A Ternary Molten Salt Approach for Direct Regeneration of LiNi_0.5Co_0.2Mn_0.3O₂ Cathode

Abstract

metals and organic electrolytes, which are hazardous to the environment.Apparently, recycling spent LIBs is a far-sighted strategy for both resource recovery and environmental protection. Particularly, re-utilizing the cathode materials is the primary task for battery recycling since they make up approximately 35% of the cost and contain abundant valuable metals. [4] Conventional approaches to recycle cathodes are based on the hydrometallurgy [5] and pyrometallurgy [6] processes, which are either tedious or energy-consuming and produce massive liquid/gaseous pollutants. [7] Overall, both methods aim to extract metals through complete physical and chemical destruction of the cathode materials. [4,8] LIBs typically retire when losing more than 20% of the initial capacity, yet the bulk structure of the electrode materials remains largely intact. [8b,9] State-of-the-art recycling approaches focus on directly regenerating the cathodes by a non-destructive process to recover the losing capacity and restore the original structure. In a typical process, after harvesting the electrode materials from current collectors (e.g., by dissolution, [10] mechanical separation, [4] or heat treatment [11] ) and removing the inactive components (e.g., polymer binders and acetylene black), the spent cathode powders are treated with Li sources for relithiation. For example, wet chemistry [12] and solid state [4,13] approaches have been demonstrated to regenerate LiCoO 2 and Ni-poor NCM cathodes, in which the capacity loss is mainly ascribed to the Li loss. Nevertheless, precise control of the reaction condition and/or stoichiometry of reactants is generally required, making these two approaches less versatile.Different from the above liquid-or solid-state approaches, molten salts have recently emerged as promising reaction mediums to regenerate cathode materials due to their low melting point, favorable reaction medium, fast ion diffusivity, and so on. [8b,14] Binary eutectic molten salts such as LiOH+LiNO 3 , [8b] LiOH+Li 2 CO 3 , [14b] and LiNO 3 +sylvite [15] have been successfully applied to recover the spent NCM cathodes. Nevertheless, the capacity decay of NCM cathodes not only results from the loss of active Li but also comes from cation mixing and subsequent formation of undesirable rock salt/spinel phases. [12a,16] Although the above binary eutectic molten salts have been found to partially restore the crystallographic structure of NCM cathodes, full recovery of the lattice Li and elimination of the cation mixing remain unconquered challenges.Recycling spent lithium-ion batteries (LIBs) is an urgent task in view of the resource shortage and environmental concerns. Here, a facile ternary molten salt approach is presented for efficiently regenerating the LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523) cathode of spent LIBs. Such an approach involves the treatment of spent cathode powder in the ternary molten salt at a moderate temperature (400 °C) and subsequent annealing in oxygen. The Li loss and degraded phases in spent NCM that...

Effective separation of LiNi0.5Co0.2Mn0.3O2cathode material and Al foilviadigestion of PVDF enabling a closed-loop recycle

“…In order to achieve closed-loop recycling, a ternary molten salt strategy was adopted for direct regeneration of the lithium nickel cobalt manganese oxide (LiNi 0.5 Co 0.2 Mn 0.3 O 2 , NCM523) cathode. 42 The XRD pattern of regenerated NCM (denoted as R-NCM) is displayed in Fig. S7a †.…”

Advances in Intelligent Regeneration of Cathode Materials for Sustainable Lithium‐Ion Batteries

“…The measurement results revealed that the regenerated LiNi 0.5 Co 0.2 Mn 0.3 O 2 cathode materials delivered a reversible capacity of 160 mAh g -1 at 0.5 C with retention of 93.7% after 100 cycles, which is compared favorably to the fresh ones, indicating the effectiveness of this ternary molten salt system to directly regenerate the degraded cathode materials. [159] Yang and co-workers also reported a ternary eutectic system of LiOH-KOH-Li 2 CO 3 to restore the electrochemical performances of degraded LiCoO 2 cathode materials in the air atmosphere. [158] A "dissolution-recrystallization" mechanism was proposed to elucidate the regeneration process, in which the LiOH-KOH-Li 2 CO 3 molten salt with abundant Li + , homogeneous thermal circumstance, suitable dissolving capacity, and high ion diffusion rate should facilitate the compensation of Li + deficiencies, decomposition of impurities and final renovation of damaged structures.…”

“…Moreover, the direct regeneration process in molten salt mixture can be carried out at an ambient pressure, in a sharp contrast with the high-pressure conditions applied in hydrothermal solution, which further increases its convenience and universality for regenerating cathode materials. [156][157][158][159] Note that, the peeled cathode materials from retired LIBs in an industrial process usually contain impurities, such as PVDF binders, carbon-based conductive agents, etc. [67,71,160] It is significant to realize the direct renovation of degraded cathode materials in such a complex system for the large-scale production.…”

Toward practical lithium-ion battery recycling: adding value, tackling circularity and recycling-oriented design

“…Molten eutectic salts can be used as a re-lithiation reagent, via provision of low temperature, ambient pressure, and liquid environment for regeneration. [176][177][178][179][180][181][182][183] Eutectic molten salts, including LiOH-LiNO 3 , LiOH-Li 2 CO 3 and KCl-KNO 3 -LiNO 3 have been used in regeneration of NCM523 material which exhibited significant performance. [176][177][178] Molten salts, including Li 2 SO 4 -LiOH for single-crystal Ni-rich NCM, 179,180 and LiOH-KOH-Li 2 CO 3 for LiCoO 2 , and LiOH-LiNO 3 for NCM111 and LMO, are reported.…”