High Conductivity, High Strength Solid Electrolytes Formed by in Situ Encapsulation of Ionic Liquids in Nanofibrillar Methyl Cellulose Networks

Abstract

Strong, solid polymer electrolyte ion gels, with moduli in the MPa range, a capacitance of 2 μF/cm(2), and high ambient ionic conductivities (>1 × 10(-3) S/cm), all at room temperature, have been prepared from butyl-N-methyl pyrrolidinium bis(trifluoromethylsulfonyl) imide (PYR14TFSI) and methyl cellulose (MC). These properties are particularly attractive for supercapacitor applications. The ion gels are prepared by codissolution of PYR14TFSI and MC in N,N-dimethylformamide (DMF), which after heating and subsequent cooling form a gel. Evaporation of DMF leave thin, flexible, self-standing ion gels with up to 97 wt % PYR14TFSI, which have the highest combined moduli and ionic conductivity of ion gels to date, with an excellent electrochemical stability window (5.6 V). These favorable properties are attributed to the immiscibility of PYR14TFSI in MC, which permits the ionic conductivity to be independent of the MC at low MC content, and the in situ formation of a volume spanning network of semicrystalline MC nanofibers, which have a high glass transition temperature (Tg = 190 °C) and remain crystalline until they degrade at 300 °C.

Recyclable High‐Performance Polymer Electrolyte Based on a Modified Methyl Cellulose–Lithium Trifluoromethanesulfonate Salt Composite for Sustainable Energy Systems

“…Unlike cellulose, which only contains hydroxyl functional groups, some of the functional groups are substituted by methoxy groups; thus, methyl cellulose is slightly less hydrophilic (less soluble in water compared to some other cellulose derivatives with more hydroxyl groups, such as hydroxypropyl cellulose) and tends to be more stable in water and protic solvents. Additionally, the physical appearance and mechanical strength of methyl cellulose are similar to those of some synthetic plastic polymers (e.g., polyethylene); hence, its application in highly durable flexible devices is promising . The change in the chemical structure of methyl cellulose upon reaction is illustrated in Figure a.…”

“…However, without substantial modification, their ion transport properties are rather mundane; hence, approaches such as hybridization or chemical functionalization are necessary to utilize them sufficiently. Nevertheless, these environmentally friendly, naturally abundant, and biodegradable polymers are still very attractive candidates for future energy‐storage devices, especially as concerns about the sustainability of energy systems are increasingly emphasized …”

Ionic Liquids as Environmentally Benign Electrolytes for High‐Performance Supercapacitors

“…Durable, self‐supporting solid ion gel polymer electrolytes, with moduli >100 MPa and presenting outstanding ambient ionic conductivities, i.e., over 10 −3 S cm −1 , a capacitance of 2 µF cm −2 and a very wide stability window of 5.6 V at RT were prepared by Mantravadi et al, by employing [BMPyr][TFSI] with methyl cellulose (MC) as gel former. For that, [BMPyr][TFSI] was first dissolved in a mixture of MC in DMF that was subsequently removed to form a thin, flexible, self‐standing ion gel containing up to 97 wt% IL.…”

“…Durable, self-supporting solid ion gel polymer electrolytes, with moduli >100 MPa and presenting outstanding ambient ionic conductivities, i.e., over 10 −3 S cm −1 , a capacitance of 2 µF cm −2 and a very wide stability window of 5.6 V at RT were prepared by Mantravadi et al, [141] [142] [TFSI], poly (diallyldimethylammonium) bis (trifluoromethanesulfonyl) imide. Using activated carbon electrodes impregnated with this electrolyte, the resulting symmetric SC showed a C sp of 100 F g −1 and an ED of 32 Wh kg −1 .…”

Surfaces modification of methylcellulose: Cobalt nitrate polymer electrolyte by sulfurated hydrogen gas treatment

“…Methylcellulose (MC) is one of the most abundant, inexpensive, and environmentally friendly natural polymer . In addition to its excellent thermal, mechanical, and chemical stabilities, MC has good film‐forming properties.…”