High-energy density LixSi-S full cell based on 3D current collector of few-wall carbon nanotube sponge

Abstract

For the practical use of innovative, high-energy-density batteries, loading of high-capacity active materials at high gravimetric and volumetric fractions is required. In this work, a flexible self-supporting paper of few-wall carbon nanotubes (FWCNTs) was used as three-dimensional conductive matrices to capture Si and S at ∼70 mass% without metal foils nor polymeric binders. The full cell comprised of the LixSi-CNT and S-CNT electrodes with a negative to positive (N/P) capacity ratio of ∼1 realized high initial energy densities of 810 W h kg−1 and 680 W h L−1 based on the total mass and volume of the electrodes, respectively. However, the cell showed a poor cycle performance due to the depletion of active Li. The increased N/P capacity ratio of 2.7 drastically improved the cycle performance, realizing an energy density of 610 W h kg−1 at first discharge and 360 W h kg−1 after 100 cycles based on the total mass of the electrodes. The full cell architecture based on 3D current collector of FWCNTs is a promising solution for loading active materials at high fractions and achieving high energy densities at the total electrode level.