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Several factors affect the lithium ion battery cycle

Author:Source:Datetime: 2016-03-14

The cycle goes without saying that the degree of importance of the performance of lithium-ion batteries; another macro terms, longer cycle life means less consumption of resources. Thus, the factors affecting the cycle performance of lithium-ion batteries, each associated with lithium industry personnel have to consider the problem. Here are several factors that may affect battery cycle performance for reference.
       
Type of material: the choice of materials is the first factor to affect the performance of lithium-ion battery. Selected poor cycling performance materials, the process is again reasonable, made for further improvement, the cycle batteries certainly can not be guaranteed; choose better materials, even if follow-up is made slightly cycling performance may not be bad too far off the mark (one play only about 135.5mAh / g and the analysis of lithium batteries, lithium cobalt oxide grams 1C hundred times diving but 0.5C, more than 500 times 90%; once batteries apart negative black graphite particles the batteries, the cycle performance of normal). From the material point of view, a full cycle of the battery performance, is provided by the cycle performance matched the positive electrode and the electrolyte, the cycle performance in the negative electrode with the electrolyte after the match both poor one decision. The cycle performance of the material is poor, on the one hand may be a rapid changes in the crystal structure, during the cycle is thus unable to continue completion of the lithium intercalation delithiated hand may be caused due to the active substance and the corresponding electrolyte SEI film is unable to generate a dense, homogeneous active substance The occurrence of side reactions with the electrolyte prematurely leaving the electrolyte excessive consumption thereby affecting the circulation. The design of the batteries, if an electrode material confirm the poor performance of the chosen cycle, the other pole without selecting a better performance of the loop material waste. Positive and negative compaction: positive and negative excessive compaction, although the energy density of the batteries can be improved, but also to some extent reduce the cycle performance of the material. From a theoretical analysis, compaction greater the equivalent of the material the greater the structural damage, and the structure of the material is to ensure that the lithium-ion battery can be recycled basis; addition, positive and negative compacted higher electric core is difficult to guarantee than The high amount of liquid retention, and to maintain the liquid volume is the basis of the normal cycle, or more times the cycle batteries.
       
Moisture: Excessive moisture will be positive and negative active substances side effects, the destruction of its structure thereby affecting circulation, at the same time, too much water is not conducive to the formation of the SEI film. However, while a trace amount of water is difficult to remove, the traces of water can also to a certain extent to ensure the performance of the batteries. Unfortunately, the civil and military personal experience in this regard is almost zero, and can not say too many things.We are interested in a search forum inside information on this topic can be found, or a lot.
       
Coated film density: single the variable considerations film density of cycle is almost an impossible task. Inconsistent film density either bring the difference in capacity, either batteries wound or laminated layers of difference. Lower film density batteries of the same material of the same model and capacity, representing an increase of one or more layers of wound or laminated layers, the corresponding increase in the diaphragm can absorb more of the electrolyte in order to ensure the circulation. Consideration to the thinner film density can be increased rate performance of the batteries, the pole pieces and the bare core baking water will also be easier, of course, an error when applying thin film density may be harder to control, the active substance the large particles may also be interested in a negative impact on coating, roll, more layers means that more of the foil material and the diaphragm in turn means that the higher cost and lower energy density. So, assess the need for a balanced consideration.
       
Negative electrode excess: the negative electrode excess of reasons in addition to the need to consider the initial irreversible capacity density deviation of the impact and the coating film outside, the impact on the cycle performance is also a consideration. Negative graphite for lithium cobalt oxide plus graphite system become more common "short board" in the party in the cycle. If negative excess is not sufficient, not analyze lithium batteries may be in circulation before the cycle but hundreds of times after the positive structural changes little negative structure was severely damaged not receive positive provided lithium ion analysis of lithium thereby, resulting in capacity over early decline.
       
The electrolyte volume: insufficient amount of electrolyte cycle impact, there are three main reasons, First, the amount of liquid injection, pour sufficient aging time is not enough, or caused due to the compaction and high positive and negative immersion not fully With the cycle batteries internal electrolyte exhaust. Note fluid volume and the amount of liquid retaining wrote "electrolyte Wenwu before the lack of impact on the performance of the batteries and therefore will not go into. The third point, positive and negative, especially negative microscopic performance match with the electrolyte is a dense and stable SEI formed, while the right eye visible performance, both for the recycling process, the consuming speed of the electrolyte.Incomplete SEI film on the one hand can not effectively prevent the negative side effects with electrolyte to consume the electrolyte, the one hand, the defective parts in the SEI film with the conduct of the cycle to regenerate the SEI film thus consume the reversible lithium source and electrolyte Whether cycle after cycle of hundreds or even thousands of times the batteries or batteries for dozens of both diving before, if the cycle electrolyte sufficient electrolyte exhaust, is likely to increase electrolyte ownership can necessarily extent, improve the performance of its cycle.

The objective conditions of the test: test the process of charge-discharge rate, cut-off voltage, the charging cut-off current test overcharge and over discharge, a sudden interruption in the test room temperature, the testing process, the test points of contact with the internal resistance of the batteries outside factors will more or less affect the cycle performance test results. In addition, the degree of sensitivity of the different materials of the objective factors of the same unified testing standards and understanding of the common and important properties of the materials should be sufficient day-to-day use.

Summary: the same principle as casks, many factors which affect battery cycle performance, the ultimate decisive factor, many factors shortest board. Between these factors have a reciprocal influence. The same material and made the higher cycle often means lower energy density, to find exactly meet customer demand integration point, as far as possible to ensure the consistency of batteries made, the party is the most important task .