A lithium-poor tantalum oxychloride solid electrolyte for all-solid-state lithium batteries

Abstract

Solid-state electrolytes (SSEs) are the core components for achieving high-performance all-solid-state lithium batteries (ASSLBs), which require high ionic conductivity and good physical contact with the positive electrode. Herein, we report a lithium-poor tantalum oxychloride solid electrolyte (0.5Li₂O-TaCl₅), which still possesses an ultra-high ionic conductivity (8.54 × 10⁻³ S cm⁻¹) and good compatibility with LiCoO₂/LiNi_0.83Co_0.12Mn_0.05O₂ (LCO/NCM83) cathodes. The ASSLBs (LCO cathode) with this amorphous electrolyte not only exhibit a high discharge capacity of 155mAh g⁻¹ at 0.1C, but also demonstrate excellent rate performance (90mAh g⁻¹, 5C). It should be emphasized that due to the extremely high compaction density (3.28 g cm⁻³) of 0.5Li₂O-TaCl₅, it can maintain stable contact and low interface impedance with the positive electrode interface, thus exhibiting superior cycling stability in the ASSLBs. Furthermore, the capacity retention rate is as high as 97.14 % even after 3000 cycles at 3C. This work inspires the composition design for oxyhalide solid electrolytes containing low Li but delivering high Li⁺ conductivity.