The ultrafine LiNi1/3Co1/3Mn1/3O2 powders with particle size in the range from 200 nm to 500 nm, good structural stability and higher structural integrity are directly synthesized by enhancing thermal decomposition of carbonates through a mechanochemical activation treatment to intensify the solid state diffusion reaction. These powders reveal a remarkable cycle stability from 143.8 mAh g(-1) to 116.2 mAh g(-1) in the range of 2.5-4.3 V and from 161.2 mAh g(-1) to 134.2 rnAh g(-1) in the range of 2.5-4.5 V at 1 C after 200 cycles and an excellent rate capacity from 1 C to 6 C. Moreover, their superior performance can be maintained at high testing temperature (55 C). Their discharge capacity releases 165.7 mAh g(-1) at first cycle and decreases to 158.0 inAh g(-1) at 1 C after 50 cycles in the range of 2.5-4.3 V, while it decreases from 191.5 mAh g(-1) to 169.8 mAh g(-1) with the cycle number from 1 to 50 in the range of 2.5-4.5 V.