Electrochemical Na Insertion and Solid Electrolyte Interphase for Hard‐Carbon Electrodes and Application to Na‐Ion Batteries

TLDR

Lithium‑ion batteries are increasingly sought for automotive use, but uneven lithium resources and rising costs drive interest in sodium‑based alternatives, yet no successful sodium‑insertion negative electrodes have been reported due to passivation challenges. The study aims to demonstrate high‑capacity, reversible sodium insertion in hard‑carbon and NaNi₀.₅Mn₀.₅O₂ electrodes using propylene carbonate electrolyte. Hard‑carbon structural changes and passivation behavior were examined to elucidate reversible sodium insertion. The resulting 3‑V Na‑ion cell with hard‑carbon/NaNi₀.₅Mn₀.₅O₂ electrodes shows stable cycling, offering an environmentally friendly, cost‑effective alternative to Li‑ion batteries.

Abstract

Abstract Recently, lithium‐ion batteries have been attracting more interest for use in automotive applications. Lithium resources are confirmed to be unevenly distributed in South America, and the cost of the lithium raw materials has roughly doubled from the first practical application in 1991 to the present and is increasing due to global demand for lithium‐ion accumulators. Since the electrochemical equivalent and standard potential of sodium are the most advantageous after lithium, sodium based energy storage is of great interest to realize lithium‐free high energy and high voltage batteries. However, to the best of our knowledge, there have been no successful reports on electrochemical sodium insertion materials for battery applications; the major challenge is the negative electrode and its passivation. In this study, we achieve high capacity and excellent reversibility sodium‐insertion performance of hard‐carbon and layered NaNi 0.5 Mn 0.5 O 2 electrodes in propylene carbonate electrolyte solutions. The structural change and passivation for hard‐carbon are investigated to study the reversible sodium insertion. The 3‐volt secondary Na‐ion battery possessing environmental and cost friendliness, Na + ‐shuttlecock hard‐carbon/NaNi 0.5 Mn 0.5 O 2 cell, demonstrates steady cycling performance as next generation secondary batteries and an alternative to Li‐ion batteries.