YANG CHENGKAI SMALL'S VIEW: BUFLULAMIDE IS USED AS AN ELECTROLYTE ADDITIVE TO REGULATE THE INTERFACE BEHAVIOR OF LITHIUM METAL ANODE
【Article Information】
Buflunomide is used as an electrolyte additive to regulate the interface behavior of lithium metal anode
First author: Zheng Xinyu
Contact: YANG Cheng-kai*, ZHANG Ran*, LIU Zhe-yuan*, YU Yan*
Affiliation: Fuzhou University, Wuhan University
【Background】
As the most commercially successful energy storage device, lithium-ion batteries have made significant contributions to human life and social progress. However, with the advancement of science and technology, its relatively low energy density has become a key factor limiting its further development. There is a growing demand for higher energy density, and there is an urgent need to develop the next generation of rechargeable batteries with high energy density and high safety. The lithium metal anode has become the focus of research due to its extremely high theoretical capacity (3860 mAh g-1). However, as a new anode material, there are still many challenges for lithium metal anode, many of which are related to the lithium metal anode itself. Since lithium metal is a reactive metal, it is prone to side reactions with most organic electrolytes to form a solid electrolyte membrane (SEI) at the anode/electrolyte interface. The stability of SEI is critical to battery performance. By designing the three-dimensional frame and optimizing the interface, the performance of the lithium metal anode can be effectively improved. At the same time, the regulation of the electrolyte also has a significant impact on the performance of the anode.
【Introduction】
近日，来自福州大学杨程凯副教授与合作者，在国际知名期刊Small上发表题为“Perfluorinated Amines: Accelerating Lithium Electrodeposition by Tailoring Interfacial Structure and Modulated Solvation for High-Performance Batteries”的观点文章。 文章通过添加剂策略调控电解液，选用了全氟化的动力学加速剂——全氟化卜氟胺（PFM）。 核磁共振谱和模拟计算结果表明，PFM分子不直接参与溶剂化结构，而是扰动内层溶剂化结构，为锂离子提供更宽松的传输环境。 这种扰动增加了电解液中锂离子的扩散系数。
Electrochemical tests and simulations show that PFM molecules are preferentially adsorbed on the surface of lithium metal anode, which promotes the interfacial desolubilization process and accelerates the deposition of lithium ions. In addition, PFM molecules can also modulate the composition of SEI to form LiF-rich SEI, which can achieve a more uniform lithium-ion deposition morphology. Eventually, in Li||Li symmetrical battery and Li||The NCM811 showed a significant performance improvement in the performance test of the whole battery.
Figure 1. a) Molecular structure description of BZTF and PFM. b) 7Li and c) 19F nuclear magnetic resonance (NMR) spectroscopy. d) Two-dimensional NMR diffusion sequencing spectroscopy (DOSY) describes the mobility of Li+ in different electrolyte media. e) Comparative Raman spectroscopy of the electrolyte solution and its corresponding pure solvent.
【Main points of the text】
Adjusting the solvation structure is an effective means to improve the interface performance of the positive and negative electrodes of the battery. Numerous studies have shown that the structure of AGG (anion-dominated solvation cluster) in high-concentration electrolyte can significantly enhance the stability of the electrode interface. In this structure, anions are deeply involved in the solvation process and decompose at the electrode interface to form a stable interfacial layer rich in inorganic components. However, increasing the lithium salt concentration increases the cost and electrolyte viscosity. To solve this problem, the researchers introduced the concept of diluents, which reduce the concentration and viscosity of lithium salts by adding an inert solvent while keeping the AGG solvated structure undamaged.
In this study, we manipulated the solvation structure of the electrolyte by carefully selecting the solvent. FEC and ETFA were selected as the main solvents, which have weak solvation ability and excellent oxidation resistance, which help to weaken the coordination strength of Li+ and solvent and improve the performance of the electrolyte under high pressure. At the same time, an appropriate amount of ether solvent DME was added, which had good compatibility and low-temperature performance with lithium metal anode, although its antioxidant capacity needed to be improved. With this combination, the electrolyte maintains the integrity of the AGG solvation structure while reducing cost and viscosity.
Figure 2: Simulation of the solvation structure of the electrolyte. Snapshots of a) blanks, b) BZTF, and c) BZTF+PFM electrolytes captured from AIMD traces. d) Blank, radial distribution function (RDF) and coordination number (N(r)) of BZTF and f) BZTF+PFM electrolytes. Mean square displacement analysis of g) blank, h) BZTF and i) BZTF+PFM electrolytes by AIMD.
The lithium salt concentration was further increased to 2 mol/L, and the electrolyte was then diluted to 1 mol/L using HFE diluent. Through Raman spectroscopy, nuclear magnetic resonance spectroscopy and simulation calculations, we found that the AGG solvation cluster structure was successfully formed in the 1M-HFE electrolyte, which significantly increased the coordination number of Li+ and anion. This design enables the electrolyte to obtain the AGG solvation structure at a lower concentration, and the scanning electron microscopy and X-ray photoelectron spectroscopy analysis confirm that a stable interface layer rich in inorganic products can be formed in the 1M-HFE electrolyte, regardless of the positive and negative electrode interfaces.
Figure 5. Battery performance. a) Li||, among the three electrolytesLi symmetrical battery with a current density of 2.0 mA cm-2 and a capacity of 1.0 mAh cm-2. b） Li||The discharge capability of the NCM811 full cell and the corresponding cyclic Columbus efficiency (CE).
During the charging and discharging process, this improvement in stability is directly reflected in the uniform deposition on the surface of the lithium metal anode, as well as the structural stability of the NCM811 cathode. The 1M-HFE electrolyte shows good application potential under extreme temperature and high pressure conditions. After 100 cycles at a magnification of 0.5 C, Li||The capacity retention rate of NCM811 is as high as 85.2%, which opens up new ideas for the application of batteries in special applications.
This research not only improves battery performance, but also enables high-performance battery design at low cost and low viscosity. It provides an important theoretical basis and practical guidance for the further optimization and application of lithium-ion batteries, especially the application prospects under extreme temperature and high voltage conditions. On this basis, future research can further explore the effects of different solvent and lithium salt combinations on battery performance, and how to achieve the overall improvement of battery performance through the regulation of solvation structure.
【Article Link】
Perfluorinated Amines: Accelerating Lithium Electrodeposition by Tailoring Interfacial Structure and Modulated Solvation for High-Performance Batteries
https://onlinelibrary.wiley.com/doi/abs/10.1002/smll.202404614
【About the Corresponding Author】
杨程凯：福州大学，材料科学与工程学院，副教授，硕导，北京大学化学与分子工程学院，博士。 福建省硅酸盐学会理事。 福建省高层次人才。 研究内容包括锂离子电池，锌离子电池，第一性原理分子动力学，工作面向高效能源存储材料与化学，提出了锂离子电池三元正极材料内部结构，并研究内部界面破碎规律，提出链反应机理，拓展了电解质构造方法，并给出特定溶剂化环境下的动力学。 以第一或者通讯作者在Adv. Mater., Adv. Energy Mater, Energy Stor. Mater., Electrochemical Energy Reviews, Adv. Funct. Mater., ACS Energy Lett, JMCA, Small, J. Power Sources, J Energy Chem., ACS Appl. Mater. Interfaces, Chem. Eng. J.等国际期刊上发表SCI论文50余篇。
The related work has been approved by the National Natural Science Foundation of China, the Natural Science Foundation of Fujian Province, the key project of the Shanxi Provincial Department of Science and Technology and the horizontal project of the enterprise. Interested students are welcome to write to [email protected].
【First Author Introduction】
Zheng Xinyu, Fuzhou University, M.S. Joined CATL.