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      "caption": "Fig. 1 | A comparison of spent LIB recycling technologies at different stages of development. Metallurgical recycling processes typically downcycle materials, underscoring the need for next-generation recycling technologies that preserve and even upcycle material value.",
      "caption_preview": "Fig. 1 | A comparison of spent LIB recycling technologies at different stages of development. Metallurgical recycling processes typically downcycle materials, underscoring the need for next-generation recycling technolo…",
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      "caption": "Fig. 2 | The overall experimental design of this protocol. The main experimental process includes the following: (1) disassembling spent LIBs to collect and pre-treat the spent cathode materials; (2) calculating the required additives on the basis of failure analysis results and the target product composition; and (3) selecting an appropriate method for direct recycling or upcycling.",
      "caption_preview": "Fig. 2 | The overall experimental design of this protocol. The main experimental process includes the following: (1) disassembling spent LIBs to collect and pre-treat the spent cathode materials; (2) calculating the req…",
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      "caption": "Fig. 3 | Failure analysis of spent cathode materials. a , b , Digital photos of the S-LMO pouch cell ( a ) and electrodes ( b ). c , An SEM image of the cross section of S-LMO electrode (scale bar, 2 μm). d , A digital photo of the S-LMO powder. e , SEM images of typical failure characteristics of the cathode material (from left Spent 2 Ah pouch cell LMO cathode disassembled from spent pouch cell Spent LMO cathode powder Residual binder and impurities Broken particles Intragranular cracks to right: scale bars, 2 μm, 300 nm, 1 μm and 500 nm, respectively). f , Rietveld refinement of XRD pattern of S-LMO. g , A comparison of Li content in S-LMO and C-LMO analyzed via ICP-OES. h , Mn 2 p XPS spectra collected from the spent Gr anode electrode. i , HRTEM analysis of S-LMO (scale bar, 5 nm).",
      "caption_preview": "Fig. 3 | Failure analysis of spent cathode materials. a , b , Digital photos of the S-LMO pouch cell ( a ) and electrodes ( b ). c , An SEM image of the cross section of S-LMO electrode (scale bar, 2 μm). d , A digital …",
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      "caption": "Fig. 4 | Structural characterization of regenerated LiMn 2O4 cathode materials. a , b , Rietveld refinement of XRD patterns of R-LMO-SS ( a ) and R-LMOJH ( b ) (insets, SEM images of R-LMO-SS ( a ) and R-LMO-JH ( b ); scale bars, 100 nm ( a ) and 200 nm ( b )). c , EPR spectrums of R-LMO-SS and R-LMO-JH. d , e , HRTEM analysis of R-LMO-SS ( d ) and R-LMO-JH ( e ) (scale bars ( d , e ), 5 nm).",
      "caption_preview": "Fig. 4 | Structural characterization of regenerated LiMn 2O4 cathode materials. a , b , Rietveld refinement of XRD patterns of R-LMO-SS ( a ) and R-LMOJH ( b ) (insets, SEM images of R-LMO-SS ( a ) and R-LMO-JH ( b ); s…",
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      "caption": "Fig. 5 | Electrochemical performance of regenerated LiMn 2O4 cathode materials. a , Galvanostatic charge/discharge curves of S-LMO, R-LMO-SS and R-LMO-JH in the voltage range of 3.0-4.5 V at 0.1 C. b , Cycling performance of S-LMO, R-LMO-SS and R-LMO-JH at 1 C. c , Rate performance of S-LMO, R-LMO-SS and R-LMO-JH at various current densities.",
      "caption_preview": "Fig. 5 | Electrochemical performance of regenerated LiMn 2O4 cathode materials. a , Galvanostatic charge/discharge curves of S-LMO, R-LMO-SS and R-LMO-JH in the voltage range of 3.0-4.5 V at 0.1 C. b , Cycling performan…",
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      "caption": "Fig. 6 | Structural characterization of upcycled high-voltage cathode material LiNi 0.5 Mn1.5 O4. a , XRD patterns of upcycled precursors and products (powder diffraction file (PDF); insets show digital photos of the corresponding powders). b , Rietveld refinement of XRD pattern of U-LNMO. c , EPR spectrums of U-LNMO and C-LNMO. d , SEM image and EDS mapping of U-LNMO (scale bar, 500 nm). e , EDS line scan of the internal section of U-LNMO. f , HRTEM analysis of U-LNMO (scale bar, 5 nm).",
      "caption_preview": "Fig. 6 | Structural characterization of upcycled high-voltage cathode material LiNi 0.5 Mn1.5 O4. a , XRD patterns of upcycled precursors and products (powder diffraction file (PDF); insets show digital photos of the co…",
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      "caption": "Fig. 7 | Electrochemical performance of upcycled high-voltage cathode material LiNi 0.5 Mn1.5 O4. a , Galvanostatic charge/discharge curve of U-LNMO in the voltage range of 3.5-4.9 V at 0.1 C (The inset is the corresponding d Q /d V curve). b , Cycling performance of U-LNMO and C-LNMO at 1 C. c , The rate performance of U-LNMO and C-LNMO at various current densities.",
      "caption_preview": "Fig. 7 | Electrochemical performance of upcycled high-voltage cathode material LiNi 0.5 Mn1.5 O4. a , Galvanostatic charge/discharge curve of U-LNMO in the voltage range of 3.5-4.9 V at 0.1 C (The inset is the correspon…",
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      "caption": "Fig. 8 | Structural characterization of upcycled Li-rich Mn-based cathode material Li 1.2 Ni0.2 Mn0.6O2. a , XRD patterns of upcycled precursors and products (the insets show digital photos of the corresponding powders.) b , Rietveld refinement of XRD pattern of U-LRMNMO. c , EPR spectrums of U-LRM and C-LRM. d , SEM image and EDS mapping of U-LRM (scale bar, 500 nm). e , EDS line scan of the internal section of U-LRM. f , HRTEM analysis of U-LRM (scale bar, 5 nm).",
      "caption_preview": "Fig. 8 | Structural characterization of upcycled Li-rich Mn-based cathode material Li 1.2 Ni0.2 Mn0.6O2. a , XRD patterns of upcycled precursors and products (the insets show digital photos of the corresponding powders.…",
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      "caption": "Fig. 9 | Electrochemical performance of upcycled Li-rich Mn-based cathode material Li 1.2 Ni0.2Mn0.6O2. a , Galvanostatic charge-discharge curve of U-LRM in the voltage range of 2.0-4.8 V at 0.1 C (the inset is the corresponding d Q /d V curve). b , Cycling performance of U-LRM and C-LRM at 1 C. c , Rate performance of U-LRM and C-LRM at various current densities.",
      "caption_preview": "Fig. 9 | Electrochemical performance of upcycled Li-rich Mn-based cathode material Li 1.2 Ni0.2Mn0.6O2. a , Galvanostatic charge-discharge curve of U-LRM in the voltage range of 2.0-4.8 V at 0.1 C (the inset is the corr…",
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      "caption": "Table 1 | Comparison of key parameters of spent LIB recycling technologies at different stages of development",
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      "caption": "Table 2 | Comparison of key parameters of five direct regeneration methods",
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      "caption": "Table 3 | The proportion of primary materials used in various direct regeneration and upcycling processes",
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      "caption": "Table 4 | Basic parameter settings for electrochemical testing of different materials in this protocol",
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