Tailoring Electrolyte Solvation Chemistry toward an Inorganic-Rich Solid-Electrolyte Interphase at a Li Metal Anode

Abstract

The solid-electrolyte interphase (SEI) is known to dictate the performance of a Li metal anode, where its inorganic compositions are primarily responsible for Li + conduction, electron insulation, and thus a compact Li deposition. In this work, we formulate a nonflammable and highly fluorinated electrolyte recipe for a highly reversible Li metal anode. By concurrently incorporating the F-donating anions and solvent molecules into the primary Li + solvation sheath, an inorganic-rich SEI with high F content is produced. The low solvation energy of the tailored solvation sheath further reduces the barrier for Li + desolvation, contributing to accelerated kinetics under fast charging and subzero conditions. Consequently, dramatic improvements in the Li deposition morphology, Coulombic efficiency (98% over 650 cycles), and Li + desolvation/transfer kinetics are obtained. Full cells pairing with the commercial LiFePO 4 (LFP) and LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523) cathodes show stable cyclability at both room-temperature and subzero conditions. Further electrolyte prototypes are showcased to demonstrate the universality of the design principle provided herein.

Anion‐Reinforced Solvation for a Gradient Inorganic‐Rich Interphase Enables High‐Rate and Stable Sodium Batteries

“…In comparison, FSI − anions extensively enter the Na + inner solvation sheath in HCE and LHCE, and present high intensity of Na‐O FSI pairs. The pronounced peak intensity of Na‐O FSI pairs in LHCE indicates the reinforced Na + ‐FSI − interaction [14] . The dominant coordination of Na + with the surrounding DME and FSI − or OTE in DE, HCE, and LHCE are shown in Figure 1d.…”

“…The pronounced peak intensity of Na-O FSI pairs in LHCE indicates the reinforced Na + -FSI À interaction. [14] The dominant coordination of Na + with the surrounding DME and FSI À or OTE in DE, HCE, and LHCE are shown in Figure 1d. Both of the inner sheaths of HCE and LHCE involve DME and FSI À , however the distance between Na + and FSI À is decreased from 2.48 to 2.34 Å in LHCE with OTE.…”

“…The increment of free DME induced by OTE in LHCE reinforces the Na + solvation sheath with more FSI − anions. As shown in Figure S10, the lower energy level of the lowest unoccupied molecular orbital (LUMO) of Na(DME) 2 FSI (−1.07 eV) than that of Na(DME) 3 + (−0.34 eV) indicates the prior decomposition of Na(DME) 2 FSI, and favors the formation of FSI − derived SEI with inorganic species at high potentials, which suppresses further solvent reduction [14, 16] …”

Structural regulation chemistry of lithium ion solvation for lithium batteries

“…The excellent performance of LHCE mainly depends on the quality of the anion‐derived SEI, namely, it is related to the degree of anion decomposition 90–92 . Ren et al 48 explored the LHCEs based on lithium bis(fluorosulfonyl)imide (LiFSI) dissolved in dimethyl carbonate (DMC), tetramethylene sulfone (TMS), triethyl phosphate (TEP), and DME solvents with TTE diluent for NCM811 at a high cutoff voltage of 4.4 V, respectively.…”

“…65 Reproduced with permission: 2015, American Association for the Advancement of Science 65 related to the degree of anion decomposition. [90][91][92] Ren et al 48 explored the LHCEs based on lithium bis(fluorosulfonyl)imide (LiFSI) dissolved in dimethyl carbonate (DMC), tetramethylene sulfone (TMS), triethyl phosphate (TEP), and DME solvents with TTE diluent for NCM811 at a high cutoff voltage of 4.4 V, respectively. The DME-based LHCE exhibited the best cycle performance, since the anode surface with higher F and N signals and the least second particle microcracks on the cathode with thin CEI (Figure 2A).…”