Helical Counter-Directional Migration-Induced Solvation Sheath Constructing Reinforced Electrode-Electrolyte Interphases for Ultra-Stable Anode-Free Lithium Metal Batteries

Abstract

Anode-free lithium metal batteries hold great promise for high-capacity energy storage by eliminating both the conventional graphite anode and any excess lithium metal. However, irreversible charge-discharge cycles lead to the rapid depletion of active lithium inventories. Moreover, the ether-based electrolytes suited for anode-free configuration are unstable at high voltages, which makes them incompatible with high-nickel cathodes and ultimately curtails their role in enhancing energy density. This study proposes an interface modification strategy driven by helical counter migration. During the formation process, ion movement pathways and anions-cations association effects regulated by internal force generated by a magnetized nickel-coated current collector synergistically guide anions into solvation structures of the adjacent lithium ions migrating in the opposite direction, thereby forming a mechanically robust ion-permeable solid electrolyte interphase, which is characterized by an ordered inorganic particle skeleton infused with organic components, similar to the structure of reinforced concrete. Consequently, the helical counter-directional migration-assisted copper electrode achieves a coulombic efficiency of 99.9%. The assembled anode-free Cu||LiFePO4 cell maintains over 80% capacity retention after 200 cycles, and the anode-less Cu||LiFePO4 cell sustains stable operation for over 1,000 cycles. Furthermore, the internal electric field drives helical counter-directional migration-induced anion-derived solvation sheaths to diffuse to the cathode side and optimize the cathode-electrolyte interphase, enabling stable operation of high-nickel cathodes. The anode-free Cu||NCM811 cells cycled at 4.5 V exhibit a capacity retention exceeding 75% after 100 cycles, and realize a 453.5 Wh kg-1 anode-free lithium metal pouch cell configuration.