Method for conditioning an aqueous ink for battery electrode

Abstract

A method for conditioning an aqueous ink for a battery electrode, comprising the following steps: i) carrying out a first solidification step by bringing the ink to a temperature between -2 and 2°C, preferably between -1 and 1°C, even more preferably equal to 0°C; and ii) carrying out a second solidification step by bringing the ink to a temperature between -10 and -30°C, preferably between -15°C and -25°C, even more preferably equal to -20°C.

Description

Title of the invention: Method for conditioning an aqueous ink for a battery electrode

[0001] The present invention relates, in general, to battery electrodes and, more particularly, to the manufacture of a battery electrode.

[0002] More specifically, the invention relates to a method for packaging an aqueous ink for a battery electrode, as well as a method for manufacturing a battery electrode.

[0003] An electric battery is formed by one or more electrochemical cells each incorporating a positive electrode, called a cathode, carried by a metal current collector, a negative electrode, called an anode, also carried by a metal current collector, and an electrolyte making it possible to ensure the movement of ions between the two electrodes, such as lithium ions in the case of a lithium-ion battery.

[0004] The positive and negative electrodes of the electrochemical cell are produced by a coating step which consists of depositing a thin layer of ink on the metal current collector generally formed by a strip.

[0005] The ink conventionally comprises an active material, a polymer binder and an electrically conductive agent dispersed homogeneously in a solvent.

[0006] The negative electrode of a lithium-ion battery comprises, for example, graphite as an active material, carbon as an electrically conductive additive, carboxymethylcellulose (CMC) and / or styrene-butadiene (SBR) as a binder and an aqueous solvent.

[0007] This ink is not very stable over time and degrades within a few hours due to sedimentation and evaporation of the aqueous solvent in the open air.

[0008] Coating must be carried out immediately and quickly after the end of the steps of mixing the ink components in order to maintain their homogeneity and before the ink becomes unusable.

[0009] The ink manufacturing step is therefore delicate and requires producing only a quantity appropriate to the tests to be carried out and defined in advance, leaving little flexibility during the manufacturing of the electrodes.

[0010] The invention therefore aims to remedy these drawbacks and to propose a solution aimed at optimizing the manufacture of battery electrodes by stopping the degradation in the open air of electrode inks incorporating an aqueous solvent following their formation, and allowing use of these inks at the desired time.

[0011] A method of conditioning an aqueous ink is therefore proposed for battery electrode, comprising the following steps:

[0012] i) carrying out a first solidification step by bringing the ink to a temperature of between -2 and 2°C, preferably between -1 and 1°C, even more preferably equal to 0°C; and

[0013] ii) carrying out a second solidification step by bringing the ink to a temperature between -10 and -30°C, preferably between -15°C and -25°C, even more preferably equal to -20°C.

[0014] Such low-temperature conditioning of the ink makes it possible to freeze its structure over time and prevent its deterioration so that the ink can be used later, whenever necessary.

[0015] Operators can be mobilized once for the manufacture of a large quantity of ink rather than multiple times for the manufacture of smaller quantities of ink. This leads to a saving of time on the stages of preparation of the production, the production itself and the cleaning stages.

[0016] Such a conditioning method is suitable for any type of aqueous battery ink: stationary battery, battery of an electric or electrified rolling vehicle such as a motor vehicle, a bus, a scooter, a motorcycle, etc., or battery of an electronic and / or portable device.

[0017] The ink is, for example, a lithium-ion battery ink.

[0018] It should be noted that, in the present description, the limits of a domain of values ​​are included in this domain, in particular in the expression “between”.

[0019] As indicated previously, the conditioning method comprises two consecutive steps i) and ii) of solidification of the ink and a first step i) of solidification of the ink.

[0020] Step i) is preferably carried out at an uncontrolled speed. Step i) is advantageously an ink setting step.

[0021] When a temperature between -2 and 2°C, preferably between -1 and 1°C, even more preferably equal to 0°C is reached, step ii) can be carried out.

[0022] To carry out step i), the ink can simply be placed in a freezer for rapid cooling.

[0023] Preferably, step ii) is carried out at a controlled speed.

[0024] Step ii) is carried out at a speed of between 1°C / min and 10°C / min. Such a range of values ​​makes it possible to quickly achieve homogeneous freezing of the ink.

[0025] Prior to steps i) and ii) the ink may be poured into one or more storage containers. The ink may thus be stored for up to 6 months without degrading.

[0026] In order to allow better control of the quantity of ink used, the capacity and the number of storage containers can be adapted to one or more desired subsequent uses of the ink.

[0027] The optimal quantities required for the manufacture of a batch of ink can then be defined in advance. A single batch of ink can thus be used for several electrode manufactures spread over time.

[0028] Such a packaging method makes it possible to transport electrode ink, which was previously impossible. It is then possible to send batches of packaged electrode ink to a third party, without damaging the product.

[0029] Another object of the invention is a method of manufacturing a battery electrode comprising the following steps:

[0030] a) preparing the electrode ink comprising an aqueous solvent;

[0031] b) storing the ink according to a conditioning method as described above;

[0032] c) thawing the ink;

[0033] d) coating a metal current collector with the ink;

[0034] e) allowing the coating to dry; and

[0035] f) recovering the electrode obtained.

[0036] Preferably, defrosting step c) is carried out in the open air.

[0037] The coating of the metal current collector is carried out quickly after thawing in order to avoid degradation of the ink in the open air.

[0038] Such conditioning of the ink during the manufacture of the battery electrode makes it possible to improve the reproducibility of the finished products. Indeed, the same batch of ink is used for several manufacturing operations carried out at different times in time.

[0039] It is possible, from the same batch of ink, to carry out different coatings, without needing to plan them in advance, which makes it possible to manufacture custom electrodes as soon as necessary.

[0040] In step c), the ink containers of desired volumes can be thawed as soon as necessary to carry out a new electrode production.

[0041] According to one example, the aqueous ink prepared in step a) may be a negative electrode ink for a lithium-ion battery.

[0042] The ink may comprise an active material, such as graphite, an electrically conductive additive, such as carbon black, a binder such as CMC and / or SBR, and an aqueous solvent.

[0043] The negative electrode may comprise 90-97% by weight of active material (example: graphite), 1-5% of carbon black, and 1-10% of CMC and / or SBR, the contents being considered as a function of the total weight of the electrode.

Claims

Claims

1. A method of conditioning an aqueous ink for a battery electrode, comprising the following steps: i) carrying out a first solidification step by bringing the ink to a temperature of between -2 and 2°C, preferably between -1 and 1°C, even more preferably equal to 0°C; and ii) carrying out a second solidification step by bringing the ink to a temperature of between -10 and -30°C, preferably between -15°C and -25°C, even more preferably equal to -20°C.

2. A method according to claim 1, wherein step ii) is carried out at a controlled speed.

3. A method according to claim 2, wherein step ii) is carried out at a rate of between 1°C / min and 10°C / min.

4. A method according to any preceding claim, wherein step i) is carried out at uncontrolled speed.

5. A method according to any preceding claim, wherein the ink is poured into one or more storage containers prior to steps i) and ii).

6. The method of claim 5, wherein the capacity of the storage containers is adapted to a desired use of the ink.

7. A method of manufacturing a battery electrode comprising the following steps: a. preparing an electrode ink comprising an aqueous solvent; b. storing the ink according to a packaging method according to any one of the preceding claims; c. thawing the ink; d. coating a metal current collector with the ink; e. allowing the coating to dry; and f. recovering the resulting electrode.

8. Method according to claim 7, in which step c) of thawing is carried out in the open air.