Energy Storage Science and Technology ›› 2022, Vol. 11 ›› Issue (4): 1093-1102.doi: 10.19799/j.cnki.2095-4239.2021.0496

• Special issue of International Outstanding Young Scientists for Energy Storage • Previous Articles     Next Articles

Layered oxide cathode materials based on molecular orbital hybridization for high voltage sodium-ion batteries

Haiyan HU1(), Shulei CHOU1, Yao XIAO1,2()   

  1. 1.Technology Innovation Institute for Carbon Neutralization, College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325035, Zhejiang, China
    2.School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore
  • Received:2021-09-23 Revised:2021-09-29 Online:2022-04-05 Published:2022-04-11
  • Contact: Yao XIAO E-mail:huhaiyan@wzu.edu.cn;xiaoyao@wzu.edu.cn

Abstract:

O3-type sodium-layered transition-metal oxides, NaNi0.5Mn0.5O2, are one of the most promising cathode materials. However, the application of O3-NaNi0.5Mn0.5O2 cathode material is limited due to the transition metal layer's slip during charge and discharge processes, with multiple irreversible complex phase transitions. In addition, its energy density is limited due to the capacity of O3-NaNi0.5Mn0.5O2 electrode, which is mainly concentrated in the low-voltage region around 3 V, and O3-P3 phase transition easily occurred in this region. This study proposes a precise chemical element substitution strategy for successfully solving these problems Doping with Sn4+ inhibits the transition metal layer's slip and the irreversible multiphase transformation. Meanwhile, Sn4+ cannot be hybridized with the O 2p orbital due to the unique outer electronic structure, which lacks a single electron in its d orbital. The O 2p orbital only hybridized with the Ni eg orbital, increasing the ionic degree of Ni—O bond and Ni's redox potential. Therefore, O3-NaNi0.5Mn0.5O2 can display a high midpoint voltage of 3.28 V. Meanwhile, the electrode material exhibits excellent electrochemical performance and kinetic properties. The controllable redox potential of O3-type cathode material was realized based on molecular orbital hybridization theory to obtain the high-voltage layered oxide cathode materials sodium-ion batteries.

Key words: sodium-ion battery, layered cathode material, molecular orbital hybridization, high voltage, phase transformation mechanism

CLC Number: