3.1 Preparation of ink with expanded graphite
The ink preparation workow starts with a donor-type intercalation of raw graphite as shown in Fig. 1. The donor-type intercalation compound (IC) is formed by donating electrons to the graphite matrix, thus, making it negatively charged, and accompanied by the insertion of positively charged species to sandwich a graphene layer between two layers of intercalants (stage 1 IC).18,19 In contrast to oxidation, i.e., the withdrawal of electrons from a graphite matrix, such an approach prevents the formation of any functional groups, and hence, preserves the conductive properties of graphene. The formed stage 1 donor-type IC slowly decomposes upon exposure to ambient conditions into mixtures of a higher stage IC.20 For instance, the IC ake shown in Fig. 1b exhibits charging effects at the edges and planes which can be attributed to lithium salts dein-tercalating from the graphite matrix. Therefore, the intercalated materials were analyzed or used immediately aer their synthesis.