Mixed-dimensional multi-walled carbon nanotubes as a conductive network for improved lithium-ion battery performance

Abstract

Alternative conductive additives for lithium-ion batteries, such as carbon nanotubes and graphene, are academically well-established with pursued industrial opportunities while carbon black represents the global standard. However, further advancements are necessary to improve battery performance beyond current industrial metrics. Herein, a mixed-dimensional carbon material is introduced, featuring a network of 1D multi-walled nanotubes with 2D sheetlets, synthesized through a cost-effective process separating methane – a potent greenhouse gas – into carbon and low carbon intensity hydrogen. With proper slurry mixing, this material forms an expansive 3D conductive network within the electrode, enhancing electrical transport and thermal conductivity compared to carbon black electrodes. With only one-third of the carbon content (1 wt%), the electrical conductivity of a LiNi_0.5Mn_0.3Co_0.2O₂ cathode is 13 times higher than a carbon black reference, increasing both energy density and rate performance. The thermal conductivity is further improved by 40% (through-plane) and 200% (in-plane), promoting better heat dissipation. This carbon network also effectively retains transition metals during electrochemical cycling, limiting their migration to the anode, and thus reducing overall impedance build-up. The excellent compatibility of this conductive additive with state-of-the-art nickel-rich (85% nickel) layered oxides is also demonstrated, where 11.5 Ah pouch cells display >88% capacity retention after 1000 cycles at C/3.