Construction Of 3D Lithiophilic Conductive Framework And Performance Research Of Composite Lithium Metal Anode

Lithium?Li?metal anode is widely considered to be the most promising anode material for lithium battery due to its ultrahigh theoretical specific capacity of 3860 mAh g^-1 and the lowest redox potential?-3.04 V vs standard hydrogen electrode?among all the anode materials.However,the Li metal anode suffers from a series of problems such as rapid capacity decay,reduced Coulombic efficiency,and short circuit of the cell owing to the uncontrollable dendrite growth and the unstable solid electrolyte interface during the stripping/plating process.As a host-less anode material,the infinite volume expansion of the Li metal anode may cause the continuous cracking and repair of SEI,and further giving rise to the formation of the Li dendrites and“dead Li”.Meanwhile,the uneven surface of the electrode will cause the nonuniform deposition of metallic Li.In this paper,we are aimed at reducing the local current density of the electrode,suppressing the volume expansion of the lithium metal anode,and reducing the nucleation overpotential of metallic Li.Herein,the lithiophilicity of the nickel foam?NF?framework are improved through the surface modifications.Composite Li anodes are fabricated via the molten Li infusion method,and the stripping/plating process together with the cycling stability of the composite Li anodes are studied.In addition,the modified lithiophilic NF framework is used as the current collector for investigating the nucleation and deposition behavior of Li metal anode.Following are the main contents of this paper:?1?The surface of the NF is in-situ decorated by Co₃O₄ nanosheet arrays through the solvothermal method and calcination method and Li-Co₃O_4/NF composite anode is fabricated via molten Li infusion method.The decorated Co₃O₄ nanosheets not only improve the Li infinity of the NF,but also decrease the local current density of the Li-Co₃O_4/NF composite anode,facilitating the uniform plating/stripping of Li.In addition,the porous structure of the NF matrix provides enough inner space for Li metal together with relieving the huge volume change during the Li plating/stripping process.Based on the above advantages,the symmetric cell based on the Li-Co₃O_4/NF composite anode exhibits a small overpotential less than 120 mV at a high current density of 5 mA cm^-2,and demonstrates dendrite-free morphology after 540 cycles.When paired with LiFePO₄ cathode,the full-cell displays a high specific capacity of 128 mAh g^-1 after 500 cycles at the rate of 2 C.?2?The NF matrix is modified by lithiophilic V₂O₅ for the first time and the Li-V₂O₅-NF composite anode is synthesized via the molten Li infusion method.The vertically growth of V₂O₅ nanobelt arrays greatly improve the specific surface area of the NF,facilitating the enhanced contact area between the molten Li and the NF,which not only improves the efficiency of the molten Li infusion process,but also reduces the local current density of the electrode,and thus facilitates the homogeneous deposition of Li.Moreover,the good mechanical strength of the NF effectively reduces the volume change of the Li metal anode,and further suppressing the dendritic Li growth resulted from the host-less plating/stripping of Li metal anode.Based on the above favorable effects,the symmetric cell with the Li-V₂O₅-NF composite anode demonstrates improved cycling stability,delivering a ultralong lifespan of 1600 h with an overpotential less than 20 mV at 1 mA cm^-2 and 1 mAh cm^-2.When coupled with Li₄Ti₅O₁₂?LTO?cathode,the Li-V₂O₅-NF|LTO full cells demonstrate batter rate performance and cycling stability,displaying a high capacity retention of 78.8%after 500 cycles at 2 C.?3?The interconnected NiF_x nanosheets decorated on NF?NiF_x@NF?is firstly synthesized by a convenient one-step fluorination strategy creatively using PTFE as the fluorine source,and the NiF_x@NF matrix is employed as the current collector of Li metal anode.The NiF_x@NF current collector has three advantages:1.The uniformly decorated NiF_x nanosheets demonstrate superior lithiophility,which can sufficiently decrease the Li nucleation overpotential and server as uniform distributed nucleation sites,inducing the subsequent Li plating process.2.The porous NiF_x nanosheets enhance the specific area of NF,which is benefit for reducing the local current density of the electrode and inhibiting the dendritic Li growth.3.The in situ generated LiF during the initial Li plating process improves the stability of SEI layer,and further promoting the homogeneous Li plating process.Benefiting from the synergistic effect of the excellent lithiophilic NiF_x coating layer and the as-generated superior LiF-enriched SEI layer,the NiF_x@NF current collector achieves dendrite-free Li plating behavior,indicating outstanding Coulombic efficiency and cycling lifespan of symmetric cell.Furthermore,excellent electrochemical performance is obtained when the NiF_x@NF current collector is utilized in full-cell testing.