Lithium metal has a high theoretical specific capacity (3860 mA h g−1) and a low redox potential. However, due to the high reactivity of lithium metal during cycling and lithium dendrite formation, the interfacial stability of lithium anode is poor. Although boron nitride (BN) nanosheets have been used as interface layers, their mechanism for stabilizing the lithium-electrolyte interface remains unclear.
Researchers from Deakin University in Australia shared the mechanism of boron nitride (BN) nanosheet sandwiching to inhibit lithium dendrite formation, enhance lithium ion transport kinetics, promote lithium deposition and reduce electrolyte decomposition. Simulations and experiments show that the desolvation process of solvated lithium ions in interlayer nanochannels is kinetically conducive to lithium deposition, and the process can achieve long-cycle stability, reduce voltage polarization and improve interfacial stability. This study provides key insights and practical guidance for designing high-performance lithium metal anodes. The research results were published in ACS Nano under the title "Interfacial Modification of Lithium Metal Anode by Boron Nitride Nanosheets".
Original link:
https://doi.org/10.1021/acsnano.3c11135
Due to its high theoretical specific capacity (3860 mA h g−1) and low redox potential, lithium metal is the most researched anode for the development of next-generation lithium metal batteries. However, lithium's high reactivity and lithium dendrite formation hinder its commercial application. The formation of lithium dendrites disrupts the solid-state electrolyte interface (SEI), resulting in increased electrolyte consumption, low coulombic efficiency (CE), poor cycling stability, and safety concerns. The stabilization of the lithium-metal interface and the control of lithium dendrites are essential for the practical application of lithium metal anodes. Lithium deposition is a critical process that affects the stability of the anode surface, including the migration of lithium ions in the electrolyte, desolvation, diffusion through SEI, and eventual reduction on the electrode surface. Each process affects the entire lithium deposition behavior. Several approaches have been explored based on different operating principles to alleviate lithium interface problems, including optimizing lithium electrodes through structural and material engineering, designing robust and effective SEIs, and facilitating lithium deposition using advanced separators or interface layers. Anode optimization can be achieved by designing lithium composites with robust structures to regulate lithium deposition and accommodate volume changes, improving cycling stability.
Recent studies have shown that the development of an interface layer that separates the lithium anode from the electrolyte can be used as an effective and potentially scalable method to achieve stable lithium anode. The interfacial layer can not only physically separate the anode from the electrolyte and inhibit the formation of lithium dendrites, but also promote lithium deposition and stripping by uniformly redistributing the lithium ion transport path and effectively adjusting the lithium ion transport kinetics. Two-dimensional nanomaterials are particularly attractive as lithium anode interfaces due to their large specific surface area, good mechanical strength, atomic thickness, solution processability, and abundant surface chemistry. Interfaces composed of insulating 2D nanomaterials such as boron nitride (BN) and C3N4 have also been widely reported. Similar to conductive insulators, these 2D insulators are often thought to facilitate lithium deposition by regulating the transport of lithium ions. All of these interface layers have different physical and chemical properties, such as electronic and ionic conductivity, thickness, orientation, and mechanical strength.
The authors investigated the effects of a 2D nanomaterial interface layer composed of insulating boron nitride (BN) and conductive reduced graphene oxide (rGO) on lithium transport, desolvation, nucleation, and plating behavior. It is found that the physicochemical properties of two-dimensional nanomaterials have a great influence on lithium deposition, and lithium deposition in the interior and surface of the rGO interface layer mitigates the formation of lithium dendrites, and lithium ions can easily migrate through the BN layer and deposit on the surface of the negative electrode, thereby improving and inhibiting lithium dendrites. In addition, the transport kinetics of lithium on the BN layer has been greatly improved. A combination of further research and simulation was used to elucidate the mechanism, revealing a partial lithium-ion desolvation process within the nanochannels of the BN interface, which improved the lithium-ion transport kinetics and reduced the plating overpotential. The surface (rGO@Li) electrodes of reduced graphene oxide doped with lithium were modified using a BN matrix interface layer, and the performance of these electrodes was significantly improved, including cycling performance, surface stability, reduced volume change, and reduced voltage hysteresis. The transfer of the BN layer on the lithium foil by a scalable rolling method demonstrates the practical application of the BN base interface layer, and the electrochemical performance of the BN-modified lithium anode (BN@Li) in both symmetrical and whole cells is significantly improved. The rational design of the interface layer of the lithium anode proves that a feasible route can be constructed to stabilize the lithium metal anode. (Text: Li Shu)
Figure 1 Schematic diagram of lithium deposition on different substrates illustrating lithium ion transport and deposition in an electrolyte by Cu electrodes coated with (a) pure Cu, (b) rGO, and (c) BN nanosheets
Figure 2 relies on the lithium nucleation of the substrate and the plating overpotential
Figure 3: Lithium deposition morphology and electrode surface properties
Figure 4: Mechanistic study of lithium-ion migration kinetics
Figure 5MD simulation of lithium ion transport through the boron nitride layer
Figure 6: Electrochemical properties of symmetrical composite lithium batteries
Figure 7: Practical application of boron nitride modified lithium anode
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