There is a growing interest in the scientific community to develop materials with better storage properties for lithium-ion batteries. One possibility is to replace graphite, commonly used as an anode in commercial batteries, by advanced carbonaceous materials such as graphene or carbon nanotubes (CNTs).
The lithiation of CNTs remains a complex and fascinating subject mainly because it follows a different mechanism with respect to lithiation of graphite. In fact, fundamental aspects of the lithiation processes in CNTs still remain controversial and unclear. To date, the reason for nanotube degradation/amorphization is not clear, and consequently, it is difficult to design strategies to mitigate or completely avoid this undesired behavior. Researchers from IMDEA Energy in collaboration with IMDEA Materials have recently given some insights on the electrochemical processes responsible for degradation of CNTs under lithiation, in particular trying to clarify the role of amorphous carbon, the presence of defects, composition of SEI (solid electrolyte interfase), and so forth. From the application viewpoint, the study indicates that CNTF fabrics are not suitable as an anode material for lithium ion batteries mainly because of the high first-cycle irreversible capacity and to the high-voltage hysteresis. On the bright side, CNTFs show high capacity, rate capability, cycling stability, and a very promising electronic conductivity. The use of CNTF fabrics as scaffolds in composite electrodes or as current collectors, as well as prelithiation, could help exploiting these favourable properties while also limiting the impact of the mentioned drawbacks.
(*) Revealing the Mechanism of Electrochemical Lithiation of Carbon Nanotube Fibers. Nicola Boaretto*, Moumita Rana, Rebeca Marcilla, and Juan José Vilatela*. ACS Applied Energy Materials Vol. 3, 2020, Pages 8695-8705. https://pubs.acs.org/doi/10.1021/acsaem.0c01267
More information: Rebeca Marcilla, Senior researcher, Electrochemical Processes Unit, firstname.lastname@example.org
Scheme of the proposed lithiation mechanism. Raman spectra that demonstrate the amorphization of CNT fibers upon cycling