Lithiophilic-Gradient, Li⁺ Supplementary Interphase Design for Lean Lithium Metal Batteries

The practicability of anode-less/free lithiummetal batteries (LMBs) is impeded by unregulated dendrite formation on thedeposition substrate. Herein, this study presents a lithiophilic-gradient, layer-stacked interfacial design for the lean lithium metal battery (LLMB) model. Engineered via a facile wet-chemistry approach, the high entropy metalphosphide (HEMP) particles with tunable lithiophilic species are dispersedwithin reduced graphene oxide (RGO). Moreover, a poly (vinylidene fluoride co-hexafluoropropylenepolymer) (PVDF-HFP), blended with molten Li at the tailorable amounts, forms aLi supplementary top layer through a layer-transfer printing technique. Theintegrated layer (HEMP@RGO-MTL@PH) not only regulates the dendrite-free lithiumdeposition towards the Cu substrate up to 10 mAh cm^-2, but also maintains robust cyclability of the symmetric cell at 5 mA cm^-2 even under 83% depth of discharge. As pairing the modified Cu foil with the LiNi_0.8Mn_0.1Co_0.1O₂ cathode (NCM811, 16.9 mg cm^-2, double sided, N/P ratio of 0.21) in the 200 mAh pouch cell, achieves gravimetric energy densities of 414.7 Wh kg^-1, power output of 977.1 W kg^-1, as well as highly reversible phasic evolutionmonitored in operando. This gradient interfacial strategy can promotethe commercialization of energy/power-dense energy storage solutions.