Lead-Calcium-Tin Negative Grid and Bismuth Boundary Layer for Lead Acid Battery

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Solution Overview

Problem

The use of bismuth at the boundary between negative straps and current collecting tabs in lead acid batteries can lead to a reduction in charge acceptance and electrical disconnection due to corrosion, especially as the electrolyte decreases.

Innovation Solution

A lead acid battery design featuring a negative electrode grid made of a lead-calcium-tin alloy with tin at 0.45 mass% or less, and a boundary layer containing 25-50 mass% bismuth at the interface between the negative electrode plate's current collecting tab and strap, along with an electrolyte containing 0.02-0.2 mol/L aluminum ions, to manage potential shifts and enhance charge acceptance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If bismuth is provided at the boundary between the negative strap and the current collecting tabs to suppress corrosion, then electrical disconnection due to corrosion is suppressed, but charge acceptance is reduced

Engineering Contradiction:

Improveelectrical disconnection resistanceVSAvoidcharge acceptance

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The invention applies local quality by providing bismuth specifically at the boundary between the negative strap and current collecting tabs where corrosion occurs, rather than uniformly distributing it throughout the electrode structure. This localized application suppresses corrosion at the critical interface while minimizing the negative impact on charge acceptance by limiting bismuth to only where it is needed for corrosion protection.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention changes the concentration parameter of bismuth from uniform distribution to localized high concentration at the boundary (25-50 mass% in the boundary layer). This parameter change allows sufficient corrosion protection at the interface while controlling the overall amount of bismuth to minimize its detrimental effect on charge acceptance.

Inventive Principle:

Principle #35Parameter changes

2Strength

If tin content in the negative electrode grid is increased to improve grid strength, then grid mechanical strength is improved, but charge acceptance is reduced due to potential shift

Engineering Contradiction:

Improvegrid mechanical strengthVSAvoidcharge acceptance

Core Design Contradiction:

StrengthVSUse of energy by moving object

Solution Approach 1:

The invention optimizes the tin content parameter in the negative electrode grid alloy to 0.45 mass% or less. This parameter change balances the competing requirements: maintaining sufficient grid mechanical strength while preventing excessive potential shift that would reduce charge acceptance. The specific tin content threshold represents the optimal balance point between these two competing factors.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention uses a composite lead-calcium-tin alloy for the negative electrode grid, combining multiple elements to achieve both mechanical strength and appropriate electrochemical potential. The composite alloy formulation allows the grid to maintain structural integrity with lower tin content than would be required in a single-element lead grid, thereby preserving charge acceptance while ensuring mechanical strength.

Inventive Principle:

Principle #40Composite materials

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

This configuration effectively suppresses corrosion-related disconnections and improves charge acceptance, ensuring reliable performance even under deep discharge conditions, particularly in vehicles with idling stop systems.

Implementation Method 1

providing bismuth (lead-bismuth alloy) at the boundary between the negative strap and the current collecting tabs (ears) as taught by Patent Literature 1, unlike providing tin (lead-tin alloy), can suppress the occurrence of electrical disconnection due to corrosion

Methodology Applied

Scientific EffectCorrosion resistance:

Implementation Method 2

The negative electrode grid comprises a lead-calcium-tin alloy containing tin in an amount of 0.45 mass% or less

Methodology Applied

Scientific EffectElectrochemical reaction:

Implementation Method 3

the electrolyte contains aluminum ion at a concentration of 0.02 mol/L or more and 0.2 mol/L or less

Methodology Applied

Scientific EffectIon conduction:

Data Source

PatentEP3273512B1Lead storage cell

Publication Date: 2023.02.15 GS YUASA INT LTD

Figure 1
Figure 2~3

AI summary

A lead acid battery including: positive and negative electrode plates each including a positive or negative electrode grid and a positive or negative electrode active material, the positive and negative electrode plates being stacked alternately with a separator therebetween to form an electrode plate group. The battery further includes: positive and negative straps integrated with current collecting tabs of the positive or negative electrode plates collectively for each electrode plate group; a battery container having a plurality of cell chambers each containing the electrode plate group and an electrolyte; and a cover sealing an opening of the battery container. A boundary layer containing bismuth is provided at a boundary between the current collecting tab of the negative electrode plate and the negative strap. The negative electrode grid comprises a lead-calcium-tin alloy containing tin in an amount of 0.45 mass% or less.