WIRE BRAIDED POWER COLLECTORS FOR BATTERY CELL ELECTRODES WITH INCREASED CONNECTION CONTACT AND REDUCED RESISTANCE

Abstract

A method for manufacturing a current collector for a battery cell electrode comprises providing a wire mesh current collector consisting of multiple first wires and multiple second wires that overlap to form multiple braid connections. The diameter of the multiple first wires and the multiple second wires is in the range of 4 µm to 100 µm. The method includes coating the wire mesh current collector with a metal coating by immersing the wire mesh current collector in a bath containing a metal salt.

Description

INTRODUCTION

[0001] The information provided in this section is intended to provide a general context for the disclosure. Work by the presently named inventors, to the extent described in this section, as well as aspects of the description that may not otherwise be prior art at the time of filing, are not expressly or impliedly admitted as prior art to the present disclosure.

[0002] The present disclosure relates to wire mesh current collectors for battery cell electrodes, and more particularly to a method for coating wire mesh current collectors of battery cells to improve interconnect contact and reduce resistance.

[0003] Electric vehicles (EVs), such as battery electric vehicles (BEVs), hybrid vehicles, and / or fuel cell vehicles, comprise one or more electric machines and a battery system with one or more battery cells, modules, and / or packs. A battery control module is used to control the charging and / or discharging of the battery system during charging and / or driving. EV manufacturers are striving for higher power density to increase the range of EVs. SUMMARY

[0004] A method of manufacturing a current collector for an electrode of a battery cell comprises providing a wire mesh current collector comprising a plurality of first wires and a plurality of second wires overlapped to form a plurality of mesh connections. The diameter of the plurality of first wires and the plurality of second wires ranges from 4 µm to 100 µm. The method comprises coating the wire mesh current collector with a metal coating by immersing the wire mesh current collector in a bath containing a metal salt.

[0005] In other cases, the plurality of first wires and the plurality of second wires of the wire mesh current collector are made of one or more metals selected from a group consisting of copper, stainless steel, brass, bronze, zinc, aluminum, and their alloys. The metal coating comprises a metal selected from the group consisting of indium (In), tin (Sn), bismuth (Bi), zinc (Zn), nickel (Ni), and their alloys.

[0006] In other cases, the method includes annealing the wire mesh current collector after coating the wire mesh current collector to improve physical and electrical contact at the plurality of mesh connections. The annealing is performed at a temperature that is higher than the melting temperature of a metal of the metal coating and lower than the melting temperature of a metal of the plurality of first wires and the plurality of second wires of the wire mesh current collector.

[0007] In other cases, the method comprises disposing a layer of anode active material adjacent to the wire mesh current collector. The method comprises disposing a layer of cathode active material adjacent to the wire mesh current collector. The method comprises coating the wire mesh current collector with a slurry containing anode active material. The method comprises coating the wire mesh current collector with a slurry containing cathode active material.

[0008] In other cases, the wire mesh current collector is immersed in the bath in individual sections. The wire mesh current collector is continuously immersed in the bath from a roll.

[0009] A method of manufacturing a current collector for an electrode of a battery cell includes providing a wire mesh current collector comprising a plurality of first wires and a plurality of second wires that overlap to form mesh connections. The diameter of the plurality of first wires and the plurality of second wires ranges from 4 µm to 100 µm. The plurality of first wires and the plurality of second wires of the wire mesh current collector are made of a metal selected from a group consisting of copper, stainless steel, brass, bronze, zinc, aluminum, and their alloys. The method includes immersing the wire mesh current collector in a bath containing a metal salt to coat the wire mesh current collector. The metal salt comprises a metal selected from the group consisting of indium (In), tin (Sn), bismuth (Bi), zinc (Zn), and their alloys.The process involves annealing the wire mesh current collector after the wire mesh current collector has been passed through the bath.

[0010] In other cases, the annealing is performed at a temperature higher than the melting temperature of a metal in the metal salt and lower than the melting temperature of the metal used in the wire mesh current collector. The method includes disposing a layer of anode active material adjacent to the wire mesh current collector. The method includes disposing a layer of cathode active material adjacent to the wire mesh current collector. The method includes coating the wire mesh current collector with a slurry containing anode active material. The method includes coating the wire mesh current collector with a slurry containing cathode active material.

[0011] In other cases, the wire mesh current collector is immersed in the bath in individual sections. The wire mesh current collector is continuously immersed in the bath from a roll.

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

[0013] The present disclosure will become more fully understood from the detailed description and the accompanying drawings, in which: Fig. 1 is a side cross-sectional view of an example battery cell having electrodes with coated wire mesh current collectors according to the present disclosure; Fig. 2A and Fig. 2B are plan views illustrating the tensile strength of an uncoated wire mesh current collector in two directions; Fig. 3A and Fig. 3B illustrate examples of methods for coating and optionally annealing a wire mesh current collector according to the present disclosure; Fig. 4A is a side view illustrating an example of a wire mesh current collector after coating according to the present disclosure; Fig. 4B is an enlarged side view illustrating an example of a wire mesh current collector after coating in accordance with the present disclosure; Fig. 5A is a side view illustrating an example of a wire mesh current collector after coating and annealing according to the present disclosure; and Fig. Figure 5B is an enlarged side view illustrating an example of a wire mesh current collector after coating and annealing.

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

[0015] Although wire mesh current collectors for battery cells according to the present disclosure are described herein in the context of electric vehicles, the battery cells may also be used in stationary applications and / or in other types of applications.

[0016] Battery cells include anode and cathode electrodes and separators arranged in a stack in a predetermined order. The anode electrodes include an active anode layer disposed on one or both sides of an anode current collector. The cathode electrodes include an active cathode layer disposed on one or both sides of a cathode current collector. In some examples, the layer of anode active material or the layer of cathode active material includes metal layers disposed adjacent to the current collectors. In other examples, the layer of anode active material or the layer of cathode active material includes coatings applied to the anode or cathode current collectors. The coatings may include one or more anode or cathode active materials, one or more binders, and one or more conductive fillers.

[0017] The anode and cathode current collectors may comprise foil, wire mesh, or expanded metal. Wire mesh current collectors may, for example, comprise wires made of copper (Cu), stainless steel (SS), brass, bronze, zinc (Zn), aluminum (Al), and their alloys (e.g., Cu-100 or SS-100). The wire mesh current collectors may be made of wires with a thickness of 4 µm to 100 µm (e.g., 30 µm). In some examples, the wire mesh current collectors have approximately 100 to 300 openings per square inch (e.g., 100).

[0018] The wires of the wire mesh current collector cross at the braid joints. Although the wires are in contact with each other at the braid joints, they are not rigidly connected. This results in the wire mesh current collector having low strength, stiffness, and / or deformation resistance, which makes it difficult to handle during electrode production. Electrodes can be manufactured, for example, using a roll-to-roll process, which requires handling of the wire mesh current collector.

[0019] The present disclosure relates to methods for increasing the strength and stiffness of wire meshes used as three-dimensional current collectors (3DCCs) in battery cell electrodes. Gaps and / or the lack of adequate physical and / or electrical contact between wires crossing at the mesh joints of the wire mesh current collector increase the internal resistance of the current collector. The increased resistance increases heating and / or decreases the performance of the anode and / or cathode electrodes using the wire mesh current collectors.

[0020] The wire mesh current collectors according to the present disclosure are coated with a metal coating to increase stiffness and reduce resistance. In some examples, the metal coating is applied by electrodeposition. In some examples, the mesh joints of the wire mesh current collectors are further strengthened by annealing the coated wire mesh after the metal coating is applied. Annealing remelts the coating. The molten coating is drawn further into the mesh joints of the wire mesh current collectors by capillary force. The molten coating cools, solidifies, and more rigidly bonds the intersecting wires at the mesh joints.

[0021] In some examples, the metal coating includes a metal material with a melting point below the melting temperature of the metal of the wires of the wire mesh current collector, so that annealing can optionally be performed after coating. In some examples, the metal coating comprises one or more metals selected from a group consisting of tin (Sn), indium (In), bismuth (Bi), zinc (Zn), nickel (Ni), and their alloys. Annealing may be omitted if the metal in the metal coating has a higher melting temperature than the metal of the wires of the wire mesh current collector. For example, if the wires of the wire mesh current collectors are made of Cu and the metal coating comprises Ni, annealing is not performed because Ni has a higher melting temperature than copper (Cu).

[0022] With reference now to Fig. 1, a battery cell 10 contains cathode electrodes 20-1, 20-2, ..., and 20-C, where C is an integer greater than one. The cathode electrodes 20 comprise a layer of cathode active material 24 arranged on one or both sides of the cathode current collectors 26. The battery cell 10 contains anode electrodes 40-1, 40-2, ..., and 40-A, where A is an integer greater than one. The anode electrodes 40 comprise a layer of anode active material 42 arranged on one or both sides of the anode current collectors 46. The cathode electrodes 20, the anode electrodes 40, and the separators 32 are arranged in a predetermined order in a housing 50. For example, separators 32 are arranged between the cathode electrodes 20 and the anode electrodes 40. The anode current collector 46 and / or the cathode current collector 26 comprise a coated, or coated and annealed, wire mesh, as described below.

[0023] With reference now to Fig. 2A through 2B, the anode and / or cathode current collectors comprise a wire mesh 70 having a plurality of first wires 74 spaced apart by a predetermined gap and extending parallel to each other in a first direction. The wire mesh 70 includes a plurality of second wires 76 spaced apart by a gap and extending parallel to each other in a second direction different from the first direction. The plurality of first wires 74 and the plurality of second wires 76 are woven over and under each other. In some examples, the first and second directions are transverse to each other, but other angles may be used.

[0024] Without coating, or coating and annealing, the wire mesh 70 exhibits anisotropy in its mechanical properties. When drawn in the direction of Fig. 2A, the stiffness of an exemplary copper wire mesh is about 22 N / mm at a peak load of about 8 N. When pulling in the direction of Fig. 2B, the stiffness is extremely low, ∼ 0.06 N / mm at a peak load of approximately 1.5 to 2 N. In addition to the low stiffness, the electrical contact between the wires of the wire mesh at the mesh joints varies from one location to another. This, in turn, leads to fluctuations in the resistance of the wire mesh current collector.

[0025] The coating, or coating and annealing, of the wire mesh current collector described here increases the strength and rigidity of the wire mesh current collector. The wire mesh current collectors therefore exhibit better manufacturing performance because they are easier to use due to their increased strength. The coated, or coated and annealed, wire mesh current collector also ensures better contact between the plurality of first wires and the plurality of second wires at the braid connections, which reduces resistance and improves the speed performance of the lithium metal anode (LMA). Furthermore, some of the coatings (e.g., In, Sn, Bi, and Zn) are lithiophilic, which improves lithium adhesion to the current collector surfaces.

[0026] With reference now to Fig. 3A and Fig. 3B, methods 100 and 100' for coating a wire mesh current collector 110 are shown. In Fig. 3A, the coating and / or annealing process is a continuous roll-to-roll process. The wire mesh current collector 110 is immersed in a bath 126, and the metal coating is deposited on the wire mesh current collector 110. In some examples, the bath contains a metal salt. In some examples, the wire mesh current collector 110 is chemically or electrochemically coated. In some examples, a negative current is applied to the wire mesh current collector 110 during the chemical coating.

[0027] The wire mesh current collector 110 passes over a roller 114 into the bath 126 and under a roller 132 located within the bath 126. In some examples, the roller 114 is connected to a power supply that provides current, and the roller 132 and / or the bath 126 are grounded. After passing through the bath 126, the coated wire mesh current collector 134 passes over a roller 136 and under a roller 138 before passing through a heater 144 configured to anneal the wire mesh current collector 110 at a temperature above a melting temperature of the metal used for coating. Although a particular arrangement of rollers is shown, the rollers may be arranged in other configurations.

[0028] In Fig. 3B, individual sections of the wire mesh current collector 110 are immersed in the bath 126 for a predetermined period of time to chemically coat, deposit, or electroplate the metal coating on the wire mesh current collector 110. The individual sections of the wire mesh current collector 110 can optionally be annealed by a heater after coating.

[0029] In some examples, the coated wire mesh current collector 134 is heated by heaters 144 to a predetermined temperature higher than the melting temperature of the metal coating to remelt and flow the metal coating. The molten coating is drawn between the wires of the wire mesh due to capillary force. The wire mesh is allowed to cool, and the metal coating resolidifies. The metal coating solidifies at the metal joints to rigidly connect the plurality of first wires and the plurality of second wires at the mesh joints. The rigid connection increases the physical strength of the wire mesh and reduces the internal resistance of the wire mesh.

[0030] In some examples, the coating has a thickness in the range of 1 nm to 1 µm. In some examples, the heater 144 heats the coated wire mesh current collector for a predetermined time in the range of 10 seconds to 30 minutes. In some examples, the heater heats the coated wire mesh current collector for a predetermined time in the range of 1 minute to 10 minutes.

[0031] In some examples, the metal in the coating has a melting point below the melting temperature of the material used for the wire mesh current collector 110. In other examples, a coating material (e.g., Ni) may be used that has a higher melting temperature than the metal used for the wires of the wire mesh current collector (e.g., Cu), and annealing is omitted.

[0032] In some examples, the metal is selected from a group consisting of tin (Sn), indium (In), bismuth (Bi), nickel (Ni), zinc (Zn), and their alloys. In some examples, the coated wire mesh current collector 134 may be cooled to allow the coating to solidify prior to annealing. In other examples, the coated wire mesh current collector 134 is not fully cooled after the bath 126 and prior to annealing by the heater 144.

[0033] With reference now to Fig. 4A and Fig. 4B shows the wire mesh current collector 134 after the metal coating has been applied. The wire mesh current collector 134 includes a plurality of first wires 210 extending in a first direction and a plurality of second wires 212 extending in a second direction different from (e.g., transverse to) the first direction. The plurality of first wires 210 and the plurality of second wires 212 of the wire mesh current collector 134 include a coating layer 218.

[0034] With reference now to Fig. 5A and Fig.5B illustrates the wire mesh current collector 148 after coating and annealing. The wire mesh current collector 134 includes the plurality of first wires 210 extending in the first direction and the plurality of second wires 212 extending in the second direction that is different from (e.g., transverse to) the first direction. The plurality of first wires 210 and the plurality of second wires 212 of the wire mesh current collector 134 include the coating layer 218. After annealing, at least a portion of the coating layer remelts and is drawn between the plurality of first wires 210 and the plurality of second wires 212 by capillary force, as shown at 220.

[0035] The foregoing description is merely illustrative and is not intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure may be embodied in a variety of forms. Therefore, while this disclosure contains specific examples, the true scope of the disclosure should not be so limited, since other modifications will become apparent upon examination of the drawings, the specification, and the following claims. It is understood that one or more steps within a method may be performed in different orders (or simultaneously) without altering the principles of the present disclosure.Although each of the embodiments described above includes certain features, one or more of these features described with respect to any embodiment of the disclosure may be implemented in and / or combined with features of any other embodiments, even if this combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and permutations of one or more embodiments remain within the scope of this disclosure.

[0036] Spatial and functional relationships between elements (e.g., between modules, circuit elements, semiconductor layers, etc.) are described using various terms, including "connected," "engaging," "coupled," "adjacent," "beside," "on top of," "over," "below," and "disposed." If a relationship between first and second elements is not explicitly described as "direct" in the above disclosure, that relationship may be a direct relationship, with no other intervening elements present between the first and second elements; or it may be an indirect relationship, with one or more intervening elements (either spatial or functional) present between the first and second elements.As used herein, the phrase “A, B, and / or C” should be construed as logical (A ORed with B, ORed with C) using a non-exclusive logical “OR” operation, rather than as “at least one of A, at least one of B, and at least one of C.”

[0037] In the figures, the direction of an arrow, as indicated by the arrowhead, generally illustrates the flow of information (e.g., data or instructions) of interest to the illustration. For example, if element A and element B exchange a variety of information, but the information transmitted from element A to element B is relevant to the illustration, the arrow may point from element A to element B. This unidirectional arrow does not imply that no other information is transmitted from element B to element A. Further, for information sent from element A to element B, element B may send requests for or acknowledgments of receipt of the information to element A.

Claims

[1] A method for manufacturing a current collector for an electrode of a battery cell, comprising: Providing a wire braid current collector comprising a plurality of first wires and a plurality of second wires overlapping to form a plurality of braid connections, wherein the diameter of the plurality of first wires and the plurality of second wires is in a range of 4 µm to 100 µm; and Coating the wire mesh current collector with a metal coating by immersing the wire mesh current collector in a bath containing a metal salt. [2] The method of claim 1, wherein the plurality of first wires and the plurality of second wires of the wire mesh current collector are made of one or more metals selected from a group consisting of copper, stainless steel, brass, bronze, zinc, aluminum, and their alloys. [3] The method of claim 1, wherein the metal coating comprises a metal selected from the group consisting of indium (In), tin (Sn), bismuth (Bi), zinc (Zn), nickel (Ni) and their alloys. [4] The method of claim 1, further comprising annealing the wire mesh current collector after coating the wire mesh current collector to improve physical and electrical contact at the plurality of mesh connections. [5] The method of claim 4, wherein the annealing is performed at a temperature higher than the melting temperature of a metal of the metal coating and lower than the melting temperature of a metal of the plurality of first wires and the plurality of second wires of the wire mesh current collector. [6] The method of claim 1, further comprising disposing a layer of anode active material adjacent to the wire mesh current collector. [7] The method of claim 1, further comprising disposing a layer of cathode active material adjacent to the wire mesh current collector. [8] The method of claim 1, further comprising coating the wire mesh current collector with a slurry containing anode active material. [9] The method of claim 1, further comprising coating the wire mesh current collector with a slurry containing cathode active material. [10] The method of claim 1, wherein the wire mesh current collector is immersed in the bath in individual sections.

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