The advancement of sodium-ion batteries (SIBs) hinges on the development of high-capacity, durable, and cost-effective anode materials. Among the most promising candidates is hard carbon derived from polyacrylonitrile (PAN), which benefits from a high intrinsic nitrogen content and excellent thermal stability. However, conventional processing methods often lead to significant nitrogen loss during stabilization and carbonization, undermining the potential advantages of nitrogen doping. To overcome this limitation, a novel approach was implemented by incorporating 3 wt % zinc borate (ZB) into PAN-based copolymer (PANIA), resulting in a composite material designated PAZ.
ZB plays a pivotal role as a catalytic agent that accelerates the formation of conjugated ladder structures during thermal stabilization. The [BO₄]⁻ units initiate cyclization of nitrile groups through nucleophilic attack, while Brønsted acid sites promote dehydration reactions, leading to crosslinking and enhanced structural integrity.Methyl pyruvate Purity & Documentation This dual mechanism effectively suppresses the volatilization of nitrogen-containing species. X-ray photoelectron spectroscopy (XPS) confirmed that PAZ-CF-700 retained approximately 90% of the original nitrogen content after carbonization at 700 °C—among the highest reported values for PAN-derived carbons. Thermogravimetric analysis revealed a 11.8% increase in residue at 700 °C compared to pure PANIA, indicating improved yield and process efficiency.
Structural characterization demonstrated profound improvements in carbon architecture. High-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) patterns showed that PAZ-CF-700 possesses a more ordered and crystalline carbon framework, with visible lattice fringes and distinct diffraction rings corresponding to (002) and (100) planes. X-ray diffraction (XRD) analysis confirmed an expanded d-spacing of ~0.35 nm—larger than graphite’s standard value—attributed to the incorporation of boron and zinc atoms between graphitic layers, which facilitates Na⁺ intercalation. Raman spectroscopy indicated a reduced ID/IG ratio and increased lateral crystallite size (La), reflecting higher degrees of graphitization and superior charge transport capability.
Nitrogen speciation analysis revealed that PAZ-CF-700 contains a dominant proportion of pyrrolic (N2) and graphitic (N1) nitrogen species, which are known to enhance electronic conductivity and provide active sites for Na⁺ adsorption. The charge transfer resistance (Rct) was measured at only 117 Ω—significantly lower than the 370 Ω observed in PANIA-CF-700—indicating exceptional interfacial kinetics. Cyclic voltammetry (CV) analysis showed that the capacitive contribution to total charge storage reached 80.55%, highlighting fast surface-controlled ion diffusion.
Electrochemical performance was outstanding. At 100 mA g⁻¹, PAZ-CF-700 delivered a specific capacity of 190 mAh g⁻¹—nearly three times that of PANIA-CF-700 (60 mAh g⁻¹). After 200 cycles, it maintained 173 mAh g⁻¹ with 91.0% capacity retention. Rate capability tests across current densities from 100 to 3200 mA g⁻¹ yielded reversible capacities of 187, 159, 138, 116, 104, 85, and 197 mAh g⁻¹, respectively. Notably, upon returning to 100 mA g⁻¹, the capacity exceeded its initial value, demonstrating excellent reversibility and kinetic stability.2-Pyrimidineacetic acid Purity & Documentation
Long-term cycling stability was exceptional: after 4000 cycles at 1.PMID:34618275 6 A g⁻¹, PAZ-CF-700 retained 94 mAh g⁻¹ with an average Coulombic efficiency close to 100%. Scanning electron microscopy (SEM) images post-cycling confirmed minimal morphological degradation, underscoring structural robustness. The presence of ZnO nanoparticles formed during high-temperature treatment may further enhance surface reactivity and interfacial stability.
This study establishes a scalable, low-cost strategy for maximizing nitrogen utilization in PAN-based hard carbon anodes through catalyst-assisted stabilization. By preserving nitrogen content and enhancing structural order, the method delivers a synergistic improvement in capacity, rate performance, and cycle life. It provides critical insights into the design of advanced carbon materials for SIBs, paving the way for commercial-scale deployment in grid-level energy storage and other sustainable applications.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com