Incorporation of Cu into Li[Ni1/3Co1/3Mn1/3]O2 cathode: Elucidating its electrochemical properties and stability

Resynthesized cathode active materials from the leaching solution of spent lithium ion batteries can contain a Cu impurity element, which is anode current collector. There is also a lack of consensus on the effects of Cu doping element/impurity in cathode active materials. We synthesize LiN1/3Mn1/3Col/3O2 (NCM) active materials with the addition of Cu. The effects of Cu on the electrochemical properties (initial charge/discharge capacity, rate capability, and cycleability) of NCM cathode are investigated under different experimental conditions such as cutoff voltage and temperature. Initial charge/discharge capacities gradually decrease and rate capability deteriorates with increasing the Cu content. The enhanced capacity retention of NCM with a certain range (similar to 1.5 mol%) of Cu content is obtained. A decline in the discharge capacity of the full cell, where graphite is adopted as anode active material, is more prominent than that of the half cell. Whereas the graphite anode before cycling contains no metal component on the surface, the surface composition on the graphite anode after cycling is dominated mostly by Cu, followed by Mn, with a negligible amount of Co and Ni. Cu in the NCM cathode dissolves and the dissolved Cu ions are deposited on the graphite surface, which would deteriorate the full cell performance. (C) 2018 Elsevier B.V. All rights reserved.