The critical role of titanium cation in the enhanced performance of P2-Na0.5Ni0.25Mn0.60Ti0.15O2 cathode material for sodium-ion batteries.

Tremendous effort has been devoted to develop durable electrode materials for sodium ion batteries. This work focuses on enhancing the reversibility of a cathode material Na0.5Ni0.25Mn0.75O2 by adopting the titanium cation doping strategy. The obtained P2-Na0.5Ni0.25Mn0.60Ti0.15O2 material shows smooth charge-discharge curves upon suppressing the Na+/vacancy ordering effect via the partial substitution of Mn4+ for Ti4+, and enhanced cycling performance. It exhibits a reversible capacity of 138 mA h g-1 at 0.5C, as well as a high rate capacity of 81 mA h g-1 at 5C between a cut-off voltage of 2 and 4 V, while long-term cycling stability is demonstrated with a capacity retention of 84% over 200 cycles. An enhanced cycling stability is also observed when the voltage is between 2 and 4.2 V. The feasibility of constructing a symmetrical Na-ion full cell with Na0.5Ni0.25Mn0.60Ti0.15O2 as cathode and anode electrodes is also demonstrated. The titanium cation doping results in reduced charge transfer impedance and an enhanced sodium cation diffusion coefficient, thus suggesting an efficient strategy to obtain a durable cathode material for sodium ion batteries.

[Prediction models of soil organic matter based on spectral curve in the upstream of Heihe basin].

Benefiting from the high spectral resolution, ground hyperspectral remote sensing technology can express the ground surface feature in detail, meanwhile, multispectral remote sensing has more advantages in studying the features in a large space time region, because of its long time-series images and wide coverage. Investigating the prediction models between the soil organic matter (SOM) content and the hyperspectral data and the sensitive bands based on different indices mathematically obtained from reflectance could combine the advantages of both kinds of spectral data, and provide a new method to search the spatio-temporal characteristics of SOM. Two hundred twenty three soil samples were chosen from the upper reaches of Heihe Basin to measure the SOM content and hyperspectral curve. Taking 181 of them, the stepwise linear regression methods were used to establish models between the SOM and five indices, including reflectance (lambda), reciprocal (REC), logarithm of the reciprocal (LR), continuum-removal (CR) and the first derivative reflectance (FDR). After then, the left 42 samples were used for model validation: firstly, the best model of the same index was chosen by the values of Pearson correlation coefficient (r) and Root mean squared error (RMSE) between the measured value and predicted value; secondly, the best models of different indices were compared. As a result, the model built by reflectance has a better estimation of SOM with the r: 0.863 and RMSE: 4.79. And the sensitive bands of the reflectance model contain 474 nm during TM1, 636 nm during TM3 and 1 632 nm during TM5. This result could be a reference for the retrieval of SOM content of the upper reaches by using the TM remote sensing data.

Copper and Zirconium Codoped O3-Type Sodium Iron and Manganese Oxide as the Cobalt/Nickel-Free High-Capacity and Air-Stable Cathode for Sodium-Ion Batteries.

Considering the abundance of iron and manganese within the Earth's crust, the cathode O3-NaFe0.5Mn0.5O2 has shown great potential for large-scale energy storage. Following the strategy of introducing specific heteroelements to optimize the structural stability for energy storage, the work has obtained an O3-type NaFe0.4Mn0.49Cu0.1Zr0.01O2 that exhibits enhanced electrochemical performance and air stability. It displays an initial reversible capacity of 147.5 mAh g-1 at 0.1C between 2 and 4.1 V, a capacity retention ratio exceeding 69.6% after 100 cycles at 0.2C, and a discharge capacity of 70.8 mAh g-1 at a high rate of 5C, which is superior to that of O3-NaFe0.5Mn0.5O2. The codoping of Cu/Zr reserves the layered O3 structure and enlarges the interlayer spacing, promoting the diffusion of Na+. In addition, the structural stability and air stability observed by Cu-doping is well maintained via the incorporation of extra Zr favoring a highly reversible phase conversion process. Thus, this work has demonstrated an efficient strategy for developing cobalt/nickel-free high-capacity and air-stable cathodes for sodium-ion batteries.

Low-Strain Reticular Sodium Manganese Oxide as an Ultrastable Cathode for Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) are recognized as attractive alternatives for grid-scale electrochemical energy storage applications. Transition metal oxide cathodes represent one of the most dynamic materials for industrialization among the various cathodes for SIBs. Here, a cation-doped cathode Na0.44Mn0.89Ti0.11O2 with a tunnel structure is introduced, which undergoes a lowered volume change of only 5.26% during the Na+ insertion/extraction process. Moreover, the average Na+ diffusion coefficients are enhanced by more than 3-fold upon the doping of the Ti cation. The obtained cathode delivers a practically usable capacity of 119 mAh g-1 at 0.1 C as well as an enhanced discharge capacity of 96 mAh g-1 at 5 C. Durability is demonstrated by the retained 71 mAh g-1 after 1000 cycles, corresponding to a capacity retention of 74%. This work demonstrates that the reticular Na0.44Mn0.89Ti0.11O2 is a promising ultrastable cathode material for the development of long-life sodium-ion batteries.

[Land layout for lake tourism based on ecological restraint].

To avoid the decrease and deterioration of lake wetlands and the other ecological issues such as lake water pollution that were caused by the unreasonable exploration of lake tourism, a land layout for the tourism development of Liangzi Lake with the priority of ecological security pattern was proposed, based on the minimal cumulative resistance model and by using GIS technology. The study area was divided into four ecological function zones, i. e., core protection zone, ecological buffer zone, ecotone zone, and human activity zone. The core protection zone was the landscape region of ecological source. In the protection zone, new tourism land was forbidden to be increased, and some of the existing fundamental tourism facilities should be removed while some of them should be upgraded. The ecological buffer zone was the landscape region with resistance value ranged from 0 to 4562. In the buffer zone, expansion of tourism land should be forbidden, the existing tourism land should be downsized, and human activities should be isolated from ecological source by converting the human environment to the natural environment as far as possible. The ecotone zone was the landscape region with resistance value ranged from 4562 to 30797. In this zone, the existing tourism land was distributed in patches, tourism land could be expanded properly, and the lake forestry ecological tourism should be developed widely. The human activity zone was the landscape region with resistance value ranged from 30797 to 97334, which would be the key area for the land layout of lake tourism. It was suggested that the land layout for tourism with the priority of landscape ecological security pattern would be the best choice for the lake sustainable development.

Separation of low concentration of cesium ion from wastewater by electrochemically switched ion exchange method: experimental adsorption kinetics analysis.

A series of experiments were performed to evaluate the continuous separation of cesium based on an electrochemically switched ion exchange (ESIX) process using a diaphragm-isolated reactor with two identical nickel hexacyanoferrate/porous three-dimensional carbon felt (NiHCF/PTCF) electrodes as working electrodes. The effects of applied potential, initial concentrations and pH values of the simulation solutions on the adsorption of cesium ion were investigated. The adsorption rate of cesium ion in the ESIX process was fitted by a pseudo-first-order reaction model. The experiments revealed that the introduction of applied potential on the electrodes greatly enhanced the adsorption/desorption rate of Cs(+) and increased the separation efficiency. H(3)O(+) was found to play a dual role of electrolyte and competitor, and the adsorption rate constant showed a curve diversification with an increase in pH value. Also, it was found that the electrochemically switched adsorption process of Cs(+) by NiHCF/PTCF electrodes proceeded in two main steps, i.e., an ESIX step with a fast adsorption rate and an ion diffusion step with a slow diffusion rate. Meanwhile, the NiHCF/PTCF film electrode showed adsorption selectivity for Cs(+) in preference to Na(+).