Fig. 1

(a) Mechanism diagram of quantum dots; (b) Various types of quantum dots in the field of alkali metal ion batteries"

Fig. 2

(a) Schematic of the synthesis route of MQDC-SnO2/RGO[32]; (b) Schematic illustration of the fabrication process of flexible ZnO@NPCF[37]; (c) Schematic illustration of lithiation for NP CoO x QDs/C anodes[41]; (d) Chematic diagram of the lithiation/delithiation process of the Ga2O3-QD@NC electrode[42]"

Fig. 3

(a) Low magnification TEM image of ZnS-QDs@mNC[54]; (b) Schematic illustration of ZnS-QDs@mNC before and after lithiation[54]; (c) Schematic illustration of the three main effects on WS2-PCNF10 for boosting ultrafast lithium storage performances[55]; (d) Schematic illustration of the reversible SEI layer formation on the CoS x @NSC-1 electrode[56]; (e) Specific capacities of the NSC and CoS x @NSC-y electrodes at varied current densities[56]"

Fig. 4

(a) Schematic representation of the Na+ storage mechanism for TiN/C composite anodes[61]; (b) Schematic illustration of lithiation and delithiation mechanisms for VN-bulk NPs, VN@NC NPs and VNQD@NC HSs[62]; (c) Cycling performance of VN-QDS/CM-600 at 0.5 A/g[63]; (d) TEM images of VNQD with NH4VO3[64]"

Fig. 5

(a) Schematic of the structures of CDs[67]; (b) Adsorption patterns for on four ions on C24H12, two ions on C24H12, five ions on C54H18, three ions on C54H18[68]; (c) TEM images of the GQDs@CNT[69]; (d) Schematic diagrams showing the formation of the hierarchical LTO/N-GQD/Super-P structure[71]; (e) Rate capability of pristine LTO and LTO-NGQ20 electrodes from 0.2 C to 50 C[71]"

Fig. 6

(a) Illustration the advantage of surface functional group-tailored BN-CQD structure[73]; (b) Schematic diagram of CDs@rGO stacked models[74]; (c) Schematic of the preparation process for LAP-rGO-CDs[75]; (d) Schematic illustration of the three main effects on the F-CQD@etched-Cu electrode for improving ultrafast cycling[78]"

Fig. 7

(a) Schematics of the lithiation and subsequent delithiation process of the 3DOP Ge@N-C anode and Ge/N-C anode[79]; (b) The difference charge density of SbQD@C at the heterogeneous interface (e/?3)[80]; (c) Proposed mechanism of the B@rGO anode during the lithium storage process; and schematic diagram of the stacked models at the cross-section[84]"

Fig. 8

(a) Schematic illustration of Ni2P@NPC building-up process[88]; (b) Schematic illustration of the mechanism of the superior performance of 0D/2D SnSe@f-Ti3C2 composites[91]; (c) Li+ diffusion path of Fe2O3/MoO3@N[93]"

Table 1

Electrochemical properties of quantum dots and their composite materials"