Lithium dendrites

- Sep 03, 2018-

Metal lithium can be used as a negative electrode for lithium secondary batteries, and its specific capacity is as high as 3862 mAh/g. However, it has been found that in repeated charge and discharge processes, lithium ions are repeatedly removed and deposited on the negative electrode, and the surface of metallic lithium is easy. Lithium dendrites are grown.

Lithium dendrite refers to a dendritic lithium metal formed by lithium ion reduction during charging of a lithium battery using a liquid electrolyte.

Metal lithium is not used as the negative electrode active material because metal lithium crystallizes on the negative electrode to form dendritic metallic lithium, "dendritic lithium". When “dendritic lithium” grows to a certain extent, it will pierce the separator which is electrically insulated between the positive and negative electrodes, and finally touches the positive electrode, causing internal short circuit of the battery, which seriously threatens personal safety. Please discuss any feasible ways to overcome the growth of lithium dendrites?

1. Adding an additive that inhibits dendrite growth to the electrolyte.

2. Anode modification of lithium metal. If lithium alloy is used as the anode, there are Li-Ai-Ni ternary alloys, Li-Sn alloys, etc. The disadvantages of this method are low cycle efficiency, large voltage platform hysteresis, expansion and pulverization of electrodes in circulation. There is no fundamental solution, or the surface of the lithium metal electrode is coated with Li2CO3 to improve the performance of the electrode.

3. Surface treatment of the diaphragm. This method is relatively simple, as long as the surface facing the lithium metal anode side is properly treated and modified, the key is to find a surface group capable of inhibiting dendrite formation. For example, a sulfonate group or the like is grafted on the surface of the separator.

4. Use bidirectional pulse charging instead of DC charging.