Kangli Electronics explains the charging process

During the charging process, lithium ions are released from the lattice of the positive electrode active material, enter the metallic lithium at the negative electrode through the organic electrolyte and the separator, and at the same time, electrons are transmitted from the external circuit to the negative electrode to achieve charge balance, and the positive electrode is in a high-potential lithium-poor state; the discharge process is the opposite, the metallic lithium is converted into lithium ions, and enters the lattice of the positive electrode active material through the organic electrolyte and the separator, and at the same time, electrons are transmitted from the external circuit to the positive electrode.

However, during the charging process, due to the uneven surface of the metal lithium electrode, the difference in electrodeposition rate causes uneven deposition, resulting in the formation of dendritic lithium crystals at the negative electrode. When the dendrites grow to a certain extent, they will break, producing "dead lithium", causing irreversible lithium and reducing the actual charging and discharging capacity of the battery. Lithium dendrites may also pierce the diaphragm, connecting the positive and negative electrodes, causing an internal short circuit in the battery. The large amount of heat generated by the short circuit can cause the battery to catch fire or even explode.

It is precisely because of the "lithium dendrite" problem during the cycle that the battery life is short and the safety performance is poor, which has caused the research of lithium metal secondary batteries to stagnate in history. In recent years, with the development of related technologies and the urgent need for high energy density lithium secondary batteries, new lithium metal secondary batteries such as lithium-sulfur and lithium-air have emerged, making the research of lithium metal secondary batteries once again a hot topic.