Thermo-mechanical treated lead and lead alloys especially for current collectors and connectors in lead-acid batteries

a lead-acid battery and alloy technology, applied in the field of thermally mechanical treatment of lead-acid batteries, can solve the problems of affecting the life of industrial batteries, limiting the life of automotive batteries, and premature failure of lead-acid batteries, so as to improve the cycle life, improve the performance of lead-acid batteries, and improve the cycle life

Inactive Publication Date: 2004-06-17
AUST KARL T +5
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

0063] FIG. 2 summarizes the estimated improvements in lead-acid battery performance from increases in special grain boundary content as calculated from eqn (5) for material having a conventional grain size of 50 .mu.m. As shown in this figure, significant improvements in cycle life are expected for both intergranular-cracking and corrosion dominated degradation processes, by increasing the population of special grain boundaries, f.sub.sp. At conventional SLI positive current collector dimensions of 1 mm, increasing the special grain boundary population from that typically observed (i.e., 15%) to 50% is expected to result in approximately a 4-fold improvement in cycle life. Moreover, as shown in FIG. 2, this improvement in performance would allow the use of grids having a minimum dimension of as low as 0.2 mm, while still retaining the current performance of SLI batteries. Such a reduction in positive grid thickness would be expected to significantly reduce the size and weight of lead-acid batteries (1 mm positive grid accounts for 25% of total battery weight), or result in commensurate increases in energy density.
0064] Through increasing the special grain boundary fraction in the metal, grain boundary engineering increases the resistance of the metal to crack propagation and strain deformation (creep) by altering the crystallographic structure of the grain boundaries. This is in contrast to previous efforts at providing improved components for lead-acid batteries, such as precipitation or age hardening, which were directed at changing the composition, size and distribution of the microconstituents within the grains. Throu...

Problems solved by technology

Intergranular degradation (i.e., creep deformation, cracking and corrosion) of lead-based positive current collector grids, tubular spines, foils and connectors (straps, lugs, posts) are the principal cause of premature failure of lead-acid batteries.
Intergranular corrosion limits the life of automotive batteries and affects the life of industrial batteries.
Creep deformation, which arises primarily from grain boundary sliding processes, results in dimensional expansion of the positive current collector.
The growth of the positive current collector also contributes to intergranular "cracking".
Growth of the positive current collector in lead-acid batteries is the predominant failure mode of automotive batter...

Method used

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  • Thermo-mechanical treated lead and lead alloys especially for current collectors and connectors in lead-acid batteries
  • Thermo-mechanical treated lead and lead alloys especially for current collectors and connectors in lead-acid batteries
  • Thermo-mechanical treated lead and lead alloys especially for current collectors and connectors in lead-acid batteries

Examples

Experimental program
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example # 2

EXAMPLE #2

[0081] A series of commercial lead alloys of the Class II type previously described, were obtained in a conventional cast condition in the form of strip. These strips were subsequently processed using the techniques described in the present invention. The specific alloys and processing conditions are summarized as follows.

[0082] A Pb-0.073 wt % Ca-0.07 wt % Sn alloy (Class II) was processed by three cycles each comprised of cold rolling at room temperature to achieve a 40% reduction in thickness, annealing at 270.degree. C. for 10 minutes in air followed by air cooling. The resulting microstructural improvement in terms of special grain boundary content is summarized in FIG. 5 (identified as PbCaSn in FIG. 5). The special grain boundary content was increased from 11% in the as-cast starting material, to 51% in the material processed by the method described.

[0083] A Pb-0.065 wt % Ca-0.07 wt % Sn 0.03 wt % Ag alloy (Class II) was processed by two cycles each comprised of col...

example # 3

EXAMPLE #3

[0087] A Pb-0.03 wt %Ca-0.7 wt. % Sn 0.06 wt %Ag alloy, representative of a Class I alloy was produced using a commercial rotary net shape casting process. The cast strip of 0.86-0.89 mm thickness was subsequently subjected to a single processing cycle comprised of approximately 20% cold tensile strain (room temperature), and heat treatment in an air convection oven at a temperature of 250.degree. C. for 5 minutes followed by cooling to ambient temperature. The strain was introduced at room temperature solely through the grid expansion process and was controlled by the tool die geometry (i.e., diamond height of expanded mesh). For comparison purposes a wrought strip was produced without subsequent recrystallization heat treatment. In this case, cast strip of 1.72 mm thickness was cold rolled by 50% and similarly expanded to mesh. The proportion of special grain boundaries present in the as-cast, wrought, and single step GBE processed materials were found to be 16.0%, 15.4%...

example # 4

EXAMPLE #4

[0089] Various lead alloys were subjected to the deformation and annealing cycle used to make the recrystallized lead-alloy according to this invention. Each of the samples was deformed at room temperature to 25% reduction in thickness and then annealed by heat-treating at 255.degree. C. for five minutes. After the deformation reduction and annealing, each of the aforementioned lead alloys was tested for hardness. A minimum of six hardness measurements at each of two locations of the test alloys were obtained using a Shimadzu model HMV2000 micro hardness tester utilizing a 25 g load. The hardness of each metal was also measured in the same way in the as-cast condition (i.e. without being subjected to deformation and annealing cycle). The f.sub.sp count of the as-cast material samples prior to GBE processing in all cases was between 10 and 15%. The results of the hardness test for each of the lead alloys is shown in Table 2. In all instances, the deformation reduction and h...

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Abstract

Recrystallized lead and lead alloy positive current collectors and connectors such as straps and lugs for use e.g. in lead acid batteries and electrowinning anodes, having an increased percentage of special grain boundaries in at least part of the microstructure, which have been provided by a process comprising of (i) cold or hot rolling or cold or hot extrusion or (ii) steps of deforming the lead or lead alloy, and subsequently annealing the lead or lead alloy. Either a single cycle of working and annealing can be provided, or a plurality of such cycles can be provided. The amount of deformation, the recrystallization time and temperature, and the number of repetitions of such steps are selected to ensure that a substantial increase in the population of special grain boundaries is provided in the microstructure, to improve resistance to creep, intergranular corrosion and intergranular cracking of the current collectors and connectors during battery service, and result in extended battery life and the opportunity to reduce the size and weight of the battery.

Description

[0001] This application is a Continuation-in-Part of pending application Ser. No. 09 / 412,610 filed Oct. 6, 1999, which is a Continuation-in-Part of application Ser. No. 08 / 977,518 filed Nov. 24, 1997, which is a Continuation-in-Part of application Ser. No. 08 / 835,926 filed Apr. 8, 1997 (abandoned), which is a Continuation of application Ser. No. 08 / 609,327 filed Mar. 1, 1996 (abandoned).[0002] This invention relates to wrought and recrystallized lead and lead alloys, with increased resistance to creep and intergranular cracking and corrosion. This invention is more particularly concerned with positive lead and lead alloy current collectors and connectors used in lead-acid batteries which. via recrystallization treatment to generate new grain boundaries in the microstructure, have improved resistance to corrosion and growth, so as to provide enhanced battery reliability, extended service life and greater energy density.[0003] Intergranular degradation (i.e., creep deformation, cracki...

Claims

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Application Information

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IPC IPC(8): C22C11/00C22F1/12H01M4/68H01M4/82
CPCC22C11/00H01M4/82H01M4/685C22F1/12Y02E60/10
Inventor AUST, KARL T.LIMOGES, DAVID L.GONZALEZ, FRANCISCOPALUMBO, GINOTOMANTSCHGER, KLAUSLIN, PETER K.
Owner AUST KARL T
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