Carbonyls Mediated Dual-Function Enables High-Performance Carbon Anodes in Ester-based Electrolyte.

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Constructing a stable solid electrolyte interphase (SEI) is crucial for high-performance hard carbon anodes in ester electrolytes.
• Existing methods for SEI formation in ester electrolytes are limited, hindering anode stability and capacity.

Purpose of the Study:

• To develop a novel surface modification strategy for hard carbon anodes to form an "ether SEI"-like layer in ester electrolytes.
• To enhance the electrochemical performance, particularly capacity and cycling stability, of hard carbon anodes.

Main Methods:

• Surface reconstruction of hard carbon by grafting caffeic acid to introduce carbonyl (C═O) moieties.
• Characterization using various techniques to analyze SEI composition and interfacial properties.
• Electrochemical testing to evaluate capacity, rate performance, and cycling stability.

Main Results:

• The introduced C═O moieties preferentially adsorb PF₆^- salt over electrolyte solvents, promoting stable inorganic SEI formation.
• C═O moieties facilitate reversible K-ion adsorption, contributing to high capacitive performance.
• The optimized hard carbon anode achieved a reversible capacity of 462.7 mAh g^-1 at 0.1 A g^-1 and maintained 321.8 mAh g^-1 at 2 A g^-1.
• A cycle life exceeding 2000 cycles was demonstrated at 2 A g^-1 in ester-based electrolytes.

Conclusions:

• Grafting caffeic acid onto hard carbon effectively creates an "ether SEI"-like layer in ester electrolytes.
• The C═O moieties enhance interfacial stability and surface properties, leading to superior electrochemical performance.
• This surface design approach offers a promising strategy for improving hard carbon anodes in potassium-ion batteries using ester electrolytes.