In-Depth Interfacial Chemistry and Reactivity Focused Investigation of Lithium–Imide- and Lithium–Imidazole-Based Electrolytes

Abstract

A comparative and in-depth investigation on the reactivity of various Li-based electrolytes and of the solid electrolyte interface (SEI) formed at graphite electrode is carried out using X-ray photoelectron spectroscopy (XPS), chemical simulation test, and differential scanning calorimetry (DSC). The electrolytes investigated include LiX (X = PF6, TFSI, TDI, FSI, and FTFSI), dissolved in EC-DMC. The reactivity and SEI nature of electrolytes containing the relatively new imide (LiFSI and LiFTFSI) and imidazole (LiTDI) salts are evaluated and compared to those of well-researched LiPF6(-) and LiTFSI-based electrolytes. The thermal reactivity of LixC6 in the various electrolytes is found to be in the order of LiFSI > LiTDI > LiTFSI > LiFTFSI > LiPF6 and LiFSI > LiFTFSI > LiPF6 > LiTFSI > LiTDI in terms of onset exothermic temperature and total heat generated, respectively. Surface and depth-profiling XPS analysis of the SEI formed with the diverse electrolyte formulations provide insight into the differences and similarities (composition, thickness, and evolution, etc.) emanating from the structure of the various salt anions.

A Dual‐Salt Gel Polymer Electrolyte with 3D Cross‐Linked Polymer Network for Dendrite‐Free Lithium Metal Batteries

“…For the Li|LiFePO 4 battery using cross‐linked network‐GPE, a large amount of COR and COOR groups (Figure 5e) are found on the surface of Li metal anode, corresponding to —CH 2 —O and —CHOO— groups in the cross‐linked network structure, respectively 44. The ratio of COR and COOR agrees with the ratio of —CH 2 —O and —CHOO— groups approximately in the PEGDA and ETPEA mixture.…”

Study of the Formation of a Solid Electrolyte Interphase (SEI) on a Silicon Nanowire Anode in Liquid Disiloxane Electrolyte with Nitrile End Groups for Lithium‐Ion Batteries

“…On the outer layer of the SEI, the layer facing the electrolyte solution (defined as t sputter =0 minutes), we note the presence of Li 2 CO 3 as evident by peaks of C 1s at 290.1 eV, O 1s at 531.65 eV, and Li 1s at 55.1 eV . We also detect Li 2 O with its characteristic peaks of O 1s at 528.6 eV, and Li 1s at 54.45 eV . The Si−O bond has a very broad Si 2p peak at 100.95 eV.…”

“…We suggest that the addition of FEC resulted in mainly fluorinated‐rich SEI with LiF, and trapped LiTFSI . This is because the C 1s XPS spectrum is dominated by carbon‐fluorine bonds at 291.8 eV (LiTFSI, C‐F x ) and at 287.1 eV assigned to C−CF x .…”

A Comparison of Formation Methods for Graphite//LiFePO4 Cells

“…528 eV in Figure S4 in the Supporting information) of such an electrode. In the case of single‐ and dual‐current protocols a weak signal of lithiated graphite species Li x C 6 and/or lithium carbide (Li 2 C 2 ) is also detected at 282.4 eV ,. Carbonates (such as the stable Li 2 CO 3 and the metastable alkyl lithium carbonates, ROCO 2 Li) are found in all electrodes between 289.5 and 291 eV ,.…”

“…Carbonates (such as the stable Li 2 CO 3 and the metastable alkyl lithium carbonates, ROCO 2 Li) are found in all electrodes between 289.5 and 291 eV ,. The carbonates result from the EC and DMC decomposition reactions such as:,, …”