Rechargeable batteries are increasingly in demand for larger devices such as electric vehicles that require high performance. The reaction at the interface between electrode and electrolyte strongly influences a battery’s performance.
To better understand this reaction, a team of Japanese scientists used frequency-modulation atomic force microscopy (FM-AFM) in liquid to observe the structure of the interface with high resolution. In particular, they looked at the interface structure between tetraglyme and graphite — the electrode material and organic solvent, respectively, in lithium-ion batteries. The results were published in The Journal of Chemical Physics.
Previous studies have investigated the interface between organic liquids and solids using X-ray and neutron techniques. With the recent development of FM-AFM, highly resolved images of the interface can be directly produced in three dimensions. The researchers used highly oriented pyrolytic graphite (HOPG) as the model for the graphite electrode and deposited tetraglyme on its surface. Along with collecting FM-AFM images via lateral and vertical scanning, they investigated the adsorption structure of tetraglyme on HOPG with density functional theory (DFT) calculations.
According to first author Taketoshi Minato, the most important achievement is the observation of the tetraglyme/HOPG interface structure with molecular resolution for the first time, because this opens the new possibility to directly visualize the interface in rechargeable batteries. The adsorbed tetraglyme forms a linear and ordered structure on the HOPG, which suggests adsorption is stable. In addition, the tetraglyme in the liquid phase around the interface forms a layered structure.
Ultimately, understanding the interface between the electrode and electrolyte could lead to enhancements for better performance in rechargeable batteries. In the future, Minato and his colleagues hope to observe the interface structure between electrode and electrolyte in a working rechargeable battery.
Source: “Interface structure between tetraglyme and graphite,” by Taketoshi Minato, Yuki Araki, Kenichi Umeda, Toshiro Yamanaka, Ken-ichi Okazaki, Hiroshi Onishi, Takeshi Abe, and Zempachi Ogumi, The Journal of Chemical Physics (2017). The article can be accessed at https://doi.org/10.1063/1.4996226.
