无锂助熔剂B_2O_3对Li_(1.3)Al_(0.3)Ti_(1.7)(PO_4)_3固体电解质离子电导率的影响

Effect of lithium-free flux B_2O_3 on the ion conductivity of Li_(1.3)Al_(0.3)Ti_(1.7)(PO_4)_3 solid electrolyte

采用固相法制备锂离子电池用固体电解质磷酸钛锂铝Li_(1.3)Al_(0.3)Ti_(1.7)(PO_4)_3(LATP),研究了不同烧结温度以及助熔剂对LATP固体电解质离子电导率的影响.采用X射线衍射、能谱分析、扫描电镜和交流阻抗等方法,研究样品的结构特征、元素含量、形貌特征以及离子导电性能.结果表明,在900?C烧结可以获得结构致密、离子电导率较高的纯相LATP陶瓷固体电解质.与添加助熔剂Li BO2的样品进行对比实验发现,采用B_2O_3代替LiBO_2作为助熔剂也可以提高烧结样品的离子电导率,并且电解质的离子电导率随助熔剂添加量的增大,先增大后减小,其中添加质量百分比为2%的B_2O_3的样品具有最高的室温离子电导率,为1.61×10^(-3)S/cm.

Using solid electrolyte instead of liquid electrolyte is regarded as an important measure to solve the safety problems of lithium ion batteries, and has attracted wide attention of researchers. Among many solid electrolytes,Li1.3Al0.3Ti1.7（PO4）3（LATP） is considered to be one of the most commercially available solid electrolytes for its high ionic conductivity. However, as a replacement substitute of for liquid electrolyte, the LATP solid electrolyte has an ionic transport property of LATP solid electrolyte that still needs to be improved. In this paper, LATP solid electrolyte used for lithium ion batteries is successfully prepared by solid reaction process, and the influences of different sintering temperatures and addition of flux B2O3 and or LiBO2 on the ionic conductivity of LATP solid electrolyte are discussed.The structures, element content, morphologies, and ionic conductivities of the sintered samples are investigated at room temperature by X-ray diffraction, energy dispersive spectrometer, electrochemical impedance spectrum and scanning electron microscopy. It is found that pure phase LATP ceramic solid electrolyte can be obtained at the sintering temperatures between 800 and 1000℃. And the ionic conductivities of the samples first increase first and then decrease with the increasing sintering temperatures increasing. The sample with a highest ionic conductivity of 4.16 × 10^-4 S/cm can be obtained at the a sintering temperature of 900℃. Further research shows that the ionic conductivities of the sintered samples can also be effectively improved by using B2O3 instead of LiBO2 as flux. Moreover, the ionic conductivities of the samples first increase first and then decrease with the increasing amount of the flux increasing. And the highest ionic conductivity of 1.61 × 10^-3 S/cm is obtained with the sampleby adding B2O3 with a mass fraction of 2 % into the sample. The results indicate that the elevating of sintering temperature and the adding of flux B2O3 and or LiBO2 can both decreasing reducing the grain boundary impedances of the LATP samples, so as to thereby improve improving their ionic conductivities. However, when the sintering temperature is higher than 900℃ or the amount of flux B2O3 and or LiBO2 exceeds the mass percentage of 2%, the ionic conductivities of the LATP samples will drop. In addition,the ionic conductivities of the samples used using B2O3 as flux are higher than that those of the samples used LiBO2 as flux. These results also indicate that the increases of ionic conductivities of LATP samples with flux is are closely related to their densities density and compactness, and is irrespective of no matter whether or not the flux contains lithium ion.