Interplay between Cation and Anion Redox in Ni-Based Disordered Rocksalt Cathodes.

Area of Science:

• Electrochemistry
• Materials Science
• Solid-State Chemistry

Background:

• Lithium-excess cation-disordered rocksalt (DRX) cathodes are promising for energy storage.
• The electrochemical performance of DRX cathodes is critically dependent on the reversibility of redox processes.
• Understanding charge compensation mechanisms is essential for optimizing DRX cathode performance.

Purpose of the Study:

• To comprehensively analyze redox reactions in a representative Ni-based DRX cathode.
• To elucidate the roles of multiple cations and anions in the charge compensation mechanism.
• To identify strategies for improving the energy efficiency and reducing voltage hysteresis in Ni-based DRX cathodes.

Main Methods:

• Comprehensive analysis of redox reactions.
• Investigation of cation and anion roles in charge compensation.
• Study of molybdenum (Mo) migration effects on oxygen reduction potential.

Main Results:

• The low-voltage reduction reaction contributes to poor energy efficiency and significant voltage hysteresis.
• Molybdenum (Mo) migration between octahedral and tetrahedral sites was observed to enhance the oxygen reduction potential.
• The study highlights the critical role of high-valence transition metals in the redox chemistry of DRX cathodes.

Conclusions:

• Mo migration presents a viable strategy to enhance the energy efficiency of Ni-based DRX cathodes.
• Addressing challenges in Ni-based DRX systems requires a deep understanding of redox chemistry and transition metal roles.
• This research provides crucial insights for the future development of advanced DRX cathode materials.