A Polymorphic FeS₂ Cathode Enabled by Copper Current Collector Induced Displacement Redox Mechanism

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Developing high-performance lithium-ion batteries is crucial for energy storage solutions.
• Iron disulfide (FeS2) is a promising cathode material due to its high theoretical capacity.
• Polysulfide shuttle effect limits the electrochemical performance of Li-FeS2 batteries.

Purpose of the Study:

• To fabricate a composite of pyrite (P-FeS2) and marcasite (M-FeS2) for high-performance Li-FeS2 batteries.
• To investigate the role of M-FeS2 in enabling a four-electron reduction.
• To address the shuttle effect and improve battery performance using a copper current collector.

Main Methods:

• Fabrication of a P-FeS2/M-FeS2 composite.
• Electrochemical characterizations (capacity, rate capability, cycling stability).
• Microscopic and spectroscopic analyses.
• Investigation of reaction mechanisms with copper current collectors.

Main Results:

• The P-FeS2/M-FeS2 composite achieved a specific capacity of 894 mAh/g and specific energy over 1300 Wh/kg.
• Copper current collectors suppressed the shuttle effect by immobilizing lithium polysulfides.
• The modified electrode exhibited superior rate capability (730 mAh/g at 2 A/g) and long cycle life (89.7% retention after 3200 cycles).

Conclusions:

• The composite of pyrite and marcasite FeS2 enables efficient four-electron reduction for high-capacity lithium storage.
• Copper current collectors are effective in mitigating polysulfide shuttling through a displacement reaction mechanism.
• This work demonstrates a viable strategy for high-performance metal chalcogenide electrodes in batteries.