Kinetics Tuning the Electrochemistry of Lithium Dendrites Formation in Lithium Batteries through Electrolytes

Lithium batteries are one of the most advance energy storage devices in the world and have attracted extensive research interests. However, lithium dendrite growth was a safety issue which handicapped the application of pure lithium metal in the negative electrode. In this investigation, two solvents, propylene carbonate (PC) and 2-methyl-tetrahydrofuran (2MeTHF), and four Li+ salts, LiPF6, LiAsF6, LiBF4 and LiClO4 were investigated in terms of their effects on the kinetics of lithium dendrite formation in eight electrolyte solutions. The kinetic parameters of charge transfer step (exchange current density, j(0), transfer coefficient, a) of Li+/Li redox system, the mass transfer parameters of Li+ (transfer number of Li+, t(Li+), diffusion coefficient of Li+, DLI+), and the conductivity (kappa) of each electrolyte were studied separately. The results demonstrate that the solvents play a critical role in the measured j(0), t(Li+), DLi+, and kappa of the electrolyte, while the choice of Li+ salts only slightly affect the measured parameters. The understanding of the kinetics will gain insight into the mechanism of lithium dendrite formation and provide guidelines to the future application of lithium metal.