fig3

Figure 3. (A) Schematic representation of four nanostructures; (B) Schematic illustration of the synthetic procedure of the FC samples; (C) Initial charge and discharge curves of AC and FC electrodes in sodium-ion battery with a current density of 20 mA·g^-1[34]. Copyright 2023, RSC; (D) TEM images of the core-shell PNC@SC particles with different loadings of PNC; (E) Comparison of rate performance of pure SC, 1PNC@SC, 3PNC@SC and 5PNC@SC-based electrodes^[35]. Copyright 2023, Wiley-VCH; (F) Schematic of different stages of sol-gel process^[37]. Copyright 2021, The authors, published by Wiley-VCH; (G)SEM and (H) HR-TEM images of Si@MoO2@C^[39]. Copyright 2020, Wiley-VCH. AC: Activated carbon; FC: filling carbon; PNC: porous nano-carbon; SC: sulfur/carbon composite secondary particles; SEM: scanning electron microscopy; TEM: transmission electron microscopy; HR-TEM: high-resolution transmission electron microscopy.