Operando Optical Imaging of Cathode Swelling Process Inside Lithium Primary Batteries: Comparative Studies between...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Fluorinated carbon (CF) is a high-capacity cathode material for lithium primary batteries.
• Nonuniform volume expansion during discharge limits the performance of CF cathodes.
• Understanding CF swelling mechanisms is crucial for optimizing battery performance.

Purpose of the Study:

• To investigate the volume evolution of different CF cathode structures during discharge.
• To quantify swelling ratios and correlate them with electrochemical lithiation mechanisms.
• To elucidate the factors influencing cathode swelling in Li/CF batteries.

Main Methods:

• Operando confocal microscopy was employed to visualize cathode thickness changes.
• Swelling ratios were quantified as a function of discharge depth.
• Single-particle Raman and photoluminescence spectroscopy were used to study lithiation mechanisms.

Main Results:

• Hard carbon-derived fluorinated carbon (FHC) showed a lower swelling ratio compared to fluorinated graphite (FG).
• FHC, with its disordered structure and pores, exhibited more homogeneous lithiation.
• FG displayed nonuniform lithium insertion via 'edge propagation' pathways, leading to greater swelling.

Conclusions:

• The study reveals distinct electrochemical mechanisms governing volume expansion in different CF structures.
• Homogeneous lithiation in FHC effectively mitigates cathode swelling.
• Findings provide insights for designing advanced CF cathodes with improved electrochemical stability and performance in Li/CF batteries.