Lead Alloy Positive Electrode Corrosion Resistance
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Solution Overview
Problem
Conventional lead storage batteries face issues with intergranular corrosion of the positive electrode lead layer, leading to increased internal resistance and potential liquid junction phenomena, especially when the layer is thinned to reduce weight and improve volume utilization.
Innovation Solution
A lead alloy with specific compositions (0.4-2% tin, 0.004% bismuth or less, and optional 0.1% calcium and silver) is developed, where image analysis of crystal orientation distribution maps identifies misorientation boundaries with a crystal misorientation of 5° or more, and the average distance between intersection points is 50 μm or less, forming a dense lattice that suppresses corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the lead layer for positive electrode is reduced in thickness to reduce the weight of the battery and improve volume utilization, then the weight and volume are improved, but the corrosion penetration risk increases due to shorter diffusion path
Solution Approach 1:
The patent changes the chemical composition parameters of the lead alloy by precisely controlling tin content (0.4-2% by mass) and limiting bismuth content (0.004% by mass or less). This compositional parameter change modifies the corrosion behavior and crystal structure of the alloy, enabling thin lead layers to resist corrosion penetration while maintaining reduced weight
Solution Approach 2:
The patent creates a composite alloy system by combining lead with specific amounts of tin and trace amounts of bismuth control. This composite material approach leverages the synergistic effects of different elements to achieve both thin-layer structural integrity and corrosion resistance, resolving the contradiction between reduced thickness and improved reliability
2Volume of stationary object
If the lead layer for positive electrode is reduced in thickness to improve volume utilization, then the volume efficiency is improved, but the internal resistance increases due to corrosion breaking electrical conduction paths
Solution Approach 1:
By adjusting the alloy composition parameters (tin: 0.4-2%, bismuth: ≤0.004%), the patent modifies the electrochemical properties and corrosion resistance of the lead alloy. This enables the use of thinner lead layers that maintain electrical conduction integrity, thus improving volume utilization while preventing internal resistance increase
Solution Approach 2:
The patent converts the potential harm of thin lead layers (which are more susceptible to corrosion) into a benefit by using controlled alloying. The specific composition creates a protective effect where the thin layer structure, when properly alloyed, actually performs better than conventional thicker layers by preventing corrosion-induced conduction path breaks
3Ease of manufacture
If conventional lead alloys are used in the lead layer for positive electrode, then the manufacturing simplicity is maintained, but the intergranular corrosion proceeds along grain boundaries causing penetration
Solution Approach 1:
The patent modifies the chemical composition parameters of conventional lead alloys by specifying tin content (0.4-2% by mass) and strictly limiting bismuth content (0.004% by mass or less). This parameter change transforms the alloy's grain boundary properties, preventing intergranular corrosion while maintaining compatibility with existing manufacturing processes
Solution Approach 2:
The patent applies local quality control by precisely managing the distribution and concentration of alloying elements, particularly keeping bismuth at very low levels (≤0.004%). This localized compositional control prevents corrosion initiation at grain boundaries while maintaining overall manufacturing simplicity and process compatibility
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The lead alloy effectively reduces the likelihood of corrosion penetration through the lead layer in the thickness direction, maintaining low internal resistance and prolonging battery life, even when the layer is reduced in thickness, thereby enhancing battery performance and capacity.
Implementation Method 1
when image analysis of a crystal orientation distribution map created by analyzing the surface by an electron backscatter diffraction method is performed
Data Source
AI summary
A lead alloy is described that is capable of manufacturing a positive electrode for a lead storage battery less likely to cause corrosion penetrating through a lead layer for the positive electrode in the thickness direction. The lead alloy contains 0.4% by mass or more and 2% by mass less of tin and 0.004% by mass or less of bismuth, with the balance being lead and inevitable impurities. When image analysis of a crystal orientation distribution map created by analyzing the surface of the lead alloy by an electron backscatter diffraction method is performed, intersection points of misorientation boundaries between crystal grains with a crystal misorientation of 5° or more and a straight line extending in one specific direction are extracted. The distances between two adjacent intersection points among the extracted intersection points are measured, and the average value of the distances is 50 μm or less.