Towards Improving the Practical Energy Density of Li-Ion Batteries: Optimization and Evaluation of Silicon:Graphite Composites in Full Cells

Increasing the energy density of Li-ion batteries is very crucial for the success of electric vehicles, grid-scale energy storage, and next-generation consumer electronics. One popular approach is to incrementally increase the capacity of the graphite anode by integratingsilicon into composites with capacities between 500 and 1000 mAh/g as a transient and practical alternative to the more-challenging,silicon-only anodes. In this work, we have calculated the percentage of improvement in the capacity of silicon:graphite compositesand their impact on energy density of Li-ion full cell. We have used the Design of Experiment method to optimize composites usingdata from half cells, and it is found that 16% improvements in practical energy density of Li-ion full cells can be achieved using 15to 25 wt% of silicon. However, full-cell assembly and testing of these composites using LiNi0.5Mn0.5Co0.5O2cathode have provento be challenging and composites with no more than 10 wt% silicon were tested giving 63% capacity retention of 95 mAh/g at only50 cycles. The work demonstrates that introducing even the smallest amount of silicon into graphite anodes is still a challenge andto overcome that improvements to the different components of the Li-ion battery are required.Peer reviewed: YesNRC publication: Ye