Enhancing cation storage performance of layered double hydroxides by increasing the interlayer distance

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Layered double hydroxides (LDH) are versatile materials used in supercapacitors.
• Their application in neutral electrolytes for metal-cation storage is limited by small interlayer distances, hindering large cation diffusion.
• Electrochemical activation can transform alkaline supercapacitor materials into cathodes for neutral electrolytes.

Purpose of the Study:

• To enhance the rate performance of NiCo-LDH for storing large cations in neutral electrolytes.
• To investigate the effect of increasing interlayer distance on cation storage.
• To develop high-performance supercapacitors using modified LDH materials.

Main Methods:

• Expanding the interlayer distance of NiCo-LDH by ion exchange, replacing nitrate ions with 1,4-benzenedicarboxylic anions (BDC).
• Characterizing the modified material (LDH-BDC) using electrochemical methods, including in situ electrochemical impedance spectra.
• Assembling and testing an asymmetric zinc-ion supercapacitor using LDH-BDC and activated carbon.

Main Results:

• The interlayer distance of NiCo-LDH was successfully expanded by incorporating BDC anions, creating LDH-BDC.
• LDH-BDC exhibited enhanced rate performance for storing large cations (Na+, Mg2+, Zn2+) compared to unmodified LDH.
• Performance for small Li+ ions remained largely unchanged, indicating selective enhancement.
• Reduced charge-transfer and Warburg resistances were observed in LDH-BDC due to increased interlayer spacing.
• The asymmetric zinc-ion supercapacitor demonstrated high energy density and cycling stability.

Conclusions:

• Increasing the interlayer distance of LDH is an effective strategy to improve large cation storage.
• BDC pillaring of NiCo-LDH significantly enhances its electrochemical performance in neutral electrolytes.
• The developed LDH-BDC material shows promise for high-performance energy storage devices like zinc-ion supercapacitors.