The critical role of sodium content on structure, morphology and electrochemical performance of layered P2-type NaxNi0.167Co0.167Mn0.67O2 for sodium ion batteries

P2-type manganese-based ternary transition metal oxides have triggered extensive researches as potential cathode materials for sodium ion batteries. However, these kinds of materials display the large difference in electrochemical performance with sodium content varying from 0.45 to 0.8, the relevant.investigations on effects of sodium content are insufficient. In this work, we synthesize a series of spherical P2-type cathode materials NaxNi0.167Co0.167Mn0.67O2 with different sodium content (x ¼ 0.45,0.55, 0.67, 0.8, 0.9, 1) and investigate the effects of sodium content on structure and electrochemical performance. The results reveal that NaxNi0.167Co0.167Mn0.67O2 (x ¼ 0.45, 0.55) consist of P2-phase and P3-phase, while NaxNi0.167Co0.167Mn0.67O2 (x ¼ 0.67, 0.8, 0.9, 1) exhibit pure P2-phase. Na0.45Ni0.167-.Co0.167Mn0.67O2 delivers an initial discharge capacity of 143 mAh g1, while a fast capacity decay is observed after 50 cycles. In comparison, Na0.67Ni0.167Co0.167Mn0.67O2 shows excellent cycling stability and rate performance. The significant difference in electrochemical performance is attributed to the initial sodium content, which leads to the existence of P3-phase. Moreover, higher sodium content promotes primary particles to grow larger and thicker, which is not favorable for the diffusion of Naþ. Generally,Na0.67Ni0.167Co0.167Mn0.67O2 is favored by suitable sodium content, offers excellent electrochemical performance in terms of capacity, rate performance and cycling stability.

基于P2型锰的三元过渡金属氧化物触发了广泛的研究，作为钠离子电池的潜在载体材料。钠含量的影响不足。不同的钠含量（x¼0.45,0.55，0.67，0.8，0.9，1），并研究钠含量对结构和电化学性能的影响。 p2期和p3期，而naxni0.167co0.167mn0.67O2（x¼0.67，0.8，0.9，1）表现出纯P2相。 NA0.45NI0.167-.CO0.167MN0.67O2的初始排放能力为143 mAh G1，而在50个周期后，速度衰减是快速的衰减，NA0.67NI0.167NI0.167CO0.167MN0.67MN0.67OMN0.67OMN0.67OCLISICE稳定性稳定性。速率性能含量促进主要颗粒的生长更大，更厚，这通常不利于NaÞ的扩散。循环稳定性。