The Study Of Nano SnO₂ Modified Nickel Cobalt Manganese Ternary Cathode Material

Nickel cobalt manganese ternary cathode material is considered to be the optimal candidate to replace LiCoO2 lithium ion battery cathode material, due to its low price, high capacity, good thermal stability and low environmental pollution. In this paper, the sol-gel method adding carrier transfer method was used to synthesise nano SnO2 modified LiNi1/3Co1/3Mn1/302 and the precipitation method was also introduced. The study of electrochemical properties and interaction mechanism within SnO2 and LiNi1/3Co1/3Mn1/3O2.was carried out.The synthesis conditions of nano SnO2 are following:pH is 3 with LAS surface active agent. During the aging time of 12 h, the colloid particle size were the most uniform, about 20-30 nm. As the ratio of activated carbon and SnO2 was 7:3, the particle size of SnO2 in SnO2/C was about 8-15 nm after immersing 5 h, and the structure of SnO2 was rutile phase.The. carrier transfer method is adopted to disperse the nano SnO2 from carbon to the surface of LiNi1/3Co1/3Mn1/3O2.The impact of nano SnO2 on LiNi1/3Co1/3Mn1/3O2 are obvious:(1) At the rate of 0.5 C, the first discharge specific capacity and coulombic efficiency were increasing; (2) The rate performance and cycle performance were improved obviously:at the rates of 1 C,2 C,5 C and 10 C, the first discharge specific capacity were 157.9、154.3、150.9、133.5 mAh g-1, respectively; The capacity retention rate was as high as 92.1% and 71.9% respectively, after 50 cycles at 1 C and 10 C rate; (3) The overcharge performance was improved. At the range of 3.0-4.8 V, after 50 cycles the discharge capacity was 90.5 mAh g-1, and the capacity retention was 55.4%; (4) The charge and discharge performance enhanced in high temperature. At 55℃, the first discharge capacity was 162.9 mAh g-1, and the retention was 92.2% after 50 cycles at the rate of 2 C; (5) The storage performance was also increased. After keeping 1 month with the charging state, the discharge specific capacity was almost equal because of existent of SnO2.The role of SnO2was indicated that:(1) The existent of SnO2 would improve the reversibility of redox reaction and specific capacity according to redox peak potential and peak area; (2) Nano SnO2 could prevent metal elements dissolving from the body material (Ni, Co, Mn) after immersed in electrolyte for one month; (3) During the process of charge-discharge, SnO2 can stabilize the crystal structure of materials; (4) Nano SnO2 could remove HF which produced by electrolyte decomposition, and improve the electrochemical performance.Precipitation method was used to prepare SnO2 modifying LiNi1/3Co1/3Mn1/3O2. Compared to the pristine sample and SnO2 modified samples with carrier transfer method, this modified sample did not increase the specific capacity of material, but greatly improves the cycle performance.