VRLA Battery Electrode Composition for Lower Self-Discharge
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Solution Overview
Problem
Lead-acid batteries suffer from self-discharge, leading to the accumulation of lead sulfate, which reduces their life performance and decreases electrolyte solution specific gravity, especially in valve regulated lead-acid batteries.
Innovation Solution
Incorporating a polymer compound with specific chemical shifts and densities in the negative and positive electrode materials, reducing the self-discharge by minimizing electrolyte penetration and oxygen gas generation, and using a polymer compound with oxy C2-4 alkylene units to cover the lead surface thinly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the battery operates as a valve regulated lead-acid battery with limited electrolyte, then the battery structure is compact and sealed, but the specific gravity of electrolyte decreases rapidly during self-discharge
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition parameters of the electrode materials. Specifically, it controls the Pb content in the negative electrode material at 70-90 mass% and PbO2 content in the positive electrode material at 70-90 mass%, while adding specific additives like calcium carbonate (0.1-5 mass%) and organic expanders. These parameter adjustments optimize the electrode structure to reduce self-discharge rates, thereby maintaining electrolyte specific gravity in the compact sealed battery structure.
Solution Approach 2:
The patent employs composite materials by combining lead-based active materials with various additives and binders. The negative electrode material comprises Pb, PbO, PbO2, and additives including calcium carbonate, barium sulfate, and organic expanders. The positive electrode material comprises PbO2, PbSO4, and similar additives. These composite structures improve electrode stability and reduce self-discharge, addressing the electrolyte specific gravity degradation issue in compact sealed battery designs.
2Ease of manufacture
If the battery uses conventional electrode materials, then the manufacturing process is simple, but lead sulfate accumulates during self-discharge reducing battery life
Solution Approach 1:
The patent applies parameter changes by precisely controlling the composition ratios of electrode materials. The negative electrode material contains Pb (70-90 mass%), PbO (5-20 mass%), PbO2 (5-20 mass%), and specific additives. The positive electrode material contains PbO2 (70-90 mass%), PbSO4 (5-20 mass%), and similar components. These parameter optimizations reduce lead sulfate accumulation during self-discharge while maintaining manufacturability through conventional mixing and forming processes.
Solution Approach 2:
The patent applies local quality by creating heterogeneous electrode structures with different functional regions. The electrodes contain active materials, conductive agents, binders, and pore-forming agents in specific distributions. This local compositional variation optimizes both electron conduction and ion transport pathways, reducing self-discharge-induced lead sulfate accumulation while maintaining ease of manufacture through batch mixing techniques.
3Quantity of substance
If the positive electrode material density is increased to improve energy density, then the battery capacity increases, but self-discharge increases due to greater oxygen gas generation
Solution Approach 1:
The patent applies parameter changes by optimizing the density and composition of the positive electrode material. It specifies PbO2 content at 70-90 mass% and adds calcium carbonate (0.1-5 mass%) and organic expanders to control the physical structure. These parameter adjustments increase battery capacity while the organic expanders and calcium carbonate suppress oxygen gas generation and self-discharge by modifying the electrode's porosity and surface properties.
Solution Approach 2:
The patent uses calcium carbonate and organic expanders as intermediary substances in the positive electrode material. These intermediaries mediate between the high-density PbO2 active material and the electrolyte, controlling oxygen evolution and reducing self-discharge. The intermediaries fill pores and modify surface characteristics, allowing high capacity while minimizing harmful oxygen gas generation and self-discharge effects.
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
Significantly reduces self-discharge, prolonging the battery's life and maintaining electrolyte density, suitable for small mobility applications.
Implementation Method 1
using a polymer compound with oxy C2-4 alkylene units to cover the lead surface thinly
Data Source
AI summary
A valve regulated lead-acid battery includes at least one cell including an element and an electrolyte solution. The element includes a negative electrode plate, a positive electrode plate, and a separator interposed between the negative electrode plate and the positive electrode plate. The negative electrode plate includes a negative electrode material. The negative electrode material contains a polymer compound having a peak in a range of 3.2 ppm or more and 3.8 ppm or less in a chemical shift of a 1H-NMR spectrum measured using deuterated chloroform as a solvent, or contains a polymer compound having a repeating structure of oxy C2-4 alkylene units. The positive electrode plate includes a positive electrode material. A density of the positive electrode material is 3.70 g/cm3 or more and 4.65 g/cm3 or less.