The investigation for electrodeposition behavior of lithium metal in a crown ether/propylene carbonate electrolyte

Abstract

It is so far an efficient way for depressing dendrite growth to adjust the electrolyte composition. Therefore, we study the electrochemical behavior of lithium metal electrodeposited in a LiPF6-propylene carbonate (PC) electrolyte by adding two kinds of crown ether. The effect of crown ether concentration on the Coulombic efficiency of lithium electrodes has be evaluated, and the electrodeposition behavior of lithium metal on negative electrode has be analyzed by cyclic voltammetric curve, electrodeposition curve and lithium metal deposition morphology. The results show that a certain amount of crown ether (15-crown-5 and 12-crown-4) can preferentially coordinate with lithium ion in the electrolyte and form complex compounds, which reduce the lithium ions concentration in the “hot spot” and level the lithium electrode greatly by inhibiting the preferential growth of lithium dendrite. A uniform and dense nano-columnar lithium layer could be obtained at the current density of 2.0 mA cm−2 when the deposition amount is 1.0 mAh cm−2, and the concentration of 15-crown-5 and 12-crown-4 ether are 0.3 M and 0.2 M, respectively. Gaussian calculation results show that the lithium-crown complex has a relatively lower lowest unoccupied molecular orbit (LUMO), where electrons could be injected during the charging process, leading to decreased Coulumbic efficiency.