Three-Dimensional Self-Supporting Lithiophilic Materials For High Performance Lithium Composite Anode

Li metal,which has a high theoretical specific capacity(3860 m Ah g^-1)and lowest redox potential（-3.040 V vs.SHE）,is considered to be one of the most promising anode material for next-generation Li ion-based batteries.However,their practical applications are limited by problems such as uncontrollable lithium dendrite growth and infinite volume changes during cycling.Focused on the problems of lithium dendrite and electrode pulverization,we propose an effective strategy to modify lithium metal anode through designing lithiophilic 3D skeleton.Detailed work as follows:（1）A rational design of 3D structured lithium metal anodes comprising of hairy cobalt-decorated three dimensional carbon nanofiber composite is demonstrated via electrospinning and continuous heat treatment.The lithiophilic cobalt can induce lithium even deposition,meanwhile,the porous and free-standing scaffold can enhance the tolerance to stresses resulting from the intrinsic volume change during Li plating/stripping and reducing local current density,delivering a significant boost in both charge/discharge rates and stable cycling performance.Therefore,the composite anode can be stable circulated for 200 cycles under the current density of 4 m A cm^-2.When the composite anode was used to assemble a full cell with commercial cathode Li Ni_0.5Co_0.2Mn_0.3O₂,excellent cycling performance and rate capability were achieved.（2）A mechanically-stable and resilient Li metal host was fabricated by covalently cross-linking a highly-conductive and lithiophilic MXene/silver nanowire scaffold through a silylation reaction between MXene nanosheets and polysiloxane.Compared with the control sample（an MXene scaffold assembled by weak van der Waals forces）,the covalently cross-linked MXene scaffold displayed excellent mechanical strength and resilience,which is conducive to buffer the large internal stress fluctuations generated during rapid and deep lithium plating-stripping and guaranteed that the integrated framework structure was maintained during long-term charging-discharging cycles.When used in a symmetric cell,the lithium composite anode based on the covalently cross-linked MXene host afforded an unprecedented cyclic lithium plating-stripping stability of a record-high 3000 h（3000 cycles）lifespan at an ultrahigh current density(20 m A cm^-2)and areal capacity(10 m Ah cm^-2).When this composite anode was coupled with a Li Ni_0.5Co_0.2Mn_0.3O₂ cathode,the full cell delivered an ultrahigh rate of10C for up to 1000 cycles,with an average capacity decay of only 0.043%per cycle and a stable Coulombic efficiency of 98.7%.（3）Low-cost cabon fiber（CF）as the conformal scaffold was used to prepare the lithiophilic Sn O₂@CF material by one step infiltration method.The lithiophilic 3D porous and conductive framework can construct homogeneous Li deposition on the surface of structured electrode and accommodate the volume change during Li plating/stripping,thus leading to a significant boost in both charge/discharge rates and cycling stability.When used in a symmetric cell,the lithium composite anode based on the Sn O₂@CF host afforded 400 stable cycles at an ultrahigh current density of 3 m A cm^-2 and an areal capacity of 3 m Ah cm^-2 with a stable Coulombic efficiency above99.0%.When this composite anode was coupled with a Li Ni_0.8Co_0.1Mn_0.1O₂ cathode,the full cell can maintain discharge capacity above 80 m Ah g^-1 after 200 cycles at 5C,and the coulombic efficiency is as high as 100%during the entire cycle.