Effect of Ball Milling on the Electrochemical Performance of Li1.02Ni0.4Co0.2Mn0.4O2 Cathode Synthesized by Citric Acid-Assisted Sol-Gel Process

Layered-type Li1.02Ni0.4Co0.2Mn0.4O2 material has been synthesized by citric acid -assisted sol gel process. The resulting material was characterized by X-ray diffraction, scanning electron microscopy, charge-discharge measurements and impedance spectroscopy. The cathodes were prepared with carbon by hand grinding and ball milling. At a 0.1 C- rate and between 2.5 and 4.3 V, the hand-ground and ball-milled Li1.02Ni0.4Co0.2Mn0.4O2 samples delivered a first-cycle discharge capacity of 156 mAh/g and 167 mAh/g, respectively. At a high C-rate of 8C, the ball-milled sample gave a capacity of 133 mAh/g which was significantly higher than the capacity obtained from hand-ground sample (115 mAh/g). In a 50-cycle test at 8C, the capacity retention of hand-ground and ball-milled samples was calculated as 75% and 87%, respectively. Ball milling the active material with carbon resulted in enhanced capacity, rate capability and cycleability due to significant decrease in the contact resistance between Li1.02Ni0.4Co0.2Mn0.4O2 and carbon particles.