Yi Hao, Li Zhen, Li Xudong, Gao Peng, Zhu Yongming
Department of Applied Chemistry, Harbin Institute of Technology at Weihai, Weihai 264209, China.
ACS Appl Mater Interfaces. 2024 Aug 21;16(33):43636-43646. doi: 10.1021/acsami.4c08777. Epub 2024 Aug 8.
O3-type NaNiMnO (NNM) is very competitive for sodium-ion batteries (SIBs) due to its high capacity and easy production. Nevertheless, the intricate phase transitions during the charging-discharging significantly impede its practical application. This paper proposes a strategy for successfully synthesizing NaNiMnTiO (NNMT) by combining coprecipitation and a high-temperature solid-state method. This method introduces Ti elements while retaining the electrochemically active Ni content, thus, the NNMT has a high initial specific capacity of 151.4 mAh g at 1 C. It is demonstrated that introducing Ti leads to the transition metal layers becoming disordered by ex situ XRD, thus mitigating the irreversible phase transition of the material. In addition, Ti does not have an outer electron, which can reduce electron delocalization in the transition metal layer and improve the material's cyclic stability. The NNMT possesses a capacity retention rate of 60.66% after 150 cycles, much higher than the initial NNM's 18.96%. It also exhibits an excellent discharge capacity of 86.8 mAh g at 5 C. In conclusion, the cycling and rate performance of the Ti-substituted NNMT are greatly improved without capacity loss, which offers innovative concepts for the modification means of the SIBs layered oxide cathode materials.
O3型NaNiMnO（NNM）因其高容量和易于制备，在钠离子电池（SIBs）领域具有很强的竞争力。然而，充放电过程中复杂的相变严重阻碍了其实际应用。本文提出了一种通过共沉淀法和高温固态法成功合成NaNiMnTiO（NNMT）的策略。该方法在保留电化学活性Ni含量的同时引入了Ti元素，因此，NNMT在1 C下具有151.4 mAh g的高初始比容量。非原位XRD表明，引入Ti会导致过渡金属层无序化，从而减轻材料的不可逆相变。此外，Ti没有外层电子，可减少过渡金属层中的电子离域，提高材料的循环稳定性。NNMT在150次循环后的容量保持率为60.66%，远高于初始NNM的18.96%。它在5 C下还表现出86.8 mAh g的优异放电容量。总之，Ti取代的NNMT的循环性能和倍率性能在不损失容量的情况下得到了极大改善，为SIBs层状氧化物正极材料的改性方法提供了创新思路。
