Graphite Anode for Lithium Ion Battery
Graphite anode is the key component of lithium ion battery (LIB). Its advantage over alternative negative electrode materials is its low intercalation voltage, which can be boosted by adding a co-solvent, and its high electrical conductivity. However, the first cycle irreversibility of graphite is still a major challenge to LIB applications. This article discusses different strategies to reduce the Cirr and achieve high coulombic efficiency (CCE) for commercial graphite anodes.
One strategy is the ex situ modification of graphite surface prior to cell preparation and assembly by using electrolyte additives or chemical treatments. The objective is to improve the interaction between lithium and the graphite and thus lower the initial irreversible capacity. However, this approach requires a large space with a protective atmosphere and adds another processing step before electrode assembly.
Another strategy is to prelithiate the graphite before battery fabrication. The purpose is to create a denser, more densely lithiated state of the graphite which is more resistant to dislocations during cycling, thus improving its rate capability. This can be achieved by pressing passivated lithium metal powder (PLP) loaded onto graphite anodes under Ar at elevated temperatures. The lithiation process is monitored electrochemically and crystallographically.
To further increase the rate capability of graphite anodes, a combination of both strategies has been developed. In this approach, the graphite is prelithiated with PLP in an Ar-filled glove box and the resulting lithiation extent (Stage 2L) is measured. Then, it is paired with an amphi-redox LMO@Gn and the plated metallic lithium is shuttled between the lithiated and unlithiated region of the graphite to overcome the first cycle irreversibility by increasing its surface area.