Regulating Electrolyte Solvation Structure via Trace LiPF₆ for High-Performance Sodium-Ion Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Sodium-ion batteries (SIBs) are a promising alternative to lithium-ion batteries.
• Challenges in SIBs include slow ion migration and unstable interfaces due to sodium ion properties.
• These issues limit battery cycle life and fast-charging.

Purpose of the Study:

• To develop a solvation regulation strategy to overcome SIB limitations.
• To enhance ionic conductivity and interfacial stability in SIB electrolytes.
• To improve the electrochemical performance and cycle life of SIBs.

Main Methods:

• Utilized a trace amount of lithium hexafluorophosphate (LiPF6) as an additive in a sodium hexafluorophosphate (NaPF6) electrolyte.
• Investigated the formation of Li+-Na+ composite solvation structures.
• Evaluated battery performance using Na3Fe2(PO4)P2O7 (NFPP) and hard carbon (HC) electrodes in coin cells and pouch cells.

Main Results:

• The LiPF6 additive induced unique Li+-Na+ composite solvation structures, enhancing ionic conductivity and interfacial stability.
• NFPP||Na batteries showed over 98% capacity retention after 3000 cycles at 10 C.
• HC||Na batteries achieved 86.83% capacity retention after 400 cycles at 1.0 A/g.
• NFPP||HC pouch cells demonstrated exceptional performance at 3 C.

Conclusions:

• The developed solvation strategy effectively improves the electrochemical performance of SIBs.
• The LiPF6 additive offers a promising approach for designing high-performance SIB electrolytes.
• This research provides a pathway for enhancing both high-rate capability and cycle life in sodium-ion batteries.