Circular Manufacturing and Direct Recycling of Li-Ion Batteries Electrodes Via Solventless Melt Process

Abstract

The expansion of the electric vehicles (EV) market demands new green fabrication methods of lithium-ion batteries (LIBs), a crucial component of EVs. At the same time, it provokes a dramatic increase of production scrap volume of LIBs with more and more EV batteries reaching end-of-life in the next years. LIBs are hazardous, posing chemical and fire risks, especially at their end-of-life. Considering their growing volume, disposal in landfill is no more an acceptable option. Furthermore, LIBs contain high-value materials (cobalt, nickel, lithium...), many of which are mined and produced via unsustainable or unethical supply chains. Thus, it becomes important to manufacture, salvage and recycle LIBs safely, responsibly and by minimizing production residues. Current recycling processes, namely pyrometallurgy and hydrometallurgy are complex, energy intensive and/or requiring large amounts of water and other chemicals for the separation of valuable elements and the preparation of new active materials. We have developed an inexpensive original melt solventless high-shear process for the manufacturing of Li-ion cathodes and anodes as well as the direct recycling of scrap electrodes and used electrodes. This process is adapted to a variety of electrodes morphologies and chemistries. This process consists in the following steps: - First, active filler dispersions are obtained in the melt using a combination of a permanent binder at low content < 3 wt% and an inexpensive commercial sacrificial binder. The sacrificial binder is a mixture of commercially available polymers made from conversion of carbon dioxide CO2. - The dispersions are then cast on the current collector using a calendaring process to yield 50-250 µm coatings depending on the final application (both high-energy and high-rate are possible). - The sacrificial binder is then degraded thermally at high speed at low temperature below 250°C to yield an electrode of tailored porosity possessing an improved adhesion to the collector compared to conventional PVDF solvent processed electrodes. Melt formulations were developed for several conventional Li-ion cathodes, namely LFP, NCA, NMC and conventional Li-ion anodes. A large range of loadings could be achieved, from 4 to 40 mg/cm2. Electrochemical performances in half cells will be presented, demonstrating high capacity and cyclability for high loadings, as well as the performances at high rates, up to 10 C. Important benefit of our process is reusage of already manufactured electrode material. Fabricated electrode material can be mixed with fresh blend to process a new electrode. Both cathode (NMC 622 and LFP) and anode (graphite) scraps were sucessfully remanufactured. The reprocessing does not alter electrode performance, even if we completely reuse old electrode material without diluting it into a fresh melt. That means that all scrap could be subsequently reprocessed without change in electrode performance. Moreover, the developed melt process is capable to reintegrate used cathode or anode material removed from its current collector (i.e. black mass) giving a new functional electrode. Such electrode material to be recycled can be initially manufactured via conventional solvent (NMP or aqueous) process with conventional binders (PVDF, CMC). Direct incorporation of up to 25 wt% recycled electrode materials including binders and conductive additives from used lithium-ion batteries into fresh electrode compositions in one step has been demonstrated. At our knowledge, that is a sole process able to directly recycle all electrode material without separation of active material from conductive carbon black and binder. Therefore, the presented melt process will illustrate shortening and better valuation of the battery production supply chain. Figure 1