Page 42 - Read Online

Page 26 of 35 Tao et al. Energy Mater 2022;2:200036 https://dx.doi.org/10.20517/energymater.2022.46

Figure 13. (A) In-situ observation of a micro-electro-mechanical system device nanochip using the focused ion beam to apply the
electric field (from left to right are the anode, SSE and cathode) and the (B) corresponding schematic. (C) Annular bright-field (ABF)
and (D) high-angle annular dark-field (HAADF) images of a pristine cathode annular. The corresponding line profile acquired at the red
dashed line rectangular zone is shown in panel (C) with both lithium and oxygen contrast. Lithium, oxygen and cobalt ions are
represented as green, purple and cyan balls, respectively, in panels (B) and (C). (E) HAADF image of the delithiated cathode colored in
blue using the GPA method and two orientations colored with green and red. Panels (F) and (G) are zoomed-in micrographs of the
yellow, dashed-line, rectangular area. Panels (H) and (I) are zoomed-in micrographs of the pink, dashed-line, rectangular area. For both
boundaries, a contrast in the lithium layer in both the HAADF and the ABF micrograph is shown, suggesting heavy atoms are present in
the lithium layer. The basal planes of the two crystals that meet at an angle of 112° are shown in panels (F) and (G) (reproduced with
permission from [201] ).

of sulfur and high safety make ASSLSBs more commercially viable than other battery systems and are
expected to play a key role in the future development of energy storage systems. However, their
performance promotion achieved at the laboratory level could offer a false sense of research direction,
because there is a significant gap between practical pouch cells and laboratory coin cells under realistic
conditions. Data collected from coin cell testing under ideal conditions is clearly far from the requirement
of practical applications. To guide the rational design of ASSLSB engineering, the effect of the required
performance parameters close-to-application multilayer-pouch cells on the gravimetric and volumetric
energy densities and safety should be evaluated and analyzed.

To realize practical energy densities, the thickness of both the electrode and electrolyte layers is required to
-2
be thinner than 50 μm and sulfur loading higher than 4-5 mg cm . Furthermore, scalable continuous roll-
to-roll methods are necessary for practical pouch cell manufacturing [Figure 14] ; however, few reports
[204]
on such methods to build ASSLSBs with sulfide-based solid electrolytes have been presented .
[205]
Several interesting methods have so far been proposed to efficiently promote the commercialization of
ASSLSBs, including thin-film, wet (solvent-based) and melt-casting methods. Despite their several
advantages to fabricating solid-state micro-batteries, such as the desired thicknesses, high densification and
good interface compatibility, the cost control for the extensive application of thin-film methods is very
significant [78,98,206] . In terms of the interfacial compatibility between the electrodes and electrolytes, wet
(solvent-based) methods show obvious advantages. Solid electrolytes and various components of composite
electrodes can be well mixed directly from liquid suspensions or solutions to form self-assembled films after
subsequent evaporating. It is noteworthy that the mixing protocols should be carefully considered to realize
a homogeneous distribution of SSEs and electrode materials . In addition, it is believed that the direct
[207]
solidification of the solid electrolyte into the desired shape and thickness, namely, melt casting, could be a
feasible method to improve the interface compatibility; however, its application remains uncertain because
such SSEs are required to form stable melts at low temperatures.