Nickel-Hydrogen Battery Negative Electrode Fluororesin Distribution
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Solution Overview
Problem
Nickel-hydrogen secondary batteries face challenges in liquid leakage resistance during reverse charging and low-temperature discharge efficiency due to the use of fluororesin in the negative electrode mixture, which either reduces electrical conductivity or decreases discharge capacity.
Innovation Solution
A negative electrode with a fluororesin content distributed such that the inner layer portion has a higher fluororesin content than the outer layer portion, within specific mass and volume ranges, to reduce the contact area between the alkaline electrolyte and hydrogen storage alloy, enhancing liquid leakage resistance and low-temperature discharge efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fluororesin is mixed into the negative electrode mixture, then liquid leakage resistance during reverse charging is improved, but electrical conductivity of the negative electrode decreases
Solution Approach 1:
The patent applies local quality by creating a dual-layer structure where the outer layer contains fluororesin for water repellency and liquid leakage resistance, while the inner layer maintains high electrical conductivity for efficient charge discharge. This spatial differentiation of material properties resolves the contradiction between liquid leakage resistance and electrical conductivity.
Solution Approach 2:
The negative electrode is segmented into two distinct layers: an outer layer with fluororesin-containing mixture for protecting against electrolyte leakage, and an inner layer with high-conductivity mixture for efficient electrochemical performance. This segmentation allows each layer to optimize its specific function without compromising the other.
2Loss of energy
If fluororesin is applied to the surface of the negative electrode, then electrical conductivity is maintained, but discharge capacity decreases under low temperature environment
Solution Approach 1:
The patent applies local quality by creating a dual-layer structure where the outer layer contains fluororesin for water repellency and liquid leakage resistance, while the inner layer maintains high electrical conductivity for efficient charge discharge. This spatial differentiation of material properties resolves the contradiction between liquid leakage resistance and electrical conductivity.
Solution Approach 2:
The patent uses composite materials by combining fluororesin with conductive materials and active materials in specific ratios and distributions. The outer layer uses a composite of fluororesin and binding agent, while the inner layer uses a composite optimized for conductivity and electrochemical activity, achieving both protection and performance.
3Reliability
If fluororesin content is increased to improve liquid leakage resistance, then internal pressure control improves, but discharge capacity decreases
Solution Approach 1:
The patent applies local quality by creating a dual-layer structure where the outer layer contains fluororesin for water repellency and liquid leakage resistance, while the inner layer maintains high electrical conductivity for efficient charge discharge. This spatial differentiation of material properties resolves the contradiction between liquid leakage resistance and electrical conductivity.
Solution Approach 2:
The patent applies partial action by limiting fluororesin to only the outer layer rather than distributing it throughout the entire negative electrode. This partial application of fluororesin provides sufficient liquid leakage resistance while minimizing its negative impact on discharge capacity, as the inner layer remains free of fluororesin restrictions.
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 improves both liquid leakage resistance during reverse charging and low-temperature discharge efficiency by optimizing the distribution of fluororesin in the negative electrode mixture layer, ensuring effective hydrogen occlusion and electrolyte permeability.
Implementation Method 1
the contact area between the alkaline electrolyte and the hydrogen storage alloy decreases due to the water repellency of the fluororesin
Implementation Method 2
a part of the hydrogen is occluded in a hydrogen storage alloy in the negative electrode by a reaction represented by the following formula (II). 1/2H2 + M → MH + e-
Implementation Method 3
optimizing the distribution of fluororesin in the negative electrode mixture layer, ensuring effective hydrogen occlusion and electrolyte permeability
Data Source
Figure 1
Figure 2~3
AI summary
A nickel-hydrogen secondary battery (2) includes an electrode group (22) which contains a positive electrode (24), a negative electrode (26), and a separator (28), wherein the negative electrode (26) includes a negative electrode core, and a negative electrode mixture layer held by the negative electrode core, wherein the negative electrode mixture layer contains a fluororesin; a content of the fluororesin, expressed by a mass applied per unit area of the negative electrode (26), is within a range of 0.2 mg/cm2 or more and 2.0 mg/cm2 or less; and a fluororesin content which is a ratio of the fluororesin contained in a unit volume of the negative electrode mixture layer is higher in an inner layer portion than in an outer layer portion in the negative electrode mixture layer.