Electrochemically triggered decoupled transport behaviors in intercalated graphite: From energy storage to enhanced electromagnetic applications

Pyrolytic graphite (PG) with highly aligned graphene layers, present anisotropic electrical and thermal transport behavior, which is attractive in electronic, electrocatalyst and energy storage. Such pristine PG could meeting the limit of electrical conductivity (∼2.5 × 10⁴ S·cm⁻¹), although efforts have been made for achieving high-purity sp² hybridized carbon. For manipulating the electrical conductivity of PG, a facile and efficient electrochemical strategy is demonstrated to enhance electrical transport ability via reversible intercalation/de-intercalation of AlCl₄⁻ into the graphitic interlayers. With the stage evolution at different voltages, variable electrical and thermal transport behaviors could be achieved via controlling AlCl₄⁻ concentrations in the PG because of substantial variation in the electronic density of states. Such evolution leads to decoupled electrical and thermal transport (opposite variation trend) in the in-plane and out-of-plane directions, and the in-plane electrical conductivity of the pristine PG (1.25 × 10⁴ S·cm⁻¹) could be massively promoted to 4.09 × 10⁴ S·cm⁻¹ (AlCl₄⁻ intercalated PG), much better than the pristine bulk graphitic papers used for the electrical transport and electromagnetic shielding. The fundamental mechanism of decoupled transport feature and electrochemical strategy here could be extended into other anisotropic conductive bulks for achieving unusual behaviors.