Novel Techniques and Electrolytes for Energy Storage Devices

Sodium ion batteries (SIBs) may offer a cheaper and more sustainable alternative to lithium batteries given the significantly higher natural abundance of sodium than lithium. The SIB electrolyte must transport ions efficiently to achieve good battery performance. Here, a range of new sodium borate and aluminate electrolyte salts provided by collaborators were investigated for their suitability. Several techniques were applied to measure key physical properties of the novel sodium electrolytes, including electrochemical impedance spectroscopy, pulsed field gradient nuclear magnetic resonance and viscometry. Collectively, these results have been used to quantitatively identify promising candidates for applications in SIBs. Supercapacitors are high power energy storage devices that store energy by the formation of double layers at the electrode surfaces. However, the molecular structure of the double layer is poorly understood. Here, neutron reflectometry (NR) and attenuated total reflection infrared (ATR-IR) spectroscopy were developed to study the supercapacitor double layer in situ. A custom cell was designed to study the supercapacitor electrode-electrolyte interface using NR in situ. Several electrode materials were investigated to determine their structure and suitability for studying the double layer. Significant effort was spent to craft a ‘realistic’ graphene electrode. Despite employing a number of state-of-the-art approaches from the literature, data collected here suggested that none of these could remove a thin layer of residual polymer on the graphene surface, used for transfer. This raises concerns for other graphene studies less able to identify the polymer than NR. Due to limited availability of neutron beamtime, we took the opportunity to develop a complementary custom cell for in situ ATR-IR spectroscopy. Careful selection of candidate ATR crystals suggested germanium could be optimal for use as an electrode to study the double layer in situ. However, unexpectedly the germanium was found to undergo chemical changes to the crystal surface over time and a particularly complex optical response was repeatedly observed with applied voltage, which complicated interpretation.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2024

Author dc:creator

• Smith, Holly

Advisors dc:contributor.advisor

• Clarke, Stuart
• Grey, Clare

• Batteries
• Chemistry
• Electrochemistry
• Energy storage
• Supercapacitors
• Surface science

Licence

• https://www.repository.cam.ac.uk/bitstreams/d6c6ffe1-985d-445e-942a-a68c60d1bf58/download
• http://purl.org/NET/rdflicense/allrightsreserved

Language dc:language

eng

Author Identifier

0000-0002-3389-6259

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/390766