The Impact of Specific Surface Area and Pore Structure on Potassium-Ion Batteries
Potassium-ion batteries (PIBs) are considered an important complement to existing lithium-ion batteries (LIBs) due to their environmental friendliness, abundant raw material resources, and low cost. PIB anode materials have become the focus of research, and carbon-based anodes have been studied for their high conductivity and chemical stability.
Graphite has been heavily studied for PIBs due to its theoretical storage capacity for K ions and therefore high energy density, shown schematically in Figure 1a. However, there are several limitations. The K+ ion has low mobility in graphite channels and pores due to its large ionic radius.(1) Many scholars have improved the performance of carbon materials in PIBs by surface modification, structural design, and functionalization.(1,2)
While graphite modification has been shown to improve K+ ion intercalation/deintercalation, attempts to increase the interlayer spacing often introduce defects into the material which reduce performance and stability. Alternatively, hard carbon is an amorphous material with randomly oriented sp2 planes. The disordered structure results in inherently larger spacing that facilitates faster intercalation and deintercalation of K+ ions. Because of this, hard carbon anodes have demonstrated excellent cycling stability when paired with an appropriate electrolyte.(3) The optimization of cathodic material properties plays an integral role in PIB chemistry, and therefore surface area and pore size have received attention from scholars.(4)
