Polysiloxane Cross‐Linked Mechanically Stable MXene‐Based Lithium Host for Ultrastable Lithium Metal Anodes with Ultrahigh Current Densities and Capacities

Abstract The applications of lithium metal anode are limited by uncontrollable lithium dendrite growth and infinite volume changes during cycling. These fundamental issues are exacerbated at high cycling current densities and capacities. Herein, a mechanically stable and resilient lithium metal host is 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 displays 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 is 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 affords an unprecedented cyclic lithium plating‐stripping stability of a record‐high 3000 h lifespan at an ultrahigh current density (20 mA cm −2 ) and areal capacity (10 mAh cm −2 ). When this composite anode is coupled with a LiNi 0.5 Co 0.2 Mn 0.3 O 2 cathode, the full cell delivers an ultrahigh rate of 10 C for up to 1000 cycles, with an average capacity decay of 0.043% per cycle and a stable Coulombic efficiency of 98.7%.