researchers at drexel university (philadelphia, pa.) have created a fabric-like material from a thick, ion-rich gel electrolyte absorbed into a freestanding at of porous carbon nanofibers that could produce more efficient energy storage devices that are less susceptible to leaks or thermal runaway.
to build their freestanding, solid-state supercapacitor, drexel researchers electrospin a mat of carbon nanofibers and coat them with an ion-rich gel. (drexel university)
according to a report from the university, the researchers claim to have completely removed the flammable component of a battery and created an electrode that has the potential for lighter storage devices.
“not only is the group’s supercapacitor solvent-free — which means it does not contain flammable liquid — but the compact design is also more durable and its energy storage capacity and charge-discharge lifespan are better than comparable devices currently being used,” the report continued.
“it is also able to operate at temperatures as high as 300°c, which means it would make mobile devices much more durable and less likely to become a fire hazard due to abuse.”
the key to producing the cloth-like electrode was electrospinning, a process that deposits a carbon precursor polymer solution in the form of a mat by extruding it through a rotating electrical field. as the article explained, it is kind of like the microscopic equivalent of making cotton candy.
“the ionogel is then absorbed in the carbon fiber mat to create a complete electrode-electrolyte network,” the article added. “its excellent performance characteristics are also tied to this unique way of combining electrode and electrolyte solutions. this is because they are making contact over a larger surface area.”
it continued, “the mat provides a greater surface area for ions from the ionogel to access the electrode, which increases the capacity and improves the performance of the energy storage device. it also eliminates the need for many of the scaffolding materials that are essential parts of forming the physical electrode, but don’t play a role in the energy storage process and contribute a good bit to the device’s overall weight.”
the research was recently published in applied materials & interfaces. the abstract stated:
“a high-performance, self-standing solid-state supercapacitor is prepared by incorporating an ionic liquid (il)-rich ionogel made with 95 wt % il (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) and 5 wt % methyl cellulose, a polymer matrix, into highly interconnected 3-d activated carbon nanofiber (cnf) electrodes.
“the ionogel exhibits strong mechanical properties with a storage modulus of 5 mpa and a high ionic conductivity of 5.7 ms cm–1 at 25 °c. the high-surface-area cnf-based electrode (2282 m2 g–1), obtained via an electrospinning technique, exhibits hierarchical porosity generated both in situ during pyrolysis and ex situ via koh activation.
“the porous architecture of the cnf electrodes facilitates the facile percolation of the soft but mechanically durable ionogel film, thereby enabling intimate contact between porous nanofibers and the gel electrolyte interface. the supercapacitor demonstrates promising capacitive characteristics, including a gravimetric capacitance of 153 f g–1, a high specific energy density of 65 w h kg–1, and high cycling stability, with a capacitance fade of only 4% after 20 000 charge–discharge cycles at 1 a g–1.
“moreover, device-level areal capacitances for the gel il cell of 122 and 151 mf cm–2 are observed at electrode mass loadings of 3.20 and 5.10 mg cm–2, respectively.”
|