The AM article of Prof. Zheng Zijian's team from the Hong Kong Polytechnic University: In-situ ultraviolet curing method based on light-transmitting 3D composite lithium metal anode solves the interface problem of positive and negative electrodes of solid-state lithium metal batteries
【Article Information】
Seamless interface flexible polymer solid-state lithium metal batteries were prepared by in-situ ultraviolet curing method based on light-transmitting 3D composite lithium metal anode
First Author: Xie Chuan
Corresponding author: Prof. Zheng Zijian
Affiliation: The Hong Kong Polytechnic University
【Background】
Flexible lithium batteries are indispensable for the flexible wearable electronics of the future. In addition to having good mechanical deformability, i.e., flexibility, high safety, high energy density and long-cycle stability are the design priorities of flexible lithium batteries. Compared to traditional lithium batteries, solid-state lithium metal batteries have high thermal stability, while their weight and volumetric energy density can be improved by ~40% and ~70%. In the solid-state lithium metal battery system, the polymer-based solid-state lithium metal battery is expected to achieve the above performance of the flexible lithium battery at the same time due to the good intrinsic flexibility of the polymer. However, the mechanical and electrochemical properties of polymer solid-state lithium metal batteries prepared based on lithium metal foil cannot meet the requirements of use, so the design and interface optimization of lithium metal anode are very important.
【Introduction】
近日，来自香港李理工大学的郑子剑教授团队，在国际知名期刊Advanced Materials上发表题为“UV-Permeable 3D Li Anodes for in situ Fabrication of Interface-Gapless Flexible Solid-State Lithium Metal Batteries”的研究论文。 该文章设计了一种可透光3D复合锂金属负极并应用于原位紫外光固化法制备聚合物固态锂金属电池，用以解决固态电解质与电极间的界面接触和锂金属负极循环稳定性问题。
Figure 1. Solid-state lithium metal batteries were prepared by in-situ ultraviolet curing method based on light-transmitting 3D composite lithium metal anode. a. Mechanism of in-situ ultraviolet curing for the preparation of solid-state lithium metal batteries. b. Solid-state lithium metal batteries prepared based on in-situ methods have good interfacial contact and ion transport. c. Solid-state lithium metal batteries prepared based on non-in-situ methods have poor interfacial contact and ion transport performance.
【Main points of the text】
Point 1: One-step preparation of polymer solid-state lithium metal batteries by in-situ ultraviolet curing
There are still many problems with conventional in-situ polymerization methods based on heat-initiated polymerization. Thermal initiation typically requires high-temperature heating, which accelerates the occurrence of side reactions between the polymer precursor and the lithium metal anode, which can deplete the active lithium and reduce the cycle life of the system using a finite capacity lithium metal anode. Heat-initiated polymerization usually takes a long time and is not very productive. The use of ultraviolet photopolymerization can effectively avoid the shortcomings of thermal polymerization, but it can only be applied to the surface coating and polymerization of single-sided electrodes, and it is difficult to be applied to the traditional lithium metal foil system to realize the preparation of whole cells. In this work, a porous and translucent 3D composite lithium metal anode was designed, which can realize the rapid one-step preparation of whole cells by ultraviolet curing method and realize seamless interface contact between the positive and negative electrodes.
Point 2: The 3D structure solves the cycling stability of the lithium metal anode
When using conventional lithium metal foil to prepare solid-state lithium metal batteries, only small current, low capacity cycling can be achieved. This is due to the fact that the interface obtained when using lithium metal foil is a 2D planar contact, which has a small contact area and limited ion transport. In addition, the resulting battery cycle life is limited, because the accumulation of SEI and dead lithium at the interface leads to further deterioration of contact, making it difficult to achieve excellent performance. The introduction of 3D structure in this research work can increase the effective contact area between lithium metal and solid electrolyte, which can improve the critical current density and circulating capacity. In addition, due to the existence of 3D structure, the generation of dead lithium can be effectively reduced, the interface can be stabilized, and the cycling performance of the anode can be greatly improved.
Point 3: Optimized full battery performance, safety and flexibility
The solid-state lithium metal battery prepared by ultraviolet in-situ curing method based on light-transmitting 3D composite lithium metal anode has good mechanical flexibility, electrochemical stability and safety. In the all-battery demonstration, the LFP full-battery capacity remained at 84% after 500 cycles. In addition, this composite lithium metal anode can also be matched with high-load cathode and high-voltage cathode, and the maximum surface capacity of the whole battery can reach 3 mAh cm-2. LCO, NCM622 and NCA815 cathodes can be used together. Pouch cells can be bent repeatedly thousands of times without charging and discharging voltage fluctuations. In addition, it has good safety, the solid-state electrolyte is non-flammable, and the pouch battery is cut without fire and explosion.
【Article Link】
UV-Permeable 3D Li Anodes for in situ Fabrication of Interface-Gapless Flexible Solid-State Lithium Metal Batteries
https://onlinelibrary.wiley.com/doi/abs/10.1002/adma.202406368
【About the Corresponding Author】
Prof. Zheng Zijian: Chair Professor of Soft Matter and Devices, Department of Applied Biology and Chemical Technology, Associate Dean of the Institute of Intelligent Wearable Systems, Deputy Director of the Central Laboratory of Materials and Devices, Changjiang Chair Professor of the Ministry of Education, Senior Research Fellow of the RGC of Hong Kong, Fellow of the Royal Society of Chemistry, Fellow of the Hong Kong Young Academy of Sciences (first batch), Member of the Youth Division of the Hong Kong Academy of Engineering Sciences (first batch) and Chairman. He received his B.S. in Polymer from the Department of Chemical Engineering of Tsinghua University in 2003, his Ph.D. in Chemistry from the University of Cambridge in 2007, and his postdoctoral fellow from the Center for Nano at Northwestern University in 2009. He is engaged in the design, preparation and mechanism research of new materials and devices in the fields of flexible electronics, flexible energy conversion and storage. He has published more than 200 papers in internationally renowned journals such as Science, Science Advances, Nature Materials, Nature Communication, Advanced Materials, etc., founded EcoMat, a new journal focusing on green energy and environmental materials under Wiley Press, and served as the editor-in-chief of Advanced Energy Materials. He is an international editorial board member of Advanced Functional Materials, npj Flexible Electronics, and many other magazines.