Cathode active material for sodium-ion batteries containing heteroatoms and sodium-ion batteries comprising the same

Cathode material for sodium-ion batteries with simultaneously formed tin coating and doped regions via two-stage co-precipitation

This technology maximizes structural stability in cathode active materials composed of secondary particles (agglomerates of primary particles) by simultaneously forming a coating layer containing heteroatoms like tin (Sn) at grain boundaries and a doped region where these heteroatoms are diffused within the particles.

Sodium-ion batteries have historically suffered from shortened lifespans due to crystal structure transitions caused by changes in the oxidation state of transition metals during charge and discharge cycles. High-voltage charging also leads to micro-cracks and side reactions with the electrolyte, resulting in the formation of rock-salt phases on the surface and increased resistance.

This technology involves creating a nickel-cobalt-manganese-based transition metal hydroxide through primary co-precipitation, followed by secondary co-precipitation with a tin compound to introduce heteroatoms to the particle surface, which is then calcined with a sodium compound. This process creates Sn doping inside the particles and a Na-Sn-O nano-coating on the surface, which relieves structural stress and prevents electrolyte penetration and micro-cracking. It enables high-capacity sodium cell designs that maintain performance even at 4V, making it ideal for large-capacity ESS, low-cost electric scooters, and residential energy storage systems that require reduced reliance on lithium.

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Key Features:

• Secondary particles composed of multiple primary particles that form the basic structure of the sodium-ion battery cathode active material
• Primary particle coating layer located at the grain boundaries of primary particles, containing tin, sodium, and oxygen
• Doped region formed by the diffusion of tin into the primary particles, having a lower heteroatom concentration than the coating layer
• Composite metal hydroxide obtained by sequentially performing primary co-precipitation and secondary co-precipitation with a heteroatom compound, then calcined with a sodium compound

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This invention was developed with support from the Ministry of Science and ICT for the development of core and commercialization technologies for interface-optimized, rod-shaped secondary battery materials.

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