Basic principle of lithium battery analysis: discharging mechanism

1. Describe lithium battery and its working principle

    Since its appearance in 1990, lithium ion battery has been rapidly developed due to its excellent performance and widely used in society.Lithium-ion batteries are rapidly gaining ground in many fields, such as mobile phones, laptops, small video cameras and so on.

    Currently, the accepted basic principle of lithium battery is the so-called "rocking chair theory".The charge and discharge of lithium battery is not through the traditional way to achieve the electron transfer, but through the lithium ions in and out of the thick material crystal to change the energy.Under normal charging and discharging conditions, the entry and departure of lithium ions will only cause the change of layer spacing, but will not cause the destruction of crystal structure. Therefore, from the charge and discharge reflection, lithium ion battery is an ideal reversible battery.When the charge and discharge of lithium ion in the battery positive and negative pole back and forth, just like a rocking chair in the positive and negative pole to shake, so some people will be called the image of lithium ion battery rocking chair battery.

     We often talk about the advantages of lithium ion battery is the traditional nickel-cadmium battery (Ni/Cd) and nickel-hydrogen battery (Ni/MH).It has the advantages of high specific voltage, long cycle life, low self-discharge rate and no memory effect.

Lithium battery discharge, for the battery, normal use is the discharge process.

Lithium battery discharge only need to pay attention to a few points:

1. The discharge current shouldn’t be too large, which may cause heat inside the battery and cause permanent damage.

2. Must be not over-discharge! Lithium batteries are most afraid of over-discharge, once the discharge voltage is lower than 2.7v, it may lead to battery scrap.

The following is the typical discharge curve of general lithium battery:

It can be seen from the typical discharge curve that the larger of discharge current, the smaller of discharge capacity and the faster of voltage drop.

Therefore, under normal circumstances, the battery heavy load work, reduce the load will appear voltage recovery, is the so-called "recovery" phenomenon.

As shown in the figure below, the discharge curve stops for a while during discharge and "recovery" appears.