6. DOPING STRATEGIES TO ENHANCE THE NA+ CONDUCTIVITY OF THE CUBIC NA3PS4 SUPERIONIC CONDUCTOR
Research Institute Affiliation: Agile - Sustainable Power and Energy Center (SPEC)
Faculty Advisor(s): Shyue Ping Ong
Name: Zhuoying Zhu
Grad Year: 2019
Cubic Na3PS4 (c-Na3PS4) is a highly promising sodium superionic conductor that may enable safer and more energy dense all-solid-state sodium batteries. First reported by Hayashi et al.,1 Na+ conductivities as high as 0.74 mS/cm have been achieved through improvements in synthesis and the addition of suitable dopants.2 In this work, we report first-principles based doping strategies to further enhance the Na+ conductivity of c-Na3PS4. We show that pristine c-Na3PS4 is an extremely poor Na ionic conductor.3 Using ab initio molecular dynamics simulations (AIMD), we confirm that the introduction of Na+ excess is the key to achieving reasonable Na+ conductivities observed in experiments, and our predicted conductivity of 6.25% Si-doped c-Na3PS4 (1.66 mS/cm) is in excellent agreement with reported experimental results. Remarkably, we find that 6.25% Sn doping yields a much higher predicted Na+ conductivity of 10.7 mS/cm, though with a slightly higher dopant formation energy. We also studied the effect of anion doping Na conductivity in this material using both first principles calculations and experiments. These results pave the way to further optimization of this highly promising superionic conductor. References:  Hayashi, A.; Noi, K.; Sakuda, A.; Tatsumisago, M., Nat. Commun, (2012), 3, 856.  Tanibata, N.; Noi, K.; Hayashi, A.; Tatsumisago, M., RSC Adv., (2014), 4, 17120.  Zhu, Z.; Chu, I.-H.; Deng, Z.; Ong, S. P., Chem Mater., (2015), 27, 8318.
Industry Application Area(s)
Energy/Clean technology | Materials