Phase Composition and Electronic Modulation of Na‐V‐PO 4 Enabling a 3.8 V Higher‐Voltage Plateau for High‐Energy Sodium‐Ion Batteries
Year: 2025
Type: article
Abstract: Two redox reactions, V 3+ /V 4+ and V 4+ /V 5+ , are accepted in Na 3 V 2 (PO 4 ) 3 (NVP) during the charge/discharge process. The discharge capacity at the higher‐voltage plateau ≈4.0 V varies with the heteroatom doping. To clarify this behavior, the V/PO 4 3− ratio is tuned in this work. The results reveal that the composition of 3Na‐0.9V‐3PO 4 is composed of the Na 7 V 4 (P 2 O 7 ) 4 PO 4 (NVPP) phase. Owing to the increased electron density around V donated by citrate ions, the apparent valence state approaches +3, resulting in a poor EPR signal. In the 3Na‐ x V‐3PO 4 /C( x = 0.9–1.5) composites, the proportion of rod/tubular‐like NVPP regularly decreases, while the NVP phase becomes increasingly dominant with rising V content. This evolution is clearly reflected in the CV curves. NVPP/C phase delivers a discharge capacity of ≈40 mAh g −1 at 117 mA g −1 with a voltage plateau near 3.8 V. As the V content increases, this high‐voltage plateau becomes shorter, while that plateau associated with NVP/C extends, leading to the increase in discharge capacity. Crystal structure and the morphology of these composites remain stable, as well as the peak of V 2p 1/2 shifts during charging/discharging, while the electron signal at the V 2p 3/2 orbital nearly disappears. These finding offers a strategy to enhance high‐voltage plateaus in sodium‐ion batteries.
Source: Small
Authors: Feifei Cui, Zimeng Bai, Zhixue Tian, Xue Gao, Ning Wang, Yujun Chai
Institution: Hebei Normal University
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W4415955429