CoHCF Cathode Active Material and Manufacturing Method Thereof

CoHCF Cathode Material for Sodium-Ion Batteries Refined via High-Speed Direct Mixing and Low-Concentration Citrate Control

This technology refines particles and ensures crystal structure stability by reducing precursor mixing time or adjusting the concentration of citrate ions, a chelating agent, during the co-precipitation of cobalt hexacyanoferrate (CoHCF).

CoHCF synthesized using conventional methods resulted in large particle sizes, leading to lattice distortion and structural deformation during Na+ insertion and extraction during charge/discharge cycles. This caused issues with poor rate capability and reduced long-term cycle stability.

This technology inhibits particle growth and increases specific surface area by rapidly mixing precursor solutions within 20 seconds using direct mixing, or by lowering the citrate ion concentration to intentionally create iron vacancies, which mitigates crystal deformation during charge/discharge. It can be applied to large-capacity sodium-ion ESS, which avoids the supply chain burdens of lithium, and low-cost mobile power sources. It allows for the custom design of particle size and cycle life characteristics simply by adjusting process variables such as mixing time and additive concentration.

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Key Features:

• Preparing a first aqueous solution containing Co(NO3)2·6H2O and trisodium citrate, and a second aqueous solution containing Na4Fe(CN)6·10H2O
• Directly mixing the two aqueous solutions at a rate of 7000 ml hr-1 or higher for 20 seconds or less, followed by an aging step
• Co-precipitating particles to an average size of 90–265 nm by lowering the trisodium citrate concentration to 0.03M or less
• Cobalt hexacyanoferrate cathode active material with a cubic crystal structure, aged at a temperature between 0°C and 25°C

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