Mechano-electrochemical coupling of ionic conductive glasses

Context:

Renewable energies, such as wind and solar power, are being developed to achieve the European Union’s goal of climate neutrality by 2050 (reducing CO₂ emissions). This is the EU’s long-term strategy that culminated in the Paris Agreement, signed in early 2020. However, to fully exploit the potential of green energy, efficient storage solutions are essential. Electrochemical storage (batteries), and in particular its latest developments with lithium-ion and post-lithium-ion batteries, offers promising solutions. A battery cell typically consists of a cathode, an electrolyte, a separator, and an anode. Liquid electrolytes, especially those containing lithium, are subject to dendrite growth of the latter, which causes internal short circuits and, consequently, safety risks related to the presence of a flammable organic liquid. In contrast, an all-solid-state battery using a solid electrolyte would allow for a significant improvement in achieving high energy density because the cell does not require a separator and/or a large electrolyte layer. While all-solid-state batteries are very promising, their development faces numerous challenges, such as lower ionic conductivity, higher manufacturing costs, and reduced performance during use. This necessitates electrolytes with favorable electrochemical and mechanical properties. In this context, glass, the amorphous material with glass transition temperature (T_g), is a good candidate because (i) its cost is relatively low and (ii) the choice of compositions to improve its electrochemical and mechanical characteristics is very flexible.

PhD topic:

This thesis will focus on the study of the mechanical and electrochemical properties of ionic conductive glasses, linking their properties to their microstructures. The study will concentrate particularly on (1) the synthesis of glass materials, (2) the measurement of resistance to crack initiation and propagation, and (3) the measurement of the ionic and electronic conductivity of the synthesized glasses. The objective is to understand the damage mechanisms of glasses under electrical load and the effect of mechanical loading (tension/compression) on the ionic conductivity of the glasses. These two phenomena are important and coupled because, in an all-solid-state battery, a force must be applied to ensure proper contact between the two electrodes and the solid electrolyte.

The first step will be to define glasses with an ionic conductivity comparable to that of the liquid electrolyte (10⁻⁴ S·cm⁻¹). Oxide glasses with different compositions will be fabricated at GeM. Glasses with favorable atomic structures and high ionic conductivities, such as borate, phosphate, and aluminate systems, will be studied. These different glasses are chosen for investigation because they possess diverse structures and potential for improving electrochemical properties and approaching those of liquid electrolytes.

The experimental characterization part will be devoted to mechanical tests which will be carried out in order to quantify: the elastic moduli, the fracture toughness (K_Ic) and the Crack Resistance (CR) of the material, and finally the crack propagation under electrical charge/discharge. Various analytical techniques available at the laboratory (PREED platform (Centrale Nantes) and MAPE platform (Saint-Nazaire University Institute of Technology)) will allow us to understand the damage mechanisms under stresses:

- micro- and nano-indentation tests and Single-Edge Precracked Beam (SEPB)

- digital image correlation techniques necessary for evaluating toughness and propagation speeds

- complementary micro-mechanical tests under a scanning electron microscope (SEM) to observe damage and ion diffusion in situ at the micro/nanoscale.

Position details

• Salary: about 2300€ gross per month
• Contract duration: 36 months
• Start date: between 01/09/2026 and 01/12/2026
• Location: Ecole Centrale de Nantes, Nantes, France
• Application deadline: 08/04/2026

https://amethis.doctorat.org/amethis-client/prd/consulter/offre/2817

Founded in 2004, GeM is a Joint Research Unit of Nantes Universit´e, Centrale Nantes, and the CNRS (UMR-6183). It brings together all the expertise in civil engineering, materials mechanics and processes, and modelling and simulation in structural mechanics from the Nantes Saint-Nazaire metropolitan area within a single laboratory.

Science et Ingénierie des Matériaux, Mécanique des Matériaux –Chemical and/or Mechanical Engineering, Material Sciences and Engineering.