Long-Term Highly Stable High-Voltage LiCoO₂ Synthesized via a Solid Sulfur-Assisted One-Pot Approach

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Commercial lithium cobalt oxide (LCO) exhibits limited capacity (≈175 mAh g⁻¹) compared to its theoretical potential (≈274 mAh g⁻¹).
• Increasing LCO's charge cutoff voltage is a strategy to enhance capacity but is hindered by phase transitions, oxygen loss, and electrolyte degradation.

Purpose of the Study:

• To develop a stable, high-voltage LCO material with improved capacity retention.
• To overcome the limitations of conventional LCO by employing a novel synthesis approach.

Main Methods:

• An in situ sulfur-assisted solid-state approach was utilized for one-pot synthesis of LCO.
• Simultaneous in situ formation of spinel LiₓCo₂O₄ shells and gradient doping of SO₄²⁻ polyanions into LCO via gas-solid interface reactions.
• Utilized generated SO₂ gas from sulfur reacting with metal oxides during synthesis.

Main Results:

• The synthesized high-voltage LCO demonstrated a discharge capacity of 232.4 mAh g⁻¹ at 0.1 C and 215 mAh g⁻¹ at 1 C at 4.6 V.
• Exceptional capacity retention of 97.4% after 100 cycles and 89.7% after 300 cycles at 1 C was achieved.
• The material maintained a capacity of 139 mAh g⁻¹ even at a high rate of 20 C.

Conclusions:

• The sulfur-assisted synthesis provides a facile, low-cost, and scalable method for producing highly stable high-voltage LCO.
• The novel compound structure with spinel shells and polyanion doping effectively suppresses degradation pathways.
• This approach offers a promising route for enhancing the performance of LCO and other electrode materials for next-generation batteries.