# Recent Advances in Lithiophilic Porous Framework toward Dendrite-Free Lithium Metal Anode
## 2 Metal-Based Li Host
### Lithium  
Lithium metal itself can be constructed as the Li host in the form of a nano/microstructured framework. [PERSON] et al. designed defects in the lithium foil using the microneedle technique shown in Figure 1a to introduce high surface areas that serve as preferred sites for Li plating [17]. The other methods of producing microstructured Li include soft lithography, where continuous surface relief (CSR) and discontinuous surface reliefs (DSR) were fabricated on the surface of the Li metal foil electrode [18]. The continuous and discontinuous 10 um deep surface modifications on 20 um thin Li electrode as shown in Figure 1b,c provides an effective way to replace the use of excess Li. [PERSON] et al. pressed the Li powder with a particle size of fewer than 20 um on stainless steel mesh Figure 1d to create a porous Li-powder anode [19]. The porous anode with 25% Li loading eliminates the growth of Lidendrites. Later, [PERSON] et al., introduced micropatterns on lithium metal using micrometer-scale pyramid reliefs (height-50 \(\upmu\)m, width-50 \(\upmu\)m, and ridge length-40 \(\upmu\)m) [20]. During stripping, the original dimension was recovered draining the liquid-like/or granular like plated Li from such structures as shown in Figure 1e,f. The coating of the micrometer particle size Li powder (CLiP) on the copper foil as shown in Figure 1g can also be done to improve the battery performance and replace the excess Li foil electrode [21]. This study shows that the porous structure and high surface area of the coated/pressed Li powder significantly reduce the current density during plating/stripping. The CLiP introduced the safety and practical battery operation at a lean lithium condition. To further enhance the self-healing electrostatic shield mechanism, [PERSON] et al., employed an electrolyte solution containing cesium hexafluorophosphate CsPF\({}_{6}\) (0.05 M) into micropatterned LMA [22]. The cesium ions form a positively charged electrostatic shield around the initial growth of protrusions, which obliges the deposition of Li adjacent to the protrusions leading to dendrite-free Li deposition [23,24]. Figure 1h,i show the cross-section SEM image of micropatterned Li without and with CsPF\({}_{6}\). The micropatterned Li metal shows the uncontrolled granular Li deposition. In contrast, the micropatterned Li with CsPF\({}_{6}\) modifications shows the dendrite-free and stabilized Li metal anode. Figure 1: Micropattern preparation process and Li deposition morphology on porous Li. (**a**) Schematic demonstration of the microneedle technique. Reproduced with permission from [17], John Wiley and Sons, 2014. (**b,c**) SEM images of continuous surface relief (CSR) and discontinuous surface relief (DSR) on the Li electrode. Reproduced with permission from [18], American Chemical Society, 2019. (**d**) SEM  
image of the Li-powder electrode. Reproduced with permission from [19], Institute of Physics Publishing, 2012. (**e,f**) SEM images of Li plated and stripped. Reproduced with permission from [20], John Wiley and Sons, 2016. (**g**) SEM image of the coating of the micrometer particle size Li powder (CLiP) electrode. Reproduced with permission from [21], John Wiley and Sons 2013. (**h,i**) Cross-section SEM images of patterned Li without and with CsPF\({}_{6}\). Reproduced with permission from [22], Elsevier, 2018. (**j,k**) Schematic illustration of the preparation and Li plating/stripping on the Li/Li-Sn composite electrode. Reproduced with permission from [25], Springer Nature, 2020. The battery operation at a higher rate demands low effective current density and fast lithium-ion diffusion kinetics. The nanostructured electrode lower effective current density and the lithium-containing alloys can facilitate the faster lithium-ion diffusion. Recently, [PERSON] et al. reported an interpenetrated 3D lithium metal/lithium tin alloy nanocomposite by a simple calendaring and folding route and lithium-tin alloying reaction mechanism as shown in Figure 1j [25].