Entropy-Regulated Cathode with Low Strain and Constraint Phase-Change Toward Ultralong-Life Aqueous Al-Ion Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Reversible aluminum-ion (Al³⁺) storage is challenging due to intense electrostatic interactions and host material instability.
• Prussian Blue analogues (PBAs) exhibit poor robustness, leading to significant strain and phase changes during Al³⁺ insertion/extraction.

Purpose of the Study:

• To develop an entropy-driven strategy for high-performance, long-lifespan aqueous Al-ion batteries (AIBs).
• To overcome the limitations of traditional PBAs in reversible Al³⁺ storage.

Main Methods:

• Synthesis of medium entropy Prussian Blue analogues (ME-PBAs) with multiple redox-active centers.
• Characterization of ME-PBAs for structural stability, conductivity, and electrochemical Al³⁺ storage.
• Assembly and testing of full cells using ME-PBAs as cathodes and MoO₃ as anodes.

Main Results:

• ME-PBAs demonstrate enhanced conductivity and significantly improved structural robustness, with only 1.2% lattice parameter fluctuation.
• The ME-PBA host enables reversible Al³⁺ storage with an extended lifespan exceeding 10,000 cycles.
• Full cells assembled with ME-PBAs and MoO₃ exhibit outstanding electrochemical properties.

Conclusions:

• Entropy regulation in PBAs is a promising strategy to simultaneously constrain strain and phase transitions for long-term Al³⁺ storage.
• ME-PBAs offer a viable design for advanced electrode materials in aqueous multivalent ion batteries.