Solid-state rigid polymer composite electrolytes with in-situ formed nano-crystalline lithium ion pathways for lithium-metal batteries

Abstract

Polymer-based solid-state electrolytes with excellent processability and flexibility are ideal candidates for commercialisation in lithium-metal batteries. However, the current polymer-based solid-state electrolytes still have many problems such as low ionic conductivity, limited Li⁺ transport number and high interfacial resistance with electrodes. To address the above challenges, a solid-state rigid polymer composite electrolyte with high ionic conductivity (2.8 mS cm⁻¹) has been prepared based on the rigid polymer poly(2, 2′-disulfonyl-4, 4′-benzidine terephthalamide) (PBDT). Locally aligned PBDT-EMImN(CN)₂ grains are interspersed with in-situ formed interconnected LiFSI to form the structure of the polymer composite electrolyte. The formation of defective LiFSI nanocrystals at grain boundaries inside the polymer electrolyte acts as additional conductive networks providing fast Li⁺ transportation (t_Li⁺ = 0.59). The flexible region in the electrolyte gives excellent interfacial impedance (32.5 Ω cm²) with Li-metal electrode. The Li||Li batteries can be stably cycled for over 1000 cycles at 1 mA cm⁻² (25 °C). The assembled Li||LiFePO₄ batteries exhibit excellent cycling and multiplication performance over a wide operating temperature (from −20 to 60 °C). Moreover, this electrolyte material exhibits compatibility with high-voltage cathode LiNi_0.6Mn_0.2Co_0.2O₂ batteries. This electrolyte and design strategy is expected to inspire the realization of all-weather practical solid-state lithium-metal batteries.