Energy Storage Science and Technology ›› 2020, Vol. 9 ›› Issue (5): 1251-1265.doi: 10.19799/j.cnki.2095-4239.2020.0102

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Recent progress of sodium-based inorganic solid electrolytes

Ge SUN(), Zhixuan WEI, Xinyuan ZHANG, Nan CHEN(), Gang CHEN, Fei DU()   

  1. Key Laboratory of Physics and Technology for Advanced Batteries,Ministry of Education, College of Physics, Jilin University, Changchun 130012, Jilin, China
  • Received:2020-03-10 Revised:2020-03-31 Online:2020-09-05 Published:2020-09-08
  • Contact: Nan CHEN,Fei DU E-mail:sunge18@mails.jlu.edu.cn;nanchen@jlu.edu.cn;dufei@jlu.edu.cn

Abstract:

Sodium-ion batteries have become a promising alternative energy storage device to lithium-ion batteries due to the abundance and low cost of sodium resources, especially for grid-scale energy storage systems. However, just like their lithium-ion batteries counterpart, sodium-ion batteries use a flammable liquid electrolyte as their ionic transportation medium, which inevitably leads to safety concerns. In this regard, solid electrolytes (SEs) can fundamentally resolve this issue due to their incombustibility. Besides, SEs can be paired with the metal anode directly, enhancing the energy density of the battery system. Compared to other types of SEs, inorganic SEs have attracted increasing attention owing to their high ionic conductivity, high ion transfer number, high mechanical properties, and excellent stability. However, in the practical application of all-solid-state sodium batteries, several inorganic SEs still face different difficulties such as low ionic conductivity and poor chemical/electrochemical stability. Therefore, the research and development of inorganic SEs is an important topic to realize the application of solid-state sodium batteries. In this paper, we introduce ion-migration mechanisms in solid materials and review the development of several of the most studied inorganic SEs: oxide, sulfide, and complex hydride electrolytes. Studies on solutions to enhance their ionic conductivity and chemical/electrochemical stability are discussed in detail, including the following aspects: enhancing ionic conductivity via ion doping; reducing the grain boundary resistance of NASICON-type SEs by controlling the chemical composition at the grain boundary or using a low-melting-point additive; solving the problem of the air sensitivity of sulfide-type SEs; developing new sulfide superionic conductors; and reducing the order-disorder phase transition temperature of complex hydride SEs and simultaneously increasing the ionic conductivity at room temperature. Finally, the key challenges and future developmental trends of SEs are summarized and discussed.

Key words: sodium-ion conductor, inorganic solid electrolyte, ionic conductivity, chemical/electrochemical stability

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