Fig. 1

Schematic diagram of modification strategies of soft carbon materials"

Fig. 2

Traditional model (a1) and alternative model (a2) of soft carbon and microporous carbon[23]; Typical powder X-ray diffraction of hard carbon (b) and soft carbon (c)[24],The arrow indicates the apparent (002) peak location of hard carbon; (d) Small Angle X-ray Scattering Pattern[25]"

Fig. 3

Theoretical model of sodium storage in hard carbon [32]"

Fig. 4

(a) Charge and discharge curve of soft carbon materials in sodium-ion batteries[33]; (b) In situ X-ray scattering scan of Na+ inserted into soft carbon; (c,e) Insertion behavior of Li+ in soft carbon; (d,f) Na+ insertion behavior in soft carbon[35]"

Fig. 5

Proposed Na+ storage mechanism in different carbon anodes[37]"

Fig. 6

(a) Preparation principle diagram of ZAD-3-800; (b) high-resolution C1s spectra of POMP800 (b1), ZAD-3-800 (b2) and ZnO-3-800 (b3); (c) Negative charge and discharge curves of POMP800 (c1), ZnO-3-800 (c2) and ZAD-3-800 (c3) at 0.05 A g-1[45]"

Fig. 7

(a) Schematic diagram of the preparation process of porous carbon[46]; (b) Manufacturing process diagram of 3DHSC[47]; (c) Cyclic performance of HSC and 3DHSCs at 0.05 A g-1 current density[47]"

Fig. 8

(a) XRD patterns of CNS1000 and PCNS1000[50]; (b) Measurement of long-term cyclic stability of PCNS1000[50]; (c) Cyclic properties of CSC and PSC materials at 100 mA g-1[52]; (d) Element mapping of STEM images and corresponding C-K, S-K, and O-K distributions for SG selected regions[53]"

Fig. 9

SEM images of A (a) SC-600, (b) SC-800 and (c) SC-1000, element maps of (d), (e) and (f) SC-800, HRTEM images and SAED of (g) SC-600, (h) SC-800 and (i) SC-1000; (b1) Cyclic performance of the sample at 0.5 A g-1, (b2) cyclic performance of SC-800 at 2 A g-1 and 5 A g-1[56]"

Fig. 10

(a) Schematic diagram of asphalt and resin co-carbonization[62]; (b) The second cycle charge-discharge curve of carbon material[62]; (c1) Initial constant discharge/charge curve of hard-soft carbon composite at 30mA g-1; (c2) Rate properties of hard-soft carbon composites at 30-1200 mA g-1; (c3) Cyclic properties of hard-soft carbon composites at 150 mA g-1[63]; (d) Raman spectra of FP-1000 and MP-1000 (d1); FP-MP-1000 samples in different proportions (d2); Sample FP-MP 5:2 at the different carbonization temperature (d3)[63]"

Fig. 11

(a) Preparation process of HC-SC composites (a1) and cyclic stability of HC-SC, HC and SC at 500 mA g-1 (a2) [64]; (b) Schematic diagram of preparation of asphalt-derived carbon nanofibers (NFC) [65]"

Fig. 12

(a) Synthesis process and structure diagram of CPP and CPOP[66]; (b) First-circle discharge curves for HCP, HCPOP-air3 and HCPOP-ox12; (c) C/20 and C/10 rate performance and 20-cycle stability[67]; (d) Schematic diagram of preparation process of amorphous carbon[68]"

Fig. 13

(a) Schematic model of the oxygen fuctional groups in MCF750[69]; (b) The charge/discharge curves of the MCF750 at 0.1 A g-1[69]; (c) Fe0.25H transmission electron microscope image[70]; (d) Rate performance diagram of FexH material[70]"

Table 1

Electrochemical properties of negative electrodes of soft carbon materials under different strategies"