Ni-MH Battery Electrode and Separator Design for High-Temperature Overcharge
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Solution Overview
Problem
Existing Ni-MH batteries experience performance degradation and reduced lifetime at high temperatures, with charging efficiency decreasing and internal resistance increasing due to oxygen evolution and hydrogen storage alloy corrosion, leading to a limited effective lifetime of less than 4 years at 40°C.
Innovation Solution
The Ni-MH battery design includes a positive electrode with spherical nickel hydroxide coated using chemical vapor deposition, positive electrode additives containing tungsten and zinc, and a fluorinated polypropylene separator, along with an alkaline electrolyte and negative electrode additives with yttrium, which enhance oxygen evolution potential, reduce internal resistance, and improve durability, allowing for extended high-temperature operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If Ni-MH battery is used at high temperature (≥40°C), then power characteristics are maintained, but charging efficiency decreases and performance degrades rapidly
Solution Approach 1:
The patent modifies the chemical composition parameters of the hydrogen storage alloy by adding specific elements (Fe, Ga, Zn, Sn, Si, B, Nb, W, Mo, V, Cr, Ta, Li, P, S) to change the electrochemical properties. This allows the battery to maintain better charging efficiency at high temperatures by adjusting the alloy's resistance to oxygen evolution and corrosion
Solution Approach 2:
The patent creates a composite hydrogen storage alloy system combining CaCu5-type base structure with multiple dopant elements. This composite material approach synergistically improves both power characteristics and high-temperature reliability by distributing different functional elements throughout the alloy matrix
2Duration of action of moving object
If Ni-MH battery operates at 40°C for long-term float charging, then continuous power supply is achieved, but internal resistance increases and discharge capacity decreases
Solution Approach 1:
The patent converts the harmful effect of oxygen evolution at high temperature into a beneficial process by designing the alloy to control oxygen recombination. The oxygen that would normally cause corrosion is instead managed through controlled evolution and recombination mechanisms, extending battery life while maintaining continuous operation capability
Solution Approach 2:
The patent performs preliminary alloying during manufacturing, pre-introducing protective elements (particularly Fe and Ga) that form protective surface layers before the battery enters service. This preliminary protection prevents subsequent corrosion during long-term float charging at elevated temperatures
3Productivity
If hydrogen storage alloy is exposed to strong alkaline environment at high temperature, then electrochemical reactions proceed, but alloy corrosion increases and water is consumed
Solution Approach 1:
The patent applies local quality by creating surface-enriched zones with specific protective elements (Fe, Ga, Zn) that form corrosion-resistant surface layers. The bulk alloy maintains high reactivity for electrochemical reactions, while the surface layer locally protects against alkaline corrosion and water consumption
Solution Approach 2:
The patent introduces intermediate protective elements (particularly Fe and Ga) that act as mediators between the aggressive alkaline electrolyte and the hydrogen storage alloy matrix. These intermediaries form stable surface compounds that prevent direct contact between the electrolyte and the reactive alloy, reducing water consumption while allowing electrochemical reactions to proceed
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 solution effectively increases the Ni-MH battery's lifetime to no less than 10 years at 40°C, maintaining discharge capacity above 75% of nominal capacity and preventing electrolyte leakage, while maintaining separator durability and reducing corrosion.
Implementation Method 1
the spherical nickel hydroxide is coated with β-CoOOH by chemical vapor deposition process
Implementation Method 2
The W element of the positive electrode additive can slowly be dissolved to form Na 2 WO 4
Implementation Method 3
The separator of the Ni-MH battery is made of grafted or fluorinated or sulfonated polypropylene separator. The fluorinated or grafted polypropylene separator will not embrittle under high temperature environment for a long time
Data Source
Figure 1~2
AI summary
The invention relates to a Ni-MH battery. The positive electrode active material of the Ni-MH battery is made of spherical nickel hydroxide coated with β-CoOOH; the positive electrode additive used in the positive electrode of the nickel-hydrogen battery comprises tungsten and zinc, and the positive electrode additive further comprises at least one of yttrium and ytterbium. The separator of the battery is made of grafted or fluorinated or sulfonated polypropylene separator. The electrolyte of the Ni-MH battery is an alkaline aqueous solution composed of alkali metal hydroxide, and the concentration of alkali metal hydroxide is 5.5 - 8.0 mol /L. The negative electrode additive used in the negative electrode of the Ni-MH battery comprises yttrium. The Ni-MH battery can effectively reduce the increase in internal resistance of the Ni-MH battery during long-term overcharging in a high-temperature environment, and prolong the service life of the Ni-MH battery.