Postdoc: Understanding the nature of degradations while using alloying anodes for Na-ion batteries (M/F)

Job Description

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.

Activity

This study will focus on electrode coating, electrolyte preparation, cell assembly, and aging, using various physicochemical and electrochemical techniques. The interface chemistry and its stability will be investigated using electrochemical and spectroscopic techniques, such as cyclic voltammetry (in oxidation and reduction), galvanostatic cycling, resistance variation measurement during cycling, XPS, XAS, etc. Pressure variations and the evolution of gaseous products during interface formation and cycling will be monitored by pressure and mass spectrometry analyses. A multidisciplinary background, combining materials science and electrochemistry, would be an asset.

Your Profil

Skills

A PhD is required. A multidisciplinary background, including knowledge of materials science and electrochemistry, would be desirable, as would excellent English skills. Candidates with experience in SAXS/WAXS analysis and large dataset processing will be given preference.

Your Work Environment

The majority of the work will take place in Paris (between CSE and Phenix), and part of the time will be spent at SyMMES (Grenoble) during the off-site periods.

Constraints and risks

Nil

Compensation and benefits

Compensation

Between €3081 and €4654 gross per month depending on experience (gross monthly salary)

Annual leave and RTT

44 jours

Remote Working practice and compensation

Pratique et indemnisation du TT

Transport

Prise en charge à 75% du coût et forfait mobilité durable jusqu’à 300€

About the offer

About the CNRS

The CNRS is a major player in fundamental research on a global scale. The CNRS is the only French organization active in all scientific fields. Its unique position as a multi-specialist allows it to bring together different disciplines to address the most important challenges of the contemporary world, in connection with the actors of change.

CNRS

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