LiNO3-Assisted Succinonitrile-Based Solid-State Electrolyte for Long Cycle Life toward a Li-Metal Anode via an In Situ Thermal Polymerization Method

Succinonitrile (SN)-based electrolytes have a great potential for the practical application of all-solid-state lithium-metal batteries (ASSLMBs) due to their high room-temperature ionic conductivity, broad electrochemical window, and favorable thermal stability. Nevertheless, the poor mechanical strength and low stability toward Li metal hinder the further application of SN-based electrolytes to ASSLMBs. In this work, the LiNO3-assisted SN-based electrolytes are synthesized via an in situ thermal polymerization method. With this method, the mechanical problem is negligible, and the stability of the electrolyte enhances tremendously toward Li metal due to the addition of LiNO3. The LiNO3-assisted electrolytes exhibit a high ionic conductivity of 1.4 mS cm-1 at 25 °C, a wide electrochemical window (0-4.5 V vs Li+/Li), and excellent interfacial compatibility with Li (stable for over 2000 h at a current density of 0.1 mA cm-1). The LiFePO4/Li cells with the LiNO3-assisted electrolytes present significantly enhanced rate capability and cycling performance compared to the control group. NCM622/Li batteries also exhibit good cycling and rate performances with a voltage range of 3.0 to 4.4 V. Furthermore, ex situ SEM and XPS are employed. A compact interface is observed on Li anode after cycling, and the polymerization of SN is found to be suppressed. This paper will promote the development of practical application of SN-based ASSLMBs.