Advanced High-Entropy Halide Solid Electrolytes Enabling High-Voltage, Long-Cycling All-Solid-State Batteries.

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Stable solid electrolytes are crucial for enhancing the safety and energy density of lithium batteries, particularly for high-voltage applications.
• Current solid electrolytes face challenges in balancing ionic conductivity with high-voltage stability.

Purpose of the Study:

• To design and synthesize an innovative high-entropy chloride solid electrolyte (HE-5) for improved lithium battery performance.
• To investigate the relationship between high-entropy engineering, ionic conductivity, and electrochemical stability in solid electrolytes.
• To evaluate the performance of HE-5 in all-solid-state batteries (ASSBs) with high-voltage cathodes.

Main Methods:

• Multielement doping was employed to create a high-entropy chloride solid electrolyte (HE-5) with the composition Li₂.₂In₀.₂Sc₀.₂Zr₀.₂Hf₀.₂Ta₀.₂Cl₆.
• The ionic conductivity and activation energy of HE-5 were measured.
• All-solid-state batteries (ASSBs) utilizing HE-5, NCM83 cathodes, and a Li-In anode were assembled and electrochemically tested.
• Electrochemical performance, including capacity retention and cycling stability at high voltage, was evaluated.

Main Results:

• The synthesized HE-5 exhibited a disordered lattice structure, facilitating lithium-ion mobility.
• An ionic conductivity of 4.69 mS cm⁻¹ at 30 °C and an activation energy of 0.300 eV were achieved.
• ASSBs with HE-5 demonstrated excellent electrochemical performance, retaining 70% capacity over 1600 cycles at a 4 C rate.
• Stable operation at 5.0 V was achieved due to the high configurational entropy stabilizing the electrolyte structure.

Conclusions:

• High-entropy engineering effectively enhances both ionic conductivity and high-voltage stability in chloride solid electrolytes.
• HE-5 presents a promising material for next-generation energy-dense and safe all-solid-state lithium batteries.
• This research provides a valuable roadmap for developing advanced solid electrolytes through compositional complexity.