EDL Effect in Solid Electrolytes -Lithium - Ion Battery Equipment

Difficulties in Studying the EDL Effect in Solid Electrolytes -Lithium - Ion Battery Equipment

The progress of Li ion batteries has made various portable devices feasible and promoted the development of electronic products. However, the inherent shortcomings of traditional lithium ion batteries, which use liquid electrolyte solutions, make them not completely suitable for electric vehicles and other highly anticipated applications. These limitations include limited durability, low capacity, safety issues, and environmental concerns about their toxicity and carbon footprint. Fortunately, scientists are now focusing on the next generation solution to all these problems: all solid state batteries. The use of solid electrolyte makes this type of battery safer and able to maintain greater power density.(Lithium - Ion Battery Equipment)

However, a key problem with these batteries is the high resistance at the electrolyte electrode interface, which will reduce the output of all solid state batteries and prevent them from charging quickly. A discussion mechanism behind this high interface resistance is the double electric layer (EDL) effect, which involves collecting charged ions from the electrolyte at the interface with the electrode. This will produce a layer of positive or negative charges, which will result in the charge of the opposite symbol accumulating on the entire electrode with equal density, thus forming a double layer charge. The problem of detecting and measuring EDL in all solid state batteries is that traditional electrochemical analysis methods cannot solve the problem.

At Tokyo University of Science in Japan, scientists led by associate professor Tohru Higuchi solved this problem by using a new method to evaluate the EDL effect in solid electrolyte of all solid state batteries. This research was published online on Nature's Communications Chemistry and was conducted in cooperation with Takashi Tsuchiya, chief researcher of the International Center for Nanostructures of Materials (MANA) of the National Institute of Materials Science of Japan, and Kazuya Terabe, chief researcher of MANA of the same organization

The new method focuses on the field effect transistor (FET) made of hydrogenated diamond and solid lithium based electrolyte. FET is a three terminal transistor in which the current between the source and drain can be controlled by applying voltage to the gate. Because of the electric field generated in the semiconductor region of the FET, this voltage controls the density of electrons or holes (positively charged "electron vacancies"). By taking advantage of these characteristics and using chemically inert diamond channels, scientists ruled out chemical reduction and oxidation effects that affect channel conductivity, leaving only static charges accumulated due to EDL effects as a necessary reason.

Therefore, scientists carried out Hall effect measurement on the diamond electrode, which is only sensitive to the charged carriers on the material surface. They used different types of lithium based electrolytes and studied how their composition affected EDL. Through their analysis, they revealed an important aspect of EDL effect: it is determined by the composition of electrolyte near the interface (about 5 nm thick). If the electrolyte material allows charge compensated reduction oxidation reaction, the EDL effect can be suppressed by several orders of magnitude.

The team now plans to use their method to analyze the EDL effect in other electrolyte materials, hoping to find clues about how to reduce the interface resistance of the next generation battery. We hope that our approach will lead to the development of all solid state batteries with very high performance in the future, Dr. Higuchi concluded. In addition, a better understanding of EDL will also contribute to the development of capacitors, sensors, memories and communication devices. Let's hope that other scientists can explore this complex phenomenon more easily, so that the field of solid-state ion devices can continue to progress.



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