Efficient Charge Redistribution Achieved by 3D Micromagnetic Fields for Dendrite‐Free Lithium Metal Batteries

Abstract Lithium metal batteries (LMBs) provide exciting potential to enhance the energy density beyond 500 Wh kg −1 due to the high theoretical capacity and low reduction potential of metallic lithium (Li) anodes. However, intrinsic issues of Li metal anodes, such as non‐uniform Li growth, unstable solid‐electrolyte interphase (SEI), and large volume changes, rapidly degrade the cyclability of LMBs. Herein, an efficient charge redistribution strategy to realize dendrite‐free LMBs is presented, which takes advantage of multidirectional magnetohydrodynamics (MHD) effects generated by 3D micromagnetic fields. To realize such experimental design, a core–shell structured Cu–Ni nanonecklace (CN‐NK) are synthesized as a functional coating material on a separator. Compared to core–shell Cu–Ni nanowires with a straight elongated morphology, necklace‐shaped CN‐NK can diversify magnetic moments, generating 3D micromagnetic fields and thus amplifying MHD effects. As verified by computational fluid dynamics simulations and electrochemical analyses, strong multidirectional MHD effects induced by CN‐NK can not only homogenize ionic concentrations and electric field, but also enhance overall mass transport kinetics. As a result, CN‐NK‐coated separators promote ultra‐dense Li nucleation, induce a salt‐derived SEI enriched with LiF, and reduce energy barriers for Li plating/stripping, collectively enhancing the cyclability of LMBs with high‐loading LiFePO 4 and LiNi 8 Co 1 Mn 1 O 2 cathodes.