Na₂SO₄‐Polyacrylamide Electrolytes and Enabled Solid‐State Electrochemical Capacitors

Abstract

A highly ionic-conductive and high-performance neutral pH polymer electrolyte comprises of Na 2 SO 4 and polyacrylamide (PAM) was developed for solid electrochemical double-layer capacitors (EDLCs). Na 2 SO 4 was compared with Li 2 SO 4 baseline in liquid electrolyte and exhibited higher ionic conductivity and identical stability window. Na 2 SO 4 À PAM electrolytes were optimized by varying their salt-to-polymer ratio. While all compositions show excellent stability for over 30-day tracking period, an ionic conductivity of ca. 30 mS cm À 1 was attained at 10,000 : 1 molar ratio of Na 2 SO 4 :PAM, among the highest reported for neutral pH polymer electrolytes. Raman spectroscopy verified that the electrolyte maintained well-hydrated ions throughout the 30 days monitoring period. Solid EDLCs were constructed using activated carbon electrodes and Na 2 SO 4 À PAM electrolyte. They exhibited a wide 1.9 V operating window at 50 mV s À 1 CV scan rate, with comparable capacitance to its liquid baseline. The solid EDLCs outperformed many symmetric devices in terms of energy and power densities. They also displayed good rate capability (up to 500 mV s À 1 ) and excellent cycle life (> 8,000 cycles).

Unraveling Synergistic Redox Interactions in Tetraphenylporphyrin–Polyluminol–Carbon Nanotube Composite for Capacitive Charge Storage

“…35 The capacitance for the composite electrodes was calculated from the CV profiles by dividing the charge by the voltage window (C = Q/V) and normalizing to the volume of the CME. 16,36 To ensure good reproducibility, the CME was loaded with the composite films and tested a minimum of 10 times.…”

Ambiguous Role of Cations in the Long-Term Performance of Electrochemical Capacitors with Aqueous Electrolytes

“…high potentials of hydrogen and oxygen evolution. 26 It has to be pointed out that to reach such voltage values, the population of ions at the interface is crucial; although the presence of H 3 O + or OH − is essential in terms of formal hydrogen or oxygen evolution potentials, the role of other ions cannot be neglected. To date, mainly nitrate-or sulfate-based systems have been successfully surveyed.…”

“…In particular, when neutral aqueous electrolytes are applied, the corresponding ECs are capable of operating even at a voltage higher than the water decomposition voltage (ca. 1.5–1.8 V) due to the high potentials of hydrogen and oxygen evolution . It has to be pointed out that to reach such voltage values, the population of ions at the interface is crucial; although the presence of H 3 O + or OH – is essential in terms of formal hydrogen or oxygen evolution potentials, the role of other ions cannot be neglected.…”

“…It has to be pointed out that to reach such voltage values, the population of ions at the interface is crucial; although the presence of H 3 O + or OH – is essential in terms of formal hydrogen or oxygen evolution potentials, the role of other ions cannot be neglected. To date, mainly nitrate- or sulfate-based systems have been successfully surveyed. − They are considered purely capacitive systems, and it has been claimed that positive electrode damage is the main reason for system failure in the long-term perspective. − During the operation of the capacitor, the positive electrode is gradually oxidized and eventually corroded . The specific surface area and electrical conductivity of the electrode decrease as the oxygen content increases (>30%).…”

Optimization of the glass transition temperature of polyvinyl pyrrolidone/polyacrylamide blend films using response surface methodology

“…Similarly, PAM, an amorphous polymer, is being studied as a hosting polymer for electrolytic preparations. The polymer's amorphousness and functional groups allow it to form complexes with various salts 17 . Despite the fact that PAM has better amorphousness and functional groups to transport and dissociate the incorporated salts, its T g is greater than 100°C, indicating that the polymer is in a frozen state at room temperature, with only vibrational motions, which has a negative impact on ionic mobility 15 .…”