Several Factors Affect The Performance of Lithium-ion Battery Cycle
Author: Source: Datetime: 2016-10-12 17:13:19
Material Type: choice of materials is the first element of the impact of lithium-ion battery performance. Lifepo4 batteries is also belongs to lithium batteries. Loop is selected, the poor performance of the material, and then the process is reasonable, then made perfect cycle batteries are bound not guarantee; choose good material, even if the follow-up made a slight problem, the cycle of poor performance may not too outrageous (one gram of lithium cobalt oxide plays only about 135.5mAh / g and analysis of lithium batteries, 1C although over a hundred times diving but 0.5C, 500 times more than 90%; there are negative after an open black graphite particles batteries batteries, normal cycle performance). From the material point of view, a full-cycle performance of the battery, the cycle performance is matched with the electrolyte of the positive electrode, negative electrode and electrolyte solution cycle characteristics after matching the two, one poorly determined. Cycling performance is poor, one hand may be in circulation during the crystal structure changes too quickly and thus unable to finish off the lithium as lithium, on the one hand may be due to the active substance can not be generated with a corresponding electrolyte membrane caused by dense, homogeneous SEI active substance a side reaction with the electrolyte premature leaving excessive consumption thereby affecting electrolyte circulation. In designing batteries, if the selection is poor cycle performance of a material of Claim pole, the other electrode is preferably selected cycle performance without material waste.
Compaction positive and negative: positive and negative compaction too, although they could improve the energy density of batteries, but also reduce cycle properties of the material to a certain extent. From theory to analyze, the greater the compaction, the equivalent of the greater structural damage to the material, and the structure of the material is the basis for the lithium-ion battery can be recycled; in addition, positive and negative high compaction relatively difficult to ensure batteries high liquid retention volume, while the fluid retention volume is complete the normal cycle batteries or more cyclic basis.
Moisture: Excessive moisture and the positive electrode active material side reactions, destroying its structure thereby affecting circulation, too much water is not conducive to the formation of SEI film. But at the same time difficult to remove trace amounts of moisture, trace amounts of water can also be to some extent to ensure the performance of batteries. Unfortunately, civil and military personal experience in this regard is almost zero, can not say too many things. We are interested can search a search forum inside information on this topic, quite a few.
Coating film density: consider the impact the film density on a single variable cycle is almost an impossible task. Film density inconsistencies or differences in the capacity to bring either lifepo4 battery pack or winding difference laminate layers. The same model with the same capacity in terms of materials, batteries, reducing the film density equivalent to adding one or more layers are wound or laminated layers, corresponding to an increase of the membrane can absorb more electrolyte to ensure circulation. Taking into account the thinner film density can increase the rate performance batteries, batteries pole piece and bare except baking water will be easier, of course, the film density error when the coating is too thin may be more difficult to control, the active substance large particles may also be coated, rolling a negative impact, more layers mean more foil and a separator, in turn means higher costs and lower energy density. Therefore, when evaluating the need to balance considerations.
Negative excess: excess negative because in addition to the need to consider first irreversible capacity outside influence and coating film density deviation, the impact on cycle performance is also a consideration. For lithium cobalt plus graphite system, the graphite anode during cycling become "short board" one of the more common. If the negative excess is not sufficient, the batteries may not be before the loop analysis lithium, cycle hundreds of times but after the positive structural changes little but negative electrode structure is seriously damaged and can not be fully received positive electrode thereby providing lithium-ion analysis lithium, resulting in over-capacity early fall.
The amount of electrolyte: the electrolyte amount is less impact on the cycle there are three main reasons, first, insufficient amount of liquid injection, liquid injection Second, although sufficient amount of aging but the lack of time or high positive and negative immersion by compaction and other causes not full, three cycles with the batteries inside the electrolyte is consumed. NOTE insufficient fluid volume and wrote, "Lack of electrolyte on the performance of batteries" before civil and military security was inadequate amount thus not repeat them, the battery is usually can be used in portable soalr power generator. On the third point, in particular, the positive and negative of the negative electrode and electrolyte solution matching the performance of micro-dense and stable SEI is formed, and the right-eye visible performance, both for the process of the electrolyte circulation rate of consumption. Incomplete SEI film on the one hand can not effectively prevent the negative electrode and the electrolyte side reactions which consume the electrolyte, on the one hand in the SEI film defective parts will circulate along with the re-generation of SEI and thus reversible lithium source and electrolyte depletion . Whether circulating hundreds or even thousands of times the batteries or for the dozens of diving both batteries, if sufficient electrolyte circulation before and after electrolyte circulation has been consumed, the amount is likely to increase the electrolyte can retain a certain improve their cycling performance degree.
The objective conditions of the test: the test during charge and discharge rate, cutoff voltage, charge cut-off current, test overcharge and over discharge, test room temperature during the test of a sudden interruption, test points and batteries and other external contact resistance factors that are more or less affect the cycle performance test results. In addition, different materials sensitive to the above objective factors vary, uniform testing standards and common understanding of the characteristics and key materials should be sufficient daily use.
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