context: In order to achieve higher power/energy densities for electrochemical energy storage, dual-ion batteries (DIBs), relying on the migration of both cations and anions to store charge concurrently, have been developed. Compared with lithium ion batteries, dual-ion migration behavior can shorten the charge carrier distance. From a cation perspective, lithium ions, as a charge carrier, have contributed to energy storage for several decades. However, many issues have also been raised, such as safety, excessive resource consumption, and environmental pollution. In the process of searching for substitutes, sodium ions, zinc ions, aluminum ions, and other metal ions have been investigated as charge carriers. Non-lithium electrochemical energy storage systems have shown signs of progress. However, no matter how they were improved, metal dendrites have still remained present during the anodic process. To address this limitation, the non-metal ionic liquid EMIm+[PF6]− has been employed as an electrolyte to realize charge transport. Unfortunately, due to the larger radius of EMIm+ (vertical: 4.3 Å; horizontal: 7.6 Å), it is not possible for traditional graphite anodes to provide a high intercalation capacity. Selecting new electrode materials to achieve the intercalation/deintercalation of EMIm+ can be a route to overcome this bottleneck limitation.
answer: graphite 