Fluoride ion shuttle batteries with DFT calculations With rising energy demand considerable attempts have been made to produce environmentally friendly, high-energy density: Energy Science Project Proposal Thesis, TCD, Ireland

Fluoride ion shuttle batteries with DFT calculations

Project Description

With rising energy demand considerable attempts have been made to produce environmentally friendly, high-energy density, and low-cost rechargeable battery systems as an alternative energy storage solution. Renewable energy systems as of today are intermittent in nature i.e. energy from solar can only be harnessed during the day, wind during high winds etc.

Hence batteries are being designed to store energy during excess production phases and release them when the production drops. Lithium-ion batteries are widely used today due to their capacity which lies around 250-670 Wh/L which is 3 times higher than Ni-Cd or Ni-MH battery.

Although they have a lot of advantages Li-ion batteries have a lot of drawbacks such as its limited capacity, energy density, transportation and ageing. Therefore, this project focuses on researching fluoride ion shuttle batteries as a probable future replacement for Li-ion batteries.

The reversible cycling behaviour of a new battery system based on a metal fluoride electrode material along with Ba doped LaF3 (La1−xBaxF3−x) as a solid-state electrolyte was found to operate at high temperatures. Fluoride anions (F) are used as charge transfer ions between the two electrodes in this battery arrangement.

A high voltage electrochemical cell can be constructed by selecting an acceptable pair of electrodes consisting of metal fluoride MFx as the cathode and metal M′ as the anode, as well as a fluoride-containing electrolyte.

Furthermore, more than one F anion can react with bivalent or trivalent metals at the same time, allowing for the transfer of more than one electron per metal atom. As a result, fluoride ion batteries have the potential to produce high energy densities of up to 5000 Wh L-1 . The reversible conversion reactions at the electrodes based on the F− shuttle are as follows:

Focus of the Project:

The biggest challenge in fluoride ion battery development is finding an electrolyte that would be suited for use at room temperatures. Fluoride ions show a high mobility in the solid state so solid state electrolytes are much more preferred than liquid electrolyte because they are more safe.

The biggest advantage of fluoride ion shuttle battery would be the huge increase in capacity over Li-ion battery and less frequent charging needed which means longer usage. To do this we first need to understand the lanthanum fluoride crystal characteristics in order to figure out the doping agents suitable for the reaction.

The aim of this research project would be to understand the basic factors controlling doping and defect formation and the underlying diffusion process with the LaF3. The following chart shows the timeline for the project as per the steps

Expected Outcomes:

1) A better understanding of crystal structures, defects, diffusion profiles and doping.
2) An experience of working with Linux and high-performance computing for calculations.
3) A deeper understanding of vacancies in unit cells, bonding-antibonding and quantum mechanics.