Preparation and characterization of spinel/layered heterostructured xLiM2O4·(1-x)LiNi1/3Co1/3Mn1/3O2cathodes for Li-ion battery and its electrochemical properties
A series of heterostructured spinel/layered xLiM 2 O 4 ·(1-x)LiNi 1/3 Co 1/3 Mn 1/3 O 2 (M=Ni, Co, Mn; x=0, 0.1, 0.2, 0.3, 0.4, 0.5) cathodes were prepared by in-situ induced coating method. Powder X-ray diffractometry (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), galvanostetic intermittent titration technique (GITT) and galvanostatic charge-discharge tests were employed to analyze the crystal structure, micromorphology and electrochemical properties of the as prepared materials. Electrochemical results indicate that the x=0.2 sample has the best rate performance and long-term cycling stability. It delivers a discharge capacity of 137 mA·h/g at 2.7-4.3 V and 1C after 100 cycles, with the outstanding capacity retention being 93%. At 10C, the specific capacity of the material is 112 mA·h/g, which is improved greatly when compared with the pristine LiNi 1/3 Co 1/3 Mn 1/3 O 2 (95 mA·h/g at 10C). Additionally, the fast-charging test results are indicative of the fact that this cathode has sufficiently stable structure, because it can still deliver a discharge capacity higher than 120 mA·h/g after 100 cycles with capacity retention of 87% at 5C charge and 1C discharge. Galvanostatic intermittent titration technique (GITT) results show that D Li+ of x=0.2 sample is higher by one order of magnitude than the pristine LiNi 1/3 Co 1/3 Mn 1/3 O 2 , indicating that the introduced spinel phase could fundamentally enhance the electrochemical performance for cathodes.