In Situ Studies of Ion Transport in Microporous Supercapacitor Electrodes at Ultralow Temperatures

Abstract

The ability to quickly store and deliver a significant amount of electrical energy at ultralow temperatures is critical for the energy‐efficient operation of high altitude aircraft and spacecraft, exploration of natural resources in polar regions and extreme altitudes, and astronomical observatories exposed to ultralow temperatures. Commercial high‐power electrochemical capacitors fail to operate at temperatures below –40 °C. According to conventional wisdom, mesoporous electrochemical capacitor electrodes with pores large enough to accommodate fully solvated ions are needed for sufficiently rapid ion transport at lower temperatures. It is demonstrated that strictly microporous carbon electrodes with much higher volumetric capacitance can be efficiently used at temperatures as low as –70 °C. The critical parameters, with respect to electrolyte properties and electrode porosity and microstructure, needed for achieving both rapid ion transport and efficient ion electroadsorption in porous carbons are discussed. As an example, the fabrication of an electrochemical capacitor with an outstanding performance at temperatures as low as –60 and –70 °C is demonstrated. At such low temperatures the capacitance of the synthesized electrodes is up to 123 F g−1 (≈76 F cm−3), which is 50–100% higher than that of the most common commercial electrochemical capacitor electrode at room temperature. At –60 °C selected cells based on ≈0.2 mm electrodes exhibited characteristic charge–discharge time constants of less than 9 s, which is faster than the majority of commercial devices at room temperature. The achieved combination of high energy and power densities at such ultralow temperatures is unprecedented and extremely promising for the advancement of energy storage systems.

Sulfur-Doped TiO2 Anchored on a Large-Area Carbon Sheet as a High-Performance Anode for Sodium-Ion Battery

“…Additionally, the small split that separately occurred at 161.64 eV corresponds to the anionic S 2– species, which is also in good agreement with previous reports . In the case of C 1s (Figure d), the feature of carbon mainly appears at 284.81 (C–C/C–S), 285.99 (C–O/C–S), 286.94 (CO), 288.54 (−CO 2– ), and 291.29 eV (π–π*). ,, More significantly, the peak at 283.79 eV can be assigned to the C–Ti covalent bond, , and the peaks at 284.81 and 285.99 eV could be ascribed to the C–S bridge bond. , …”

Printing Porous Carbon Aerogels for Low Temperature Supercapacitors

“…The 3D-MCA electrode achieved a gravimetric capacitance of 148.6 F g –1 at a scan rate of 5 mV s –1 , which is significantly higher than that of MCA (63.8 F g –1 ). It also outperforms many other previously reported carbon electrodes at similar or even higher temperatures, such as graphene films (60 F g –1 at 1 mV s –1 , −40 °C), activated graphene (100 F g –1 at 1 mV s –1 , −50 °C), activated carbon (92 F g –1 at 5 A g –1 , −60 °C), mesoporous graphene (20 F g –1 at 1 A g –1 , −70 °C), carbon nanotubes (53.4 F g –1 at 100 mV s –1 , −70 °C), and zeolite-templated carbon (117 F g –1 at 1 mV s –1 , −70 °C) . Most importantly, the 3D-MCA electrode retained 48% of its capacitance when the scan rate increased from 5 to 200 mV s –1 .…”

Lithographically Patterned Thin Activated Carbon Films as a New Technology Platform for On-Chip Devices

“…The highest specific capacitance and the best capacity retention were achieved in the ACF-2h electrode. A specific capacitance in excess of 325 F g –1 was observed at a very high current density of 45 000 mA g –1 , which has never been reported before for any type of EDLC or supercapacitor electrodes. ,,,,,,− The large average pore size of ACF-2h (Figure b) may have assisted in the low resistance to the transport of ions within this sample. Indeed, at a current density of 22 500 mA g –1 the IR drop is only 5% of the total voltage range (inset in Figure b).…”