The University of Science and Technology of China National Synchrotron Radiation Laboratory’s official website informed that the laboratory Professor Song Li’s team based on the intercalation type zinc ion battery cathode material of synchrotron radiation spectroscopy characterization proposed the concept of intercalator-induced V t2g orbital occupation, developed a fast charging performance of ammonium root intercalation vanadium pentoxide zinc ion battery cathode material. The related results were recently published in the international academic journal Proceedings of the National Academy of Sciences.
Aqueous zinc ion batteries (ZIBs) have become one of the most promising sustainable energy storage technologies due to their safety, non-toxicity, and high theoretical capacity. Among the many ZIBs electrode materials, layered vanadium oxides with tunable crystal structures and high capacity are widely studied cathode materials at this stage. Based on ionic or molecular pre-intercalation strategies, the problems of insufficient lattice space and low electron conductivity of cathode materials can be effectively solved, thus further enhancing battery performance. However, current research on intercalated cathode materials has mostly focused on the contribution of interlayer space expansion to capacity. Therefore, the development of advanced in situ characterization techniques to deeply understand the intrinsic structural changes of electrode materials caused by intercalators in terms of atomic orbitals is the key to the design and development of future high-performance cathode materials.
Figure 1. V t2g orbital occupation mechanism of NH4+-V2O5 applied to high-performance ZIBs cathode material.
Fig. 2. Analysis of NH4+-V2O5 energy storage mechanism applied to high-performance ZIBs cathode material.
This work takes advantage of the comprehensive experimental platform of synchrotron light source and combines various in situ and non-in situ synchrotron spectroscopy techniques to reveal the changes of V 3dt2g orbital occupancy in V2O5 after ammonium ion (NH4+) intercalation and the reversible evolution law during charging and discharging. It is found that the NH4+ intercalation induces structural distortion of the V-O bond to a large extent, which further leads to the rearrangement of the electronic structure and the occupation of the 3dxy vacant state in the V t2g orbital. This V t2g orbital occupation greatly improves the electrical conductivity of the material, and the broadened layer spacing after combined NH4+ intercalation significantly accelerates the transfer of zinc ions (Zn2+) and achieves the ultra-high multiplicity performance of the zinc ion battery.
The results show that the specific capacity of the ammonium intercalated vanadium pentoxide (NH4+-V2O5) cathode material remains at 101.0 mA h g-1 at a current density of 200 C, and the charging time is only 18 s. This work not only provides a basis for understanding the energy storage mechanism of Zn2+ in intercalated V2O5 materials from the atomic orbital aspect but also provides a basis for the application of high-performance zinc ion batteries in fast-charging energy storage devices. This work not only provides a basis for understanding the energy storage mechanism of Zn2+ in intercalated V2O5 materials in terms of atomic orbitals but also lays the foundation for the application of high-performance Zn-ion batteries in fast-charge energy storage devices.