Investigating the Solid Electrolyte Interface (SEI) of Sodium Ion Batteries

Lead Research Organisation: University of Cambridge
Department Name: Chemistry


Lithium ion batteries are of fundamental importance to the modern world because of their use in many devices, such as portable electronics. Looking to the future, storing energy is set to become increasingly important for other large-scale applications including electric vehicles and grid storage of energy generated by renewable energy sources, such as wind and solar. However, lithium reserves are limited to only a few countries, and the increased demand for lithium causes a commensurate increase in expense. Therefore, the development of cheap alternatives to lithium ion batteries is highly desirable. As sodium has a similar chemistry to lithium and is readily available (sodium is approximately 1200 times more abundant than lithium and is more evenly distributed in the earth's landmass), there has been an increased interest in developing sodium-ion batteries.

Within sodium ion batteries, sodium ions are transferred from a cathode to an anode through an electrolyte during charging and then from the anode to the cathode during discharging. As the battery is cycled, a solid layer builds up at the interface between the electrolyte and the electrodes. This layer is called the solid electrolyte interphase (SEI) and it is formed mainly from decomposition products of the electrolyte. The SEI is of crucial importance to the battery as it protects the anode by inhibiting the transfer of electrons from the anode to the electrolyte, whilst also allowing sodium ions to transfer from the electrolyte to the anode. The ideal SEI is therefore both an ionic conductor and an electrical insulator.

To improve battery technologies, we must provide a better understanding of the SEI. This project sets out to characterise chemical composition and morphology of the SEI formed in sodium ion batteries by using a variety of techniques including solid-state NMR, X-ray photoelectron spectroscopy, and Raman spectroscopy.


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Au H (2020) A revised mechanistic model for sodium insertion in hard carbons in Energy & Environmental Science

Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/R512461/1 01/10/2017 30/09/2022
1944642 Studentship EP/R512461/1 01/10/2017 30/12/2021 Thomas Henry Smith
Description Lithium-ion batteries (LIBs) are currently the state-of-the-art energy storage system and are consequently ubiquitous in the modern world. Looking to the future, energy storage is set to become increasingly important, especially in the fields of electric vechicles and grid storage of renewable energy. This increased demand, has led to a significant increase in the price of lithium, when this is combined with the enviromental concerns about the production of lithium and cobalt for the cathodes, it has become desireable to research alternatives to LIBs.

One alterantive is sodium-ion batteries (SIBs), as sodium is much more abudant than lithium whilst having a similar chemistry to lithium. Despite the similarities, the chemistries of these systems are not the same and how sodium ions interact with (both ordered and disordered) carbon materials used as anodes is not fully understood We have therefore used solid state nuclear magnetic resonance spectroscopy (SSNMR) to probe these interactions
Exploitation Route This more detailed understanding of how sodium ions interact with carbon anodes, allows of the design of anodes that can have more desireable properties, such as higher capacity.
Sectors Chemicals,Energy

Description Studying Sodium Intercalation in to hard carbon - Magda Titirici group, Imperial College London 
Organisation Imperial College London
Country United Kingdom 
Sector Academic/University 
PI Contribution We performed solid state nuclear magnetic resonance (ss-NMR) studies on various hard carbons
Collaborator Contribution Our NMR results were combined with small angle X-ray scattering (SAXS) and XPS to provide a model of sodium intercalation into hard carbon
Impact Paper has been submitted, not yet published
Start Year 2019
Description Presentation at Shell Technology Centre, Amsterdam 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact I gave a brief summary of my work at Shell Technology Centre, Amsterdam (as Shell partly fund my iCASE PhD), we are now discussing the opportunity for me to return to Shell for an internship
Year(s) Of Engagement Activity 2020