Heat generation in electric double layer capacitors with neat and diluted ionic liquid electrolytes under large potential window between 5 and 80 °C

Calorimetry Can Detect the Early Onset of Hydrolysis in Hybrid Supercapacitors with Aqueous Electrolytes

“…For both devices, the cell potential 𝜓 𝑠 (𝑡) varied almost linearly with time 𝑡 except at the beginning of the charging or discharging steps featuring an IR drop. A similar behavior can be observed in many EDLCs and hybrid supercapacitors with surface redox reactions [19,41,42,70]. Here also, no electrolyte decomposition was evident in the measured cell potential 𝜓 𝑠 (𝑡) as the cycle period 𝑡 𝑐𝑑 monotonically decreased with increasing current 𝐼. Interestingly, the galvanostatic cycle period 𝑡 𝑐𝑑 was shorter for Device 2 than for Device 1, as corroborated by its smaller capacity (Fig.…”

“…Fig. 7 shows the measured cyclic voltammograms for scan rate (a) 𝜈 = 10 and (b) 𝜈 = 30 mV/s for potential window ranging from 1.2 V to 2.0 V. For both scan rates 𝜈, no sharp rise in current at high cell potential voltage 𝜓 𝑠 , often associated with hydrolysis reaction, was observed [41,42,65]. This unequivocally establishes that the early onset of hydrolysis could be observed with isothermal operando calorimetry before it could be observed with electrochemical measurements.…”

“…Recently, isothermal operando calorimetry measuring the time-dependent heat generation rates, at each electrode separately, during galvanostatic cycling has been successfully used to identify the thermal signature of different charging mechanisms in EDLCs with aqueous [38], organic [38][39][40][41], and ionic liquid [40][41][42] electrolytes. These mechanisms included (i) ion desolvation and adsorption [39][40][41][42], (ii) overscreening effect [39,40], (iii) organic solvent decomposition [42], and (iv) irreversible ion intercalation in AC electrode under different temperatures and potential windows [42]. Moreover, a new in situ cell was developed for simultaneous thermal analysis (STA) to measure simultaneously heat dissipation and weight changes as well as resistance and capacitance in an EDLC device during cycling or float tests [43].…”

Operando Calorimetry Investigation of Particle Size Effects on Heat Generation in Wadsley–Roth (W0.2V0.8)3O7-Based Electrodes

“…Several calorimetric measurement techniques have been used to probe heat generation associated with battery operation and electrical energy losses. For instance, differential scanning calorimetry, , accelerating rate calorimetry, , and operando isothermal calorimetry , have been used to develop thermal management systems to prevent thermal runaway and to investigate transport processes as well as chemical reactions occurring during battery cycling. , Furthermore, our previous operando isothermal calorimetry studies using a custom-made calorimeter capable of measuring the instantaneous heat generation rates have revealed thermal signatures associated with a variety of physicochemical phenomena including ion adsorption/desorption in supercapacitors, − electrolyte decomposition at high voltages and/or high temperatures, , ion intercalation, overscreening effects, , resistive losses, ,− and insulator to metal transition . In the present study, an operando isothermal calorimeter was used to investigate the energy dissipation mechanisms in (W 0.2 V 0.8 ) 3 O 7 electrodes during cycling and the effect of particle size on heat generation.…”

Design and Use of a Novel In Situ Simultaneous Thermal Analysis Cell for an Accurate “Real Time” Monitoring of the Heat and Weight Changes Occurring in Electrochemical Capacitors

“…Furthermore, they also offer the possibility to distinguish between the heat generated at each electrode. [21][22][23][24][25][26][27][28] Therefore, in operando calorimeters can be considered as a powerful tool to investigate the heat generation in EDLCs. Nevertheless, their use is not especially easy and they are quite limited in their area of application, especially as custom-made instruments are required.…”