WO2020092525A1

WO2020092525A1 - Covetic alloy current collector for a lead-acid electrochemical cell and method of manufacturing same

Info

Publication number: WO2020092525A1
Application number: PCT/US2019/058806
Authority: WO
Inventors: Jaime Navarrete
Original assignee: Crown Battery Manufacturing Company
Priority date: 2018-10-31
Filing date: 2019-10-30
Publication date: 2020-05-07

Abstract

An electrochemical cell includes a housing defining an interior that contains an electrolyte. First and second current collectors are at least partially immersed in the electrolyte. First and second electrical terminals are respectively connected to the first and second current collectors and extend outwardly from the housing. One or both of the first and second current collectors is composed of a covetic alloy, such as a 98% lead - 2% tin alloy material combined with the covetic material. The covetic material generally represents from about 0.01% to about 10% by weight of the overall alloy, preferably represents from about 1% to about 5% by weight of the overall alloy, and more preferably represents about 3% by weight of the overall alloy.

Description

TITLE

COVETIC ALLOY CURRENT COLLECTOR FOR A LEAD- ACID ELECTROCHEMICAL CELL AND METHOD OF MANUFACTURING SAME

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of United States Provisional Application No. 62/753,103, filed October 31, 2018 the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] This invention relates in general to current collectors for use in electrochemical cells and batteries. In particular, this invention relates to a covetic alloy current collector for use in a lead-acid electrochemical cell or battery, and further to a method of manufacturing same.

[0003] An electrochemical cell is a device that is capable of either generating electrical energy from chemical reactions or using electrical energy to cause chemical reactions. In such electrochemical cells, energy from reduction-oxidation chemical reactions are converted to electrical energy. A typical battery includes one or more of such electrochemical cells that are electrically connected to one another and are supported within a housing having external electrical terminals that facilitate the connection of the battery to an electrically-operated device, such as a flashlight, cell phone, or electric car.

[0004] A conventional electrochemical cell includes a housing defining an interior that contains an electrolyte. First and second current collectors are supported within the interior of the housing so as to be at least partially immersed in the electrolyte. The first and second current collectors have respective electrical terminals provided thereon that extend outwardly from the housing. The current collectors provide physical support for the electrical terminals respectively connected thereto. If desired, either or both of the current collectors may be coated with an active material that facilitates the transfer of electrical current between the electrolyte and the active material and also between the active material and the current collectors.

[0005] In a conventional lead-acid type of electrochemical cell, the current collectors are frequently formed from an alloy consisting of primarily lead and one or more minor elements, such as (but not limited to) calcium, tin, antimony, silver, selenium, bismuth, aluminum, etc. One example of a lead alloy that has been commonly used to form current collectors in lead-acid storage batteries is a 98% lead - 2% tin alloy. This alloying is done because pure (or at least essentially pure) lead is relatively soft (which can result in manufacturing difficulties) and has a higher cost. The use of a lead alloy material provides the current collectors with increased rigidity and reduces cost.

Unfortunately, however, current collectors formed from such lead alloys are prone to increased oxidation after repeated cycling or other use of the electrochemical cell. As the current collector oxidizes, its volume increases as the lead therein is converted to lead dioxide. Such changes in volume can cause undesirable brittleness and other loss of mechanical integrity and strength.

[0006] Notwithstanding this, known current collectors for lead-acid electrochemical cells and batteries have functioned satisfactorily in the past. However, it would be desirable to provide an improved structure for such current collectors, as well as an improved method of manufacturing same, that reduces the rate of corrosion and thus minimizes or avoids the resultant undesirable brittleness and other loss of mechanical integrity and strength.

SUMMARY OF THE INVENTION

[0007] This invention relates to relates to a covetic alloy current collector for use in a lead-acid electrochemical cell or battery, and further to a method of manufacturing same. The electrochemical cell includes a housing defining an interior that contains an electrolyte. First and second current collectors are at least partially immersed in the electrolyte. First and second electrical terminals are respectively provided on or connected to the first and second current collectors and extend outwardly from the housing. One or both of the first and second current collectors is composed of a covetic alloy preferably containing lead, such as a 98% lead - 2% tin alloy material combined with the covetic material for example. The covetic material may generally represent from about 0.01% to about 10% by weight of the overall alloy, preferably represents from about 1% to about 5% by weight of the overall alloy, and more preferably represents about 3% by weight of the overall alloy.

[0008] Various aspects of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Fig. 1 is a schematic sectional elevational view of a portion of a lead-acid electrochemical cell including first and second current collectors in accordance with this invention.

[0010] Fig. 2 is a perspective view of one of the current collectors of the

electrochemical cell illustrated in Fig. 1.

[0011 ] Fig. 3 is a flowchart illustrating a method of manufacturing one of the current collectors illustrated in Figs. 1 and 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0012] Referring now to the drawings, there is schematically illustrated in Fig. 1 a portion of a lead- acid electrochemical cell, indicated generally at 10, in accordance with this invention. The illustrated electrochemical cell 10 is, in large measure, conventional in the art and is intended merely to illustrate one environment in which this invention may be practiced. Thus, the scope of this invention is not intended to be limited for use with the specific structure for the electrochemical cell 10 illustrated in Fig. 1. On the contrary, as will become apparent below, this invention may be used in any desired environment.

[0013] The illustrated portion of the electrochemical cell 10 includes a housing 11 defining an interior that contains an electrolyte 12. The housing 11 and the electrolyte 12 may be formed from any desired materials that are well known in the art. First and second current collectors 13 and 14 are supported within the interior of the housing 11 and are at least partially immersed in the electrolyte 12. The first and second current collectors 13 and 14 have respective electrical terminals l3a and l4a provided thereon or connected thereto that extend outwardly from the housing 11. As is well known, the current collectors 13 and 14 respectively provide physical support for the electrical terminals 13a and 14a. If desired, either or both of the current collectors 13 and 14 may be coated with a conventional active material (not shown) that, as is well known in the art, facilitates the transfer of electrical ions between the electrolyte 12 and the active material, and also between the active material and the associated current collectors 13 and 14.

[0014] The physical structure of the first current collector 13 is best illustrated in Fig. 2. As shown therein, the illustrated first current collector 13 is generally flat and rectangular in shape. However, the first current collector 13 may be formed having any desired shape. The illustrated electrical terminal 13a is formed integrally with the first current collector 13, although such is not required. Optionally, the illustrated first current collector 13 has a plurality of openings 13b extending therethrough. The second current collector 14 may be formed having the same shape as the first current collector 13 although, again, such is not required. The structure of the electrochemical cell 10 thus far described is conventional in the art.

[0015] In accordance with this invention, either (or both) of the first and second current collectors 13 and 14 is composed of a covetic material or manufactured by a covetic process. Covetic materials are generally characterized by the creation, generation, or otherwise inclusion of carbon or nanocarbon particles (e.g., graphene, fullerenes, and nanotubes) into matrices of another metallic material. In other words, covetic materials are metals that have been created with or otherwise modified to include carbon or nanocarbon particles. The creation, generation, or other inclusion of the carbon nanomaterials particles into the base metals has been found to result in very desirable changes in the mechanical and electrochemical properties of current collectors 13 and 14 that are used in electrochemical cells 10 and batteries.

[0016] This invention contemplates that either (or both) of the first and second current collectors 13 and 14 be composed of a covetic material or be formed by a covetic process. Preferably, the base metal of the covetic material is or includes lead. As mentioned above, one example of a conventional alloy that has been commonly used to form either (or both) of the current collectors in known lead-acid electrochemical cells and batteries is a 98% lead - 2% tin alloy. Thus, the first and second current collectors 13 and 14 of this invention may, for example, be formed from an alloy of lead, tin, and carbon or nanocarbon particles. More specifically, this invention contemplates that the conventional base metal material of a 98% lead - 2% tin alloy be modified to include carbon or nanocarbon particles such that the carbon or nanocarbon particles material represents from about 0.01% to about 10% by weight of the overall alloy. Preferably, the carbon covetic material represents from about 1% to about 5% by weight of the overall alloy. Most preferably, the carbon covetic material represents about 3% by weight of the overall alloy.

[0017] It has been found that current collectors 13 and 14 formed from this lead- tin- carbon covetic alloy (or similar covetic alloys) exhibit significantly improved mechanical properties. As a result, current collectors 13 and 14 formed from such a lead-tin-carbon covetic alloy can withstand extended bending without breaking or cracking.

Additionally, current collectors 13 and 14 formed from such a lead- tin-carbon covetic alloy have been found to exhibit a lesser amount of oxidation after cycling or other use of the electrochemical cell 10 than do traditional current collectors formed from conventional lead- tin alloys.

[0018] The covetic process results in an alloy wherein each of the current collectors 13 and 14 has increased flexibility and can withstand a higher degree and frequency of bending without cracking or breaking. Such current collectors 13 and 14 are slower to oxidize after cycling or other use of the electrochemical cell 10. As a result, the lead- covetic current collectors 13 and 14 can increase the cycle life of the electrochemical cell 10 by reducing failures due to grid corrosion and grid growth.

[0019] Fig. 3 is a flowchart illustrating a method, indicated generally at 20, of manufacturing the current collector 13 illustrated in Figs. 1 and 2. In a first step 21 of this method 20, the current collector 13 is formed from a covetic alloy, such as the lead- tin-carbon covetic alloy described above. One example of a process for making this lead- tin-carbon covetic alloy is disclosed in U.S. Patent Application Publication No.

2017/0298476, the disclosure of which is incorporated herein by reference. The current collectors 13 and 14 may be formed using any desired process including, but not limited to, gravity book mold casting, continuous casting, expanded metal, lead foil processes, and other techniques. In a second (optional) step 22 of this method 20, the current collector 13 is coated with a conventional active material, which is cured thereon. Lastly, in a third step 23 of this method 20, the current collector 13 is assembled (together with electrolyte 12 and other current collector 14) into the housing 11 to form the

electrochemical cell 10.

[0020] The principle and mode of operation of this invention have been explained and illustrated in its preferred embodiment. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.

Claims

What is claimed is:

1. An electrochemical cell comprising:

a housing defining an interior that contains an electrolyte;

first and second current collectors at least partially immersed in the electrolyte; and

first and second electrical terminals respectively connected to the first and second current collectors and extending outwardly from the housing;

wherein one or both of the first and second current collectors is formed from a covetic material.

2. The electrochemical cell defined in Claim 1 wherein the covetic material includes a base metal material and carbon or nanocarbon particles.

3. The electrochemical cell defined in Claim 2 wherein the base metal material is or includes lead.

4. The electrochemical cell defined in Claim 2 wherein the base metal material is a 98% lead - 2% tin alloy material.

5. The electrochemical cell defined in Claim 2 wherein the carbon or nanocarbon particles represent from about 0.01% to about 10% by weight of the covetic material.

6. The electrochemical cell defined in Claim 2 wherein the carbon or nanocarbon particles represent from about 1% to about 5% by weight of the covetic material.

7. The electrochemical cell defined in Claim 2 wherein the carbon or nanocarbon particles represent about 3% by weight of the covetic material.

8. The electrochemical cell defined in Claim 2 wherein the covetic material includes a base metal material and carbon particles.

9. The electrochemical cell defined in Claim 2 wherein the covetic material includes a base metal material and nanocarbon particles.