Nanotube-enhanced Carbon Graphite (NTeC-G) is the latest advanced material for Li-ion batteries. This material is a carbon nanotube CNT-graphite hybrid that is low cost and easy to handle. In this type of CNT-coated graphite material, a “carpet” layer of CNTs are attached to the exterior of graphite particles, providing a highly porous surface coating on a solid graphite core.
In this growth process, a solid catalyst is mixed with natural or synthetic graphite, and the mixed material is placed in a reactor for multi-walled CNT growth. This material can be grown using a simple catalytic process in a specialized reactor. Graphite particles are seeded with a metallic catalyst, which drives CNT growth on the graphite core. CNTs grow directly on the graphite particles and remain attached once growth is complete. The growth process for these hybrid CNT/graphite particles is simple enough for scalable production with high yield and low cost. Multi-walled CNTs grow on the graphite core with controllable diameter (typically 20-25 nm) and length (3-10 μm). The final step in producing both types of materials is purification, where the carbon mixture is heated to high temperature for graphitization and removal of metal impurities. SEM images of uncoated graphite and the NTeC-G-carpet material are shown below.
Above: SEM image of 5-10 μm graphite particles.
Above: CHASM’s NTeC-G-carpet material with CNTs grown on graphite particles in a specialized reactor.
This CNT-graphite hybrid material is quite easy to handle and integrate into cylindrical battery cells, coin cells, and pouch cells. As the material is in the solid state, it can be mixed with a surfactant and binder to form a slurry. This slurry can then be spread onto a copper foil and dried, yielding a porous film with low resistance. No specialized growth processes are required to integrate these materials with other standard battery materials.
As can be seen above, the web of CNTs forms a highly porous surface on top of the core graphite particles. The porous nature of this CNT-graphite hybrid material provides a number of benefits. For example, when used as an anode in Li-ion batteries, NTeC delivers:
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