Tailored Organic Electrode Material Compatible with Sulfide Electrolyte for Stable All-Solid-State Sodium Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• All-solid-state sodium batteries (ASSSBs) offer a safer and more cost-effective alternative to lithium-ion batteries due to nonflammable electrolytes and abundant sodium.
• A key challenge in ASSSBs is the chemical and electrochemical incompatibility between sulfide electrolytes and high-voltage sodium-ion cathodes, leading to interfacial instability and poor performance.

Purpose of the Study:

• To introduce a novel organic cathode material, Na4C6O6, designed for enhanced compatibility with superionic sulfide electrolytes in ASSSBs.
• To evaluate the electrochemical performance and interfacial stability of the Na4C6O6 cathode in ASSSBs.

Main Methods:

• Synthesis and characterization of the organic cathode material Na4C6O6.
• Fabrication and electrochemical testing of bulk-type ASSSBs utilizing Na4C6O6 as the cathode.
• Cycling stability tests were performed at various current densities (0.1 C and 0.2 C) over extended cycles (100 and 400).

Main Results:

• The Na4C6O6 cathode demonstrated high specific capacity (184 mAh g-1) and specific energy (395 Wh kg-1), among the highest for intercalation compound-based ASSSBs.
• Exceptional cycling stability was achieved, with 76% capacity retention after 100 cycles at 0.1 C and 70% after 400 cycles at 0.2 C, setting new records for ASSSBs.
• Na4C6O6 also exhibited potential as an anode material, enabling the construction of a symmetric all-organic ASSSB.

Conclusions:

• Na4C6O6 is a promising organic cathode material that overcomes the interfacial challenges associated with sulfide electrolytes in ASSSBs.
• The developed ASSSBs exhibit high energy density and unprecedented long-term cycling stability.
• The dual functionality of Na4C6O6 as both cathode and anode opens avenues for developing fully organic ASSSBs.