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H2020Individual fellowship2020–2022

NanoEvolution · Nanoscale phase evolution in lithium-sulfur batteries

Horizon 2020 — Marie Skłodowska-Curie Actions

Duration
2020-07-01 → 2022-06-30
EU contribution
€191,149
Participants
1
Scheme
MSCA-IF

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Results in brief

Nanoscale phase evolution in lithium-sulfur batteries

Reducing global greenhouse gas emissions is amongst the most pressing societal and technological challenges of our times. Batteries will be key in our efforts to reduce CO2 emissions but require major progress in sustainability, cost, and energy density. Practical Li-sulfur (Li-S) batteries would be game-changers in many respects: a theoretical capacity amongst the highest of all batteries paired with the low cost and sustainability of sulfur. Years of research left a central question in Li-S batteries open: what is the very fundamental mechanism to reversibly convert sulfur (S) into lithium sulfide (Li2S) and back? Particularly, how is insulating, insoluble Li2S electrodeposited and stripped? As the battery discharges, S is reduced into soluble polysulfides (Li2Sn), which eventually need to be reduced to solid, insulating, and insoluble Li2S. Only converting large amounts of S into Li2S allows to fully exploit the outstanding capacity of Li-S electrochemistry. Notably, while reducing S8 via various polysulfides to Li2S2 affords half of the capacity, converting Li2S2 to Li2S affords the other half, highlighting the importance of this step alone. The MSC project NanoEvolution aimed at understanding the fundamentals of the solid-liquid-solid S/Li2S conversion and the relevant structure-property relationships by developing structure-sensitive operando scattering methods, combined with stochastic modelling and electron microscopy.

Data: CORDIS, © European Union

Project objective

Lithium-sulfur (Li-S) batteries are considered a strategic candidate to achieve both significantly higher energy storage and better sustainability than current Lithium-ion batteries. They operate by converting sulfur into lithium sulfide and back on discharge/charge. However, practically achieved energies are far from theoretical values due to difficulties to load sulfur in high areal and volume density in the porous carbon cathode and to fully use it electrochemically. Current experimental techniques are strong in aspects, but fail to combine the required coverage of length scales ranging from sub-nanometers to micrometers in the crucial real-time in situ fashion. NanoEvolution aims to i) identify nanoscale structure-transport-performance correlations, ii) understand capacity limitations and reaction mechanisms, and iii) derive design criteria for improved Li-S battery performance. To achieve these goals, structure-sensitive in situ scattering and imaging methods during electrochemically operating custom-built in situ Li-S cells will be implemented. Specifically, in situ small and wide angle X-ray scattering (SWAXS) will be established and synergistically combined with nanoscale phase evolution modelling for data analysis. In situ nanoscale X-ray tomography will be realized to achieve continuous structural sensitivity from (sub-)nanometer (SWAXS) to sub-micrometer scales (tomography). The novel combination of modelling and structure-sensitive in situ experiments allows real-time detection of the Li2S/sulfur morphology and location within the nanoporous carbon electrode during charge and discharge, at length scales so far not accessible to other methods. This allows to determine the final cause for capacity limitation (mass transport vs. charge transport), ii) elucidate the nature of the multiple-step sulfur reduction (oxidation) reaction, and iii) derive design criteria for improved sulfur loading, capacity utilization, and power densities.

Original text from CORDIS.

Participants

  • EIDGENOESSISCHE TECHNISCHE HOCHSCHULE ZUERICH · ZuerichCoordinatorSwitzerland

Links

Data: CORDIS, © European Union