Organic–Inorganic Composite Electrolytes Optimized with Fluoroethylene Carbonate Additive for Quasi-Solid-State Lithium-Metal Batteries

Abstract

Composite solid electrolytes (CSEs) are considered crucial materials for next-generation solid-state lithium batteries with high energy density and reliable safety, and they make full use of the advantages of both organic and inorganic solid-state electrolytes. However, few CSEs have sufficiently high ionic conductivity at room temperature for practical applications. Here, a traditional CSE consisting of poly­(ethylene oxide) (PEO) matrix and Li1.3Al0.3Ti1.7(PO4)3 (LATP) fillers was optimized by introducing a fluoroethylene carbonate (FEC) additive, resulting in an improved high ionic conductivity of 1.99 × 10–4 S cm–1 at 30 °C. The symmetric Li||Li cell assembled with the optimized CSE exhibited a low overpotential and a good cycling stability of more than 1500 h at room temperature. Moreover, the Li||LiFePO4 battery with the optimized CSE delivered a discharge capacity of 132 mAh g–1 at 0.2 C after 300 cycles at room temperature. Comparisons between the LATP-containing CSE and control electrolytes indicated that the enhanced ion conductivity of the former resulted from the synergistic effect of LATP and FEC. Comprehensive characterizations and DFT calculations suggest that with the presence of LATP, FEC additives in the precursor could transform into some other species in the preparation process of CSE. It is believed that these FEC-derived species improve the ion conductivity of the CSEs. The results reported here may open up new approaches to developing composite electrolytes with high ionic conductivity at room temperature by introducing organic additives in the precursor and converting them into species that facilitate ion conduction in the CSE preparation process.

Tailoring of Li/LATP-PEO Interface via a Functional Organic Layer for High-Performance Solid Lithium Metal Batteries

“…In contrast, the symmetric cell based on the PEO-LATP CSE maintains only ∼350 h followed by short circuit, and a bigger overpotential of ∼320 mV is obtained. These results are similar to or even superior to many reported works (Table S4, Supporting Information), ,,,,,− suggesting that the as-prepared PEO-LATP@SI-6 CSE has better Li compatibility. Figure (b) displays the polarization voltage of the Li||PEO-LATP@SI-6 CSE||Li symmetric cell at different current densities.…”

“…It can be seen that only characteristic peaks of Ti 4+ located at 459.6 and 465.6 eV can be detected for initial LATP and LATP@SI. 20 After being contacted for 20 h, characteristic peaks of Ti 3+ located at 458.2 and 463.2 eV appear, 21,32 and the relative content of Ti 3+ increases with the increase of storing time. The phenomenon suggests that Ti 4+ in LATP was reduced by Li metal, and LATP is chemically incompatible with the Li metal anode when they are directly contact to each other.…”

Working Principles of Lithium Metal Anode in Pouch Cells

“…Composite SSE composed of organic and inorganic materials is promising to address the inherent problems related to the poor mechanical properties of solid-state polymer electrolytes and the poor flexibility and high interfacial resistance of solid-state inorganic electrolytes. [218,219] The combination of the polymer matrix and the inorganic components mainly leads to the complementary effects in the composite SSE, especially when the polymer matrix is doped with a certain amount of inorganic substances. [220] The addition of the Li 7 La 3 Zr 2 O 12 (LLZO)-based garnet-type SSE into the poly(ethylene oxide) (PEO) matrix is expected to yield an LLZO-PEO composite SSE with excellent performance in pouch cells.…”

Recent Advances in Conduction Mechanisms, Synthesis Methods, and Improvement Strategies for Li1+xAlxTi2−x(PO4)3 Solid Electrolyte for All‐Solid‐State Lithium Batteries

“…In this regard, Li et al introduced a conventional fluoroethylene carbonate (FEC) additive into composite electrolytes consisting of PEO matrix and LATP fillers; (Figure 17c) FEC-derived species were generated from the interaction between FEC and LATP; and thus, resulted in an improved high ionic conductivity of 1.99 × 10 −4 S cm −1 at 30 °C. [196] Figure 16. a) The thermal stability and heat runaway mechanism of Li-containing metal oxide SES.…”

“…Reproduced with permission. [196] Copyright 2022, American Chemical Society. d) Li transport mechanism of composite electrolyte.…”