Decomposition Reactions of Anode Solid Electrolyte Interphase (SEI) Components with LiPF₆

Abstract

The anode solid electrolyte interface (SEI) on the anode of lithium ion batteries contains lithium carbonate (Li2CO3), lithium methyl carbonate (LMC), and lithium ethylene dicarbonate (LEDC). The development of a strong physical understanding of the properties of the SEI requires a strong understanding of the evolution of the SEI composition over extended timeframes. The thermal stability of Li2CO3, LMC, and LEDC in the presence of LiPF6 in dimethyl carbonate (DMC), a common salt and solvent, respectively, in lithium ion battery electrolytes, has been investigated to afford a better understanding of the evolution of the SEI. The residual solids from the reaction mixtures have been characterized by a combination of X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy with attenuated total reflectance (IR-ATR), while the solution and evolved gases have been investigated by nuclear magnetic resonance (NMR) spectroscopy and gas chromatography with mass selective detection (GC-MS). The thermal decomposition of Li2CO3 and LiPF6 in DMC yields CO2, LiF, and F2PO2Li. The thermal decomposition of LMC and LEDC with LiPF6 in DMC results in the generation of a complicated mixture including CO2, LiF, ethers, phosphates, and fluorophosphates.

Clarification of Decomposition Pathways in a State‐of‐the‐Art Lithium Ion Battery Electrolyte through 13C‐Labeling of Electrolyte Components

“…Recently, Wang, Xu, Eichhorn and co‐workers corrected the previous assumption of lithium ethyl di‐carbonate (LEDC) as a main SEI component to the analogous monocarbonate species . Lithium ethyl monocarbonate (LEMC) presumably provides high reactivity and is an integral component of electrochemical degradation assumptions in this study …”

The Effects of Mechanical and Thermal Loads during Lithium‐Ion Pouch Cell Formation and Their Impacts on Process Time

“…A possible change of the morphology and the composition of the SEI at elevated temperatures is reported. This involves a growth and repairing caused by SEI dissolution . In terms of composition change, a conversion from metastable SEI components into more stable inorganic components is observed .…”

An ultrafast rechargeable lithium metal battery

“…The composition of C, O, F, and P is in agreement with previous literature exerting similar electrolyte. [25][26][27] The fitted C1s spectrum shows peaks related to -C-C-, ROCO2Li, and Li2CO3. The fitted O1s spectrum shows peaks related to C=O and C-O, which is consistent with the C1s spectrum.…”

“…F1s spectrum was fitted by LiF and LixPOyFz with peaks located at 685.0 and 686.7 eV respectively. 25 Besides, there also exists trace quantities of LixPOyFz and LiPF6 P-species as the contamination with weak intensity in XPS, which is corresponding to the EDX imaging of P in Figure S2. 26 Although the composition of SEI is similar to that of SEI formed in common electrolytes, there are some new compositions as shown in Li1s, N1s and Mn2p spectrum in Figure 1g.…”