Figure 3 (a) Schematic of the microstructure and fabrication
process of the Lix M/graphene
foils. (Reproduced from
ref.[39], with permission from Copyright © 2017 Macmillan Publishers
Limited, part of Springer Nature.) (b) Schematic representation of 3D
Li-coated PI alloy electrode. (Reproduced from ref.[100], with
permission from Copyright © 2016 Springer Nature.)
3.2 | Lithium alloys matrix
Equations
By confining Li in a 3D structure, the infinite volume change during
cycling could be eliminated[101]. Furthermore, the high surface area
provided by 3D structures can further lower the localized current
density and enable a more stable plating/stripping process[26]. Even
confining the lithium metal in 3D carbon materials is a more common
strategy, there are still some pioneering works on using the 3D lithium
alloys matrix to host the lithium metal[26, 37, 102].
In 2014, Zhang’s group first employed a 3D lithium alloys
(Li7B6)
fibrous matrix for ultra-stable lithium-sulfur batteries[37]. The 3D
nanostructured Li7B6 framework with high
surface area and enough volume space, could not only decrease the areal
current density, but also adequately accommodate the electrolyte and
re-deposited Li to stabilize the concentration of Li ions. By employing
this Li@Li7B6 anode, the Li-S batteries could stability
cycle to 2000 cycles. Recently, Yan and his co-workers reported a 3D Mg
doped LiB skeleton for hosting the metallic lithium and inhibiting the
lithium dendrite growth as shown in Figure 4a and 4b [102]. The 3D
LiB skeleton could significantly reduce volume variation during Li
electrochemical dissolution/deposition process. Its superior
lithiophilic and conductive characteristics could also contribute to the
reduction of the local current density and homogenization of incoming
Li+ flux. More importantly, Yan et al., used the
Density Functional Theory (DFT) calculation proved the doping of Mg
element to the 3D LiB skeleton could enhance the adsorption energy of
Li. And the remaining Li-deficient Li-Mg alloy forming after Li stripped
can help connect LiB fibers to stabilize the whole skeleton and lower
interfacial resistance, which could effectively inhibit the lithium
dendrite growth as shown in Figure 4c and 4d.