Chemical Reaction of Lithium Surface during Immersion in LiClO4 or LiPF6 /  DEC  Electrolyte

Abstract

Chemical reactions of lithium with diethyl carbonate (DEC) containing 1.0 mol dm3 LiC1O4 or LiPF6 (LiClO4/DEC or LiPF6/DEC) were studied by using in situ Fourier transform infrared (FTIR) and x-ray photoelectron spectroscopies. The in situ FTIR spectra for both electrolytes show a penetration of the DEC electrolyte into the native surface film on lithium foils at the initial period of immersion. In the case of LiC1O4/DEC, the DEC solvent contacts the lithium metal, and then reacts directly with lithium metal to form reductive decomposition products of DEC, such as lithium alkylcarbonate, lithium alkoxide, and Li2CO3. When LiPF6/DEC was used as the electrolyte, the native surface film was gradually etched and then changed to a LiF/Li20 bilayer surface film. The in situ FTIR spectra showed no formation of decomposition products of DEC. This means that the surface film consisting of LiF/Li20 was highly effective in suppressing the direct chemical reactions of DEC with lithium metal.

An Artificial Lithium Protective Layer that Enables the Use of Acetonitrile‐Based Electrolytes in Lithium Metal Batteries

“…100-250 nm diameter, as estimated from the AFM images (Figure 3c). Moreover,a ccording to Kanamura et al,t he spontaneous reaction between Li metal and 1m LiPF 6 in DEC produces asurface layer mainly composed of inorganic Li salts,i ncluding PF 5 and LiF, [20] and the degradation of EC forms astable SEI mostly composed of Li ethylene dicarbonate (CH 2 OCO 2 Li) 2 . [21] Thec ombination of both the solvent and the salt creates asurface layer similar to the widely accepted SEI mosaic structure model which consists of multiple inorganic and organic products originating from the electrolyte decomposition.…”

Review on Li‐Sulfur Battery Systems: an Integral Perspective

“…In the studies described here, the capacity was limited to 600 mAh g −1 . [56][57][58] Monolithic Si electrodes with a thickness of ≈7 µm were prepared for assembling lithiated silicon-sulfur (SLS). The galvanostatic charge/discharge voltage profi les for various cycles of these a-Si fi lm electrodes vs. Li + /Li (cycled according to the charge limited procedure with a charge cutoff capacity of 600 mA h g −1 ) are shown in Figure 13 d. Very stable cycling of Si/Li cells was obtained during several thousands of cycles.…”

An Artificial Lithium Protective Layer that Enables the Use of Acetonitrile‐Based Electrolytes in Lithium Metal Batteries

“…We noticed an electrochemical behavior similar to the cell with FEC used as additive in the electrolyte.I nb oth cases,t he initial overpotential remained lower than 100 mV for as hort time after rapidly increasing to the 10 Vcut-off,showing that only dense passivation layers formed by pure FEC decomposition can efficiently prevent ACNd ecomposition. Moreover,a ccording to Kanamura et al,t he spontaneous reaction between Li metal and 1m LiPF 6 in DEC produces asurface layer mainly composed of inorganic Li salts,i ncluding PF 5 and LiF, [20] and the degradation of EC forms astable SEI mostly composed of Li ethylene dicarbonate (CH 2 OCO 2 Li) 2 . TheLimetal was immersed in 1m LiPF 6 in EC/DEC 1:2( v/v) or neat FEC for 5h.T he untreated Li metal surface (Figure 3a)presents arelatively smooth surface with few cavities.InF igure 3b,c the surface was imaged after 5h of immersion in 1m LiPF 6 in EC/DEC 1:2( v/v).…”