High-Entropy Layered Oxide Cathode Enabling High-Rate for Solid-State Sodium-Ion Batteries.

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• O3-type layered oxides are promising cathodes for sodium-ion batteries due to high energy density and low cost.
• Challenges include phase transitions, sluggish kinetics, and air instability, hindering solid-state battery performance.

Purpose of the Study:

• To develop a high-performance cathode material for solid-state sodium-ion batteries.
• To improve the rate capability, air stability, and electrochemical-thermal stability of O3-type layered oxides.

Main Methods:

• Employing a high-entropy design and lithium (Li) doping strategy on Na_0.95Li_0.06Ni_0.25Cu_0.05Fe_0.15Mn_0.49O₂.
• Investigating the material's electrochemical performance, including capacity, rate capability, and cycling stability.
• Assessing air stability and thermal stability.

Main Results:

• The modified cathode exhibits a high reversible capacity of 141 mAh g^-1 at 0.2C and excellent rate capability (111 mAh g^-1 at 8C, 85 mAh g^-1 at 20C).
• Achieved long-term stability with over 85% capacity retention after 1000 cycles, attributed to a suppressed phase transition.
• Demonstrated air stability for seven days and thermal stability up to 279 °C.
• A polymer solid-state sodium battery using this cathode delivered 92 mAh g^-1 at 5C with 96% retention after 400 cycles.

Conclusions:

• The high-entropy design and Li doping effectively enhance the performance of O3-type layered oxide cathodes.
• This strategy significantly improves air stability, rate capability, and electrochemical-thermal stability for sodium-ion batteries.
• The developed material shows great potential for high-performance solid-state sodium-ion batteries.