Effects of PVP-assisted Co3O4 coating on the electrochemical and storage properties of LiNi0.6Co0.2Mn0.2O2 at high cut-off voltage
Effects of PVP-assisted Co3O4 coating on the electrochemical and storage properties of LiNi0.6Co0.2Mn0.2O2 at high cut-off voltage
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DOI：
10.1016/j.electacta.2016.05.060
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发表时间：
2016-08
影响因子：
6.6
通讯作者：
Fen Tao;Xiao-xia Yan;Junjie Liu;Hongling Zhang;Li Chen
中科院分区：
文献类型：
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作者：
Fen Tao;Xiao-xia Yan;Junjie Liu;Hongling Zhang;Li Chen
采用聚乙烯吡咯烷酮（PVP）辅助的湿法包覆工艺在富镍正极材料LiNi 0. 6Co 0. 2 Mn 0. 2 O2上包覆了一层均匀的Co 3 O 4。1wt.% Co 3 O 4包覆的LiNi0.6Co0.2Mn0.2O2在4.6 V的高截止电压下，电化学性能得到了改善，尤其是循环稳定性。通过扫描电子显微镜（SEM）和透射电子显微镜（TEM）证实了其高度连续和致密的涂层。Co 3 O 4包覆层起到了HF清除剂的作用，保护了LiNi0.6Co0.2Mn0.2O2芯层不受电解液的侵蚀。循环伏安（CV）结果表明，涂层样品具有较低的极化和较高的电极反应可逆性。包覆Co 3 O 4后，LiNi 0.6Co 0.2Mn 0.2O2的存储性能也得到了改善。在空气中储存三个月后，原始的和1 wt.%的初始放电容量分别为1000 mAh和1000 mAh。Co 3 O 4包覆的LiNi0.6Co0.2Mn0.2O2在0.1C（18 mA g−1）下分别从206.4 mAh g− 1和209.5 mAh g− 1降低到177.8 mAh g− 1和198.6 mAh g−1。电化学阻抗谱（EIS）结果表明，涂层样品储存后的电荷转移电阻远小于储存的原始样品。Co 3 O 4包覆层可以防止Li 2CO 3/LiOH杂质的形成，提高了材料的储存性能。
A uniform Co3O4layer is coated on nickel-rich cathode material LiNi0.6Co0.2Mn0.2O2via a facile polyvinyl pyrrolidone (PVP)-assisted wet coating process. The 1 wt.% Co3O4-coated LiNi0.6Co0.2Mn0.2O2shows improved electrochemical performance, especially the cycling stability, at high cut-off voltage of 4.6 V. Its highly continuous and compact coating layer is confirmed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The improved performance can be attributed to Co3O4coating layer which acts as HF scavenger and protects LiNi0.6Co0.2Mn0.2O2core from electrolyte attack. Cyclic voltammetry (CV) results indicate that the coated sample exhibits lower polarization and higher reversibility of electrode reaction. The storage property of LiNi0.6Co0.2Mn0.2O2is also ameliorated by Co3O4coating. After storing in air for three months, the initial discharge capacities of pristine and 1 wt.% Co3O4-coated LiNi0.6Co0.2Mn0.2O2decrease from 206.4 mAh g−1and 209.5 mAh g−1at 0.1C (18 mA g−1) to 177.8 mAh g−1and 198.6 mAh g−1, respectively. Electrochemical impedance spectroscopy (EIS) results reveal that the charge transfer resistance of coated sample after storage is much smaller than that of stored pristine sample. The improved storage property also benefits from Co3O4coating layer which can prevent the formation of electrochemical inactive Li2CO3/LiOH impurities.