Medium-entropy-designed δ-MnO₂ cathode for high-performance aqueous zinc-ion battery

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Layered δ-MnO₂ cathodes offer high voltage and capacity for aqueous zinc-ion batteries (AZIBs).
• However, they suffer from poor conductivity and structural instability, limiting their practical application.
• Developing stable and conductive cathode materials is crucial for advancing AZIB technology.

Purpose of the Study:

• To design and synthesize a medium-entropy δ-MnO₂ cathode material with enhanced electronic/ionic conductivity and structural stability.
• To investigate the effects of Cr/V/Ti multi-principal elemental co-doping on the electrochemical performance of δ-MnO₂.
• To elucidate the Zn²⁺ insertion/extraction mechanism in the entropy-stabilized cathode.

Main Methods:

• Medium-entropy design strategy utilizing Cr/V/Ti multi-principal elemental co-doping.
• Synthesis of the entropy-stabilized δ-MnO₂ cathode material.
• Electrochemical characterization including cyclic voltammetry, galvanostatic charge-discharge, and rate capability tests.
• In-situ characterizations (e.g., in-situ XRD, in-situ DRT) and Density Functional Theory (DFT) calculations.

Main Results:

• The medium-entropy doping significantly improved bulk electronic spatial structures, enhancing reaction kinetics.
• The optimized cathode exhibited excellent structural stability and inhibited Mn dissolution.
• The material achieved a high working capacity of 298 mA h g⁻¹ at 1C, superior cyclic stability (91.5% after 100 cycles), and competitive rate capabilities (199 mA h g⁻¹ at 3C).

Conclusions:

• Medium-entropy design is an effective strategy to enhance the performance of δ-MnO₂ cathodes in AZIBs.
• The Cr/V/Ti co-doped δ-MnO₂ demonstrates significant potential for high-performance and practical AZIB applications.
• This work provides fundamental insights into the structure-activity relationship and ion insertion mechanism for advanced battery materials.