Understanding Rate and Capacity Limitations in Li-S Batteries Based on Solid-State Sulfur Conversion in Confinement
Ayca Senol Gungor1, Jean-Marc von Mentlen1, Jean G A Ruthes2,3
1Department of Information Technology and Electrical Engineering, ETH Zürich, Gloriastrasse 35, 8092 Zürich, Switzerland.
ACS Applied Materials & Interfaces
|November 29, 2024
Summary
High cycle life lithium-sulfur (Li-S) batteries utilize sulfur-infiltrated nanoporous carbon cathodes. Understanding capacity limitations reveals charge transfer and cathode-electrolyte interphase structure are key for improved performance.
Area of Science:
- Materials Science
- Electrochemistry
- Energy Storage
Background:
- Lithium-sulfur (Li-S) batteries offer high theoretical energy density but suffer from limited cycle life and capacity fade.
- Protective cathode-electrolyte interphase (CEI) formation in sulfur-infiltrated nanoporous carbon cathodes improves cycle life by preventing polysulfide dissolution.
Purpose of the Study:
- To investigate the factors limiting capacity and rate performance in Li-S batteries with nanoporous carbon cathodes.
- To elucidate the role of CEI formation and sulfur conversion mechanisms within the nanopores.
Main Methods:
- Operando small-angle neutron scattering (SANS) and X-ray diffraction (XRD) to observe structural changes during cycling.
- Electrochemical impedance spectroscopy and galvanostatic charge/discharge to assess performance limitations.
- Utilized two types of nanoporous carbons with varying pore sizes.
Main Results:
- Operando SANS and XRD confirmed CEI formation and solid-state conversion of sulfur to lithium sulfide (Li2S) within the nanopores.
- Electrochemical data indicated that charge transfer at active material interfaces and the CEI/active material nanostructure are critical for capacity and rate performance.
- Performance was correlated with pore size and CEI characteristics.
Conclusions:
- Charge transfer kinetics and the nanostructure of the cathode-electrolyte interphase within nanopores are primary limitations for Li-S battery performance.
- Strategies focusing on optimizing these factors can enhance sulfur loading, sulfur utilization, rate capability, and overall cycle life.
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