Hu Yongsheng

New layered metal oxides as positive electrode materials for room-temperature sodium-ion batteries

In order to achieve better Na storage performance, most layered oxide positive electrode materials contain toxic and expensive transition metals Ni and/or Co, which are also widely used for lithium-ion batteries. Here we report a new quaternary layered oxide consisting of Cu, Fe, Mn, and Ti transition metals with O3-type oxygen stacking as a positive electrode for room-temperature sodium-ion batteries. The material can be simply prepared by a high-temperature solid-state reaction route and delivers a reversible capacity of 94 mAh/g with an average storage voltage of 3.2 V. This paves the way for cheaper and non-toxic batteries with high Na storage performance.

Significant effect of electron transfer between current collector and active material on high rate performance of Li4Ti5O12

The rate and cycling performances of the electrode materials are affected by many factors in a practical complicated electrode process. Learning about the limiting step in a practical electrochemical reaction is very important to effectively improve the electrochemical performances of the electrode materials. Li4Ti5O12, as a zero-strain material, has been considered as a promising anode material for long life Li-ion batteries. In this study, our results show that the Li4Ti5O12 pasted on Cu or graphite felt current collector exhibits unexpectedly higher rate performance than on Al current collector. For Li4Ti5O12, the electron transfer between current collector and active material is the critical factor that affects its rate and cycling performances.

Highly Efficient Dye-Sensitized Solar Cells Using a Composite Electrolyte Consisting of LiI(CH3OH)4-I2, SiO2Nano-Particles and an Ionic Liquid

Solid-state electrolyte LiI(CH3OH)4-I2 is used in dye-sensitized solar cells (DSSCs). The DSSCs using only the LiI(CH3OH)4-I2 electrolyte show very poor performance due to the quick crystal growth of LiI(CH3OH)4. In order to improve the performance of DSSCs, we prepare a composite electrolyte by adding SiO2 nano-particles and an ionic liquid, 1-methyl-3-ethylimidazolium iodide, into the original solid-state electrolyte. High efficiency of 4.3% is achieved by applying this composite electrolyte to DSSCs.

Electrical properties of zinc-oxide-based thin-film transistors using strontium-oxide-doped semiconductors*

Strontium-zinc-oxide (SrZnO) films forming the semiconductor layers of thin-film transistors (TFTs) are deposited by using ion-assisted electron beam evaporation. Using strontium-oxide-doped semiconductors, the off-state current can be dramatically reduced by three orders of magnitude. This dramatic improvement is attributed to the incorporation of strontium, which suppresses carrier generation, thereby improving the TFT. Additionally, the presence of strontium inhibits the formation of zinc oxide (ZnO) with the hexagonal wurtzite phase and permits the formation of an unusual phase of ZnO, thus significantly changing the surface morphology of ZnO and effectively reducing the trap density of the channel.

Recent progress in structure study of electrode materials for room-temperature sodium-ion stationary batteries

With the rapid development of renewable energy of wind and solar power and realization of future smart grid, the large-scale energy storage system becomes more and more important. Recently, room-temperature sodium-ion batteries re-attract a great deal of attention due to its low cost and potential application in large-scale energy storage. So far, a large amount of electrode materials have been proposed for sodium-ion batteries. In general, the electrochemical performance of electrodes is determined by its crystal structure. In this review, we summarize the crystal structures of present electrodes and intend to provide insightful guides to electrode material design.

溶胶-凝胶法制备钠离子固态电解质Na 3 Zr 2 Si 2 PO 12 及其电导性能研究

采用溶胶-凝胶法, 探索了合成纯相Na 3 Zr 2 Si 2 PO 12 的条件, XRD分析表明前驱体中Na和P 均过量10%时, 在1050℃下烧结得到了纯相的Na 3 Zr 2 Si 2 PO 12 , 而P不过量时, 得到的产物中含有少量的ZrO 2 杂质。电化学阻抗谱测试表明Na和P 均过量10%时, 烧结得到的陶瓷片室温离子电导率达到了5.4×10 -4 S/cm, 比P不过量时烧结得到样品的离子电导率(室温时为3.7×10 -4 S/cm)要高。进一步分析可知高温下P的挥发造成ZrO 2 杂质相的析出, 从而使得离子电导率降低。与固相法相比, 溶胶-凝胶法需要的烧结温度更低, 且制得的样品的离子传导性更好。NASICON-structured Na3Zr2Si2PO12 was synthesized by a Sol-Gel approach. Phase-pure samples were successfully sintered at 1050 degrees C when adding 10% excessive Na and P in the precursors, while a small amount of ZrO2 impurity was detected without adding excessive phosphorus. Electrochemical impedance spectrum tests indicate that the ionic conductivity of the former is as high as 5.4x10(-4) S/cm at room temperature, which is higher than that of samples prepared from the precursors without adding excessive phosphorus (3.7x10(-4) S/cm). Further analysis reveals that the evaporation of phosphorus at high temperature would cause the formation of ZrO2 impurity in the samples, leading to a lower ionic conductivity. Compared with solid state reaction approach, samples with enhanced ionic conductivity can be obtained at a rather lower temperature by Sol-Gel synthesis.采用溶胶-凝胶法, 探索了合成纯相Na 3 Zr 2 Si 2 PO 12 的条件, XRD分析表明前驱体中Na和P 均过量10%时, 在1050℃下烧结得到了纯相的Na 3 Zr 2 Si 2 PO 12 , 而P不过量时, 得到的产物中含有少量的ZrO 2 杂质。电化学阻抗谱测试表明Na和P 均过量10%时, 烧结得到的陶瓷片室温离子电导率达到了5.4×10 -4 S/cm, 比P不过量时烧结得到样品的离子电导率(室温时为3.7×10 -4 S/cm)要高。进一步分析可知高温下P的挥发造成ZrO 2 杂质相的析出, 从而使得离子电导率降低。与固相法相比, 溶胶-凝胶法需要的烧结温度更低, 且制得的样品的离子传导性更好。