Cathode Active Material, Method for Manufacturing the Same, and Sodium-Ion Secondary Battery Comprising the Same

CoHCF Cathode Active Material with Enhanced Rate Capability via Lattice Constant Reduction through Zinc Ion Doping

This technology is a cathode active material that enhances rate capability and cycle stability by intentionally distorting the lattice of cobalt hexacyanoferrate (CoHCF) through zinc ion doping (Co1-xZnxHCF), creating pathways that facilitate easier ion transport.

While conventional CoHCF cathode materials offer high specific capacity, they have faced technical limitations due to relatively lower rate capabilities compared to nickel or copper-based Prussian blue analogues.

This technology synthesizes Co1-xZnxHCF (x=0.03~0.09) using iron, cobalt, and zinc precursors while controlling the Co:Zn molar ratio within the range of 97:3 to 91:9. Zinc doping reduces the lattice constant and forms mesopores within the particles, optimizing ion diffusion pathways. Applicable to aqueous electrolyte-based sodium-ion secondary batteries and energy storage systems linked to renewable energy with frequent output fluctuations, it significantly reduces capacity loss during high-speed charge/discharge cycles with only a small amount of zinc additive.

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Key Features:

• Cathode active material represented by the composition Co1-xZnxHCF (x=0.03~0.09), featuring zinc ions incorporated into cobalt hexacyanoferrate
• Step of preparing a reaction solution by adding a second solution containing cobalt and zinc precursors to a first solution containing an iron precursor at a set rate
• Step of aging the reaction solution, in which the molar ratio of cobalt ions to zinc ions is maintained between 97:3 and 91:9, for up to 12 hours
• Sodium-ion secondary battery with an aqueous electrolyte positioned between a cathode containing the Zn-doped active material and an anode

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