Dual-salt reinforced polyacrylonitrile-based composite solid electrolyte for stable lithium metal batteries

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Science

Background:

• Composite solid electrolytes (CSEs) offer safety and manufacturing advantages for solid-state lithium batteries.
• Current CSEs face challenges with low ionic conductivity and poor interfacial compatibility, limiting their practical use.

Purpose of the Study:

• To improve Li+ conduction and interfacial compatibility in polyacrylonitrile-based CSEs.
• To investigate the effect of incorporating dual salts, Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and Lithium bis(oxalate)borate (LiBOB), on CSE performance.

Main Methods:

• Synthesized polyacrylonitrile-based CSEs with varying molar ratios of LiTFSI/LiBOB dual salts.
• Optimized the CSE composition (F/B-1:3) for enhanced ionic conductivity and Li-ion transference.
• Characterized the electrolyte-electrode interface and evaluated the performance of Li metal symmetrical cells and Li|NCM811 cells.

Main Results:

• The optimized F/B-1:3 CSE achieved high ionic conductivity (4.11 × 10⁻⁴ S cm⁻¹ at 30°C) and a Li-ion transference number of 0.68.
• The dual salts promoted the formation of a stable solid electrolyte interface (SEI) layer (LiF/Li₃N/B-O), enabling uniform Li deposition.
• Li|F/B-1:3|Li symmetrical cells demonstrated over 1600 hours of stable cycling, and Li|F/B-1:3|NCM811 cells retained 86.5% capacity after 200 cycles.

Conclusions:

• Incorporating LiTFSI/LiBOB dual salts effectively enhances ionic conductivity and interfacial compatibility in polyacrylonitrile-based CSEs.
• The developed CSE shows excellent electrochemical stability and potential for high-performance, safe solid-state lithium batteries.