Operando Neutron Imaging of Lithium Flux and Gradient Cathode Design for Enhanced Kinetics in High-Loading...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• All-solid-state lithium-sulfur batteries (ASSLSBs) offer high energy density and safety but face challenges with slow redox kinetics and limited sulfur utilization.
• Sluggish Li+ transport and uneven Li+ distribution in cathodes hinder efficient sulfur conversion, especially in high-mass-loading ASSLSBs.

Purpose of the Study:

• To investigate the impact of Li+ transport kinetics on sulfur conversion in ASSLSBs.
• To design and validate gradient cathode architectures for optimizing Li+ flux and ionic conductivity.
• To enhance sulfur utilization and electrochemical performance in high-mass-loading ASSLSBs.

Main Methods:

• Operando neutron imaging was employed to visualize Li+ transport dynamics within the cathode during operation.
• Gradient cathode architectures with varied catholyte concentrations (three- and five-layer designs) were fabricated.
• Electrochemical performance, including rate capability and electrode polarization, was evaluated at high sulfur mass loadings.

Main Results:

• Operando neutron imaging revealed sluggish Li+ transport as a key limitation in traditional ASSLSB cathodes.
• The three-layer gradient cathode design significantly improved Li+ mobility and promoted uniform redox reactions.
• Superior rate performance and reduced polarization were achieved with gradient cathodes at sulfur loadings up to 6.0 mg cm-2.
• A five-layer gradient cathode demonstrated a substantial capacity increase to 1232 mAh g-1 at 7.5 mg cm-2 sulfur loading.

Conclusions:

• Gradient cathode architectures effectively address Li+ transport limitations in ASSLSBs.
• Optimized Li+ flux and ionic conductivity are crucial for high sulfur utilization and performance.
• This design strategy shows significant potential for developing practical, high-energy-density ASSLSBs.