The importance of the cycle performance of lithium ion battery needless to say, in terms of macroscopic, longer cycle life means less resource consumption, therefore, the influence factors of lithium ion battery cycle, is each lithium electricity industry related personnel have to consider the problem.
According to the analysis of scientific research personnel, and influence the properties of the lithium battery has the following seven factors:
1, the moisture in the lithium battery manufacturing process
Too much moisture and 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.
2, the battery is negative compaction density
Anode compaction is too high, although can improve the energy density of batteries, but also a certain extent, reduce the circulation of the material performance, from the theory to analysis, the 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.
3, lithium battery test in the objective conditions
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 system performance test results, 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.
4 excessive, lithium battery cathode
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 graphite into circulation in the process of "short board" side is relatively 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.
5, the density of the coating film
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 layer, corresponding to the increase of the diaphragm can absorb more electrolyte in order to keep the loop, considering the thinner film density can increase the ratio of cell performance, 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, so the evaluation also need to balance considerations.
6, choose the kind of lithium battery raw materials used
The choice of materials is the first factor influence the properties of lithium ion battery, chose the cycle performance of poor material, process made more perfect, more reasonable, the cycle of batteries must also cannot guarantee; Chose the better material, even if later made into a little problem, cycle performance may also can‘t bad too far, from the Angle of material, a whole battery of cycle performance, is from the anode and electrolyte circulation performance after the match, the cathode and electrolyte circulation after the matching performance of the two, poor person to decide, the cycle of material performance is poor, 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.
7, the amount of electrolyte
Insufficient amount of electrolyte influence on the cycle there are three main reasons, one is the insufficient amount of filler, 2 it is though filled fluid 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. Third, the matching of positive negative especially in the cathode and the electrolyte micro 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 rate, 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.
