Fluorinated Graphite (FG)-Modified Li-S Batteries with Superhigh Primary Specific Capacity and Improved Cycle...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Lithium-sulfur (Li-S) batteries offer high theoretical energy density and low cost.
• Key challenges include low sulfur utilization and polysulfide shuttle effect, leading to capacity fade.
• Improving cathode performance is crucial for practical Li-S battery applications.

Purpose of the Study:

• To introduce fluorinated graphite (FG) as a cathode additive in Li-S batteries.
• To investigate the impact of FG on sulfur utilization, polysulfide shuttle, and electrochemical performance.
• To enhance the energy density and cycle stability of Li-S batteries.

Main Methods:

• Incorporation of fluorinated graphite (FG) into the Li-S battery cathode.
• In situ formation of lithium fluoride (LiF) nanocrystals within the cathode structure.
• Electrochemical testing including specific capacity, cycle life, and rate capability measurements.

Main Results:

• FG addition led to in situ formation of LiF nanocrystals, increasing cathode porosity and polarity.
• Enhanced electrolyte infiltration and polysulfide adsorption were observed.
• A high initial specific capacity of 1602 mA h g^-1 was achieved.
• Reversible specific capacity of 650 mA h g^-1 at 0.5C after 300 cycles.
• Significantly improved rate capability, with 860 mA h g^-1 at 5C (367% higher than without FG).

Conclusions:

• Fluorinated graphite effectively mitigates the shuttle effect and improves sulfur utilization in Li-S batteries.
• The in situ generated LiF nanocrystals play a key role in enhancing electrochemical performance.
• This strategy offers a promising pathway for developing high-energy and stable Li-S batteries.