# Recent Advances in Lithiophilic Porous Framework toward Dendrite-Free Lithium Metal Anode
## 2 Metal-Based Li Host
### Copper
developed compartmented 3D Cu (150 \(\upmu\)m diameter) by an industry-adaptable technology following a series of processes, including hot lamination, laser ablation, and alkaline etching treatments [30]. The insulating polyimide (PI)-clad copper grid with lateral electric field distribution designated as E-Cu guides the Li deposition laterally within the porous scaffold of Cu (Figure 2f,g). In contrast, pristine copper (P-Cu) showed larger, thicker dendrites with an uneven surface as shown in Figure 2h,i. [PERSON] et al. used a laser microprocessing system to design VA microchannels with optimized pore radius, pore depth, and pore spacing of 5 \(\upmu\)m, 50 \(\upmu\)m, and 12 \(\upmu\)m, respectively [31]. The VA porous Cu provides a large surface area to deposit the lithium in the microchannels as shown in Figure 2j,k. The VA porous Cu demonstrated a stable CE of 98.5% for 200 cycles and voltage hysteresis of 30 mV after 50 cycles [31]. The lithium deposited porous Cu anode paired with the LiFePO\({}_{4}\) (LFP) cathode demonstrated higher capacity retention of 90% compared to the planar Cu (80%) after 100 cycles at 0.5 C.  
The other techniques such as mechanical press or folding techniques have also been reported to make a 3D Cu/Li-metal composite anode that demonstrated a high CE and a longer and ultra-high plating/stripping capacity up to 50 mAh cm\({}^{-2}\) at an ultrahigh current density of 20 mA cm\({}^{-2}\)[32; 33]. [PERSON] et al., developed the vertically oriented lithium-copper-lithium arrays composite anode developed by mechanical rolling or repeated stacking [33]. Such composite anode showed voltage hysteresis of less than 55 mV and a lifetime up to 2000 h at 1 mA cm\({}^{-2}\) to achieve a capacity of 1 mAh cm\({}^{-2}\). Figure 2: The lithium deposition behavior of Cu based porous framework. (**a,b**) Schematic illustration to prepare 3D porous Cu foil from planar Cu foil and the Li-ion flux distribution on planar and 3D Cu  
current collector. Reproduced with permission from [9], Springer Nature, 2015. **(c,d)** The comparison of the voltage profile of Li plating/stripping on 2D and 3D current collectors at a current density of 1 mA cm\({}^{-2}\) to reach a capacity of 1 mAh cm\({}^{-2}\). Reproduced with permission from [28], [PERSON] Wiley and Sons, 2018. **(e)** The comparison of cycling performance of a Li anode with 2D and 3D Cu current collector paired with the (NiCoMn)O\({}_{2}\) cathode. Reproduced with permission from [34], Elsevier, 2018. **(f)** Top-view SEM image of E-Cu after cycling of 150 cycles at 0.5 mA cm\({}^{-2}\); inset shows the magnified image of the pinhole. **(g)** Top-view SEM image of E-Cu after peeling off the upper PI film. **(h)** Top-view SEM image of P-Cu after cycling. **(i)** Magnified top-view SEM image from the selected area in **c**. The scale bars in **(f-i)** are 50 \(\upmu\)m, 50 \(\upmu\)m, 2 \(\upmu\)m, and 500 nm, respectively. The scale bar in the inset of **(f)** is 10 \(\upmu\)m. Reproduced with permission from [30], Springer Nature, 2018. **(j,k)** Schematic of the vertically aligned (VA) porous Cu and the Li deposition preferential on it. Reproduced with permission from [31], John Wiley and Sons 2017. The poor wettability of lithium towards Cu does not spread the molten Li across the surface of lithiophobic substrates, promoting the non-uniform and dendritic Li deposition. To overcome this problem, the lithiophobic surface of Cu can be converted to lithiophilic by various coatings or layers of metal [35; 36], oxide [37; 38; 39; 40; 41; 42], nitride [43; 44], oxynitride [45], sulfide[46], and phosphide [47], the addition of functional groups or doping [48; 49; 50; 51], and by an increase in temperature [52]. [PERSON] et al., studied the tuning of Li wettability by reacting molten lithium with elemental additives and organic compounds containing functional groups [50].