Although LiNi
Co
Mn
O
is attracting increasing attention on account of its high specific capacity, the moderate cycle lifetime still hinders its large-scale commercialization applications. Herein, ...the Ti-doped LiNi
Co
Mn
O
compounds are successfully synthesized. The Li(Ni
Co
Mn
)
Ti
O
sample exhibits the best electrochemical performance. Under the voltage range of 2.7
4.3 V, it maintains a reversible capacity of 151.01 mAh·g
with the capacity retention of 83.98% after 200 cycles at 1 C. Electrochemical impedance spectroscopy (EIS) and differential capacity profiles during prolonged cycling demonstrate that the Ti doping could enhance both the abilities of electronic transition and Li ion diffusion. More importantly, Ti doping can also improve the reversibility of the H2-H3 phase transitions during charge-discharge cycles, thus improving the electrochemical performance of Ni-rich cathodes.
In this paper, we present a novel surface mesh generation approach that splits B-rep geometry models into isotropic triangular meshes based on neural networks and splitting lines. In the first stage, ...a recursive method is designed to generate plentiful data to train the neural network model offline. In the second stage, the implemented mesh generator, ISpliter, maps each surface patch into the parameter plane, and then the trained neural network model is applied to select the optimal splitting line to divide the patch into subdomains continuously until they are all triangles. In the third stage, ISpliter remaps the 2D mesh back to the physical space and further optimizes it. Several typical cases are evaluated to compare the mesh quality generated by ISpliter and two baselines, Gmsh and NNW-GridStar. The results show that ISpliter can generate isotropic triangular meshes with high average quality, and the generated meshes are comparable to those generated by the other two software under the same configuration.
As a promising high-capacity anode material for Li-ion batteries, NiMn2O4 always suffers from the poor intrinsic conductivity and the architectural collapse originating from the volume expansion ...during cycle. Herein, a combined structure and architecture modulation is proposed to tackle concurrently the two handicaps, via a facile and well-controlled solvothermal approach to synthesize NiMn2O4/NiCo2O4 mesocrystals with superlattice structure and hollow multi-porous architecture. It is demonstrated that the obtained NiCo1.5Mn0.5O4 sample is made up of a new mixed-phase NiMn2O4/NiCo2O4 compound system, with a high charge capacity of 532.2 mAh g-1 with 90.4% capacity retention after 100 cycles at a current density of 1 A g-1. The enhanced electrochemical performance can be attributed to the synergistic effects of the superlattice structure and the hollow multi-porous architecture of the NiMn2O4/NiCo2O4 compound. The superlattice structure can improve ionic conductivity to enhance charge transport kinetics of the bulk material, while the hollow multi-porous architecture can provide enough void spaces to alleviate the architectural change during cycling, and shorten the lithium ions diffusion and electron-transportation distances.
A critical challenge for the practical use of the layered O3-type binary nickel manganese oxides for sodium-ion batteries is the poor structural stability during extended cycling. The approaches of ...constructing O3/P2 hybrid composites can partially improve the cycling stability, but general approaches sacrifice the advantages of high capacity and low cost of the O3-type cathodes due to excessive sodium deficiency and lithium substitution. Here, we rationally design a serial of novel O3-majority hybrid Na0.9-xNi0.45Mn0.55O2 (x = 0.02, 0.04 and 0.08) cathodes, which exhibit high capacities while maintaining exceptional long-term stability. Particularly, the optimized O3/P2 Na0.88Ni0.45Mn0.55O2 composite delivers 106.7 mA h·g−1 with 71.1% capacity retention after 250 cycles at 1 C (1C = 150 mA g−1), the cyclability is 32% higher than that of the O3Na0.9Ni0.45Mn0.55O2 cathode; and it also delivers a initial discharge capacity of 75.9 mA h·g−1, maintaining 72.4% capacity retention after 1000 cycles at 10 C. More importantly, the post-cycling analyses demonstrate O3/P2 hybrid phases successfully suppress the structural degradation of Na0.9Ni0.45Mn0.55O2 during battery operation. This study provides new perspectives in designing high performance cathodes for sodium-ion batteries.
•This work reports a novel O3-majority hybrid Na0.88Ni0.45Mn0.55O2 cathode.•O3 phase and P2 phase grow with an intergrowth interfaces.•The O3/P2 hybrid Na0.88Ni0.45Mn0.55O2 shows superior electrochemical performance.•The major O3 phase guarantees a high specific capacity.•The O3/P2 hybrid phases suppress structural and electrochemical degradation.
After the 2004 Indian Ocean tsunami, the effectiveness of fringing reefs in protecting coastlines from tsunami-induced inundation has aroused great attention in the post-tsunami surveys. To better ...understand the role of fringing reefs in the mitigation of a tsunami hazard, laboratory experiments were conducted in a wave flume to study the transformation and run-up of tsunami-like solitary waves over various fringing reef profiles. The effects of incident wave height, reef-flat submergence, lagoon width and reef surface roughness were examined. Cylinder arrays were employed to create artificial roughness elements on the reef surface. Empirical formulas based on the experimental data were also proposed for the wave run-up. The ratio of the reef flat submergence to the incident wave height was always found to be the dominant parameter to characterize the wave run-ups over various tested reef profiles. Subsequently, a numerical model based on the improved Boussinesq equations including the drag effect of roughness elements was validated by the experimental data. The validated model was then applied to investigate the impacts of variations of reef morphologies (fore-reef slope, back-reef slope, reef-flat width, reef-crest width) on the solitary wave run-up.
•Tsunami-like solitary wave transformation and run-up over various fringing reef profiles were investigated experimentally.•The effects of incident wave height, reef-flat submergence, lagoon width and reef surface roughness were examined.•Wave run-up was found to depend primarily on the ratio of the reef flat submergence to the incident wave height.•A numerical model based on the improved Boussinesq equations including the roughness drag effect was validated.•The validated model was applied to investigate the impacts of variations of reef morphologies on the solitary wave run-up.
The development of the layered cathode material for sodium ion batteries are hindered by synthesis approaches. The sol-gel method is a promising way to prepare the cathodes due to the advantage of ...mixing the raw product at atomic or molecular level, while the selection criteria for complexing agents are still unclear. Herein, the Na0.9Ni0.45Mn0.55O2 cathode is successfully prepared via sol-gel method, by using sucrose, glucose, citric acid, and ethylene diamine tetra-acetic acid as the chelating agent, respectively. The effects of different chelating agents on the morphologies, structural and electrochemical properties are studied in detail. Electrochemical properties prove that the sample using citric acid shows the best electrochemical performance, delivering a capacity of 96 mAh g−1 and 48% retention after 300 cycles at 1C, and 59.6 mAh g−1 of capacity at 10 C rate, which are significantly higher than those of the other samples. XRD and HRTEM are conducted for the cycled electrodes, which demonstrate that the structure of the optimized sample maintains better phase stability and interfacial stability. This work is of considerable significance in understanding the selection criteria for the synthesis of layered cathode chelators for sodium-ion batteries by the sol-gel method.
•Layered Na0.9Ni0.45Mn0.55O2 is prepared via sol-gel method.•The effect of the chelating agents on the Na0.9Ni0.45Mn0.55O2 are discussed.•Citric acid assisted Na0.9Ni0.45Mn0.55O2 shows superior electrochemical properties.•Citric acid assisted Na0.9Ni0.45Mn0.55O2 exhibits well dynamic behavior.•Citric acid can fix more sodium and thus obtaining a stable structure.
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O3-type layered transition metal oxides (NaxTMO2) have attracted extensive attention as a promising cathode material for sodium-ion batteries because of their high capacity. However, ...the irreversible phase transition especially cycled under high voltage remains a concerning challenge for NaxTMO2. Herein, a Ti-substituted NaNi0.5Co0.2Mn0.3O2 cathode with strongly suppressed phase transition and enhanced storage stability is investigated. The Ti substitution effectively inhibits the irreversible phase transition and alleviates the structural change even charged to 4.3 V during the repeated Na+ deintercalation process. After storing in air or water, the original O3 phase structure of the material is integrally maintained without the generation of impurity phase. As a result, the as-prepared material shows excellent long-term cycle stability and rate performance when charged to a high voltage of 4.3 V.
Ni-rich cathode materials, one of the most promising cathodes for high-energy lithium-ion batteries, are still suffered from interfacial instability and bulk degradation. Herein, Zr-doped and ...Li6Zr2O7-coated LiNi0.8Co0.1Mn0.1O2 cathode, and Zr-doped Li6Zr2O7–LiNi0.8Co0.1Mn0.1O2 composite are successfully prepared via a smart one-step calcination process. The attained dual-modified architecture allows the optimized sample exhibiting enhanced rate performance while maintaining long-term stability at room temperature (82.13% after 200 cycles at 1 C rate) and even at elevated temperature. Further studies reveal that the delayed temperature-driven phase transition and the suppressed interfacial degradation can be addressed with the synergetic effects provided by the Zr-doping and Li6Zr2O7-coating. The Zr doping could improve bulk stability by reducing cation disorder. The conductive Li6Zr2O7 surface coating enhances the interfacial stability of the cathode materials while improving the electrochemical kinetics. This smart modification strategy renders Zr modification a viable modification method to enhance the electrochemical performance and structural properties of Ni-rich cathode materials.
Lithium ion batteries have been powering our daily life from portable electronic devices to electric vehicles 1–3. The lack of cathode materials with high reversible capacities and high thermal stability is still a restriction for the development of high-energy LIBs. Among the adopting options as an alternative to traditional LiCoO2 material, the layered Ni-rich ternary materials LiNixCoyMn1-x-yO2 (x≥0.5) are considered as promising candidates because of their increased energy densities and reduced cost 4–7. Specially, LiNi0.8Co0.1Mn0.1O2 (NCM) has been attracting much attention by virtue of high specific capacity of delivering more than 200 mAh•g−1 of discharge capacity 8–11.
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•Ce-doped and CeO2-coated LiNi0.5Co0.2Mn0.3O2 cathode is synthesized via a simple route.•Ce-doping can reduce the degree of cation mixing by 0.5%.•The capacity retention of ...Ce-modified NCM cathode is increased by 9.6%.•The 2% Ce-modified sample shows the best Li+ diffusion coefficient.
The well-established LiNi0.5Co0.2Mn0.3O2 (NCM523) cathode materials possess a broad prospect for Li-ion batteries. However, the NCM523 still suffers severe capacity fading and structural instability. In this research, Ce-doped and CeO2-coated NCM523 cathode materials are synthesized by a smart one-step calcination process. It is found that the CeO2 coating layer is formed during high-temperature calcination. The CeO2 coating layers stop the electrode from being exposed to the electrolyte directly and promote the kinetics of lithium deintercalation. Besides, Ce doping could suppress the bulk cation-mixing degree. Electrochemical tests suggest that Ce-modification improves the capacity retention of cathode materials. The optimized Ce-modification cathode material, among 2.7 V and 4.6 V, not only shows the best capacity retention of 76.2%, but also delivers a discharge capacity of 178.2 mAh g−1 at 1 C. This smart modification strategy provides novel ideas for advanced LIBs.
In recent years, a defect on the surface of photovoltaic (PV) modules called ‘snail trails’ has become a widespread reliability issue, affecting many modules installed in the field. In this work, ...silver acetate is identified as one component of snail trails through non-destructive Raman analysis. The chemical reaction between the silver grid line, oxygen and acetic acid on top of the micro-crack is proposed as the mechanism. The generation and/or diffusion of acetic acid released from ethylene vinyl acetate (EVA) encapsulant, oxygen and moisture are modeled using finite element method to predict the formation of silver acetate. The simulation results indicate that the existence of micro-crack plus cell gap are necessary for snail trail formation and act as the pathway for transport. As the source of acetic acid, encapsulant plays an important role in snail trail formation. Oxygen transmission rate of backsheet also has significant influence on snail trail formation. Water vapor transmission rate is shown to have no effect on snail trials over a wide rate of transmission rates. An accelerated aging snail trail test has been developed that can simulate snail trails within days, and is compared to modeling and field results.
•Silver acetate is identified as one composition of snail trails.•The reaction between silver grid line, acetic acid and oxygen is proposed as one formation mechanism.•The formation of snail trails can be simulated in accelerated aging tests.•Modeling the diffusion/generation of moisture, oxygen and acetic acid can predict silver acetate distribution.•The correlation between snail trail formation and encapsulant/backsheet properties are identified.
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