New crosslinked gel electrolytes could create high energy density supercapacitors rivaling batteries
7 December 2016
Researchers from Augmented Optics Ltd. and the University of Surrey, in collaboration with the University of Bristol, have developed new, crosslinked gel-matrix polymer electrolytes exhibiting measured capacitance values more than 100 times those of conventional electrolytes. The new gel electrolytes are compatible with all normal production electrodes.
Augmented Optics, which has formed a subsidiary, SuperCapacitor Materials, to commercialize the materials, believes that the combination of existing electrodes and the new electrolytes have the potential to create supercapacitors that have energy storage capacities which can approach or exceed existing battery systems.
Supercapacitors feature long cycle life and high power density; they can perform thousands of high power charge/discharge cycles without loosing energy storage capacity. However, compared to batteries, they are hampered by low energy density, limiting the amount they can store.
In a paper earlier this year published in the RSC Journal of Materials Chemistry A, researchers at Seoul National University in Korea who are developing their own higher-performance cross-linked polymer-ionic liquid electrolyte succinctly explained:
LIBs [Li-ion batteries] have intrinsic limitations in power densities due to their energy storage mechanisms, so SCs [supercapacitors] that show high energy densities and wide operating voltages have been researched extensively. There are two ways to enhance the energy density of SCs: increasing capacitances and widening the operating voltages.
These methods work because the energy density is proportional to the capacitance and operating voltages.… The active electrode material plays an important role in increasing energy densities. For instance, carbonaceous materials like graphene and CNT, pseudo capacitance materials including metal oxides/hydroxides, and conductive polymers have been reported as high capacitance materials. However, those materials struggle with about process abilities, limiting of electrolyte adoption, charging/discharging properties, minimizing high cost and checking suitability for commercial production lines. Such boundaries with electrode materials motivate the development of electrolyte with high operating voltages for high energy densities. Because the operating voltages for SCs depends on the electrochemical stability window of the electrolyte.—Ahn et al.
The Augmented Optics technology was adapted from the principles used to make soft contact lenses, which Dr. Donald Highgate (of Augmented Optics, and an alumnus of the University of Surrey) developed following his postgraduate studies at Surrey 40 years ago.
The work was conducted by researchers at the University of Surrey’s Department of Chemistry where the project was initiated by Dr. Highgate. The research team was co-led by the Principal Investigators Dr. Ian Hamerton and Dr. Brendan Howlin. Dr. Hamerton continues to collaborate on the project in his new post at the University of Bristol, where the electrochemical testing to trial the research findings was carried out by fellow University of Bristol academic David Fermin, Professor of Electrochemistry in the School of Chemistry.
The test results from the new polymers suggest that extremely high energy density supercapacitors could be constructed in the very new future. We are now actively seeking commercial partners in order to supply our polymers and offer assistance to build these ultra high energy density storage devices.—Jim Heathcote, Chief Executive of both Augmented Optics Ltd. and Supercapacitor Materials Ltd.
Yong-keon Ahn, Bokyung Kim, Jieun Ko, Duck-Jea You, Zhenxing Yin, Hyunjin Kim, Dalwoo Shin, Sanghun Cho, Jeeyoung Yoo and Youn Sang Kim (2016) “All solid state flexible supercapacitors operating at 4 V with a cross-linked polymer–ionic liquid electrolyte” J. Mater. Chem. A, 4, 4386-4391 doi: 10.1039/C6TA00643D
Nerea Casado, Guiomar Hernández, Haritz Sardon, David Mecerreyes (2016) “Current trends in redox polymers for energy and medicine,” Progress in Polymer Science, Volume 52, Pages 107-135 doi: 10.1016/j.progpolymsci.2015.08.003