Zinc Electrode Composition to Suppress Dendrites in Ni-Zn Batteries
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Solution Overview
Problem
The existing alkaline nickel-zinc batteries face issues with zinc oxide solubility in the electrolyte, leading to zincate ion diffusion, electrode deformation, and dendrite growth, which reduces cycle life and performance.
Innovation Solution
A zinc electrode is prepared with a water-soluble calcium salt of organic acid, a binder, and a thickener, allowing in-situ formation of calcium zincate to anchor zincate ions, reducing solubility and dendrite growth, and using a mercury-free zinc alloy to inhibit hydrogen evolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If zinc oxide is used as the active material in the zinc electrode, then the battery can achieve electrochemical energy storage and conversion, but the zinc oxide dissolves in the alkaline electrolyte to form freely movable zincate ions, causing electrode deformation and dendrite growth
Solution Approach 1:
The patent introduces calcium hydroxide as an intermediary substance that mediates between zinc oxide and the alkaline electrolyte. Calcium hydroxide reacts with zincate ions to form insoluble calcium zincate, effectively removing the harmful zincate ions from the electrolyte and preventing dendrite growth while maintaining the electrochemical function of zinc oxide
Solution Approach 2:
The patent converts the harmful effect of zincate ion formation into a beneficial process by having calcium hydroxide react with zincate ions to form insoluble calcium zincate. This transforms the harmful soluble zincate ions into a beneficial insoluble precipitate that can be easily removed and prevents electrode deformation and dendrite growth
2Duration of action of stationary object
If insoluble calcium salts such as calcium hydroxide are added to the zinc electrode to inhibit zinc oxide dissolution, then the cycle life is prolonged, but the mixing uniformity of the slurry deteriorates due to large differences in density and particle size
Solution Approach 1:
The patent changes the particle size parameter of calcium hydroxide to the nano-scale (1-100 nm), which dramatically improves its dispersibility and mixing uniformity in the slurry. This parameter change allows the calcium hydroxide to be uniformly distributed throughout the zinc electrode without the severe aggregation problems that occur with larger particles, while still maintaining the function of inhibiting zinc oxide dissolution
3Stability of the object's composition
If micron-scale or sub-micron-scale insoluble calcium salts are used as additives, then the solubility of zinc oxide is inhibited, but the anchoring effect on zincate ions is poor and the internal calcium element cannot interact with zincate ions effectively
Solution Approach 1:
The patent utilizes the high surface area to volume ratio inherent in nano-scale materials to create numerous anchoring sites for zincate ions. The nano-scale calcium hydroxide particles provide a vastly increased surface area compared to micron-scale particles, enabling effective interaction and anchoring of zincate ions throughout the zinc electrode structure
Solution Approach 2:
The patent applies calcium hydroxide locally at the nanoscale throughout the zinc electrode structure, creating numerous localized anchoring sites for zincate ions. This distributed local quality approach ensures that zincate ions can be effectively captured at multiple locations within the electrode, significantly improving the overall anchoring effect compared to using larger particles
4Duration of action of stationary object
If calcium oxide is used as an additive to inhibit zinc oxide dissolution, then the cycle life is improved, but a large amount of heat is generated during manufacturing, consuming water and destroying the binder structure
Solution Approach 1:
The patent changes the chemical composition parameter from calcium oxide to calcium hydroxide, which fundamentally alters the thermal properties of the additive. Calcium hydroxide does not undergo the highly exothermic hydration reaction that calcium oxide does, thereby eliminating the problematic heat generation during manufacturing while still providing the necessary function of inhibiting zinc oxide dissolution through the formation of insoluble calcium zincate
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 enhances the utilization rate of active materials, improves discharge capacity, and prolongs the cycle life of the battery by uniformly distributing calcium to inhibit zincate ion diffusion and dendrite growth, while avoiding equipment corrosion and impurity introduction.
Implementation Method 1
the calcium hydroxide additive can bond to zinc oxide and an intermediate product of charge and discharge, to form an insoluble phase, called calcium zincate
Implementation Method 2
the solubility of zinc oxide is about 54 g/L in a 30 wt. % potassium hydroxide solution, and can be as high as 80 g/L in a 45 wt. % potassium hydroxide solution
Implementation Method 3
the zinc electrode, as a negative electrode part of the nickel-zinc battery, mainly undergoes reversible electrochemical conversion reactions between zinc oxide and metal zinc
Data Source
AI summary
Disclosed is a preparation method for a zinc electrode, including: a step of dissolving a water-soluble calcium salt of organic acid in deionized water to obtain a first mixed solution; a step of preparing a negative electrode slurry by mixing the first mixed solution, a water-soluble binder, a thickener, and an active material including zinc oxide; and a step of preparing the zinc electrode by applying the slurry to a surface of a current collector and baking it at a high temperature. Further disclosed is a zinc electrode prepared by the preparation method, and use of the zinc electrode in an alkaline nickel-zinc battery. The zinc electrode prepared in the present disclosure can not only effectively improve the deformation thereof and solve the growth problem of zinc dendrites, but also contribute to increasing the utilization rate of an active material of the zinc electrode and improving the cycle performance of the alkaline nickel-zinc battery.