hy deep discharge would hurt to li ion battery?

- Sep 23, 2018 -

Do you know why deep discharge would hurt to lithium ion battery ?

Analysis of the impact of lithium. We know that if the lithium ion dissolved in the electrolyte is reduced to metallic lithium on the surface of the anode active material, notice that this is on the surface, and this reaction is not normally embedded in the lattice structure of the anode active material. This phenomenon can be formed when the negative electrode potential falls below the standard potential of Li / Li +. Then some lithium reacts with electrolytes to form irreversibly insoluble by-products, which in turn leads to negative SEI growth and even dendrite formation. The by-products can also be filled into the pores of active materials and diaphragms and isolated from certain electrode regions, making them inactive.

In the higher SoC, the specific voltage platform of the battery can identify excessive lithium plating as shown below. This process can be observed during the charging process and disappears again during subsequent standing time or battery discharge. A small amount of lithium precipitation can be detected by calorimetry or high precision measurement of Kulun efficiency.

Although lithium deposition disappears during the rest of the charging process and is embedded in the negative electrode, part of the deposited lithium reacts with the electrolyte. The reaction of lithium and electrolyte will consume lithium and further reduce the battery capacity. Because of the low equilibrium potential of graphite, especially at high SoC, this lithium precipitation plating is easy to occur on the surface of graphite. With the increase of SoC, the increase of charge current and the decrease of temperature will increase lithium plating. In addition, thick electrodes with large particles and low porosity are more likely to deposit lithium than thin electrodes with small particles and high porosity. In general, lithium metal plating can be considered as a side effect during charging, which necessarily leads to the consumption of recyclable lithium and consequently leads to capacity degradation.

not all lithium ion batteries have deep discharge capability, otherwise, it would probably destroy battery at one time. if you need any deep cycle lithium ion batteries, it's higher recommend to negotiated with engineer.