High-Entropy Doping Enables Ultrahigh-Ni Co-Free Layered Cathodes with Enhanced Thermal Stability

Area of Science:

• Materials Science
• Electrochemistry
• Solid-state Chemistry

Background:

• Layered nickel-rich cathode materials offer high energy density but suffer from thermal decomposition due to phase transitions and strain during cycling.
• Conventional strategies to improve stability often compromise performance or introduce undesirable elements.

Purpose of the Study:

• To develop a novel high-entropy doping strategy for ultrahigh-nickel, cobalt-free layered cathode materials.
• To enhance the thermal and cycling stability of these advanced cathode materials, addressing safety concerns.

Main Methods:

• Synthesis of a compositionally complex (high-entropy) doped ultrahigh-Ni, Co-free layered cathode material.
• Investigation of the effects of high-entropy doping on Ni migration, phase transitions, and local atomic structure.
• Evaluation of thermal stability and cycling performance, including voltage decay.

Main Results:

• High-entropy doping significantly improved thermal and cycling stability, with negligible voltage decay.
• Doping suppressed irreversible phase transitions (layer-spinel-rocksalt) and mitigated strain propagation.
• Localized charge density around Ni atoms and improved Ni-O bond covalency were observed, leading to suppressed surface reconstruction.

Conclusions:

• High-entropy doping is an effective strategy to enhance the stability and safety of ultrahigh-Ni, Co-free layered cathode materials.
• This approach offers an innovative pathway to overcome thermal instability and safety concerns in next-generation batteries.