Dissolution assisted wetting of lithium on copper current collectors

Abstract

The invention relates to dissolution assisted wetting of lithium on copper current collectors. A method for manufacturing an anode electrode for a battery cell includes melting lithium metal in a bath to produce molten lithium metal; adding copper to the molten lithium metal in the bath to form a molten lithium matrix comprising lithium metal and distributed copper particles, wherein the concentration of copper added to the bath is between 5 wt% and 15 wt%; and coating a copper current collector with the molten lithium matrix to form an anode active material layer on the copper current collector.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to battery cells, and more particularly to an anode electrode fabricated by dissolving and wetting lithium onto a copper current collector. BACKGROUND

[0002] This section provides information which can be useful in general understanding. No admission is made that any of the information provided herein is prior art. The description provided in this section is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent the work is described in this section, as well as aspects of the description that can not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as 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 machines and a battery pack system including one or more battery cells, modules, and / or packs. A power control system is used to control the 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 layer of cathode active material (including a cathode active material) disposed on a cathode current collector. The anode electrode includes a layer of anode active material (including an anode active material) disposed on an anode current collector. SUMMARY

[0005] A method for fabricating an anode electrode for a battery cell includes melting lithium metal in a bath to produce a molten lithium metal; adding copper to the molten lithium metal in the bath to form a molten lithium matrix including lithium metal and distributed copper particles, wherein the concentration of copper added to the bath is between 5 wt% and 15 wt%; and coating a copper current collector with the molten lithium matrix to form a layer of anode active material on the copper current collector.

[0006] In other features, the method includes stirring the molten lithium matrix to produce a homogenous mixture. The method includes stirring the molten lithium matrix using an electromagnetic stirrer. The anode electrode has a thickness of less than 70 pm. The anode electrode has a width of greater than 100 pm.

[0007] In other features, the method includes heating the bath to a temperature that is at least 100 °C greater than the melting temperature of lithium. The temperature of the bath is between 290 °C and 310 °C. The copper added to the bath is selected from the group consisting of copper foil, bronze foil, brass foil, and combinations thereof. The copper added to the bath includes copper foil. The copper current collector does not include a lithiumophilic metal / metal oxide coating.

[0008] An anode electrode for a battery cell includes an anode current collector including copper and an anode active material layer coated on an outer surface of the anode current collector. The anode active material layer includes a lithium matrix including lithium metal and distributed copper particles. The copper in the anode active material layer is 5 wt% to 15 wt% of the anode active material layer.

[0009] In other features, the distributed copper particles form copper dendrites in the lithium metal of the anode active material layer. The anode electrode has a thickness of less than 70 μιη, and the anode electrode has a width of greater than 100 μιη.

[0010] In other features, the anode current collector includes a copper foil. The anode current collector does not include a lithiumophilic metal / metal oxide coating.

[0011] A battery cell includes A anode electrodes, C cathode electrodes, and S separators, where A, C, and S are integers greater than 1.

[0012] A method for manufacturing an anode electrode for a battery cell includes heating lithium metal in a bath to produce molten lithium metal at a temperature at least 100 °C above a melting temperature of the lithium metal; and adding copper to the molten lithium in the bath to form a lithium matrix including distributed copper particles. The copper is 5 wt% to 15 wt% of the lithium matrix. The method includes agitating the lithium matrix in the bath using an electromagnetic stirrer; and coating a copper current collector with the lithium matrix in the bath to form an anode active material layer on the copper current collector. The temperature is 290 °C to 310 °C.

[0013] In other features, the copper added to the bath is selected from a copper foil, a bronze foil, and a brass foil. The anode electrode has a thickness of less than 70 μιη, and the anode electrode has a width of greater than 100 μιη.

[0014] The following aspects are disclosed:

[0015] Aspect 1. A method for manufacturing an anode electrode for a battery cell, comprising:

[0016] melting lithium metal in a bath to produce molten lithium metal;

[0017] adding copper to the molten lithium metal in the bath to form a molten lithium matrix including lithium metal and distributed copper particles,

[0018] where a concentration of the copper added to the bath is 5 wt% to 15 wt%; and

[0019] coating a copper current collector with the molten lithium matrix to form an anode active material layer on the copper current collector.

[0020] Scheme 2. The method according to Scheme 1, further comprising stirring the molten lithium matrix to produce a homogenous mixture.

[0021] Scheme 3. The method according to Scheme 2, further comprising stirring the molten lithium matrix using an electromagnetic stirrer.

[0022] Scheme 4. The method according to Scheme 1, wherein the anode electrode has a thickness of less than 70 pm.

[0023] Scheme 5. The method according to Scheme 1, wherein the anode electrode has a width of greater than 100 pm.

[0024] Scheme 6. The method according to Scheme 1, further comprising heating the bath to a temperature that is at least 100 °C greater than the melting temperature of lithium.

[0025] Scheme 7. The method according to Scheme 6, wherein the temperature of the bath is from 290 °C to 310 °C.

[0026] Scheme 8. The method according to Scheme 1, wherein the copper added to the bath is selected from the group consisting of copper foil, bronze foil, brass foil, and combinations thereof.

[0027] Scheme 9. The method according to Scheme 1, wherein the copper added to the bath comprises copper foil.

[0028] Scheme 10. The method according to Scheme 1, wherein the copper current collector does not include a lithiumophilic metal / metal oxide coating.

[0029] Scheme 11. An anode electrode for a battery cell, comprising:

[0030] a copper-containing anode current collector; and

[0031] a layer of anode active material coated on an outer surface of the anode current collector,

[0032] wherein the layer of anode active material comprises a lithium matrix comprising lithium metal and distributed copper particles,

[0033] wherein the copper in the layer of anode active material comprises from 5 wt% to 15 wt% of the layer of anode active material.

[0034] Scheme 12. The anode electrode according to Scheme 11, wherein the distributed copper particles form copper dendrites in the lithium metal of the layer of anode active material.

[0035] Scheme 13. The anode electrode according to Scheme 11, wherein:

[0036] the anode electrode has a thickness of less than 70 pm, and

[0037] The anode electrode has a width greater than 100 pm.

[0038] Scheme 14. The anode electrode of Scheme 11, wherein the anode current collector comprises a copper foil.

[0039] Scheme 15. The anode electrode of Scheme 11, wherein the anode current collector does not comprise a lithiumophilic metal / metal oxide coating.

[0040] Scheme 16. A battery cell for a vehicle, comprising:

[0041] A anode electrode of Scheme 11;

[0042] C cathode electrodes; and

[0043] S separators, wherein A, C, and S are integers greater than 1.

[0044] Scheme 17. A method for manufacturing an anode electrode for a battery cell, comprising:

[0045] heating lithium metal in a bath to produce molten lithium metal at a temperature at least 100 °C greater than the melting temperature of lithium metal;

[0046] adding copper to the molten lithium metal in the bath to form a lithium matrix comprising distributed copper particles,

[0047] wherein the copper comprises 5 to 15 wt% of the lithium matrix; and

[0048] stirring the lithium matrix in the bath using an electromagnetic stirrer; and

[0049] coating a copper current collector with the lithium matrix in the bath to form an anode active material layer on the copper current collector,

[0050] wherein the anode electrode has a thickness less than 70 pm and a width greater than 100 pm.

[0051] Scheme 18. The method of Scheme 17, wherein the temperature is 290 °C to 310 °C.

[0052] Scheme 19. The method of Scheme 17, wherein the copper added to the bath is selected from the group consisting of a copper foil, a bronze foil, and a brass foil.

[0053] Further areas of applicability of the present disclosure will become apparent from the detailed description, the claims and the drawings. The detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF DRAWINGS

[0054] The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein:

[0055] Figure 1 is a side cross-sectional view of an example of a battery cell including C cathode electrodes, A anode electrodes, and S separators, the A anode electrodes including a copper anode current collector and a lithium copper metal coating, in accordance with the present disclosure;

[0056] Figure 2 is a side cross-sectional view of an example of a cathode electrode, in accordance with the present disclosure;

[0057] Figure 3 is a side cross-sectional view of an example of an anode electrode including a copper anode current collector and a lithium copper coating, in accordance with the present disclosure;

[0058] Figure 4 is a side cross-sectional view of an example of lithium metal not wetting onto a copper anode current collector;

[0059] Figure 5 is a graph showing an example of the phase and solubility of a mixture of lithium and copper as a function of temperature and copper concentration;

[0060] Figure 6 is a flow chart of an example of a method of wetting an anode current collector using a bath including a molten lithium matrix having lithium metal and distributed copper particles, in accordance with the present disclosure;

[0061] Figure 7 is a side view showing an example of preparing a bath including a molten lithium matrix having lithium metal and distributed copper particles, in accordance with the present disclosure;

[0062] Figure 8 is a side view showing an example of making an anode electrode by passing a copper foil through a bath including molten lithium copper, in accordance with the present disclosure;

[0063] Figure 9A is a magnified side cross-sectional view of an anode electrode, in accordance with the present disclosure;

[0064] Figure 9B is a magnified plan view of a lithium copper layer, in accordance with the present disclosure;

[0065] Figure 10A is a plan view of a pure lithium layer showing lithium spalling and formation of post-plating dendrites; and

[0066] Figure 10B is a plan view of a lithium copper layer with more uniform lithium spalling and post-plating, in accordance with the present disclosure.

[0067] In the drawings, reference numerals can be repeated among the figures for like and / or similar elements. DETAILED DESCRIPTION

[0068] Although the anode electrode and battery pack according to this disclosure are shown in the context of an electric vehicle, the anode electrode and battery pack can be used in stationary applications and / or other applications.

[0069] Compared to graphite, which has a theoretical specific capacity of only 360 mAh / g, lithium (Li) metal anode electrodes can provide the highest theoretical specific capacity (~3860 mAh / g). Conventional methods for manufacturing lithium foil are typically based on extrusion and rolling. Manufacturing lithium foil by rolling is extremely challenging. For large-format battery packs, lithium foil needs to be large and thin enough (e.g., less than 70 μm thick and greater than 100 mm wide). The poor mechanical properties of lithium (e.g., extreme softness) have hindered the use of rolling in these applications.

[0070] A method for manufacturing ultrathin lithium metal anodes involves coating a current collector foil with molten lithium. However, in practice, manufacturing molten lithium anodes is difficult. Lithium has extremely low wettability on commercial current collector substrates such as copper foil, stainless steel foil, or 3D mesh current collectors. For example, when liquid lithium is coated onto the surface of untreated copper foil, molten lithium spheres form. Lithium does not adhere well to copper, creating bare spots on the copper foil surface. Molten lithium also dissolves some of the copper from the foil, causing the foil to crumble.

[0071] Efforts have been made to improve the wettability of molten lithium on copper current collectors and / or prevent the dissolution of copper foil current collectors. These methods typically require coating the copper current collector with a lithium-philic metal / metal oxide coating (such as Zn, Sn, Mg, their oxides, and combinations thereof). In some instances, electroplating processes are used to add the coating. However, electroplating significantly increases the cost of the manufacturing process. Furthermore, it is difficult to uniformly deposit a lithium-philic coating to uniformly improve wettability and prevent copper dissolution across the entire surface area of ​​the current collector.

[0072] The anode electrode according to this disclosure includes a copper current collector immersed in a bath heated to a predetermined temperature increment at least 100°C higher than the melting temperature of lithium (e.g., 170°C). For example, the temperature of the bath can be maintained at approximately 300°C (e.g., 290°C to 310°C). The bath contains molten lithium and copper. Copper is dissolved in the lithium bath to improve the wettability of molten lithium on the copper current collector.

[0073] Copper has relatively low solubility in lithium baths at 300 °C. For example, the solubility of copper in molten lithium at 300 °C is less than 0.1% by weight. Adding copper to molten lithium exceeds the solubility limit of copper in molten lithium at the bath temperature. In some instances, copper in the bath accounts for 5% to 15% by weight of the molten metal, which is significantly higher than the solubility of copper at this temperature. In some instances, lithium accounts for 85% to 95% by weight.

[0074] Adding copper to the molten lithium bath creates a secondary metallic additive phase (an alloy of copper and lithium), which helps reduce the surface energy of the lithium bath and improves the wettability of the molten lithium. Furthermore, the molten lithium with the secondary copper-lithium additive phase prevents further dissolution of copper from the current collector foil.

[0075] By allowing copper to dissolve into the molten lithium bath, the surface tension of the bath is reduced. As described herein, the meniscus shape of the applied coating changes from a spherical shape to a flat surface in response to the copper added to the molten lithium. When the molten lithium bath contains copper adducts, lithium spontaneously wets the copper current collector. Furthermore, the copper foil current collector does not fracture during coating in the bath.

[0076] Now for reference Figure 1 The battery pack 10 includes C cathode electrodes 20, A anode electrodes 40, and S spacers 32 arranged in a predetermined order within the battery pack stack 12, where C, S, and A are integers greater than zero. The battery pack stack 12 is arranged within a housing 50. In some embodiments, a liquid electrolyte 52 is added to the housing 50.

[0077] C cathode electrodes 20-1, 20-2, ..., 20-C include a cathode active material layer 24 disposed on one or both sides of the cathode current collector 26. A anode electrodes 40-1, 40-2, ..., 40-A include an anode active material layer 42 disposed on one or both sides of the anode current collector 46. The anode active material layer 42 includes a lithium copper layer, which is coated by immersing the anode current collector 46 in a lithium copper bath containing 5% to 15% copper as described herein. The anode current collector 46 includes a copper current collector. S spacers 32-1, 32-2, ..., 32-S are disposed between the C cathode electrodes 20 and the A anode electrodes 40.

[0078] In some instances, A anode electrodes 40 and C cathode electrodes 20 exchange lithium ions during charging / discharging. In some instances, the cathode active material layer 24 includes a coating comprising one or more active materials, one or more conductive additives, and / or one or more binder materials, which are cast or applied to one or both sides of the cathode current collector 26.

[0079] In some instances, the cathode current collector 26 comprises metal foil, metal mesh, perforated metal, three-dimensional (3D) metal foam, and / or expanded metal. In some instances, the cathode current collector is made of one or more materials selected from stainless steel, brass, bronze, zinc, aluminum, and / or alloys thereof. External tabs 28 and 48 extend from the current collectors of the cathode and anode electrodes, respectively, and may be arranged on the same side or different sides of the battery pack stack 12. External tabs 28 and 48 are connected to the terminals of the battery pack cells.

[0080] Now for reference Figure 2 One of the C cathode electrodes 20 is shown in more detail. The cathode active material layer 24 includes cathode active material 62, conductive additive 64, and binder 66.

[0081] Now for reference Figure 3 The anode electrode 40 includes a copper foil current collector 120 and an anode active material layer 124. The anode active material layer 124 is applied by passing the copper foil current collector 120 through a lithium-copper bath heated to a temperature above 270°C (e.g., 300°C). As mentioned above, it is difficult to wet the surface of the copper foil current collector 120 using pure molten lithium. Figure 4 In the process, when the copper foil current collector 120 is coated, the meniscus of the pure lithium metal 132 coated on the copper foil has a spherical shape, rather than the flat surface required to correspond to the anode active material layer.

[0082] According to this disclosure, a copper foil current collector 120 is immersed in a bath comprising a molten lithium matrix containing dissolved copper particles. The copper foil current collector 120 is coated to form an anodic active material layer 124. In some examples, the anodic active material layer 124 comprises 85% to 95% by weight of lithium metal and 5% to 15% by weight of copper.

[0083] exist Figure 5 The diagram illustrates the phases and solubilities of a bath containing both lithium and copper at different temperatures and copper concentrations. According to this disclosure, copper is added to the lithium bath up to the solubility limit of copper. Additional copper is added to form a copper concentration of 5% to 15% by weight in the molten lithium. The copper concentration in the bath is significantly greater than the solubility of copper at the heating temperature of the bath. The added copper improves the wettability of the copper foil current collector. Since the copper in the bath exceeds the solubility of copper, the added copper also reduces the solubility of the copper foil current collector (which would occur if pure molten lithium were used).

[0084] Now for reference Figure 6The method 200 is illustrated using a bath comprising a molten lithium matrix with distributed copper particles to wet an anode current collector. At 220, lithium is melted in a bath at a temperature at least 100 °C higher than the melting temperature of lithium (e.g., 270 °C (= 170 °C + 100 °C)). At 224, copper is added to the bath up to the solubility limit of copper. At 226, additional copper is added to increase the copper concentration to 5% to 15% by weight. The added copper causes secondary phase formation (beyond the solubility limit of copper) and prevents further dissolution of copper from the copper foil current collector. At 230, the copper foil current collector is passed through a lithium-copper bath to coat the copper foil current collector (e.g., forming an anode active material layer for the anode electrode) with lithium copper.

[0085] Now for reference Figure 7 An example of preparing a molten lithium-copper bath is shown. Lithium metal is heated and melted in bath 310. Source 320 supplies copper 322 into the lithium bath to form a molten lithium matrix comprising lithium metal and copper particles 312 with a distribution of secondary phase formation, such as... Figure 6 The copper is described above. In some instances, the copper includes copper foil, brass foil (Cu-Zn), and / or bronze foil (Cu-Sn). The copper introduced into the molten lithium bath dissolves into the molten lithium. The distributed copper particles reduce the surface tension of the molten Li. In some instances, an electromagnetic stirrer 324 is used to stir the molten lithium to provide a homogeneous mixture. In some instances, the foil (including copper) added to the bath includes waste generated during battery pack manufacturing (e.g., waste copper foil generated during the formation of the outer tab 48 of the anode current collector 46).

[0086] Now for reference Figure 8 The fabrication of the anode electrode is illustrated. A copper foil current collector 354 is supplied by roller 350. The copper foil current collector 354 passes through rollers 358 and 360 in a bath 310 comprising a molten lithium matrix having lithium metal and distributed copper particles (at 312). The copper foil current collector 354 is coated in the bath, and then the anode electrode 370 is collected on roller 362.

[0087] Now for reference Figure 9A and 9B Copper from a lithium-copper bath forms an anode electrode, which includes an active material layer with a two-phase microstructure comprising a lithium matrix having lithium metal and homogeneously distributed copper particles. Figure 9A In this process, a lithium copper layer is formed on a copper current collector (CCC). The copper current collector passes through the lithium copper bath. In some instances, some copper foil added to the molten lithium metal forms dendritic copper portions within the lithium copper layer, such as... Figure 9B As shown. In other words, copper dendrites form a 3-D current collector within lithium metal.

[0088] Now for reference Figure 10A and10B The microstructure of the lithium-copper layer was compared with that of a lithium foil / copper foil laminate after 50 peeling and plating cycles. Figure 10A The image shows a lithium layer formed by rolling a lithium foil layer onto a copper foil current collector. Lithium dendrites have formed after cycling.

[0089] exist Figure 10B In this process, the lithium copper layer is formed by coating a copper foil current collector using a lithium copper bath as described herein. As can be understood, in-situ Cu particles and / or dendrites in the lithium copper layer appear to benefit more uniform lithium stripping and plating. In other words, in-situ Cu particles and / or dendrites can reduce the formation of lithium dendrites during cycling.

[0090] The foregoing description is exemplary in nature and is in no way intended to limit this disclosure, its application, or its use. The broad teachings of this disclosure can be implemented in various forms. Therefore, although this disclosure includes specific examples, its true scope should not be limited thereto, as other modifications will become apparent upon examination of the drawings, specification, and the following claims. It should be understood that one or more steps within the method may be performed in a different order (or simultaneously) without altering the principles of this disclosure. Furthermore, although the embodiments are described above as having certain features, any one or more of those features described with respect to any embodiment of this disclosure may be implemented in any other embodiment and / or combined with features of any other embodiment, even if such combination is not explicitly described. In other words, the embodiments are not mutually exclusive, and the mutual permutations and combinations of one or more embodiments remain within the scope of this disclosure.

[0091] Various terms are used to describe spatial and functional relationships between elements (e.g., modules, circuit elements, semiconductor layers, etc.), including “connection,” “joint,” “coupled,” “adjacent,” “next to,” “on top of,” “above,” “below,” and “disposed.” Unless explicitly described as “direct,” when describing the relationship between the first and second elements in the foregoing disclosure, the relationship can be a direct relationship in which no other intermediary element exists between the first and second elements, or an indirect relationship in which one or more intermediary elements exist between the first and second elements (spatially or functionally). The phrase “at least one of A, B, and C” as used herein should be interpreted as referring to the logic of using non-exclusive OR (A OR B OR C) and should not be interpreted as referring to “at least one of A, at least one of B, and at least one of C.”

Claims

1. A method for manufacturing an anode electrode for a battery pack, comprising: Lithium metal is melted in a bath to produce molten lithium metal; Copper is added to the molten lithium metal in the bath to form a molten lithium matrix comprising lithium metal and distributed copper particles. The concentration of copper added to the bath is 5% to 15% by weight; and The copper current collector is coated with the molten lithium matrix to form an anolyte active material layer on the copper current collector.

2. The method of claim 1, further comprising stirring the molten lithium matrix to produce a homogeneous mixture.

3. The method of claim 2, further comprising stirring the molten lithium matrix using an electromagnetic stirrer.

4. The method according to claim 1, wherein the anode electrode has a thickness of less than 70 μm.

5. The method according to claim 1, wherein the anode electrode has a width greater than 100 μm.

6. The method of claim 1, further comprising heating the bath to a temperature at least 100°C higher than the melting temperature of lithium.

7. The method according to claim 6, wherein the temperature of the bath is 290°C to 310°C.

8. The method of claim 1, wherein the copper added to the bath is selected from copper foil, bronze foil, brass foil, and combinations thereof.

9. The method of claim 1, wherein the copper added to the bath comprises copper foil.

10. The method of claim 1, wherein the copper current collector does not include a lithium-philic metal / metal oxide coating.

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