LiNi_(0.5-x)Al_(2x)Mn_(1.5-x)O_4的制备、结构及电化学特征

Preparation,Structure and Electrochemical Properties of LiNi_(0.5-x)Al_(2x)Mn_(1.5-x)O_4(0≤2x≤0.15) by Spray-Dry Process

采用喷雾干燥法合成了LiNi0.5-xAl2xMn1.5-xO4(0≤2x≤0.15)正极材料,研究Al掺杂对LiNi0.5Mn1.5O4材料结构与电化学性能的影响.通过X射线衍射(XRD)、扫描电子显微镜(SEM)、电感耦合等离子体-原子发射光谱(ICP-AES)、傅里叶红外光谱(FTIR)、循环伏安(CV)和充放电测试等手段对其结构及电化学性能进行表征.结果表明,Al取代Ni和Mn使材料的晶体结构发生了转变,空间群由P4332转变为Fd3m,同时增大了锂离子的扩散速率,提高了材料的倍率性能.在室温下,LiNi0.4 5Al0.1Mn1.45O4表现了最好的倍率性能,当放电电流为0.5 C时,放电容量为126 mA.h/g,当放电电流增加到5 C时,放电容量为109 mA.h/g,保持率达到了87%.此外,Al取代Ni和Mn有效降低了材料在高温下的Mn溶解量,从而有效改善了材料在高温大倍率下的循环性能.LiNi0.45Al0.1Mn1.45O4材料在50℃,倍率为3 C时,放电容量为121.7mA.h/g,循环50次后,仍可保留初始容量的94%.

LiNi0.5_xA12xMnl.5_xO4（0≤2x≤0.15） was prepared by spray drying process. The effects of A1 substitution for both Ni and Mn on the structural and electrochemical properties were investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, inductively coupled plasma-atomic emission spectrometry（ ICP-AES）, Fourier transform infrared spectrometer（ FTIR）, charge-discharge test and cyclic vohammetry （CV）. The results show that the substitution of A1 for Ni and Mn in the LiNi0. 5 Mnl. 5 04 resultes in the struc- tural transformation from P4332 to Fd3m in terms of the space group, which is believed to relate to the increase of the lithium diffusion coefficient, and consequently upgrade the rate capability. At room temperature the LiNio.45A10.1Mnl.4504 sample presents the best rate capability with the discharge capacity of 109 mA h/g at 5 C rate, which is about 87% of its capacity of 126 mA h/g at 0. 5 ℃. Moreover, AI substitution for Ni and Mn can effectively suppress the dissolution of manganese into the electrolyte solution when electrode was operated at elevated temperature （50 ℃ ）, resulting in a remarkable improvement in the cyclic performance at a high rate at elevated temperature. The LiNio.45A10.1Mn.4504 sample delivers a capacity of 121.7 mA h/g with a capacity retention of 94% in 50 cycles operated at 3 C rate and 50 ℃.