States of thermochemically or electrochemically synthesized NaxPy compounds analyzed by solid state 23Na and 31P nuclear magnetic resonance with theoretical calculation

Ryohei Morita, Kazuma Gotoh, Mouad Dahbi, Kei Kubota, Shinichi Komaba, Kazuyasu Tokiwa, Saeid Arabnejad, Koichi Yamashita, Kenzo Deguchi, Shinobu Ohki, Tadashi Shimizu, Robert Laskowski, Hiroyuki Ishida

Research output: Contribution to journalArticle

Abstract

Phosphorus is a promising material for the electrode in sodium ion batteries (NIBs). In this study, the states of NaxPy compounds synthesized by thermochemical reaction and electrochemical sodiation were compared using solid state 23Na magic angle spinning (MAS) NMR, 23Na multiple quantum (MQ) MAS NMR, and 31P MAS NMR. The NMR signals in thermochemically synthesized NaxPy compounds (Na3P, NaP, Na3P7, Na3P11, NaP7) are assigned in reference to theoretical chemical shifts, based on first-principles calculations. Furthermore, the NMR signals in electrochemically prepared NaxPy compounds after two sodiation/desodiation cycles are ascribed to Na3P compounds and three amorphous compositions. The amorphous compounds ascribed to Na1−αP (0 < α < 1), Na2−βP (0 < β < 1), and Na3−γP (0 < γ < 1) are formed below 0.58 V in the charge and discharge process. These Na3P and the amorphous phases overlapped in the range from 0.20 V (sodiation process) to 0.58 V (desodiation process). 23Na and 31P NMR spectra reveal reversible sodiation and desodiation processes in the third cycle.

Original languageEnglish
Pages (from-to)418-424
Number of pages7
JournalJournal of Power Sources
DOIs
Publication statusPublished - Feb 15 2019

Keywords

  • Negative electrode
  • Phosphorus
  • Sodium ion battery
  • Sodium phosphide
  • Solid state NMR

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • Energy Engineering and Power Technology
  • Physical and Theoretical Chemistry
  • Electrical and Electronic Engineering

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