Robust Solid Electrolyte Interphases in Localized High Concentration Electrolytes Boosting Black Phosphorus Anode for...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Black phosphorus (BP) exhibits high theoretical capacity for potassium ion (K+) storage.
• However, BP anodes suffer from poor cycling stability and rapid capacity decay, limiting their practical application.
• Developing strategies to enhance the stability of BP anodes is crucial for advancing potassium-ion battery technology.

Purpose of the Study:

• To synthesize a stable black phosphorus-graphite (BP/G) composite anode for potassium-ion batteries.
• To investigate the use of a localized high concentration electrolyte (LHCE) to improve the electrochemical performance and cycling stability of BP anodes.
• To elucidate the mechanism by which LHCEs enhance the solid electrolyte interphase (SEI) formation and stability.

Main Methods:

• Synthesis of an 80 wt % BP/G composite.
• Preparation of a localized high concentration electrolyte (LHCE) using potassium bis(fluorosulfonyl)imide in trimethyl phosphate with a fluorinated ether diluent.
• Electrochemical characterization including cyclic voltammetry, galvanostatic cycling, and rate capability tests.
• Analysis of the solid electrolyte interphase (SEI) composition and structure.

Main Results:

• The BP/G composite anode stabilized by LHCE demonstrated significantly improved reversibility and capacity retention.
• The LHCE facilitated the formation of an inorganic-rich SEI layer, effectively passivating the BP electrode.
• The fluorinated ether diluent in the LHCE enhanced ionic conductivity and homogenized SEI elemental distribution, improving its mechanical robustness and accommodating volume changes.
• The resulting electrode exhibited excellent cyclic performance and attractive rate capability.

Conclusions:

• Localized high concentration electrolytes (LHCEs) are effective in stabilizing high-capacity black phosphorus anodes for potassium-ion batteries.
• The inorganic-rich and mechanically robust SEI formed under LHCE conditions is key to preventing electrode degradation.
• This work highlights the potential of LHCEs for developing advanced energy storage devices utilizing high-capacity alloy anodes.