Volatile Heterometallic Precursors for the Low-Temperature Synthesis of Prospective Sodium Ion Battery Cathode Materials

Heterometallic single-source precursors with a proper sodium:transition-metal ratio for nonoxide sodium ion battery cathode materials are reported. Heterometallic fluorinated β-diketonates NaM­(hfac)3 (M = Mn (1), Fe (2), Co (3), and Ni (4); hfac = hexafluoroacetylacetonate) have been obtained on a large scale, in high yield using a one-step reaction that employs commercially available reagents. The complexes are stable in open air and highly volatile. The mass spectrometric investigation indicates the existence of heterometallic molecules in the gas phase. The presence of heterometallic species in solutions of several solvents has been unambiguously confirmed. Heterometallic precursors were shown to exhibit clean, low-temperature decomposition in argon atmosphere that results in phase-pure perovskite fluorides NaMF3, the prospective cathode materials for sodium ion batteries.本文报道了一类具备适宜钠与过渡金属比例的异金属单源前驱体，可用于制备无氧化物钠离子电池正极材料。通过一步法使用市售试剂，可高产率、大规模合成异金属氟化β-二酮酸盐配合物NaM(hfac)₃（M = Mn(1)、Fe(2)、Co(3)、Ni(4)；其中hfac为六氟乙酰丙酮合配体（hexafluoroacetylacetonate））。该类配合物在敞口空气中稳定性良好且具有高挥发性。质谱研究证实其气相中存在异金属分子；在多种溶剂的溶液中，异金属物种的存在也得到了明确验证。实验表明，该异金属前驱体在氩气氛围下可发生洁净的低温热解，得到纯相钙钛矿型氟化物NaMF₃，该材料是极具应用前景的钠离子电池正极材料。