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Tao et al. Energy Mater 2022;2:200036 https://dx.doi.org/10.20517/energymater.2022.46 Page 17 of 35

conductivity of cathodes, increasing the contact area at the cathode/SSE interface and decreasing the
interfacial resistance. However, the conductivity of sulfur-based electrodes could not be significantly
enhanced by simply mixing carbon and SSEs with sulfur. The low interfacial resistance seriously depends on
the component and preparation method of composite cathode materials [Figure 10 and Table 3].

Constructing composites consisting of Li-ion conductors, electronic conductors and sulfur-based active
materials
Ball milling is a technique that can provide the mechanical energy to break the order of a crystalline
structure, decrease the particle size of electrode materials, prepare an intimate contact and generate a
favorable interface between the active material, conducting additive and Li-ion conductor. Therefore, ball
milling has intensively been employed to prepare various sulfur-based cathode composites of ASSLSBs,
[121]
including S/Cu S/acetylene black (AB)/80Li S/20P S [120] , sulfur/poly(ethylene oxide) (PEO)/AB ,
2 5
2
2
S ) , Li S/80Li S/20P S /Cu ,
S/carbon/PEO/acetonitrile , S/AB/thio-LISICON (Li Ge 0.25 P 0.75 4 [123] 2 2 2 5 [124]
[122]
3.25
[128]
[125]
80Li S/20P S -Cu , S/AB/80Li S/20P S [149] , Li S/AB/80Li S/20P S [127] , S/graphite , sulfur/carbon/thio-
2
2
2 5
2 5
2
2
2 5
LISICON , vapor-grown carbon fiber (VGCF)/S/ionic liquid/α-Li PS 4 [130] , sulfur/activated carbon/P S [131] ,
[129]
2 5
3
[132]
S
s
s u l f u r / s u p e r P carbon/Li P S Br , u l f u r / A B / 7 5 L i S · 2 5 P S 2 5 [116] , - C/Li P S C l / s u p e r P ,
[133]
5
5
2
6
6
S/C/Li P Mn S I [116] , S-graphene oxide/Li Si P S Cl /carbon black , Li S-VGCF/78Li S·22P S
[99]
2
7 2.9
1.74 1.44 11.7
0.3
2
2 5
9.54
0.1 10.7 0.3
[84]
/Ketchen black conductive carbon , reduced graphene oxide-S/Li GeP S /AB , S/AB/70Li S·30P S [134] , Li 2
[83]
2 5
10
2
2 12
S/super P carbon/VGCF/70Li S·30P S [137] , S-C-FeS /Li PS -LiI , S-carbon nanotubes/multi-wall carbon
[150]
2 5
2
3
4
2
[138]
[139]
nanotubes/78Li S·22P S [137] , S/3,5-divinylbenzene copolymer , S-C/super P carbon/Li PS Br , S-carbon
6
5
2 5
2
[151]
nanotubes/AB/Li GeP S [45] and S-mesoporous carbon/thio-LISICON . According to these results, it can
2 12
10
be concluded that composite cathodes benefit from improved diffusion, larger contact area, increased
electronic and ionic conductivity and more suitable interfacial compatibility caused by ball milling, which is
actually required to increase the contact area of electrode materials, decrease the interfacial resistance and
enhance the performance of batteries.
Furthermore, other methods are employed to synthesize the composite cathode materials. For example, a
series of sulfur-rich composite cathodes containing S and Li PS prepared by solution reactions in
3
4
tetrahydrofuran show good ionic conductivities and high electrochemical reversibility during cycling ,
[140]
because the reaction between elemental sulfur and PS anion can generate a new family of sulfur-rich
3-
4
-6
compounds with high lithium-ion conductivity (10 -10 S cm ). In order to improve the ionic conductivity
-5
-1
of Li S cathodes, the core-shell nanostructure of Li S (core )-Li PS (shell) was fabricated by a solution-based
3
2
2
4
reaction and the reduced interfacial resistance and improved performance of batteries could be attributed
[141]
to the innovative nanostructured materials. A favorable interface between the S-C composite cathode and
LiBH electrolyte could be realized by cold pressing, which allows for three-dimensional (3D) charge
4
transfer in the cathode . Homogeneous nanocomposite electrodes consisting of Li S, carbon and
[142]
2
polyvinylpyrrolidone prepared by a novel bottom-up method show outstanding mechanical and conducting
properties . This is because the resulting nanoscale mixed-conductive network, consisting of ionic
[143]
conductive SSEs and electronic conductive carbon, can effectively maintain the intimate contact between
the cathode and electrolyte and improve the electronic conduction and Li-ion diffusion of the electrode.
Introducing sulfur into the porous carbon replicas can form a 3D carbon matrix framework structure with
[129]
high electronic conduction using a gas-phase mixing method , which exhibits an improved battery energy
density.
A novel Li La Zr O nanoparticle/porous carbon foam synthesized by the one-step facile Pechini sol-gel
3
7
12
2
method can serve as an ion/electron conductive matrix to construct a high-performance S-based
cathode . The structural framework of graphene oxide/polyethylene glycol prepared by an esterification
[144]