Novel Nanostructured Anodes For Green Energy Battery Storage

The quest to increase the lithium storage capacity of anodes in lithium-ion batteries is a prominent goal in battery research. The conventional graphitic Carbon-based anode material achieves a maximum capacity of 372 mAh g-1, limited by the stoichiometry of the lithiated state Lithium Carbide (LiC6). To overcome this limitation, Silicon anodes offer a theoretical storage capacity approximately ten times higher, albeit accompanied by a significant volume expansion issue. This study firstly explores various methods of fabricating composite materials as anodes, when combining Graphite and Silicon. The studies include the use of nano particle graphite as well as a physical method of nanoparticles deposition with a Matrix Assembly Clusters Source (MACS). The project was inspired by the ultimate prospect of employing cluster (nanoparticle) beam implantation techniques to embed small Silicon Nanoclusters, sized between 1-3 nm, into a porous carbon host. The utilization of such small Silicon particle sizes, embedded between Graphite particles, might possibly solve the volume expansion problem while retaining the benefit of additional storage density. Anodes were made using various graphites as reference active materials, both conventionally sized (D50 8.4 μm) and Graphite nano powder to aid homogenous dispersion, and with the addition of Silicon Nanoparticles. These were made into slurries with Carbon Black and binder and cast on to foil prior to assembly into half-cells with lithium metal. The reference anodes made using conventional graphite performed as expected, with specific capacities close to expected values. However, when using Nano Graphite, the morphology of the powder caused significant drying and processing issues, that made it difficult to reliably cast the anode, causing delamination and ultimately higher instances of cell failure and lower specific capacity. Integration of the Silicon nano powder gave some evidence of improved results, but data were inconsistent and hindered by processing issues and high instances cell failure. First demonstrative experiments utilising the MACS approach, which offers the advantage of integrating Silicon with larger Graphite particles, gave composite anodes that were able to be readily processed into an anode in the same way as conventional Graphite, without delamination or excessive cell failure. The resultant half-cells gave slightly higher capacity than reference Graphite cells, but more work is needed to develop and verify the processing to validate the extent of the Silicon coating on the Graphite and confirm its effect on capacity