Method for conditioning an aqueous ink for a battery electrode

Abstract

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

Description

[0001] TITLE: Process for conditioning an aqueous ink for a battery electrode

[0002] The present invention relates, in general, to battery electrodes and, more particularly, to the manufacture of a battery electrode.

[0003] More specifically, the invention relates to a method of conditioning an aqueous ink for a battery electrode, as well as a method of manufacturing a battery electrode.

[0004] 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 allowing the movement of ions between the two electrodes, such as lithium ions in the case of a lithium-ion battery.

[0005] 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.

[0006] The ink typically comprises an active material, a polymer binder and an electrically conductive agent homogeneously dispersed in a solvent.

[0007] The negative electrode of a lithium-ion battery comprises, for example, graphite as the active material, carbon as the electrically conductive additive, carboxymethylcellulose (CMC) and / or styrene-butadiene (SBR) as the binder, and an aqueous solvent.

[0008] 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.

[0009] Coating must be carried out immediately and quickly after the end of the mixing steps of the ink components in order to maintain their homogeneity and before the ink becomes unusable. 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 manufacture 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 for conditioning an aqueous ink for a battery electrode is therefore proposed, 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.

[0012] Such low-temperature conditioning of the ink allows its structure to be fixed over time and prevents its deterioration so that the ink can be used later, whenever necessary.

[0013] Operators can be mobilized once to produce a large quantity of ink rather than multiple times to produce smaller quantities of ink. This leads to time savings in the production preparation stages, the production itself and the cleaning stages.

[0014] 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, bus, scooter, motorcycle, etc., or battery of an electronic and / or portable device.

[0015] The ink is, for example, lithium-ion battery ink.

[0016] It should be noted that, in the present description, the limits of a range of values ​​are included in this range, in particular in the expression "between". As indicated previously, the conditioning method comprises two consecutive steps i) and ii) of solidification of the ink a first step i) of solidification of the ink.

[0017] Step i) is preferably carried out at uncontrolled speed. Step i) is advantageously an ink setting step.

[0018] 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.

[0019] To perform step i), the ink can simply be placed in a freezer for rapid cooling.

[0020] Preferably, step ii) is carried out at controlled speed.

[0021] Step ii) is carried out at a speed between 1°C / min and 10°C / min. Such a range of values ​​allows for rapid achievement of homogeneous freezing of the ink.

[0022] Prior to steps i) and ii) the ink may be poured into one or more storage containers. The ink can thus be stored for up to 6 months without degrading.

[0023] In order to allow better control of the quantity of ink used, the capacity and number of storage containers can be adapted to one or more desired subsequent uses of the ink.

[0024] The optimal quantities required for the production of a batch of ink can then be defined in advance. A single batch of ink can thus be used for several electrode productions spread over time.

[0025] This packaging process 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.

[0026] Another object of the invention is a method for manufacturing a battery electrode comprising the following steps: a) preparing the electrode ink comprising an aqueous solvent; b) storing the ink according to a conditioning method as described previously; 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.

[0027] Preferably, step c) of thawing is carried out in the open air.

[0028] 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.

[0029] This type of ink conditioning during battery electrode manufacturing improves the reproducibility of finished products. Indeed, the same batch of ink is used for several production runs carried out at different times.

[0030] It is possible, from the same batch of ink, to make different coatings, without needing to plan them in advance, which allows custom electrodes to be manufactured as soon as necessary.

[0031] In step c), the ink containers of the desired volumes can be thawed as soon as necessary to carry out a new electrode production.

[0032] According to one example, the aqueous ink prepared in step a) may be a negative electrode ink for a lithium-ion battery.

[0033] The ink may include 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.

[0034] The negative electrode may comprise 90-97% by weight of active material (e.g. 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. Method for conditioning an aqueous ink for a battery electrode, comprising the following steps: i) carrying out a first solidification step by bringing T 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 T 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. Method according to claim 1, in which step ii) is carried out at controlled speed.

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

4. Method according to any one of the preceding claims, in which step i) is carried out at uncontrolled speed.

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

6. Method according to claim 5, in which 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.