Mechanically sinterable sulfide Na+ superionic conductors are key to enabling room-temperature-operable all-solid-state Na-ion batteries (ASNBs) for large-scale energy storage applications. To date, few candidates can fulfill the requirement of a high ionic conductivity of ≥1 mS cm-1 using abundant, cost-effective, and nontoxic elements. Herein, the development of a new Na+ superionic conductor, Ca-doped cubic Na3PS4, showing a maximum conductivity of ∼1 mS cm-1 at 25 °C is described. Complementary analyses using conductivity measurement by the AC impedance method, 23Na nuclear magnetic resonance spectroscopy, and density functional theory calculations reveal that the aliovalent substitution of Na+ in Na3PS4 with Ca2+ renders a cubic phase with Na vacancies, which increases the activation barriers but drastically enhances Na-ion diffusion. It is demonstrated that TiS2/Na-Sn ASNBs employing Ca-doped Na3PS4 exhibit a high charge capacity of 200 mA h g-1 at 0.06C, good cycling performance, and higher rate capability than those employing undoped cubic Na3PS4.
Bibliographical noteFunding Information:
Y.S.J. was supported by the Technology Development Program to Solve Climate Changes and by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning (Nos. NRF-2017M1A2A2044501 and NRF-2018R1A2B6004996), and by KOREA HYDRO & NUCLEAR POWER CO., LTD (No. 2017-Tech-17). H.J.L. and J.H.L. were supported by Creative Materials Discovery Program through NRF (No. 2017M3D1A1040828).
© Copyright 2018 American Chemical Society.
All Science Journal Classification (ASJC) codes
- Chemistry (miscellaneous)
- Renewable Energy, Sustainability and the Environment
- Fuel Technology
- Energy Engineering and Power Technology
- Materials Chemistry