METHOD FOR MANUFACTURING AN ELECTRODE COMPRISING A POLYMER MATRIX TRAPPING AN ELECTROLYTE

Abstract

A method for manufacturing an electrode comprising a polymer matrix trapping an electrolyte, the method comprising the following steps: a) a step of preparing a composition comprising the ingredients intended to be included in the constitution of the electrode; b) a step of forming the electrode, from the composition, on a support; wherein the composition prepared in step a) is a composition in paste form having a dynamic viscosity greater than 5000. Pa.Math.s measured at a shear gradient of 0.1 s-1 and at ambient temperature; and wherein the preparation step consists in introducing the ingredients intended to be included in the constitution of the electrode into a mixer with two co-rotating interpenetrating screws rotating in a closed sleeve, and mixing the ingredients therein, the preparation step being implemented at a temperature less than 100° C.

Claims

1. Method for manufacturing an electrode comprising a polymer matrix trapping an electrolyte, said method comprising the following steps: a) a step of preparing a composition comprising the ingredients provided to enter into the constitution of the electrode; b) a step of forming the electrode on a substrate, from said composition; wherein: the composition prepared in step a) is a composition in the form of a paste having a dynamic viscosity greater than 5000 Pa.Math.s measured at a shear rate of 0.1 s.sup.−1 and at ambient temperature; and the preparing step consists of introducing and mixing the ingredients provided to enter into the constitution of the electrode inside a mixer with two co-rotary interpenetrating screws rotating in a closed sleeve, said preparing step being implemented at a temperature less than 100° C.

2. Manufacturing method according to claim 1, wherein the composition comprises, as ingredients constituting the electrode: at least one electrode active material; at least one polymer provided to enter into the constitution of the polymer matrix; an electrolyte; optionally at least one electron conductor additive.

3. Manufacturing method according to claim 1, wherein the polymer or polymers are selected from gelling polymers suitable for gelling in contact with the electrolyte and thus trapping the electrolyte.

4. Manufacturing method according to claim 2, wherein the polymer or polymers are selected from fluorinated polymers comprising at least one repeat unit arising from the polymerization of a fluorinated monomer and, preferably, at least one repeat unit arising from the polymerization of a monomer comprising at least one carboxylic acid group, optionally in the form of a salt.

5. Manufacturing method according to claim 2, to wherein the electrolyte is a liquid electrolyte comprising at least one organic solvent, at least one metallic salt and optionally an additive belonging to the category of carbonaceous compounds.

6. Manufacturing method according to claim 2, wherein the composition further comprises at least one solvent of the polymer or polymers provided to enter into the constitution of the polymer matrix.

7. Manufacturing method according to claim 6, further comprising, after the forming step, a step of evaporating the solvent or solvents of the polymer or polymers provided to enter into the constitution of the polymer matrix.

8. Manufacturing method according to claim 2, wherein the composition is devoid of solvent or solvents of the polymer or polymers provided to enter into the constitution of the polymer matrix.

9. Manufacturing method according to claim 1, wherein the preparing step is implemented continuously.

10. Manufacturing method according to claim 6, wherein the preparing step is carried out at ambient temperature or is carried out at a temperature greater than the ambient temperature but less than 100° C.

11. Manufacturing method according to claim 6, wherein the preparing step is carried out at a temperature above the ambient temperature but less than the boiling temperature of the solvent or solvents of the polymer or polymers provided to enter into the constitution of the polymer matrix, when that solvent or those solvents are present in the composition or when that solvent or those solvents are not present, at a temperature greater than the ambient temperature but less than the melting temperature of the polymer or polymers provided to enter into the constitution of the polymer matrix.

12. Manufacturing method according to claim 2, wherein the composition further to the manufacturing step comprises from 50% to 80% of solid mass relative to the total mass of the composition, when it comprises a solvent or solvents of the polymer or polymers provided to enter into the constitution of the polymer matrix or comprises from 83 to 90% of solid mass relative to the total mass of the composition, when it does not comprise a solvent or solvents of the polymer or polymers provided to enter into the constitution of the polymer matrix.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0153] FIG. 1 is a graph illustrating the change in voltage U (in V) as a function of the capacity C (in mAh/g) for the negative electrode obtained according to the method of Example 1, curve a) being that of the 1.sup.st cycle and curve b) being that of the 2.sup.nd cycle.

[0154] FIG. 2 is a graph illustrating the change in voltage U (in V) as a function of the capacity C (in mAh/g) for the positive electrode obtained according to the method of Example 3, curve a) being that of the 1.sup.st cycle and curve b) being that of the 2.sup.nd cycle.

[0155] FIG. 3, described earlier, is a cross-section view of a specific biscrew mixer usable in the context of the method of the invention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Example 1

[0156] This example illustrates the manufacture by a continuous method in accordance with the invention of a negative electrode comprising 55% of solid mass relative to the total mass of the electrode.

[0157] In a first phase, an ionogel electrode paste is prepared by continuous introduction and mixing at 25° of the constituents of the electrode in the presence of acetone inside a mixer having two co-rotary interpenetrating screws rotating in a closed sleeve, the introduction being carried out, firstly, by the introduction of the solid constituents, then, secondly, by the introduction of the liquid constituents. The composition of the paste is as follows: 39.2 wt % of graphite (D.sub.50=20 μm) 13.1 wt % of graphite (D.sub.50=3.5 μm), 2.7 wt % of the copolymer constituting the polymer matrix (which copolymer is a copolymer comprising repeat units arising from the polymerization of vinylidene fluoride (96.7 mol %), acrylic acid (0.9 mol %) and hexafluoropropene (2.4 mol %) and having an intrinsic viscosity of 0.30 L/g in dimethylformamide at 25° C.), 37.5 wt % anhydrous acetone and 7.5 wt % 1M of LiPF.sub.6 electrolyte in a mixture of ethylene carbonate and propylene carbonate (1:1) containing 2 wt % vinyl carbonate.

[0158] The dynamic viscosity of the composition was measured on a CVO Bohlin rheometer of the Malvern brand equipped with a Peltier mounting and a mobile cone-plane of diameter 40 mm and angle 4°. For this, the paste is deposited between the Peltier mounting and the mobile member with a gap of 150 μm, a solvent trap is added to the system to avoid excessively fast evaporation of the acetone and the measurement is made in viscometer mode at a shear rate of 0.1 s.sup.−1 and 25° C. over an integration time of 5 seconds.

[0159] The dynamic viscosity measurement obtained is 7200 Pa.Math.s.

[0160] In a second phase, the electrode paste so formed is spread, at the outlet of the specific mixer on a sheet of copper of 10 μm thickness, then dried and calendered, thereby forming an ionogel graphite electrode. The weight per unit area of the electrode is 11.3 mg/cm.sup.2 (3.6 mAh/cm.sup.2) for a thickness of 90 μm. The capacity of the electrode was verified in a button cell against lithium metal.

[0161] The total measured capacity is 350 mAh/g and the reversible capacity is 300 mAh/g at the 1.sup.st cycle at C/20. The reversible capacity is 350 mAh/g at the 2.sup.nd cycle at C/20, these data being illustrated in FIG. 1, showing the change in the voltage U (in V) as a function of the capacity C (in mAh/g), curve a) being that of the 1.sup.st cycle and curve b) being that of the 2.sup.nd cycle.

Example 2

[0162] This example illustrates the manufacture of an ionogel electrode paste, said paste being prepared in accordance with the manufacturing step of the method of the invention and comprising 65% of solid mass relative to the total mass of the electrode.

[0163] This electrode paste is prepared by continuous introduction and mixing at 25° of the constituents of the electrode in the presence of acetone inside a mixer having two co-rotary interpenetrating screws rotating in a closed sleeve, the introduction being carried out, firstly, by the introduction of the solid constituents, then, secondly, by the introduction of the liquid constituents. The composition of the paste is as follows: 46.4 wt % of graphite (D.sub.50=20 μm) 15.4 wt % of graphite (D.sub.50=3.5 μm), 3.2 wt % of the copolymer constituting the polymer matrix (which copolymer is a copolymer comprising repeat units arising from the polymerization of vinylidene fluoride (96.7 mol %), acrylic acid (0.9 mol %) and hexafluoropropene (2.4 mol %) and having an intrinsic viscosity of 0.30 L/g in dimethylformamide at 25° C.), 24.2 wt % anhydrous acetone and 10.8 wt % 1M of LiPF.sub.6 electrolyte in a mixture of ethylene carbonate, propylene carbonate and dimethyl carbonate (1:1:3) containing 2 wt % vinyl carbonate.

[0164] It was not possible to measure the dynamic viscosity of the composition obtained using a CVO Bohlin rheometer of the Malvern brand on account of too high a dynamic viscosity (appreciably greater than 10 000 Pa.Math.s at a shear rate of 0.1 s.sup.−1).

Example 3

[0165] This example illustrates the manufacture by a continuous method in accordance with the invention of a positive electrode comprising 70% of solid mass relative to the total mass of the electrode.

[0166] In a first phase, an ionogel electrode paste is prepared by continuous introduction and mixing at 25° of the constituents of the electrode in the presence of acetone inside a mixer having two co-rotary interpenetrating screws rotating in a closed sleeve, the introduction being carried out, firstly, by the introduction of solid constituents, then, secondly, by the introduction of the liquid constituents. The composition of the paste is as follows: 65.8 wt % of LiNi.sub.0.33Mn.sub.0.33Co.sub.0.33O.sub.2, 2.8 wt % of an electron conductor additive, 1.4 wt % of the copolymer constituting the polymer matrix (which copolymer is a copolymer comprising repeat units arising from the polymerization of vinylidene fluoride (96.7 mol %), acrylic acid (0.9 mol %) and hexafluoropropene (2.4 mol %) and having an intrinsic viscosity of 0.30 L/g in dimethylformamide at 25° C.), 22.4 wt % anhydrous acetone and 7.6 wt % 1M of LiPF.sub.6 electrolyte in a mixture of ethylene carbonate and propylene carbonate (1:1) containing 2 wt % vinyl carbonate.

[0167] The dynamic viscosity of the composition was measured on a CVO Bohlin rheometer of the Malvern brand equipped with a Peltier mounting and a mobile cone-plane of diameter 40 mm and angle 4°. For this, the paste is deposited between the Peltier mounting and the mobile member with a gap of 150 μm, a solvent trap is added to the system to avoid excessively fast evaporation of the acetone and the measurement is made in viscometer mode at a shear rate of 0.1 s.sup.−1 and 25° C. over an integration time of 5 seconds.

[0168] The dynamic viscosity measurement obtained is 11 000 Pa.Math.s.

[0169] In a second phase, the electrode paste so formed is spread, at the outlet of the specific mixer on a sheet of aluminum of 20 μm thickness, then dried and calendered, thereby forming an ionogel graphite electrode. The weight per unit area of the electrode is 19.5 mg/cm.sup.2 (2.9 mAh/cm.sup.2) for a thickness of 95 μm. The capacity of the electrode was verified in a button cell against lithium metal. The total measured capacity is 170 mAh/g and the reversible capacity is 147 mAh/g at the 1.sup.st cycle at C/20. The reversible capacity is 143 mAh/g at the 2.sup.nd cycle at C/20, these data being illustrated in FIG. 2, showing the change in the voltage U (in V) as a function of the capacity C (in mAh/g), curve a) being that of the 1.sup.st cycle and curve b) being that of the 2.sup.nd cycle.

Example 4

[0170] This example illustrates the manufacture by a continuous method in accordance with the invention of a positive electrode comprising 80% of solid mass relative to the total mass of the electrode.

[0171] In a first phase, an ionogel electrode paste is prepared by continuous introduction and mixing at 25° of the constituents of the electrode in the presence of acetone inside a mixer having two co-rotary interpenetrating screws rotating in a closed sleeve, the introduction being carried out, firstly, by the introduction of solid constituents, then, secondly, by the introduction of the liquid constituents. The composition of the paste is as follows: 75.2 wt % of LiNi.sub.0,33Mn.sub.0,33Co.sub.0,33O.sub.2, 3.2 wt % of an electron conductor additive, 1.6 wt % of the copolymer constituting the polymer matrix (which copolymer is a copolymer comprising repeat units arising from the polymerization of vinylidene fluoride (96.7 mol %), acrylic acid (0.9 mol %) and hexafluoropropene (2.4 mol %) and having an intrinsic viscosity of 0.30 L/g in dimethylformamide at 25° C.), 11.3 wt % anhydrous acetone and 8.7 wt % 1M of LiPF.sub.6 electrolyte in a mixture of ethylene carbonate and propylene carbonate (1:1) containing 2 wt % vinyl carbonate.

[0172] It was not possible to measure the dynamic viscosity of the composition obtained using a CVO Bohlin rheometer of the Malvern brand on account of too high a dynamic viscosity (appreciably greater than 10 000 Pa.Math.s at a shear rate of 0.1 s.sup.−1).

[0173] In a second phase, the electrode paste so produced is formed into a strip via a slot-die placed at the outlet of the mixer, the strip then being laminated to reduce its thickness then deposited by co-lamination on a current collector of aluminum to form the ionogel electrode.

Example 5

[0174] This example illustrates the manufacture by a continuous method in accordance with the invention of a positive electrode comprising 90% of solid mass relative to the total mass of the electrode.

[0175] In a first phase, an ionogel electrode paste is prepared by continuous introduction and mixing at 25° of the constituents of the electrode in the presence of acetone inside a mixer having two co-rotary interpenetrating screws rotating in a closed sleeve, the introduction being carried out, firstly, by the introduction of solid constituents, then, secondly, by the introduction of the liquid constituents. The composition of the paste is as follows: 84.6 wt % of LiNi.sub.0.33Mn.sub.0.33Co.sub.0.33O.sub.2, 3.6 wt % of an electron conductor additive, 1.8 wt % of copolymer constituting the polymer matrix (which copolymer is a copolymer comprising repeat units arising from the polymerization of vinylidene fluoride (96.7 mol %), acrylic acid (0.9 mol %) and hexafluoropropene (2.4 mol %) and having an intrinsic viscosity of 0.30 L/g in dimethylformamide at 25° C.), 10 wt % 1M of LiPF.sub.6 electrolyte in a mixture of ethylene carbonate and propylene carbonate (1:1) containing 2 wt % vinyl carbonate.

[0176] It was not possible to measure the dynamic viscosity of the composition obtained using a CVO Bohlin rheometer of the Malvern brand on account of too high a dynamic viscosity (appreciably greater than 10 000 Pa.Math.s at a shear rate of 0.1 s.sup.−1).

[0177] In a first phase, the electrode paste so produced is formed into a strip via a slot-die placed at the outlet of the mixer, the strip then being laminated to reduce its thickness then deposited by co-lamination on a current collector of aluminum to form the ionogel electrode.