Alkaline batteries are mainly composed of positive and negative electrodes, electrolytes, current collectors, separators, and other materials. Among them, the separator plays an important role in alkaline batteries. This post will explain the meaning of separators, the role of separators, the manufacturing technology of separators, and the development direction of separators.
What is a separator
The separator is located between the positive and negative electrodes of the battery, and is used to isolate the active materials of the positive and negative electrodes of the battery to prevent the active materials of the positive and negative electrodes from directly contacting each other and causing a short circuit in the battery. It plays an irreplaceable and important role in alkaline batteries. Many discussions and research on the development of alkaline battery technology focus on separator technology.
The role of the separator
In the alkaline battery manufacturing process, the performance requirements of the separator and the role it can play have many aspects, roughly including:
1. The separator needs to have a stable, evenly distributed, and concentrated pore structure that can allow ions to pass smoothly while blocking electrons from intervening.
2. The separator needs to have good stability. It cannot react chemically in the alkaline electrolyte, and the size of the separator must be stable and not easy to deform.
3. The separator must be able to meet the requirements of good ion conductivity under continuous battery discharge, especially under high-power discharge conditions.
4. During the preparation process of the separator, the impurity content must be strictly controlled, especially the content of metal particles such as iron and copper must not exceed the standard, otherwise it may cause self-discharge.
The manufacturing technology of separator
The manufacturing materials of the separator use a variety of different types of fibers, such as vinyl fiber, hardwood fiber, bonding fiber, etc. Among them, vinyl fiber has good alkali resistance, hardwood fiber has good strength and absorption capacity, and bonding fiber can further improve the strength of the separator.
In addition to these three materials, some separators will also add viscose fiber, tencel fiber, etc., the main purpose of which is to improve the strength of the separator and adjust the pore size of the separator.
The separator materials listed above have some common characteristics, but in fact, there are some differences between the products produced by different battery separator manufacturers. Generally speaking, separators with good strength, uniform pore distribution, and more stable quality will be more popular in the market.
The development direction of separator
Alkaline batteries are developing towards higher capacity and greater current. In this case, reducing the thickness of the separator and increasing the amount and ratio of battery electrode materials are effective ways to increase the energy density of the battery. The future development direction of the separator must also be accompanied by this trend. Its development direction can be mainly divided into the following points:
1. Improve the pore structure of the separator
The main function of the separator is to provide a channel for the transmission of ions and prevent direct contact between the positive and negative electrodes.
Theoretically, the smaller the pore size of the separator, the slower the migration rate of ions, and the larger the pore size of the separator, the higher the ion passage rate. However, if the pore size of the separator is too large, the battery may experience self-discharge and short circuit. If the pore size is too small, it may cause excessive deposition of zinc and reduce the battery life.
Therefore, the separator needs to have good uniformity, and the distribution of pore size should be more concentrated. This can avoid problems caused by too large or too small pore size.
2. Improve the alkali resistance of the separator
Alkaline batteries use alkaline electrolytes, and the batteries may be in a high temperature environment during the manufacturing process. Therefore, the battery separator needs to have good alkali resistance and high temperature resistance.
To achieve this goal, the separator needs to use fiber raw materials with good alkali resistance and high temperature resistance. Today, vinyl fiber is the main raw material for battery separators because it has good stability in strong alkaline solutions. However, to improve the liquid absorption capacity and strength of the separator, many manufacturers will add some other substances (such as plant fibers and renewable fibers) to the raw materials, which leads to a decrease in the alkali resistance of the separator. The mixed use of fibers of different types and different properties increases the difficulty of separator manufacturing.
Therefore, in terms of raw materials, it is necessary to find a new fiber material with alkali resistance comparable to vinyl fiber and better strength and liquid absorption capacity.
3. Improve the manufacturing process of separators
At present, the production line of alkaline batteries has been automated, which is a good phenomenon. But at the same time, this also poses challenges to the strength performance and liquid absorption capacity of the separator.
In the production process of alkaline batteries, the separator needs to have good tensile strength to overcome the tension caused by the equipment. In addition, when the battery is hit, the separator also needs to be light enough to maintain itself from breaking, to ensure the safety of the battery.
During the manufacturing process of alkaline batteries, the manganese dioxide of the positive electrode, the zinc powder of the negative electrode, and the separator will adsorb the alkaline electrolyte. Any component that adsorbs too much or too little alkaline solution will affect the discharge performance of the battery. In terms of separators, its washing capacity can be regulated by processing raw materials, fiber ratio, etc.
4. Control the metal impurities in the separator
Heavy metal impurities (such as Fe, Cu, Pb, etc.) in the separator have a great influence on the electrochemical performance of alkaline batteries. Metal impurities will produce hydrogen evolution reaction with the negative electrode in the electrolyte, which will accelerate the corrosion of the negative electrode zinc powder. Therefore, some means should be used to strictly control the content of metal impurities in the manufacturing process of the separator.
5. Reduce the thickness of the separator
Under the premise that the volume of the alkaline battery remains unchanged, the use of thinner separators can increase the filling space of the active materials at both ends of the battery, thereby improving the energy density of the battery.
However, it should be noted that the thinner the separator, the lower its physical strength and liquid absorption efficiency. Therefore, the manufacturing technology that reduces the thickness of the separator without damaging the performance of the separator has always been the research direction.
The above article gives you a detailed introduction to the relevant information of alkaline battery separators, I hope it will be helpful to you.
About the Author
Liteway is a professional manufacturer and supplier of alkaline batteries, carbon-zinc batteries, and lithium batteries based in Ningbo, China.
We have more than 20 years of manufacturing and exporting experience in the battery field, providing battery manufacturing and OEM/ODM services to customers all over the world. We are a co-manufacturer for many battery brands and have been unanimously recognized by our partners during the cooperation process.
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