Al₂O₃ Fiber-Reinforced Polymer Solid Electrolyte Films with Excellent Lithium-Ion Transport Properties for High-Voltage Solid-State Lithium Batteries

Abstract

Composite solid electrolytes (CSEs) with high ionic conductivity and good interfacial compatibility are the basis for the practical application of solidstate lithium batteries. The combination of suitable polymers and inorganic fillers is the key to the preparation of CSEs with excellent performance. In this work, a flexible-rigid composite solid electrolyte film was prepared by incorporating different weight ratios (5−20 wt %) of γ-Al 2 O 3 fibers into flexible polypropylene oxide (PPO) polymer electrolytes. Due to the addition of γ-Al 2 O 3 fibers, the ion migration path is shortened and the ion migration rate is effectively improved. At the same time, the Lewis acid groups of γ-Al 2 O 3 fibers react with TFSI − to release more Li + , which increases the number of lithium-ion migration. Therefore, when the content of γ-Al 2 O 3 fibers is 15 wt %, the room-temperature ionic conductivity reaches 3.38 × 10 −4 S cm −1 , the ion migration number is 0.70, and the electrochemical window is 5.6 V. In addition, lithiophilic γ-Al 2 O 3 reacts with Li metal to generate a Li−Al−O transition layer, which promotes Li + interfacial transport and Li uniform deposition, and further inhibits the growth of Li dendrites. This Al 2 O 3 fiber-reinforced CSE improves the lithium-ion transport properties and interface stability between lithium and the electrolyte and has positive practical applications in solid-state lithium batteries.

Flexible self-supporting inorganic nanofiber membrane-reinforced solid-state electrolyte for dendrite-free lithium metal batteries

“…The formation of Li-Al-O compounds between the Li electrodes and the solid-state electrolyte as a homogeneous Li + conductive layer could effectively prevent the accumulation of Li + at the interface and greatly inhibit the growth of Li dendrites. 47,48 In addition, the enhancement of the PEO-based electrolytes by the Al 2 O 3 nanofibrous 3D skeleton structures was further demonstrated by probing the time for the short-circuit phenomenon to occur during the galvanostatic charging of PEO-LiTFSI electrolytes and AOM-PEO-LiTFSI electrolytes at a current density of 0.1 mA cm −2 . In comparison, the Al 2 O 3 nanofibrous membrane-reinforced composite solid-state electrolyte extended the continuous charging time to more than 10 h, whereas a short-circuit occurred after only 4 h of the charging process for the PEO-LiTFSI solid-state electrolyte (Fig.…”

“…The formation of Li–Al–O compounds between the Li electrodes and the solid-state electrolyte as a homogeneous Li + conductive layer could effectively prevent the accumulation of Li + at the interface and greatly inhibit the growth of Li dendrites. 47,48…”

The Critical Role of Fillers in Composite Polymer Electrolytes for Lithium Battery

“…Second, based on Lewis acid–base theory, the surface groups of passive fillers would interact with ion pairs to promote further dissociation. In recent decades, many passive fillers, including TiO 2 [ 66 ], Al 2 O 3 [ 67 ], SiO 2 [ 68 ] and ZrO 2 [ 69 ] , have been widely applied in CPEs owing to their advantages of easy synthesis, controllable size and stable physical and chemical stability. Table 2 shows typical passive fillers and their ionic conductivity.…”

Liquid Metal Loaded Molecular Sieve: Specialized Lithium Dendrite Blocking Filler for Polymeric Solid‐State Electrolyte

“…Combining inorganic fillers with a polymer matrix to establish the Lewis acid-based interactions between inorganicpolymer interface is an effective approach to kinetically suppress the crystallization of polymers with a lower T g , meanwhile enhancing Li ions transport, mechanical strength, and electrochemical stability. [16][17][18][19] Up to now, various fillers included inert ceramics: SiO 2 , [20] Al 2 O 3 , [21] and ceramic electrolytes: garnet Li 7 La 3 Zr 2 O 12 , [22] perovskite Li 0.33 La 0.56 TiO 3 [23,24] have been proven to effectively multiple-fold upgrade Li-ion conductivities. However, a peak enhancement of ionic conductivity is provided by the addition (normally under 20 wt%) of inert filler without the capability to transport Li ions, [25] where excessively high or low additions can affect the coherence and integrity of the modified interface network.…”