A supercapacitor constructed with a partially graphitized porous carbon and its performance over a wide working temperature range

Abstract

A supercapacitor that possesses excellent performance in a wide temperature range is constructed with a partially graphitized porous carbon (PGPC) as the electrode material and tetraethylammonium tetrafluoroborate/propylene carbonate (Et 4 NBF 4 /PC) as the electrolyte. The PGPC-based electrode shows 10 a very consistent performance at a wide temperature range from -20 to 50 o C. At the working temperatures as high as 50 o C and as low as -20 o C, it delivers the specific capacitances of ~148 and ~135 F g -1 , respectively, and the supercapacitors exhibit high energy densities of ~46 and ~43 Wh kg -1 . Especially, the low-temperature capacitive performance and rate capability of PGPC are much better than the normally used activated carbon and among the best ones for ever-reported carbon-based 15 supercapacitors. More significantly, the PGPC-based supercapacitor shows excellent cycling performance at all tested working temperatures, with a capacitance retention of ~98% after 1000 cycles at 5 A g -1 even when the working temperature decreases to -20 o C.A supercapacitor constructed with a partially graphitized porous carbon (PGPC) as the electrode material and Et 4 NBF 4 /propylene carbonate as the electrolyte exhibits high energy densities of ~46 and ~43 Wh kg -1 at 50 °C and -20 °C, respectively.

Well‐Aligned Hierarchical Graphene‐Based Electrodes for Pseudocapacitors with Outstanding Low‐Temperature Stability

“…The capacitance at −30 °C retains 70.2∼80.8 % of the capacitance at RT with a current density of 1 A g −1 , which is comparable to the temperature stability of EDLCs with the same operating temperature range . The capacitance retention declines with the increasing current density, in good agreement with prior work . To better understand the temperature‐dependent electrochemical behavior of the pseudocapacitor, the relationship between the capacitance and the operating temperature is further investigated.…”

“…As temperature decreases from 25 to 0 °C, 90.7 % of the capacitance is retained at 1 A g −1 . Such a capacitance retention of the as‐prepared pseudocapacitor is significantly larger than those of MnO 2 ‐based composite materials, Co 3 O 4 , and Fe 3 O 4 /carbon and even comparable to those of EDLCs within similar temperature ranges …”

“…However, the capacitive performance of both EDLCs and pseudocapacitors exhibits great sensitivity to their operating temperature, particularly at low temperatures . Recent studies show that the specific capacitance of EDLCs (typically <200 F g −1 ) decays by 5∼12 % when the operating temperature decreases from 25 to 0 °C . Such a phenomenon of attenuated capacitance at relatively low temperatures is more pronounced in pseudocapacitors.…”

“…The diffusion coefficient of electrolyte ions reduces with the decreasing temperature, leading to a reduced number of ions diffusing onto the electrode surfaces and thus a decreased capacitance . This phenomenon could be more noticeable at high charge rates . With reduced ion diffusion distance and improved ion transport rate, high capacitance retention could be achieved over a wide temperature range .…”

“…[13] Recent studies show that the specific capacitance of EDLCs (typically < 200 F g À 1 ) decays by 5~12 % when the operating temperature decreases from 25 to 0°C. [14][15][16][17] Such a phenomenon of attenuated capacitance at relatively low temperatures is more pronounced in pseudocapacitors. Although pseudocapacitors offer higher specific capacitances (typically 200~1000 F g À 1 ) than those of EDLCs, [18,19] their large capacitance decay (in the range of 25~45 %) within the same operating temperature range could dramatically hinder the practical applications in harsh temperature environments.…”