Lithium and cobalt extraction from LiCoO2 assisted by p(VBPDA-co-FDA) copolymers in supercritical CO2.

Supercritical CO2 (scCO2) extraction assisted by complexing copolymers is a promising process to recover valuable metals from lithium-ion batteries (LIBs). CO2, in addition to being non-toxic, abundant and non-flammable, allows an easy separation of metal-complexes from the extraction medium by depressurization, limiting the wastewater production. In this study, CO2-philic gradient copolymers bearing phosphonic diacid complexing groups (poly(vinylbenzylphosphonic diacid-co-1,1,2,2-tetrahydroperfluorodecylacrylate), p(VBPDA-co-FDA)) were synthesized for the extraction of lithium and cobalt from LiCoO2 cathode material. Notably, the copolymer was able to play the triple role of leaching agent, complexing agent and surfactant. The proof of concept for leaching, complexation and extraction was achieved, using two different extraction systems. A first extraction system used aqueous hydrogen peroxide as reducing agent while it was replaced by ethanol in the second extraction system. The scCO2 extraction conditions such as extraction time, temperature, functional copolymer concentration, and the presence of additives were optimized to improve the metals extraction from LiCoO2 cathode material, leading to an extraction efficiency of Li and Co up to ca. 75 % at 60 °C and 250 bar.

A multi-analytical methodology for the characterization of industrial samples of spent Ni-MH battery powders.

A multi-analytical methodology is implemented to characterize several sieving fractions of industrial samples of Black Mass (BM) powders originating from the thermo-mechanical treatment of cylindrical and prismatic-type spent nickel metal-hydride (Ni-MH) batteries. Elemental analyses of 17 elements (including C and O) indicate that the elemental composition of the powders (greater than93 %wt) does not depend on the battery type nor on the sieving fraction. XRD analyses evidence several phases (including Ni, NiO, CeO2 and C) but their quantification is not possible. Beyond these standard characterisations, magnetic susceptibility measurements demonstrate that the amount of metallic nickel versus nickel oxide increases with the sieving fraction, and that powders from prismatic-type batteries contain twice as much metallic nickel than cylindrical ones. Thanks to statistical analysis (based on clustering algorithms) of an electron probe µ-analysis (EPMA) compositional map, the complete methodology allows us to propose a full phase distribution for the BM particles. Three types of particles are identified and quantified. They originate from the partial oxidation of the battery components (anode active mass, anode current collector, cathode active mass and cathode current collector). The whole picture highlights the joint importance of battery ageing mechanisms, thermal deactivation and BM sieving steps on powder composition.

Leaching Mechanisms of Industrial Powders of Spent Nickel Metal Hydride Batteries in a Pilot-Scale Reactor.

In view of a sustainable recycling process, the leaching mechanisms of nickel and rare-earth elements (REEs) contained within industrial samples of spent nickel metal hydride battery powders were investigated in HCl and H2 SO4 , under mild temperature (25-60 °C) and pH (3-5.5). First, in-depth characterization of the heterogeneous battery powder was carried out with powder XRD, SEM, electron probe microanalyzer wavelength-dispersive spectroscopy (EPMA-WDS) quantitative analyses of individual particles, and inductively coupled plasma optical emission spectrometry (ICP-OES) elemental analysis. An unusual result is the identification of particles that exhibit a core-shell structure, which is related to anode active mass aging mechanisms. Then, a leaching study in a 10 L pilot-scale reactor demonstrated the selective dissolution of REEs, with respect to nickel, at pH 3, which is attributed to 1) the kinetic inhibition of nickel metal dissolution, and 2) the specific core-shell structure of aged mischmetal particles. Furthermore, the use of H2 SO4 led to coprecipitation of lanthanide-alkali double sulfates and nickel salts.

Fluidized bed chemical vapor deposition of silicon on carbon nanotubes for Li-ion batteries.

Silicon was deposited on balls of entangled multi-walled carbon nanotubes (CNT) with a mean diameter of several hundreds of microns, by Fluidized Bed Chemical Vapor Deposition from silane (SiH4). The weight total percentage of deposited silicon was between 30 and 70%, to test their efficacy in Li-ion battery anodes. TEM and SEM imaging revealed that silicon deposits were of the form of nanoparticles uniformly dispersed on the whole CNT surface. The diameter of these nanoparticles increases with the deposited silicon percentage from 18 to 36 nm whereas their density remains constant at 5 10(22) nanoparticles/g of CNT. This indicates a low affinity of chemical species born from silane pyrolysis with the CNT surface for nucleation. The increase of the silicon nanoparticles diameter leads to the decrease of the specific surface area and the porous volume of the balls, probably due to the filling of the pores of the CNT network by silicon. A slight increase of the mean diameter of the balls was observed for the two highest silicon percentages, certainly due to the ability of the CNT network to be deformed under the mechanical stress induced by the silicon nanoparticles growth.