School of Materials Science and Engineering, Northeastern University, Shenyang 110819, PR China.
School of Materials Science and Engineering, Northeastern University, Shenyang 110819, PR China; School of Resources and Materials, Northeastern University at Qinhuangdao, Qinhuangdao 066004, PR China; Key Laboratory of Dielectric and Electrolyte Functional Material Hebei Province, Qinhuangdao, PR China.
J Colloid Interface Sci. 2019 May 15;544:164-171. doi: 10.1016/j.jcis.2019.02.094. Epub 2019 Feb 28.
P2-type transition metal oxides are promising cathode materials for sodium-ion batteries. However, due to irreversible phase transition, these batteries exhibit low capacity and poor cycling stability. In this study, highly dense, spherical P2-type oxides Na[NiCoMn]TiO (0 ≤ x ≤ 0.4) are synthesized by calcining a mixture of NaCO, spherical ternary precursor powder NiCoMnO, and different amounts of nanoscale TiO. High-temperature X-ray diffraction results obtained during calcination reveal 850 °C as the optimum calcination temperature. All materials exhibit high crystallinity without any impurity phases. The initial reversible capacities of the as-prepared samples decrease with increasing Ti substitution; however, these samples attain better cycling stability. When x = 0.2, the sample delivers an initial discharge capacity of 138 mAh g at 20 mA g between 2 and 4.5 V. Even at 100 mA g, the sample delivers 101 mAh g reversible capacity in the first cycle with capacity retention of 89.4% after 300 cycles. Moreover, the material shows sloping potential profiles, with the average voltages reaching up to ∼3.8 V. The ex-situ X-ray diffraction (XRD) results of the samples after cycling demonstrate that Ti substitution improves the structural stability. In general, Ti substitution is an effective approach for improving the electrochemical performance of ternary P2-type oxide NaNiCoMnO.
P2 型过渡金属氧化物是钠离子电池有前途的阴极材料。然而，由于不可逆的相变，这些电池表现出低容量和差的循环稳定性。在这项研究中，通过煅烧由 NaCO、球形三元前驱体粉末 NiCoMnO 和不同量的纳米级 TiO 组成的混合物，合成了高致密、球形 P2 型氧化物 Na[NiCoMn]TiO（0≤x≤0.4）。煅烧过程中获得的高温 X 射线衍射结果表明 850°C 是最佳煅烧温度。所有材料都表现出高结晶度，没有任何杂质相。所制备样品的初始可逆容量随 Ti 取代量的增加而降低；然而，这些样品具有更好的循环稳定性。当 x=0.2 时，样品在 2 至 4.5 V 之间以 20 mA g 的电流密度下首次放电的可逆容量为 138 mAh g。即使在 100 mA g 的电流密度下，样品在第一个循环中也可提供 101 mAh g 的可逆容量，在 300 次循环后容量保持率为 89.4%。此外，该材料显示出倾斜的电位曲线，平均电压高达约 3.8 V。循环后样品的原位 X 射线衍射（XRD）结果表明，Ti 取代提高了结构稳定性。总的来说，Ti 取代是改善三元 P2 型氧化物 NaNiCoMnO 电化学性能的有效方法。
