Energy storage and / or conversion device and method for manufacturing such an energy storage and / or conversion device

Abstract

The device 1 for storing and / or converting energy includes one or more spacers 2 defining two surfaces and electrodes 3 in contact with one or both surfaces of the spacers 2, each electrode 3 containing an ink including at least one conductive additive. The method includes the following steps: preparing an ink including at least one conductive additive; forming the electrodes 3 using the ink; and contacting the electrodes 3 with one or both surfaces of the one or more spacers 2. This allows the spacers themselves to function as current collectors, providing a solution to the problem of oxidation of metal current collectors.

Description

[Technical Field]

[0001] The present invention relates to energy storage and / or conversion devices and methods for making such energy storage and / or conversion devices. [Background technology]

[0002] Currently, energy storage devices are equipped with metal current collectors as conductive supports for the electrodes, as the electrodes do not function properly due to insufficient conductivity.

[0003] One of the biggest problems with energy storage devices is the current collector, because it is a metal component that is the heaviest and reduces energy density.

[0004] At the same time, current collectors are one of the most expensive components in a battery, especially nowadays due to material sourcing and its geographic location.

[0005] The solution that has been considered so far has been to make the current collector as thin as possible to reduce weight and cost, but the metal current collector remains.

[0006] Furthermore, this partial solution of reducing the thickness and weight of the current collector can cause problems during manufacturing, as very thin current collectors are extremely fragile and can break on the production line during printing and assembly, resulting in the economic cost of stopping production to remove the broken part and then restarting the machine. Summary of the Invention [Problem to be solved by the invention]

[0007] The energy storage and / or conversion device and method of the present invention overcomes the above-mentioned drawbacks and provides other advantages as described below. [Means for solving the problem]

[0008] The object of the present invention is therefore, inter alia, to propose a device for storing and / or converting energy and a method for placing electrodes on a spacer (separator), the spacer itself acting as a current collector, providing a solution to the problem of oxidation of the metal current collector.

[0009] These objectives are achieved by mixing the ink with graphene fibers, thereby providing the necessary conductivity to the electrodes without the use of metal current collectors.

[0010] Devices and methods for storing and / or converting energy according to the invention are set out in respective independent claims, with optional additional features included in the dependent claims.

[0011] It should be noted that in this specification and claims, the term spacer refers to any type of material that physically separates one material from another, such as the positive and negative electrodes of a battery.

[0012] It should be noted that in this specification and claims, the term energy storage and / or conversion device refers to any type of energy storage and conversion device, such as, for example, lithium batteries, sodium batteries, potassium batteries (including ion batteries, solid-state batteries, metal-air batteries, and organic batteries), fuel cells, electrolyzers, etc.

[0013] According to a first aspect, an apparatus for storing and / or converting energy comprises: one or more spacers defining two surfaces; and electrodes in contact with one or both sides of the spacer, each electrode being provided with an ink containing at least one conductive agent; It is equipped with:

[0014] Preferably, the conductive additive includes graphene fibers.

[0015] Additionally, the ink advantageously also includes a binder, an active material and a solvent.

[0016] Preferably, the spacers are made of cellulose, plastic, or fiberglass.

[0017] According to a second aspect, a method for manufacturing an energy storage and / or conversion device comprises: - preparing an ink, the ink comprising at least one conductive aid; and forming an electrode using said ink, the electrode being in contact with one or both sides of one or more spacers; Includes.

[0018] According to a preferred embodiment, the electrodes are formed by applying ink directly to both sides of the spacer, preferably by first applying ink to a first side of the spacer and allowing it to dry, and once the ink is dry, applying ink to a second side of the spacer and allowing it to dry.

[0019] According to an alternative embodiment, the electrodes are formed on the support, and once formed, the electrodes are placed in contact with both sides of the spacer.

[0020] If necessary, the method may include a final step of cutting the assembly of the spacer and the two electrodes.

[0021] The energy storage and / or conversion device according to the present invention is extremely versatile and has several advantages, including: -High energy density: By avoiding the use of metal current collectors, the total mass is significantly reduced, resulting in improved energy density per kilogram. - Lower final price: One of the most expensive components of an energy storage and / or conversion device is the metal current collector. By (at least partially) eliminating these current collectors and replacing them with one or more spacers that can be made from a variety of materials such as cellulose (paper), polymers (e.g., polypropylene), fibers (e.g., ceramic, glass, carbon, etc.), the device components are simplified and the cost reduced. - Minimized oxidation / reduction problems of current collectors. Whether the electrolyte solvent is an organic solvent or, more often, a water-based electrolyte (which is much more environmentally friendly and economical), degradation of the current collectors can have a significant impact on the stability of the device.

[0022] All of these advantages make the energy storage and / or conversion device and method according to the present invention better and cheaper than current energy storage and / or conversion devices.

[0023] For a better understanding of what has been described above, drawings are included, which show, by way of schematic and non-limiting example only, practical cases of embodiments. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a schematic cross-sectional view of an energy storage device according to the present invention; [Figure 2] The figure shows the charge-discharge cycles of an LFP and Li metal half-cell using a conventional current collector (aluminum) and LiPF6 1M EC / EMC = 50 / 50 (v / v) as the electrolyte. [Figure 3] Using the novel method described above on a polypropylene spacer, we demonstrate the charge-discharge cycling of an LFP and Li metal half-cell using LiPF6 1M EC / EMC = 50 / 50 (v / v) as the electrolyte. [Figure 4] The graphite and Li metal half-cell is shown as a charge-discharge cycle using a conventional current collector (copper) and LiPF6 1M EC / EMC = 50 / 50 (v / v) electrolyte. [Figure 5] Using the novel method described above on a polypropylene spacer, we demonstrate the charge-discharge cycling of a graphite and Li metal half-cell using LiPF6 1M EC / EMC = 50 / 50 (v / v) as the electrolyte. [Figure 6A] This shows a 10-hour charge-discharge cycle of a lithium-ion button cell battery with an aluminum current collector for the positive electrode and a copper current collector for the negative electrode, each with a cellulose spacer. Device: Stainless steel button cell; Positive electrode: Commercially available LFP on an aluminum current collector with conductive carbon; Negative electrode: Commercially available synthetic graphite on a copper current collector with conductive carbon; Electrolyte: LiPF6 1M EC / EMC = 50 / 50 (v / v). [Figure 6B] Using the novel method described above for the cellulose spacer, a 10-hour charge-discharge cycle of a lithium-ion button cell using LiPF6 1M EC / EMC = 50 / 50 (v / v) as the electrolyte is demonstrated. DETAILED DESCRIPTION OF THE INVENTION

[0025] An energy storage and / or conversion device according to the present invention, generally designated 1, comprises a spacer 2 having two electrodes 3 formed thereon by application of ink containing graphene fibers thereon, as shown schematically in FIG. 1.

[0026] In this way, the spacer 2 itself, which also functions as a current collector, provides a solution to, among other things, the oxidation problem of metal current collectors.The ink containing graphene fibers therefore provides the necessary conductivity to the electrode 3 without the use of metal current collectors.

[0027] The spacer 2 onto which the ink is applied can be any material used in energy storage and / or conversion devices, such as cellulose in capacitors, plastic or glass fiber spacers in lithium batteries, metal mesh, etc.

[0028] It should be noted that the device shown schematically in FIG. 1 is only one non-limiting example, and that devices according to the present invention may be double-spaced, with two spacers printed on only one side, or with spacers on a support, etc.

[0029] The manufacturing method according to the present invention begins with the preparation of the ink to be applied to the spacer 2.

[0030] The ink is prepared using a binder, a solvent, a conductive additive, and an active material. Any conventional binder can be used to prepare the ink, but the most common are polyvinylidene fluoride (PVDF) and styrene butadiene rubber (SBR).

[0031] The proportion of such binders may vary, for example, from 0.1% to 40% of the total mass of the ink. Any solvent may be used for printing, such as N-methyl-2-pyrrolidone (NMP), water, or alcohol.

[0032] The conductive additive may be a conductive carbon material such as carbon black, graphene fiber, carbon nanotube, graphite carbon, or the like, used alone or in combination. The amount of the conductive additive may vary from 0.1% to 40% of the total mass of the ink.

[0033] Once the binder is dissolved in a solvent and the remaining ingredients are added, the ink is homogenized using specialized systems (ball mills, shear mills, vacuum mixers, etc.).

[0034] Thereafter, ink is applied to one surface of the spacer 2 to form the electrode 3 .

[0035] This application can be done by any method (for example, by applying the ink to the spacer 2 using a doctor blade), but can also be done using systems such as lamination, inkjet, etc. By using a doctor blade, the ink can be applied to the cellulose spacer 2 to achieve the desired thickness.

[0036] Once the ink has been applied to one side of the spacer 2, it is dried, for example at a temperature of 20-150°C, for the time required to completely remove the solvent. After the initial drying or curing, the ink is applied to the other side of the spacer 2 and dried in the same manner.

[0037] It should be noted that this can also be achieved by applying the ink to a smooth surface from which the electrode can be taken as a wafer, which will be fully functional and will eliminate the need for a metal current collector.

[0038] The ink can also be applied to a fabric as a secondary support, but the fabric must be solvent soluble and can be removed with a corresponding solvent during assembly, leaving the electrode free of current collector and support.

[0039] Additionally, if desired, the spacer and electrode assembly can be cut to the desired shape, for example, in the case of a button cell, by cutting a circle of the desired diameter to obtain the desired shape.

[0040] To demonstrate the energy storage and / or conversion device according to the present invention, the following comparative examples are provided in the following description.

[0041] The lithium batteries were fabricated using a conventional LFP (lithium iron phosphate) battery configuration, with a LiPF61M EC / EMC (50 / 50 v / v) electrolyte and a polypropylene or cellulose spacer. Commercially available LFP was used as the positive electrode active material, along with a conductive additive and binder. Commercially available synthetic graphite was used as the negative electrode active material, along with the respective conductive additive and binder.

[0042] For testing, various electrodes were positioned in the conventional manner, using copper or aluminum current collectors as needed. After the electrodes were positioned, cut, and dried, various button cells were assembled in an argon-atmosphere glove box in the following configurations: First, a half-cell button cell was fabricated by assembling a commercially available LFP (lithium iron phosphate) cathode onto lithium metal using LiPF61M EC / EMC = 50 / 50 (v / v) as the electrolyte and a polypropylene spacer (Figure 2). The same configuration using the developed technique without the metal current collector is shown below (Figure 3).

[0043] Next, we fabricated a half-cell button battery by assembling a commercially available graphite anode against lithium metal, using LiPF61M EC / EMC = 50 / 50 (v / v) as the electrolyte, and a polypropylene spacer (Figure 4). The same configuration using the developed technique without the metal current collector is shown below (Figure 5).

[0044] Finally, Figure 6A shows multiple charge-discharge cycles of a lithium-ion button cell assembled with an aluminum current collector for the positive electrode (LFP) and a copper current collector for the negative electrode (graphite). LiPF61M EC / EMC = 50 / 50 (v / v) was used as the electrolyte, and cellulose was used as the spacer.

[0045] Figure 6B shows multiple charge-discharge cycles of a lithium-ion button cell assembled using the same materials for the cathode and anode, the same electrolyte, but using the newly developed method for the cellulose spacer. As can be seen in Figure 6B, the newly developed technique can be used with both polymer spacers (e.g., polypropylene) and cellulose spacers, and adequate operation is observed. Naturally, these results can be improved by using other materials for the spacer.

[0046] Although specific embodiments of the present invention have been described, it will be clear to those skilled in the art that many variations and modifications of the described method and device are possible and that the details described can be replaced by technically equivalents without departing from the scope of protection defined in the appended claims.

Claims

1. 1. A device for storing and / or converting energy, comprising: - one or more spacers (2) defining two faces, and - electrodes (3) in contact with one or both sides of said spacer (2), each electrode being provided with an ink containing at least one conductive agent; A device (1) for storing and / or converting energy, characterized in that it comprises:

2. The energy storage and / or conversion device (1) of claim 1, wherein the conductive agent comprises one or more forms of carbon, such as graphene fibers.

3. The device (1) for storing and / or converting energy according to claim 1, wherein the ink also comprises a binder, an active material, and a solvent.

4. 2. The device (1) for storing and / or converting energy according to claim 1, wherein the spacer (2) is made of cellulose, polymer, glass fiber or ceramic or a combination thereof.

5. A method for manufacturing a device (1) for storing and / or converting energy, comprising: - preparing an ink, said ink comprising at least one conductive aid; and - forming an electrode (3) using said ink, said electrode (3) being in contact with one or both sides of one or more spacers (2); 1. A method for producing a device (1) for storing and / or converting energy, comprising:

6. 6. The method for manufacturing a device (1) for storing and / or converting energy according to claim 5, wherein the electrodes (3) are formed by applying the ink directly to one or both sides of the spacer (2).

7. 6. A method for manufacturing a device (1) for storing and / or converting energy according to claim 5, wherein the electrodes (3) are formed on a support and, after being formed, the electrodes are placed in contact with both sides of the spacer (2).

8. A method for manufacturing a device (1) for storing and / or converting energy according to any one of claims 5 to 7, further comprising a final step of cutting the assembly of the spacer (2) and the two electrodes (3).

9. 7. The method for manufacturing a device (1) for storing and / or converting energy according to claim 6, wherein the ink is first applied to a first surface of the spacer (2) and dried, and once the ink is dry, the ink is applied to a second surface of the spacer (2) and dried.

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