Missions

The development of sodium-ion batteries (NIBs) as a complementary energy storage solution to the widely used lithium-ion batteries (LIBs) is gaining global attention and NIBs have already been commercialized for high-power applications. However, the maximum energy density achieved so far is approximately 120 Wh/kg (in cylindrical 18650 format) for Na3V2(PO4)2F3 (NVPF)|Hard Carbon (HC) cells and around 140-160 Wh/kg (in either 18650 or pouch format) for layered oxide|HC cells. To improve their competitiveness, the energy density of sodium-ion cells needs to be enhanced. One potential solution is to replace the current HC negative electrode with alloying anodes (e.g., Sn, Sb, Pb), which offer a capacity 2 to 4 times greater than the conventional HC electrode. However, cycling of alloying anodes has been exclusively demonstrated in electrolytes containing glyme as the solvent, which remains stable upon reduction, ensuring minimal interfacial reactivity at the negative electrode. Despite this, glyme-based electrolytes have lower oxidative stability compared to commercially used carbonate ester solvents, presenting challenges when paired with high-voltage positive electrodes. Our recent studies using NVPF/Sn-HC based Na-ion cells indicate that glyme electrolytes oxidize in the NVPF surface to form different byproducts that deteriorate the alloying anodes. Hence, our project aims to follow the structural degradation that happen in the alloying anodes due to the parasitic species, via SAXS/WAXS and spectroscopic analyses of the fresh and aged materials (ex-situ and operando when possible). The project involves CSE (UMR8260), Phenix- Sorbonne University and SyMMES (CEA, Grenoble). Candidates must have in-depth knowledge in the fields of electrochemistry, materials science, especially structural analyses and hands-on experience in Li/Na-ion cell assemblies. Candidates having experience in SAXS/WAXS will be preferred. A perfect command in English is required. Major amount of work will be in Paris (between CSE and Phenix) and part of time will be at SyMMES (Grenoble) during the beam time.

Activités

The study will focus on electrode coating, electrolyte preparation, cell assembly, ageing studies using different physical/chemical/ electrochemical techniques. The interface chemistry and its stability will be followed by electrochemical and spectroscopic techniques, such as, cyclic voltammetry (both on oxidation, reduction), galvanostatic cycling, change in resistance upon cycling, XPS, XAS etc. Pressure changes and gaseous product evolutions during interface formation and upon cycling will be followed by pressure analyses and mass spectrometry. A multi-disciplinary profile with notions of materials science and electrochemistry would be welcome.

Compétences

A candidate with phd degree is required. A multidisciplinary profile including knowledge of materials science and electrochemistry would be desirable, as would a mastery of English. Candidates with experience in SAXS/WAXS analyses and in the data treatment of large data set will be preferred.

Contexte de travail

Major amount of work will be in Paris (between CSE and Phenix) and part of time will be at SyMMES (Grenoble) during the beam time.

Contraintes et risques

Nil

Informations complémentaires

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