Carbon coating method for lithium-containing phosphates

Lithium phosphate coating method using supercritical CO2 for uniform carbon precursor adsorption

This technology leverages the high permeability and wettability of supercritical carbon dioxide (scCO2) to uniformly adsorb carbon precursors onto the surfaces and pores of lithium iron phosphate (LiFePO4) particles. Subsequent calcination ensures excellent electrical conductivity and charge-discharge performance, even with a low carbon content.

LiFePO4 inherently suffers from low electrical conductivity and slow lithium-ion diffusion, which degrades performance. Conventional wet coating methods struggle to achieve uniform carbon coverage, often leading to reduced process efficiency due to excessive carbon usage, the generation of environmental pollutants, and particle agglomeration.

By dissolving carbon precursors in supercritical carbon dioxide to create a "carbon-containing CO2 fluid," this technology allows for uniform adsorption into even the finest pores of LiFePO4 particles. The particles are then calcined in a reducing atmosphere at 200–800°C to form a crystalline carbon coating layer, which is expected to overcome the limitations of existing materials when applied to secondary batteries.

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Key Features:

• Dissolving a carbon precursor in supercritical carbon dioxide within a reactor to form a carbon-containing CO2 fluid
• Immersing phosphate-based cathode active material particles in the carbon-containing CO2 fluid to adsorb the carbon precursor onto their surfaces and pores
• Calcining the phosphate-based cathode active material particles with the adsorbed carbon precursor to form a carbon coating layer
• Configuration that utilizes the permeability of supercritical carbon dioxide to achieve a uniform carbon coating with minimal carbon content

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