Wei-Bo Hua

A further electrochemical investigation on solutions to high energetical power sources: isomerous compound 0.75Li1.2Ni0.2Mn0.6O2·0.25LiNi0.5Mn1.5O4

An isomerous layered/spinel 0.75Li1.2Ni0.2Mn0.6O2·0.25LiNi0.5Mn1.5O4 cathode material with outstanding electrochemical properties has been synthesized by a reasonable design of introducing high-power spinel LiNi0.5Mn1.5O4 material to fill up the surface gaps of pristine lithium-rich layered Li1.2Ni0.2Mn0.6O2 material with a molar ratio of 25 : 75. Morphological characterization reveals that the octahedral spinel LiNi0.5Mn1.5O4 particles are successfully coated into the surface gaps of the Li1.2Ni0.2Mn0.6O2 secondary particle, forming a special alternant structure with spherical and octahedral particles on the surface. Interestingly, some hollow sections are also observed in 0.75Li1.2Ni0.2Mn0.6O2·0.25LiNi0.5Mn1.5O4 material, confirmed from the TEM images. The structural characterization demonstrates that this isomerous compound is more well-defined α-NaFeO2 configured, more enlarged in Li layer spacing and lower in cation disordered degree. The exquisite morphology and ideal structure endow this nanocrystal-assembled composite significantly enhanced electrochemical performance with high capacity, good rate capability and excellent cycling stability, compared with the pristine Li1.2Ni0.2Mn0.6O2. It delivers a discharge capacity of 135 mA h g−1 even at an ultrahigh current density of 2000 mA g−1 (10 C). Moreover, the superior cycling stability is also observed with high discharge capacities of 254 mA h g−1 and 222 mA h g−1 at 0.5 C and 1 C after 100 cycles with capacity retention of 98% and 94%, respectively. Moreover, the fast-charging test results are indicative of the fact that this layered/spinel cathode could be used in practical application. Its discharge capacity is 176 mA h g−1 at 1 C after 50 cycles with the charge rate of 10 C. Furthermore, the composite can endure high current charging and discharging even at a high cut-off potential (5.0 V), whereas the pristine Li1.2Ni0.2Mn0.6O2 material cannot. Therefore, we absolutely believe that this isomerous layered/spinel 0.75Li1.2Ni0.2Mn0.6O2·0.25LiNi0.5Mn1.5O4 cathode is a promising candidate for the commercial development of advanced LIBs.

Designed synthesis of Zr-based ceria–zirconia–neodymia composite with high thermal stability and its enhanced catalytic performance for Rh-only three-way catalyst

Developing advanced oxygen storage materials that deliver high thermal stability is crucial to meeting increasingly stringent environmental regulations for three-way catalysts (TWCs). The surfactant, trialkylamine (N235, N (CnH2n+1), n = 8–10), was used to prepare the zirconium (Zr)-based ceria–zirconia–neodymia composites with loose morphology for the first time, and the effect of N235 on the properties of the ceria–zirconia–neodymia solid solution composites was investigated systematically. After thermal treatment at 1000 °C for 5 h in air, the obtained material (CZ/N235-1000) presented a high surface area of 31 m2 g−1 and had superior redox properties. As a support material in rhodium (Rh)-only TWCs, the prepared Rh/CZ/N235-f and Rh/CZ/N235-a demonstrated excellent catalytic performances. Particularly, after aging at 1000 °C for 5 h in air, the light off temperature (T50%) of nitrogen oxide and carbon monoxide for Rh/CZ/N235-a were 229 °C and 235 °C, respectively, and were much lower than those (278 °C and 280 °C) of Rh/CZ-a in which the support material was synthesized without N235. Therefore, this work provides a simple and scalable synthesis route for advanced oxygen storage materials.

Shape-controlled synthesis of hierarchically layered lithium transition-metal oxide cathode materials by shear exfoliation in continuous stirred-tank reactors

Developing hierarchically layered cathode materials with high performance is key to further improving advanced lithium-ion batteries, but it is challenging to synthesize such systems with controllable shape on a large scale. We used a high-shear mixer to continuously prepare flower-like hydroxide precursors via a co-precipitation method in a continuous stirred-tank reactor (CSTR). After the lithiation reaction, hierarchical lithium transition-metal oxides with predominantly exposed electrochemically active {010} planes are produced. The electrochemical properties of these peculiar materials (i.e. LiNi1/3Co1/3Mn1/3O2, LiNi0.6Co0.2Mn0.2O2 and Li1.2Ni0.2Mn0.6O2) are demonstrated to be excellent. Particularly, LiNi1/3Co1/3Mn1/3O2 exhibits a durable high-rate capability with a capacity retention of 98.2% after 500 cycles at 20C between 2.7 and 4.3 V. This work provides a new technology to fabricate two-dimensional nanoarchitectured electrode materials. Moreover, the outstanding electrochemical properties of this hierarchically structured cathode material in combination with the scalable method make it highly interesting for commercialization.

Effective enhancement of the electrochemical performance of layered cathode Li1.5Mn0.75Ni0.25O2.5 via a novel facile molten salt method

A series of nanocrystalline lithium-rich cathode materials Li1.5Mn0.75Ni0.25O2.5 have been prepared by a novel synthetic process, which combines the co-precipitation method and a modified molten salt method. By using a moderate excess of 0.5LiNO3–0.5LiOH eutectic salts as molten media and reactants, the usage of deionized water or alcohol in the subsequent wash process is successfully reduced, compared with the traditional molten salt method. The materials with different excess Li salt content, Li/M (M = Ni + Mn) = 1.55, 1.65, 1.75, 1.85, 1.95, 2.05, molar ratio, show distinct differences in their structure and charge–discharge characteristics. The structural characterization demonstrates that the sample with a ratio of Li/M = 1.85 has a more well-defined α-NaFeO2 structure and a more enlarged Li layer spacing. It also exhibits the best comprehensive electrochemical behavior with the highest coulombic efficiency, the best rate capability and optimal cycling stability. More specifically, it delivers a dramatically improved initial coulombic efficiency of 87.86%, and a discharge capacity of 129 mA h g−1 even at an ultra-high current density of 2000 mA g−1 (10C). Meanwhile a superior cycling stability is also observed with a high discharge capacity of 251 mA h g−1 and a retention of 98% at 0.2C after 50 cycles. Our results reveal that this method is facile and feasible to synthesize a high rate and high capacity lithium-rich material.

Design and Synthesis of Layered Na2Ti3O7 and Tunnel Na2Ti6O13 Hybrid Structures with Enhanced Electrochemical Behavior for Sodium-Ion Batteries

Abstract A novel complementary approach for promising anode materials is proposed. Sodium titanates with layered Na2Ti3O7 and tunnel Na2Ti6O13 hybrid structure are presented, fabricated, and characterized. The hybrid sample exhibits excellent cycling stability and superior rate performance by the inhibition of layered phase transformation and synergetic effect. The structural evolution, reaction mechanism, and reaction dynamics of hybrid electrodes during the sodium insertion/desertion process are carefully investigated. In situ synchrotron X‐ray powder diffraction (SXRD) characterization is performed and the result indicates that Na+ inserts into tunnel structure with occurring solid solution reaction and intercalates into Na2Ti3O7 structure with appearing a phase transition in a low voltage. The reaction dynamics reveals that sodium ion diffusion of tunnel Na2Ti6O13 is faster than that of layered Na2Ti3O7. The synergetic complementary properties are significantly conductive to enhance electrochemical behavior of hybrid structure. This study provides a promising candidate anode for advanced sodium ion batteries (SIBs).