Excellent cyclability of P2-type Na–Co–Mn–Si–O cathode material for high-rate sodium-ion batteries
Excellent cyclability of P2-type Na–Co–Mn–Si–O cathode material for high-rate sodium-ion batteries
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DOI：
10.1007/s10853-019-03807-y
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发表时间：
2019-10
影响因子：
4.5
通讯作者：
Lijun Wang;Yanzhi Wang;Xiaheng Yang;Jinlong Wang;Xiduo Yang;Jiantao Tang
中科院分区：
文献类型：
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作者：
Lijun Wang;Yanzhi Wang;Xiaheng Yang;Jinlong Wang;Xiduo Yang;Jiantao Tang
以非金属元素硅为掺杂剂，采用简单固相法制备了P2型Na2/3Co0.25Mn0.705Si0.045O2(Si-NCM)高倍率正极材料。X射线衍射谱证实了P2型六方结构的空间群为(SG：P63/MMC)，其中Si4+离子取代了P2-Na2/3Co0.25Mn0.75O2(NCM)晶格中的Mn位，没有任何与Si有关的杂质相。硅纳米管在0.1C时的初始容量为144mAhg−1,100次循环后的容量保持率为80.1%，1℃时的放电容量为120mAhg−1,200次循环时的容量保持率为83.4%。特别是，在5℃下，260次循环后的容量保持率为90.2%，500次循环后的容量保持率为85.8%。与NCM相比，掺硅可以加快Si-NCM的循环稳定性，这是由于Si-O、Tm-O和O-O键更强，在晶胞内钠钠石中的占有率更稳定，特别是由于在Na+的提取和嵌入过程中P2-P3-P2发生了可逆的两相转变。因此，SiO_2 As掺杂剂是发展SIB高倍率正极材料的一种新策略。
P2-type Na2/3Co0.25Mn0.705Si0.045O2(Si-NCM) high-rate cathode was designed by using silicon of the nonmetallic element as dopant and developed by the simple solid-state route for sodium-ion batteries. XRD refinements confirm the P2-type hexagonal structure with space group (SG: P63/mmc), in which Si4+ions substitute the Mn site of P2-Na2/3Co0.25Mn0.75O2(NCM) lattice without any impurity phases of Si-related substances. Si-NCM delivers the initial capacity of 144 mAh g−1at 0.1 C with the capacity retention of 80.1% after 100 cycles, and the discharge capacity of 120 mAh g−1at 1 C with 83.4% retention at 200th cycle. Particularly, excellent capacity retentions of 90.2% after 260 cycles and 85.8% after 500 cycles at 5 C have been achieved. Si-doping can expedite the superior cycle stability of Si-NCM compared to NCM, which is attributed to the more powerful Si–O, TM–O and O–O bonds, more stable occupancy rate in the Naesite of unit cell and particularly ascribed to the reversible two-phase transition of P2–P3–P2 in the process of Na+extraction and intercalation. Hence, SiO2as dopant is a novel strategy with regard to the development of high-rate cathode materials for SIBs.