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Page 2 of 11 Wang et al. Energy Mater 2024;4:400031 https://dx.doi.org/10.20517/energymater.2023.103

INTRODUCTION
Lithium (Li) metal has high specific capacity (3,860 mA h g ) and the lowest electrochemical potential
-1
(-3.04 V vs. standard hydrogen electrodes), which is considered to be a potential choice for high energy
density Li-based batteries . However, the commercialization of Li metal batteries is severely limited by the
[1-4]
volume variation associated with the “hostless” bare Li anode and the uncontrolled Li dendrite growth.
Generally, hosting Li with the three-dimensional (3D) framework has been regarded as a popular method to
improve the lifespan of Li anodes [5-11] . To encapsulate Li metal in a 3D framework, thermal infusion
strategies involving introducing molten Li into a 3D matrix have been developed [12-18] . Among various 3D
hosts, carbon-based frameworks are recognized to be an ideal host architecture due to their lightweight,
high mechanical strength, excellent electrical conductivity, low-cost, and abundance in nature [19-26] . For
instance, Wang et al. proposed that molten Li can be easily impregnated into carbon nanotube (CNT)
network to form Li-CNT composites, which not only exhibit high specific capacity but also suppress Li
dendrite formation .
[27]
Remarkably, the liquid Li has high surface tension and the poor lithiophilicity of carbon materials causes the
liquid Li to display a spherical shape on the most carbon-based substrates, indicating the molten Li is
difficult to diffuse into the interior of the carbon-based skeleton, which poses an obstacle for the fabrication
of Li composite anodes [28-31] . Therefore, further modification of carbon-based hosts is required to tune the
wettability. Apparently, the binding energy among Li atoms can be reduced by some substances that can
react with Li metal to form Li compounds or alloys, thus decreasing the surface tension of molten Li and
improving the wettability . Coating lithiophilic layers have been widely employed to decorate the carbon-
[32]
based framework [33-40] . For example, Zhu et al. reported a carbon scroll, which consists of vertically aligned
[33]
carbon fibers decorated with copper oxide (CuO ) nanoparticles . The CuO can react with metallic Li to
x
x
produce Cu and Li O chemically, which facilitates the wettability of liquid Li to carbon scroll, thus enabling
2
Li metal to be well accommodated inside the skeleton. Alternatively, Wang et al. coated carbon cloth (CC)
with ZnO nanoarray to obtain 3D porous hosts . Molten Li can be infiltrated into such a 3D host rapidly
[41]
due to the enhanced wettability of liquid Li toward 3D porous CC@ZnO. Notably, the nano-scale ZnO
coating not only offers the driving force for wettability but also enables the formation of a Li-Zn alloy,
+
exhibiting an exceptionally high Li diffusion coefficient and facilitating the uniform Li deposition.
However, the Li O in situ deduced from metal oxide layers can increase the interfacial impedance and
2
[28]
prevent the substrate from being perfectly wetted by the molten Li . To avoid this shortcoming, the non-
metallic or metallic species that can react with liquid Li to produce Li O-free Li alloy have been
2
investigated [42-45] . Zhang et al. introduced Si nanowire arrays on commercial CC sheets to fabricate a
lithiophilic host . The Si nanowires enhanced the wettability due to the generation of Li Si . The same
[42]
5
22
phenomenon is repeated by Ag-coated framework. Zhang et al. found that Ag nanoparticles react with Li to
[45]
produce Li-Ag alloy, which shows favorable Li affinity . In addition, Ag nanoparticles can also act as the
lithiophilic sites, promoting the Li nucleation process uniformly. On the other hand, regulating the micro/
nanostructure on the surface of the carbon-derived substrate is also a promising strategy to improve the
wettability [46-51] . Feng et al. introduced inactive transition metal nanoparticles (Ni, Cu) onto the surface of
[47]
CC sheets to form capillary-like structure with conical gaps . When the modified CC was in contact with
liquid Li, the generated Laplace pressure forced the molten Li to diffuse into the CC at 220 °C, thereby
significantly improving the wettability. It should be pointed out that the radial length of these lithiophilic
architectures anchored on carbon-based substrate is only a few micrometers, which has relatively low
specific area and is susceptible to being buried by the deposited Li, especially under a high Li plating
capacity. This indicates that the conventional host has a limited ability to promote the Li stripping/plating
behavior, and Li dendrites will grow uncontrollably on the electrode surface after multiple cycles [38,52] .
Therefore, it is essential to design a continuous network of the lithiophilic species with the micro/nano-scale