Solid-state electrochemical cell and manufacturing process

Abstract

Solid-state electrochemical cell and manufacturing method. The invention relates to an electrochemical cell (10) comprising a stack (12) extending along a stacking direction (X), said stack comprising: an anodic layer (14); a cathodic layer (16); and a solid-state electrolyte layer (18), between the anodic layer and the cathodic layer along the stacking direction. The stack also comprises a pressure-resistant layer (20), composed of a polymer matrix and one or more lithium salts included in the polymer matrix, the pressure-resistant layer being located between the solid-state electrolyte layer (18) and the anodic layer (14) or the cathodic layer (16) along the stacking direction, said pressure-resistant layer preferably being located between the solid-state electrolyte layer (18) and the anodic layer (14). Figure: Figure 1

Description

Title of the invention: Solid-state electrochemical cell and manufacturing method

[0001] The present invention relates to an electrochemical cell, of the type comprising at least one stack extending along a stacking direction, said stack comprising: an anodic layer; a cathodic layer; and a layer of solid electrolyte, between the anodic layer and the cathodic layer along the stacking direction.

[0002] The invention is particularly applicable to solid-state electrochemical cells, not comprising a liquid electrolyte. Such a solid-state electrochemical cell is described in document EP4264697.

[0003] The anodic layers, particularly those comprising a silicon-based active material, can be subjected to significant volume variations during the operation of the electrochemical cell. Adhesion at the interface between the anodic layer and the solid-state electrolyte layer can therefore be affected.

[0004] The object of the present invention is to propose an improved electrochemical cell, particularly with regard to the mechanical adhesion between the anodic layer and the electrolyte layer in the solid state.

[0005] To this end, the invention relates to an electrochemical cell of the aforementioned type, in which the stacking also includes a first pressure-resistant layer, comprising a polymer matrix and one or more lithium salts included in the polymer matrix, the first pressure-resistant layer being located between the solid electrolyte layer and the anodic or cathodic layer along the stacking direction, said first pressure-resistant layer preferably being located between the solid electrolyte layer and the anodic layer.

[0006] In other advantageous aspects of the invention, the electrochemical cell comprises one or more of the following features, taken alone or in any technically feasible combination:

[0007] - the first pressure-resistant layer is in contact with both the layer anodic or cathodic and with the electrolyte layer in the solid state;

[0008] - the polymer matrix of the first pressure-resistant layer comprises: one among a poly(ionic liquid) or a polymer; and one among an ionic liquid or a plasticizer; the polymer matrix preferably comprising polydiallyldimethylammonium bis(fluorosulfonyl)imide plasticized by N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (Pyrl3FSI);

[0009] - the lithium salt(s) included in the polymer matrix are chosen from lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethane)sulfonimide, lithium hexafluorophosphate and lithium bis(oxalato)borate;

[0010] - a thickness of the pressure-resistant layer, along the direction of the stacking, is less than or equal to 20 pm, more preferably less than 10 pm, even more preferably less than 5 pm;

[0011] - the anodic layer comprises a material selected from silicon, alloys of silicon, silicon oxides, metallic lithium, lithium alloy, silicon carbon and composite silicon;

[0012] - the cathode layer comprises a solid electrolyte, preferably an electrolyte of sulfide; and more preferably comprises a mixture of NMC 811, sulfide electrolyte, PTFE binder and carbon;

[0013] - the solid-state electrolyte layer comprises a sulfide and composite polymer, said polymer preferably being PTFE;

[0014] - the first pressure-resistant layer is located between the electrolyte layer and the solid state and the anodic layer; and the stack also includes a second pressure-resistant layer between the solid-state electrolyte layer and the cathodic layer.

[0015] The invention also relates to a battery comprising at least one electrochemical cell as described above.

[0016] The invention will be better understood in the light of the following description, which is given by way of non-limiting example, with reference to the drawings, in which:

[0017] [Fig.1] Fig.1 is a schematic partial cross-sectional view of an electrochemical cell according to an embodiment of the invention.

[0018] Figure 1 shows a partial and schematic view of an electrochemical cell 10 according to an embodiment of the invention. The electrochemical cell 10 is designed to be part of a battery (not shown).

[0019] More specifically, the electrochemical cell 10 is a solid-state electrochemical cell, not comprising a liquid electrolyte.

[0020] The electrochemical cell 10 comprises at least one stack 12, extending along a stacking direction X. In one embodiment, the electrochemical cell 10 comprises a plurality of stacks 12, substantially identical and stacked along the stacking direction X.

[0021] The stack 12 comprises: an anodic layer 14; a cathodic layer 16; a solid electrolyte layer 18; and a first pressure-resistant layer 20. Optionally, the stack 12 also includes a second pressure-resistant layer 22, as in the embodiment of [Fig.1].

[0022] Preferably, the anodic layer 14 comprises a material selected from silicon, silicon alloys, silicon oxides, metallic lithium, lithium alloy, silicon carbon, composite silicon, and their pre-lithianed versions, as detailed below. A silicon-based anodic layer may further comprise a solid electrolyte and / or a binder and / or a conductive additive.

[0023] Preferably, the anodic layer 14 is a thin electrode; in other words, a thickness of the anodic layer 14, along the stacking direction X, is preferably less than or equal to 50 pm, more preferably less than or equal to 25 pm.

[0024] Preferably, the cathode layer 16 comprises a solid electrolyte, more preferably a sulfide electrolyte.

[0025] Preferably, the cathode layer 16 comprises a cathode active material, comprising at least one of the following compounds: lithium nickel cobalt manganese oxide (NMC), lithium iron phosphate (LFP), lithium iron manganese phosphate (LMFP), lithium nickel manganese spinel (LNMO), lithium nickel cobalt aluminum oxide (NCA), lithium manganese oxide (LMO), lithium cobalt oxide (LCO), lithium titanate (LTO), lithium transition metal borates, or lithium vanadium phosphate. The cathode active material may also comprise coatings of lithium niobium oxides, lithium silicon oxides, or the like.

[0026] More preferably, the cathode layer 16 is of the NMC type and comprises nickel, manganese, and cobalt. In a preferred embodiment, the first cathode layer 16 is an NMC 811 cathode.

[0027] Preferably, the cathode layer 16 also comprises a conductive material, more preferably carbon-based. Said conductive material may comprise carbon black, conductive graphite, NTC, ethylene black, carbon fibers, graphene, or the like.

[0028] Preferably, the cathode layer 16 also comprises a binder. More preferably, the binder comprises PTFE (polytetrafluoroethylene). The binder may also comprise BR (butadiene rubber), NBR (nitrile butadiene rubber), HNBR (hydrogenated nitrile butadiene rubber), PVDF, SEBS (styrene ethylene butylene styrene), styrene butadiene rubber (SBR) (vinylidene difluoride), CMC (carboxymethylcellulose), etc.

[0029] A preferred composition of the cathode layer 16 is NMC 811 (75% to 87%) + sulfide electrolyte (10% to 25%) + binder (0.1% to 5%) + carbon (0.1% to 5%). A more preferred composition is NMC 811 (80%) + sulfide electrolyte (18%) + PTFE binder (1%) + VGCF carbon nanofiber (1%). The percentages are weight percentages.

[0030] Preferably, the cathode layer 16 is a thick electrode; in other words, a thickness of the cathode layer 16, along the stacking direction X, is preferably greater than or equal to 80 pm, more preferably between 80 pm and 150 pm, even more preferably between 90 pm and 120 pm.

[0031] The solid-state electrolyte layer 18 is located between the anodic layer 14 and the cathodic layer 16 along the stacking direction Z.

[0032] Preferably, the solid-state electrolyte layer 18 comprises a material selected from a sulfide electrolyte and a sulfide-polymer composite, said polymer being more preferably PTFE. The sulfide-based solid-state electrolyte is more preferably selected from lithium-germanium-phosphorus sulfide, lithium-silicon-phosphorus sulfide, lithium-phosphorus sulfide, lithium-phosphorus-sulfur chloride, lithium-argyrodite-like material, lithium-tin sulfide, and their derivatives.

[0033] Preferably, the solid-state electrolyte layer 18 comprises between 95% and 99.9% sulfide electrolyte. A preferred composition of the solid-state electrolyte layer 18 is sulfide (99%) + PTFE (1%), the percentages being expressed by weight.

[0034] A thickness of the solid-state electrolyte layer 18, along the stacking direction X, is preferably less than 50 pm and more preferably less than or close to 30 pm.

[0035] The first pressure-resistant layer 20 is located between the solid electrolyte layer 18 and the anodic layer 14 or cathodic layer 16, along the stacking direction X. Preferably, the pressure-resistant layer 20 is in contact with both the solid electrolyte layer 18 and the anodic layer 14 or cathodic layer 16.

[0036] Preferably, the first pressure-resistant layer 20 is located between the solid electrolyte layer 18 and the anodic layer 14.

[0037] In the embodiment presented, the stack 12 also includes a second pressure-resistant layer 22, in contact with both the solid-state electrolyte layer 18 and the cathode layer 16. In another embodiment (not illustrated), the stack 12 does not include the second pressure-resistant layer 22 and the solid-state electrolyte layer 18 is in contact with the cathode layer 16.

[0038] The first 20 and the second 22 pressure-resistant layers will be described simultaneously below, under the designation "pressure-resistant layer 20, 22".

[0039] The pressure-resistant layer 20, 22 comprises a polymer matrix and one or more lithium salts included in the polymer matrix.

[0040] Preferably, the polymer matrix of the pressure-resistant layer 20, 22 is based on a poly(ionic liquid), plasticized by an ionic liquid or by solvents. More preferably, the polymer matrix of the pressure-resistant layer 20, 22 is a poly(ionic liquid) / ionic liquid (PIL / IL) pair whose proportions are adjusted to obtain key values ​​of mechanical strength and ionic conductivity.

[0041] Preferably, the poly(ionic liquid) comprises a compound selected from polydiallyldimethylammonium bis(fluorosulfonyl)imide (PDADMAF), poly(acrylamide-co-diallyldimethylammonium bis(fluorosulfonyl)imide) (P(AAm-co-DADMAF), poly(diallyldimethylammonium chloride) (PDADMAC) and poly(acrylamide-co-diallyldimethylammonium) (P(AAm-co-DADMAC). A more preferred compound is polydiallyldimethylammonium bis(fluorosulfonyl)imide (PDADMAF).

[0042] Preferably, the ionic liquid of the polymer matrix comprises a compound selected from N-propyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide (Pyrl3FSI), BMPyrr-FSI, BMPyrr-TFSI, BMIM-FSI, BMIM-TFSI and a combination thereof.

[0043] Preferably, the lithium salt(s) included in the polymer matrix of the pressure-resistant layer 20, 22 are chosen from lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethane)sulfonamide (LiTFSI), lithium hexafluorophosphate (LiPF6) and lithium bis(oxalato)borate (LiBOB).

[0044] According to one embodiment, the pressure-resistant layer 20, 22 also includes a mechanical reinforcement such as a secondary polymer with mechanical properties, such as Poly(vinylidene-co-hexafluoropropylene fluoride) (PVDF-HFP), and / or inorganic fillers such as aluminium nitride (AIN).

[0045] According to one embodiment, the pressure-resistant layer 20, 22 is in the form of a mixture or a semi-interpenetrating network of the Li conductive polymer matrix described above and a secondary polymer selected from poly(ethylene oxide) (PEO), polypropylene oxide (PPO), poly(acrylonitrile) (PAN), poly(methyl methacrylate) (PMMA), poly(vinylidene fluoride) (PVdF), poly(bis-methoxyethoxyethoxide), phosphazene, polyvinyl chloride, polydimethylsiloxane, poly(vinylidene fluoride)-hexafluoropropylene (PVDF-HFP), a derivative thereof, such as sulfonated versions, and a combination thereof.

[0046] According to one embodiment, the pressure-resistant layer 20, 22 also comprises an organic plasticizer or an agent for improving chemical and processing compatibility, such as polyethylene glycol dimethacrylate. (PEGDMA), succinonitrile (SN), glutaronitrile (GN), PEG, PEGDME, or a combination thereof.

[0047] Preferably, a thickness 24 of the pressure-resistant layer 20, 22, along the stacking direction X, is less than or equal to 20 µm. More preferably, the thickness 24 is less than 10 µm, and even more preferably less than 5 µm.

[0048] According to one embodiment, a Young's modulus of the pressure-resistant layer 20, 22 is less than 10 GPa. According to another embodiment, said Young's modulus of the pressure-resistant layer 20 is less than the Young's modulus of the anodic layer 14 and less than the Young's modulus of the solid-state electrolyte layer 18.

[0049] In one embodiment, the stack 12 also includes an anodic current collector (not shown) having electrical conductivity and coupled to the anodic layer 14, so as to form the anode of the electrochemical cell. The anodic current collector may comprise at least one material selected from indium, copper, magnesium, aluminum, stainless steel, iron, nickel, and their carbon-coated versions.

[0050] In one embodiment, the stack 12 also includes a cathode current collector (not shown) having electrical conductivity and coupled to the cathode layer 16, so as to form the cathode of the electrochemical cell. The cathode current collector may comprise at least one material selected from indium, copper, magnesium, aluminum, stainless steel, iron, and their carbon-coated versions.

[0051] A manufacturing process for the electrochemical cell 10 will now be described. In particular, a manufacturing process for the stack 12 will now be described.

[0052] In the considered embodiment of the electrochemical cell 10, the stack 12 does not include the second pressure-resistant layer 22 and the solid-state electrolyte layer 18 is in contact with the cathode layer 16.

[0053] According to a first embodiment, the manufacturing process comprises a first step in which: the first pressure-resistant layer 20 is assembled with the anodic layer 14, forming a first stacking element; and the solid electrolyte layer 18 is coated onto the cathodic layer 16, thus forming a second stacking element. The manufacturing process also comprises: a second step in which the first and second stacking elements thus formed are assembled; and a third step in which the resulting intermediate stack is densified under pressure to form the stack 12.

[0054] The process for preparing the first pressure-resistant layer 20 is not particularly limited. However, it may be preferable to coat the first layer pressure resistant 20 on the anodic layer 14, by a deposition process such as PVD, CVD, PECVD, spraying or similar.

[0055] According to a second embodiment, the manufacturing process comprises: a first step, in which the solid electrolyte layer 18 and the cathodic layer 16 are laminated together and densified together; a second step, in which the first pressure-resistant layer 20 is assembled to the anodic layer 14; and a third step of assembling the elements obtained.

[0056] Such a manufacturing process provides an electrochemical cell 10 in which adhesion at the interface of the anodic layer is reliable, even when a 100% Si anodic layer is used. Indeed, 100% Si electrodes are subject to significant expansion and contraction of their volume during charging and discharging. The first pressure-resistant layer 20 absorbs the mechanical stress of the Si electrode, thus creating a conformal contact between the anodic layer 14 and the solid-state electrolyte layer 18.

[0057] Consequently, the stacking pressure required for a battery comprising the electrochemical cell 10 is lower than in the prior art. For example, such a stacking pressure is less than or close to 1 MPa.

[0058] In addition, the first pressure-resistant layer 20 effectively dampens the chemical-mechanical effects of the Si anode and the solid-state sulfide electrolyte.

[0059] In parallel, the pressure-resistant layers 20, 22 protect the solid-state electrolyte layer 18 from mechanical, chemical and electrochemical decomposition.

[0060] In addition, the first pressure-resistant layer 20 ensures high ionic kinetics and conductivity on the interface with the anodic layer 14. For example, an ionic conductivity of a pressure-resistant layer 20 according to an embodiment of the invention is greater than 10⁴ S / cm. List of documents cited

[0061] 10: Electrochemical cell

[0062] 12: Stacking

[0063] 14: Anodic layer

[0064] 16: Cathode layer

[0065] 18: Solid-state electrolyte layer

[0066] 20: First pressure-resistant layer

[0067] 22: Second pressure-resistant layer

[0068] 24: Thickness of the first pressure-resistant layer

Claims

Demands

1. Electrochemical cell (10) comprising at least one stack (12) extending along a stacking direction (X), said stack comprising: an anodic layer (14); a cathodic layer (16); and a solid electrolyte layer (18), between the anodic layer and the cathodic layer along the stacking direction; the electrochemical cell being characterized in that the stack also comprises a first pressure-resistant layer (20), comprising a polymer matrix and one or more lithium salts included in the polymer matrix, the first pressure-resistant layer being located between the solid electrolyte layer (18) and the anodic layer (14) or the cathodic layer (16) along the stacking direction, said first pressure-resistant layer preferably being located between the solid electrolyte layer (18) and the anodic layer (14).

2. Electrochemical cell according to claim 1, wherein the first pressure-resistant layer (20) is in contact with both the anodic layer (14) or cathodic layer (16) and the solid-state electrolyte layer (18).

3. Electrochemical cell according to claim 1 or 2, wherein the polymer matrix of the first pressure-resistant layer (20) comprises: a poly(ionic liquid) or a polymer; and one of an ionic liquid or a plasticizer; the polymer matrix preferably comprising polydiallyldimethylammonium bis(fluorosulfonyl)imide plasticized with N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (Pyrl3FSI).

4. Electrochemical cell according to any one of the preceding claims, wherein the lithium salt(s) included in the polymer matrix are selected from lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethane)sulfonimide, lithium hexafluorophosphate and lithium bis(oxalato)borate.

5. Electrochemical cell according to any one of the preceding claims, wherein a thickness (24) of the pressure-resistant layer (20), along the stacking direction (X), is less than or equal to 20 pm, more preferably less than 10 pm, even more preferably less than 5 pm.

6. Electrochemical cell according to any one of the preceding claims, wherein the anodic layer (14) comprises a material selected from silicon, silicon alloys, silicon oxides, metallic lithium, lithium alloy, silicon carbon and composite silicon.

7. Electrochemical cell according to any one of the preceding claims, wherein the cathode layer (16) comprises a solid electrolyte, preferably a sulfide electrolyte; and more preferably comprises a mixture of NMC 811, sulfide electrolyte, PTFE binder and carbon.

8. Electrochemical cell according to any one of the preceding claims, wherein the solid-state electrolyte layer (18) comprises a sulfide and polymer composite, said polymer preferably being PTFE.

9. Electrochemical cell according to any one of the preceding claims, wherein: the first pressure-resistant layer is located between the solid electrolyte layer (18) and the anodic layer (14); and the stack (12) also comprises a second pressure-resistant layer (22) between the solid electrolyte layer (18) and the cathodic layer (16).

10. Battery comprising at least one electrochemical cell (10) according to any one of claims 1 to 9.

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