采用浓度梯度加料的方式,首先沉淀制备了核为Ni(OH)2、壳为镍钴锰氢氧化物浓度梯度包覆的复合前驱体,然后配锂高温焙烧,合成了梯度包覆的镍酸锂复合正极材料Li[Ni0.92C0.04Mn0.04]O2.采用X射线衍射(XRD)、扫描电镜(SEM)、恒电流充放电测试等方法对材料的结构、表观形貌及电化学性能进行了表征.结果表明,该材料具有良好的六方单相层状α-NaFeO2结构,呈类球型状.切面元素线扫描显示该材料的包覆壳层中主要金属元素呈梯度变化.同时该新型梯度包覆的镍酸锂复合正极材料表现出了优越的电化学性能:在25℃下,2.8～4.3 V充放电范围,0.1C首次放电比容量可达198.3 mAh·g-1,循环40次容量保持96.8％; 1C和2C倍率下放电比容量可达175 mAh· g-1和165.1 mAh·g-1.55℃下,该材料首次放电比容量可达236.1 mAh·g-1,循环40次容量仍能保持77.5％.%A new core-shell structure precursor were prepared by a co-precipitation method. A gradient concentration of Ni-Co-Mn shell layer was co-precipitated on the Ni(0H)2 core which was used as the precursor. Then, the well-ordered spherical LiNi0.92Co0.04Mn0.04O2 was synthesized by sintering the mixture of as-prepared precursor and LiOH·H2O in O2. The prepared samples were characterized by X-ray diffractometry, SEM and galvanostatic charge-discharge test. The results show that, the product has a layered hexagonal α-NaFeO2 structure and a spherical morphology. The line scan test of elements on the cross section area of coating shell show that the main elements of the materials change gradiently. The initial discharge capacity is 193.8 mAh·g-1 at 0.1C rate between 2.8 and 4.3 V and retains 96.8% after 40 cycles at 25 T. The capacity at 1C and 2C is 175 mAh·g-1 and 165.1 mAh·g-1 When cycled at 55 ℃, the initial discharge capacity is 236.1 mAh·g-1 and retains 77.5% after 40 cycles, indicating good electrochemical capacity and cycling stability.
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