Tailoring Electrolyte Additives with Synergistic Functional Moieties for Silicon Negative Electrode-Based Lithium Ion Batteries: A Case Study on Lactic Acid O-Carboxyanhydride

Abstract

Silicon (Si) has attracted much attention to be applied as a negative electrode (N) material for lithium ion batteries (LIBs) with increased energy density. However, the huge volume changes during (de-)­lithiation of the Si, accompanied with the breakdown of the initially formed solid electrolyte interphase (SEI), result in the gradual consumption of active lithium and electrolyte and, hence, a poor cycling performance of LIBs with Si-based N. The addition of various electrolyte additives was proven to be able to reduce the active lithium consumption by the formation of a more effective/flexible and, therefore, better protecting SEI on the Si. Within this study, we synthesize the new electrolyte additive lactic acid O-carboxyanhydride (lacOCA), which is designed to incorporate two different moieties within its structure, that both show to function as effective SEI additives. The addition of small amounts of 2 wt % of lacOCA to the baseline electrolyte significantly improves the electrochemical performance of NMC-111||Si full cells in terms of discharge capacity retention and Coulombic efficiency. The lacOCA also outperforms the comparable additives lactide and diethyl dicarbonate, which are chosen to individually represent the moieties incorporated within the lacOCA structure, proving the synergistic effect of the two different moieties, when in one molecule. Ex situ investigations of the SEI by means of X-ray photoelectron spectroscopy and attenuated total reflectance Fourier transform infrared spectroscopy reveal that the SEI formed by lacOCA is mainly composed of poly­(lactic acid) and lithium carbonate, which enables a significant reduced consumption of active lithium during charge/discharge cycling of the NMC-111||Si full cells.

A Thorough Analysis of Two Different Pre‐Lithiation Techniques for Silicon/Carbon Negative Electrodes in Lithium Ion Batteries

“…The peak at 533.5 eV is at most present as a small shoulder, thus, a SEI layer seems to cover the surface of the electrodes, as the information depth of XPS is ≈10 nm. In the spectrum of the pre‐lithiated electrode by Li metal, an additional peak is present at ≈528 eV, which is related to small quantities of the inorganic species Li 2 O formed in the SEI layer [22b,25a,26] …”

“…In the C 1s spectra, a major peak at 284.5 eV (C−C, C−H) is present for the pre‐lithiated electrodes, which is attributed to alkane species incorporated in the SEI resulting from decomposition products of the organic electrolyte [22b] . The spectrum of the pristine Si/C electrode exhibits a broad peak in this BE region, which is related to C−C, C−H and C−O environments arising from the PAA binder [24b,26,27] .…”

Production of high-energy Li-ion batteries comprising silicon-containing anodes and insertion-type cathodes

“…To avoid severe safety issues and critical challenges linked to the direct utilisation of solid CO 2 (dry ice) in pouch cells before battery sealing, the use of in situ (electro)chemically CO 2 releasing additives (e.g. 5-methyl-1,3-dioxolane-2,4-dione (lacOCA) 65 ) has been reported in the literature.…”

Interfacing Si‐Based Electrodes: Impact of Liquid Electrolyte and Its Components

“…Furthermore, addition of LAC leads to an increased ratio of lithium fluorophosphates to LiF in the SEI. [136] Pentafluorophenyl Isocyanate (PFPI): Nölle et al studied PFPI as an additive to conventional electrolytes for Si thin film electrodes in NMC111||Si cell configuration. The study demonstrated that addition of 2 wt% to the baseline electrolyte has a similarly beneficial effect as the addition of 2 wt% of VC or FEC.…”

“…XPS analysis revealed that the amount of lithium fluorophosphate species in the SEI was significantly reduced and evidence of simultaneous formation of poly(lactic acid) (PLA) and Li 2 CO 3 as the main SEI components was found. [ 136 ]…”