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Page 22 of 35 Tao et al. Energy Mater 2022;2:200036 https://dx.doi.org/10.20517/energymater.2022.46

Figure 11. (A) In-situ optical microscopy visualization of bare Li (left column) and graphite fluoride-LiF-Li (right column) electrolyte
interface in different time periods during cycling on symmetric cells (reproduced with permission from [162] ). Comparison between bare
Li and Li/graphite interfacial behaviors with SSE pellet. SEM images of (B) Li-C/SSE and (C) bare Li/SSE interfaces and (D-G) elemental
mappings of the Li-C/SSE interface (reproduced with permission from [163] ). (H) Cross-sectional SEM image and (I) high-magnification
cross-sectional SEM image of Li-Mg alloy melted on the SSE and (J) corresponding elemental mapping by EDX at the interface
(reproduced with permission from [164] ). (K) Schematic of molten Li wetting behavior for pure SSE and ALD-Al O -coated SSE,
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respectively, and l) SEM images of the SSE/Li metal interface [without ALD-Al O coating (left) and with ALD-Al O coating (right)]
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(reproduced with permission from [165] ).
Organic polymer electrolytes
Although various protective interlayers have been successfully introduced into the SSE/anode interface to
effectively decrease the interfacial resistance, the generation of unnecessary side reactions and elemental
infiltration during cycling has a potentially negative impact on the performance of ASSLSBs . Therefore,
[172]
the introduction of PEO-based electrolytes with high ionic conductivity, excellent mechanical stability and
good thermal stability between the Li metal and inorganic SSEpromises a significantly increased contact
area for the electrolyte/electrodes [173-176] . For example, an adaptive buffer layer (ABL) consisting of low
molecular weight polypropylene carbonate, PEO and lithium salt was proposed to make an intimate
interfacial contact between the solid polymer electrolytes and Li metal anode during battery cycling
[175]
because the ABL has high viscosity and ionic conductivity. Yu et al. demonstrated that introducing a 3D gel
polymer electrolyte at the interface between Li Al Ge (PO ) pellets and lithium metal anodes can reduce
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1.5
4 3
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[175]
interfacial resistance and suppress the volumetric change of the anodes during cycling . It has been
reported that a PEO-based solid polymer electrolyte-coated diatomite-derived lithium silicide-Li composite
can act as a hierarchically structured, stable and dendrite-free Li metal-based hybrid anode for high-
performance ASSLSBs . Overall, the PEO-based layer can resist the side reactions between solid
[176]
electrolytes and lithium to some extent ; however, it is noteworthy that Li metal may destroy the PEO-
[177]
based protective layer because of its reducibility. Thus, it could be expected that more effective strategies will
be developed for constructing suitable interfaces between Li anodes and SSEs .
[178]
Others
A novel wetting agent, namely, a 1.5 M LiTFSI/Pyr TFSI ionic liquid, was successfully employed to enhance
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the interfacial stability between the Li SnP S solid electrolyte and Li metal interface and the cycling
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performance of symmetric cells . Recently, a 3D electronic and ionic mixed conducting interlayer
[36]
composed of a Sn/Ni alloy layer-coated Cu nanowire network showed the capability to improve the