Due to the characteristics of the material itself, wet and dry diaphragms have their own advantages and disadvantages:
The wet-process diaphragm is light and thin, not easy to tear, but the melting point of PE is 135&#;, which is less safe than the dry-process diaphragm. In addition to the different raw materials and production processes, the overall cost is higher than that of the dry-process diaphragm; It has better high-pressure resistance and oxidation resistance, but it is thicker than wet-process separators and is prone to longitudinal tearing, which requires higher process requirements for battery companies.
With the rapid expansion of ternary power batteries, especially high-nickel power batteries, the need for diaphragms with the advantages of high safety, strong functionality, and low cost is imminent, which has become the direction of joint efforts of domestic diaphragm companies. The "three-layer composite membrane" developed by the international diaphragm giant Celgard may be able to inspire some domestic counterparts.
The middle layer of Celgard's "three-layer composite film" is polyethylene, which has a melting point of about 132°C. When the battery is out of control and heats up, the polyethylene will melt, closing the pores and cutting off the circuit, which can form safety protection for the battery; the outer two layers are polypropylene, It has oxidation resistance and the melting point is above 165&#;. Even if the battery temperature rises slightly, the physical shape of the membrane will not be affected, providing a second layer of safety protection for the battery.
In addition to high safety, Celgard President Shi Lie publicly stated that the dry process of the company's "three-layer composite membrane" products is greener and environmentally friendly than wet membranes.
Wet process requires chemical solvents and solutions. Although manufacturers are working hard to recover them, some will evaporate into the air in the end, which is harmful to people and the environment.
Shi Lie disagrees with the view that some people in China believe that the application of wet-process separators in the field of power batteries is broader. In his opinion, at the beginning of the rise of new energy vehicles, dry-process diaphragms dominated because wet-process products had relatively poor oxygen resistance and large lateral shrinkage; they would melt when the temperature reached 130°C, which was very limited; in terms of strength, The wet-process diaphragm drops by more than 50% after a period of use, while the three-layer composite film hardly changes, and its life span is longer than that of the wet-process polyethylene diaphragm.
From an objective point of view, after the wet-process diaphragm is coated, it will effectively avoid the "defects" in the inherent characteristics of the material, but this will increase the cost.
At present, most domestic ternary power battery systems use "wet method + coating". Based on cost considerations, dry-method separators with progressively improved performance have been used in large quantities for lithium iron phosphate systems, and they have also begun to be applied to ternary systems. The leading enterprises of the meta-system also use dry-process diaphragms.
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At present, the proportion of high-nickel power batteries in the world is not high. Whether "wet method + coating" can simultaneously meet the requirements of high safety, strong functionality, and low-cost separators, it remains to be further verified.
Shi Lie said that the three-layer composite membrane is the only separator that can be used in high-energy batteries without coating, and the direct use of the base membrane will be more competitive than the polyethylene ceramic separator.
"Different customers or different battery designs sometimes require us to coat a layer of ceramics, so the price will be more expensive." Shi Lie added that Celgard has many successful cases in Japan, South Korea and some Chinese battery manufacturers. In the past many years, the market has given very good feedback on CELGARD's "three-layer composite membrane", especially in electric vehicles and energy storage batteries, and there has never been a safety accident, and the reliability is very guaranteed. We welcome more battery manufacturers to make more attempts and cooperation.
It is understood that Celgard is the "originator" of the global dry-process diaphragm technology. It has a history of 30 to 40 years in the diaphragm industry and is now a subsidiary of Asahi Kasei. Most of China's dry process diaphragm companies have followed Celgard's dry process, but what Chinese manufacturers cannot replicate at present is the "three-layer composite membrane" developed and imported by Celgard.
"We started to study three-layer membranes as early as a few years ago, but there was no matching production equipment at the time, and one of the raw materials needed to be imported from abroad." A senior executive of a domestic dry-process diaphragm company said that most of the domestic double-layer membranes are produced. Because not be thin'.
However, with the continuous improvement of raw materials, production equipment, and process technology, some domestic dry-process diaphragm companies are trying to develop and launch three-layer composite membranes.
Industrial milling is one of the most commonly used techniques in the manufacturing industry and can be divided into two categories: wet milling and dry milling. To understand the difference between the two, and the challenges that come along the milling process, we first need to gain an understanding of the basics.
The use of mechanical energy to break down particles through various mechanical forces including grinding media, pegs, rods, pebbles, and screens. When the material is pumped through the mill, the mill&#;s components act on the solids in the mixture to tear them apart or crush them, further reducing them in size. The industrial milling process helps to maximize the yield of the mix&#;s ingredients and can improve the resulting product&#;s functionality as well. For example, milling can help improve color development, film properties, and product flow in inks and paints.
Now that we have a basic understanding of the industrial milling process, let&#;s examine the difference between wet milling and dry milling. Dry milling typically uses particle-on-particle contact to reduce materials&#; size, while wet milling involves dispersing the material in a liquid and using solid, grinding elements to reduce size. Products can be broken down through either one of these processes, but wet milling, which we&#;ll discuss first, tends to be a more intensive process than dry milling. Wet milling, also known as wet grinding, is a process through which particles that are suspended in a liquid slurry are dispersed in that liquid by shearing or crushing. Once the milling process is complete, these particles are ready for use or can be dried and separated for incorporation into additional products. Wet milling is more complex than dry milling, thanks to the addition of a liquid, but this process also has the power to reduce a product into finer particles. This allows for the production of a greater variety of byproducts and also can result in improved physical properties in your final product. By contrast, dry milling utilizes no liquid element, and is most frequently used for the particle size reduction of dry materials like powders and granules, or de-agglomerating and de-lumping bulk materials. While dry milling is a less intensive process, which often makes it the first method considered, wet milling is the best and most efficient way to get to your preferred particle size if extremely small particles are your goal.
Depending on the type of materials you&#;re working with, different industrial milling jobs come with their own unique challenges. When working with smaller (or older) milling units, the time and labor required to work in batches can be problematic and lead to unnecessary waste of materials and time. This leaves manufacturers faced with the growing challenge of producing smaller and smaller particles in an efficient and cost effective manner. For instance, as nanoparticles continue to become more and more common in the development of new products, using the correct equipment for this manufacturing process is crucial if businesses want to maintain a leading edge over their competitors. Finally, although wet milling and dry milling are unique processes, one challenge that they have in common is the potential wear and tear on the grinding equipment that&#;s used to break down the material. In dry milling, abrasives within the materials themselves could damage the milling equipment over time, while in wet milling, the carrier fluid used in the process, or the material itself, can potentially eat away at portions of the equipment.
There are many types of mills in the market for both wet and dry milling, and the selection process can be daunting, but with the right equipment to meet your industrial milling needs, you can cost-effectively create uniformly fine particles with little to no contamination. When choosing a mill to fit your business needs, it&#;s important to find the equipment that maximizes efficiency and performance, and you need to know how the equipment will perform for your product. There are many factors to consider, and material loss can be a big one as it&#;s part of your overall manufacturing costs. The lower your costs, the better your bottom line looks. Here at Hockmeyer, our line of innovative, state-of-the-art wet milling equipment will help you get the job done, no matter what your desired end result is. Key players in our line of industrial milling equipment include:
Looking for additional insight to help decide which mill is right for you, or ready to learn more about industrial milling solutions from Hockmeyer? Contact us for more information about our products and how they can best serve you and your business needs.
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