High-Voltage Electrolytes Based on Adiponitrile for Li-Ion Batteries

Abstract

Adiponitrile, CN[CH2]4CNCN[CH2]4CN , ADN, was evaluated as both a solvent and cosolvent in safer and more electrochemically stable electrolytes suitable for high energy and power density Li-ion batteries. An electrochemical investigation of its electrolyte solution with the Li(CF3SO2)2NLi(CF3SO2)2N , LiTFSI, salt showed a wide electrochemical window of 6V6V vs Li+∕LiLi+∕Li . The high melting point and the incompatibility of ADN with graphite anode required the use of ethylene carbonate (EC) as a cosolvent. The resultant EC:ADN electrolyte solutions showed ionic conductivities reaching 3.4mS∕cm3.4mS∕cm , viscosities of 9.2cP9.2cP , and an improved resistance to aluminum corrosion up to 4.4V4.4V , all at 20°C20°C . Li-ion batteries incorporating graphite/ LiCoO2LiCoO2 electrodes were assembled using EC:ADN electrolyte mixture containing 1M1M LiTFSI and 0.1M0.1M LiBOB as a cosalt, and discharge capacities of 108mAh∕g108mAh∕g with very good capacity retention were obtained. AC impedance spectra of the batteries recorded as a function of charging and cycling indicated the presence of a stable solid electrolyte interface.