Magnetism-Induced Homogenization of Charge and Ionic Distributions Realized By Cu-Ni Core-Shell Nano-Necklace for Stable Lithium Metal Batteries

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One-dimensional nanostructures such as nanowires and nanobelts exhibit unique characteristics. Nano-necklace structures, in particular, have demonstrated superior properties in certain applications compared to nanowire structures due to their enlarged active sites and surface area, ample transport channels as well as, multiscale surficial roughness.Various methods exist for fabricating nano-necklace structures, including chemical synthesis, self-assembly, template assistance, and electrospinning. The method we approached was to modify the chemical reduction method in an economical, facile, and quick way for large scale synthesis. In our synthetic approach, we utilized ethylenediamine as a capping and shape-directing agent in a strong base solution, which enable the mass production of Cu-Ni core-shell nano-necklace (CNNN) with a high yield within 30 minutes. Moreover, by changing the type of basic solution, we successfully obtained Cu-Ni core-shell nanowire (CNNW) as a typical 1D nanostructure.The physiochemical properties of as-obtained CNNN and CNNW were systematically investigated. Microscopic analyses demonstrated that both CNNN and CNNW are constituted by two major components: 1) surficial Ni coating layers with a thickness of about 40 nm and 2) inner Cu clusters as a shell and a core, respectively. Experimental results suggest that CNNN exhibits much stronger ferromagnetic properties with much higher specific surface area compared to CNNN, which hold potentials for various applications.To demonstrate one of the potential applications of CNNN, we employed CNNN as a charge and ionic re-distributor for stable lithium metal batteries (LMB). The electrochemical analyses demonstrated that CNNN enabled uniform charge and ionic distributions when coated on a commercial separator, which suppresses notorious dendrite formation of Li metal anodes, due to its excellent ferromagnetic properties and enlarged active sites with Li ions. Therefore, CNNN enabled the stable operation of LMB with LiFePO4 and LiNi8Co1Mn1O2 cathode. Figure 1