Impact of Fluorine‐Based Lithium Salts on SEI for All‐Solid‐State PEO‐Based Lithium Metal Batteries

Abstract

LiF‐rich solid‐electrolyte‐interphase (SEI) can suppress the formation of lithium dendrites and promote the reversible operation of lithium metal batteries. Regulating the composition of naturally formed SEI is an effective strategy, while understanding the impact and role of fluorine (F)‐based Li‐salts on the SEI characteristics is unavailable. Herein, LiFSI, LiTFSI, and LiPFSI are selected to prepare solid polymer electrolytes (SPEs) with poly(ethylene oxide) and polyimide, investigating the effects of molecular size, F contents and chemical structures (F‐connecting bonds) of Li‐salts and revealing the formation of LiF in the SEI. It is shown that the F‐connecting bond is more significant than the molecular size and F element contents, and thus the performances of cells using LiPFSI are slightly better than LiTFSI and much better than LiFSI. The SPE containing LiPFSI can generate a high amount of LiF, and SPEs containing LiPFSI and LiTFSI can generate Li3N, while there is no Li3N production in the SEI for the SPE containing LiFSI. The preferential breakage bonds in LiPFSI are related to its position to Li anode, where Li‐metal as the anode is important in forming LiF, and consequently the LiPFSI reduction mechanism is proposed. This study will boost other energy storage systems beyond Li‐ion chemistries.

A Fast Na‐Ion Conduction Polymer Electrolyte via Triangular Synergy Strategy for Quasi‐Solid‐State Batteries

“…52 Undoubtedly, the limiting effect of Nerolin on the ionic liquid resulted in the NaTFSI salt‐dominated decomposition at the interface, leading to an organic‐F‐rich and thinner interphase, thereby enhancing Na + transport (Figure 4g). These findings demonstrate that the triangular synergy strategy could promote rapid Na + transport through the bulk phase of the polymer electrolyte and the interphase at room temperature [25] …”

“…These findings demonstrate that the triangular synergy strategy could promote rapid Na + transport through the bulk phase of the polymer electrolyte and the interphase at room temperature. [25] To assess the practicality of FNCPE electrolyte in quasisolid-state batteries, NajjNVP cells were assembled without extra liquid electrolyte (Figure 5a). At room temperature, the NajjNVP cells using FNCPE maintained a capacity of 87.6 mAh g À 1 at 3 C, while the NajjNVP cells with PE only retained 43.6 mAh g À 1 at the same C rate (Figures 5b, c).…”

Cryo-ultramicrotomy enables TEM characterization of global lithium/polymer interfaces

“…S18, ESI†). Prior investigations have elucidated that PEO undergoes degradation under high voltage conditions at the cathode, 32–35 while lithium salts preferentially acquire electrons under low voltage levels at the anode, 36,37 thereby engaging in interface reactions that lead to their degradation. In this study, however, the inorganic components within the SEI predominantly manifest as LiOH, Li 2 CO 3 , and Li 2 O species.…”

The Versatile Establishment of Charge Storage in Polymer Solid Electrolyte with Enhanced Charge Transfer for LiF‐Rich SEI Generation in Lithium Metal Batteries

“…Figure 5e and Table S4 compares the cycling performance of reported polymeric solid electrolytes. [37][38][39][40][41][42][43][44] Moreover, by varying the current density from 0.1 to 0.2, 0.5, 1 and 2 C (Figure 5d), the discharge capacity of the PEO-POF cells was increased by 166.8, 154.3, 146.8, 137.4 and 123.6 mAh g À 1 . When the current density was returned to 0.1 C, the reversible charge/discharge capacity of the PEO-POF cell was still as high as 162.8 mAh g À 1 , which showed a very good multiplicative performance.…”