Multi-Electron Transfer Halide Cathode Materials Based on Intercalation-Conversion Reaction Towards All-Solid-State...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• All-solid-state lithium batteries (ASSLBs) promise enhanced safety and energy density compared to conventional lithium-ion batteries.
• Current ASSLBs are limited by low-capacity oxide cathode materials that rely on intercalation mechanisms and require significant catholyte content.
• Developing high-performance cathode materials is crucial for advancing ASSLB technology.

Purpose of the Study:

• To introduce novel halide cathode materials (Li_xFeX_x+2) as alternatives to conventional oxide cathodes in ASSLBs.
• To investigate the electrochemical performance and operating mechanism of these new halide materials.
• To demonstrate the potential for high energy density and improved safety in ASSLBs utilizing these advanced cathodes.

Main Methods:

• Synthesis and characterization of Li_xFeX_x+2 (X=Cl, Br) cathode materials.
• Electrochemical testing of catholyte-free ASSLBs incorporating LiFeCl₃ active material (95 wt%).
• Analysis of the intercalation-conversion coupling reaction mechanism, including the role of amorphous Fe formation.

Main Results:

• Li_xFeX_x+2 materials operate via a 3 mol e^- transfer intercalation-conversion coupling reaction, offering higher capacity than traditional oxides.
• Catholyte-free ASSLBs using 95 wt% LiFeCl₃ achieved a capacity of 446 mAh g^-1 and energy density of 912 Wh kg^-1.
• Amorphous Fe formed during conversion catalyzes the reverse reaction, enabling reversible intercalation-conversion and high cycling stability.

Conclusions:

• Halide cathode materials (Li_xFeX_x+2) represent a significant advancement for high-energy-density ASSLBs.
• The unique intercalation-conversion mechanism and catholyte-free design overcome limitations of oxide cathodes.
• These findings pave the way for next-generation safer and more powerful solid-state batteries.