# Recent Advances in Lithiophilic Porous Framework toward Dendrite-Free Lithium Metal Anode
## 4 Conclusions and Viewpoints  
Lithium metal-based anodes are considered a potential candidate to meet the ever-increasing energy demands. However, the serious safety and poor cycling performance of the lithium metal anode have impeded the practical application of next-generation energy storage systems. The well-designed micro/nanostructured Li host materials could effectively improve the safety concerns and efficiently boost cycling performance. The high surface area and the electronic conductivity of such a porous matrix renders a uniform electric field, buffers the Li expansion during plating/stripping cycles, and lowers the effective current density. As a result, the uniform Li-ion flux and dendrite-free Li deposition not only ensures the safety issues but also addressed the low cycling performance. However, the micro/nanostructured Li host is still not up to the challenges to thoroughly address all the issues associated with lithium metal anodes. Firstly, the lithiophobic host materials increase the Li nucleation overpotential, cannot guide the uniform Li deposition, and shows increased voltage hysteresis on continuous cycling. Secondly, the micro/nanostructured host materials occupy a larger volume compromising of the volumetric energy density, and thirdly, the high surface area needs excess electrolyte to wet the surface and expose the high area of the lithium metal to the electrolyte. This consumes both the lithium and electrolyte leading to quick capacity decay and poor CE.  
The efficient use of a 3D porous Li host can only be done with the use of lithiophilic decorations or coatings. The design of lithiophilic micro/nanostructured composite Li anode by infusing the molten lithium metal inside a porous structure can effectively address the safety and challenges in high energy-density lithium metal batteries. The use of 3D scaffolds with mechanical and chemical stability and mixed ionic conductivity can generate a robust, stable SEI, suppress the Li dendrite growth, and inhibit the side reactions between the lithium metal anode and the electrolyte. More recently, the development of 'all in one', i.e., the lithiophilic and porous Li host, is the simple and low-cost technique for enhancing the Li nucleation behavior and reducing the voltage hysteresis. The decoration of a porous framework with lithiophilic coatings or seeds allows high Li loading and dendrite-free Li deposition into such porous structures. Although it is tricky to obtain the fresh Li during the critical initial plating mechanism, further understanding of the initial Li nuclei using advanced characterization tools is necessary. The ex-situ or in-situ derived stable SEI and the use of a solid-state electrolyte along with the lithiophilic materials decorated nano/microstructured Li host can further enhance the battery cycling performance.  
Conceptualization, writing--Original draft preparation, visualization, investigation, and review and editing, R.P.; supervision and funding acquisition, Y.Z.; supervision and funding acquisition, Q.Q. All authors have read and agreed to the published version of the manuscript.  
\begin{table}
\begin{tabular}{c c c} \hline
**Lithiophilic Materials-Type** & **Examples-Forms/Structures** & **Ref.** \\ \hline organic compound coating & & [50] \\  & ZnO quantum dots, ZnO NA, ZnO layer, VA ZnO & \\ Metal oxides & NSs, NiO, CuO nanorod array, CuO-VA-NA, & [18; 19; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29; 30; 31; 32; 33; 34; 35; 36; 37; 38; 39; 40; 41; 42; 43; 44; 45; 46; 47; 48; 49; 50; 51; 52; 53; 54; 55; 56; 57;  
**Funding:** This research was funded by NSF MRI (1428992), NASA EPSCoR (NNX15 AM83A), SDBoR Competitive Grant Program, SDBoR R&D Program, and EDA University Center Program (ED18 DEN3030025).  
**Acknowledgments:** We acknowledge the support from NSF MRI, NASA EPSCoR, SDBoR Competitive Grant Program, SDBoR R&D Program, and EDA University Center Program.  
**Conflicts of Interest:** The authors declare no conflict of interest.