Ultra-stable, high-rate solid-state sodium batteries with bulk-interface engineering of NaCrO₂ cathode

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Solid-state sodium batteries (SSBs) offer high energy density and safety but face challenges in cycling stability and rate capability.
• O3-type layered oxides like NaCrO2 (NCO) are promising cathode materials for sodium-ion batteries.

Purpose of the Study:

• To improve the electrochemical performance of O3-type NaCrO2 for advanced SSBs.
• To investigate the synergistic effects of bulk doping and surface modification on NCO performance.

Main Methods:

• Synergistic modification of NaCrO2 via Li+ bulk doping and uniform carbon surface coating.
• Electrochemical characterization including cycling stability and rate capability tests.
• Assembly and testing of NCO-based solid-state sodium batteries with a Mg-doped Na-Landauer-type solid electrolyte (Mg-NZSP).

Main Results:

• Li+ doping significantly enhanced sodium ion diffusion and structural reversibility.
• Carbon coating effectively suppressed side reactions and reduced electrode volume change.
• The modified NCO material (NCO-1.5L@8%P) demonstrated excellent cycle stability (80.8% retention after 1600 cycles) and rate performance (113.5 mAh g-1 at 10C).
• SSBs assembled with the modified NCO achieved stable cycling (95.5% retention after 200 cycles at 2C) and high capacities at elevated rates (102.7 mAh g-1 at 5C, 96.1 mAh g-1 at 10C).

Conclusions:

• Synergistic modification of bulk and surface properties is an effective strategy to overcome limitations in O3-type NCO cathodes for SSBs.
• The enhanced electrochemical kinetics and interfacial stability contribute to superior performance in both organic electrolyte and solid-state configurations.
• This work provides insights into the regulation mechanisms for improving energy storage devices.