Nonsacrificial Additive for Tuning the Cathode–Electrolyte Interphase of Lithium-Ion Batteries

Abstract

Solid–electrolyte interphases is essential for stable cycling of rechargeable batteries. The traditional approach for interphase design follows the decomposition of additives prior to the host electrolyte, which, as governed by the thermodynamic rule, however, inherently limits the viable additives. Here we report an alternative approach of using a nonsacrificial additive. This is exemplified by the localized high-concentration electrolytes, where the fluoroethylene carbonate (FEC) plays a nonsacrificial role for modifying the chemistry, structure, and formation mechanism of the cathode–electrolyte interphase (CEI) layers toward enhanced cycling stability. On the basis of ab initio molecular dynamics simulations, we further reveal that the unexpected activation of the otherwise inert species in the interphase formation is due to the FEC–Li+ coordinated environment that altered the electronic states of reactants. The nonsacrificial additive on CEI formation opens up alternative avenues for the interphase design through the use of the commonly overlooked, anodically stable compounds.

Pinned Electrode/Electrolyte Interphase and Its Formation Origin for Sulfurized Polyacrylonitrile Cathode in Stable Lithium Batteries

“…It is speculated that the LiFSI salt in LFSI-ether electrolyte shows no significant decomposition but just suffers a breakage of S–N bonds to form SO 2 F and/or N-SO 2 F. This agrees well with our recent work, in which it is found that the S–N bond will break first when the FSI – anion is oxidized and the primary decomposition products of FSI – anion in CEI are SO 2 F (or N-SO 2 F) . This is also consistent with the previous report that, in the FSI – anion structure, the N–S bond is the weakest bond (192.7 kJ mol –1 ), while the F–S bond is much stronger (652.3 kJ mol –1 ), indicating that the FSI – anion could prefer to decompose to form the fragments of SO 2 F and/or N-SO 2 F . The limited LiF species is more likely from the decomposition of TTE or the reaction between TTE and active lithiation product Li 2 S 2 , which will be discussed in following sections.…”

“…), indicating that the FSI − anion could prefer to decompose to form the fragments of SO 2 F and/or N-SO 2 F. 38 The limited LiF species is more likely from the decomposition of TTE or the reaction between TTE and active lithiation product Li 2 S 2 , which will be discussed in following sections.…”

Applying Classical, Ab Initio, and Machine-Learning Molecular Dynamics Simulations to the Liquid Electrolyte for Rechargeable Batteries

“…Cations are small in size with high positive charge densities, and aprotic polar solvents commonly used in electrolytes possess strong nucleophilic sites (e.g., carbonyl oxygen). Therefore, solvents have the potential to compete with anions for the cation solvation, − forming solvation shells in electrolytes (Figure a). This phenomenon has been verified by many experimental characterizations. − MD simulations allow a concrete observation of the solvation structures of cations at the microscopic level (Figure b) .…”

Improving Li Ion Storage Capability of V2O5 Electrode by Using Aminoalkyldisiloxane Electrolyte Additive

“…A uniform CEI layer about ∼12 nm was found on the surface of the V 2 O 5 electrode in the DSON‐containing electrolyte and the separator showed a clean surface without dark powders on it. Such homogeneous and thin CEI film indicate that the deposited sediments from the electrolyte are not incorporated into the V 2 O 5 interphase, providing effective protection for V 2 O 5 electrode from crystal structure and valid suppression of the electrolyte decomposition [17] . Thus, the SAED image for V 2 O 5 electrode cycled in the DSON‐containing electrolyte shows unambiguous diffraction spots (Figure 2l).…”