context: Li and co-authors applied PTCDA-derived polymer P10 as the anode for aqueous K-ion batteries. Saturated solutions of K2SO4 (∼0.69 M) or KNO3 (∼3.75 M) were tested as the electrolytes. The potassium nitrate solution enabled better rate capabilities with P10 as the active material, owing to the higher conductivity. Particularly, ∼90 mA h g−1 was delivered at 5.4 A g−1, which was about 70% of the value achieved at 0.36 A g−1. A full cell with the potassium hexacyanoferrate cathode had an energy density of 24.2 W h kg−1 (per mass of both electrodes), could reach a high power of 2.08 kW kg−1, and retained 74% of the capacity after 300 cycles.
answer: K2SO4 (∼0.69 M) or KNO3 (∼3.75 M) 