Achieving stable lithium metal anode via constructing lithiophilicity gradient and regulating Li3N-rich SEI

Abstract

Three-dimensional (3D) current collectors are studied for the application of Li metal anodes in high-energy battery systems. However, they still suffer from the preferential accumulation of Li on the outermost surface, resulting from an inadequate regulation of the Li + transport. Herein, we propose a deposition regulation strategy involving the creation of a 3D lithiophilicity gradient structure of MoN on Cu 3 N nanowire-grown Cu foam (MCNCF) to induce a “bottom-up” Li deposition. During the initial Li deposition, the reaction between Li and Cu 3 N leads to the formation of Li 3 N while the lithiophilic MoN located at the bottom promotes the downward Li + migration, resulting in the generation of a Li 3 N gradient. Such a “bottom-up” Li 3 N distribution results in the formation of a stable and Li 3 N-rich solid electrolyte interphase (SEI) layer, facilitating the Li⁺ transport and promoting a uniform Li nucleation. Computational simulations and experimental results corroborate the preferential deposition of Li on the bottom of the substrate, leading to a uniform Li nucleation and growth throughout the electrode. The MCNCF electrode offers a significantly improved reversibility of the Li deposition, achieving a lifespan of more than 1200 h at a current density of 1 mA cm −2 in symmetric Li||Li cells. Furthermore, full-cells incorporating MCNCF@Li as the negative electrode and LiFePO 4 (LFP) cathodes exhibit outstanding electrochemical performance with a capacity retention of over 99.5% after 250 cycles at 1 C, which significantly surpasses the performance achieved with CF@Li or CCF@Li electrodes. This innovative design strategy for 3D metallic current collectors, featuring a lithiophilicity gradient, provides new perspectives for the development of stable Li metal anodes and, as a result, for the advancement of Li-metal batteries. The MCNCF lithiophilic nitride gradient results into a Li 3 N-rich gradient SEI layer after the initial cycle, which, by enhancing Li⁺ transport and uniform Li nucleation, enables a significantly enhanced rate performance and long-term cycling stability of the negative electrode as well as Li/ LiFePO 4 and Li/LiNi 0.8 Co 0.1 Mn 0.1 O 2 full cells. ● MCNCF hosts an in-situ formed Li 3 N-rich SEI, promoting rapid Li + diffusion. ● MCNCF favors the “bottom-up” Li deposition mechanism. ● MCNCF-based LMBs demonstrate excellent electrochemical performance.

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