Lead-Acid Battery Negative Electrode Shrinkage Prevention
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Solution Overview
Problem
Lead-acid batteries face a degradation issue where the negative active material shrinks in the thickness direction when a tin compound is included in the positive active material, leading to reduced cycle life performance due to increased bulk density and decreased pore volume, making charge-discharge with heavy currents difficult.
Innovation Solution
Incorporating carbon black in the negative active material in an amount of 0.4% to 2.0% by mass and a tin compound in the positive active material in an amount of 0.5% to 3.0% by mass, along with applying compressive force between the positive and negative electrode plates in a valve regulated lead-acid battery, to prevent shrinkage of the negative active material and enhance cycle life performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tin compound is included in the positive active material to prevent corrosion of the positive electrode grid, then grid corrosion resistance is improved, but the negative active material shrinks in thickness direction leading to reduced cycle life
Solution Approach 1:
Carbon black is introduced as an intermediary substance in the negative active material. It mediates between the tin compound in the positive active material and the negative active material structure, preventing the harmful shrinkage effect while allowing the beneficial corrosion prevention effect to occur. The carbon black acts as a structural buffer that maintains pore volume and prevents bulk density increase.
Solution Approach 2:
The invention changes the compositional parameters of the negative active material by adding carbon black within a specific range (0.4% to 2.0% by mass). This parameter change counteracts the shrinkage tendency induced by the tin compound, maintaining the thickness and pore structure of the negative active material throughout charge-discharge cycles.
2Quantity of substance
If the negative active material shrinks in thickness direction, then bulk density increases, but pore volume decreases making charge-discharge with heavy currents difficult
Solution Approach 1:
Carbon black is added to maintain and enhance the porous structure of the negative active material. The carbon black particles fill voids and prevent pore collapse during shrinkage, ensuring that pore volume is maintained even as bulk density increases slightly. This preserved porosity allows efficient ion transport for heavy current charge-discharge operations.
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 inclusion of carbon black and tin compound within specified ranges significantly improves charge-discharge cycle life by preventing negative active material shrinkage, maintaining charge acceptability, and ensuring efficient charge-discharge performance even at heavy currents.
Implementation Method 1
the negative active material shrinks in a thickness direction. In this case, life performance in a cycle charge-discharge life test is defined by shrinkage of a negative active material. Dropout and the like of an active material could not be detected, and the bulk density of a negative active material increased with shrinkage of the negative active material. According to a charge-discharge model of a lead-acid battery, the pore volume decreases and charge-discharge with a heavy current becomes difficult when the bulk density of a negative active material increases.
Implementation Method 2
it has been found that life performance is defined by corrosion of a positive electrode grid when a tin compound is not included in a positive active material; and when a tin compound is included in an amount of 1% by mass on a metal tin basis, corrosion of a positive electrode grid can be prevented
Implementation Method 3
In the valve regulated lead-acid battery, shrinkage of the negative active material is suppressed owing to a compressive force applied to the negative electrode plate, so that cycle life performance is further improved.
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A lead-acid battery includes a positive electrode plate including a positive electrode grid and a positive active material filled in the positive electrode grid and formed in advance, a negative electrode plate 2 including a negative electrode grid 4 and a negative active material 6 filled in the negative electrode grid 4 and formed in advance, and an electrolyte solution. The positive active material contains a tin compound in an amount of 0.5% by mass to 3.0% by mass (inclusive) on a metal tin basis, and the negative active material 6 contains carbon black in an amount of 0.4% by mass to 2.0% by mass (inclusive). Shrinkage of the negative active material 6 in a thickness direction in a charge-discharge cycle is prevented to improve the charge-discharge life performance.