Freestanding Trilayer Hybrid Solid Electrolyte with Electrospun Interconnected Al-LLZO Nanofibers for Solid-State Lithium-Metal Batteries
Tadesu Hailu Mengesha, Shimelis Lemma Beshahwured, She‐Huang Wu, Yi–Shiuan Wu, Rajan Jose, Shingjiang Jessie Lue, Chun‐Chen Yang
Abstract
Energy storage devices that are safe to use and thermally stable and have a wide working electrochemical window and high specific capacity would be a boon to modern society. All-solid-state lithium-metal batteries (ASSLMBs) are promising devices for energy storage because they fulfill these requirements. In this study, we used a solution-casting method to synthesize a freestanding trilayer hybrid solid-state electrolyte (Tri-HSE) membrane from a suspension of interconnected Li6.28La3Zr2Al0.24O12 (Al-LLZO, as the filler), poly(vinylidene fluoride)/poly(ethylene carbonate) (PVDF/PEC, as the blended polymer), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, as the salt), and succinonitrile (SN, as the plasticizer). The as-prepared Tri-HSE membrane exhibited a high ionic conductivity (ca. 3.91 × 10–4 S cm–1 at 25 °C), a high Li transference number (ca. 0.78), and a high tensile strength (ca. 11.36 MPa). The symmetric cell (Li/Tri-HSE/Li) was stable during Li plating/stripping cycles for 470 h without any short-circuiting. The assembled NCM811/Tri-HSE/Li full cell operated between 2.6 and 4.2 V cut-off voltages, displaying a high initial discharge capacity (162.59 mAh g–1) and a high capacity retention (92.41%) after 100 cycles at a rate of 0.1C. Also, at a rate of 0.2C, it displayed admirable capacity retentions and average Coulombic efficiencies of 87.52, 83.40 and 99.21, 99.47%, after 450 and 250 cycles, at 4.2 and 4.3 V cut-off voltages, respectively. Moreover, the 5 × 3 cm2 dimensional pouch cell assembled using the same membrane reveals an average Coulombic efficiency and capacity retention of 99.53 and 95.58% after 30 cycles, respectively. Therefore, this as-synthesized Tri-HSE membrane─characterized by high flexibility, ionic conductivity, mechanical strength, wide electrochemical window, and low in situ heat generation─appears to be a promising solid-state electrolyte for upcoming generations of lithium-metal batteries operated at room temperature.