Fig 1

An overview of the corresponding scientific problems of lithium metal anodes in liquid or solid electrolyte systems at multiple spatial scales. EDL: electronic double layer. SEI: solid electrolyte interphase."

Table 1

Fundamental information of advanced characterization technologies for lithium metal anode."

Fig 2

Characterization techniques for lithium metal anode in multiple spatial scales."

Fig 3

(A) Schematics about sample preparation of cryo-TEM, the related result of (B) crystal orientation and (C) grain boundary of Li dendrite 38; (D) cryo-TEM images of Li microspheres deposits with the corresponding HRTEM images and the measured lattice spacing of them, and TEM images of Li dendrite with SAED patterns 39; multiple crystalline grains in the (E) bare and (F) Li2S added Li|PEO interphase and Li crystal orientation characterized by HRTEM 40; (G) TEM images of the electrodeposited Li as a function of the electron radiation dose at 300 and 100 K 42. Adapted from American Association for the Advancement of Science, Springer Nature, Wiley and American Chemical Society publishers."

Fig 4

(A) AFM image of the variation of Li particle size in the same area 43; (B) surface roughness and electronic conductivity of bare and Cu3N-modified Cu foil at pristine state and after first lithium plating and stripping processes 47; (C) topographic height and adhesion mapping images of the surface of the Li electrode during electrochemical deposition 44. Adapted from American Chemical Society publisher."

Fig 5

(A) Schematics of in situ TEM and the electrochemical liquid cell, and (B) the growth process of Li dendrite on Li-Au alloy anode 48; (C) HAADF images of Li deposition and dissolution 49; (D) in situ TEM liquid cell with 10 electrodes, (E) operando STEM images of Li deposition and nucleation 53. Adapted from American Chemical Society publisher."

Fig 6

(A) Cross-sectional SEM images of the Li anodes obtained from the cells after 100 cycles under different rate 10; (B) voltage profile shape and morphological evolution of dead Li layer under SEM 32; (C) the influence of ALD modified surface on Li deposition 56; (D) cracks of Ti electrode caused by Li deposition 55. Adapted from Wiley, Royal Society of Chemistry, Elsevier, and American Chemical Society publishers."

Fig 7

(A) 3D reconstruction images of voids and bulk Li metal after the first electrochemically deposition in different electrolytes 30; (B) a time lapse series of SEM images of lithium plating and stripping 57; (C) a schematic illustration of a Li|Li symmetric cell under SRS imaging, 3D images showing depletion of ions near the anode surface, and correlation between local Li growth and local Li+ concentration displayed by 2D overlapping images 68. Adapted from American Chemical Society, Wiley, Springer Nature publishers."

Fig 8

(A) In situ glass capillary cell and flocculent lithium dendrite growth 9; (B) in situ morphological observation of surface patterned Li electrode during cycling 60; (C) setup and cell configurations for the NDP measurement, and in situ measured spectra of a Li/garnet/CNT asymmetric cell while cycling 65; (D) schematics and spectra contour map of in situ NDP revealing Li deposition behavior of an ASSLMB with 3D Ti electrode 55. Adapted from Royal Society of Chemistry, Elsevier and American Chemical Society publishers."

Fig 9

(A) Experiment setup of Nano-CT; (B) 2D slices and 3D reconstruction images of Li morphologies at 5, 33 ℃ and low/high current density 54; (C) schematic and photograph of the Li|Li cell used in XCT and the characterization of bulk and mossy Li 58; (D) images and schematic of formation and evolution of pits during Li stripping and plating 75; (E) schematics of setup and cell of XCT with the observed uneven Li deposition and separator deformation 69. Adapted from American Chemical Society and Royal Society of Chemistry publishers."

Fig 10

(A) 2D XCT slices of the Li metal polymer batteries before and after cycling 89; (B) XCT results comparing defect-driven and fabrication-related modes of cell failure 90; (C) design of the in situ solid-state Li symmetric cell allowing control and monitoring pressure during cycling; (D) Li detected in Li6PS5Cl by XCT after shorting 91. Adapted from Institute of Physics, American Chemical Society and Wiley publishers."

Fig 11

(A) Schematics of synchronized electrochemical/video microscopy setup, (B) Li dendrite growth in different kinds of electrolyte, (C) Li deposits morphology and corresponding voltage trace profile 62; (D) through-plane cycling in LLZO with operando cross-sectional visualization; (E) operando optical images at different time during Li plating 64; (F) effective volume calculation method and volume tracking profile of four individual dendrites throughout the first cycle 63; (G) in situ lithiation of solid electrolytes during XPS surface analysis and the related XPS results 76. Adapted from American Chemical Society and Cell publishers."

Fig 12

(A) Schematic of the cell used for in situ magnetic resonance imaging, and time series showing the evolution of the 7Li electrolyte concentration profile and chemical shift image of Li metal 77; (B) three-dimensional segmented images of the in situ NMR cell at different charging time 78; (C) 3D evolution of Li distribution at different stages of cycling, and 2D evolution of the Li distribution as a function of charging time based on the normalized neutron radiographs 80. Adapted from American Chemical Society and National Academy of Sciences publishers."