Mixed-Dimensional (1D-2D) Carbon as a Conductive Additive and Enabler for Next Generation Lithium-Ion Batteries

Abstract

The race to develop the next generation of lithium-ion batteries with higher performance metrics (e.g. energy density, power density, cyclability) has spurred interest in carbon allotropes, such as carbon nanotubes (1D) and graphene (2D). Herein, a new multi-dimensional carbon material, comprised of long and entangled 1D nanotubes that unfurl into a spanning network of 2D sheetlets, is investigated as a conductive additive in lithium-ion battery cathodes. Compared to conventional conductive additives, this so-called 1.5D carbon material improves both electrical and thermal pathways between battery active materials within the electrode.In this presentation, the electrical, thermal, and electrochemical properties of the mixed-dimensional (1.5D) carbon are compared to conventional additives such as carbon black and graphite. Higher active material loadings, less heat generation, and more energy-dense cells can be enabled by the improved electrical conductivity, where three times less carbon black results in one order of magnitude higher electrode conductivity. The thermal conductivity of these cathodes is also enhanced in both the through- and in-plane directions, which is beneficial for battery thermal management. For instance, using a third of the carbon amount results in more than 30% and 240% higher through- and in-plane thermal conductivity values, respectively. The combination of these properties translates to overall improvements in electrochemical performance metrics including rate capability, lower cell impedance, and higher achievable capacities. Compared to cells with conventional carbon black, there is a 20% reduction in ohmic resistance determined by electrochemical impedance spectroscopy. In terms of capacity retention and rate capability, full cells cycled at a 2C charge and 0.5C discharge rate demonstrated 2.5% higher initial capacity than carbon black with a retention of 95% vs 94.4% after 120 cycles.