Analysis of the characteristics and development of ceramic coated diaphragms

by:CTECHi     2021-08-29
In today's highly developed science and technology, a variety of high-tech appears in our lives, bringing convenience to our lives, so do you know that these high-tech lithium-ion battery ceramic-coated separators may contain? The important purpose of the lithium ion battery is to separate the positive and negative electrodes of the lithium ion battery to prevent the two poles from contacting and short-circuit, and also has the function of allowing electrolyte ions to pass through. The performance of the diaphragm determines the interface structure and internal resistance of the battery, and directly affects the battery's capacity, cycle, and safety performance. The performance of the diaphragm determines the internal resistance and interface structure of the lithium-ion battery, which in turn determines the battery capacity, safety performance, charge-discharge density and cycle performance. Ceramic-coated special diaphragm: Take pp, pE or multi-layer composite diaphragm as the substrate, and the surface is coated with a layer of nano-aluminum oxide material, which is treated by a special process and adheres tightly to the substrate. Significantly improve the high temperature resistance and safety of lithium-ion batteries. The method of continuing to increase the energy of lithium-ion batteries is achieved through structural design and integration technology, but this will cause the problem of reduced mechanical strength of the diaphragm, which is likely to cause thermal runaway and reduce the safety of the battery. Ceramic diaphragms are used to improve safety and create a safety core. Coating ceramic diaphragm nanoparticles on the diaphragm can increase the strength of the diaphragm. High-safety functional lithium-ion battery ceramic-coated separators against the trend, lithium-ion batteries have become the mainstream of energy storage devices on the market. As the 'third electrode' separator is an important part of lithium-ion batteries. The important purpose of the separator is to separate the positive and negative electrodes of the battery to prevent contact between the two poles and short-circuit. In addition, it also has the function of allowing electrolyte ions to pass through. The performance of the diaphragm determines the interface structure and internal resistance of the battery, and directly affects the capacity, cycle and safety performance of the battery. The traditional diaphragm material uses polyolefin, which has stable chemical properties and strong mechanical properties, and is easy to produce on a large scale. However, its low thermal stability and insufficient affinity for electrolytes limit its long-term development. Facing the large-scale application of ternary materials in power lithium-ion batteries, the energy density of lithium-ion batteries continues to increase, and safety issues are becoming more and more important. The new technology of coating ultrafine alumina powder on the surface of the traditional organic membrane is booming. The ceramic coating diaphragm was further modified by the use of bionic material-polydopamine, and a diaphragm material with high safety was designed and developed. Using the auto-oxidative polymerization of dopamine, after immersing the ceramic-coated diaphragm in the dopamine solution overnight, polydopamine forms a continuous and complete film-forming coating on the ceramic coating and the polyolefin base film, thereby forming the ceramic layer and the base film overall. Ceramic-coated separator has the following advantages: 1. It can improve the thermal stability of the lithium ion battery separator, improve its mechanical strength, and prevent large-area contact between the positive and negative electrodes caused by the shrinkage of the separator; 2. It can improve its puncture resistance It can prevent the short circuit caused by the long-term cycling lithium dendrites of the battery piercing the separator, and can neutralize a small amount of HF in the electrolyte to prevent the battery from swelling; 3. The porosity of the ceramic coating is greater than that of the separator, which It is beneficial to enhance the liquid retention and wettability of the separator, thereby prolonging the cycle life of the battery. Ceramic coating technology has become the choice for high-safety and high-performance diaphragms. From the perspective of characteristic requirements, in order to prevent polyethylene from cracking under higher working voltage, the use of outer layer pp, ceramic coating or high temperature outer layer is a safer choice. To obtain a longer cycle life, high-rate charging and discharging and braking recharging, appropriate pore size, lower tortuosity and higher air permeability are the factors that should be considered for the diaphragm; in order to improve safety and service life, The diaphragm should meet the conditions of cut-off function, prevention of thermal explosion and dimensional stability. According to the national industrial policy, high requirements are put forward for increasing the energy ratio of lithium-ion batteries. However, for a long time, there has been a scientific problem with lithium-ion batteries, that is, the higher the energy density, the lower the safety. The emergence of nano-ceramic diaphragm technology has broken this curse and created a 'safe core' to enable lithium-ion batteries. The battery is not afraid of thorns, not afraid of falling, and not falling. In this critical period when it is urgent to break through the bottleneck of existing technologies, it will undoubtedly inject power into the entire power lithium-ion battery industry. Ceramic coating is a systematic project, involving base film selection, high-precision coating equipment, ceramic particle selection, process parameter control and battery system research. Only through strict verification and testing can the ideal coating effect be guaranteed. The above is some detailed analysis of the ceramic-coated separators for lithium-ion batteries that are worth learning. I hope that I can give you some help when you are just getting in touch. If you have any questions, you can also discuss with the editor.
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