Flotation of Electrode Materials in Spent LiFePO4 Batteries Enhanced by Selective Flocculation
In the flotation process of electrode materials from spent LiFePO4 batteries,the occurrence of entrainment and entrapment usually leads to poor separation effect.Aiming at such problem,selective flocculation with polyvinylpiroxanone(PVP)and polyacrylic acid(PAA)was adopted to enhance the flotation effect in an experimental study,and the interaction mechanism between PVP and PAA and electrode materials was also analyzed.Results show that the firstly added PVP can be selectively adsorbed on the graphite surface by hydrogen bonding,thus inhibiting the spontaneous hydrophobic flocculation of graphite.Then,due to site-blocking effect,the subsequently-added PAA is inhibited to be adsorbed on the graphite surface,leading to selective flocculation of LiFePO4 by PAA.A combined usage of PVP and PAA can not only make graphite effectively dispersed,but also lead to apparent particle size(D50)of LiFePO4 cathode material increased from 15.01 μm to 26.17 μm.As a result,the loss of LiFePO4 due to entrainment in the flotation process of mixed electrode can be effectively reduced,thus the recovery rate of LiFePO4 cathode material by flotation process can be improved from 71.41％to 83.59％.
lithium iron phosphatespent battery recyclingcathode materialgraphiteelectrode materialselective flocculationflotation
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