Abstract
A novel method for processing natural graphite for use in high performance Li-ion batteries is presented. The processing method utilises hydrodynamic jet cavitation (HJC) to produce a highly conductive graphite powder from a natural graphite precursor with the only consumables being electricity and water (process shown in Figure 1a). The HJC process produced a thin (carbon black)-like coating on the surface of the graphite particles, giving the material a higher conductivity compared to two other commercial graphite samples. In rate capability tests, LFP // graphite full cells produced a specific capacity 500% than the commercial graphite anodes (Figure 1c).This patented process is carbon neutral and aims to help the global electric vehicle (EV) market to produce high performing EVs whilst simultaneously lowering the high carbon footprint from producing the battery packs that power them.An in-depth characterisation study is performed on the powders, electrode slurry formulations and cells to determine how the surface characteristics of the graphite particles affect their electrochemical performance. The graphite powders were separated by particle size and tested in both coin and single layer pouch cells. Through SEM analysis, HJC graphite powders show a higher proportion of edge planes compared to basal planes, providing more sites for Li (de-)intercalation during charging and discharging (shown in Figure 1b). This explains their higher capacity at higher C-rates (5C + 10C) compared to the commercial standards. However, it is also found that the higher proportion of edge planes results in a substantially thicker solid electrolyte interphase (SEI) during cycling, consuming more of the Li inventory; resulting in a poorer initial coulombic efficiency and cycle life. The addition of electrolyte additives such as Lithium difluorooxalatoborate (LiDFOB), vinyl carbonate (VC) and VC derivatives are used to improve the coulombic efficiency of the coin and pouch cells. Figure 1
Published Version
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