Synthesis And Modification Of Ni-Rich LiNi_0.8Co_0.1Mn_0.1O₂ Cathode Materials For Lithium Ion Battery

Since the first successful commercialization of lithium-ion batteries?LIBs?,they have been widely used in portable electronics,such as cell phones,laptops and cameras because of their high capacities,high voltage,long cycle life and reliable safety and are becoming more and more indispensable in our daily life.However,as the development of EV and HEV,the already commercialized cathode materials with limited capacity have become the bottleneck of obtaining advanced LIBs and higher performance cathode materials are urgently needed and drawing more and more attention.Ni-rich layered lithium transition metal oxide LiNi_1-x-yCo_xMn_yO₂?x+y?0.4?become the most promising candidate cathode material for high-energy batteries due to higher discharge capacity(more than 200 mAh g^-1),environmental friendly and high level of safety.Unfortunately,there are still some major problems needed to be solved before the nickel rich layered oxides for commercialize application as the increase of nickel content which can lead to capacity fading and poor cycle performance.In this work,LiNi_0.8Co_0.1Mn_0.1O₂ materials have been fabricated via co-precipitation method followed by calcination.Meanwhile,the optimization of calcination conditions and surface coating modification are researched systematically.The synthesized materials were characterized by X-ray diffraction?XRD?,scanning electron microscopy?SEM?,transmission electron microscopy?TEM?and energy dispersive spectrometer?EDS?,demonstrating that it had?-NaFeO₂ structure and superior crystallinity.The morphology of these samples are secondary micro sphere particles comprised of nano primary particle,and there are visible porous between primary particles.The electrochemical test showed that the product calcined at 750 ^oC for 12 h exhibits feasible electrochemical performance.In the voltage range of2.8-4.3 V,the initial discharge capacities of LiNi_0.8Co_0.1Mn_0.1O₂ at 0.2 C(40mA g^-1)and 2 C rates were 201.7 and 150 mAh g_-1,respectively and capacity retention is 81.1%and 95%after 100 cycles.To obtain higher discharge capacity,these LiNi_0.8Co_0.1Mn_0.1O₂ materials are also investigated between the voltage range of2.8-4.6 V.Although it can deliver 217.2 mAh g^-1 initial capacity,but it has poor cycle performance because of more severe structural change occurs when cycling under a higher upper cutoff voltage which hampers the application of this voltage range.To get better electrochemical performances,ZrO₂ was used to coat the LiNi_0.8Co_0.1Mn_0.1O₂ sample.The effects of nano ZrO₂ coating on the structural and electrochemical performances of the LiNi_0.8Co_0.1Mn_0.1O₂ cathode materials are also investigated in detail.Although there is minor decrease of initial discharge capacity,the capacity retention and rate performance both are enhanced because of the protective layer coated on the surface of cathode materials.