How does the diaphragm, positive and negative poles and other factors of lithium-ion batteries affect their cycle life?

There are many factors that affect the cycle life of lithium ion batteries, but the underlying reason is that the number of lithium ions involved in energy transfer is constantly decreasing. It should be noted that the total number of lithium elements in the battery has not decreased, but there are fewer "activated" lithium ions. They are trapped in other places or the channels of activity are blocked and can not freely participate in the process of circular charging and discharging.

1, isolation film blocked or damaged

The role of the isolation membrane is to separate the positive and negative poles of the battery to prevent short circuits. In the process of lithium ion battery cycle, the separation membrane drying up and failure is an important reason for the early deterioration of battery performance. This is mainly due to the lack of electrochemical stability and mechanical properties of the isolation film itself, and the infiltration of the electrolyte to the isolation film during repeated charging process. Due to the drying up of the isolation membrane, the ohmic resistance of the battery increases, resulting in congestion of the charging and discharging channel, incomplete charging and discharging, and the battery capacity can not return to the initial state, greatly reducing the battery capacity and service life.

2, positive and negative material fall off

The positive and negative active substances are fixed to the matrix by binders. During the long-term use process, due to the failure of binders and the mechanical vibration of the battery, the positive and negative active substances continue to fall off and enter the electrolyte solution. This leads to the continuous reduction of active substances that can participate in electrochemical reactions and the continuous reduction of battery cycle life.

The long-term stability of the binder and the good mechanical properties of the battery will slow down the decline of the battery cycle life.

3, external use factors

Lithium-ion batteries have reasonable conditions and range of use, such as charging and discharging off voltage, charging and discharging ratio, operating temperature range, storage temperature range, etc.. However, in actual use, abuse beyond the allowed range is very common. Long-term unreasonable use will lead to irreversible chemical reactions within the battery, causing damage to the battery mechanism, accelerating the aging of the battery, and causing a rapid decline in the cycle life., severe, There are also safety incidents.

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