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HKUST-1@IL-Li Solid-state Electrolyte with 3D Ionic Channels and Enhanced Fast Li⁺ Transport for Lithium Metal Batteries at High Temperature.

ABSTRACT: The challenge of safety problems in lithium batteries caused by conventional electrolytes at high temperatures is addressed in this study. A novel solid electrolyte (HKUST-1@IL-Li) was fabricated by immobilizing ionic liquid ([EMIM][TFSI]) in the nanopores of a HKUST-1 metal-organic framework. 3D angstrom-level ionic channels of the metal-organic framework (MOF) host were used to restrict electrolyte anions and acted as "highways" for fast Li⁺ transport. In addition, lower interfacial resistance between HKUST-1@IL-Li and electrodes was achieved by a wetted contact through open tunnels at the atomic scale. Excellent high thermal stability up to 300 °C and electrochemical properties are observed, including ionic conductivities and Li⁺ transference numbers of 0.68 × 10^-4 S·cm^-1 and 0.46, respectively, at 25 °C, and 6.85 × 10^-4 S·cm^-1 and 0.68, respectively, at 100 °C. A stable Li metal plating/stripping process was observed at 100 °C, suggesting an effectively suppressed growth of Li dendrites. The as-fabricated LiFePO₄/HKUST-1@IL-Li/Li solid-state battery exhibits remarkable performance at high temperature with an initial discharge capacity of 144 mAh·g^-1 at 0.5 C and a high capacity retention of 92% after 100 cycles. Thus, the solid electrolyte in this study demonstrates promising applicability in lithium metal batteries with high performance under extreme thermal environmental conditions.

SUBMITTER: Li M

PROVIDER: S-EPMC7999087 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Fluorinated electrolytes based on fluoroethylene carbonate (FEC) have been considered as promising alternative electrolytes for high-voltage and high-energy capacity lithium-ion batteries (LIBs). However, the compatibility of the fluorinated electrolytes with graphite negative electrodes is unclear. In this paper, we have systematically investigated, for the first time, the stability of fluorinated electrolytes with graphite negative electrodes, and the result shows that unlike the ethylene carbonate (EC)-based electrolyte, the FEC-based electrolyte (EC was totally replaced by FEC) is incapable of forming a protective and effective solid electrolyte interphase (SEI) that protects the electrolyte from runaway reduction on the graphite surface. The reason is that the lowest unoccupied molecular orbital energy levels are also lowered by the introduction of fluorine into the solvent, and the FEC solvent has poorer resistance against reduction, leading to instability on the graphite negative electrode. To tackle this problem, two lithium salts of lithium bis(oxalato)borate and lithium difluoro(oxalato)borate (LiDFOB) have been investigated as negative-electrode film-forming additives. Incorporation of only 0.5 wt % LiDFOB to a FEC-based electrolyte [1.0 M LiPF6 in 3:7 (FEC-ethyl methyl carbonate)] results in excellent cycling performance of the graphite negative electrode. This improved property originates from the generation of a thinner and better quality SEI film with little LiF by the sacrificial reduction of the LiDFOB additive on the graphite negative electrode surface. On the other hand, this additive can stabilize the electrolyte by scavenging HF. Meanwhile, the incorporated LiDFOB additive has positive influence on the interphase layer on the positive electrode surface and significantly decreases the amount of HF formation, finally leading to improved cycling stability and rate capability of LiNi0.5Mn1.5O4 electrodes at a high cutoff voltage of 5 V. The data demonstrate that the LiDFOB additive not only exhibits a superior compatibility with graphite but also improves the electrochemical properties of high-voltage spinel LiNi0.5Mn1.5O4 positive electrodes considerably, confirming its potential as a prospective, multifunctional additive for 5 V fluorinated electrolytes in high-energy capacity lithium-ion batteries (LIBs).

Project description:With the development of mobile electronic devices, there are more and more requirements for high-energy storage equipment. Traditional lithium-ion batteries, like lithium-iron phosphate batteries, are limited by their theoretical specific capacities and might not meet the requirements for high energy density in the future. Lithium-sulfur batteries (LSBs) might be ideal next-generation energy storage devices because they have nearly 10 times the theoretical specific capacities of lithium-ion batteries. However, the severe capacity decay of LSBs limits their application, especially at high currents. In this study, an ionic liquid (IL) electrolyte additive, TDA+TFSI, was reported. When 5% of the TDA+TFSI additive was added to a traditional ether-based organic electrolyte, the cycling performance of the LSBs was significantly improved compared with that of the LSBs with the pure traditional organic electrolyte. At a rate of 0.5 C, the discharge specific capacity in the first cycle of the LSBs with the 5% TDA+TFSI electrolyte additive was 1167 mAh g-1; the residual specific capacities after 100 cycles and 300 cycles were 579 mAh g-1 and 523 mAh g-1, respectively; and the average capacity decay rate per cycle was only 0.18% in 300 cycles. Moreover, the electrolyte with the TDA+TFSI additive had more obvious advantages than the pure organic ether-based electrolyte at high charge and discharge currents of 1.0 C. The residual discharge specific capacities were 428 mAh g-1 after 100 cycles and 399 mAh g-1 after 250 cycles, which were 13% higher than those of the LSBs without the TDA+TFSI additive. At the same time, the Coulombic efficiencies of the LSBs using the TDA+TFSI electrolyte additive were more stable than those of the LSBs using the traditional organic ether-based electrolyte. The results showed that the LSBs with the TDA+TFSI electrolyte additive formed a denser and more uniform solid electrolyte interface (SEI) film during cycling, which improved the stability of the electrochemical reaction.

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HKUST-1@IL-Li Solid-state Electrolyte with 3D Ionic Channels and Enhanced Fast Li⁺ Transport for Lithium Metal Batteries at High Temperature.

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HKUST-1@IL-Li Solid-state Electrolyte with 3D Ionic Channels and Enhanced Fast Li+ Transport for Lithium Metal Batteries at High Temperature.

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OmicsDI is part of the ELIXIR infrastructure

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HKUST-1@IL-Li Solid-state Electrolyte with 3D Ionic Channels and Enhanced Fast Li⁺ Transport for Lithium Metal Batteries at High Temperature.