Carbonization and Laser Structured Graphite Cathode for Lithium Ion Batteries
Graphite has a number of excellent properties which make it an ideal cathode material for lithium ion batteries (LIBs): 1. It has a remarkable capacity, 2. It can be easily processed and manufactured, 3. It is environmentally friendly, 4. It is highly recyclable, 5. It enables efficient energy storage.
Despite its outstanding performance, graphite cathodes still need to be improved for advanced LIBs. In this context, carbonization and laser structuring have been investigated as promising approaches to improve the LIB performance.
A crucial factor is the SEI layer at the electrode/electrolyte interface, which prevents direct electronic contact between graphite particles and the electrolyte. It kinetically suppresses the continuous electrolyte decomposition and inhibits solvent co-intercalation, while allowing for lithium cation conduction.
This is primarily achieved through the introduction of a solid electrolyte interphase (SEI). The solid layer is formed essentially during the first charge and discharge cycle, when it impedes the graphite particle desolvation from the electrolyte and thus reducing the electrolyte permeability for the graphite.
Furthermore, the formation of this SEI film is accelerated by the ex situ modification of the graphite surface prior to the electrode preparation and cell assembly (see Section 3.2.2). Besides, several other factors influence the graphite intercalation/de-intercalation process, e.g., the graphite particle size and morphology, electrode architecture, the chemical composition of the SEI, etc.
The XPS spectra of graphite powders show the appearance of the doublet peak E2g2(i) and E2g2(b) during lithiation and de-intercalation, respectively. The reversibility of this peak was also shown by the in-situ Raman spectrum. This spectral feature is indicative of the graphite intercalation/de-intercalation mechanism.