Investigating electrolyte and charge rate effects on the sodiation of hard carbon A combined SAXS and electrochemical study on sodium-ion batteries
Typ
Examensarbete för masterexamen
Master's Thesis
Master's Thesis
Program
Physics, MPPHS, MSc
Publicerad
2024
Författare
Drevander, Isak
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
The interest in sodium-ion batteries has exponentially increased in the past 15 years.
One of the challenges in developing this technology has been in finding suitable an ode materials. As of today the most promising candidate is hard carbon. The
material is often defined as a non-graphitizable form of carbon that lacks long-range
order, and is made up of twisted and disarranged sheets of graphene. Due to the
complex amorphous structure, which can vary depending on the synthesis process,
there is currently no consensus regarding the sodium storage mechanism in the ma terial. By achieving a better understanding of this process, the nanoscale structure
of hard carbon anodes could be engineered to enhance its storage capabilities.
In this study, the sodiation process in hard carbon anodes was studied using small and wide-angle X-ray scattering along with electrochemical characterization tech niques. Two charge rates (C/5 and C/10) and two electrolytes (one ester-based and
one ether-based) have been compared to investigate possible variations in sodium
storage mechanisms. In all configurations, the scattering results show signatures
of pore filling occurring during the whole sodiation process while signatures from
intercalation appears first at higher degrees of sodiation. This suggests that pore
filling takes place during the sloping region of the voltage profile, while the two
mechanisms occur simultaneously in the plateau region. The pore filling mechanism
was less dominant when using a higher charge rate, and a higher capacity was re tained in batteries using an ether-based electrolyte compared with an ester-based
electrolyte, despite similar pore filling contributions.
Beskrivning
Ämne/nyckelord
Sodium-ion batteries, hard carbon, SAXS, sodiation, charge rate, elec trolyte, diglyme, EC:PC