We report on single-phase Na_xV₂(PO₄)₃ compositions (1.5 ≤ x ≤ 2.5) of the Na super ionic conductor type, obtained from a straightforward synthesis route. Typically, chemically prepared c-Na₂V₂(PO₄)₃, obtained by annealing an equimolar mixture of Na₃V₂(PO₄)₃ and NaV₂(PO₄)₃, exhibits a specific sodium-ion distribution (occupancy of the Na(1) site of only 0.66(4)), whereas that of the electrochemically obtained e-Na₂V₂(PO₄)₃ (from Na₃V₂(PO₄)₃) is close to 1. Unlike conventional Na₃V₂(PO₄)₃, when used as positive electrode materials in Na-ion batteries, the Na_xV₂(PO₄)₃ compositions lead to unusual single-phase Na⁺ extraction/insertion mechanisms with continuous voltage changes upon Na⁺ extraction/insertion. We demonstrate that the average equilibrium operating voltage observed upon Na⁺ deintercalation from single-phase Na₂V₂(PO₄)₃ is increased up to an average value of ~3.70 V versus Na⁺/Na (thanks to the activation of the V⁴⁺/V⁵⁺ redox couple) compared to 3.37 V versus Na⁺/Na in conventional Na₃V₂(PO₄)₃, thus leading to an increase in the theoretical energy density from 396.3 Wh kg^–1 to 458.1 Wh kg^–1. Electrochemical and chemical Na⁺ deintercalation from c-Na₂V₂(PO₄)₃ enables complete Na-ion extraction, increasing energy density.

我们报道了从直接合成路线获得的 Na 超离子导体类型的单相 Na_xV₂（PO₄）₃ 组成 （1.5 ≤ x ≤ 2.5）。通常，化学制备的 c-Na₂V₂（PO₄）₃ 通过退火 Na₃V₂（PO₄）₃ 和 NaV₂（PO₄）₃ 的等摩尔混合物获得，表现出特定的钠离子分布（Na（1） 位点的占用率仅为 0.66（4）），而电化学获得的 e-Na₂V₂（PO₄）₃（从 Na₃V₂（PO₄）₃） 接近 1。与传统的 Na₃V₂（PO₄）₃ 不同，当用作 Na 离子电池中的正极材料时，Na_xV₂（PO₄）₃ 成分会导致不寻常的单相 Na⁺ 提取/插入机制，在 Na⁺ 提取/插入时电压会持续变化。我们证明，与传统 Na₃V₂ （PO₄） 中的 3.37 V 相比，从单相 Na₂V₂（PO₄）₃ 进行 Na⁺ 脱嵌时观察到的平均平衡工作电压与 Na⁺/Na 相比（由于 V⁴⁺/V⁵⁺ 氧化还原对的激活）增加到了 ~3.70 V 的平均值，高达 ~3.70 V_，，从而导致理论能量密度从 396.3 Wh kg^–1 增加到 458.1 Wh kg^–1。 从 c-Na₂V₂（PO₄）₃ 进行电化学和化学 Na⁺ 脱嵌可实现完全的 Na 离子提取，从而提高能量密度。