Slightly Fluorination of Al₂O₃ ALD Coating on Li₁.₂Mn₀.₅₄Coo.₁₃Ni₀.₁₃O₂ Electrodes: Interface Reaction to Create Stable Solid Permeable Interphase Layer

Improving the performance of cathodes by using surface coatings has proven to be an effective method for improving the stability of Li-ion batteries (LIBs), while a high-quality film satisfying all requirements of electrochemical inertia, chemical stability, and lithium ion conductivity has not been found. In this study, a composite film composed of Al2O3 and AlF3 layers was coated on the surface of Li1.2Mn0.54Co0.13Ni0.13O2 (Li-rich NMC) based electrodes by atomic layer deposition (ALD). By varying the ratio of Al2O3 and AlF3, an optimal coating was achieved. The electrochemical characterization results indicated that the coating with 1 cycle of AlF3 ALD on 5 cycles of Al2O3 ALD (1AlF3-5Al2O3) significantly improved the cycling stability and alleviated the voltage attenuation problem of Li-rich NMC based electrodes by suppressing side reactions between the electrolyte and electrode, as well as inhibiting the transformation of layered Li2MnO3 into a spinel-like phase. After 200 cycles of charge-discharge, the discharge capacity retention of LIB half cells based on 1AlF3-5Al2O3 coated Li-rich NMC electrodes kept at 84%, much higher than that of the uncoated Li-rich NMC (the capacity retention less than 20%)

Ultra-Thin Coating and Three-Dimensional Electrode Structures to Boosted Thick Electrode Lithium-Ion Battery Performance

This paper reports a multiscale controlled three‐dimensional (3D) electrode structure to boost the battery performance for thick electrode batteries with LiMn1.5Ni0.5O4 as cathode material, which exhibits a high areal capacity (3.5 mAh/cm2) along with a high specific capacity (130 mAh/g). This excellent battery performance is achieved by a new concept of cell electrode fabrication, which simultaneously controls the electrode structure in a multiscale manner to address the key challenges of the material. Particles with ultrathin conformal coating layers are prepared through atomic layer deposition followed by a nanoscale‐controlled, thermal diffusion doping. The particles are organized into a macroscale‐controlled 3D hybrid‐structure. This synergistic control of nano‐/macro‐structures is a promising concept for enhancing battery performance and its cycle life. The nanoscale coating/doping provides enhanced fundamental properties, including transport and structural properties, while the mesoscale control can provide a better network of the nanostructured elements by decreasing the diffusion path between. Electrochemical tests have shown that the synergistically controlled electrode exhibits the best performance among non‐controlled and selectively‐controlled samples, in terms of specific capacity, areal capacity, and cycle life

The role of sampling strategy on apparent temporal stability of soil moisture under subtropical hydroclimatic conditions

Financial support for this research was provided through the joint China-UK Red Soil Critical Zone project funded by the National Natural Science Foundation of China (NSFC: 41771263; 41571130053) and the United Kingdom Natural Environment Research Council (NE/N007611/1). Additional funding was provided by the “135 innovation project” from the Chinese Academy of Sciences (CAS:ISSASIP1648). Special thanks go to the staff of the Ecological Experimental Station of Red Soil of the Institute of Soil Science of CAS.Peer reviewedPublisher PD

Improving Soil Heat Flux Accuracy with the Philip Correction Technique

Soil heat flux Gs is an important component of the surface energy balance. Soil heat flux plates (SHFPs) are widely used to measure Gs, although several errors are known to occur. The Philip correction has been applied to minimize errors in Gs measured by SHFPs (Gp) if the soil thermal conductivity λs, SHFP thermal conductivity λp, and plate geometry function H are known. The objective of this study is to evaluate the effectiveness of the Philip correction for a variety of SHFPs. The λp were determined without thermal contact resistance and differed from the manufacturer-specified λp. A simplified H formulation was similar to or less than the full H equation for different SHFP shapes. The G ratio (Gp/Gs) was sensitive to λs/λp and H when they were relatively small. Compared with the Gs determined by a gradient method (Gs_grad), the Gpmeasured under a full corn (Zea mays, L.) canopy in the field underestimated Gs by 38%–62%. After applying the Philip correction, almost all Gp agreed better with Gs_grad. Generally, the Gp corrected with measured plate parameters agreed better with Gs_grad than those corrected with manufacturer-specified values. The Gp corrected with the simplified and full H expression differed for different SHFPs. These results indicate that SHFPs always underestimate Gs and that the performance of the Philip correction is affected by λp, plate dimensions, and H. An alternative method to measure Gs by a three-needle heat-pulse sensor or a gradient method, in which soil temperature and water content are measured at several depths, is recommended

Air-void-affected zone in concrete beam under four-point bending fracture

A series of numerical simulations were performed on prenotched four-point bending (FPB) concrete beams containing air voids of different sizes and locations by using the finite element method combined with the cohesive crack model. The void-affected zone was proposed for characterizing the effect of a void on a fracture, and its size was determined by moving an air void horizontally until the crack path changed. As a function of air void location and size, the dimensionless affected-zone radius was fitted according to the numerical results. Finally, the fracture processes of the pre-notched FPB concrete beams with randomly distributed voids were simulated numerically, and the affected-zone radius was used to explain the choice of crack paths to verify the prediction. It was found that the prediction is accurate for an isolated affected zone and is roughly approximate for an overlapped one

Higher atmospheric CO2 levels favour C3 plants over C4 plants in utilizing ammonium as a nitrogen source

Photosynthesis of wheat and maize declined when grown with NH4+ as a nitrogen (N) source at ambient CO2 concentration compared to those grown with a mixture of NO3– and NH4+, or NO3– as the sole N source. Interestingly, these N nutritional physiological responses changed when the atmospheric CO2 concentration increases. We studied the photosynthetic responses of wheat and maize growing with various N forms at three levels of growth CO2 levels. Hydroponic experiments were carried out using a C3 plant (wheat, Triticum aestivum L. cv. Chuanmai 58) and a C4 plant (maize, Zea mays L. cv. Zhongdan 808) given three types of N nutrition: sole NO3– (NN), sole NH4+ (AN) and a mixture of both NO3– and NH4+ (Mix-N). The test plants were grown using custom-built chambers where a continuous and desired atmospheric CO2 (Ca) concentration could be maintained: 280 μmol mol–1 (representing the pre-Industrial Revolution CO2 concentration of the 18th century), 400 μmol mol–1 (present level) and 550 μmol mol–1 (representing the anticipated futuristic concentration in 2050). Under AN, the decrease in net photosynthetic rate (Pn) was attributed to a reduction in the maximum RuBP-regeneration rate, which then caused reductions in the maximum Rubisco-carboxylation rates for both species. Decreases in electron transport rate, reduction of electron flux to the photosynthetic carbon [Je(PCR)] and electron flux for photorespiratory carbon oxidation [Je(PCO)] were also observed under AN for both species. However, the intercellular (Ci) and chloroplast (Cc) CO2 concentration increased with increasing atmospheric CO2 in C3 wheat but not in C4 maize, leading to a higher Je(PCR)/ Je(PCO) ratio. Interestingly, the reduction of Pn under AN was relieved in wheat through higher CO2 levels, but that was not the case in maize. In conclusion, elevating atmospheric CO2 concentration increased Ci and Cc in wheat, but not in maize, with enhanced electron fluxes towards photosynthesis, rather than photorespiration, thereby relieving the inhibition of photosynthesis under AN. Our results contributed to a better understanding of NH4+ involvement in N nutrition of crops growing under different levels of CO2