Ambient‐Pressure Relithiation of Degraded Li_xNi_0.5Co_0.2Mn_0.3O₂ (0 < x < 1) via Eutectic Solutions for Direct Regeneration of Lithium‐Ion Battery Cathodes

Abstract

Today's lithium-ion batteries (LIBs) can offer high energy density (260 Wh kg −1 and 700 Wh L −1 at cell level), and high Coulombic efficiency (99.98%) and long cycling life (>1000 cycles), making them the dominating power sources for portable electronics and electric vehicles (EVs). [1,2] Due to With the rapid growth of the lithium-ion battery (LIBs) market, recycling and re-use of end-of-life LIBs to reclaim lithium (Li) and transition metal (TM) resources (e.g., Co, Ni), as well as eliminating pollution from disposal of waste batteries, has become an urgent task. Here, for the first time the ambient-pressure relithiation of degraded LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523) cathodes via eutectic Li + molten-salt solutions is successfully demonstrated. Combining such a low-temperature relithiation process with a well-designed thermal annealing step, NCM523 cathode particles with significant Li loss (≈40%) and capacity degradation (≈50%) can be successfully regenerated to achieve their original composition and crystal structures, leading to effective recovery of their capacity, cycling stability, and rate capability to the levels of the pristine materials. Advanced characterization tools including atomic resolution electron microscopy imaging and electron energy loss spectroscopy are combined to demonstrate that NCM523's original layered crystal structure is recovered. For the first time, it is shown that layer-to-rock salt phase change on the surfaces and subsurfaces of the cathode materials can be reversed if lithium can be incorporated back to the material. The result suggests the great promise of using eutectic Li +

Direct Recycling of Spent NCM Cathodes through Ionothermal Lithiation

“…[24][25][26][27] The relithiation process can directly upcycle spent NCM particles to achieve pristine structure and stoichiometry but generally requires harsh experimental conditions such as high-temperature and/or high-pressure. [21,[28][29][30] Thus, it is still challenging but highly desirable to develop a scalable, cost-effective, and environment-friendly strategy for direct recycling of spent NCM cathodes.…”

“…Chen et al developed a ternary eutectic repair technology to relithiate spent NCM materials at 300 °C and annealed in oxygen with Li 2 CO 3 at 850 °C, which is very promising. [28] In order for our ionothermal relithiation to be more economical, our process has been optimized. Since ionic liquid is one of the major contributions to the cost of ionothermal relithiation process, the strategies for cost reduction have been mainly focused on reducing the amount of ILs and reuse of ILs.…”

Boosting the cycling stability of Ni-rich layered oxide cathode by dry coating of ultrastable Li3V2(PO4)3 nanoparticles

“…4e). 37 However, for the NCM622/LVP-C composite, the structure of NCM622 remained to be its original layered structure in all regions (Fig. 4f-h).…”

Direct Recycling of Blended Cathode Materials by Froth Flotation

“…Many previous efforts have been devoted to regenerating aged cathode materials from spent LIBs. [23][24][25][26][27][28] There are two major challenges to be addressed to restore the electrochemical performance of aged cathode materials. First of all, the aged cathode may have lost lithium from its structure.…”

“…Hydrothermal treatment followed by an annealing process was developed to rejuvenate LiCoO 2 , [23] and LiNi 0.33 Co 0.33 Mn 0.33 O 2 (NMC111) in LiOH aqueous solutions, [24] and LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523) in mixed LiOH/LiNO 3 molten salt solutions. [25] Second, the aged cathode undergoes phase and structural changes including cracking after numerous charge-discharge cycles that need to be repaired before reusing. Heat treatment can be used to fix some of these issues, which have been successfully used to repair aged LFP, [26] NMC111, [27] and LCO.…”