Non-flammable electrolytes could intrinsically eliminate fire hazards and improve battery safety, but their compatibility with electrode materials, especially graphite anodes, remains an obstacle owing to the strong catalytic activity of the anode surfaces. Here, we report an approach that improves the stability of non-flammable phosphate electrolytes by adjusting the molar ratio of Li salt to solvent. At a high Li salt-to-solvent molar ratio (~1:2), the phosphate solvent molecules are mostly coordinated with the Li+ cations, and the undesired reactivity of the solvent molecules toward the graphite anode can be effectively suppressed. High cycling Coulombic efficiency (99.7%), good cycle life and safe operation of commercial 18650 Li-ion cells with these electrolytes are demonstrated. In addition, these non-flammable electrolytes show reduced reactivity toward Li-metal electrodes. Non-dendritic Li-metal plating and stripping in Li–Cu half-cells are demonstrated with high Coulombic efficiency (>99%) and good stability.

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The main idea of the paper was jointly developed by Wuhan University and Pacific Northwest National Laboratory (PNNL), with support from the US Department of Energy, Office of Science, Basic Energy Sciences, Division of Materials Sciences and Engineering, under award KC020105-FWP12152 and by the National Key Research Program of China (no. 2016YFB0100200) and the National Nature Science Foundation of China (nos. 21673165 and 21333007). The NMR testing was supported by the US Department of Energy, Office of Science, Basic Energy Sciences, Division of Materials Sciences and Engineering, under award KC020105-FWP12152. Simulations were performed using PNNL Institutional Computing Resources. PNNL is operated by Battelle for the US Department of Energy under contract no. DE-AC05-76RL01830. The electrochemical study was supported by Wuhan University, and supported by the National Key Research Program of China (no. 2016YFB0100200) and the National Nature Science Foundation of China (nos. 21673165 and 21333007). The preparation of 18650 cells was supported by EVE Energy Co. Ltd. The safety tests were supported by the staff of the Battery Safety Laboratory of BST Power (Shenzhen) Limited.

Author information


  1. College of Chemistry and Molecular Sciences, Hubei Key Laboratory of Electrochemical Power Sources, Wuhan University, Wuhan, China

    • Ziqi Zeng
    • , Xiaoyu Jiang
    • , Yuliang Cao
    • , Xinping Ai
    •  & Hanxi Yang
  2. Pacific Northwest National Laboratory, Richland, WA, USA

    • Vijayakumar Murugesan
    • , Kee Sung Han
    • , Ji-Guang Zhang
    • , Maria L. Sushko
    •  & Jun Liu
  3. State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, China

    • Lifen Xiao


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J.L., L.X. and Y.C. conceived the idea of the high-molar-ratio non-flammable electrolyte. Z.Z. and X.J. synthesized a series of non-flammable electrolytes and carried out the electrochemical measurements of the electrode materials and 18650 cells. K.S.H. and L.X. conducted NMR measurements. V.M. conducted DFT calculations. Z.Z., L.X., Y.C. and J.L. participated in the manuscript writing. X.A., H.Y., J.-G.Z. and M.L.S. provided advice and helped in editing the manuscript. All authors participated in the analysis of the experimental data, the discussions of the results and the preparation of the paper.

Competing interests

The authors declare no competing interests.

Corresponding authors

Correspondence to Yuliang Cao or Lifen Xiao or Jun Liu.

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