Ca²⁺-Based Dual-Carbon Batteries in Ternary Ionic Liquid Electrolytes

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Developing next-generation batteries requires exploring novel chemistries beyond lithium-ion.
• Calcium ion (Ca²⁺) batteries offer potential due to calcium's abundance and divalent nature.
• Dual-carbon batteries (DCBs) present an alternative architecture for high-performance energy storage.

Purpose of the Study:

• To propose and investigate Ca²⁺-based dual-carbon batteries (DCBs) utilizing graphite anode and cathode materials.
• To develop and optimize a ternary electrolyte for enhanced anodic stability and anion intercalation.
• To evaluate the electrochemical performance and cyclability of the constructed DCBs.

Main Methods:

• Fabrication of DCBs using mesocarbon microbeads (MCMB) as anode and KS6L graphite as cathode.
• Electrolyte formulation using a Ca²⁺-tetraglyme complex ([Ca:G₄]) in Pyr₁₄TFSI ionic liquid.
• Electrochemical characterization including cyclic voltammetry, galvanostatic charge/discharge, and long-term cycling tests.

Main Results:

• Optimal electrolyte composition identified as 0.5 M [Ca:G₄] in Pyr₁₄TFSI ionic liquid.
• Demonstrated reversible Ca²⁺ intercalation in the MCMB anode and bis(trifluoromethanesulfonyl)imide (TFSI^-) anion intercalation in the KS6L cathode.
• Achieved a high capacity of 54.0 mA h g^-1 at 200 mA g^-1 with a capacity fading rate of 0.022 mA h g^-1 cycle^-1 over 300 cycles.

Conclusions:

• Ca²⁺-based DCBs with graphite electrodes are feasible and exhibit promising electrochemical performance.
• The precisely tuned ternary electrolyte is crucial for enabling simultaneous ion and anion intercalation.
• This research paves the way for developing novel Ca²⁺-based energy storage systems.