Article

Hydrate-melt electrolytes for high-energy-density aqueous batteries

  • Nature Energy 1, Article number: 16129 (2016)
  • doi:10.1038/nenergy.2016.129
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Abstract

Aqueous Li-ion batteries are attracting increasing attention because they are potentially low in cost, safe and environmentally friendly. However, their low energy density (<100 Wh kg−1 based on total electrode weight), which results from the narrow operating potential window of water and the limited selection of suitable negative electrodes, is problematic for their future widespread application. Here, we explore optimized eutectic systems of several organic Li salts and show that a room-temperature hydrate melt of Li salts can be used as a stable aqueous electrolyte in which all water molecules participate in Li+ hydration shells while retaining fluidity. This hydrate-melt electrolyte enables a reversible reaction at a commercial Li4Ti5O12 negative electrode with a low reaction potential (1.55 V versus Li+/Li) and a high capacity (175 mAh g−1). The resultant aqueous Li-ion batteries with high energy density (>130 Wh kg−1) and high voltage (2.3–3.1 V) represent significant progress towards performance comparable to that of commercial non-aqueous batteries (with energy densities of 150–400 Wh kg−1 and voltages of 2.4–3.8 V).

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References

  1. 1.

     & Issues and challenges facing rechargeable lithium batteries. Nature 414, 359–367 (2001).

  2. 2.

     & Building better batteries. Nature 451, 652–657 (2008).

  3. 3.

     & Challenges for rechargeable Li batteries. Chem. Mater. 22, 587–603 (2010).

  4. 4.

    Nonaqueous liquid electrolytes for lithium-based rechargeable batteries. Chem. Rev. 104, 4303–4417 (2004).

  5. 5.

    Electrolytes and interphases in Li-ion batteries and beyond. Chem. Rev. 114, 11503–11618 (2014).

  6. 6.

    ,  & Electrical energy storage for the grid: a battery of choices. Science 334, 928–935 (2011).

  7. 7.

    ,  & Safety mechanisms in lithium-ion batteries. J. Power Sources 155, 401–414 (2006).

  8. 8.

     & A general discussion of Li ion battery safety. Interface 21, 37–44 (2012).

  9. 9.

    et al. Thermal runaway caused fire and explosion of lithium ion battery. J. Power Sources 208, 210–224 (2012).

  10. 10.

    ,  & Rechargeable lithium batteries with aqueous electrolytes. Science 264, 1115–1118 (1994).

  11. 11.

    , ,  & Raising the cycling stability of aqueous lithium-ion batteries by eliminating oxygen in the electrolyte. Nat. Chem. 2, 760–765 (2010).

  12. 12.

    , ,  & A high-rate and long cycle life aqueous electrolyte battery for grid-scale energy storage. Nat. Commun. 3, 1149 (2012).

  13. 13.

    et al. Aqueous rechargeable Li and Na ion batteries. Chem. Rev. 114, 11788–11827 (2014).

  14. 14.

    et al. ‘Water-in-salt’ electrolyte enables high-voltage aqueous lithium-ion chemistries. Science 350, 938–943 (2015).

  15. 15.

    et al. Advanced high-voltage aqueous lithium-ion battery enabled by ‘water-in-bisalt’ electrolyte. Angew. Chem. Int. Ed. 55, 7136–7141 (2016).

  16. 16.

    A new class of molten salt mixtures. The hydrated dipositive ion as an independent cation species. J. Electrochem. Soc. 112, 1224–1227 (1965).

  17. 17.

     & Emulsion techniques for the study of glass formation. 2. Low melting point salt hydrates. J. Phys. Chem. 88, 4779–4781 (1984).

  18. 18.

    Vapor pressures of aqueous melts: LiNO3+KNO3 melts containing water or deuterium oxide. J. Chem. Thermodyn. 7, 263–269 (1975).

  19. 19.

     & Observations of water monomers in supersaturated NaClO4, LiClO4, and Mg(ClO4)2 droplets using Raman spectroscopy. J. Phys. Chem. A 107, 5956–5962 (2003).

  20. 20.

    Glyme-lithium salt phase behavior. J. Phys. Chem. B 110, 13177–13183 (2006).

  21. 21.

    Electronic structure calculations on lithium battery electrolyte salts. Phys. Chem. Chem. Phys. 9, 1493–1498 (2007).

  22. 22.

    et al. Phase-diagrams and conductivity behavior of poly(ethylene oxide) molten-salt rubbery electrolytes. Macromolecules 27, 7469–7477 (1994).

  23. 23.

    et al. Glyme-lithium bis(trifluoromethanesulfonyl)imide and glyme-lithium bis(perfluoroethanesulfonyl)imide phase behavior and solvate structures. Chem. Mater. 17, 2284–2289 (2005).

  24. 24.

    et al. LiTFSI stability in water and its possible use in aqueous lithium-ion batteries: pH dependency, electrochemical window and temperature stability. J. Electrochem. Soc. 160, A1694–A1700 (2013).

  25. 25.

     & International equations for the saturation properties of ordinary water substance. J. Phys. Chem. Ref. Data 16, 893–901 (1987).

  26. 26.

    Mobility and ionic association of lithium salts in a propylene carbonate-ethyl methyl carbonate mixed solvent. J. Electrochem. Soc. 142, 2577–2581 (1995).

  27. 27.

    ,  & Ionic liquids: ion mobilities, glass temperatures, and fragilities. J. Phys. Chem. B 107, 6170–6178 (2003).

  28. 28.

     & Fluidity and conductance in aqueous electrolyte solutions. An approach from the glassy state and high-concentration limit. I. Ca(NO3)2 solutions. J. Phys. Chem. 1086, 3244–3253 (1979).

  29. 29.

     & Contrasting conductance/viscosity relations in liquid states of vitreous and polymer solid electrolytes. J. Phys. Chem. 92, 2083–2086 (1988).

  30. 30.

    , ,  & Raman frequency and intensity studies of liquid H2O, H218O and D2O. J. Raman Spectrosc. 20, 683–694 (1989).

  31. 31.

    , ,  & Hydrogen bonding and Raman, IR, and 2D-IR spectroscopy of dilute HOD in liquid D2O. Proc. Natl Acad. Sci. USA 104, 14215–14220 (2007).

  32. 32.

     & IR and Raman spectra of liquid water: theory and interpretation. J. Chem. Phys. 128, 224511 (2008).

  33. 33.

    et al. Reference Raman spectra of synthesized CaCl2 nH2O solids (n = 0,2,4,6). J. Raman Spectrosc. 46, 822–828 (2015).

  34. 34.

     & Hybrid aqueous energy storage cells using activated carbon and lithium-intercalated compounds. J. Electrochem. Soc. 153, A1425–A1431 (2006).

  35. 35.

    et al. Interfacial lithium-ion transfer at the LiMn2O4 thin film electrode/aqueous solution interface. J. Power Sources 174, 695–700 (2007).

  36. 36.

    et al. Oxidative-stability enhancement and charge transport mechanism in glyme-lithium salt equimolar complexes. J. Am. Chem. Soc. 133, 13121–13129 (2011).

  37. 37.

    et al. Unusual stability of acetonitrile-based superconcentrated electrolytes for fast-charging lithium-ion batteries. J. Am. Chem. Soc. 136, 5039–5046 (2014).

  38. 38.

    , , ,  & Sacrificial anion reduction mechanism for electrochemical stability improvement in highly concentrated Li-salt electrolyte. J. Phys. Chem. C 118, 14091–14097 (2014).

  39. 39.

    , , ,  & Characterization of lithium electrode in lithium imides/ethylene carbonate and cyclic ether electrolytes. J. Electrochem. Soc. 151, A437 (2004).

  40. 40.

    et al. Twin problems of interfacial carbonate formation in nonaqueous Li–O2 batteries. J. Phys. Chem. Lett. 3, 997–1001 (2012).

  41. 41.

     & The vapor pressures of aqueous solutions of lithium nitrate and the activity coefficients of some alkali salts in solutions of high concentration at 25. J. Am. Chem. Soc. 54, 3544–3555 (1932).

  42. 42.

    A thermodynamic study of bivalent metal halides in aqueous solution. Part XVII-Revision of data for all 2:1 and 1:2 electrolytes at 25, and discussion of results. Trans. Faraday Soc. 44, 295–307 (1947).

  43. 43.

     & Ionic hydration and activity in electrolyte solutions. J. Am. Chem. Soc. 70, 1870–1878 (1948).

  44. 44.

    The influence of ionic hydration on activity coefficients in concentrated electrolyte solutions. Trans. Faraday Soc. 51, 1235–1244 (1955).

  45. 45.

    et al. Isolation of solid solution phases in size-controlled LixFePO4 at room temperature. Adv. Funct. Mater. 19, 395–403 (2009).

  46. 46.

     & Unified approach for molecular dynamics and density-functional theory. Phys. Rev. Lett. 55, 2471–2474 (1985).

  47. 47.

    CPMD (IBM Corp. 1990–2008, MPI für Festkörperforschung Stuttgart 1997–2001);

  48. 48.

    A unified formulation of the constant temperature molecular dynamics methods. J. Chem. Phys. 81, 511–519 (1984).

  49. 49.

    ,  & Separable dual-space Gaussian pseudopotentials. Phys. Rev. B 54, 1703–1710 (1996).

  50. 50.

    Pseudopotentials for H to Kr optimized for gradient-corrected exchange-correlation functionals. Theor. Chem. Acc. 114, 145–152 (2005).

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Acknowledgements

This work was supported by a JSPS Grant-in-Aid for Specially Promoted Research (No. 15H05701). The calculations in this work were performed on the K computer at the RIKEN AICS and on the Oakleaf-FX at the University of Tokyo with the support of the HPCI Systems Research Projects (Proposal Numbers hp150275 and hp150068) and on the supercomputers at NIMS, ISSP and ITC at the University of Tokyo and Kyushu University.

Author information

Affiliations

  1. Department of Chemical System Engineering, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan

    • Yuki Yamada
    • , Kenji Usui
    • , Seongjae Ko
    •  & Atsuo Yamada
  2. Elements Strategy Initiative for Catalysts & Batteries (ESICB), Kyoto University, 1-30, Goryo-Ohara, Nishikyo-ku, Kyoto 615-8245, Japan

    • Yuki Yamada
    • , Keitaro Sodeyama
    • , Yoshitaka Tateyama
    •  & Atsuo Yamada
  3. PRESTO, Japan Science and Technology Agency (JST), 4-1-8, Honcho, Kawaguchi, Saitama 333-0012, Japan

    • Keitaro Sodeyama
  4. Center for Green Research on Energy and Environmental Materials and Center for Materials Research by Information Integration, National Institute for Materials Science (NIMS), 1-1, Namiki, Tsukuba, Ibaraki 305-0044, Japan

    • Keitaro Sodeyama
    •  & Yoshitaka Tateyama

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Contributions

Y.Y. and A.Y. proposed the concept. Y.Y., K.U. and S.K. designed the experiments. K.U. developed the hydrate melt system and analysed the structures and basic physicochemical/electrochemical properties. S.K. designed the electrochemical cell and performed the cycling tests and the post-mortem electrode analyses. K.S. and Y.T. designed and performed the theoretical calculations. All authors contributed to the discussion. Y.Y. and A.Y. wrote the manuscript. A.Y. supervised the overall project.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Atsuo Yamada.

Supplementary information

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    Supplementary Information

    Supplementary Figures 1–13, Supplementary Table 1, Supplementary Notes 1–2, Supplementary References