Overcoming Through-Plane Resistance in Lithium-Ion Battery Cathode Electrodes via the Application of Trace High-Aspect-Ratio Carbon Nanofiber Carbon Additives with Carbon Nanotube-Coated LiNi0.8Co0.1Mn0.1O2

As the demand for high-capacity Ni-rich lithium-ion batteries continues to grow, the push to increase their energy density at the material level also increases. To achieve higher energy densities, binder material (BM) and carbon additive (CA) ratios must be minimized, resulting in careful consideration of their selection. Recently, carbon nanotubes (CNTs) have been popularized; however, unwanted migration of CNTs during electrode manufacturing causes severe carbon additive agglomeration on the surface, leaving behind a poor conductive network throughout the electrode. This is particularly emphasized, as the binder concentration is lowered to maximize cell energy density. One of the possible solutions is to establish a robust electrically conductive network by incorporating a trace amount of high-aspect-ratio carbon nanofibers (CNFs) alongside CNTs as the CA in Ni-rich active material (AM) cathode electrodes. The results indicate that adding an optimized amount of 0.25 wt % CNFs with 0.75 wt % CNTs constructs an effective conductive network and reduces the through-plane (from the electrode surface to the current collector) resistance significantly. With an electrode ratio of 98:1:1 (AM/CA/BM), the performance is outstanding and shows a capacity retention of 93.7% after 100 cycles at 1C. It is also observed that CNFs help in developing a good electrical network in high-energy-density thick electrodes, as the cycling performance of dual conductive additive CNF/CNT mix electrodes achieves a capacity retention of 97.01% at a loading level of ∼20 mg cm–2. Therefore, the addition of CNFs as a trace with CNTs proved beneficial to bypass through-plane parallel resistances within the electrode caused by undesirable migration of CNTs during electrode synthesis. Hence, providing sufficient electrical highways from the electrode surface to the current collector through addition of trace CNFs can significantly enhance the electrochemical performance of the cells and become a facile and retrofittable solution to high electrical resistances arising in the current electrode production process.