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Bundled and dispersed carbon nanotube assemblies on graphite superstructures as free-standing lithium-ion battery anodes

Yan, Yiran, Li, Changling, Liu, Chueh, Mutlu, Zafer, Dong, Bo, Liu, Jingjing, Ozkan, Cengiz S., Ozkan, Mihrimah
Carbon 2019 v.142 pp. 238-244
additives, anodes, carbon nanotubes, electrochemistry, electrolytes, foams, graphene, lithium batteries, manufacturing, physical properties, surface area
Carbonaceous materials are intensively used as additives or active electrode materials in lithium-ion battery (LIB) industry due to their stable chemical and physical properties. Compared to developing next-generation high-capacity non-carbonaceous anode materials, improvement on current carbonaceous materials could lead to instant commercial values due to less process modifications to the battery manufacturing. Here, we report a facile approach to synthesize carbon nanotubes (CNTs) with controlled assemblies: well-dispersed CNTs vs. bundled CNTs. Furthermore, we incorporated these CNTs onto three-dimensional (3D) graphite foams as free-standing anodes for LIBs. This hierarchical 3D network provided high surface area and ultra-high conductivity with enhanced battery capacity. With controlled growth conditions, the assembly of CNTs can be changed from bundled state to dispersed state, resulting in a significant improvement in electrochemical performance. The dispersed CNTs showed a higher specific capacity of above 800 mAhg−1 over 120 cycles, while CNT bundles exhibited a specific capacity of 500 mAhg−1. The loose structure of well-dispersed CNTs provides sufficient active interfaces between electrolyte and materials, as well as shortened ion transport path. Insights can be gained in improving state-of-the-art battery performance by controlling the bulk assemblies of CNT additives.