Fig. 1

Several typical structures of in situ optical microscope reaction cells (a) glass plate clamped type[15]; (b) glass cuvette type[16]; (c) glass tube type[17]; (d) capillary tube type[18]; (e) coin cell type[19]; (f) pouch cell type[20]; (g) electrode draped mold[21]; (h) electrode edge-to-edge mold[22]; (i) electrode face-to-face mold[24]"

Fig. 2

Typical voltage curves of intercalated lithium stages of graphite materials and the color change process of graphite particles at different lithium concentrations[26]"

Fig. 3

(a) Color change process of five graphite particles of different sizes and shapes at 0.1 C[33]; (b) color change of natural graphite single crystal flakes during the first lithium intercalation process[34]"

Fig. 4

Lithium ion transport process of commercial graphite electrodes with prefabricated defects during charging[36]"

Fig. 5

In situ Raman spectroscopic imaging of the LiCoO2 electrode cross-section during charging and discharging[38]"

Fig. 6

(a) Optical micrographs of lithium dendrite growth patterns throughout the charging cycle at three temperature conditions[45]; (b) voltage versus time at constant current applied at three temperature conditions[45]"

Fig. 7

Schematic classification of lithium depositional morphology for four major classes and twelve subclasses[46]"

Fig. 8

Morphological evolution of the i-Li island [52] (a) configuration of the optical cell with an i-Li island between the NMC and Li electrodes; (b) Li islands in the initial state (t=0 h) and intermediate states (t=3 h) during the charging phase h) optical microscope images; (c) optical microscope images of Li islands in the initial state (t=0 h) and intermediate state (t=3 h) during the discharge"

Fig. 9

The morphological evolution process of graphite anode surface and the corresponding external characteristic curves[22] (a) voltage curves of graphite during a 10 min OCV rest period for two cells; (b) local optical images of the graphite surfaces at different points in time during the OCV rest; (c) dV/dt curves associated with the two voltage profiles; (d) blue of graphite during the extended 50 min OCV rest period"

Fig. 10

Effect of electrolyte additives on the growth of lithium dendrites on lithium metal surfaces[55] (a) Li2S8 and LiNO3; (b) only LiNO3"

Fig. 11

Volume changes of the two negative active particles during charging and discharging[67] (a) a-Si0.57Al0.28Fe0.15; (b) a-Si0.64Sn0.36"

Fig. 12

The thickness variation of the NCM and graphite electrode[71] (a) optical microscope cross-sectional images of the electrode; (b) evolution of the volume expansion rate"

Fig. 13

In situ optical observation of Li deposition-induced crack formation process inside LPS solid electrolyte[76]"

Fig. 14

Evolution of strain field on graphite anode surface with lithium concentration changing[83] (a) evolution of the strain field on the surface of the graphite anode; (b) average concentration and average in-plane strain as a function of time on the surface of the graphite anode, respectively"