Yuki Yamada 교수

The development of a stable, functional electrolyte is urgently required for fast-charging and high-voltage lithium-ion batteries as well as next-generation advanced batteries (e.g., Li-O2 systems). Acetonitrile (AN) solutions are one of the most promising electrolytes with remarkably high chemical and oxidative stability as well as high ionic conductivity, but its low stability against reduction is a critical problem that hinders its extensive applications. Herein, we report enhanced reductive

Ever-increasing demand for better batteries has set extraordinarily high standards for electrolyte materials, which are far beyond the realm of a conventional nonaqueous electrolyte design. Superconcentrated (or highly concentrated) solutions are emerging as a new class of liquid electrolytes with various unusual functionalities beneficial for advanced lithium (Li) battery applications. This article reviews unique features, as well as basic physicochemical properties, of highly concentrated elec

We have found ultrafast Li(+) intercalation into graphite in a superconcentrated ether electrolyte, even exceeding that in a currently used commercial electrolyte. This discovery is an important breakthrough toward fast-charging Li-ion batteries far beyond present technologies.

The kinetics of lithium ion transfer at an interface between graphite and liquid electrolyte was studied by ac impedance spectroscopy. Using highly oriented pyrolytic graphite (HOPG) as a model electrode, we evaluated the activation energies of the interfacial lithium ion transfer from the temperature dependences of the interfacial conductivities. When a binary electrolyte consisting of LiClO(4) dissolved in a mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) (1:1 by volume) was us

Abstract Metal corrosion is a serious problem that has beset various electrochemical systems. For lithium‐ion batteries, oxidative corrosion of an Al current collector has been a great challenge in designing new electrolyte materials, and only a few lithium salts (e.g. LiPF 6 ) are in practical use. The present work shows effective suppression of Al corrosion up to 4.5 V versus Li + /Li by using a highly concentrated electrolyte of lithium bis(fluorosulfonyl)amide (LiFSA). The corrosion preventi

Lithium-ion batteries have exclusively employed an ethylene carbonate (EC)-based electrolyte to ensure the reversibility of the graphite negative electrode reaction. Because of the limitation of electrolyte compositions, there has been no remarkable progress in commercial lithium-ion batteries despite active research on positive electrode materials. Herein, we present a salt-superconcentrating strategy as a simple and effective method of universalizing a graphite negative electrode reaction in v

The behavior of electrochemical lithium intercalation at graphite has been investigated in dimethyl sulfoxide (DMSO)-based electrolytes: (1) lithium salt-concentrated solutions and (2) binary solutions with dimethyl carbonate (DMC). The intercalation of DMSO-solvated lithium ion (i.e., cointercalation of DMSO) into graphite occurred during charge in 1.0 mol dm−3 LiN(SO2CF3)2/DMSO, whereas the use of a salt-concentrated solution (e.g., 3.2 mol dm−3 LiN(SO2CF3)2/DMSO) or a binary solution (e.g., 1

The kinetics of the electrochemical insertion and extraction of lithium ion at silicon monoxide (SiO) were investigated by ac impedance spectroscopy. The resultant Nyquist plots showed two semicircles at high and middle frequency regions. These two semicircles were attributed to lithium-ion transport resistance in a surface film and alloying reaction resistance (charge-transfer resistance), respectively. We evaluated the activation energies of the charge-transfer reaction from the temperature de

A non-aqueous electrolyte solution for lithium-ion batteries has been optimized at around 1 mol dm−3 salt concentration based upon ionic conductivity. Recently, however, superconcentrated solutions (e.g., over 3 mol dm−3) are emerging as a new class of liquid electrolyte that develops unique interfacial chemistry on battery electrodes. In this article, we discuss the origin of the unique interfacial chemistry from the viewpoint of their peculiar liquid structure, and highlight advanced rechargea

The kinetics of lithium-ion transfer at a Li0.35La0.55TiO3 (LLT)/liquid electrolyte interface were investigated by four-probe ac impedance spectroscopy. In Nyquist plots for a system consisting of Li/electrolyte/LLT/electrolyte/Li, two semicircles were observed at high- and midfrequency regions and were attributed to grain-boundary resistance in LLT and interfacial resistance between LLT and the liquid electrolyte. The activation energies of interfacial lithium-ion transfer were evaluated from t

The charge−discharge behaviors of natural graphite in propylene carbonate (PC):dimethyl carbonate (DMC) mixed solutions were investigated after a solid electrolyte interface (SEI) was formed in an ethylene carbonate (EC)-based electrolyte. Electrolytes consisting of LiClO4/PC and PC:DMC (1:1 by vol) caused a continuous decomposition of solvents, which led to the exfoliation of graphite. On the other hand, LiClO4/PC:DMC (1:7 by vol) showed successful charge−discharge curves without the exfoliatio