Electrospinning Equipment for Research| Al-doped garnet nanofiber-reinforced cathode-supported composite solidelectrolyte membranes for advanced all solid-state lithium batteries

 Prof. Chen Xinzhi from Kunming University of Science and Technology: Cathode-Supported Composite Solid Electrolyte Membrane Reinforced by Garnet Ceramic Nanofibers

As important electrochemical energy conversion and storage devices, rechargeable lithium-ion batteries (LIBs) hold an irreplaceable position in intermittent renewable energy storage due to their high energy density and long cycle life. However, traditional LIBs predominantly use organic liquid electrolytes, which exhibit flammability, poor chemical stability, and volatility—particularly under high temperatures—posing significant safety risks. Additionally, side reactions between liquid electrolytes and lithium metal anodes lead to interfacial instability and lithium dendrite growth, compromising battery lifespan and safety.To address these issues, solid-state electrolytes (SSEs) have emerged as a critical direction for improving battery safety and stability. Yet, existing SSEs still face challenges such as low ionic conductivity and high electrode-electrolyte interfacial resistance, severely limiting the large-scale application of all-solid-state lithium-ion batteries (ASSLIBs).

Recently, Prof. Chen Xinzhi’s team at the Yunnan Provincial Key Laboratory of Energy Saving in Phosphorus Chemical Engineering and New Materials published a study titled "Al-doped garnet nanofiber-reinforced cathode-supported composite solid electrolyte membranes for advanced all solid-state lithium batteries" in the Journal of Energy Storage. The research developed a novel cathode-supported composite solid electrolyte (CSE) membrane via electrospinning and tape-casting processes, based on polyethylene oxide (PEO) and Al-doped garnet ceramic nanofibers (Li7La3Zr2O12, LLZAO).Compared to the conventional layered structure of cathodes and electrolytes in solid-state batteries, this integrated design establishes continuous lithium-ion transport channels, significantly improving interfacial contact between the electrolyte and cathode. Meanwhile, the incorporation of LLZAO nanofibers markedly enhances the electrochemical performance, mechanical strength, and thermal stability of the PEO polymer electrolyte.The ASSLIBs constructed with this cathode-supported CSE membrane demonstrated exceptional rate capability and cycling stability. This study proposes a scalable strategy for optimizing solid electrolyte membranes, providing critical support for ASSLIBs and related energy storage technologies.

Highlights & Results:

1.Nanofiber Preparation & Characterization: LLZAO nanofibers were fabricated via electrospinning followed by a one-step sintering process (Fig. 1). Scanning electron microscopy (SEM) images revealed that the obtained LLZAO fibers had a diameter of approximately 300 nm (Fig. 2b). Subsequently, a double-layer tape-casting method was employed to prepare the cathode-supported composite solid electrolyte (CSE) membrane (Fig. 2d). Experiments demonstrated that LiFePO₄ was uniformly distributed in the cathode layer, though some pores and cracks were observed on the surface (Fig. 2e). By directly casting the CSE slurry onto the cathode layer, the existing pores and cracks were effectively filled, resulting in a denser electrolyte structure (Fig. 2f).

Fig. 1: LLZAO nanofiber fabrication schematic.

Fig. 2: Schematic and SEM images of LLZAO nanofibers and CSE membranes.

2.Interfacial Properties: In the cathode-supported LFP-15 wt% LLZAONF/PPAL-CSE membrane, the electrolyte layer was tightly bonded to the cathode layer, with an almost indistinguishable interface (Fig. 3a). In contrast, the freestanding 15 wt% LLZAONF/PPAL-CSE membrane pressed against the cathode still exhibited noticeable gaps between the electrolyte and cathode (Fig. 3b). These gaps increase interfacial resistance and hinder Li⁺ transport. Additionally, the thickness of the freestanding CSE membrane was 104 μm, whereas the electrolyte layer in the cathode-supported CSE membrane was only 11.2 μm thick. The cathode-supported structure not only reduced interfacial resistance and facilitated Li⁺ transport but also significantly improved the battery's energy density.



Fig. 3: Cross-section comparisons of cathode-supported vs. freestanding CSE membranes.



3.Performance of Freestanding CSE Membranes: The freestanding 15 wt% LLZAONF/PPAL-CSE membrane exhibited excellent electrochemical performance, mechanical properties, and thermal stability. At 60°C, it achieved an ionic conductivity of 6.19 × 10⁻⁴ S·cm⁻¹, a Li⁺ transference number of 0.60, and an electrochemical stability window of 5.6 V (Fig. 4). Owing to its good mechanical strength (5.7 MPa), the membrane enabled stable cycling for up to 475 hours in a symmetric cell with a lithium metal anode without short-circuiting (Fig. 5). Moreover, the incorporation of LLZAO nanofibers effectively reduced the crystallinity of the PEO matrix, significantly enhancing the thermal stability of the
composite electrolyte




Fig. 4: Ionic conductivity tests.





Fig. 5: Mechanical/electrochemical/thermal tests of 15 wt% LLZAONF/PPAL-CSE.



4.Electrochemical Performance: The all-solid-state LFP//Li battery assembled with the cathode-supported LFP-15 wt% LLZAONF/PPAL-CSE membrane demonstrated outstanding rate capability and cycling performance. Throughout the rate performance tests, compared to the LFP-PPAL-PSE//Li battery, the LFP-15 wt% LLZAONF/PPAL-CSE//Li battery exhibited higher discharge specific capacity and lower polarization voltage (Fig. 6). After 115 cycles at 0.5C, it maintained a specific capacity of 143 mAh g⁻¹, with a capacity retention rate of 94.1% and an average Coulombic efficiency of 99%.




Fig. 6: Electrochemical performance of cathode-supported LFP//Li cells.

Paper Link: https://doi.org/10.1016/j.est.2025.116247