High Ionic Conductivity and Transfer Number of Composite Solid Electrolyte for Advanced Lithium Battery by Synergetic Effect of Halloysite Nanotube and High-entropy Zeolitic Imidazolate Frameworks

Abstract

Composite solid-state electrolytes (CSEs) with excellent flexibility and high safety hold great potential for high performance lithium batteries. However, its low room temperature ionic conductivity and transfer number have plagued its practical application. In this work, local Li diffusion was tailored by the synergetic effect of halloysite nanotubes (HNTs) and high-entropy ZIF in a polyvinylidene fluoride/LITFSI/Li_6.85La_2.95Yb_0.05Zr_1.85Ta_0.15O₁₂ matrix. The anchoring of TFSI⁻ anions by the rich open metal sites in HE-ZIF and the inner positively wall in HNT, combined with the continuous diffusion pathway of Li⁺ built by the negatively surface of HNT, distinctly enhances the ionic conductivity and transfer number of the electrolyte. A high ionic conductivity (1.06×10⁻³ S·cm⁻¹ at 30 °C) and high Li⁺ transference number (0.86) were achieved in PLLH-HE. The lithium symmetric battery (Li//PLLH-HE//Li) exhibited excellent interfacial compatibility and a high critical current density (CCD, 2.38 mA·cm⁻²). A lithium metal battery assembled with LiFePO₄ (LFP) cathodes exhibited a high discharge specific capacity of 141 mAh·g⁻¹ after 400 cycles at 0.5 C, while the cell assembled with LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) also delivered a high discharge specific capacity of 140.1 mAh·g⁻¹ at 1 C after 600 cycles. This work reveals the critical role of local Li diffusion and provides a general method for enhancing the electrochemical properties of CSEs for solid state batteries.