Toward the High-Performance Lithium Primary Batteries by Chemically Modified Fluorinate Carbon with δ-MnO₂

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Lithium/carbon monofluoride (Li/CFₓ) batteries offer high energy density but suffer from poor rate capability, limiting their widespread use.
• Improving the electrochemical performance of Li/CFₓ batteries, particularly at high discharge rates, is crucial for unlocking their full potential.

Purpose of the Study:

• To develop a facile chemical modification method for CFₓ using δ-MnO₂ to enhance the electrochemical performance of Li/CFₓ batteries.
• To investigate the impact of this modification on both energy density and rate capability.

Main Methods:

• Chemical modification of CFₓ with δ-MnO₂.
• Electrochemical testing of modified Li/CFₓ batteries, including coin cells and punch batteries, at various C-rates.
• Galvanostatic intermittent titration technique (GITT) and theoretical calculations to explore the underlying mechanisms.

Main Results:

• Modified Li/CFₓ batteries demonstrate significantly enhanced electrochemical performance at high discharge rates without compromising specific capacity.
• Coin cells achieved an energy density of 1.94 × 10³ Wh kg⁻¹ at 0.2 C, nearing the theoretical limit.
• Power densities of 5.49 × 10⁴ W kg⁻¹ (40 C) and 4.39 × 10⁴ W kg⁻¹ (30 C) were obtained for coin and punch cells, respectively, with substantial energy densities maintained.

Conclusions:

• The chemical modification of CFₓ with δ-MnO₂ effectively overcomes the rate capability limitations of Li/CFₓ batteries.
• Fast Li⁺ diffusion kinetics, facilitated by thin δ-MnO₂ flakes and reduced formation energy barriers due to chemical bonding, are responsible for the improved performance.