COBALT-LITHIUM DIOXIDE LEACHING USING CITRIC-THIOSULFATE SOLUTIONS

摘要

Cobalt and lithium recovery from spent Li-ion secondary batteries has been increasingly studied in recent years due to the high value of both metals and the low proven reserves for lithium. The standard method employed until now has been the deactivation and crushing of the batteries, followed by leaching of the LiCoO_2 spinel from the battery cathode using acid solutions, such as 1.5 to 2.0 M HC1 or H_2SO_4, in a temperature range from 120℃ to 250℃. Once leached, the cobalt is separated by electrodeposition and the lithium by precipitation, using large amounts of carbonate to bring the solution to alkaline pH values. In the present work, citric-thiosulfate solutions are used for the spinel leach at room temperature, favoring a reductive environment at room temperature, which stabilizes the cobalt(II) as cobalt citrate and lithium(I) at pH 5, and recovers approximately 99% of both metals.