Influence of Electrolyte on the Electrochemical Performance of the Biomass-Derived Hard Carbon for Potassium Ion Batteries

There is a promising aspect of potassium-ion batteries (KIB) alternative to lithium-ion batteries (LIB) due to a similar charge storage mechanism. However, the major hurdles, such as higher volume pulverization during continuous cycling, lower Coulombic efficiency, and subsequent fading, need to be addressed before the commercialization of KIB. In this regard, the choice of electrolytes and their impact on the electrochemical performance of the electrode is quite crucial. Here, a two-step pyrolysis method was used to synthesize hard coconut shell-derived hard carbon (HHC). The synthesized powder was characterized by various analytical techniques to confirm the formation of pyrolyzed carbon. The surface area of the synthesized powder was calculated to be around 40.9 m².g⁻¹. Three types of electrolytes such as 1 M KPF₆ in EC: DEC (1 : 1 v/v), 0.8 M KPF₆ in EC: DEC (1 : 1 v/v), and 1 M KTFSI in TEGDME, were prepared to study the electrochemical performance of the assembled KIB cell. The study demonstrated that compared to other electrolytes, 0.8 M KPF₆ in EC: DEC (1 : 1 v/v) exhibited higher coulombic efficiency, higher charge storage capacity, and much better capacity retention. The EIS studies revealed that a lower solution resistance and a higher pseudo capacitance have aided in better electrochemical performance for 0.8 M KPF₆ in EC: DEC (1 : 1 v/v) electrolyte. The cell exhibited a higher specific capacity of 187.3 mAh g⁻¹ at a current density of 200 mA g⁻¹ with a higher coulombic efficiency of 96.8 % and retained about 86.7 % of the original capacity after 100 cycles of charge-discharge. This promising combination of appropriate electrolytes and electrodes can further advance the research progress of potassium ion batteries.