With the development of science and technology, lithium battery applications are more and more widely. After several cycles of charge and discharge, the battery capacity performance will decline. The process of lithium battery charge and discharge cycle is a complex physical and chemical reaction process. There are many factors influence cycle life, on the one hand it related to the the characteristics of battery itself, such as design, manufacturing process and material degradation, etc, on the other hand it relate to the environmental factors of battery using, such as the environment of using, charge and discharge conditions. Next, we’ll analysis the following factors that affect the cycle life of lithium battery.

 

1.Design and manufacturing processes

(1). Moisture

Excessive moisture will appear with side effects with active material of positive and negative, destroying the structure and then influencing de circulation. In addition, it is not conducive to the formation of SEL film, but when the trace of moisture is difficult to remove, trace of water may also ensure the performance of the battery in a certain extent.

(2). Positive and negative compaction

If the positive and negative compaction is too high, it can reduce cycle performance of the material to a certain extent though it can improve the energy density. From theory to analyze, compaction is greater, its damage to the structure of material is greater. The structure of the material is the basis for ensuring the lithium-ion battery can be recycled. In addition, high compaction of positive and negative is hard to ensure the high preserving fluid volume. Preserving fluid volume is the basis of cell to cycle normal or more cycle times.

(3). Excessive negative

As for lithium cobalt oxide added graphite system, graphite cathode becomes “short board” which is a common situation in the process of circulation. If excessive negative is not sufficient, the cell may not analyze the lithium before cycle. But after hundreds of times cycle, the structure of positive changes little and the structure of negative is destroyed seriously and can’t fully receive lithium-ion provided by positive to analyze the lithium which cause prematurely decline of capacity.

(4).  Coating film density

Membrane density can bring capacity difference or battery winding or lamination layers difference. For the same as material with capacity with batteries, reducing the membrane density is equivalent to add a layer or multilayer winding or laminated layer. Corresponding to the increase in the diaphragm can absorb more electrolytes in order to keep the cycle. In addition, thinner film density can increase the rate performance of cells and the baking out of the water of pole piece and naked cells will be easier. Of course, the error of too thin coating film density may be harder to control. The large particles of the active substance may have a negative effect on the coating and rolling. Furthermore, more layers mean more foil and diaphragm, which means higher costs and lower energy density. Therefore, we need to do the balancing consideration when assessing.

(5).  Material category

Selecting material is the most important factor influencing the performance of lithium-ion battery. From the point of materials, there are two kinds of cycle performance. One is the cycle performance after matching anode and electrolyte, and another is the cycle performance after matching cathode and electrolyte. The cycle performance of the whole battery depends on the poorer one between these two kinds of cycle performance. The cycle performance of materials is poor. There are maybe two reasons. On the one hand, crystal structure changes too fast to continue to finish inserting and dropping in the cycle process. On the other hand, active materials and its corresponding electrolyte can’t produce dense and homogeneous SEI film, leading to the active materials and corresponding electrolyte generate side reaction too early, because of that, electrolyte consumes too fast influencing cycle. In the process of designing cell, if one pole certainly selects the material with poor cycle performance, another pole needn’t to select material with good cycle performance, because of wasting

(1). Temperature environment

The temperature environment is too low or too high will affect the cycle life of lithium battery. 

The discharge capacity of lithium battery will be reduce at low temperature environment. Because of Li-ion is easier to disengage from the negative pole, and more difficult to embed at low temperature, When charging, lithium metal will appear and react with the electrolyte to form a new SEI film covering the original SEI film, so that the battery impedance increases, resulting in battery capacity decline. Lithium battery charge and discharge cycle is unstable at high temperature, high temperature lead to the electrode electrochemical polarization intensifies and gas generation, resulting in bulging phenomenon, while the charge transmission resistance increases, ion transport kinetics to reduce.

(2). Transport Process

Equipment that uses lithium-ion batteries may experience the test such as vibration, shock, impact, etc. when transported or under normal operation. Some lithium batteries charge and discharge with the system communication and receive data according to a certain frequency. The vibration frequency of equipment may cause interference to the battery, which may cause the chip data to be faulty or cause protection circuit action. Strong vibration or shock, The pole of the battery, the external wiring, terminals, tabs may be broken or off, he active material on the pole of battery may also peel off, which will affect the battery cycle life and even dangerous

Lithium battery using is the process of charge and discharge cycle, charge and discharge current,  cut-off voltage and the methods of charge and discharge are influence battery cycle life.  Blindly increase battery current and charge cut-off voltage, reduce the discharge cut-off voltage will make the battery performance down.