Meaning
Analytical metric that quantifies the volume of pores smaller than one nanometer in hard carbon anode materials using gas adsorption. Measuring carbon dioxide micropore volume provides a precise characterization of the sodium storage sites within the carbon matrix. This measurement focuses on the ultra micropores that are inaccessible to larger nitrogen molecules, allowing for a clearer understanding of the microstructural regions that govern ion insertion and diffusion.
Adsorption Method
Sorption measurements at zero degrees Celsius are performed because diffusion rates are higher at elevated temperatures. The adsorption method utilizes carbon dioxide rather than nitrogen to resolve the smallest pores. This approach ensures that the molecular sieve effects do not distort the resulting porosity data.
Anode Performance
Sodium ions insert into the ultra micropores of the anode during cell charging. Elevated values of carbon dioxide micropore volume correspond to higher plateau capacity in sodium ion batteries. However, excessive porosity can lead to high first cycle active sodium consumption.
Quality Standard
Sourcing specifications for hard carbon require a consistent distribution of these sub nanometer pores to maintain stable batch properties. A deviation in the pore volume alters the electrolyte wetting rate and the electrode density. Consistent values guarantee uniform cell performance across production lots.
