LiCoO2

LiCoO2, or lithium cobalt oxide, is a layered transition-metal oxide that serves as a common cathode material in lithium-ion batteries. Its chemical formula is LiCoO2, with cobalt typically in the +3 oxidation state in the discharged state.

Structure and electrochemistry: LiCoO2 crystallizes in a layered α-NaFeO2-type structure, with alternating Li+ and Co ions in a close-packed oxygen lattice. During charging, lithium ions are extracted and cobalt is oxidized toward +4. The reaction Li1−xCoO2 ⇄ LiCoO2 + xLi+ + xe− yields a theoretical capacity of 274 mAh/g, but practical cells cycled to a 4.2 V cutoff typically deliver about 140–160 mAh/g. The material undergoes structural changes as it delithiates, which can limit cycle life at high states of charge. While generally stable at moderate SOC, deeper delithiation or overcharge can raise safety concerns due to potential oxygen release and thermal instability.

Synthesis and processing: LiCoO2 is usually produced by solid-state synthesis from lithium precursors (such as Li2CO3) and cobalt oxides or carbonates, calcined at high temperatures (approximately 700–800°C) in air or oxygen. Controlling lithium content is important to minimize defects and optimize conductivity and rate capability. Particle size, coating, and doping are used to influence performance and robustness.

Applications and market context: It has long been a dominant cathode in consumer electronics because of its high energy density and well-characterized chemistry. However, cobalt cost, supply risk, and thermal stability have spurred development of cobalt-reduced formulations such as nickel-rich layered oxides (NMC) and other chemistries for large-format batteries. LiCoO2 remains a focus of research for safer, lower-cobalt variants and is still used in some cells under moderate cycling conditions.

Environmental and recycling aspects: Cobalt mining raises ethical and environmental concerns, and recycling LiCoO2-rich batteries helps recover cobalt and reduce supply risk.