Using ultrasonic oil–water nano-emulsions to purify lithium-ion battery black mass†

Abstract

Long-loop recycling of spent lithium-ion batteries is neither sustainable nor economical at scale. In the absence of design-to-recycle initiatives taken up by cell manufacturers, even for batteries produced today, all-in-one shredding processes are the only practical option to achieve circularity of critical materials. Shredding lithium-ion batteries ultimately produces ‘black mass’ – a low-value commodity comprising a mixture of graphite from the anode and lithium metal oxides from the cathode. Recovery of valuable metals such as cobalt and nickel from black mass using energy-intensive pyro- and hydro-metallurgy processes inevitably destroys the crystalline structure of lithium metal oxides and thus requires further resynthesis of battery material upon isolation and purification. This study presents an efficient process for direct separation of graphite and lithium metal oxides from numerous sources of black mass by utilizing a meta-stable oil-in-water emulsion. The purification of black mass is facilitated by one minute of high-power ultrasonic agitation followed by sieve separation, whereby the ultrasonic process enabling purification requires ca. 1% of the energy for heat removal of the binder. The separation exploits the disparity in hydrophobicity between graphite and lithium metal oxides, with ultrasonic energy enhancing the efficacy of the process to allow separation of cathode and anode counterparts with purity as high as 96% within minutes of operation. This innovative approach offers a promising solution for short-loop recycling of lithium-ion battery black mass.