LiC₆@Li as a Promising Substitution of Li Metal Counter Electrode for Low-Temperature Battery Evaluation

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Lithium (Li) metal is commonly used as a counter electrode in coin-type half-cells for evaluating electrode materials.
• The suitability of Li metal as a counter electrode under various working conditions, particularly low temperatures, is often overlooked.
• Li metal exhibits significant resistance and high over-potentials at cryogenic temperatures, compromising its performance.

Purpose of the Study:

• To highlight the limitations of Li metal as a counter electrode at low temperatures.
• To develop and evaluate a novel composite electrode as a superior alternative for low-temperature electrochemical studies.
• To demonstrate the necessity of specialized counter electrodes for accurate material evaluation under specific operating conditions.

Main Methods:

• Development of a LiC6@Li composite electrode.
• Comparative analysis of Li metal and LiC6@Li electrodes at -20 °C.
• Evaluation of cathodic/anodic over-potential and potential stability.
• Testing the performance of LiC6@Li-based half-cells for electrode material evaluation.
• Preparation and testing of a KC8@K composite electrode as an analogous system.

Main Results:

• Li metal shows high resistance and over-potential (0.05 V at -20 °C) at cryogenic conditions.
• The novel LiC6@Li composite electrode exhibits significantly lower over-potential (ten times lower than Li metal) at -20 °C.
• LiC6@Li demonstrates stable potential due to rapid lithium replenishment from the Li metal.
• LiC6@Li-based half-cells enable more precise evaluation of Li+ storage potential and capacities of electrode materials at low temperatures.
• KC8@K was successfully prepared as a superior counter electrode to K metal.

Conclusions:

• The LiC6@Li composite electrode is a promising substitute for Li metal as a counter electrode in low-temperature evaluations.
• This work emphasizes the need for specialized counter electrodes tailored to specific operating conditions, such as subfreezing environments.
• The findings facilitate more accurate assessment of battery materials under challenging cryogenic conditions.