Controllable Preparation Of Lithiophilic Conductive Frameworks And Their Performance For The Lithium Metal Anode

Li metal anodes,is regarded as a“Holy Grail”electrodes for rechargeable battery,due to its ultra-high theoretical specific capacities(3860 m Ah g^-1)and the lowest electrode potentials（-3.04 V vs.H⁺/H₂）.However,the current application of Li metal anodes is limited by several major defects,including large volume change,Li dendrite disordered growth and electrode structure powder during charging and discharging process,resulting in rapid capacity decay,low coulomb efficiency,short cycle life and safety hazards for Li metal anodes.This paper starts from the skeletons design of Li metal anode,using lithiophilic materials coating modification on the Cu skeleton surfaces could modify the commercial Cu foams from being lithiophobic to lithiophilic conductive skeletons.Further studied the effect of different lithiophilic modified materials on the behavior of Li metal plating/stripping in the skeleton,to constructed a high-performance 3D support skeletons,which can effectively suppress the dendrite degradation and volume strain of Li metal anodes,and obtain a cyclic stable Li metal anodes.The main research work of this paper is as follows:（1）The NF-Cu₃P arrays was uniformly coated on the Cu foam skeleton by in-situ growth method,used as the lithiophilic conductive skeleton of Li metal anodes（NF-Cu₃P@Cu）.The lithiophilic NF-Cu₃P arrays can providing uniform and abundant Li nucleation active sites and inducing rapid nucleation and uniform electrodeposition of Li metal in NF-Cu₃P@Cu.Meanwhile,NF-Cu₃P arrays could be lithiated to form the fast-ion conductor Li₃P during the Li deposition process,which can ensure the rapid and uniform conduction of Li⁺in the skeleton and effectively inhibit the formation of Li dendrites.Therefore,the NF-Cu₃P@Cu skeleton maintains a high coulomb efficiency of nearly 99%after 200 cycles at current densities of 1 m A cm^-2 and Li deposition capacities of 1 m Ah cm^-2(1 m A cm^-2/1 m Ah cm^-2).The Li/NF-Cu₃P@Cu anodes obtained after the deposition of Li on the NF-Cu₃P@Cu skeletons has an Li deposition overpotentials of～10 m V after a stable cycles of 150 cycles（300 h）at 1 m A cm^-2/1 m Ah cm^-2;when at 2 m A cm^-2/2m Ah cm^-2,the Li deposition overpotentials and voltage polarization are lower than those of Li/Cu anodes based on lithiophobic Cu foam frameworks.（2）Further considering the ultra-high lithiophilic performance of Ag metal,a simple chemical substitution reaction was used to in situ coating a"pine needle-like"Ag hierarchical porous arrays inside the Cu foam skeleton as a super-lithiophilic conductive skeleton of Li metal anode（Ag@Cu）.The super-lithiophilic of Ag coating and the capillary action of hierarchical porous arrays structure coude enhanced the wettability of Ag@Cu skeletons to molten Li metal and promoted the rapid impregnation and uniform nucleation deposition of Li metal.Moreover,similar to nature’s bi-directional nutrient transport in pine needles forest,the"pine needle-like"structure of Ag coating can provides sufficient specific surface area and bi-continuous electron/ion conduction pathways,promoted uniform Li deposition and stripping and accelerated the electrochemical reaction process of Li metal anode,thus effectively restrained Li dendrite powderization and volume strain.Therefore,the obtained Li/Ag@Cu anodes can stable cycling for more than 500 cycles（1000 h）at 1 m A cm^-2/1 m Ah cm^-2,and exhibits an extremely low Li deposition overpotentials（～3 m V）.The Li/Ag@Cu anodes pairing with Li Fe PO₄ cathodes assembled cells could retains 129 m Ah g^-1 reversible capacities after 200 cycles at0.5 C;and pairing Li Ni_0.8Co_0.1Mn_0.1O₂ cathodes assembled cells could retains 131m Ah g^-1 reversible capacities after 200 cycles at 1 C;and assembled cells with S cathodes also showed excellent cycle stability.