Chenqiang Du

Synthesis and characterization of Zr-doped LiNi0.4Co0.2Mn0.4O2 cathode materials for lithium ion batteries

Li(Ni0.4Co0.2Mn0.4)1−xZrxO2 (x = 0, 0.01) was synthesized by a typical sol–gel method. The morphology, structure and electrochemical properties were characterized by SEM, XRD, charge–discharge tests, Cyclic Voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The X-ray diffraction patterns showed that the substituted elements slightly enlarged the interlayer spacing and obtained a higher degree of the well-ordered crystallographic form. The doped sample Li(Ni0.4Co0.2Mn0.4)0.99Zr0.01O2 delivered good electrochemical properties. The initial discharge capacities were 162.4 mA h g−1, 157.5 mA h g−1, 135.3 mA h g−1, 124.3 mA h g−1 at 0.2C, 0.5C, 1.0C and 2.0C, respectively. After 50 cycles, the capacity retentions were 80.5%, 70.9%, 73.4% and 68.5% at the corresponding rates, respectively. The improved electrochemical performance could be ascribed to the enhanced diffusion rate of Li+ and improved crystal structure.

Na-X zeolite templated and sulfur-impregnated porous carbon as the cathode for a high-performance Li–S battery

Significant efforts have recently been devoted to developing commercially viable high-capacity and low-cost lithium sulfur (Li–S) batteries. In this paper, we report Na-X zeolite templated porous carbon (ZPC) filled with sulfur as a cathode material for Li–S batteries. To immobilize liquid Li sulfide, the surface of NCP was modified by amphiphilic N-polyvinylpyrrolidone (PVP), making ZPC amphiphilic (denoted as A-ZPC). ZPC, A-ZPC and their corresponding composites with sulfur (ZPC–S and A-ZPC–S) were analyzed by various physical characterizations, charge–discharge profiling and electrochemical impedance spectroscopy (EIS). The results showed excellent performance of the A-ZPC–S composite cathode with 46 wt% sulfur loading, a specific capacity can be retained at 691 mA h g−1 even after 300 cycles under a rate of 1C, fading only 0.142% per cycle.

Surface modification of a LiNi0.5Mn1.5O4 cathode with lithium boron oxide glass for lithium-ion batteries

Lithium boron oxide glass (LBO-glass) coated LiNi0.5Mn1.5O4 cathode materials have been synthesized by a solution method to enhance the electrochemical performances. The structure and morphology of the as-prepared materials have been characterized by XRD, SEM, and TEM. The results indicate that the LiNi0.5Mn1.5O4 is coated with a layer of amorphous LBO-glass. The electrochemical properties are characterized by galvanostatic charge–discharge cycling, cyclic voltammetry, electrochemical impedance spectroscopy and a self-discharge test. Differential scanning calorimetry is carried out to confirm the improved safety by LBO-glass coating. The LBO coating can effectively enhance the electrochemical kinetics of the LiNi0.5Mn1.5O4 phase and improve the cycling performance. Among the as-prepared samples, the 1 wt% LBO-glass coated LiNi0.5Mn1.5O4 presents optimal electrochemical behaviors with a capacity retention of 91.4% after 100 cycles at 1 C and a discharge capacity of 105.8 mA h g−1 at 10 C. Besides, the electrochemical impedance spectroscopy analysis shows the 1 wt% LBO-glass coating reduces the electrochemical impedance and improves the ability to conduct Li+ in the cells to a great extent.

A novel sulfur-impregnated porous carbon matrix as a cathode material for a lithium–sulfur battery

A novel sulfur-impregnated porous carbon matrix (PCM-Z-S) has been prepared as a cathode material for a lithium–sulfur battery. The porous carbon matrix (PCM-Z), which was obtained using de-waxed cotton and ZnCl2 as an activator, has a surface area of 1056 m2 g−1 and a pore volume of 1.75 cm3 g−1. The PCM-Z was mixed with sublimed sulfur and then heated in nitrogen gas to form a carbon–sulfur 58 wt% composite (PCM-Z-S) which has excellent electrochemical proprieties. The PCM-Z-S delivers a capacity of 850 mA h g−1 at 1C and retains 630 mA h g−1 after nearly 200 cycles which are values much higher than that of a carbon matrix prepared without ZnCl2. These results show the sulfur-impregnated porous carbon matrix (PCM-Z-S) has great potential as a cathode material in a lithium–sulfur battery.

Synthesis and electrochemical properties of lithium zinc titanate as an anode material for lithium ion batteries via microwave method

Lithium zinc titanate (Li2ZnTi3O8) anode material has been synthesized via a microwave method for the first time. The physical and electrochemical performances of the as-prepared sample are characterized by X-ray diffraction patterns (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), galvanostatic charge–discharge tests, cyclic voltammetry (CV) tests, and electrochemical impedance spectroscopy (EIS). It is found that the pristine Li2ZnTi3O8 obtained via the microwave method at 780 W for 10 min exhibits a typical cubic spinel structure with P4332 space group. The electrochemical measurements indicate that the Li2ZnTi3O8 anode material displayed a highly reversible capacity and excellent cycling stability. The initial charge capacities of Li2ZnTi3O8 nanoparticles were 216.8 mA h g−1, 197.4 mA h g−1, 192.6 mA h g−1, 174.5 mA h g−1 at 50 mA g−1, 100 mA g−1, 300 mA g−1 and 500 mA g−1, respectively. After 50 cycles, charge capacities of 263.5 mA h g−1, 234.8 mA h g−1, 223.2 mA h g−1 and 208.4 mA h g−1 can be retained, with no significant capacity fading. This indicates that the microwave method has a great potential application in synthesizing Li2ZnTi3O8 anode materials for lithium ion batteries.