Extraction of lithium from spinel phases of the system Li_(1+x)Mn_(2-x)O_(4-δ)

摘要

The process of chemical lithium extraction from the spinel phase Li_(1+x)Mn_(2-x)O_(4-δ) was studied for 0 <= x <= 0.33 in acidic medium (H_2SO_4/ H_2O) and Br_2/CH_3CN as proton-free extraction liquid. From a comparison of the quantitative results of chemical delithiation with the electrochemical performance there follows a subdivision into three regions. In region I (0 <= x <= 0.05) the extraction products are multiphase due to a pronounced lattice instability. The electrochemical performance is unsatisfying. The best materials for cathodes in rechargeable Li- ion batteries are situated in region II (0.05 <= x <= 0.2). All extraction products are single phase due to an improved lattice stability. In region III (0.2 <= x <= 0.33) the capacity is too low for practical applications. All materials are oxygen deficient and show a strong tendency for an ion exchange Li~+ ←→ H~+ in protonic solvents. In acidic media, the Hunter mechanism is obeyed for x = 0. With increasing x this model is suppressed in favour of a Li~+←→ H~+ exchange.