LiF and LiNO3 as synergistic additives for PEO-PVDF/LLZTO-based composite electrolyte towards high-voltage lithium batteries with dual-interfaces stability

作者：Li, Liansheng; Deng, Yuanfu^*; Duan, Huanhuan; Qian, Yunxian; Chen, Guohua

来源：Journal of Energy Chemistry, 2022, 65: 319-328.

DOI：10.1016/j.jechem.2021.05.055

• Synergistic additives
• Composite solid electrolyte
• Dual-interfaces stability
• High-voltage cathode
• Lithium metal battery

Solid electrolytes with desirable properties such as high ionic conductivity, wide electrochemical stable window, and suitable mechanical strength, and stable electrode-electrolyte interfaces on both cathode and anode side are essential for high-voltage all-solid-state lithium batteries (ASSLBs) to achieve excellent cycle stability. In this work, a novel strategy of using LiF and LiNO3 as synergistic additives to boost the performance of PEO-PVDF/LLZTO-based composite solid electrolytes (CSEs) is developed, which also promotes the assembled high-voltage ASSLBs with dual-interfaces stability characteristic. Specifically, LiF as an inactive additive can increase the electrochemical stability of the CSE under high cut-off voltage, and improve the high-voltage compatibility between cathode and CSE, thus leading to a stable cath-ode/CSE interface. LiNO3 as an active additive can lead to an enhanced ionic conductivity of CSE due to the increased free-mobile Li+ and ensure a stable CSE/Li interface by forming stable solid electrolyte inter-phase (SEI) on Li anode surface. Benefiting from the improved performance of CSE and stable dual-interfaces, the assembled NCM622/9[PEO15-LiTFSI]-PVDF-15LLZTO-2LiF-3LiNO(3)/Li cell delivers a high rate capacity of 102.1 mAh g(-1) at 1.0 C and a high capacity retention of 77.4% after 200 cycles at 0.5 C, which are much higher than those of the ASSLB assembled with additive-free CSE, with only 60.0 mAh g(-1) and 52.0%, respectively. Furthermore, novel cycle test modes of resting for 5 h at different charge states after every 5 cycles are designed to investigate the high-voltage compatibility between cathode and CSE, and the results suggest that LiF additive can actually improve the high-voltage compat-ibility of cathode and CSE. All the obtained results confirm that the strategy of using synergistic additives in CSE is an effective way to achieve high-voltage ASSLBs with dual-interfaces stability.