Synergistic fluorine-nitrogen interfaces enabling stable high-voltage sulfide-based all-solid-state lithium metal batteries

Sulfide-based all-solid-state lithium metal battery (ASSLMB) is widely recognized as one of the promising next-generation energy storage devices, offering enhanced safety by using non-flammable solid electrolytes (SEs), and higher energy density by enabling the integration of high-voltage cathodes and lithium-metal anodes.

However, the practical deployment of sulfide ASSLMBs remains hampered by two persistent interfacial challenges: (1) electrochemical instability with high-voltage cathodes, where the large potential mismatch between sulfide SEs and oxide cathodes induces detrimental space charge layers (SCLs) and oxidative decomposition; (2) incompatibility of sulfide SEs with lithium-metal anode, where the strong reducibility of lithium triggers continuous SE degradation and lithium dendrite penetration. These issues collectively lead to rapid capacity fading, low critical current densities (CCD <1 mA/cm²), and poor cycling stability under extreme conditions (e.g., high voltages, high rates, and wide temperatures), hindering the commercialization of sulfide based ASSLMBs.

To address the above challenges, Professor Xie Jia's group from Huazhong University of Science and Technology has revealed a fluorine-nitrogen synergistic interface engineering strategy by modifying Li_5.5PS_4.5Cl_1.5 (LPSC) with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), thereby enhancing the stability of sulfide electrolytes at high-voltage cathodes and lithium metal anodes.

Firstly, the compatibility of different lithium salts (LiTFSI, LiFSI, and LiDFOB) with the LPSC electrolyte was compared through characterization methods such as XPS and XRD, and LiTFSI was selected as the modification medium. The modified LPSC electrolyte exhibits a high ionic conductivity of 2.88 mS/cm and improved air stability.

Additionally, LiTFSI induced dual-functional interphases, a fluorine-rich CEI (LiF/Li_xPO_yF_z) and a fluorine-nitrogen composite SEI (Li₃N/LiF/Li_xPO_yF_z), contributing to high oxidation stability (LiNi_0.8Co_0.1Mn_0.1O₂//LiIn battery retains 107% capacity retention after 13000 cycles at 15C) and excellent lithium dendrite inhibition ability (Li//Li: CCD 3.4 mA/cm², stably cycling 2600 h at 0.5 mA/cm²). As a result, the LiNi_0.8Co_0.1Mn_0.1O₂//Li cell with modified electrolyte demonstrates 1000 stable cycles at a high cut-off voltage of 4.5 V and wide-temperature adaptability (-20~50 ℃). This work shows a facile and effective method for constructing long-life high-energy-density sulfide based ASSLMBs.

The team published their work in Nano Research on July 21, 2025.

In this work, different lithium salts were screened from the aspects of ionic conductivity, lithium metal compatibility, and chemical compatibility with electrolyte. And the one that best matched LPSC was finally determined. In the follow-up work, the team will further study the mechanism of interaction between different lithium salts and sulfide electrolytes, and further develop high-performance lithium salt additives suitable for sulfide electrolytes.

About the Authors

Jia Xie received his BS degree from Peking University in 2002 and his PhD from Stanford University in 2008. He joined Huazhong University of Science and Technology (HUST) as a Full Professor in 2015. His current research interests focus on Power battery and the key materials, large-scale electrochemical energy storage technology for power grid and electric vehicle. Until now, he has published more than 200 papers, owns more than 100 invention patents. For more information, please pay attention to his research homepage http://rest.seee.hust.edu.cn.

About Nano Research

Nano Research is a peer-reviewed, open access, international and interdisciplinary research journal, sponsored by Tsinghua University and the Chinese Chemical Society, published by Tsinghua University Press on the platform SciOpen. It publishes original high-quality research and significant review articles on all aspects of nanoscience and nanotechnology, ranging from basic aspects of the science of nanoscale materials to practical applications of such materials. After 18 years of development, it has become one of the most influential academic journals in the nano field. Nano Research has published more than 1,000 papers every year from 2022, with its cumulative count surpassing 7,000 articles. In 2024 InCites Journal Citation Reports, its 2024 IF is 9.0 (8.7, 5 years), and it continues to be the Q1 area among the four subject classifications. Nano Research Award, established by Nano Research together with TUP and Springer Nature in 2013, and Nano Research Young Innovators (NR45) Awards, established by Nano Research in 2018, have become international academic awards with global influence.