Activating ultra-low temperature Li-metal batteries by tetrahydrofuran-based localized saturated electrolyte

Abstract

For realizing the commercialization of Li-metal batteries (LMBs), the discharge-blocking obstacles under ultra-low temperatures must be conquered besides the long-term reversibility. Nevertheless, commercial carbonate-based electrolytes are not only incompatible with the aggressive Li anode, but also have poor fluidity at low temperatures. The prevailing chain-ether-based electrolyte designing tactics, such as the common-used DME, improve the affinity with Li metal to some extent, but the multiple Lewis-acid binding sites of chain ethers are not conducive to the de-solvation of Li+. Herein, for the first time, the cheap cyclic-type tetrahydrofuran (THF) with ultra-low melting point and weak solvating power is adopted for designing an original THF-based localized saturated electrolyte (Tb-LSCE), demonstrating excellent adaptability for low-temperature LMBs. Computational and experimental evidence verify the original solvated structure is modified via the addition of fluorinated antisolvent, further contributing to the Li+-THF de-solvation. Therefore, equipped with Tb-LSCE, the assembled Li-NCM523 cells achieve powerful anti-polarization capability at low temperatures (73.3% discharge capacity retention at -30 °C). Furthermore, the unique solvated sheath structure of Tb-LSCE also regulates the interfacial chemistry and uniformity of Li depositing behavior, highlighted by the outstanding reversibility of Li-Li cells (a long lifespan of exceeding 1600 h at 30 °C and 1100 h at -30 °C, respectively) and Li-NCM523 cells (80.7%, 160 cycles) even remarkably stable operation within 50 cycles (ultra-high cathode loading of 19.7 mg cm−2). This work outlines a cheap and effective electrolyte design solution to activate the potential LMBs under practical conditions, especially those operated under cryogenic environments.