Marshenya Sergey N, Scherbakov Alexey G, Dembitskiy Artem D, Golubnichiy Alexander A, Trussov Ivan A, Savina Aleksandra A, Kazakov Sergey M, Aksyonov Dmitry A, Antipov Evgeny V, Fedotov Stanislav S
Skolkovo Institute of Science and Technology, Skoltech, 121205, Moscow, Russian Federation.
Lomonosov Moscow State University, Chemistry Department, 119991, Moscow, Russian Federation.
Dalton Trans. 2024 Oct 1;53(38):15928-15936. doi: 10.1039/d4dt02288b.
The synthesis of langbeinite-type phosphates with small cations such as Li or Na a high-temperature solid-state reaction is a challenging task due to the predominant formation of a related NaSICON-type phase. This work reports on the synthesis route, crystal structure, thermal behavior, and Na-conductive properties of the langbeinite-type NaZr(PO) prepared by a mechanochemically activated ion-exchange reaction between hydrothermally prepared NHZr(PO) and NaNO. The crystal structure of NaZr(PO) is refined based on X-ray diffraction data and validated by Fourier-transformed infrared spectroscopy. NaZr(PO) is found to be stable up to 730 °C, undergoing a transformation into the NaSICON phase with further heating. Notably, in the 25-500 °C range, the material shows negative thermal expansion. The Na conductivity within the range of 50-225 °C amounts to 1.7 × 10 S cm at 50 °C and 1 × 10 S cm at 225 °C with an activation energy of 0.44 eV, accompanied by a sufficiently low (∼10 S cm) electronic conductivity. The bandgap of 4.44 eV and the electrochemical stability window covering the 1.39-4.18 V Na/Na range are calculated using density functional theory. The obtained results open up opportunities for designing langbeinite-structured phosphates as potential solid electrolytes for Na-ion batteries.
通过高温固态反应合成含有锂或钠等小阳离子的无水钾镁矾型磷酸盐是一项具有挑战性的任务，因为主要会形成相关的NASICON型相。本文报道了通过水热法制备的NH₄Zr(PO₄)₂与NaNO₃之间的机械化学活化离子交换反应制备的无水钾镁矾型NaZr(PO₄)₂的合成路线、晶体结构、热行为和钠传导性能。基于X射线衍射数据对NaZr(PO₄)₂的晶体结构进行了精修，并通过傅里叶变换红外光谱进行了验证。发现NaZr(PO₄)₂在高达730°C时是稳定的，进一步加热会转变为NASICON相。值得注意的是，在25-500°C范围内，该材料表现出负热膨胀。在50-225°C范围内，钠电导率在50°C时为1.7×10⁻⁴ S cm⁻¹，在225°C时为1×10⁻³ S cm⁻¹，活化能为0.44 eV，同时电子电导率足够低（约10⁻⁷ S cm⁻¹）。使用密度泛函理论计算出带隙为4.44 eV，电化学稳定窗口覆盖1.39-4.18 V的Na⁺/Na范围。所得结果为设计无水钾镁矾结构的磷酸盐作为钠离子电池的潜在固体电解质开辟了机会。
