Plating and stripping calcium in an organic electrolyte

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Multivalent cation batteries, particularly those using magnesium, calcium, and aluminum, are of significant interest for next-generation energy storage.
• The metal anode remains a major challenge for these battery chemistries, limiting their practical application.
• Previous calcium plating/stripping efforts required elevated temperatures (75-100°C) and suffered from low capacities and side reactions.

Purpose of the Study:

• To demonstrate efficient room-temperature plating and stripping of calcium metal for potential use in calcium-ion batteries.
• To overcome the limitations of elevated temperatures and side reactions observed in previous calcium anode research.
• To investigate the stability and electrochemical performance of calcium metal anodes under ambient conditions.

Main Methods:

• Electrochemical plating and stripping of calcium metal at room temperature using a Ca(BH4)2 in tetrahydrofuran (THF) electrolyte.
• Characterization of plated calcium and analysis of side products using techniques not specified in the abstract.
• Cyclic voltammetry and galvanostatic cycling to assess capacity, rate capability, and cycle life.

Main Results:

• Successful plating and stripping of calcium metal at room temperature with a capacity of 1 mAh cm⁻² at a rate of 1 mA cm⁻².
• Achieved low polarization (∼100 mV) and stability over 50 cycles.
• Identified calcium hydride (CaH2) as a minor product, formed by reaction with the electrolyte, which passivates the calcium metal surface and prevents detrimental side reactions.

Conclusions:

• Room-temperature plating and stripping of calcium metal is feasible with significant improvements in capacity and stability.
• The formation of a protective CaH2 layer is key to enabling stable calcium electrochemistry at ambient temperatures.
• While challenges remain, this work represents a significant advancement towards practical calcium-ion batteries.