Cu/Ti co-doping boosting P2-type Fe/Mn-based layered oxide cathodes for high-performance sodium storage

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• P2-type layered iron manganese oxides are promising cathode materials for sodium-ion batteries (SIBs).
• Their application is limited by phase transitions, metal dissolution, and poor air stability.
• Existing solutions involve single-cation doping or expensive lithium co-doping.

Purpose of the Study:

• To develop a cost-effective and stable cathode material for SIBs.
• To investigate the effects of low-cost Cu/Ti co-doping on P2-Na$_{0.7}$Cu$_{0.2}$Fe$_{0.2}$Mn$_{0.5Ti$_{0.1}$O$_{2}$.
• To enhance the air and electrochemical stability of SIB cathode materials.

Main Methods:

• Synthesis of Cu/Ti co-doped P2-Na$_{0.7}$Cu$_{0.2}$Fe$_{0.2}$Mn$_{0.5Ti$_{0.1}$O$_{2}$ cathode material.
• Electrochemical performance testing including rate capability and cycling stability.
• Structural and chemical characterization using in-situ X-ray diffraction (XRD), inductively coupled plasma optical emission spectrometry (ICP-OES), and X-ray photoelectron spectroscopy (XPS).

Main Results:

• The Cu/Ti co-doped material exhibits an initial capacity of 130 mAh g^-1 at 0.1C and 61.0 mAh g^-1 at 5C.
• It shows excellent capacity retention (>71.1% after 300 cycles) and remarkable air/water stability.
• Co-doping effectively mitigates P2-Z transitions, suppresses P2-P'2 phase transitions, reduces volume variation, and lowers transition metal dissolution.

Conclusions:

• Low-cost Cu/Ti co-doping is a viable strategy to enhance the performance of P2-type layered oxides for SIBs.
• This approach addresses key challenges including phase transitions and material degradation.
• The developed material demonstrates potential for practical, high-performance, and environmentally friendly sodium-ion batteries.