Source: Lithium Battery Alliance Chairman Author/Zhu Liang etc.
In order to solve this problem, people have studied prelithiation technology. The electrode material is recharged with lithium through prelithiation to offset the irreversible lithium loss caused by the formation of the SEI film, so as to increase the total capacity and energy density of the battery.
The common pre-lithiation method of anode lithium supplement technology is anode lithium supplement, such as lithium foil supplement lithium, lithium powder lithium supplement, etc., which are currently the key development pre-lithiation processes.
Pre-lithiation with lithium foil is a technology that uses self-discharge mechanism to supplement lithium. The potential of metallic lithium is the lowest among all electrode materials. Due to the existence of the potential difference, when the anode material contacts the metallic lithium foil, electrons spontaneously move to the anode, accompanied by the intercalation of Li+ in the anode.
The electrolyte is dropped on the silicon nanowire anode grown on the stainless steel substrate, and then it is directly contacted with the lithium metal foil to supplement lithium. A half-cell test was performed on the anode after replenishing lithium, and it was found that the open circuit voltage of unreplenished lithium was 1.55V, and the specific capacity of lithium intercalation for the first 0.1C discharge at 0.01～1.00V was 3800mAh/g; the silicon nanowires after replenishing lithium were open circuit The voltage is 0.25V, and the specific capacity for lithium insertion for the first time is 1600mAh/g.
The tin-carbon anode is directly contacted with the lithium foil soaked in the electrolyte for 180 minutes to supplement lithium. With a half-cell test, the irreversible specific capacity of tin-carbon is reduced from 680mAh/g to 65mAh/g after replenishing lithium. The anode constitutes a full battery. The ICE tested at a rate of 1.0C at 3.1 to 4.8V is close to 100%, and the cycle is stable, and the rate performance is good.
Although the anode can be pre-lithiated in direct contact with the lithium foil, the degree of pre-lithiation is not easy to accurately control. Insufficient lithiation cannot sufficiently improve ICE; and excessive pre-lithiation may form a metal lithium plating layer on the surface of the anode.
Z. Y. Cao and others have improved the safety of pre-lithiation with lithium foil. The designed active material/polymer/lithium metal three-layer structure anode can be stable in ambient air for 30-60 minutes, which is sufficient for anode processing. The three-layer structure is: a metal lithium layer electrochemically deposited on a copper foil, the lithium layer is coated with a polymethyl methacrylate protective layer and an active material layer.