Lead Alloy Positive Current Collector for High Draft Rate Rolling
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Solution Overview
Problem
The conventional rolling process for lead-acid battery current collectors using lead alloys with impurities like Bi faces limitations in increasing draft rate, which reduces creep durability and battery performance.
Innovation Solution
A lead-acid battery with a positive current collector made from a lead alloy containing 0.05-0.1% Ca, 1.2-2.2% Sn, 0.002-0.03% In, and 0.001-0.04% Bi, subjected to a rolling process at 80-97.5% draft rate, enhancing lattice density and durability while suppressing intergranular corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the draft rate in the rolling process is increased to improve lattice density and battery performance, then the cycle life and battery performance are improved, but the intergranular corrosion is accelerated and creep durability is reduced
Solution Approach 1:
The patent changes the chemical composition parameters of the lead alloy by precisely controlling the content of Ca (0.03-0.1 mass%), Sn (1.0-2.5 mass%), and In (0.01-0.5 mass%). This compositional parameter optimization suppresses intergranular corrosion while enabling high draft rate rolling, thereby resolving the contradiction between improving cycle life through increased lattice density and maintaining creep durability.
Solution Approach 2:
The patent creates a composite lead alloy system combining multiple elements (Pb-Ca-Sn-In) where each element contributes specific properties. Ca and Sn provide base structural stability, while In specifically suppresses intergranular corrosion. This composite material approach allows the alloy to withstand high draft rate rolling without excessive corrosion, thus improving both cycle life and maintaining creep durability.
2Reliability
If the draft rate in the rolling process is increased to improve lattice density, then the battery performance is improved, but the manufacturing complexity and process control difficulty increase
Solution Approach 1:
The patent performs preliminary optimization of the alloy composition before the rolling process. By pre-establishing the optimal Ca-Sn-In content ratios in the molten alloy, the material is prepared in advance to withstand high draft rate rolling without excessive corrosion. This preliminary compositional design simplifies subsequent process control compared to attempting to manage corrosion issues during or after rolling.
3Ease of manufacture
If impurities like Bi are present in the lead alloy to reduce raw material cost, then the manufacturing cost is reduced, but the creep durability is reduced when high draft rate is applied
Solution Approach 1:
The patent acknowledges that Bi impurities (0.001-0.04 mass%) are present and potentially harmful to creep durability. However, by optimizing the Ca-Sn-In composition, the patent converts this harmful effect into a manageable parameter. The In content specifically counteracts the negative effects of Bi, allowing the use of lower-cost alloy compositions while maintaining adequate creep durability through the synergistic effect of the multi-element system.
Data Source
AI summary
A lead-acid battery provided herein has attained improved battery characteristics and durability at the same time even if a lead alloy containing impurities is used for an electrode current collector. A negative electrode and a positive electrode are stacked via a separator to form an electrode group. The electrode group is housed in a battery case together with an electrolyte. The negative electrode includes a negative current collector on which a negative active material is held. The positive electrode includes a positive current collector on which a positive active material is held. The positive current collector is made of a lead alloy which contains 0.05 to 0.1% by mass of Ca, 1.2 to 2.2% by mass of Sn, and 0.002 to 0.03% by mass of In and contains, as unavoidable impurities, at least 0.001 to 0.04% by mass of Bi, the remainder being Pb. The lead alloy is subjected to a rolling process at a draft rate of 80 to 97.5%.