Synergy of an In Situ-Polymerized Electrolyte and a Li₃N–LiF-Reinforced Interface Enables Long-Term Operation of Li-Metal Batteries

Abstract

The long-term operation of a Li-metal anode remains a great challenge due to the severe dendrite growth in an organic liquid electrolyte. To protect a Li-anode surface from continuous corrosion by an electrolyte, a consistent and robust solid electrolyte interface (SEI) is an essential prerequisite. This work proposes a secure gel polymer electrolyte, which is in situ constructed via a facile polymerization process of vinylidene carbonate inside Li-metal batteries. The liquid components that are not involved in polymerization are well entrapped in the poly(vinyl carbonate) framework, leading to a high oxidative stability of up to 4.5 V (vs Li/Li + ). A Li 3 N−LiFreinforced SEI resulting from the reduction of fluoroethylene carbonate and lithium nitrate additives has a synergistic effect on the suppression of Lidendrite growth. The densely packed Li deposition behavior is revealed by in situ/ex situ microscopic observations. Steady cycling of over 2500 h with a relatively low voltage hysteresis is achieved by the Li||Li symmetric cells. A Coulombic efficiency above 96% upon long-term cycling is available for the asymmetric Li||Cu cells. The smooth operation of batteries with commercial LiFePO 4 cathodes further indicates that the SEI with homogeneity in composition and structure prompts Li deposition with alleviative dendrites.

Fluorinated carbon nitride with a hierarchical porous structure ameliorating PEO for high-voltage, high-rate solid lithium metal batteries

“…5f). 22 Moreover, the peak of LiOH/Li 2 CO 3 /RO-Li is significantly reduced (consistent with the O 1s spectrum at 531.5 eV), while the peak of Li 2 O increased (consistent with the O 1s spectrum at 528.6 eV) (Fig. 5g).…”

“…The integration of LiF and Li 3 N to construct a Li 3 N-rich and LiF-rich composite SEI would considerably inhibit the formation of lithium dendrites. 20–25 For example, Li 3 PS 4 electrolyte coated with a Li 3 N–LiF composite layer shows a significant suppression effect on Li dendrites; 20 a Li 3 N–LiF interface layer formed in PEO/LiTFSI which is ameliorated by mesoporous La x CoO 3 − δ nanofibers allows for stable cycling even when it was matched with a LiNi 0.8 Mn 0.1 Co 0.1 O 2 cathode. 25 However, the preparation processes above need either strict fabrication conditions or using expensive rare earth elements, and thus they are unsuitable for large-scale commercial manufacturing.…”

Fluorine- and Nitrogen-Donating Gel Polymer Electrolytes Enabling LiF- and Li3N-Enriched SEI for Stabilizing Lithium Metal Anodes

“…In the Li 1 s spectra, LiF (56.10 eV), Li 3 N (55.20 eV), and LiN x O y (55.60 eV) are observed on the Li metal anode with the 2N1F-50 electrolyte. In the N 1 s spectra, the peaks assigned to Li 3 N and NO x can be found, and the detected LiF and C–F are clear in the F 1 s spectra, indicating that the SEI is mainly composed of LiF, Li 3 N, and LiN x O y . The results suggest that 2N1F-50 undergoes decomposition to form a uniform and dense LiF-based SEI, which can inhibit side reactions between the Li metal and 2N1F-50.…”

“…In the N 1 s spectra, the peaks assigned to Li 3 N and NO x can be found, and the detected LiF and C−F are clear in the F 1 s spectra, indicating that the SEI is mainly composed of LiF, Li 3 N, and LiN x O y . 57 The results suggest that 2N1F-50 undergoes decomposition to form a uniform and dense LiF-based SEI, which can inhibit side reactions between the Li metal and 2N1F-50. To deeply investigate the role of HFBMA in forming the SEI, XPS analysis was conducted on the Li/PVDF/Li cell.…”

Progress and perspectives of in situ polymerization method for lithium‐based batteries

“…As a frequently used unsaturated additive in liquid electrolytes, VC with a unique framework containing functional groups of C═O and C═C bonds in the five-membered ring, can be easily polymerized on the surface of the electrodes to form PVC-based in situ GPEs. [43][44][45][46] As shown in Figure 3A, the in situ polymerization of LiFe 0.2 Mn 0.8 PO 4 |GPE|C full cells using precursors containing solutions of 1 M lithium difluoro(oxalato) borate (LiDFOB) in VC, solutions of 1 M LiDFOB in EC/diethyl carbonate (1:1), and thermal initiators were reported by Chai et al [43] The X-ray diffraction pattern of GPEs displayed a bread peak in the range of 2θ = 23°, which verified that the GPEs were amorphous at room temperature, leading to the increase of ionic conductivity (5.59 × 10 −4 S cm −1 at 25°C). The electrochemical stability window tested by the linear sweep voltammetry measurements (LSV) of PVC-based GPEs (4.8 V) was higher than that of pristine liquid electrolyte (4.5 V), indicating that polymerization could obviously increase oxidative stability.…”