In the quest for advanced energy storage solutions, researchers have long been captivated by the potential of organic electrode materials for sodium-ion batteries. However, these materials often fall short due to poor electronic conductivity and high solubility in common electrolytes. A recent study published in *Energy Material Advances* (translated to English as “Energy Materials Advances”) offers a promising breakthrough, demonstrating how the strategic engineering of metal centers in π-d conjugated coordination polymers (CCPs) can significantly enhance sodium storage capabilities.
Lead author Mengpei Qi, from the Key Laboratory of Catalysis and Energy Materials Chemistry of Ministry of Education & Hubei Key Laboratory of Catalysis and Materials Science at South-Central Minzu University in Wuhan, China, and her team synthesized a variety of CCPs using 2,5-dihydroxy-1,4-benzoquinone (DHBQ) as a ligand, paired with different metal ions (Ni, Co, and Mn). This approach allowed them to meticulously investigate the impact of these metal sites on the electrochemical performance of the CCPs.
The study revealed that Ni-DHBQ exhibited the smallest bandgap and the highest degree of π-d conjugation, facilitating the transport of Na+ ions. “This enhanced conjugation is crucial for improving the electronic conductivity and stability of the material,” Qi explained. Consequently, Ni-DHBQ delivered impressive results, including a high capacity of 157 mAh g−1 at 0.1 A g−1, excellent rate ability of 153.9 mAh g−1 at 0.2 A g−1, and remarkable cycling stability with a capacity retention of 92.9% over 500 cycles at 1 A g−1.
The research also delved into the reaction mechanism of Ni-DHBQ using in situ x-ray diffraction, complemented by ex situ Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy. The findings suggest that π-conjugated quinone groups are responsible for the reversible accommodation of Na+ ions, providing critical insights into the molecular-level design of CCPs.
This work underscores the significance of metal centers within CCPs and offers a roadmap for developing advanced organic electrode materials with enhanced sodium-ion storage capabilities. As the energy sector continues to evolve, the insights gained from this research could pave the way for more efficient and sustainable energy storage solutions, potentially revolutionizing the way we harness and utilize renewable energy sources.
“Our findings not only highlight the importance of metal centers in CCPs but also provide a foundation for future research in this exciting field,” Qi added. With the publication of this study in *Energy Material Advances*, the scientific community is one step closer to unlocking the full potential of organic electrode materials for next-generation energy storage technologies.