Meaning
Structural dimension represents the average thickness of stacked graphene sheets within a carbonaceous material along the crystallographic c-axis. Measured via X-ray diffraction, crystallite height lc determines the degree of graphitization in battery anode materials. This value directly influences the operating voltage and sodium storage behavior of hard carbons.
Structural Dimension
X-ray diffraction profiles of disordered carbons display broad peaks that correspond to the graphene layers. From these profiles, the Scherrer equation calculates crystallite height lc using the full width at half maximum of the zero zero two diffraction peak. A smaller value indicates a more disordered, non-graphitizable structure.
Performance Influence
The stacking height of carbon sheets governs the path length for ion diffusion during charge and discharge cycles. In sodium-ion batteries, a small crystallite height lc prevents the formation of long-range ordered domains that resist sodium insertion. When this height remains below two nanometers, the anode offers higher capacity and less structural strain.
Conversely, excessive growth of these domains during calcination turns the carbon into a less active material.
Measurement Method
Accurate determination requires high-resolution diffractometers and precise background subtraction. Sample preparation must avoid introducing mechanical stress that broadens the diffraction peaks. Consistent measurements allow material suppliers to guarantee anode quality.
