Zhenjiang He

A novel architecture designed for lithium rich layered Li[Li0.2Mn0.54Ni0.13Co0.13]O2 oxides for lithium-ion batteries

Lithium rich manganese layered oxides (Li[Li0.2Mn0.54Ni0.13Co0.13]O2) with three kinds of architectures (conventional small particles, solid spherical particles and novel hollow spherical particles) are synthesized by co-precipitation followed by calcination. Their interior architectures have been studied through observation of cross-sections, and electrochemical impedance spectroscopy (EIS) has been utilized to gain insight into their properties. Conventional small particles have a high specific surface area (3.3467 m2 g−1) that may cause corrosion in an electrolyte to more easily happen on its surface. Solid spherical particles show unsatisfactory electrochemical properties that could result from the long diffusion path (can reach 10.1 μm). Hollow spherical particles illustrate a low specific surface area (0.4648 m2 g−1) and short diffusion path (about 1.5 μm) at the same time, which enhanced their performance during the electrode process (271 mA h g−1 of initial discharge capacity). The electrochemical performance of hollow spherical particles is significant in the development of lithium rich manganese layered oxides.

Electrochemical Analysis for Enhancing Interface Layer of Spinel Li4Ti5O12: p-Toluenesulfonyl Isocyanate as Electrolyte Additive.

An electrolyte additive, p-toluenesulfonyl isocyanate (PTSI), is evaluated in our work to overcome the poor cycling performance of spinel lithium titanate (Li4Ti5O12) lithium-ion batteries. We find that the cycling performance of a Li/Li4Ti5O12 cell with 0.5 wt % PTSI after 400 cycles is obviously improved. Remarkably, we also find that a solid electrolyte interface (SEI) film is formed about 1.2 V, which has higher potential to generate a stable SEI film than do carbonate solvents in the voltage range of 3.0-0 V. The stable SEI film derived from PTSI can effectively suppress the decomposition of electrolyte, HF generation, interfacial reaction, and LiF formation upon cycling. These observations are explained in terms of PTSI including SO3. The S═O groups can delocalize the nitrogen core, which acts as the weak base site to hinder the reactivity of PF5. Hence, HF generation and LiF formation are suppressed.

Synthesis and characterization of a sulfur/TiO 2 composite for Li-S battery

S/TiO2 composite is prepared via a simple solution method by using sublimed sulfur and nanosized TiO2. The composite is characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and Brunauer–Emmett–Teller (BET) test. The results indicate that the sulfur is well dispersed in the composite. The electrochemical performance of the composite as cathode material was evaluated by cycling under constant current cyclic voltammetric (CC-CV) mode at room temperature and cyclic voltammetry (CV). The S/TiO2 composite can effectively confine the diffusion of dissolved polysulfides in electrolyte and stabilize the structure during the charge and discharge process and shows high capacity and good rate performance.

Comparative Investigation of 0.5Li2MnO3·0.5LiNi0.5Co0.2Mn0.3O2 Cathode Materials Synthesized by Using Different Lithium Sources

Lithium-rich manganese-based cathode materials has been attracted enormous interests as one of the most promising candidates of cathode materials for next-generation lithium ion batteries because of its high theoretic capacity and low cost. In this study, 0.5Li2MnO3·0.5LiNi0.5Co0.2Mn0.3O2 materials are synthesized through a solid-state reaction by using different lithium sources, and the synthesis process and the reaction mechanism are investigated in detail. The morphology, structure, and electrochemical performances of the material synthesized by using LiOH·H2O, Li2CO3, and CH3COOLi·2H2O have been analyzed by using Thermo gravimetric analysis (TGA), X-ray diffraction (XRD), Scanning electron microscope (SEM), Transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), and electrochemical measurements. The 0.5Li2MnO3·0.5LiNi0.5Co0.2Mn0.3O2 material prepared by using LiOH·H2O displays uniform morphology with nano particle and stable layer structure so that it suppresses the first cycle irreversible reaction and structure transfer, and it delivers the best electrochemical performance. The results indicate that LiOH·H2O is the best choice for the synthesis of the 0.5Li2MnO3·0.5LiNi0.5Co0.2Mn0.3O2 material.

Multiple Linkage Modification of Lithium-Rich Layered Oxide Li1.2Mn0.54Ni0.13Co0.13O2 for Lithium Ion Battery

A multiple linkage modification (MLM) method was investigated to comprehensively improve the properties of lithium-rich layered oxides. MLM Li1.2Mn0.54Ni0.13Co0.13O2 was successfully synthesized via continuous and appropriate heat treatment. The synthesized Li1.2Mn0.54Ni0.13Co0.13O2 particles were coated with a Li2ZrO3 layer and doped with Zr4+ by using a Zr compound as the MLM reagent. The Li2ZrO3 coating layer could protect materials from the corrosion of hydrogen fluoride, and the structure of the base materials was stabilized due to Zr4+ doping. In addition, the formation of Li2ZrO3 captured inactive residual lithium on the surface and absorbed lithium of host materials, thereby leading to the reduction in the Li/M ratio of materials and promoting the first-cycle Coulombic efficiency. The MLM material delivered the highest initial cycle Coulombic efficiency (∼85%), the best cycle and rate performance among bare and ZrO2-coated particles. These results indicate that MLM is an important technique for improving the performance of electrode materials.