Fig. 1: Rapid upcycling of SLCO into L6CO.

a SEM image of SLCO (scale bar, 5 μm). b HRTEM of SLCO (scale bar, 5 nm). Region (i) represents the bulk interior of the particle, which retains a layered structure. Region (ii) corresponds to the near-surface area, where a spinel phase is observed. c XRD Rietveld refinement results for SLCO. d HRTEM images of the upcycled L6CO (scale bar, 5 nm). e XRD Rietveld refinement results for the obtained L6CO. f Initial charge and discharge curves of L6CO at 0.1 C (1 C = 800 mA g⁻¹). g Charge and discharge curves of SLCO with varying degrees of degradation (55.7%, 37.1%, 11.4% capacity retention), alongside the corresponding regenerated L6CO. All cells were cycled at 0.1 C, with 1 C = 180 mA g⁻¹ for SLCO and 1 C = 800 mA g⁻¹ for L6CO. h Schematic comparison between traditional direct regeneration (TDR) and the proposed upcycling strategy. Unlike TDR, which aims to restore original structure, the upcycling approach transforms SLCO into L6CO for additional Li supply. Blending L6CO with fresh positive electrodes in new cells markedly improves energy density and cycling stability. i Comparison of lithium and TM recovery efficiencies and processing times across different recycling routes. Circle sizes reflect relative time consumption on a logarithmic scale. The numbers in the plot correspond to the article number in Supplementary Table S3.