Improving Na₂Ti₃O₇ Anode Performance in Sodium-Ion Batteries via a Al Doping

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Sodium titanate (Na2Ti3O7) is a promising anode material for sodium-ion batteries (SIBs) due to its low sodium insertion potential.
• However, its practical use is limited by poor electronic conductivity, slow ion kinetics, and interfacial instability, resulting in poor cycling and rate performance.

Purpose of the Study:

• To synthesize and characterize Al-doped Na2Ti3O7 (NTO-Al) as an improved anode material for SIBs.
• To investigate the effects of Al doping on the structural, electronic, and electrochemical properties of NTO.

Main Methods:

• One-step high-temperature solid-state synthesis of micron-sized rod-like NTO and NTO-Al samples.
• Electrochemical characterization including charge-discharge cycling and rate capability tests.
• Hydrogen temperature-programmed reduction (H2-TPR) to analyze the role of doping and oxygen vacancies.

Main Results:

• Al doping slightly reduced NTO microrod size but introduced oxygen vacancies and Ti3+, enhancing electronic conductivity.
• H2-TPR indicated that doping activates lattice oxygen, improving reaction kinetics.
• The optimized NTO-Al0.03 electrode showed a higher initial charge capacity (147.4 mAh g-1 at 0.5 C vs. 124.7 mAh g-1 for NTO).
• NTO-Al0.03 demonstrated superior cycling stability (49.5% retention after 100 cycles) and rate performance (36.3 mAh g-1 at 2 C).

Conclusions:

• Al doping is an effective strategy to overcome the limitations of Na2Ti3O7 as an anode material for SIBs.
• The enhanced electronic conductivity and ionic diffusion in NTO-Al contribute to improved electrochemical performance.
• Optimized Al-doped NTO shows significant potential for high-energy-density and stable sodium-ion batteries.