An Active Halide Catholyte Boosts the Extra Capacity for All-Solid-State Batteries.

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Solid electrolytes (SEs) are crucial for safer lithium batteries, replacing flammable liquid electrolytes.
• Current solid-state batteries face challenges with low energy density due to inactive SE additives in cathodes.
• Developing active SEs that contribute to capacity is key for high-performance solid-state devices.

Purpose of the Study:

• To introduce and characterize a novel halide solid electrolyte, Li3VCl6, as an active component in lithium batteries.
• To evaluate the electrochemical performance and ionic conductivity of Li3VCl6.
• To demonstrate the potential of Li3VCl6 to enhance energy density when integrated into composite cathodes.

Main Methods:

• Synthesis and characterization of the halide solid electrolyte Li3VCl6.
• Electrochemical testing including cyclic voltammetry and galvanostatic cycling to assess capacity and voltage.
• Ionic conductivity measurements under electrochemical cycling conditions.
• Composite cathode fabrication using Li3VCl6 with LiFePO4 for performance evaluation.

Main Results:

• Li3VCl6 exhibits good Li+ conductivity and a reversible capacity of ~80 mAh g-1 at 3V vs Li+/Li.
• The ionic conductivity of Li3VCl6 remains stable during lithiation/delithiation due to a solid-solution reaction mechanism.
• Composite cathodes with active Li3VCl6 achieved 217.1 mAh g-1 (LFP basis) and a ~50% increase in energy density.

Conclusions:

• Li3VCl6 functions as an active halide solid electrolyte, contributing to battery capacity.
• The use of active catholytes like Li3VCl6 significantly enhances energy density in solid-state lithium batteries.
• This approach offers a promising strategy for developing safer and higher-energy-density lithium battery technologies.