Electrodes comprising materials with a positive temperature coefficient (PTC)

Abstract

Electrode for a battery cell, comprising: a power collector; and a layer of active material arranged on the current collector, comprising the following: an active material with an outer coating layer comprising a material with a positive temperature coefficient (PTC); a conductive additive; and a binder, wherein the outer coating layer has a thickness in the range of 50 nm to 2 µm.

Description

INTRODUCTION

[0001] The information contained in this section serves to present the general context of the disclosure. Works of the inventors mentioned herein, insofar as they are described in this section, as well as aspects of the description that would not otherwise be considered prior art at the time of filing, are neither expressly nor implicitly admitted as prior art against the present disclosure.

[0002] The present disclosure relates to battery cells and in particular to electrodes and methods for manufacturing electrodes for battery cells.

[0003] Electric vehicles (EVs), such as battery electric vehicles (BEVs), hybrid vehicles, and / or fuel cell vehicles, comprise one or more electric motors and a battery system with one or more battery cells, modules, and / or packs. A power control system is used to manage the charging and / or discharging process of the battery system during charging and / or driving.

[0004] Battery cells include cathode electrodes, anode electrodes, and separators. The cathode electrodes comprise a layer of cathodically active material arranged on a cathode current collector. The anode electrodes comprise a layer of anodically active material arranged on an anode current collector.

[0005] Known electrodes for battery cells are described, for example, in US 2020 / 0 044 243 A1, CN 2 03 218 375 U, CN 1 13 651 612 A and JP 2016 - 134 217 A. SUMMARY

[0006] According to the invention, an electrode for a battery cell comprises a current collector and a layer of active material arranged on the current collector. The layer of active material includes an active material with an outer coating layer comprising a material with a positive temperature coefficient (PTC), a conductive additive, and a binder. The outer coating layer has a thickness in the range of 50 nm to 2 µm.

[0007] In other cases, the active material is in the range of 80 wt.% to 99 wt.%, the PTC material in the range of 0.5 wt.% to 20 wt.%, the conductive additive in the range of 0.5 wt.% to 20 wt.%, and the binder in the range of 0.5 wt.% to 10 wt.%. The active material is in the range of 80 wt.% to 99 wt.%, the PTC material in the range of 1 wt.% to 5 wt.%, the conductive additive in the range of 0.5 wt.% to 20 wt.%, and the binder in the range of 0.5 wt.% to 10 wt.%.

[0008] In other cases, the PTC material exhibits a Curie temperature in the range of 80 °C to 200 °C. The PTC material exhibits a Curie temperature in the range of 80 °C to 140 °C.

[0009] In other cases, the PTC material contains an inorganic material selected from a group consisting of metal oxides, BaTiO3, V2O5, and combinations thereof. The PTC material includes an organic material selected from a group consisting of polymethyl methacrylate (PMMA) or polydimethylsiloxane (PDMS).

[0010] In other cases, the PTC material is doped with one or more elements selected from the group consisting of lanthanum (La), cerium (Ce), antimony (Sb), yttrium (Y), tungsten (W), titanium (Ti), tantalum (Ta), niobium (Nb), cobalt (Co), chlorine (Cl), iodine (I), bromine (Br) and combinations thereof.

[0011] The outer coating layer has a thickness in the range of 200 nm to 500 nm.

[0012] Further applications of the present disclosure will become apparent from the detailed description, the claims, and the drawings. The detailed description and the specific examples serve only for illustration and are not intended to limit the scope of the disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present disclosure is better understood from the detailed description and the accompanying drawings; the following applies: Fig. Figure 1 is a side cross-sectional view of a battery cell with anode and cathode electrodes and separators according to the present disclosure; Fig. Figure 2 is a lateral cross-sectional view of a cathode electrode with a PTC-coated cathodically active material according to the present disclosure; Fig. Figure 3 is a lateral cross-sectional view of an anode electrode with a PTC-coated anodically active material according to the present disclosure; Fig. Figure 4 is a lateral cross-sectional view of a particle of active material with a PTC coating according to the present disclosure; Fig. Figure 5 is a lateral cross-sectional view of a cathode electrode with a layer of cathodically active material containing PTC material according to the present disclosure; Fig. Figure 6 is a lateral cross-sectional view of an anode electrode with a layer of anodically active material containing PTC material according to the present disclosure; Fig. Figure 7 is a lateral cross-sectional view of a cathode electrode with a PTC layer according to the present disclosure; Fig. Figure 8 is a lateral cross-sectional view of an anode electrode with a PTC layer according to the present disclosure; Fig. Figures 9A to 9D are flowcharts of the process for manufacturing an electrode with a layer of active material containing PTC material according to the present disclosure; Fig. Figure 10A is a diagram of the heat flow as a function of temperature for battery cells with and without PTC material according to the present disclosure; Fig. 10B and Fig. Figures 10C are diagrams showing the results of a verification of the formation cycle and C-rate for battery cells with and without PTC material according to the present disclosure.

[0014] Reference symbols can be used repeatedly in the drawings to identify similar and / or identical elements. DETAILED DESCRIPTION

[0015] Although the battery cells described in the present disclosure are related to vehicles, the battery cells can also be used in other applications, e.g. in stationary applications.

[0016] Battery cells can experience a rapid temperature increase if caused by objects penetrating the cell casing (e.g., a nail or other sharp object), heat propagation, and / or short circuits. This rapid temperature increase can lead to separator shrinkage, melting, and further short circuits. As can be seen, reducing heat generation due to short circuits can help prevent thermal runaway.

[0017] The present disclosure relates to electrodes containing a positive temperature coefficient (PTC) material whose resistance increases significantly at a Curie temperature in response to an elevated battery cell temperature. The PTC material can be used, for example, as a coating on particles of the active material, such as PTC particles mixed with the active material layer, and / or in a PTC layer between the active material layer and an adjacent separating layer.

[0018] As can be seen, the resistance of the PTC material increases significantly when the battery cell temperature rises above the Curie temperature. The PTC material can, for example, contain BaTiO3, which has a resistance of approximately 10 Ω up to about 100 °C. 1 Ohm, which then quickly rises to ~10 5The Curie temperature increases at 175 °C. In some examples, the Curie temperature of the PTC material is adjusted or lowered to a temperature below the melting temperature of the separator (e.g., less than 150 °C) by doping or using an additive.

[0019] In some examples, the resistance of the PTC material increases so dramatically in response to the elevated temperature that it effectively creates an open circuit. When the cell temperature rises above the Curie temperature of the PTC material, the resistance of the battery cell increases rapidly. This increased resistance reduces the current flow to prevent further temperature rise and / or suppresses or prevents short circuits.

[0020] In relation to Fig. 1 contains a battery cell 10, cathode electrodes 20, anode electrodes 40, and separators 32, arranged in a predetermined sequence in a battery cell stack 12, where C, S, and A are integers greater than zero. The battery cell stack 12 is arranged in a housing 50. The C cathode electrodes 20-1, 20-2, ..., and 20-C contain layers 24 of cathodically active material arranged on one or both sides of a cathode current collector 26.

[0021] In some examples, the A anode electrodes 40 and the C cathode electrodes 20 exchange lithium ions during charging / discharging. The A anode electrodes 40-1, 40-2, ... and 40-A contain layers 42 of anodically active material arranged on one or both sides of the anode current collectors 46. In some examples, the cathodically active material layers 24 and / or the anodically active material layers comprise a coating or self-supporting film with one or more active materials, one or more conductive additives, and / or one or more binder materials, which are cast or laminated onto the current collectors. The cathode electrodes and / or the anode electrodes contain a material with a positive temperature coefficient (PTC), as described below.

[0022] In some examples, the cathode current collector 26 and / or the anode current collector 46 comprise metal foil, metal mesh, perforated metal, three-dimensional (3D) metal foam, and / or expanded metal. In some examples, the current collectors are made of one or more materials selected from the group consisting of copper, stainless steel, brass, bronze, zinc, aluminum, and / or their alloys. The outer tabs 28 and 48 are connected to the current collectors of the cathode and anode electrodes, respectively, and can be located on the same side or on different sides of the battery cell stack 12. The outer tabs 28 and 48 are connected to the terminals of the battery cells.

[0023] Now, regarding Fig. 2 and Fig. Figure 3 shows examples of cathode and anode electrodes. Fig. Figure 2 shows the cathode electrode 20 in more detail. The layer 24 of cathodically active material of the cathode electrode 20 contains a cathodically active material 62 coated with a PTC material, as shown in Figure 2. Fig. 4 shown, an optional conductive additive 64 and an optional binder 66.

[0024] In Fig. Figure 3 shows the anode electrode 40 in more detail. The layer 42 of anodically active material of the anode electrode 40 contains an anodically active material 72 coated with a PTC material, as shown in Fig. 4 shown, an optional conductive additive 64 and an optional binder 66.

[0025] Now, regarding Fig. Figure 4 shows a particle 80 of the active material for a cathode or anode electrode coated with a PTC coating 84. In some examples, the PTC coating 84 interrupts the electronic pathways to the active material 80 at high temperatures in the range of 80 °C to 200 °C. In some examples, the PTC coating 84 interrupts the electronic pathways to the active material 80 at high temperatures in the range of 80 °C to 140 °C. According to the invention, the thickness of the PTC coating is in the range of 50 nm to 2 µm. In some examples, the thickness of the PTC coating is in the range of 200 nm to 500 nm.

[0026] Now, regarding Fig. 5 and Fig. 6. The cathode electrodes and / or anode electrodes may contain PTC material mixed with other materials in the active material layer. Fig. 5 contains the cathode electrode 20 the layer 24 of cathodically active material, which is mixed with PTC particles 90.

[0027] In Fig. Figure 6 contains the anode electrode 40, which comprises a layer 42 of anodically active material mixed with PTC particles 94. The PTC particles 90 and 94 act as a conductive filler at lower temperatures when the battery cell temperature is below the Curie temperature (e.g., 120 °C). When the battery cell temperature rises above the Curie temperature, the PTC material 90 and 94 act as electron blockers (due to their increased resistance) to shut down the battery cell and prevent further thermal problems. In some examples, the PTC particles 90 and 94 constitute 0.5 to 20 wt.% of the active material layer. In other examples, the PTC particles constitute 1 to 5 wt.% of the active material layer.

[0028] Now, regarding Fig. 7 and Fig. 8. A PTC layer can be used. Fig. Figure 7 contains the cathode electrode 20, which includes a PTC layer 110 arranged between the layer 24 of cathodically active material and an adjacent separator. Fig. Figure 8 shows that the anode electrode contains a PTC layer 114. The PTC layers 110 and / or 114 exhibit a significantly increased resistance at elevated temperatures to reduce or prevent short circuits. As can be seen, the cathode and / or anode electrodes can contain various combinations of the PTC material (e.g., the PTC coating of the active material, PTC particles in the active material, and / or the PTC layer between the active material and the adjacent separator).

[0029] Now, regarding Fig. Figure 9A shows a method for producing an electrode with a layer of active material containing PTC particles. Figure 320 describes mixing a slurry of active material, binder, and conductive filler with PTC particles. Figure 324 describes printing or casting the mixture onto a current collector. The mixture is printed, for example, using a gravure printing press or cast using a casting machine.

[0030] In Fig. Figure 9B describes a process for forming a PTC coating. The process involves dissolving a PTC precursor in a solution (e.g., solvent-based or aqueous) containing active material particles at 330. The solution is heated at 334 for a predetermined time and then cooled. The solid particles are filtered at 338 and optionally rinsed. The particles are then calcined at a predetermined temperature (e.g., 500 °C to 1000 °C) for a predetermined time at 342.

[0031] In Fig. Section 9C describes a process for coating an electrode with a PTC layer. The process involves mixing a slurry containing a PTC material and a binder at 350. The mixture is then printed or cast onto the electrode's active material layer at 354. For example, a gravure printing press or a casting machine can be used.

[0032] In Fig. Figure 9D shows another process for coating particles of active material with a PTC layer. The active material and the PTC material are mixed at 360° and arranged in a mechanical melting machine. The mechanical melting machine mechanically presses the PTC material into the active material, resulting in a coated active material at 364°.

[0033] In some examples, the active material layer of the electrode contains the active material in a range of 80 wt.% to 99 wt.%, the PTC material in a range of 0.5 wt.% to 20 wt.% (e.g., 1 wt.% to 5 wt.%), the conductive filler in a range of 0.5 wt.% to 20 wt.%, and the binder in a range of 0.5 wt.% to 10 wt.%. In some examples, the electrode load is in the range of 2 mAh / cm². 2 up to 10 mAh / cm 2 In some examples, the electrode load is in the range of 3 mAh / cm². 2 up to 6 mAh / cm 2 .

[0034] In some examples, the PTC material contains an inorganic material selected from a group consisting of metal oxides, BaTiO3, V2O5, and combinations thereof. In some examples, the PTC material also contains a dopant and / or an additive to adjust the Curie temperature. The PTC material may, for example, contain BaTiO3 with a dopant (e.g., lanthanum (La), cerium (Ce), antimony (Sb), yttrium (Y), tungsten (W), titanium (Ti), tantalum (Ta), niobium (Nb), cobalt (Co), chlorine (Cl), iodine (I), bromine (Br)) and / or an additive (e.g., SiO2, Al2O3). In some examples, the PTC material contains an organic material selected from a group consisting of polymethyl methacrylate (PMMA) or polydimethylsiloxane (PDMS). In some examples, doping and / or additives are used to lower the Curie temperature of the PTC material below 150 °C.

[0035] In some examples, the Curie temperature of the PTC material ranges from 80 °C to 200 °C. In some examples, the Curie temperature of the PTC material is less than 150 °C. In some examples, the Curie temperature of the PTC material ranges from 80 °C to 140 °C.

[0036] In some examples, the cathodically active material is selected from a group consisting of lithium nickel cobalt manganese (NCM), lithium nickel cobalt manganese aluminum (NCMA), lithium nickel cobalt aluminum oxide (NCA), lithium nickel manganese aluminum (NMA), nickel metal (NM), lithium nickel oxide (LNO), lithium iron phosphate (LFP), lithium manganese iron phosphate (MFMP), lithium cobalt oxide (LCO), and combinations thereof. In some examples, the morphology includes primary and secondary Ni-rich cathodes of the mono-sized particle type or the bimodal type. In some examples, D50 is in the range of 1 µm to 20 µm. In some examples, the primary type lies in a range of 3 µm to 6 µm and the secondary type in a range of 3 µm to 15 µm.

[0037] In some examples, the anodically active material is selected from a group consisting of graphite, hard carbon, lithium silicon oxide (LSO), silicon (Si), and silicon dioxide (SiO₂). x). In some examples, the morphology of the silicon-based material includes nanoparticles, nanofibers, nanotubes, and microparticles. In some examples, the conductive filler is selected from a group consisting of graphite, graphene, carbon black, graphene oxide, Super P, acetylene black, carbon nanofibers, carbon nanotubes, and combinations thereof.

[0038] In some examples, the binder is selected from a group consisting of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), CMS, styrene-butadiene rubber (SBR), polyacrylic acid (PAA), PAA-PHEA, and combinations thereof. In some examples, the PAA is replaced by sodium hydroxide (NaOH) or lithium hydroxide (LiOH), sodium polyacrylate (PAANa), PAAH 0.2 N 0.8 or lithium polyacrylic acid (LiPAA) neutralized.

[0039] In relation to Fig. Figure 10A shows a diagram of the heat flow as a function of temperature for a battery cell with a cathode electrode containing the PTC material, compared to the same battery cell without the PTC material. In this example, the cathodically active material is NCMA and the anodically active material is graphite. The cathodically active material layer contains the cathodically active material (e.g., NCMA), the PTC material, the conductive additive (e.g., Super P), and the binder (e.g., PVDF) in a ratio of 86 / 10 / 2 / 2 wt% (or 96 / 2 / 2 if no PTC material is used). Peak strength occurs at ~220°C and decreases from ~15 W / g to ~5 W / g.

[0040] In relation to Fig. 10B and Fig. Figure 10C shows a verification of the formation cycle and capacity rate of battery cells with and without PTC material. The tests illustrate a comparable performance of the battery cells with and without PTC material. Fig. In 10C, part of the active material was replaced by the PTC material, which has higher conductivity and provides better performance at some charging speeds (e.g. 2C) and comparable performance at other charging speeds.

[0041] Spatial and functional relationships between elements (e.g., between modules, circuit elements, semiconductor layers, etc.) are described using various terms, including "connected," "interlocking," "coupled," "adjacent," "next to," "on top of," "above," "below," and "arranged." If a relationship between first and second elements is not explicitly described as "direct" in the above disclosure, this relationship may be a direct relationship, in which no other intervening elements exist between the first and second elements, or an indirect relationship, in which one or more intervening elements (either spatial or functional) exist between the first and second elements.As used herein, the expression “A, B and / or C” should be interpreted using a non-exclusive logical OR operation as logical (A OR-connected with B OR-connected with C) and not as “at least one of A, at least one of B and at least one of C”.

[0042] In the diagrams, the direction of an arrow, as indicated by its tip, generally illustrates the flow of information (e.g., data or instructions) that is relevant to the illustration. For example, if Element A and Element B exchange a variety of information, but the information transferred from Element A to Element B is relevant for the illustration, the arrow may point from Element A to Element B. This unidirectional arrow does not mean that no other information is transferred from Element B to Element A. Furthermore, in the context of information sent from Element A to Element B, Element B may send requests for or acknowledgments of the information to Element A.

Claims

[1] Electrode for a battery cell comprising: a power collector; and a layer of active material arranged on the current collector, comprising the following: an active material with an outer coating layer comprising a material with a positive temperature coefficient (PTC); a conductive additive; and a binder, wherein the outer coating layer has a thickness in the range of 50 nm to 2 µm. [2] Electrode according to claim 1, wherein the active material is in a range of 80 wt.% to 99 wt.%, the PTC material is in a range of 0.5 wt.% to 20 wt.%, the conductive additive is in a range of 0.5 wt.% to 20 wt.% and the binder is in a range of 0.5 wt.% to 10 wt.%. [3] Electrode according to claim 1, wherein the active material is in a range of 80 wt.% to 99 wt.%, the PTC material is in a range of 1 wt.% to 5 wt.%, the conductive additive is in a range of 0.5 wt.% to 20 wt.% and the binder is in a range of 0.5 wt.% to 10 wt.%. [4] Electrode according to claim 1, wherein the PTC material has a Curie temperature in the range of 80 °C to 200 °C. [5] Electrode according to claim 1, wherein the PTC material has a Curie temperature in the range of 80 °C to 140 °C. [6] Electrode according to claim 1, wherein the PTC material comprises an inorganic material selected from the group consisting of metal oxide, BaTiO3, V2O5 and combinations thereof. [7] Electrode according to claim 1, wherein the PTC material comprises an organic material selected from the group consisting of polymethyl methacrylate (PMMA) or polydimethylsiloxane (PDMS). [8] Electrode according to claim 1, wherein the PTC material is doped with one or more elements selected from the group consisting of lanthanum (La), cerium (Ce), antimony (Sb), yttrium (Y), tungsten (W), titanium (Ti), tantalum (Ta), niobium (Nb), cobalt (Co), chlorine (Cl), iodine (I), bromine (Br) and combinations thereof. [9] Electrode according to claim 1, wherein the outer coating layer has a thickness in the range of 200 nm to 500 nm.

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