Recovery of positive electrode active material from spent lithium-ion battery

Abstract

This thesis aims to design and develop environmentally friendly process by using mineral processing technique in liberating and concentration positive electrode active material. The original contribution to the body of knowledge is related to the unique insights into the selective liberation of lithium-ion battery (LIB) by applying cutting mill and attrition scrubbing aim at concentrating LiCoO2 particles. The current research practice often involves the use of organic solvent such as n-methyl-pyrrolidone (NMP) to dissolve the polyvinylidene fluoride (PVDF) to obtain LiCoO2 concentrate. However, the use of mechanical treatment to effectively liberate LiCoO2 is still under examined. This study is carried out by employing mineral processing techniques. The initial liberation by using only cutting mill produce selective liberation with optimum cut point of 850 µm. However, 56.3 wt% of LiCoO2 active materials are still held together by the PVDF binder and laminating the surface of the current collector in the size fraction of > 850 µm. This result suggests that the selective liberation by only using cutting mill is sub-optimum. The lack of liberation prompted the use of attrition scrubbing as a secondary stage of mechanical treatment. Attrition induces abrasion and it is shown to effectively liberate the LiCoO2 particles. The proof of concept shows 80.0 wt% LiCoO2 particles can be recovered in the size region of < 38 µm with 7.0 wt% aluminium and 6.1 wt% copper recovery, making attrition scrubbing a suitable second stage mechanical treatment for the recovery of LiCoO2 particles. The relative breakage rate between LiCoO2, copper and aluminium during attrition have also been studied. To further the discussion, parameters affecting attrition scrubbing liberation have been studied and presented. The proof of concept to further separate the attrition product have also been reported. The separation techniques involve electrostatic separation to separate copper and aluminium in the larger size fraction (> 38 µm) and froth flotation to separate the graphite from the finer size region (< 38 µm).

Date of Award	8 Nov 2020
Original language	English
Awarding Institution	Univerisity of Nottingham
Supervisor	Philip Hall (Supervisor), Summers Peter (Supervisor) & George Mike (Supervisor)