Anion-Dependent Potential Precycling Effects on Lithium Deposition/Dissolution Reaction Studied by an Electrochemical Quartz Crystal Microbalance

Abstract

The electrochemical quartz crystal microbalance technique was employed to study the initial stage of the electrodeposition and dissolution of lithium utilizing three kinds of electrolyte solutions such as LiPF, LiTFSI, or LiFSI in tetraglyme. The native-SEI (solid-electrolyte interphase) formed by a potential prescan before lithium deposition/dissolution in all three solutions. Simultaneous additional SEI (add-SEI) deposition and its dissolution with lithium deposition and dissolution, respectively, were observed in LiPF and LiTFSI. Conversely, the add-SEI dissolution with lithium deposition and its deposition with lithium dissolution were observed in LiFSI. Additional potential precycling resulted in the accumulation of a "pre-SEI" layer over the native-SEI layer in all of the solutions. With the pre-SEI, only lithium deposition/dissolution were significantly observed in LiTFSI and LiFSI. On the basis of the potential dependences of the mass and resistance changes, the anion-dependent effects of such a pre-SEI layer presence/absence on the lithium deposition/dissolution processes were discussed.

The Study of the Binder Poly(acrylic acid) and Its Role in Concomitant Solid–Electrolyte Interphase Formation on Si Anodes

“…This is not the full 7 m / z expected for the state of lithiation, thus indicating consumption of Li + most likely in the formation of the SEI layer. Smaran et al found that m / z < 7 was attributed to SEI formation on the surface of Li metal in glyme-based electrolytes . The relatively slow kinetics of the Li deposition at 0.05 V would suggest that a small amount of Li deposits would react with the solvent and subsequent impurities, such as HF, resulting in a low m / z ratio …”

“…Smaran et al found that m/z < 7 was attributed to SEI formation on the surface of Li metal in glyme-based electrolytes. 49 The relatively slow kinetics of the Li deposition at 0.05 V would suggest that a small amount of Li deposits would react with the solvent and subsequent impurities, such as HF, resulting in a low m/z ratio. 50 Upon delithiation to 1.5 V, the SEI layer grows to 15 ± 0.2 nm with an increase in the SLD to 3.83 ± 0.05 (from 1.52), reflecting a change in the chemistry of the layer as a result of the delithiation of the anode (Table 1).…”

Li Plating/Stripping Efficiency in Ether‐based Dilute Electrolyte for Anode‐free Lithium‐metal Batteries: Effect of Operating Potential Range on Subsequent SEI Layer Structure

“…Multiple MPE values were obtained during Li plating, indicating multiple electrochemical processes. [36] An extra film was formed during Li plating due to the reaction of plated Li metal with electrolyte as indicated by MPE values much larger than 7 (a value indicating only Li plating/stripping occurs). [43] The possible surface species are the complicated organics from the decomposed TEGDME molecule and the organic Li salts from the reaction of Li metal with these organics, resulting in the overall MPE values around 50-80.…”

“…The MPE (mass change per mol e − ) values during this process, which can be calculated from the slope of the plot with Δ m as a function of the passed charge, was close to 10. It was deemed to be a result of several electrochemical reactions that generated both dissolved products and deposited products, while the latter were mostly inorganic species, especially Li 2 O which could be a product of the reductive decomposition of LiTFSI (Li 2 O as one of the final products, MPE unknown), [36,37] or the reduction of Cu oxides on the Cu surface (Cu x O+2Li→Li 2 O+ x Cu), [16] or even the reaction with trace oxygen in glove box (O 2 +4Li + +4e − →2Li 2 O, MPE=15) [38] . This could also suggest that TEGDME did not heavily decompose prior to the initial Li plating (also indicated by the weak reduction current shown in Figure S1a), since most of the decomposed fragments and derivatives of TEGDME have larger MPE values [39,40] .…”

Origin of Solvent Stabilization at Superconcentrated Electrolyte/Electrode Interfaces Revealed by Heterodyne-Detected Vibrational Sum Frequency Generation Spectroscopy

“…The CVs exhibit negative and positive current peaks around −3.0 V in both cases. The negative and positive peaks have been assigned to lithium deposition and the dissolution of the deposited metal lithium, respectively, 36 indicating lithium deposition/dissolution takes place in both dilute and superconcentrated electrolyte solutions. While the dilute system shows almost no current peak in the potential region more positive than −2.0 V, the saturated system shows negative and small positive peaks around −1.7 and −0.7 V, respectively.…”