Insights into the Phase Purity and Storage Mechanism of Nonstoichiometric Na3.4Fe2.4(PO4)1.4P2O7 Cathode for High-Mass-Loading and High-Power-Density Sodium-Ion Batteries

Ziwei Fan, Wande Song, Nian Yang, Chenjie Lou, Ruiyuan Tian, Weibo Hua, Mingxue Tang, Fei Du

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

Mixed-anion-group Fe-based phosphate materials, such as Na4Fe3(PO4)2P2O7, have emerged as promising cathode materials for sodium-ion batteries (SIBs). However, the synthesis of pure-phase material has remained a challenge, and the phase evolution during sodium (de)intercalation is debating as well. Herein, a solid-solution strategy is proposed to partition Na4Fe3(PO4)2P2O7 into 2NaFePO4 ⋅ Na2FeP2O7 from the angle of molecular composition. Via regulating the starting ratio of NaFePO4 and Na2FeP2O7 during the synthesis process, the nonstoichiometric pure-phase material could be successfully synthesized within a narrow NaFePO4 content between 1.6 and 1.2. Furthermore, the proposed synthesis strategy demonstrates strong applicability that helps to address the impurity issue of Na4Co3(PO4)2P2O7 and nonstoichiometric Na3.4Co2.4(PO4)1.4P2O7 are evidenced to be the pure phase. The model Na3.4Fe2.4(PO4)1.4P2O7 cathode (the content of NaFePO4 equals 1.4) demonstrates exceptional sodium storage performances, including ultrahigh rate capability under 100 C and ultralong cycle life over 14000 cycles. Furthermore, combined measurements of ex situ nuclear magnetic resonance, in situ synchrotron radiation diffraction and X-ray absorption spectroscopy clearly reveal a two-phase transition during Na+ extraction/insertion, which provides a new insight into the ionic storage process for such kind of mixed-anion-group Fe-based phosphate materials and pave the way for the development of high-power sodium-ion batteries.

Original languageEnglish
Article numbere202316957
JournalAngewandte Chemie - International Edition
Volume63
Issue number8
Early online date2 Jan 2024
DOIs
StatePublished - 19 Feb 2024
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2024 Wiley-VCH GmbH.

Funding

This work was supported by National Natural Science Foundation of China (Grant No. 12374222, 12274176 and 22108218), Science and Technology Development Project, Jilin Province (Grant No. 20220201118GX), and the Fundamental Research Funds for the Center Universities.

FundersFunder number
Science and Technology Development Project
National Natural Science Foundation of China12274176, 12374222, 22108218
People's Government of Jilin Province20220201118GX
Fundamental Research Funds for the Central Universities

    Keywords

    • Ion-Storage Mechanism
    • Mixed Phosphate Cathodes
    • NaFe(PO)PO
    • Pure Phase
    • Sodium-Ion Batteries

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