Chalcopyrite-Derived NaMO₂ (M = Cu, Fe, Mn) Cathode: Tuning Impurities for Self-Doping

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Developing earth-abundant cathode materials is crucial for large-scale sodium-ion batteries (SIBs).
• Traditional methods often face challenges with impurities in natural precursors.

Purpose of the Study:

• To explore the direct synthesis of layered NaMO2 cathodes from concentrated chalcopyrite ores.
• To investigate the role of impurity elements (Si, Ca) in tailoring the structure and performance of SIB cathodes.

Main Methods:

• Direct synthesis of layered NaMO2 (M = Cu, Fe, Mn) cathodes from concentrated chalcopyrite ores.
• Analysis of the impact of impurity elements (Si, Ca) on P2 and O3 phase formation.
• Electrochemical testing of synthesized cathode materials in half-cells.

Main Results:

• Impurity elements (Si, Ca) were found to be crucial for controlling P2/O3 phase structures, overcoming concerns about their negative effects.
• Ca self-doping in P2-type NaMO2 enhanced structural stability, showing 56 mAh g⁻¹ at 5 C and 90% retention after 100 cycles at 1 C.
• O3-type oxides with fewer impurities achieved a high capacity of 107 mAh g⁻¹ at 0.1 C and 84% retention after 200 cycles at 2 C.

Conclusions:

• A new strategy for preparing SIB electrode materials from natural ores by utilizing impurities was developed.
• This approach offers a feasible route for constructing cost-effective and durable sodium-ion batteries.