About the project
The SOLBAT project makes up one of the Faraday Institution's 4 parallel 'Fast Start' projects. Started in March 2018 and recently extended until April 2023 it is a collaboration led by The University of Oxford, with four other university partners and three industrial partners, to break down the barriers that are preventing the progression to market of solid-state batteries, that should be lighter and safer, meaning cost savings and less reliance on cooling systems.
The ambition of this project is to demonstrate the feasibility of a solid state battery with performance superior to Li-ion in EV applications. With Oxford, university partners include the University of Liverpool, University of Sheffield, University of Warwick and University College London
We have identified the four major barriers facing all-solid-state batteries where a lack of fundamental understanding is blocking progress.
PLATING AND STRIPPING LI OR NA AT THE ALKALI METAL ANODE||SOLID ELECTROLYTE INTERFACE (WP1)
The rate of charge and discharge (current density) is limited to a value too low for practical applications (< 0.5 mAcm-2) due to the formation of alkali metal dendrites (fingers of alkali metal). We shall understand the origin and propagation of dendrites, experimentally and theoretically, including the effects of surface cracks, cavitation on stripping.
The new knowledge will be used to inform how to design anode/solid electrolyte interfaces to mitigate dendrites
CERAMIC-CERAMIC CONTACT AT THE SOLID ELECTROLYTE||CATHODE INTERFACE (WP2)
The cathode is a composite mixture of the active cathode material, the solid electrolyte and carbon. Volume changes of the active material as it expands and contracts on charge and discharge leads to loss of contact between the active material and the solid electrolyte, between the solid electrolyte particles themselves, and between the active material and carbon.
In short, the composite degrades mechanically leading to failure electrochemically, specifically to low current densities (rates of charge discharge), capacity fading and early cell death. We shall understand the factors that control wetting, contact and adhesion between the solid electrolyte and solid electrode particles as the latter expands and contracts on cycling.
DISCOVERY OF NEW SOLID ELECTROLYTES (WP3)
Two main classes of solid electrolyte exist currently, oxides and sulphides. Oxides do not deliver sufficient conductivity to sustain high currents through thick composite cathodes necessary for practical cells and sulphides are highly air sensitive making a practical use in cell manufacture extremely challenging.
In short there is a need to discover new solid electrolyte materials that combine high conductivity with chemical and electrochemical stability and the necessary mechanical properties.
INTEGRATION OF SOLID STATE ELECTROLYTES IN FULL CELL ARCHITECTURES (WP4)
It is essential all of our studies are carried out on the same set of materials and cells. We will prepare cells for the experimental studies to be carried out elsewhere in the project. This includes preparing dense ceramic disks/films of oxides and sulphides and forming these into symmetrical laboratory cells.
We will also form whole cells (alkali metal anode and intercalation cathode) in order to explore antagonistic effects between the two interfaces.
Finally we will investigate smart electrode design based on controlled porosity cathodes formed from sulphide solid electrolyte.