# Recent Advances in Lithiophilic Porous Framework toward Dendrite-Free Lithium Metal Anode
## 3 Non-Metal-Based Li Host
### Metal Seeds  
[PERSON] et al., studied the nucleation overpotential of Li deposition on various materials such as Au, Ag, Zn, Mg, Al, Pt, Si, Sn, C, Cu, and Ni [83]. As shown in Figure 5a, for the materials with higher solubility (such as Ag and Mg), the slope of the voltage profile becomes flat before the onset of the Li deposition. For the materials with relatively lower solubility (such as Al and Pt), the Li nucleation overpotential can be observed. The nucleation overpotential increases as the solubility of the material decreases. Figure 5b shows a clear overpotential for Li nucleation on Si, Sn, C, Ni, and Cu substrate samples. As Cu and Ni do not form an alloy with Li, they have higher nucleation overpotential. Although C, Sn, and Si form an alloy with Li, still the overpotential can be observed but is lower than Cu and Ni. In their work, the carbon shell with embedded gold nanoparticles (AuNPs) showed a CE of 98% for more than 300 cycles higher than only the Au film or only the carbon shell, which implies that the necessity of lithiophilic porous scaffold for Li metal nucleation.  
[PERSON] et al., also studied the high Li wettability of elements such as Sn, Zn, Si, and Al, which form an alloy with Li [84]. This indicates the potential battery applications of these lithiophilic elements on any kinds of Li host. The chemical potential gradient inside the CNF was introduced using higher chemical potential elements (Ni or Co) in the inner layer and lower chemical potential (Ti or W) in the outer layer forming a hollow structure [85]. The lithiophilic particles inside the hollow structure obtained a high CE of 99.6% for more than 1400 cycles at a current density of 0.5 mA cm\({}^{-2}\) and capacity 1 mAh cm\({}^{-2}\).  
[PERSON] et al., designed a Li/carbon composite anode by melt infusion of Li into the lithiophilic Si coated 3D porous carbon matrix [57]. The silicon coating and molten Li react to form a binary lithium silicide alloy that enhances the Li wettability of the entire surface and fills the porous structure. It was observed that the molten Li forms a droplet on the carbon framework. In contrast, the molten Li spread out on the surface of the Si coated carbon framework. This indicates the enhanced lithiophilicity of the porous carbon framework by Si coating. The Li/C composite anode exhibited stable Li plating/stripping cycles with an overpotential of \(<\)90 mV at 3 mA cm\({}^{-2}\) over 80 cycles. Silver (Ag) has good solubility in Li and can form an Ag-Li alloy, it has been used to enhance the lithiophilicity of porous carbon materials for improving the plating/stripping cycles and full cell cycling performance. The anchoring of Ag nano-seeds on CNFs by Joule heating [86] and electroplating of coralloid-type Ag on carbon fiber [87] have shown low voltage overpotential and long stable cycling performance.  
The conformally coated Sn on free-standing and highly flexible 3D CNFs (CNF-Sn) also provides a lithiophilic nucleation site and superior electric contact between the Li plating and conductive CNF [88]. The low energy barrier of Li-Sn alloying leads to the small nucleation overpotential of 28 mV and potential polarization of 14 mV during Li plating/stripping cycles. The schematic in Figure 5c shows the Li deposition with and without Sn coating on CNF. The poor lithiophilicity of CNF induces Li to nucleate on the hotspots, which grow like grains. The insufficient electric contact between the Li grains and CNF leads to the residual of dead Li. In contrast, the homogenous Li deposition can be attained with the CNF-Sn.