non-tubular conductive additive component. That is, the electrode precursor composition can be essentially free of conductive carbonaceous materials other than tubular carbon material - for example, the electrode precursor composition can not comprise graphite, graphene and / or amorphous carbon (e.g. carbon black). In some embodiments, the electrode precursor composition can contain less than 0.5 wt% of conductive carbonaceous materials other than tubular carbon material, for example 0.1 wt% or less, 0.05 wt% or less, or 0.01 wt% or less.

[0015] The term "tubular carbon" is used herein to define a carbonaceous material having a generally tubular form. Tubular carbon materials can include, but are not limited to, carbon nanotubes (CNTs) (including SWCNTs and MWCNTs) and carbon fibres, for example carbon nanofibres (CNFs) and vapour grown carbon fibres (VGCFs).

[0016] The present inventors have found that by providing a conductive additive comprising tubular carbon as a major component, an electrode having improved electrochemical performance can be obtained. In particular, the present inventors have found that by providing a conductive additive comprising tubular carbon as a major component, the tortuosity value (tortuosity value related to Li+diffusion) of the resulting electrode can be reduced compared to an electrode which does not comprise tubular carbon as a major component of the conductive additive in the electrode. As discussed in more detail below, an electrode produced from an electrode precursor composition according to the first aspect can exhibit a tortuosity of 2.2 or less, as measured using electrochemical impedance spectroscopy on a symmetric cell incorporating the electrode, for example as described in Johannes Landesfeind et al. 2016 J. Electrochem. Soc. 163 A1373. When the electrode has a tortuosity of 2.2 or less, the electrode can exhibit a suitable ionic resistance to permit improved performance in high power applications.

[0017] The dispersed phase can consist of, or consist essentially of, the electrochemically active material and the conductive additive. That is, the dispersed phase can be essentially free of other components in addition to the electrochemically active material and the conductive additive.

[0018] The tubular carbon material can be a material selected from single-walled carbon nanotubes (SWCNT), multi-walled carbon nanotubes (MWCNT), carbon nanofibres (CNF), vapour grown carbon fibres (VGCF), or mixtures thereof. Preferably, the tubular carbon material comprises, consists essentially of, or consists of multi-walled carbon nanotubes (MWCNT). It has been found that the use of MWCNT can provide suitable performance at lower cost and manufacturing complexity compared to the use of SWCNT or tubular carbon materials based on carbon fibres.

[0019] In some embodiments, the electrochemically active material is a positive active material and the electrode precursor composition is a cathode precursor composition. In these embodiments, the positive active material can be a lithium transition metal oxide material. In some embodiments, the positive active material is a lithium transition metal oxide material comprising a mixed metal oxide of lithium and one or more transition metals, optionally further comprising one or more additional non-transition metals. In some embodiments, the positive active material is a lithium transition metal oxide material comprising lithium and one or more transition metals selected from nickel, cobalt and manganese. In some embodiments, the positive active material is selected from one or more of: lithium cobalt oxide (LCO), lithium manganese oxide (LMO), lithium nickel cobalt oxide (NCO), aluminium-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 (LMFP) and lithium nickel vanadate (LNV). In some embodiments, the positive active material is lithium nickel manganese cobalt oxide (NMC), optionally doped with additional metals such as aluminium. Such positive active materials are commercially available, or can be manufactured by methods known to those skilled in the art, for example by precipitating a mixed metal hydroxide intermediate from a reaction mixture containing different precursor metal salts, followed by calcination to form a mixed metal oxide and optionally lithiation to introduce lithium into the oxide.

[0020] The electrochemically active material can be undoped or uncoated, or can contain one or more dopants and / or coatings. For example, the electrochemically active material can be doped with small amounts of one or more metallic elements. The electrochemically active material can comprise a carbon coating on the surface of the material particles.

[0021] The electrochemically active material can be a pellet, i.e. a material composed of a plurality of discrete particles. The particles can comprise primary particles and / or secondary particles formed from agglomeration of a plurality of primary particles.

[0022] In some embodiments, the electrochemically active material comprises at least 50% by volume of the electrode precursor composition, such as at least 55% by volume, at least 60% by volume, at least 62% by volume, at least 64% by volume, or at least 65% by volume, based on the total volume of the electrode precursor composition. Suitably, in some embodiments, the electrochemically active material can comprise about 64% by volume of the electrode precursor composition.

[0023] As noted above, the dispersed phase further comprises a conductive additive, which includes a tubular carbon material as a primary component. In some embodiments, the conductive additive is present in an amount of 0.1% to 10% by volume, based on the total volume of the electrode precursor composition. For example, the conductive additive can comprise 0.3% to 5% by volume, 0.4% to 4% by volume, 0.5% to 3% by volume, or 0.55% to 2.5% by volume of the electrode precursor composition. In some embodiments, the conductive additive can comprise 1% by volume or more, such as 1% to 3% by volume of the electrode precursor composition. Suitably, in some embodiments, the conductive additive can be present in an amount of about 1.29% by volume, 1.89% by volume, or 2.48% by volume.

[0024] In some embodiments, the dispersed phase comprises 1.2% to 5% by volume of the conductive additive, based on the total volume of the dispersed phase, such as 1.3% or more, 1.4% or more, 1.5% or more, 1.6% or more, 1.7% or more, 1.8% or more, 1.9% or more, or 2% or more of the conductive additive, based on the total volume of the dispersed phase. The dispersed phase can comprise 4.5% or less, 4% or less, 3.9% or less, 3.8% or less, 3.7% or less, 3.6% or less, or 3.5% or less of the conductive additive, based on the total volume of the dispersed phase.

[0025] In some embodiments, the dispersed phase comprises 95% to 98.8% by volume of the electrochemically active material, based on the total volume of the dispersed phase, such as 96% or more, 97% or more, or 98% or more of the electrochemically active material. The dispersed phase can comprise 98% or less of the electrochemically active material. The dispersed phase can comprise 95% to 98% by volume, or 96.5% to 98% by volume of the electrochemically active material.

[0026] In some embodiments, the polymer-electrolyte gel matrix phase is formed from one or more electrolyte components and at least one gelling polymer.

[0027] The one or more electrolyte components can include a solvent suitable for use as an electrolyte solvent in a gel electrode, such as an organic solvent. The one or more electrolyte components can include a salt. In some embodiments, the one or more electrolyte components can constitute an electrolyte salt solution or a liquid electrolyte.

[0028] In some embodiments, the one or more electrolyte components comprise a solvent comprising one or more cyclic or linear carbonate compounds. In some embodiments, the solvent comprises one or more cyclic carbonate compounds. In some embodiments, the solvent comprises one or more of: ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, fluoroethylene carbonate, fluoropropylene carbonate, and gamma-butyrolactone.

[0029] In some embodiments, the solvent comprises a blend of at least two different compounds, such as at least three or at least four different compounds. In some embodiments, the solvent comprises a blend of at least two different organic carbonate compounds, such as at least three or at least four different organic carbonate compounds.

[0030] Preferably, the electrolyte components comprise a solvent having a low vapor pressure and a high flash point to enable safe processing. One example of a solvent that meets these criteria is propylene carbonate. Accordingly, the one or more electrolyte components can comprise, or consist of, propylene carbonate, or a blend of propylene carbonate and one or more of the solvents listed above.

[0031] In some embodiments, the one or more electrolyte components comprise an alkali metal salt. The alkali metal of the alkali metal salt can be any suitable alkali metal (Group I of the periodic table). The alkali metal salt can be a lithium salt, a sodium salt, or a potassium salt.

[0032] The anion of the alkali metal salt can be any suitable anion. Typical anions are known to those skilled in the art and can be selected based on the identity of the alkali metal. In some embodiments, when the alkali metal is lithium, the anion of the salt comprises a halogen such as fluorine. Examples include BF4-, PF6-, TFSI-, FSI-, OTf-, DFOB-, and TDI-.

[0033] In some embodiments, the one or more electrolyte components comprise a lithium salt. In some embodiments, the electrolyte comprises a mixture of at least two different lithium salts. Examples of suitable lithium salts include LiPF6, LiBF4, LiTFSI, LiFSI, LiOTf, LiDFOB, and LiTDI. Preferably, the salt is a thermally stable salt. LiPF6 has been found to have relatively low thermal stability relative to other available lithium salts, and thus use of LiPF6 can be avoided - i.e. in some embodiments, the electrolyte components do not include LiPF6.

[0034] One or more alkali metal salts can be used in accordance with the present application. Typically, but not exclusively, when more than one alkali metal salt is used, they share a common alkali metal.

[0035] The polymer-electrolyte gel matrix phase can comprise a gel matrix formed by one or more gelation polymers gelling upon absorption of the liquid electrolyte by the polymer. Thus, the polymer-electrolyte gel matrix phase comprises a gel comprising a polymer and an absorbed liquid electrolyte.

[0036] The gelation polymer can comprise one or more gelation polymers independently selected from the group consisting of poly(ethylene glycol dimethacrylate), poly(ethylene glycol diacrylate), poly(propylene glycol dimethacrylate), poly(propylene glycol diacrylate), poly(methyl methacrylate) (PMMA), poly(acrylonitrile) (PAN), polyurethane (PU), poly(vinylidene fluoride) (PVDF), poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), poly(ethylene oxide) (PEO), poly-L-lactic acid (PLA), polystyrene (PS), poly(ethylene glycol dimethyl ether), poly(ethylene glycol diethyl ether), poly[bis(methoxyethoxyethoxy)-phosphazene], poly(dimethylsiloxane) (PDMS), polyacenic hydrocarbon, polydisulfide, polystyrene, polystyrene sulfonate, polypyrole, polyaniline, polythiophene, polythioketone, polyvinylpyridine (PVP), polyvinyl chloride (PVC), polyaniline, poly(3,4-ethylenedioxythiophene) (PEDOT), poly(p-phenylene), poly(triphenylene), polyazulene, polyfluorene, polynaphthalene, polyanthracene, polyfuran, polycarbazole, tetrathiafulvalene-substituted polystyrene, ferrocene-substituted polyethylene, carbazole-substituted polyethylene, polyoxophenazine, poly(heteroacene), poly[(4-styrenesulfonyl)(trifluoromethylsulfonyl)imide-co-methoxypolyethylene glycol acrylate] (Li[PSTFSI-co-MPEGA]), sulfonated poly(phenylene oxide) (PPO), N,N-dimethylacrylamide (DMAAm), lithium 2-acrylamido-2-methyl-1-propane sulfonate (LiAMPS), poly(lithium 2-acrylamido-2-methylpropane sulfonate-co-vinyltriethoxysilane), polyethylene oxide (PEO) / poly(lithium sorbate), PEO / poly(lithium glutarate), PEO / [poly(lithium sorbate) + BF3], PEO copolymers, PEO terpolymers, and NIPPON SHOKUBAI® polymers, or mixtures or copolymers thereof.

[0037] In some preferred examples, the gelled polymer comprises one or more gelled polymers independently selected from poly(vinylidene fluoride) (PVDF), poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), poly(methyl methacrylate) (PMMA), poly(ethylene oxide) (PEO), poly-L-lactic acid (PLA), and polystyrene (PS).

[0038] In some embodiments, the polymer-electrolyte gel matrix phase constitutes 20 to 50 volume %, for example 25 to 45 volume %, 28 to 42 volume %, 30 to 40 volume %, 31 to 39 volume %, or 32 to 38 volume % of the electrode precursor composition. Suitably, in some embodiments, the polymer-electrolyte gel matrix phase can constitute approximately 33.52 volume %, approximately 34.11 volume %, or approximately 34.72 volume % of the electrode precursor composition.

[0039] In some embodiments, the electrode precursor composition is for use in a lithium-ion secondary electrochemical cell. In some embodiments, the electrode precursor composition is a cathode precursor composition.

[0040] A second aspect of the application is an electrode for an alkali metal-ion secondary battery, comprising:

[0041] a polymer-electrolyte gel matrix phase; and

[0042] a dispersed phase comprising an electrochemically active material and a conductive additive;

[0043] wherein the conductive additive comprises a tubular carbon material as a major component.

[0044] In some embodiments, the electrode exhibits a tortuosity of 2.2 or less, as measured using electrochemical impedance spectroscopy on a symmetric cell incorporating the electrode, for example as described in Johannes Landesfeind et al. 2016 J. Electrochem. Soc. 163 A1373. When the electrode has a tortuosity of 2.2 or less, the electrode can exhibit a suitable ionic resistance to permit improved performance in high power applications. In some embodiments, the electrode can exhibit a tortuosity in the range 1-2. The tortuosity may, for example, be 1.6 or less, 1.5 or less, 1.4 or less, or 1.3 or less.

[0045] In some embodiments, the electrode has an ionic conductivity of 1.2 mS / cm or more, as measured using electrochemical impedance spectroscopy at 30 °C on a symmetric cell into which the electrode is introduced, for example as described in Johannes Landesfeind et al. 2016 J. Electrochem. Soc. 163 A1373. For example, the ionic conductivity can be 1.29 mS / cm or more, 1.3 mS / cm or more, 1.4 mS / cm or more, 1.5 mS / cm or more, 1.6 mS / cm or more, 1.7 mS / cm or more, 1.8 mS / cm or more or 1.9 mS / cm or more, as measured using electrochemical impedance spectroscopy at 30 °C on a symmetric cell into which the electrode is introduced.

[0046] In some embodiments, the capacity retention of the electrode is 20% or more at a C rate of 10C, as evaluated at 45 °C in a lithium metal half-cell with a glass fibre separator and 70 mI of electrolyte under standard conditions. For example, the capacity retention of the electrode can be 25% or more, 30% or more, 35% or more, 38% or more or 39% or more at a C rate of 10C, as evaluated at 45 °C in a lithium metal half-cell with a glass fibre separator and 70 mI of electrolyte under standard conditions.

[0047] In some embodiments, the capacity retention of the electrode is 70% or more at a C rate of 5C, as evaluated at 45 °C in a lithium metal half-cell with a glass fibre separator and 70 mI of electrolyte under standard conditions. For example, the capacity retention of the electrode can be 76% or more, 77% or more, 80% or more, 83% or more or 84% or more at a C rate of 5C, as evaluated at 45 °C in a lithium metal half-cell with a glass fibre separator and 70 mI of electrolyte under standard conditions.

[0048] In some embodiments, the electrode is produced by processing the electrode precursor composition according to the first aspect to form a film or coating.

[0049] In some embodiments, the processing comprises thermal processing and / or extrusion. The electrode can be an extruded electrode. In other embodiments, the electrode can be a hot rolled electrode. In other embodiments, the electrode is prepared by extruding the electrode precursor composition according to the first aspect via a die to form a film.

[0050] In some embodiments, the electrode is a cathode.

[0051] All of the composition options and preferences listed above for the electrode precursor composition of the first aspect apply equally to the electrode of the second aspect, including the specific information (identity) and relative amounts of the various components of the composition that do not change during the process of processing the precursor composition into an electrode.

[0052] In some embodiments, the thermal processing comprises passing the electrode precursor composition through a roller assembly at a temperature of at least 50 °C, e.g., 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 processing comprises passing the electrode precursor composition through a roller at a temperature of up to 150 °C, e.g., up to 140 °C, or up to 130 °C. In some embodiments, the thermal processing comprises passing the electrode precursor composition through a roller at a temperature of 50 °C to 150 °C, e.g., 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.

[0053] The roller assembly can comprise two rollers separated by a small distance, such that the electrode is pressed into a thin film as it passes through the rollers.

[0054] In some embodiments, the thermal processing comprises extruding the electrode. In some embodiments, the thermal processing comprises extruding the electrode using an extrusion apparatus comprising one or more screw feed sections and an extrusion die. In some embodiments, the temperature of the die is at least 50 °C, e.g., 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, e.g., up to 140 °C, or up to 130 °C. In some embodiments, the temperature of the die is 50 °C to 150 °C, e.g., 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.

[0055] In some embodiments, the electrode has a thickness of less than 150 µm, e.g., less than 100 µm, less than 90 µm, less than 80 µm, or less than 70 µm. 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.

[0056] 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.

[0057] In some embodiments, the electrode has a porosity of less than about 5% by volume. In some cases, the porosity of the electrode is less than 5%, less than 3%, or less than 2% by volume. Stated in another way, the bulk density of the electrode can be at least 95%, suitably at least about 97% or 98% of the density of a perfect non-porous electrode.

[0058] In some cases, the extruded electrode can form part of an extruded monolith that includes one or more additional layers present in the electrochemical battery. For example, the monolith can include a separator layer, and / or can include other electrodes (i.e. the extruded monolith can include both a cathode and an anode). Different layers can be co-extruded and have different compositions from one another.

[0059] A third aspect of the application provides an electrochemical secondary battery comprising an electrode according to the second aspect. The battery can be an alkali metal ion secondary battery, for example a sodium ion secondary battery or a lithium ion secondary battery. Preferably the battery is a lithium ion secondary battery. In some embodiments, the electrochemical secondary battery comprises a first electrode according to the second aspect, wherein the first electrode is a cathode, and a second electrode, wherein the second electrode is an anode, and an electrolyte between the cathode and the anode. In some embodiments, the electrochemical secondary battery comprises an electrode according to the second aspect, which is laminated together with a current collector (e.g. a metal foil).

[0060] A fourth aspect of the application provides an electrochemical energy storage device comprising an electrochemical secondary battery according to the third aspect. In some embodiments, the electrochemical energy storage device is a battery. In some embodiments, the electrochemical energy storage device is a lithium ion battery.

[0061] A fifth aspect of the application provides a method of making an electrode for an alkali metal ion secondary battery, comprising:

[0062] mixing a polymer, an electrolyte, an electrochemically active material, and a conductive additive comprising tubular carbon as a main component to form an electrode precursor composition according to the first aspect; and

[0063] processing the electrode precursor composition to form an electrode film.

[0064] In some embodiments, the electrode film has a thickness of 500 to 700 pm.

[0065] In some embodiments, the method further comprises cutting the electrode film to form an electrode having a predetermined size.

[0066] In some embodiments, the method further comprises a second heat processing step to reduce the thickness of the film to be in the range of 50 to 70 pm after cutting.

[0067] In some embodiments, the temperature during thermal processing is 90 °C or more, for example from 100 to 140 °C.

[0068] EMBODIMENTS AND DETAILED DESCRIPTION

[0069] For all samples tested, the amounts of active material, conductive additive, polymer and electrolyte were determined by calculating the desired volume % and then converting that amount to the desired weight %. The appropriate amount of each material was then weighed and mixed. The mixture was then fed into a twin screw extruder with three mixing zones at several intervals. The body of the twin screw extruder was maintained at 120 degrees within the mixing zones, ramping from 40 degrees at the input port and dropping to 80 degrees at the exit. After the material was fed into the twin screw extruder, it was collected as a granular mixture.

[0070] The granular mixture was then rolled into a thin film. The precursor material was fed into a hot roller assembly to produce a film of the target thickness, typically 50-70 pm, depending on the formulation.

[0071] Gel electrode precursor compositions were prepared according to the compositions shown in Table 1 :

[0072]

[0073] Each of the electrode precursor compositions in Table 1 was formed into a gel electrode film by the method set out above.

[0074] The tortuosity, ionic and electronic conductivity values (IC, EC) of these electrode films were then measured, the results of which are set out in Table 2 below:

[0075]

[0076] These results were determined using electrochemical impedance spectroscopy on symmetric cells incorporating the electrodes, according to the methodology described in the following reference: Johannes Landesfeind et al. 2016 J. Electrochem. Soc. 163 A1373.

[0077] The rate performance of the electrode films was then evaluated in lithium metal half-cells with glass fibre separator and 70 pl electrolyte under standard conditions, the results of which are set out in Table 3 below:

[0078]

[0079] By comparing Comparative Example F1 and Example F2, it can be shown that when carbon black is replaced by MWCNT, the ionic conductivity increases significantly from 1.13 mS / cm to 1.74 mS / cm.

[0080] By comparing the rate capability of these two examples, it is shown that the high rate capability of Example F2 is significantly improved compared to Comparative Example Fl, increasing from 12.5% to 20% at 10C. Despite the much lower electronic conductivity of Example F2 compared to Example Fl.

[0081] By comparing Examples F3 and F4, it can be shown that by increasing the volume % of tubular carbon used as the conductive additive, the electronic conductivity of the electrode can be significantly increased, while the IC only moderately decreases. This leads to a significant improvement in the rate capability.

[0082] By comparing Examples F5, F6 and F7, it can be shown that replacing tubular carbon with carbon black leads to significantly lower ionic conductivity, and subsequently lower rate capability, regardless of the electronic conductivity. However, each of the examples using 50 vol% or more of tubular carbon shows improved electrochemical performance relative to Comparative Example Fl, with reduced tortuosity compared to the comparative example containing no tubular carbon, and increased ionic and electronic conductivity.

[0083] All examples according to the present application are seen to exhibit a tortuosity value of 2 or less, in particular 1.6 or less, thereby showing an improvement relative to Comparative Example Fl, which exhibits a tortuosity of 2.2.

[0084] Furthermore, all examples according to the present application are seen to exhibit an ionic conductivity value of 1.29 mS / cm (at 30°C) or more, thereby showing an improvement relative to Comparative Example Fl, which exhibits an ionic conductivity value of 1.13 mS / cm (at 30°C).

[0085] From these examples, it is concluded that the use of a tubular carbon material as a primary component of the conductive additive in an electrode precursor composition can provide significantly improved electrochemical performance of an electrode formed from said electrode precursor composition. In particular, a significant improvement in high rate capability is seen.

Claims

1. An electrode precursor composition for use in alkali metal ion secondary batteries, comprising: Polymer-electrolyte gel matrix phase; and A dispersed phase containing electrochemically active materials and conductive additives; The conductive additive contains tubular carbon material as the main component.

2. The electrode precursor composition according to claim 1, wherein the tubular carbon material constitutes 90% by weight or more of the conductive additive, optionally wherein the conductive additive is substantially composed of the tubular carbon material.

3. The electrode precursor composition according to claim 1 or claim 2, wherein the electrode precursor composition is substantially free of conductive carbonaceous materials other than the tubular carbon material, and optionally, wherein the electrode precursor composition is substantially free of graphite, graphene and / or amorphous carbon such as carbon black.

4. The electrode precursor composition according to any one of the preceding claims, wherein the tubular carbon material comprises or is composed of single-walled carbon nanotubes (SWCNTs) and / or multi-walled carbon nanotubes (MWCNTs).

5. The electrode precursor composition according to claim 4, wherein the tubular carbon material is substantially composed of multi-walled carbon nanotubes (MWCNTs).

6. The electrode precursor composition according to any one of the preceding claims, wherein the electrochemical active material is a positive electrode active material.

7. The electrode precursor composition according to claim 6, wherein the electrochemically active material is a lithium transition metal oxide material.

8. The electrode precursor composition according to any one of the preceding claims, wherein the electrochemically active material comprises at least 50% by volume of the electrode precursor composition, based on the total volume of the composition.

9. The electrode precursor composition according to any one of the preceding claims, wherein the electrode precursor composition comprises 20 vol% to 50 vol% of a polymer-electrolyte gel matrix phase, based on the total composition volume.

10. The electrode precursor composition according to any one of the preceding claims, wherein the conductive additive is present in an amount of 0.1 vol% to 10 vol% based on the total weight / volume of the electrode precursor composition.

11. The electrode precursor composition according to any one of the preceding claims, wherein the polymer-electrolyte gel matrix phase is formed of one or more electrolyte components and at least one gelling polymer, and wherein the gelling polymer comprises one or more gelling polymers independently selected from the group consisting of: poly(ethylene glycol dimethacrylate), poly(ethylene glycol diacrylate), poly(propylene glycol dimethacrylate), poly(propylene glycol diacrylate), poly(methyl methacrylate) (PMMA), poly(acrylonitrile) (PAN), polyurethane (PU), poly(vinylidene fluoride) (PVDF), poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), poly(ethylene oxide) (PEO), poly-L-lactic acid (PLA), polystyrene (PS), poly(ethylene glycol dimethyl ether), poly(ethylene glycol diethyl ether), poly[bis(methoxyethoxyethoxy)phosphazene], poly(dimethylsiloxane) (PDMS), poly(phenylene oxide), polydisulfide, polystyrene, polystyrene sulfonate, polypyrrole, polyaniline, polythiophene, polythioketone, poly(ethylene glycol dimethyl ether), poly(ethylene glycol dimethyl ether), poly[bis(methoxyethoxyethoxy)phosphazene], poly(dimethylsiloxane) (PDMS), poly(ethylene glycol dimethyl ether ...(ethylene glycol dimethyl ether), poly(ethylene glycol dimethyl ether), poly(ethylene glycol dimethyl ether), poly(ethylene glycol dimethyl ether), poly(ethylene glycol dimethyl ether), poly(ethylene glycol dimethyl ether), poly(ethylene glycol dimethyl ether), poly(ethylene glycol dimethyl ether), poly(ethylene glycol dimethyl ether), poly(ethylene glycol dimethyl ether), poly(ethylene glycol Alkenylpyridine (PVP), polyvinyl chloride (PVC), polyaniline, poly(3,4-ethylenedioxythiophene) (PEDOT), poly(p-phenylene), poly(triphenylene), polyazine, polyfluorene, polynaphthalene, polyanthracene, polyfuran, polycarbazole, tetrathiofulvalene-substituted polystyrene, ferrocene-substituted polyethylene, carbazole-substituted polyethylene, polyoxyphenazine, poly(hexabenzobenzene), poly[(4-styrenesulfonyl)(trifluoromethanesulfonyl)imide-co-methoxy polyethylene glycol acrylate](Li[PSTFSI-co-MPEGA) ]), sulfonated poly(phenylene ether) (PPO), N,N-dimethylacrylamide (DMAAm), lithium 2-acrylamido-2-methyl-1-propanesulfonate (LiAMPS), poly(lithium 2-acrylamido-2-methylpropanesulfonate-co-vinyltriethoxysilane), polyethylene oxide (PEO) / poly(lithium sorbate), PEO / poly(lithium mucinate), PEO / [poly(lithium sorbate)+BF3], PEO copolymers, PEO terpolymers and NIPPONSHOKUBAI® polymers.

12. The electrode precursor composition according to claim 11, wherein the one or more electrolyte components comprise: (i) A solvent suitable for use as an electrolyte solvent in a gel electrode, such as an organic solvent; and (ii) Salt.

13. An electrode for use in an alkali metal ion secondary battery, comprising: Polymer-electrolyte gel matrix phase; and A dispersed phase containing electrochemically active materials and conductive additives; The conductive additive contains tubular carbon material as the main component.

14. The electrode according to claim 13, which is produced by processing the electrode precursor composition according to any one of claims 1 to 12 to form a film or coating.

15. The electrode of claim 14, wherein the processing comprises thermal processing or extrusion.

16. The electrode according to any one of claims 13 to 15, wherein the electrode has a tortuosity of 2.2 or less, which is measured by electrochemical impedance spectroscopy for a symmetrical cell to which the electrode is introduced.

17. The electrode according to any one of claims 13 to 16, wherein the electrode has an ionic conductivity of 1.2 mS / cm or higher, which is measured at 30°C.

18. The electrode according to any one of claims 13 to 17, wherein the capacity retention of the electrode is 20% or higher at a C-rate of 10C, which is evaluated under standard conditions at 45°C in a lithium metal half-cell having a glass fiber separator and 70 µl of electrolyte.

19. An electrochemical secondary cell comprising an electrode according to any one of claims 13 to 19.

20. An electrochemical energy storage device comprising the electrochemical secondary battery according to claim 20.

21. A method for producing electrodes, including: A mixture of polymer, electrolyte, electrochemically active material and conductive additive comprising tubular carbon as a main component is used to form an electrode precursor composition according to any one of claims 1 to 12. as well as The electrode precursor composition is processed to form an electrode film.

Images