【作者】 李迎；

【导师】 戴叶婧； 鲁燕萍；

【作者基本信息】 天津大学 ， 材料工程， 2019， 硕士

【摘要】 过渡金属化合物因其良好的导电性和结构稳定性受到广泛关注,而循环寿命是衡量二次电池实际应用价值的最重要因素之一,但电化学反应过程中的体积膨胀造成的电极粉化问题却极大地破坏了二次电池的循环稳定性,传统的块体电极材料又常常存在着电化学动力学缓慢的问题,基于此,本文结合了纳米材料和多孔结构的特点,利用硬模板法制备了三种多孔结构纳米正极材料并测试其电化学性能,主要研究内容及成果如下:采用硬模板法制备两种复合过渡金属氧化物多孔材料,分别为尖晶石铁酸镍空心球大孔材料和钙钛矿钛酸钡介孔材料,并将该两种材料作为载体与S复合后用于锂硫电池正极（分别记作h-NiFe₂O₄@S和P-BaTiO₃/S）,探究其电化学性能。在NiFe₂O₄空心球的物理限域和极性吸附的共同作用下,h-NiFe₂O₄@S复合材料表现出优异的电化学综合性能:首次放电比容量为948.7 m A h g^-1,表现出较大的比容量;经过200次循环后容量衰减为519.9 m A h g^-1,容量保持率为54.80%,循环稳定性良好;且当电流密度分别为200,500,1000,3000 m A g^-1时,放电比容量分别为1047,841.6,651.7,373.6 m A h g^-1,最后当电流密度再次回到200 m Ag^-1时,放电比容量恢复至1042.1 m A h g^-1,表现出优异的倍率性能。在BaTiO₃介孔材料的物理限域和自发极化的共同作用下,P-BaTiO₃/S复合材料相比于同等条件下的C/S复合材料,该复合材料表现出更加优异的循环稳定性、倍率性能和电化学可逆性,在0.1,0.2,0.5,1和2 C的电流密度下,P-BaTiO₃/S正极材料的放电比容量分别为891,624.1,561.8,498.9和474.5m A h g^-1,当电流密度回到0.1 C时,放电比容量恢复到525.1 m A h g^-1。采用硬模板法制备CMK-3有序介孔碳材料,并利用浸渍沉积法将其与过渡金属硒化物Cu₂Se纳米颗粒复合后用于钠离子电池,探究其电化学性能,利用CMK-3有序介孔碳材料的物理限域作用容纳电化学反应过程中的体积膨胀,同时增强电极材料导电性,Cu₂Se@CMK-3复合材料做正极的钠离子电池表现出良好的电化学综合性能:在0.1 C下经100次循环,平均每次的容量衰减仅为0.33%,表现出优异的循环稳定性,且还具备良好的倍率性能,在0.1,0.2,0.5,1,2 C的电流倍率下,放电容量分别为227,177,127,108,97 m A h g^-1。更多还原

【Abstract】 Transition metal compounds have received extensive attention due to their good electrical conductivity and structural stability,and cycling stability is one of the most important factors to evaluate the practical application value of secondary batteries,however,the electrode pulverization caused by volume expansion during electrochemical reaction greatly destroys the cycling stability.Moreover,the issue of poor electrochemical kinetics of the traditional block electrode materials also hinder their commercial application.Based on this,combined with the characteristics of nanomaterials and porous structures,three kinds of porous nano-positive materials were prepared by hard template method and their electrochemical properties were invetigated.The main research contents and results are as follows:Two kinds of composite transition metal oxide porous materials were prepared by hard template method,namely spinel structure nickel ferrite hollow sphere macroporous material and perovskite barium titanate mesoporous material,these two materials were used as the carrier of sulfur for cathode material of lithium-sulfur batteries to investigate electrochemical performance.Under the combination of physical limitation and polar adsorption of Ni Fe₂O₄ hollow spheres,h-Ni Fe₂O₄@S composites exhibit excellent electrochemical performance:the initial discharge specific capacity is 948.7 m A h g^-1,showing a large specific capacity;after 200cycles,the capacity is attenuated to 519.9 m A h g^-1,the capacity retention rate is54.80%,showing good cycle stability;and when the current densities are 200,500,1000,3000 m A g^-1,respectively,the discharge specific capacities were 1047,841.6,651.7,373.6 m A h g^-1,finally,when the current density returned to 200 m A g^-1 again,the discharge specific capacity recovered to 1042.1 m A h g^-1,showing excellent rate performance.Under the combined action of physical and spontaneous polarization of BaTiO₃ mesoporous materials,the composite exhibits more excellent cycling stability,rate performance and electrochemical reversibility,compared to the C/S composite under the same conditions.The discharge specific capacity of P-BaTiO₃/S cathode materials was 891,624.1,561.8,498.9 and 474.5 m A h g^-1 at current densities of 0.1,0.2,0.5,1 and 2 C,respectively.When the current density returns to0.1 C,the discharge specific capacity recovers to 525.1 m A h g^-1.CMK-3 ordered mesoporous carbon material was prepared by hard template method,and it was combined with transition metel selenide Cu₂Se nanoparticles by immersion deposition method for sodium ion battery to explore its electrochemical performance.The physical confinement effect of CMK-3 ordered mesoporous carbon material accommodates the volume expansion during electrochemical reaction and enhances the conductivity of the electrode material.The sodium ion battery using Cu₂Se@CMK-3 composite as the cathode exhibits good electrochemical performance:After 100 cycles at 0.1 C,the average capacity attenuation per time is only 0.33%,showing excellent cycling stability,and it also has good rate performance.The discharge capacities are 227,177,127,108,97 m A h g^-1 at current rates of 0.1,0.2,0.5,1,2 C,respectively.更多还原