An Adaptive High-Entropy Superstructure Cathode: Concurrently Tackling Phase Transition, Oxygen Redox, and Ambient...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Two-dimensional layered transition metal oxides (K_xTMO₂) offer good ion diffusion but suffer from poor structural stability and air sensitivity.
• Jahn-Teller distortion and layer gliding lead to phase transitions and degradation in K-ion battery cathodes.

Purpose of the Study:

• To develop a stable and high-performance cathode material for potassium-ion batteries.
• To overcome the limitations of traditional layered oxides through high-entropy design and doping.

Main Methods:

• Synthesis of an entropy-tailored dual-site Li-doped high-entropy superstructure oxide (K_0.67Mn_0.47Li_0.06Co_0.125Ni_0.125Fe_0.125Cu_0.125O₂).
• Investigation of structural stability using high-entropy, superlattice stabilization, and interlayer pinning effects.
• Analysis of charge compensation mechanisms and air stability enhancement through in situ spinel-like layer formation.

Main Results:

• Suppression of phase transitions and enablement of a single-phase solid-solution K-ion storage mechanism.
• Enhanced cationic-anionic charge compensation via elevated O 2p orbital energy and multi-TM hybridization.
• Improved ambient resistance due to a passivated spinel-like layer reducing CO₂ chemisorption and acid-driven degradation.
• Demonstrated high energy density, rate capability, and cyclic stability in half-cell and solid-state full-batteries.

Conclusions:

• The proposed high-entropy cathode material significantly enhances the stability and performance of potassium-ion batteries.
• Entropy engineering and dual-site doping are effective strategies for designing advanced layered oxide cathodes.
• This research provides a pathway for developing practical and durable energy storage solutions.