低温熔融盐浸渍法构建富锂锰基锂离子电池正极材料的表面异质层

Construction of Heterogeneous Layer on the Surface of Li-rich Manganese-based Cathode Materials for Lithium-ion Batteries by Low Temperature Molten Salt Impregnation

通过微波水热法以及低温熔融盐浸渍法合成了一种含Zn表面异质层改性的富锂正极材料Li_(1.2)Mn_(0.56)Ni_(0.16)Co_(0.08)O_(2)(Zn-LLO).XRD表明没有杂质相的掺入,且合成的材料结晶性十分优异;在扫描电镜和透射电镜下呈现出200 nm左右的二级颗粒组成的球状一级结构;在XPS中可以看出掺入的Zn是存在的,证明了Zn表面异质层的存在.得益于微波水热法,合成的材料结晶性较好,具有较好的性能,同时得益于低温熔融盐浸渍法不破坏材料的结构又形成了Zn表面异质层,Zn-LLO展现出极其优异的电化学性能.在100 mA·g^(-1)下经过100圈的循环,Zn-LLO有209.4 mAh·g^(-1)的超高容量,并且在20,100,200,400,1000和2000 mA·g^(-1)下分别有276.8,236.1,204.4,171.1,127.8和95.1 mAh·g^(-1)的优异的平均容量.经过分析,这主要是由于Zn表面异质层对材料的保护作用,LLO与电解液减少接触使得LLO在循环过程中不容易被电解液腐蚀分解,电化学性能从而更加优异且稳定.

A lithium-rich cathode material Li_(1.2)Mn_(0.56)Ni_(0.16)Co_(0.08)O_(2)(Zn LLO)was synthesized by the microwave hydrothermal method and the low temperature molten salt impregnation method.The XRD results show that there is no impurity phase in the cathode material,and that the crystallinity of the material is excellent.Under the scanning electron microscope and transmission electron microscope,the spherical primary structure presents secondary particles of about 200 nm.It can be seen from XPS that there is doped Zn,which proves the existence of heterogeneous layer on the surface of Zn.Due to the microwave hydrothermal method,the synthesized material has both a high degree of crystallinity and a good performance.The low-temperature molten salt impregnation method does not damage the structure of the material to form the Zn heterogeneous layer on the surface of the material.Zn LLO shows an extremely excellent electrochemical performance,and after 100 cycles at 100 mA·g^(-1),it has an ultra-high capacity of 209.4 mAh·g^(-1),and an excellent average capacity of 276.8,236.1,204.4,171.1,127.8 and 95.1 mAh·g^(-1) at 20,100,200,400,1000 and 2000 mA·g^(-1),respectively.The contact between LLO and electrolyte is reduced,and LLO is not easy to be decomposed by electrolyte during cycling,which makes the electrochemical performance more excellent and stable.