Advanced and multiscale characterisation of solid state batteries
Résumé
All-solid-state batteries have been presented as the ideal solution to address i) the safety limitations of conventional Li-ion batteries and ii) the problem of insufficient energy densities if coupled to Li metal. To date, two types of solid Li-ion electrolytes have been mainly studied, namely, sulfur-based, and ceramic-based materials. As they are easy to process and they offer a high lithium-ion conductivity in the range of 1-20 mS/cm, sulfide-based electrolytes are therefore regarded as suitable candidates to be used in lithium all-solid-state batteries.To date, many aspects regarding their chemical and mechanical issues remain unsolved especially during electrochemical activities. If the electrode engineering i.e. composite electrode (mixture of electroactive material, conductive agent and solid electrolyte) is under intense investigation, the role of the solid electrolyte is so far poorly investigated. As an example, sintering (even cold sintering) process is a key parameter that controls the lifetime of the batteries, the rate capability etc. If it is not properly performed, the Li-ion conduction will not be optimal which could create kinetics problem. If voids are present in the solid electrolyte pellet, then during stress/strain, the voids could lead to fracture, hindering the ionic conductivity and lowering the electrochemical performance during cycling.In this work, we are proposing an in depth (operando and postmortem) multiscale investigation of the electrolyte “shaping” and its consequence on the electrochemical activity. We correlate information from bulk to surface analysis using electrochemical (EIS, CV, etc.) X-rays (XRD, XAS, micro and nano-XRT, FIB-SEM, etc.) and X-ray/neutron-based diffraction techniques revealing the relationship between shaping, structure, morphology and electrochemical performance. The results obtained here should serve as a preliminary basis to develop better solid-state batteries using sulfide-based electrolyte.