Improved battery current collector

Abstract

Improved Current Collector for Batteries This application relates to a current collector for the negative electrode, coated with at least one electronically conductive and ionically insulating layer, the method for preparing such a collector, and batteries comprising it. Figure for abstract: None

Description

Description Title of the invention: Improved current collector for battery

[0001] The present invention relates to the field of energy storage, and more specifically- precisely the batteries, especially of the lithium type.

[0002] — Lithium-ion rechargeable batteries do indeed offer excellent densities energetic and volumetric and now occupy a prominent place on the the portable electronics market, electric and hybrid vehicles, and more stationary energy storage systems.

[0003] Their operation is based on the reversible exchange of lithium ions between a a positive electrode and a negative electrode, separated by an electrolyte.

[0004] Solid electrolytes also offer a significant improvement in terms of safety insofar as they present a much lower risk of flammability than electrical Liquid trolytes.

[0005] — However, the properties of solid electrolytes suffer degradation at contact with moisture. In the case of sulfide electrolytes, moisture leads in particular the emission of harmful gases (HS) which are likely to corrode the materials commonly used for current collectors, particularly copper, which is generally used for negative electrode current collectors.

[0006] It is therefore desirable to protect the current collectors from sulfide electrolytes.

[0007] — EP1032064 is intended to protect the current collector of a positive electrode aluminum is protected against corrosion by highly alkaline positive electrode metals: it The aim is therefore to locally reduce the pH. Furthermore, these positive electrodes are used with a liquid electrolyte.

[0008] | US2012 / 0237824 also aims at protecting the current collector of the electrode negative.

[0009] - WO2019 / 045399 relates to liquid electrolyte battery technology.

[0010] — Consequently, the proposed protections essentially relate to the protection of positive current collectors and / or liquid electrolytes.

[0011] — It is therefore necessary to protect the current collectors to prevent contact direct contact with a solid sulfide electrolyte, while maintaining electronic conduction between the electrolyte and the collector.

[0012] … The invention proposes to address this problem by proposing a layer of current collector protection, an electronically conductive layer and insulator of Li* ions.

[0013] — Thus, according to a first object, the present invention relates to a current collector negative electrode comprising a material susceptible to corrosion in consequence of the use of sulfides in the cell, characterized in that the collector is coated with at least one electronically conductive and Li-ion insulating layer* The corrosion described here can occur following direct contact between sulfide particles and the current collector, but also via the generation of HS gas (formed in particular in the presence of humidity), the presence of which is likely to corrode materials used in the composition of common current collectors. The term "electrical conductor" used here refers to the ability of the protective layer to allow electric current to pass through. The term "Li* ion insulator" used here refers to the ability of said layer to inhibit the transit of Li+ ions through said layer, between the active mass of the negative electrode and the current collector, the active mass comprising the active material, a possible binder, the solid electrolyte and a possible electronic conductor. According to one embodiment, said layer is made of a material which is not reactive with sulfides and does not lithiace. According to one embodiment, said at least one layer contains at least one material selected from carbon, silicon and mixtures thereof. According to this embodiment, the thickness of said at least one layer is between 1 and 100nm, preferably 3 to 10nm. According to another embodiment, said layer contains at least one material selected from chromium, chromium oxide or nickel oxide and mixtures thereof, or stainless steel. According to this embodiment, the thickness of said at least one layer is between 1 and 10nm, it being understood that in the case of oxides, the thickness is preferably between 1 and 10nm. According to one embodiment, said layer is free of fluorinated resin and / or oxalate. The collector is generally in the form of a strip of conductive material, such as a metal. Materials susceptible to corrosion include, in particular, nickel, copper, iron, molybdenum, zinc, and manganese. In one embodiment, the material susceptible to corrosion is copper. According to one embodiment, said current protector may be coated with one or more layers such as the aforementioned one, identical or different. According to one embodiment, the current collector according to the invention is suitable for solid sulfide-type electrolytes. Examples of sulfide electrolytes include Li-PS, and the set of phases [(Li-S),(P2S5)1.y]u-2 (LIX), (with X a halogen element; O <y<1 ; O<z<1), les argyrodites tels que LisPSsX, avec X=CI, Br, I, ou LiP; Su, les électrolytes sulfures ayant la structure cristallographique équivalente au composed of Li,,GeP,S,, According to one embodiment, the current collector according to the invention further comprises sulfur, in the form of a sulfide or a sulfur-based compound. According to another object, the present invention also relates to a method for preparing a coated current collector according to the invention, said method comprising the deposition of said layer on the collector. According to one embodiment, the deposition is carried out by physical or chemical vapor deposition (PVD or CVD). The PVD technique refers to any method of vacuum deposition of thin films, and notably includes the deposition of: @ by direct evaporation (Vacuum evaporation or evaporation; Electron beam evaporation in vapor phase); @ by cathodic sputtering "sputtering" by ion bombardment; @ by evaporation by ablation of a target with a pulsed laser "pulsed laser deposition" or "pulsed laser ablation" under the action of intense laser radiation; @ by molecular beam epitaxy; and @ by electric arc deposition (Arc-PVD) by vaporization under the action of a strong current, caused by electrical discharge between two electrodes presenting a strong potential difference. More specifically, the protective layer can be deposited by PVD by cathodic sputtering (PECVD). CVD involves exposing the substrate to one or more gas-phase precursors, which react and / or decompose on the substrate surface to generate the desired deposit. Materials in various forms can be deposited: single-crystal, polycrystalline, amorphous, and epitaxial. These materials include silicon, silica, silicon-germanium, silicon carbides, diamond carbon, fibers, nanofibers, filaments, carbon nanotubes, tungsten, high electrical permittivity materials, and more. CVD techniques vary depending on the means by which the chemical reactions are initiated and the process conditions: Classification according to total pressure Atmospheric pressure CVD (APCVYD) - CVD performed at at- mospheric. Low-pressure CVD (LPCVD) - CVD performed at sub-pressure atmospheric 1. Reduced pressures tend to reduce the unwanted gas-phase reactions and increased uniformity films along the substrates. Most current CVD processes are either LPCVD or UHVCVD. Ultrahigh vacuum CVD (UHVCVD) - CVD performed at very high pressure low, typically below 10⁻⁶ Pa (-1079 torr). NB: in other fields, a subdivision between “high” and “ultra-high vacuum” is common, often located at 107 Pa. Classification based on the physical characteristics of the reagent Aerosol assisted CVD (AACVD) - in which the precursor is transported to the substrate by means of a liquid aerosol: a gas that can be generated by ultrasound. This technique is suitable in the use cases for non-volatile precursors. Direct liquid injection CVD (DLICVD) - in which the pre- sliders are in a liquid state {liquid or solid dissolved in a suitable solvent). Liquid solutions are injected into a vaporization chamber using injectors. Then the pre- sliders are transported to the substrate as in a process Classic CVD. This technique is suitable for use with Liquid or solid precursors, high growth rates can be achieved using this technique. Plasma-assisted processes Microwave plasma-assisted CVD (MPCVD) Plasma-Enhanced CVD (PECVD) - in which a plasma is used to increase the reaction rate of precursors.” This variant allows deposition at lower temperatures (the temp- (temperature is often a sticking point). Remote plasma-enhanced CVD (RPECVD) - Similar to PECVD, except that the substrate is not directly in the region of the Plasma discharge. This allows for temperature treatments ambient. Atomic layer CVD (ALCVD) — Deposition of successive layers of different substances (see epitaxy) Hot wire CVD (HWCVD) – Also known as catalytic CVD (Cat-CVD) or hot filament activated CVD (HFCVD). Uses a hot filament to chemically decompose source gases. Metalorganic chemical vapor deposition (MOCVD) - CVD processes using metal-organic precursors. Hybrid Physical-Chemical Vapor Deposition (HPCVD) - a vapor phase deposition process that involves both the chemical decomposition of a gaseous precursor and the vaporization of a solid. Rapid thermal CVD (RTCVD) - CVD uses heating lamps or Other methods for quickly heating the substrate. By heating only the substrate rather than gas or chamber walls helps reduce the unwanted reactions that can lead to the formation of particles in- expected. Vapor Phase Epitaxy (VPE) - Epaxis in the vapor phase. More specifically, the protective layer can be deposited by CVD using atomic layer deposition (ALD) or by PECVD According to another object, the present invention further relates to an electrode comprising a current collector coated according to the invention such that said active material of said electrode is graphite. According to one embodiment, said electrode is a negative electrode. According to another object, the present invention also relates to an electro-chemical element comprising a current collector coated according to the invention and a solid electrolyte of the sulfide type. The term "electrochemical element" refers to a basic electrochemical cell consisting of a positive electrode / electrolyte / negative electrode assembly, which stores the electrical energy supplied by a chemical reaction and releases it in the form of a current. The electrochemical elements according to the invention are preferably accumulators with a capacity greater than 100 mAh, typically 1 to 100Ah. According to another object, the present invention also relates to an electro-chemical module comprising the stacking of at least two elements according to the invention, each element being electrically connected with one or more other element(s). The term "module" here therefore refers to the assembly of several electrochemical elements, said assemblies being able to be in series and / or parallel. According to another of these objects, the invention also relates to a battery comprising one or more modules according to the invention. The term "battery" refers to the assembly of several modules according to the invention. According to one embodiment, the battery can be a Li-ion type battery or a solid-state battery. Figures [fig.1] Figure 1 represents the structure of an electrochemical element according to the invention (left) and the detail of the current collector (right). Figure 1 schematically represents on the left an electrochemical element comprising, at the negative electrode: a current collector (1) coated with a protective layer (2) according to the invention, and at the positive electrode a current collector (7). The chemical element shown is of the all-solid type, where the anode and cathode are of composite type, being made up of a mixture of active material (3) and (6) respectively and electrolyte (4). The anode and cathode are separated by electrolyte. As illustrated on the right, the protective layer (2) provides the interface between the collector (1) and the active material particles (3) and electrolyte (4) that together form the composite anode. In addition, conductive particles (5), such as carbon black, are incorporated into the mixture of the active material (3) and the electrolyte (4). The active material is typically graphite. The electrolyte can be, in particular, a solid sulfide electrolyte. According to an alternative configuration not shown, the chemical element may also be of the all-solid Li-metal type, where the negative electrode may contain an alkali metal in the charged state, such as lithium metal. [fig.2] Figure 2 represents the discharged capacity and coulombic efficiency values ​​obtained for a cell according to the invention (Cu Si) and a comparative cell (Cu). Coulombic efficiency is the ratio of the capacity recovered during discharge divided by the capacity supplied during the previous charge. The following examples are given by way of illustration and not limitation of the invention: Example All powder handling was performed in a glove box under an argon atmosphere. The solid electrolyte used in this example is a LisPS;Cl type argyrodite (-1 mS / cm at room temperature). The composite mixture of NCA and sulfide electrolyte (SE) used as the positive electrode was prepared manually in a mortar, respecting the mass ratio of NCA:SE 70:30. The mixture used as the negative electrode was prepared according to the same protocol, using graphite and SE in mass proportions of graphite:SE 2:1. The complete graphite / SE / NCA cells were prepared in specific cells, similar to 7 mm diameter pelletizing molds with stainless steel pistons and a body made of electrically insulating material. First, 40 mg of electrolyte were introduced and then compressed under 250 MPa to form the separating electrolytic layer (SEL).The cell is then opened on one side to introduce 15 mg of the positive electrode mixture and an aluminum disc (serving as a current collector). The positive electrode is formed by compression at 250 MPa. 12 mg of the negative electrode mixture and a copper current collector are then introduced on the other side of the SEL. The entire cell is then compressed under 500 MPa for several minutes. A pressure of 250 MPa is subsequently maintained on the cell using screws. This first cell is designated as "Comparative Example: Cu" in the graphical representations. A second cell is assembled under the same conditions, but the copper collector of the negative electrode is replaced by a collector made from the same copper foil, but on which a 50 nm layer of silicon has been previously deposited by PECVD. This second cell is designated as "Example 1: Cu-Si" in the graphical representations. After a 12-hour rest period, the assembled cells are then characterized by galvanostatic cycling between 2.8 and 4.1 V at room temperature. The sequence [1 control cycle at C / 20 — 20 cycles at C / 10 — 1 control cycle at C / 20] is repeated 7 times. Figure 2 shows the discharged capacitance and coulombic efficiency values ​​obtained for these cells. Both cells exhibit similar discharged capacitance values ​​during the first 100 cycles, while the coulombic efficiency obtained for the cell containing the copper collector with silicon deposition is significantly improved compared to the comparative example. Indeed, the average coulombic efficiency values ​​between the 2nd and 22nd cycles (first sequence, excluding the first cycle) are 97.6% for Example 1: Cu-Si and only 87.6% for the comparative example. This difference reflects the significant reactions occurring within the negative electrode, particularly between the sulfide electrolyte and the copper current collector. A protective layer of only 50 nm considerably reduces these instabilities.

Claims

Demands

1. Current collector (1) of negative electrode comprising a material susceptible to corrosion in the presence of sulfides, characterized in that the collector (1) is coated with at least one electrically conductive layer (2) tronically and insulating of Li* ions.

2. Coated current collector (1) according to claim 1 such as said at least one layer (2) contains at least one material selected from the carbon, silicon and their mixtures.

3. Coated current collector (1) according to claim 1 such as said layer (2) contains at least one material selected from chromium, chromium oxide or nickel oxide or stainless steel.

4. Coated current collector (1) according to any one of the claims previous indications such that said layer (2) is resin-free fluorinated and / or oxalate.

5. Coated current collector (1) according to any one of the claims previous indications such as the material susceptible to corrosion is copper.

6. Method for preparing a coated current collector (1) according to one any of the preceding claims, including the filing of said layer (2) on the collector.

7. The method according to claim 5, wherein the deposit is carried out by depositing physical or chemical vapor deposition (PVD or CVD).

8. Electrode comprising a coated current collector (1) according to one any of the claims | to 4, such as said active material (3) of said electrode is graphite.

9. Electrochemical element comprising a coated current collector (1) according to any one of claims 1 to 4 and a solid electrolyte (4) of the sulfide type.

10. Electrochemical module comprising the stacking of at least two elements according to claim 8, each element being electrically connected trically with one or more other element(s).

11. | Battery comprising one or more modules according to claim 9.