Interfacial characterization of hybrid solid-liquid electrolytes for Li-metal anode batteries

A successful implementation of lithium metal is required to meet the volumetric and gravimetric energy density requirements of portable electronics and electric vehicles of the future. The SOLBAT project has made a good progress in understanding the causes of dendrite formation and propagation at the Li-metal|SE interface. At the cathode, volume changes of active particles during charge/discharge make retention of intimate contact within the SE a significant problem. Currently, none of the identified SE candidates have the necessary combination of electrochemical stability, ionic conductivity and mechanical properties to address this issue. A hybrid solid-liquid electrolyte (HSE) cell in which a solid-protected anode is combined with a conventional liquid-filled porous cathode would represent a more readily implementable route to the practical implementation of metal anode batteries. A HE, introduces a new solid/liquid interface, poorly investigated in the literature but often associated with high impedances.

In this project, the student will investigate the solid electrolyte-liquid electrolyte interface as a function of charge state, cycling, current density, temperature and pressure, using a range of techniques including electrochemical impedance spectroscopy (3 and 4 electrodes), Raman, AFM, XPS, morphology studies by FIB/plasma-SEM, sample thinning and TEM-EDX and contact angle measurements. We will prioritize solid-electrolytes with proven stability in contact with Li-metal, i.e. Garnet LLZO and explore the effect of doping, grain size and surface roughness/morphology on the interfacial impedance. Strategies to mitigate high impedances, e.g. surface treatments and coatings will be investigated.

Utilise characterisation methods including XRD, SEM with EDX and EBSD, XPS, AFM and SEM assisted nanoindentation to characterise the microstructure of electroplated lithium in cell conditions and tie this to the resultant cycling/failure behaviour, with particular focus on the mechanical properties. Establish an understanding of the changes in microstructure with changing electrochemical conditions, and the resultant changes in performance.

EPSRC research area Theme: Energy