锂离子电池高镍正极材料掺铝的作用及掺铝方法的研究

Effects of Al-Doping on Properties of Ni-Rich Cathode Materials Employing Different Aluminum Sources

为了探究铝对高镍层状氧化物在结构、形貌及性能方面的影响,本文采用两种不同的方式掺铝以制备NCA正极材料(Li Ni0.8Co0.15Al0.05O2):一是固相法即将共沉淀合成的NC前驱体(Ni0.84Co0.16(OH)2)在混锂烧结过程混入铝源(纳米Al2O3或Al(NO3)3);二是共沉淀法即直接在合成前驱体过程中混入铝源(Al2(SO4)3或NaAlO2)即合成NCA前驱体(Ni0.8Co0.15Al0.05(OH)2.05)后再混锂烧结.结果表明,掺铝能够降低阳离子混排程度、维持层状结构的稳定性,改善材料在充放电循环过程的放电电压及中值电压大幅下降的情况,提高其循环性能.其中以NaAlO2为铝源合成NCA前驱体所制备的NCA材料性能最优:在3.0~4.3 V充放电区间,0.1C倍率下首圈放电比容量达198 m Ah·g-1,首次库仑效率可达94.6%,1C倍率下循环200圈后容量保持率达70%.

In order to investigate the effects of Al-doping on the structure,morphology and electrochemical performance of Ni-rich layered oxides,the NCA cathode materials with a nominal chemical formula of Li Ni0.8Co0.15Al0.05O2were prepared by two methods with different aluminum sources.One was the solid phase method:the precursor(Ni0.84Co0.16(OH)2)prepared by co-precipitation was mixed with lithium and aluminum source(nano-Al2O3or Al(NO3)3)thoroughly,and calcined at 780oC for 15 h under an oxygen atmosphere.The other was the co-precipitation method:the NCA precursor(Ni0.8Co0.15Al0.05(OH)2.05)was synthesized by co-precipitation method employing either Al2(SO4)3or NaAlO2as an aluminum source,and the NCA precursor was then mixed with lithium source and sintered at 780oC for 15 h under an oxygen atmosphere.The results showed that Al-doping reduced the degree of cation mixing and maintained the stability of the layered structure,thereby reducing the voltage drop and improving its cycle performance.The NCA material prepared by co-precipitation method employing NaAlO2as the aluminum source revealed the morphology of dense microspheres with a uniform size distribution and a well-layered structure of low Ni2+/Li+mixing,acheving the best performance.The as-prepared NCA cathode material delivered a high discharge capacity(198 m Ah·g-1at 0.1C)corresponding to 94.6%coulombic efficiency and good cycle stability(a capacity retention of 70%after 200 cycles at 1C)between 3.0 V and 4.3 V.