A core-shell structure spinel cathode material with a concentration-gradient shell for high performance lithium-ion batteries

A novel spinel cathode material with an average composition of LiMn1.912Ni0.072Co0.016O4, in which the LiMn2O4 core material is completely encapsulated by a stable spinet structure concentration-gradient shell (CGS), is successfully synthesized via co-precipitation process. The spherical LiMn2O4 core is encapsulated by CGS that increased continuously Ni and Co contents, and the composition of the outmost layer of the spherical LiMn1.912Ni0.072Co0.016O4 is LiNi0.45Mn1.45Co0.1O4. The electrochemical properties of the LiMn1.912Ni0.072Co0.016O4 compared to the LiMn2O4 are carefully investigated by galvanostatic charge discharge, cyclic voltammetric and electrochemical impedance spectroscopy. It has been found that the electrochemical properties of the LiMn1.912Ni0.072Co0.016O4 material are far superior to those of the alone LiMn2O4 core material. Besides, the LiMn1.912Ni0.072Co0.016O4 sample exhibits excellent cycling stability at elevated temperature. It delivers a discharge capacity of 118 mAh g(-1) between 3.0 and 4.4 V vs. Li/Li+ with a retention of 96% over 200 cycles at a rate of 1 C (148 mA g(-1)) at 55 degrees C. In the same time, the LiMn1.912Ni0.072Co0.016O4 shows also a good rate capability. It can still deliver a high discharge capacity of over 110 mAh g(-1) even at a rate of 5 C. Therefore, the core-shell structure spinet cathode material with CGS will be a promising cathode material for advanced lithium ion batteries. (C) 2014 Elsevier B.V. All rights reserved.