Figure 4. Electrochemical performance of capacitor with SAPO-PTFE composite electrolyte, 105% H₃PO₄ electrode ionomer, and HNO₃-activated carbon.

a) Energy density as a function of temperature, where the current density and the charge voltage were set in the range of 1.5–3 A g⁻¹ and at 1 V, respectively. b) Energy density as a function of current density at 100 and 200°C, where the charge voltage was set at 1 V. c) Energy density as a function of charge voltage at 100 and 200°C, where the current density was set in the range of 3–6 A g⁻¹. The procedures for Methods 1 and 2 are described in the manuscript.