Synthesis And Properties Of LiNi_1/3Co_1/3Mn_1/3O₂ Ternary Cathode Materials

Ternary material LiNi1/3Co1/3Mn1/3O2,which integrates the advantage of LiCoO2,LiNiO2 and LiMnO2 cathode materials,is regarded as a promising candidate cathode material for lithium-ion batteries.At present,this kind ternary material has been widely used in the 3C products and mobile powers.Moreover,in the field of electric vehicles,communications and energy storages,it also has very large space for development.In this dissertation,we focus on the synthesis and modification of LiNi1/3Co1/3Mn1/3O2 cathode materials,study the synthesis process of LiNi1/3Co1/3Mn1/3O2 material by combustion method.M-doping(M = Br,Zr,Na)and graphene coating were researching carefully.The conclusions are as follows:1.The combustion synthesis route was adapted to synthesize LiNi1/3Co1/3Mn1/3O2,and the effect of synthesis parameter on the structure and properties were researched,such as,combustion improvers,calcination temperature and calcination time.Finally,the optimum synthesis conditions are as follows: tartaric acid is used as the combustion improver,calcining at 850? for 10 h.LiNi1/3Co1/3Mn1/3O2 prepared under these conditions had high crystallinity,fine particles and uniform distribution,delivered the initial discharge capacity of 157.4mAh/g at 0.2C,and the capacity retention was 84.1% after 20 cycles.2.The LiNi1/3Co1/3Mn1/3O2-xBrx(x = 0?0.01?0.03?0.05?0.07?0.09)were synthesized by combustion method.The LiNi1/3Co1/3Mn1/3O1.95Br0.05 material had the best electrochemical performance when its doping amount was x=0.05.The initial discharge capacity of Li Ni1/3Co1/3Mn1/3O1.95Br0.05 was 169.6mAh/g at 0.2C,higher than pure phase of 12.2mAh/g,and the capacity was only 127.8mAh/g after 50 cycles.When the current density is increased to 2C,LiNi1/3Co1/3Mn1/3O1.95Br0.05 cathode material delivered the initial discharge capacity of 139.8mAh/g.In order to further improve the cycling performance of LiNi1/3Co1/3Mn1/3O1.95Br0.05 material,graphene was introduced to LiNi1/3Co1/3Mn1/3O1.95Br0.05 to get Li Ni1/3Co1/3Mn1/3O1.95Br0.05/G composites.The results showed that graphene coated LiNi1/3Co1/3Mn1/3O1.95Br0.05 had better cycling performance,the specific discharge capacity was 142.1mAh/g after 50 cycles,and the capacity retention was 83.6%.3.The Li(Ni1/3Co1/3Mn1/3)1-x Zrx O2(x = 0?0.01?0.03?0.05?0.07?0.09)powers were synthesized by combustion method,the impact of Zr content on the synthetic Li(Ni1/3Co1/3Mn1/3)1-x Zrx O2 were researched.The results showed that all the samples were of ?-NaFeO2 layered structure,and Zr doping did not change the structure of the host material.The optimum Zr doping content was x=0.05.The Li(Ni1/3Co1/3Mn1/3)0.95Zr0.05O2 cathode material delivered the initial discharge capacity of 164.3mAh/g at 0.2C,and the capacity retention was 90% after 20 cycles.It exhibited good rate capability with the specific capacity of 136.5mAh/g at 2C.4.The series of Li1-xNaxNi1/3Co1/3Mn1/3O2(x = 0?0.01?0.02?0.03?0.04)cathode materials with different amounts Na doping has been synthesized by combustion method.The results indicated that Na doping did not change the layer structure.Among these Li1-x NaxNi1/3Co1/3Mn1/3O2 cathode materials,Li0.98Na0.02Ni1/3Co1/3Mn1/3O2 cathode material delivered the initial discharge capacity of 160.2mAh/g at 0.2C,the specific capacity was 143.8mAh/g after 50 cycles,and the capacity retention was 89.8%.It exhibited good rate capability with the specific capacity of 136.0mAh/g at 2C.