Improving the electrochemical performance of layered cathode oxide for sodium-ion batteries by optimizing the titanium content
Improving the electrochemical performance of layered cathode oxide for sodium-ion batteries by optimizing the titanium content
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通过优化钛含量提高钠离子电池层状正极氧化物的电化学性能
DOI：
10.1016/j.jcis.2019.02.094
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发表时间：
2019
影响因子：
9.9
通讯作者：
Qing Wang
中科院分区：
文献类型：
--
作者：
Shuo Bao;Shao-hua Luo;Zhi-yuan Wang;Sheng-xue Yan;Qing Wang
p2型过渡金属氧化物是很有前途的钠离子电池正极材料。然而，由于不可逆的相变，这些电池表现出低容量和循环稳定性差。本研究以Na2CO3、球形三元前驱体粉末Ni0.167Co0.167Mn0.67 o2和不同量的纳米TiO2为原料，煅烧合成了高密度的球形p2型氧化物Na-0.67[Ni0.167Co0.167Mn0.67 67](1-x)TixO2 （0 <= x <= 0.4）。高温x射线衍射结果表明，850℃为最佳煅烧温度。所有材料均表现出高结晶度，无任何杂质相。制备样品的初始可逆容量随着Ti取代量的增加而降低；然而，这些样品获得了更好的循环稳定性。当x = 0.2时，样品在2和4.5 V之间的20毫安时提供138毫安时g（-1）的初始放电容量。即使在100ma g（-1）下，样品在第一次循环中提供101 mAh g（-1）的可逆容量，在300次循环后容量保持率为89.4%。此外，该材料呈现出倾斜的电位分布，平均电压最高可达3.8 V。循环后样品的x射线衍射（XRD）结果表明，Ti取代提高了结构的稳定性。总的来说，Ti取代是改善三元p2型氧化物Na0.67Ni0.167Co0.167Mn0.67O2电化学性能的有效途径。
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-0.67[Ni0.167Co0.167Mn0.67](1-x)TixO2 (0 <= x <= 0.4) are synthesized by calcining a mixture of Na2CO3, spherical ternary precursor powder Ni0.167Co0.167Mn0.67O2, and different amounts of nanoscale TiO2. High-temperature X-ray diffraction results obtained during calcination reveal 850 degrees 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(-1) at 20 mA g(-1) between 2 and 4.5 V. Even at 100 mA g(-1), the sample delivers 101 mAh g(-1) 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 similar 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 Na0.67Ni0.167Co0.167Mn0.67O2.