Precision anode vacancy engineering for long-lasting and fast-charging Na-Ion batteries

In the field of energy storage materials, the unique properties of vacancies are highly significant, especially in the optimization of transition metal dichalcogenides (TMDs). However, scaling up these storage solutions remains a considerable challenge. In our study, we successfully synthesized VSe2-x via alleviating selenide content, where vacancies were introduced in situ through a straightforward physical vapor transport process. These vacancies boost the adsorption capacity for sodium ions (Na+), and create additional active sites, thereby minimizing the structural changes in VSe2-x during Na+ storage. Our VSe2-x based negative electrode demonstrates impressive sodium storage capability, offering an exceptional rate performance with a capacity of 346 mAh g−1 at 5 A g−1 and maintaining a remarkable stability of 378 mAh g−1 even after 1400 cycles at 10 A g−1. Additionally, through a combination of theoretical calculations, in situ X-ray diffraction analysis, and ex situ transmission electron microscopy, we have confirmed the creation of vanadium selenide materials containing vacancies. During continuous charging and discharging, these materials facilitate the generation of numerous sodium-containing aggregates with high electronic conductivity. This paper provides a comprehensive exploration of how vacancies in transformed materials can be an effective strategy for efficient rechargeable batteries.