With more and more electric vehicles (EV) hitting the market, the need for better and more robust energy storage system increases, and silicon has been a promising candidate for the next generation anode material to satisfy the high energy density and high-power requirements for electric vehicles because of its extremely high theoretical capacity. This has allowed the design of thinner electrodes to reduce the diffusion time scales and deliver a fast charge. However, at high charge and discharge rates, low electrical conductivity (~1.12 eV) of silicon hampers the battery performance. As a result, a lot of research has been conducted to improve the performance of silicon anodes using nanoscale carbon to increase the electrical conductivity. Graphene has been used to synthesize Si/Gr hybrid anodes due to its high conductivity.

Graphene nanoribbons (GNRs) , a part of the graphene family, are one-dimensional graphene nanostructures which tune its electrical properties based on dimensional confinement. GNR has a higher conductivity than Graphene. It also has high aspect ratio and surface area to provide a strong conductive path along with mechanical strength to support the silicon anode. Due to presence of GNR, lithium-ion transport into silicon nanostructures was enhanced. As a result, 50% of graphene was replaced by 50% GNR with silicon nanoparticles to form anodes. Due to the highly conducting structure of GNR, capacity at high rates was significantly improved because of the improved silicon utilization. Since GNR’s dimensions are in nanometer range, connection with silicon nanoparticles is better. It not only improves silicon to silicon conductivity, but it also acts as a filler for better connection of graphene with silicon nanoparticles.

Addition of graphene nanoribbons can improve the lithium-ion transport within the anode but to enhance the high charge transfer rate further, Si/GNR/Gr hybrid, high rate-capable anodes were paired with Polyimide (PI)/Polysilsesquioxane (PSSQ) hybrid separators which also shown to exhibit an improved charge transfer rate. At high rates such as 3C and 5C, the effect of separator on the cell performance becomes more prominent. While Celgard’s performance was very unstable at both 3C and 5C, at 3C, the cycling of hybrid separators did not get impacted, despite the relatively harsher conditions. This synergistic combination of high-rate capable silicon/graphene anode and hybrid separator outperformed the commercially used separator especially at high-rate cycling. Cells with Si/GNR/Gr anode paired with the PI/PSSQ separator delivered an impressive capacity of 1,000 mAh/g at high charge/discharge rates of 5C/5C.