Electrodes comprising positive temperature coefficient (PTC) materials

Abstract

The invention relates to an electrode comprising a positive temperature coefficient (PTC) material. An electrode for a battery cell includes a current collector and an active material layer disposed on the current collector. In some examples, the active material layer includes an active material, a conductive additive, a positive temperature coefficient (PTC) material, and a binder. In other examples, the active material layer includes an active material having an overcoat layer including a PTC material. In other examples, the PTC layer is disposed on the active material layer.

Description

Technical Field

[0001] The present disclosure relates to battery cells for a battery pack, and more particularly to electrodes and methods for fabricating electrodes for battery cells of a battery pack. Background Art

[0002] The information provided in this section is intended to generally introduce the background of the present disclosure. To the extent that the work currently attributed to the inventors is described in this section, and aspects of the specification that may not otherwise be determined to be prior art at the time of filing, are not expressly or implicitly admitted to be prior art against the present disclosure.

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

[0004] A battery cell includes a cathode electrode, an anode electrode, and a separator. The cathode electrode includes a cathode active material layer disposed on a cathode current collector. The anode electrode includes an anode active material layer disposed on an anode current collector. Summary of the Invention

[0005] An electrode for a battery cell includes a current collector and an active material layer disposed on the current collector. The active material layer includes an active material, a conductive additive, a positive temperature coefficient (PTC) material, and a binder.

[0006] In other features, the active material is 80 wt% to 99 wt%, the PTC material is 0.5 wt% to 20 wt%, the conductive additive is 0.5 wt% to 20 wt%, and the binder is 0.5 wt% to 10 wt%. The active material is 80 wt% to 99 wt%, the PTC material is 1 wt% to 5 wt%, the conductive additive is 0.5 wt% to 20 wt%, and the binder is 0.5 wt% to 10 wt%.

[0007] In other features, the Curie temperature of the PTC material is between 80°C and 200°C. The Curie temperature of the PTC material is between 80°C and 140°C.

[0008] In other features, the PTC material includes an inorganic material selected from metal oxides, BaTiO3, V2O5, and combinations thereof. The PTC material includes an organic material selected from polymethyl methacrylate (PMMA) or polydimethylsiloxane (PDMS).

[0009] Among other features, the PTC material is doped with one or more elements selected from 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.

[0010] An electrode for a battery cell of a battery pack includes a current collector and an active material layer disposed on the current collector. The active material layer contains an active material, and the active material includes an outer coating that contains a positive temperature coefficient (PTC) material, a conductive additive, and a binder.

[0011] Among other features, the Curie temperature of the PTC material is between 80 °C and 200 °C. The Curie temperature of the PTC material is between 80 °C and 140 °C. The PTC material includes an inorganic material selected from metal oxides, BaTiO3, V2O5, and combinations thereof. The PTC material includes an organic material selected from polymethyl methacrylate (PMMA) or polydimethylsiloxane (PDMS). The thickness of the outer coating is between 50 nm and 2 μm. The thickness of the outer coating is between 200 nm and 500 nm.

[0012] An electrode for a battery cell of a battery pack includes a current collector and an active material layer disposed on the current collector. The active material layer contains an active material, a conductive additive, and a binder. The positive temperature coefficient (PTC) layer is disposed on the active material layer and contains a PTC material.

[0013] Among other features, the Curie temperature of the PTC material is between 80 °C and 200 °C. The Curie temperature of the PTC material is between 80 °C and 140 °C.

[0014] The PTC material includes an inorganic material selected from metal oxides, BaTiO3, V2O5, and combinations thereof. The PTC material includes an organic material selected from polymethyl methacrylate (PMMA) or polydimethylsiloxane (PDMS).

[0015] The present invention discloses the following solutions:

[0016] Solution 1. An electrode for a battery cell of a battery pack, the electrode comprising:

[0017] A current collector; and

[0018] An active material layer disposed on the current collector, the active material layer containing:

[0019] An active material;

[0020] A conductive additive;

[0021] A positive temperature coefficient (PTC) material; and

[0022] Binder.

[0023] Solution 2. The electrode according to Solution 1, wherein the active material is 80% to 99% by weight, the PTC material is 0.5% to 20% by weight, the conductive additive is 0.5% to 20% by weight, and the binder is 0.5% to 10% by weight.

[0024] Solution 3. The electrode according to Solution 1, wherein the active material is 80% to 99% by weight, the PTC material is 1% to 5% by weight, the conductive additive is 0.5% to 20% by weight, and the binder is 0.5% to 10% by weight.

[0025] Solution 4. The electrode according to Solution 1, wherein the Curie temperature of the PTC material is between 80°C and 200°C.

[0026] Solution 5. The electrode according to Solution 1, wherein the Curie temperature of the PTC material is between 80°C and 140°C.

[0027] Solution 6. The electrode according to Solution 1, wherein the PTC material includes inorganic materials selected from metal oxides, BaTiO3, V2O5, and combinations thereof.

[0028] Solution 7. The electrode according to Solution 1, wherein the PTC material includes organic materials selected from polymethyl methacrylate (PMMA) or polydimethylsiloxane (PDMS).

[0029] Solution 8. The electrode according to Solution 1, wherein the PTC material is doped with one or more elements selected from 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.

[0030] Solution 9. An electrode for a battery cell of a battery pack, the electrode comprising:

[0031] A current collector; and

[0032] An active material layer disposed on the current collector, the active material layer comprising:

[0033] An active material, which includes an outer coating containing a positive temperature coefficient (PTC) material; a conductive additive; and

[0034] Binder.

[0035] Solution 10. The electrode according to Solution 9, wherein the Curie temperature of the PTC material is between 80°C and 200°C.

[0036] Solution 11. The electrode according to Solution 9, wherein the Curie temperature of the PTC material is between 80 °C and 140 °C.

[0037] Solution 12. The electrode according to Solution 9, wherein the PTC material comprises an inorganic material selected from metal oxides, BaTiO3, V2O5, and combinations thereof.

[0038] Solution 13. The electrode according to Solution 9, wherein the PTC material comprises an organic material selected from polymethyl methacrylate (PMMA) or polydimethylsiloxane (PDMS).

[0039] Solution 14. The electrode according to Solution 9, wherein the thickness of the outer coating is between 50 nm and 2 μm.

[0040] Solution 15. The electrode according to Solution 9, wherein the thickness of the outer coating is between 200 nm and 500 nm.

[0041] Solution 16. An electrode for a battery cell of a battery pack, the electrode comprising:

[0042] A current collector;

[0043] An active material layer disposed on the current collector, the active material layer comprising:

[0044] Active material;

[0045] A conductive additive; and

[0046] A binder; and

[0047] A positive temperature coefficient (PTC) layer disposed on the active material layer comprising the PTC material.

[0048] Solution 17. The electrode according to Solution 16, wherein the Curie temperature of the PTC material is between 80 °C and 200 °C.

[0049] Solution 18. The electrode according to Solution 16, wherein the Curie temperature of the PTC material is between 80 °C and 140 °C.

[0050] Solution 19. The electrode according to Solution 16, wherein the PTC material comprises an inorganic material selected from metal oxides, BaTiO3, V2O5, and combinations thereof.

[0051] Solution 20. The electrode according to Solution 16, wherein the PTC material comprises an organic material selected from polymethyl methacrylate (PMMA) or polydimethylsiloxane (PDMS).

[0052] Further applicable fields of the present disclosure will be apparent from the detailed description, the claims, and the drawings. The detailed description and specific examples are only intended to be illustrative and are not intended to limit the scope of the present disclosure. Description of the Drawings

[0053] The present disclosure is more fully understood from the detailed description and the drawings, in which:

[0054] Figure 1 is a side cross-sectional view of a battery cell of a battery pack including an anode electrode, a cathode electrode, and a separator according to the present disclosure;

[0055] Figure 2 is a side cross-sectional view of a cathode electrode including a PTC-coated cathode active material according to the present disclosure;

[0056] Figure 3 is a side cross-sectional view of an anode electrode including a PTC-coated anode active material according to the present disclosure;

[0057] Figure 4 is a side cross-sectional view of an active material particle having a PTC coating according to the present disclosure;

[0058] Figure 5 is a side cross-sectional view of a cathode electrode including a cathode active material layer containing a PTC material according to the present disclosure;

[0059] Figure 6 is a side cross-sectional view of an anode electrode including an anode active material layer containing a PTC material according to the present disclosure;

[0060] Figure 7 is a side cross-sectional view of a cathode electrode including a PTC layer according to the present disclosure;

[0061] Figure 8 is a side cross-sectional view of an anode electrode including a PTC layer according to the present disclosure;

[0062] Figure 9A , 9B , 9C and 9D are flowcharts of a method for manufacturing an electrode including an active material layer containing a PTC material according to the present disclosure;

[0063] Figure 10A is a graph of the heat flow of a battery cell with and without a PTC material as a function of temperature according to the present disclosure;

[0064] Figure 10B and 10CIt is a graph showing the results of formation cycle check and C-rate check of battery cells of a battery pack with and without PTC material according to the present disclosure.

[0065] In the drawings, reference numerals may be reused to identify similar and / or identical elements. Detailed Description

[0066] Although the battery cells of the battery pack according to the present disclosure are described in the context of a vehicle, the battery cells can be used in other applications such as stationary applications.

[0067] When the battery cell housing is pierced (e.g., by a nail or other sharp object), heat propagation, and / or short circuit is triggered, the battery cell experiences a rapid temperature increase. The rapid temperature increase can cause the separator to shrink, melt, and additional short circuits. It can be understood that reducing the heat generation due to short circuits can be used to prevent thermal runaway.

[0068] The present disclosure relates to an electrode containing a positive temperature coefficient (PTC) material that experiences a significant increase in resistance at the Curie temperature in response to an elevated battery cell temperature. For example, the PTC material can be used as a coating on the active material particles, as PTC particles mixed with the active material layer, and / or in a PTC layer between the active material layer and the adjacent separator layer.

[0069] It can be understood that when the temperature of the battery cell rises above the Curie temperature, the resistance of the PTC material significantly increases. For example, the PTC material can include BaTiO3, which has a resistance of ∼10 1 ohms at up to about 100 °C and then rapidly increases to ∼10 5 ohms at 175 °C. In some instances, the Curie temperature of the PTC material is adjusted or reduced to a temperature below the melting temperature of the separator (e.g., below 150 °C) by doping or using additives.

[0070] In some instances, the resistance of the PTC material increases sufficiently in response to the elevated temperature to create an effective open circuit. When the battery temperature rises above the Curie temperature of the PTC material, the resistance of the battery cell rapidly increases. The increased resistance reduces the current to prevent further temperature increase and / or inhibit or prevent short circuits.

[0071] Now refer to Figure 1, the battery cell 10 of the battery pack includes C cathode electrodes 20, A anode electrodes 40, and S separators 32 arranged in a predetermined order in the battery cell stack 12, where C, S, and A are integers greater than zero. The battery cell stack 12 is disposed in the housing 50. The C cathode electrodes 20-1, 20-2, ..., and 20-C include cathode active material layers 24 disposed on one or both sides of the cathode current collector 26.

[0072] 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 include anode active material layers 42 disposed on one or both sides of the anode current collector 46. In some examples, the cathode active material layer 24 and / or the anode active material layer includes a coating or a self-standing film that includes one or more active materials, one or more conductive additives, and / or one or more binder materials cast or laminated onto the current collector. The cathode electrode and / or the anode electrode incorporates a positive temperature coefficient (PTC) material, as will be further described below.

[0073] In some examples, the cathode current collector 26 and / or the anode current collector 46 includes a metal foil, a metal mesh, a perforated metal, a three-dimensional (3D) metal foam, and / or an expanded metal plate. In some examples, the current collector is made of one or more materials selected from copper, stainless steel, brass, bronze, zinc, aluminum, and / or their alloys. The external tabs 28 and 48 are respectively connected to the current collectors of the cathode electrode and the anode electrode, and may be disposed on the same side or different sides of the battery cell stack 12. The external tabs 28 and 48 are connected to the terminals of the battery cell.

[0074] Now refer to Figure 2 and Figure 3 , examples of the cathode electrode and the anode electrode are shown. In Figure 2 , the cathode electrode 20 is shown in further detail. The cathode active material layer 24 of the cathode electrode 20 includes a cathode active material 62 coated with a PTC material as shown in Figure 4 , an optional conductive additive 64, and an optional binder 66.

[0075] In Figure 3 , the anode electrode 40 is shown in further detail. The anode active material layer 42 of the anode electrode 40 includes an anode active material 72 coated with a PTC material as shown in Figure 4 , an optional conductive additive 64, and an optional binder 66.

[0076] Now refer to Figure 4, which shows that the active material particles 80 for the cathode electrode or the anode electrode are coated with a PTC coating 84. In some instances, the PTC coating 84 closes the electronic path to the active material 80 at a high temperature of 80 °C to 200 °C. In some instances, the PTC coating 84 closes the electronic path to the active material 80 at a high temperature of 80 °C to 140 °C. In some instances, the thickness of the PTC coating is between 50 nm and 2 μm. In some instances, the thickness of the PTC coating is between 200 nm and 500 nm.

[0077] Now refer to Figure 5 and Figure 6 , the cathode electrode and / or the anode electrode may include a PTC material mixed with other materials in the active material layer. In Figure 5 , the cathode electrode 20 includes a cathode active material layer 24 mixed with PTC particles 90.

[0078] In Figure 6 , the anode electrode 40 includes an anode active material layer 42 mixed with PTC particles 94. When the battery pack cell temperature is below the Curie temperature (e.g., 120 °C), the PTC particles 90 and 94 act as conductive fillers at a lower temperature. When the temperature of the battery pack cell rises above the Curie temperature, the PTC materials 90 and 94 are used as an electronic blocker (due to increased resistance) to shut down the battery pack cell and prevent further thermal problems. In some instances, the PTC particles 90 and 94 account for 0.5% to 20% by weight of the active material layer. In some instances, the PTC particles account for 1% to 5% by weight of the active material layer.

[0079] Now refer to Figure 7 and Figure 8 , a PTC layer can be used. In Figure 7 , the cathode electrode 20 includes a PTC layer 110 disposed between the cathode active material layer 24 and an adjacent separator. In Figure 8 , the anode electrode includes a PTC layer 114. The PTC layers 110 and / or 114 have a significantly increased resistance at elevated temperatures to reduce or prevent short circuits. It can be understood that the cathode electrode and / or the anode electrode can incorporate different combinations of PTC materials (e.g., a PTC coating on the active material, PTC particles in the active material, and / or a PTC layer between the active material and an adjacent separator).

[0080] Now refer to Figure 9A , which shows a method for manufacturing an electrode including an active material layer containing PTC particles. At 320, a slurry containing an active material, a binder, and a conductive filler is mixed with PTC particles. At 324, the mixture is printed or cast onto a current collector. For example, the mixture is printed using a gravure printing press or cast using a casting machine.

[0081] In Figure 9B , a method for forming a PTC coating is shown. The method includes dissolving a PTC precursor in a solution (e.g., solvent-based or aqueous) containing active material particles at 330. The solution is heated for a predetermined time at 334 and then cooled. The solid particles are filtered at 338 and optionally rinsed. The particles are calcined at a predetermined temperature (e.g., 500 °C to 1000 °C) for a predetermined time at 342.

[0082] In Figure 9C , a method for coating a PTC layer on an active material layer of an electrode is shown. The method includes mixing a slurry containing a PTC material and a binder at 350. At 354, the mixture is printed or cast onto the active material layer of the electrode. For example, a gravure printing press or a casting machine can be used.

[0083] In Figure 9D , another method for coating a PTC layer on active material particles is shown. The active material and the PTC material are mixed at 360 and placed in a mechanical fusion machine. At 364, the mechanical fusion machine mechanically presses the PTC material into the active material to produce coated active material.

[0084] In some examples, the active material layer of the electrode includes 80 wt% to 99 wt% of active material, 0.5 wt% to 20 wt% (e.g., 1 wt% to 5 wt%) of PTC material, 0.5 wt% to 20 wt% of conductive filler, and 0.5 wt% to 10 wt% of binder. In some examples, the loading of the electrode is 2 mAh / cm 2 to 10 mAh / cm 2 . In some examples, the loading of the electrode is 3 mAh / cm 2 to 6 mAh / cm 2 .

[0085] In some examples, the PTC material includes inorganic materials selected from metal oxides, BaTiO3, V2O5, and combinations thereof. In some examples, the PTC material further includes doping elements and / or additives to adjust the Curie temperature. For example, the PTC material can include BaTiO3 with doping elements (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 additives (e.g., SiO2, Al2O3). In some examples, the PTC material includes organic materials selected from polymethyl methacrylate (PMMA) or polydimethylsiloxane (PDMS). In some examples, the doping elements and / or additives are used to reduce the Curie temperature of the PTC material to below 150 °C.

[0086] In some instances, the Curie temperature of the PTC material is from 80 °C to 200 °C. In some instances, the Curie temperature of the PTC material is below 150 °C. In some instances, the Curie temperature of the PTC material is from 80 °C to 140 °C.

[0087] In some instances, the cathode active material is selected from 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 instances, the morphology includes primary and secondary single particle size types or bimodal nickel-rich cathodes. In some instances, the D50 is from 1 μm to 20 μm. In some instances, the primary type is from 3 μm to 6 μm and the secondary type is from 3 μm to 15 μm.

[0088] In some instances, the anode active material is selected from graphite, hard carbon, lithium silicon oxide (LSO), silicon (Si), and silicon oxide (SiO x ). In some instances, the morphology of the silicon-based material includes nanoparticles, nanofibers, nanotubes, and microparticles. In some instances, the conductive filler is selected from graphite, graphene, carbon black, graphene oxide, Super P, acetylene black, carbon nanofibers, carbon nanotubes, and combinations thereof.

[0089] In some instances, the binder is selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), CMS, styrene-butadiene rubber (SBR), polyacrylic acid (PAA), PAA-PEA, and combinations thereof. In some instances, PAA is neutralized by sodium hydroxide (NaOH) or lithium hydroxide (LiOH), sodium polyacrylate (PAANa), PAAH 0.2 N 0.8 or lithium polyacrylate (LiPAA).

[0090] Now referring to Figure 10A , the graph shows the heat flow as a function of temperature for a battery cell of a battery pack having a cathode electrode including a PTC material compared to the same battery cell of a battery pack without the PTC material. In this instance, the cathode active material includes NCMA and the anode active material includes graphite. The cathode active material layer includes a cathode active material (e.g., NCMA), a PTC material, a conductive additive (e.g., Super P), and a binder (e.g., PVDF) having a ratio of 86 / 10 / 2 / 2 wt% (or 96 / 2 / 2 when not using the PTC material). The peak intensity decreases from ~15 W / g to ~5 W / g at ~220 °C.

[0091] Now referring to Figure 10B and 10C, showing the formation cycle check and capacity rate check of battery pack cells with and without PTC material. This check shows that the performance of battery pack cells with and without PTC material is comparable. In Figure 10C , some of the active material is replaced with PTC material, which has higher conductivity and provides improved performance at some charge rates (e.g., 2C) and comparable performance at other charge rates.

[0092] The foregoing description is merely exemplary and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure may be implemented in a variety of forms. Thus, although the disclosure includes specific examples, the true scope of the disclosure should not be so limited because other modifications will become apparent upon study of the drawings, the specification, and the following claims. It should be understood that one or more steps within a method may be implemented in a different order (or concurrently) without altering the principles of the disclosure. Further, although the embodiments are described above as having certain features, any one or more of the features described with respect to any one embodiment of the disclosure may be implemented in and / or combined with the features of any other embodiment, even if not explicitly described in that combination. In other words, the described embodiments are not mutually exclusive, and permutations of one or more of the embodiments are still within the scope of the disclosure.

[0093] Various terms are used to describe the spatial and functional relationships between elements (e.g., between modules, circuit elements, semiconductor layers, etc.), including "connected", "joined", "coupled", "adjacent", "next to", "on top of", "on", "under", and "disposed". Unless explicitly described as "direct", when the relationship between a first element and a second element is described in the foregoing disclosure, the relationship can be a direct relationship in which no other intervening elements exist between the first element and the second element, or an indirect relationship in which one or more intervening elements exist between the first element and the second element (spatially or functionally). The phrase "at least one of A, B, and C" as used herein should be construed to mean a logical (A or B or C) using a non-exclusive logical OR and should not be construed to mean "at least one of A, at least one of B, and at least one of C".

[0094] In the drawings, the direction of the arrow as shown by the arrow generally shows the information flow (such as data or instructions) of interest in the illustration. For example, when element A and element B exchange various information but the information sent from element A to element B is relevant to the illustration, the arrow can point from element A to element B. Such a one-way arrow does not mean that no other information is sent from element B to element A. Further, for the information transmitted from element A to element B, element B can send a request for that information or receive an acknowledgment to element A.

Claims

1. An electrode for a battery cell of a battery pack, comprising: A current collector; And An active material layer disposed on the current collector, the active material layer comprising: Active material; Conductive additive; Positive temperature coefficient (PTC) material; and Binder.

2. The electrode according to claim 1, wherein the active material is 80 wt% to 99 wt%, the PTC material is 0.5 wt% to 20 wt%, the conductive additive is 0.5 wt% to 20 wt%, and the binder is 0.5 wt% to 10 wt%.

3. The electrode according to claim 1, wherein the active material is 80 wt% to 99 wt%, the PTC material is 1 wt% to 5 wt%, the conductive additive is 0.5 wt% to 20 wt%, and the binder is 0.5 wt% to 10 wt%.

4. The electrode according to claim 1, wherein the Curie temperature of the PTC material is between 80 °C and 200 °C.

5. The electrode according to claim 1, wherein the Curie temperature of the PTC material is between 80 °C and 140 °C.

6. The electrode according to claim 1, wherein the PTC material comprises an inorganic material selected from metal oxides, BaTiO3, V2O5, and combinations thereof.

7. The electrode according to claim 1, wherein the PTC material comprises an organic material selected from polymethyl methacrylate (PMMA) or polydimethylsiloxane (PDMS).

8. The electrode according to claim 1, wherein the PTC material is doped with one or more elements selected from 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. An electrode for a battery cell of a battery pack, comprising: A current collector; And An active material layer disposed on the current collector, the active material layer comprising: Active material, which includes an outer coating containing a positive temperature coefficient (PTC) material; Conductive additive; and Binder.

10. The electrode according to claim 9, wherein the Curie temperature of the PTC material is between 80 °C and 200 °C.

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