Layer-by-Layer Anodes With Orientation Arranged Structure Induced By Magnetic Field For High-performance LIB/SIB

With the rapid promotion and popularization of portable electronic products,high-performance lithium-ion batteries（LIBs）and sodium-ion batteries（SIBs）are inevitable for development.Transition metal oxides are expected to be used as anode materials for LIBs and SIBs due to their high theoretical specific capacity(e.g.926 mAh g^-1 for Fe₃O₄).However,the poor conductivity of Fe₃O₄ and the volume expansion during charge and discharge processes significantly reduce its battery performance.In addition to modifying the active materials,designing electrode structures to enhance the lithium storage performance and stability has gradually become a research hotspot for addressing these defects.Optimizing the electrode structure design on the basis of material modification and new material development can further improve the performance of lithium/sodium-ion batteries.In order to achieve high-performance lithium/sodium ion batteries,deeply understand the impact of electrode structure on battery performance,scientifically and reasonably design the electrode structure,and build an excellent continuous electron conduction network inside the electrode,thereby greatly improving the energy density and cycle performance of the battery.This paper specifically outlines the successful preparation of unique layer-by-layer（LBL）Fe₃O₄/carbon fiber（CF）oriented arrays induced by a magnetic field as the negative electrode for lithium/sodium-ion batteries（LIB/SIB）.In this method,Fe₃O₄ nanoparticles are deposited on carbon fibers through the sol-gel method.Under the induction of a magnetic field,Fe₃O₄/CFs are formed by alternately coating aqueous and organic active material slurries,achieving oriented arrangement and LBL structure.Due to the change in magnetic field direction,the prepared Fe₃O₄/CFs are oriented perpendicular to the next layer,significantly improving the conductivity of Fe₃O₄/CFs and increasing the Li+/Na+ storage space and diffusion channels.Thus,a high electrochemical performance was achieved:specific capacities of 1671.3 and 504.6 mAh g^-1 at current densities of 0.1 A g^-1 and 3 A g^-1,respectively;capacity retention of 83.8% and specific capacity > 420 mAh g^-1 at 3 A g^-1 after2000 cycles for LIBs.The specific capacities of 340.9 and 240.2 mAh g^-1 at current densities of 0.1 A g^-1 and 1 A g^-1,respectively;capacity retention of 69.6% and specific capacity > 420 mAh g^-1 at 1 A g^-1 after 1000 cycles for SIBs.