Advanced Model for Solid Electrolyte Interphase Electrodes in Liquid and Polymer Electrolytes

Abstract

Recent studies show that the SEI on lithium and on LixC6 anodes in liquid nonaqueous solutions consists of many different materials including Li2O , LiF, LiCl, Li2CO3,LiCO2‐R , alkoxides, and nonconducting polymers. The equivalent circuit for such a mosaic‐type SEI electrode is extremely complex. It is shown that near room temperature the grain‐boundary resistance (R gb) for polyparticle solid electrolytes is larger than the bulk ionic resistance. Up to now, all models of SEI electrodes ignored the contribution of R gb to the overall SEI resistance. We show here that this neglect has no justification. On the basis of recent results, we propose here for SEI electrodes equivalent circuits which take into account the contribution of grain‐boundary and other interfacial impedance terms. This model accounts for a variety of different types of Nyquist plots reported for lithium and LixC6 electrodes in liquid nonaqueous and polymer electrolytes.

New Insight into the Solid Electrolyte Interphase with Use of a Focused Ion Beam

“…In the range of 0 to 1, the ELSA curves of F and O show a gradual decrease, indicating that species such as LiF and Li 2 O have a gradient distribution with the depth increment; as for C, its content remains nearly unchanged, which suggests that organic species from decomposition of EC/DMC may dominate this part. On the basis of these changes, it seems more likely that the SEI film is a mosaic of polyheteromicrophases as proposed by Peled et al 4,5 In the range of 1 to 2, the content of F remains basically stable, but O and C decrease gradually. This is consistent with our former observations that there is a similar composition between the freshly formed outer SEI film and the "internal SEI film", in which fluorides such as LiF from the salt reduction predominate and organic compounds decrease gradually.…”

Selecting the Best Graphite for Long-Life, High-Energy Li-Ion Batteries

“…Moreover, new peaks at 686.2 eV in the F 1s spectra were also identified in all cycled anodes, which suggests the formation of inorganic SEI components likes LiF and PO y F z from LiPF 6 salt decomposition. 56,57 This was further confirmed from the slightly asymmetric Li 1s peak 58 and the presence of P. Of particular interest is that the SEI components were distinctly different in each cycled graphite anode, though no strong correlation was revealed with capacity retention. SLC 1520T, MAGE, and MAGE3 appeared to have more inorganic species like LiF and PO y F z than SCMG-BH, APS, or A12.…”

Electrochemical Performance and Thermal Stability Studies of Two Lithium Sulfonyl Methide Salts in Lithium-Ion Battery Electrolytes

“…11,[19][20][21][22][23][24][25] However, with increasing demands on the electrolyte regarding thermal and/or electrochemical stability, the limitations of such electrolyte mixtures are unraveled. 11,26,27 Alternative electrolyte compositions that depict certain improvements compared to the state-of-the-art electrolyte are still required to fulfil the following properties: a sufficient ionic conductivity to transport the lithium ions, the ability to form an effective solid electrolyte interphase (SEI) on the graphitic anode [28][29][30][31][32][33][34][35][36][37] which enables stable cycling in the low potential range as well as inertness toward aluminum to avoid anodic dissolution of the current collector on the cathode side. 38,39 In addition to performance, more general aspects like low price and environmental compatibility are important as well.…”