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Each lithium electricity industry personnel have to consider lithium ion battery performance, and longer cycle life means less resource consumption. So what exactly what determines the performance of lithium ion battery cycle there?
Material: the choice of materials is the first factor influence the properties of lithium ion batteries. Chose the cycle performance of poor material, process made more perfect, more reasonable, the cycle of batteries must also cannot guarantee; Chose the better materials, made some problems, even if the subsequent cycle performance may also can't bad too far (a cobalt acid lithium g play around just 135.5 mAh/g and formation of lithium batteries, 1 C hundred times while diving, but 0.5 C, more than 90% of the 500 times; a batteries apart after the cathode with a black batteries, graphite particles cycle performance is normal). From the Angle of material, a whole battery of cycle performance, is by the positive electrode and the electrolyte circulation performance after the match, the cathode and the electrolyte cycle after the matching performance of the two, with poor person. Material cycle performance is poorer, on the one hand, is likely to be in circulation in the process of crystal structure change too fast to continue to complete the intercalated-li lithium, on the one hand may be due to the active substance and its corresponding electrolyte can't generate dense and uniform SEI film active material and electrolyte premature side reaction and make the electrolyte excessive consumption will affect cycle. In designing batteries, if a very confirm choose cycle performance with poor material, other do not need to choose cycle performance good material, waste.
Compaction is negative: negative compaction is too high, although can improve the energy density of batteries, but also a certain extent, reduce the material cycle performance. According to the analysis of theory of compaction, the greater the equivalent of the greater the damage to the structure of the material, and the structure of the material is to guarantee the foundation of the lithium ion battery can be recycled, In addition, the anode compaction is high batteries are difficult to ensure higher fluid volume, and protect liquid quantity is to complete a normal cell cycle or the basis of more circulation.
Water: too much water will with the cathode active material adverse events, and destroying the structure, in turn, affect the circulation, too much water also not conducive to the formation of the SEI film. But in difficult to remove traces of moisture at the same time, the trace amounts of water can also be a certain extent to ensure the performance of the batteries. Unfortunately wenwu to this vital experience is almost zero, could not say too much. You are interested can search the BBS inside information about the topic, or a lot.
Coating film density: single variable considering membrane density on the influence of the cycle is an almost impossible task. Membrane density inconsistent or bring capacity differences, is either batteries winding or laminated layer of the difference. For the same as material of batteries with capacity with lower density was equivalent to add a layer or multilayer winding or laminated layers, the corresponding increase of diaphragm can absorb more electrolyte in order to keep the cycle. Considering more thin film density can increase rate performance of the batteries, the pole piece and naked batteries baked in addition to the water will be easier, too, of course, when the density of thin film coating of error may be more difficult to control, active substances in the larger particles may also cause negative effect to coating, rolling, more layer means more foil and diaphragm, which means higher costs and lower energy density. Therefore, assessment also need balance considerations.
Negative: excessive negative excess reason except for the first time to consider the influence of the reversible capacity and the density of coating film deviation, the impact on the cycle performance is also a consideration. For cobalt acid lithium and graphite system, negative electrode graphite into circulation in the process of the "short board" is common. If negative excessive insufficient, lithium batteries may before the cycle is not analysis, but the positive structure change little circulation after hundreds of times but the cathode structure is destroyed and cannot receive the positive provide lithium, lithium ion to analyse cause premature capacity decline.
Enough amount of electrolyte, electrolyte influence on the cycle there are three main reasons, one is the insufficient amount of filler, 2 it is though liquid injection amount but aging time enough or is negative because of the high compaction immersion is not sufficient, 3 it is inside the loop batteries electrolyte was consumed. Insufficient fluid injection rate and liquid volume wenwu written before the lack of electrolyte effect the performance of the batteries and therefore no longer here. Across the electrodes to the third point, especially in the cathode and the electrolyte of the matching of microscopic characterized by dense and stable SEI formation, and in his right eye visible performance, both for the circulation of electrolyte in the process of consumption. Incomplete SEI film on the one hand, can not effectively prevent the cathode and the electrolyte are consumed by the side effects of electrolyte, on the one hand, on the SEI film for the defective parts will be as the cycle to regenerate the SEI film to consume the reversible lithium source and electrolyte. Whether the batteries of recycle hundreds or even thousands of times or for dozens of times both diving batteries, if cycle before the electrolyte electrolyte has consumed after adequate but cycle, increase electrolyte ownership is likely to a certain extent, to improve the cycle performance.
Objective conditions of the test: the test in the process of charging and discharging rate, cut-off voltage, charge cut-off current, in the test charge and test room temperature, all of a sudden interruption in the process of testing, test points and outside factors, such as batteries, contact resistance will be more or less affect the cycle performance test result. In addition, the sensitive degree of different material to the objective factors each are not identical, unified test standard and knowledge of common and important characteristics of materials should be enough for routine use.
Conclusion: like bucket principle, many of the factors affecting the performance of cell cycle, the final decisive factor, is the shortest board of a number of factors. At the same time, between these influencing factors, also have interactive effects. Under the same material and made into ability, the higher the cycle, often means that the lower energy density, find combination point between just to meet customer demand, to ensure consistency of batteries made from as far as possible, is the most important task.
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