Lithium iron phosphate (LiFePO4, LFP), an olivine–type cathode material, represents a highly suitable cathode option for lithium–ion batteries that is widely applied in electric vehicles and ...renewable energy storage systems. This work employed the ball milling technique to synthesize LiFePO4/carbon (LFP/C) composites and investigated the effects of various doping elements, including F, Mn, Nb, and Mg, on the electrochemical behavior of LFP/C composite cathodes. Our comprehensive work indicates that optimized F doping could improve the discharge capacity of the LFP/C composites at high rates, achieving 113.7 mAh g−1 at 10 C. Rational Nb doping boosted the cycling stability and improved the capacity retention rate (above 96.1% after 100 cycles at 0.2 C). The designed Mn doping escalated the discharge capacity of the LFP/C composite under a low temperature of −15 °C (101.2 mAh g−1 at 0.2 C). By optimizing the doping elements and levels, the role of doping as a modification method on the diverse properties of LFP/C cathode materials was effectively explored.
In this paper, the photovoltaic performance and charge recombination of the dye-sensitized solar cells (DSCs) based on nitrogen-doped TiO2 electrodes were investigated in detail. A negative shift of ...the flatband potential (V fb) of nitrogen-doped TiO2 film was attributed to the formation of an O−Ti−N bond, and it was indicated that the position of the edge of the V fb is shifted to negative, resulting in the improvement of the open circuit voltage for DSC with nitrogen doping. The UV−vis spectrum of the nitrogen-doped film exhibited a visible absorption in the wavelength range from 400 to 500 nm. The back electron transfer of the nitrogen-doped DSC was studied by measuring the electrochemistry impedance spectra (EIS), and the EIS for DSCs showed that the enhanced electron lifetime for nitrogen-doped TiO2 solar cells could be attributed to the formation of O−Ti−N in the TiO2 electrode to retard the recombination reaction at the TiO2 photoelectrode/electrolyte interface as compared to the undoped TiO2 solar cells. The photovoltaic performance of the DSC under high temperature conditions and one soaking in sun light for more than 1000 h indicated that the nitrogen-doped TiO2 solar cells exhibited better stability. It indicated that the formation of O−Ti−N in the TiO2 electrode influences the performance of the DSC. Especially, the introduction of nitrogen into the DSC can stabilize the DSC system due to the replacement of oxygen-deficient titania by nitrogen-doped TiO2.
Based on the discrete element method (DEM), a numerical simulation of the Xiamadazi landslide caused by the Haiyuan earthquake in 1920 was conducted in this study. The three-dimensional space–time ...dynamic evolution process of the loess landslide was reproduced, and its motion characteristics were analyzed, which laid a theoretical foundation for the effective prevention of loess landslides caused by strong earthquakes. The parameters are calibrated through multiple triaxial compression tests to ensure consistency between microscopic and macroscopic strength characteristics of loess, establishing a solid foundation for analyzing the landslide’s failure process and motion characteristics. Additionally, the contour line generated by digital elevation model ( DEM) is used to construct the landslide surface, which accurately reflects the terrain and truly reproduces the evolution process of Xiamadazi landslide under seismic action. The results show that the Xiamadazi landslide is a thrust-type landslide with shoulder cracking, the maximum average velocity of the landslide is 11.1 m/s, and the maximum average displacement is 534 m. The whole movement process reflects the characteristics of a fast sliding velocity, long sliding distance and wide disaster range. The Xiamadazi landslide is a loess landslide. In the process of landslides, many weak cements of loess are destroyed, and the destruction of weak cements of loess increases the impact energy and disaster range of landslides. This destruction is also an important factor in high-velocity loess landslides. The results of this study provide a reference for disaster prevention and mitigation in similar areas in the future.
The reversibility of Zn plating/stripping during cycling is adversely affected by dendritic growth, electrochemical corrosion, surface passivation, and hydrogen generation on the Zn anodes for ...rechargeable aqueous zinc ion batteries (ZIBs). Herein, through an ordinary anodic etching process, a uniform porous ZnP matrix protective layer was created on the Zn foil (Zn@ZnP). The large and accessible specific surface area of the prepared Zn@ZnP can facilitate contact with the electrolyte, accelerating the migration and enhancing the desolvation of Zn2+, effectively enhancing the Zn deposition kinetics. According to studies from scanning electron microscopy (SEM) and multiscale optical microscopy, the Zn@ZnP electrode effectively inhibits the growth of dendrites with excellent Zn plating/stripping reversibility. In consequence, the symmetric cell with the Zn@ZnP electrodes displays a long‐term cycle life of over 1260 h at 10 mA cm−2. The full cell, consisting of Zn@ZnP anodes and MnO2‐based cathode, demonstrated a high discharge capacity of 145 mAh g−1 after cycling 500 times at the current density of 1000 mA g−1. A scalable method for designing a homogeneous anode protection layer enables dendrite‐free zinc metal anodes, paving the way for interface modification of other metal anodes.
The porous ZnP matrix is in situ grown on the surface of Zn foil as the artificial protective layer. The ZnP‐protected Zn anodes exhibit excellent cycling stability without dendrite formation.
Lithium–sulfur (Li–S) batteries have been regarded as one of the most promising candidates for next-generation energy storage owing to their high energy density and low cost. However, the practical ...deployment of Li–S batteries has been largely impeded by the low conductivity of sulfur, the shuttle effect of polysulfides, and the low areal sulfur loading. Herein, we report the synthesis of uniform Co–Fe mixed metal phosphide (Co–Fe–P) nanocubes with highly interconnected-pore architecture to overcome the main bottlenecks of Li–S batteries. With the highly interconnected-pore architecture, inherently metallic conductivity, and polar characteristic, the Co–Fe–P nanocubes not only offer sufficient electrical contact to the insulating sulfur for high sulfur utilization and fast redox reaction kinetics but also provide abundant adsorption sites for trapping and catalyzing the conversion of lithium polysulfides to suppress the shuttle effect, which is verified by both the comprehensive experiments and density functional theory calculations. As a result, the sulfur-loaded Co–Fe–P (S@Co–Fe–P) nanocubes delivered a high discharge capacity of 1243 mAh g–1 at 0.1 C and excellent cycling stability for 500 cycles with an average capacity decay rate of only 0.043% per cycle at 1 C. Furthermore, the S@Co–Fe–P electrode showed a high areal capacity of 4.6 mAh cm–2 with superior stability when the sulfur loading was increased to 5.5 mg cm–2. More impressively, the prototype soft-package Li–S batteries based on S@Co–Fe–P cathodes also exhibited superior cycling stability with great flexibility, demonstrating their great potential for practical applications.
The metallic tin (Sn) anode is a promising candidate for next‐generation lithium‐ion batteries (LIBs) due to its high theoretical capacity and electrical conductivity. However, Sn suffers from severe ...mechanical degradation caused by large volume changes during lithiation/delithiation, which leads to a rapid capacity decay for LIBs application. Herein, a Cu–Sn (e.g., Cu3Sn) intermetallic coating layer (ICL) is rationally designed to stabilize Sn through a structural reconstruction mechanism. The low activity of the Cu–Sn ICL against lithiation/delithiation enables the gradual separation of the metallic Cu phase from the Cu–Sn ICL, which provides a regulatable and appropriate distribution of Cu to buffer volume change of Sn anode. Concurrently, the homogeneous distribution of the separated Sn together with Cu promotes uniform lithiation/delithiation, mitigating the internal stress. In addition, the residual rigid Cu–Sn intermetallic shows terrific mechanical integrity that resists the plastic deformation during the lithiation/delithiation. As a result, the Sn anode enhanced by the Cu–Sn ICL shows a significant improvement in cycling stability with a dramatically reduced capacity decay rate of 0.03% per cycle for 1000 cycles. The structural reconstruction mechanism in this work shines a light on new materials and structural design that can stabilize high‐performance and high‐volume‐change electrodes for rechargeable batteries and beyond.
A rigid Cu–Sn intermetallic coating layer (ICL) is designed to restrict the volume change of a Sn anode through a structural reconstruction mechanism. A gradual separation of the metallic Cu phase from the Cu–Sn ICL provides a regulated distribution of Cu to buffer the volume change and suppress the mechanical degradation of the Sn anode.
In the electrolyte containing Li+ and TBA+ (tert-n-butylammonium), the band edge movement, trap state distribution, electron recombination and electron transport in dye-sensitized solar cells (DSSCs) ...before and after TiO2 film surface coating with Yb2O3 is studied in this paper. It is found that whether surface coating could improve the performance of DSSCs depends on the compositions of the electrolytes. After surface coating, the band edge shifts negatively in the Li+ electrolyte, but no significant negative shift was observed in the TBA+ electrolyte. The changes of the trap state distribution also depend on the combined effects of the electrolytes and surface coating. In both types of electrolytes, the Yb2O3-coated TiO2 film suppresses the recombination and slows down the electron transport. These findings are important for improving the performance of the DSSC using the surface coating, which could explain the reasons why the photoelectric efficiency could not improve by coating, doping, and core−shell TiO2 in DSSCs.
The interface structure induced by electrolyte cations was found to play a significant role in determining the performance and stability of dye-sensitized solar cells. The trap state density in the ...nanostructure TiO2 electrodes was affected by the adsorbed 1,2-dimethyl-3-propylimidazolium cation (DMPI+) or alkali cations, such as Li+, Na+, K+, and Cs+, on the dyed TiO2 electrode and was found to increase with the order of decreasing cation radius DMPI+ < Cs+ < K+ < Na+ < Li+. The change in interface structure resulted from the accumulation of the adsorbed cations to increase trap states in the nanostructure TiO2 electrodes during long-term accelerated aging tests. The size effect of electrolyte cations on the cell performance suggested that the reduced surface cations, when small cations penetrated into titania lattice, resulted in a negative shift of the TiO2 conduction band edge and a weaker interaction of Li+ with dyes to obtain the decline in photocurrent and efficiency. The overall efficiency of dye-sensitized solar cells with large DMPI+ in the electrolyte retained over 110% of its initial value after 2100 h. Also, no obvious differences in the efficiency for dye-sensitized solar cells with electrolyte cations, such as Li+, Cs+, and DMPI+, were observed after 1270 h under one sun light soaking in our experiment. The results suggested that large DMPI+ chemisorbed on TiO2 surface could not intercalate into the TiO2 lattice for the enhanced stability of dye-sensitized solar cells in practical application.
As one of the most promising cathode materials for lithium-ion batteries, nickel-rich layered oxide LiNi0.83Co0.11Mn0.06O2 (NCM83) has an inherent issue with rapid capacity decay caused by phase ...change and interface side reactions during the charge/discharge cycling. Herein, an effectively synergistic strategy for improving the structural stability and electrochemical performance of NCM83 cathodes has been proposed, combining surface polymeric coating with bulk doping by the high-temperature solid-phase method. The comprehensive results demonstrate that the niobium (Nb) element can be successfully bulk-doped into the crystal lattice, which could increase the layer spacing, thus stabilizing the crystal structure and minimizing the Li+/Ni2+ mixing in the as-prepared NCM83 cathode. Meanwhile, a small amount of Nb in the form of oxide and a layer of polyaniline (PANI) was coated on the NCM83 cathode’s surface. This not only can prevent electrolyte erosion and inhibit side reactions but also can effectively improve the transport coefficient of Li+ during the charge and discharge process. The optimized NCM83 cathode exhibited outstanding discharge-specific capacity (236.79 mAh g–1 at 0.2 C rate and 215.67 mAh g–1 at 2 C rate), stable cycling performance (capacity retention of 84.4% after 100 cycles at 2 C), and excellent rate performance (150.58 mAh g–1 at 10 C) by taking advantage of the synergistic effects. The synergistic strategy using Nb doping in combination with a surface polymeric coating can enhance the fundamental understanding of the high-nickel layered oxide cathodes for lithium-ion batteries.
