Simple cathode design for Li–S batteries: cell performance and mechanistic insights by in operando X-ray diffraction

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Rechargeable batteries are crucial for electric vehicles and grid storage.
• Elemental sulfur offers the highest theoretical specific capacity among cathode materials.

Purpose of the Study:

• To evaluate the electrochemical performance of simple sulfur cathodes.
• To identify limitations in lithium-sulfur (Li–S) cell performance.

Main Methods:

• Fabrication and testing of sulfur cathodes in coin and pouch cells.
• Electrochemical performance analysis at room and elevated temperatures.
• In operando X-ray diffraction (XRD) to study sulfur phase evolution.

Main Results:

• Specific capacities of 1000 mA h g−1 achieved over 60 cycles at room temperature.
• Poor cyclability observed at temperatures above 40 °C.
• Discharge identified as the kinetically rate-limiting step.
• Significant sulfur loss during the formation cycle and electrolyte decomposition on the lithium anode.
• Li2S formation and β-sulfur phase observed during cycling via in operando XRD.

Conclusions:

• Simple sulfur cathodes demonstrate good capacity at room temperature but face challenges with temperature stability and cycling.
• Electrolyte decomposition and sulfur loss are critical issues for Li–S cell longevity.
• Understanding sulfur phase transformations is key to improving Li–S battery performance.