Reduced Graphene Oxide Stack, Manufacturing Method Thereof, and Sodium Secondary Battery Comprising the Same

Reduced Graphene Stacking Anode for Sodium Storage with Expanded Interlayer Spacing Using AlOOH Sacrificial Spacers

This technology involves inserting metal oxyhydroxide particles, such as AlOOH, between reduced graphene oxide (rGO) sheets to adjust the interlayer spacing before removing the particles. This creates a layered graphene stack that facilitates the insertion and extraction of sodium ions.

Because sodium ions are larger than lithium ions, they struggle to enter the narrow interlayer spacing of conventional graphite electrodes. Graphene electrodes also face limitations, as the sheets tend to aggregate, making it difficult to secure the interlayer space required for ion diffusion and electric double-layer formation.

This technology involves adding a trivalent metal salt, such as aluminum halide, to a graphene oxide dispersion, followed by sequential reduction and heat treatment to grow nano-sized metal oxyhydroxide particles between the graphene layers. The particles are then removed using an acidic solvent to obtain a stack with wide interlayer spacing, corresponding to an XRD 2θ peak of 10° or less. Applicable to sodium-ion battery anodes and sodium hybrid capacitor electrodes, it provides a reversible storage space for large ions using only carbon materials, which was difficult to achieve with graphite.

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Key Features:

• Adding a reducing agent to a dispersion containing a trivalent metal salt and graphene oxide sheets to form reduced graphene oxide sheets
• Heat-treating the dispersion to form metal oxyhydroxide particles with an average diameter of 0.5 Å to 16.0 Å between the reduced graphene oxide sheets
• Removing the metal oxyhydroxide particles located between the sheets after heat treatment to secure interlayer space
• A reduced graphene oxide stack where the interlayer spacing in the direction normal to the sheets appears as a peak at 2θ 10° or less in XRD analysis

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This invention was developed with support from the Ministry of Trade, Industry and Energy for the development of extended layered sodium-ion secondary battery anode materials with long-range regularity using large polyatomic ion functionalized graphene ink.

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