Upcycling of low value end-of-life cathode material into next generation cathode materials

Abstract

The increase in the use of electric vehicles (EVs) will ultimately lead to an increase in the number of end-of-life lithium-ion batteries (LIBs) that need to be recycled. A particular challenge concerns how to deal with low value cathodes, such as LiMn₂O₄ (LMO). To this end, this paper investigates recycling cathode material from an end-of-life Gen 1 Nissan Leaf (2011 model, 40 000 miles) which contains a mixture of spinel (LMO) and a Ni-rich layered oxide (LO). Citric acid was employed to selectively leach LMO into solution while leaving the remaining LO as a solid. The citric acid also acts as a delamination agent to remove the remaining LO from the Al current collector. The LMO was then recovered from solution and upcycled to form new cathode materials. Ni-doping of the solution allowed the synthesis of the high voltage cathode LiMn_1.5Ni_0.5O₄ (LMNO) which is attracting commercial interest. Disordered rocksalt compounds Li₄Mn₂O₅ and Li₂MnO_2.25F were also synthesised and gave high specific discharge capacities of 293 and 279 mA h g⁻¹ respectively. This proof of concept work demonstrates a method to upcycle end-of-life cathode material into next generation cathode materials.