南开大学、福建师范大学，AFM：优化轨道杂化诱导的抑制多级相变并增强超低温(-70°C)钠存储的氧化还原动力学

优化轨道杂化诱导的抑制多级相变并增强超低温(-70°C)钠存储的氧化还原动力学

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Figure 1. a) The working mechanism of regenerated sodium-ion battery cathodes. b) XRD patterns of RMNC-0, RMNC-2 and RMNC-4. c) Rietveld refinement analysis of the XRD pattern of RMNC-2. d) Additional TEM image of RMNC-2. e) SAED pattern of RMNC-2. f) STEM–HAADF image of RMNC-2. g) EDS analysis at the atomic scale.

Figure 2. Electrochemical properties at 25 °C: a) GCD profiles of RMNC-2 at 0.5 C. b) Rate performance of RMNC-0, RMNC-2 and RMNC-4. c) Cycling performance of RMNC-0, RMNC-2 and RMNC-4 at 0.5 C. d) Cycling performances of RMNC-0 and RMNC-2 at 0.5 C from −10 to −70 °C. Electrochemical properties at −40 °C: e) Rate performances of RMNC-0 and RMNC-2. Cycling performances of RMNC-0 and RMNC-2 at f) 0.2 C and g) 5 C. h) Comparison of the electrochemical performance of RMNC-2 with other recently reported cathodes for SIBs at −40 °C (materials not tested at −40 °C are marked accordingly).

Figure 3. In-situ XRD patterns of a) RMNC-0 and b) RMNC-2 electrodes at different voltage states (1.5–4.2 V) at 0.1 C. c) Crystal structure evolution of RMNC-0 and RMNC-2. d) Evolution of lattice parameters obtained by rietveld refinement. e) In-situ EIS spectra of RMNC-2 and RMNC-0 at different voltages (-40°C). f) STEM–HAADF images of RMNC-2 electrodes in their uncycled state and after multiple cycles, recharged to 4.2 V. g) ICP results showing Mn ion dissolution after 200 cycles at 2 C for RMNC-0 and RMNC-2. h)  Mn atomic ratio on the surface of sodium metal after 200 cycles at 2 C.

Figure 4. a) EIS study of RMNC-2 at various temperatures. Evolution of b) RCEI and c) Rct in different temperatures for RMNC-0 and RMNC-2 electrolytes. d) Calculated activation energy for RMNC-0 and RMNC-2. Comparison of the F 1s and O 1s XPS spectra of e) RMNC-0 and f) RMNC-2. g) Three-dimensional reconstructed images of the CEI for RMNC-2, showing the signals of C₂HO⁻, CHO₂⁻, NaF₂⁻, NiF₃⁻, MnF₃⁻ and CoF₃⁻ species. h) TOF-SIMS depth profiles of NiF₃⁻, MnF₃⁻, CoF₃⁻, C₂HO⁻, CHO₂⁻ and NaF₂⁻ species in RMNC-2.

Figure 5. Coordination environment characterization of RMNC-0 and RMNC-2: a) Mn normalized K-edge XANES spectra; b, c) Mn normalized K-edge XANES spectra and d, e) Mn EXAFS analysis of the samples at different voltages during the first cycle. f) WT-EXAFS spectra of RMNC-2 at different voltages. g) Crystal structure of RMNC-2 doped with Zn at the Ni site. h) Doping formation energies for Zn substitution at Co, Mn, Ni and Na sites. i) Energy difference between Nae and Naf sites in RMNC-0 and RMNC-2. j) TDOS for RMNC-2 and RMNC-0 (Local). k) DOS of O 2p and Ni 3d orbitals for RMNC-0 and RMNC-2. l) Schematic representation of the DOS for RMNC-0 and RMNC-2.

Figure 6. The performance of the full cell consisting of RMNC-2 and HC: a) Schematic diagram illustrating the operational principle of the HC || RMNC-2 full cell. b) GCD curves for RMNC-2 and hard carbon in a half-cell configuration. c) Rate performance of the HC || RMNC-2 full cell. Cycling stability of the HC || RMNC-2 full cell at d) 0.5 C and e) 2 C. f) Electrochemical energy storage performance of HC || RMNC-2 full cell at −20 °C. g) Cycling performance of HC || RMNC-2 pouch cell at 0.5 C. h) Performance of HC || RMNC-2 pouch cell under different temperatures from 25 to −30 °C during cycling at 0.2 C. i) Schematic diagram of HC || RMNC-2 pouch cell powered a mobile phone. Analysis of economic and environmental effects of synthetic regenerated RMNC-2 and commercial cathode (CM-NCM). j) Life cycle cost of each part. k) Total life cycle cost. l) Environmental impact characterization results.

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