Adv. Energy Mater.｜Wave-structured MXene thin films eliminate tip discharge effect in lithium metal anodes

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Research abstract

Li metal anodes are considered as the most promising candidates for rechargeable Li-based batteries, but uncontrollable Li dendrites hinder their further applications. In recent years, MXenes have promoted the rapid development of dendrite-free lithium metal anodes. Since Professor Yang Shubins team published an article on MXenes for metal lithium anodes, MXenes with horizontal and vertical structures have also been further applied to metal lithium anodes, and have achieved better performance. Through extensive research on MXenes on lithium metal anodes, it is found that vertically aligned MXene metal lithium composite anodes have higher capacity and energy density. However, in vertically aligned MXenes, due to the extremely small radius of curvature, the tip discharge effect is significantly amplified, resulting in the easy deposition of metallic lithium on the electrode surface and the formation of dendrites. Therefore, in order to solve this problem, in this research work, MXene films with low curvature flexible sine-like structure were prepared and applied to metal lithium anodes.

Introduction

Recently, the team of Professor Shubin Yang from Beihang University has innovatively prepared a low-curvature flexible sine wave-like structure MXene film and applied it to the metal lithium anode. First, the theoretical simulation study in COMSOL Multiphysics shows that the curvature of the electrode surface has an important impact on the nucleation and growth behavior of metallic lithium. In this study, by establishing a groove model, the influence of the groove model on the electrodeposition behavior of metallic lithium was systematically studied. In order to obtain high capacity The dendrite-free lithium metal anode provides a new idea. Under the guidance of the theoretical model, a sine-like structure MXene film with low curvature was designed and controllably prepared, and the nucleation of metallic lithium on the sine-like structure MXene film was systematically studied by in-situ optical electron microscopy and SEM analysis. growth pattern.

The result was published online in the top international journal Advanced Energy Materials (impact factor 29.698) with the title: Eliminating Lightning-Rod Effect of Lithium Anodes via Sine-Wave Analogous MXene Layers.

Graphical guide

Figure 1. Schematic diagram of the deposition process of lithium metal on (a) sine-like structure (low curvature) and (b) vertical array structure (high curvature), respectively.

Figure 2. The sine-like structure of MXene films (a) schematic diagram of the preparation process, (b) front SEM image, (c) cross-sectional SEM image. (d) Impedance response test of sine-like MXene and planar MXene films.

Figure 3. SEM images of MXene films with sine-like structure after deposition of (a) 0.5 mAh cm-2, (b) 4 mAh cm-2 and (c) 8 mAh cm-2, respectively. (d) Schematic diagram of different deposition processes of metallic lithium on MXene films with sine-like structure simulated by COMSOL Multiphysics. In situ optical photographs of the deposition process of metallic lithium on (e) sine-like MXene films and (f) metallic copper surfaces.

Figure 4. (a) contact angle test and (b) nucleation overpotential test of sine-like structure MXene film, planar structure MXene film and metallic copper. (c) Cycling performance of sine-like MXene-Li, planar MXene-Li and metallic Cu-Li. (d) Rate performance of sine-like structure MXene-Li.

Figure 5. (a) and (b) photos of MXene-Li pouch cells with sine-like structure. Cycling performance of (c) sine-like MXene-Li pouch battery and (d) planar MXene-Li pouch battery under different bending states. (e) Deep charge and deep discharge performance of MXene-Li with a sine-like structure.

Figure 6. Sine-like structure MXene-Li//LFP, planar structure MXene-Li//FLP and Cu-Li//FLP (a) cycling performance at 34 mA g-1, (b) rate performance and ( c) Cycling performance at 1088 mA g-1.

Summarize

In this study, a sine-like structure MXene (Ti3C2Tx) thin film was obtained by dispersing an aqueous MXene solution onto the cross-sectional surface of a metal coil and then drying it at room temperature. COMSOL Multiphysics simulation results show that the low curvature of the sine-like structure MXene film can effectively homogenize the distribution of lithium ions and electric field, and effectively eliminate the tip discharge effect on the electrode surface during the lithium deposition process. Therefore, the MXene film with a sine-like structure has a low lithium nucleation overpotential (~13.5 mV at 0.05 mA cm−2), a deep charge and deep discharge capacity of up to 40 mAh cm−2, and a long cycle life of 1250 h. . In addition, the full cell based on the sine-like structure of MXene-Li composite anode and LiFePO4 cathode achieves a cycle life of up to 420 cycles at a current density of 1088 mA g−1.

Literature link

https://doi.org/10.1002/aenm.202201181

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