Surface fluorination of nickel nanowires enabling LiF-rich nanoscale solid electrolyte interface for stable lithium anodes

Abstract

Lithium (Li) metal has become a research hotspot for anodes materials due to its ultra-high theoretical capacity and the lowest redox potential. However, the practical application of Li metal batteries is hampered by the formation of uncontrollable Li dendrites and the irreversible structural changes during long-term charge/discharge process. Developing stable Li metal anode with uniform Li deposition is highly desirable. Herein, surface fluorination of nickel nanowires enabling LiF-rich nanoscale solid electrolyte interface was demonstrated for stable Li anodes. Free-standing three-dimensional (3D) nickel nanowires (NiNWs) current collector decorated with lithiophilic NiF2 nanosheets (NiNWs@NiF2) was constructed via a simple and scalable fluorination strategy. Theoretical and experimental analysis confirmed that the lithiophilic surface of NiF2 nanosheets could reduce the Li nucleation barrier, facilitating uniform Li ion deposition. The 3D conductive NiNWs network enabled fast electron transfer and mitigated volume changes during cycling. Additionally, a LiF-rich nanoscale solid electrolyte interface (SEI) layer formed between Li and the electrolyte significantly improved the interfacial stability. As a result, the as-assembled Li-NiNWs@NiF2 symmetrical cell provides a superior electrochemical performance, maintaining stability for 2500 h at 1.0 mA cm−2 and 900 h at 5.0 mA cm−2. Furthermore, the assembled Li-NiNWs@NiF2|| LiFePO4 (LFP) full cell demonstrated exceptional capacity retention of 93.9 % after 2000 cycles at a rate of 5C. Overall, the unique structure of NiNWs@NiF2 not only offers a straightforward method for designing a 3D lithiophilic host, but also provides the concept of interfacial engineering through the in-situ construction of an artificial LiF-rich nanoscale SEI layer.