Understanding and\nControlling Structural Defects and\nDisordering in LiNi<sub>0.5</sub>Mn<sub>1.5</sub>O<sub>4</sub> Cathodes\nfor Direct Recycling

Despite significant progress in recycling spent lithium-ion\nbatteries\n(LIBs), nondestructive, direct recycling methods still face untenable\ndiscrepancies in multiple cathode chemistries, which primarily originate\nfrom a variety of structure stabilities during the recycling process.\nThrough systematic investigation of the microstructure evolution during\nthe relithiation treatment, we observed the inevitably induced defects\nand Li/Mn disordering in the LiNi<sub>0.5</sub>Mn<sub>1.5</sub>O<sub>4</sub> cathode, contributing to the sluggish Li<sup>+</sup> transport\nand irreversible capacity loss. Employing a defect engineering approach\nto achieve twin boundaries and preferred grain orientation, we show\nthe regenerated cathodes demonstrate a substantial enhancement of\nLi<sup>+</sup> diffusion and cycling stability, retaining 97.4% capacity\nafter 100 cycles and 87.96% after 200 cycles at C/3. This work not\nonly elaborates on a systematic investigation of defect inducement\nand structural restoration mechanism but also provides an effective\napproach to directly recycle high-voltage spinel-type cathodes, contributing\nto the sustainability of next-generation LIBs.