Agricultural product futures are crucial to economic development, and the prediction of agricultural product futures prices has an important impact on the stability of the market economy. In order to ...improve the accuracy of agricultural product futures price prediction, based on machine learning algorithms, this study mainly uses machine learning methods to predict futures prices based on the analysis of fundamental factors affecting agricultural product futures prices. Moreover, in this study, wavelet analysis method is used to smooth the data and then build a model to process the hierarchical information after signal decomposition. In addition, this study conducts model validity studies through cases to draw comparative statistical diagrams to analyze the accuracy of model prediction data. The research shows that the model proposed in this paper has certain effects and can provide theoretical reference for subsequent related research.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, ODKLJ, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Phosphorus (P) is one of the most promising anode materials for sodium-ion batteries (SIBs) because of its high theoretical capacity upon Na storage (2590 mA h g
−1
), low sodiation potential (∼0.4 V
...vs.
Na/Na
+
) and natural abundance. Unfortunately, it suffers from huge volume variation during sodiation/desodiation processes, which can cause severe structural destruction and therefore fast performance degradation during cycling. To overcome this issue, tremendous efforts, including nanostructure engineering, composite designing and surface modification, have made to improve the structural stability to optimize the electrochemical performance. Additionally, the fabrication of phosphides is an effective way to achieve P-based anodes with long-cycle life, despite sacrificing a certain amount of capacity. Herein, we first introduce the Na storage mechanism of P-based materials and then summarize the recent advancement in the synthesis and fabrication of phosphorus-based anode materials. The fundamental scientific challenges faced by phosphorus-based electrodes are discussed, followed by a comprehensive review of effective strategies used to enhance the electrochemical properties. We have computed the theoretical sodiation potentials of possible metal phosphides by first-principles calculations, which can offer guidance for future high-performance phosphide exploration. Finally, we discuss the perspectives and challenges to enable the practical applications of P-based materials in SIB. We have attempted to provide a unique insight into this rapidly developing field and shed light on the future trends of the P-based material anodes for SIBs.
This review summarizes the recent progress in the Na storage mechanism, preparation, challenges and solutions of phosphorus-based anode materials for sodium ion batteries.
At present, some experts and scholars do not explicitly mention the static model in the analysis of the straddle strategy, which leads to the research results are not ideal. This paper unifies the ...static model and proposes a method to analyze the arbitrage opportunities in the bond market. At the same time, this paper combines image processing technology to analyze image method and improve image clarity. In addition, this paper uses the contrast method to carry out traditional static model analysis, combines the research requirements to improve the model, obtains the research data through network data collection, and constructs the model for experimental data analysis. Finally, the paper processes the model data through image processing to obtain identifiable statistical images. The research shows that the model proposed in this study has certain validity and can provide theoretical reference for subsequent related research.
A designed nanostructure with MoS2 nanosheets (NSs) perpendicularly grown on graphene sheets (MoS2/G) is achieved by a facile and scalable hydrothermal method, which involves adsorption of Mo7O24 6– ...on a graphene oxide (GO) surface, due to the electrostatic attraction, followed by in situ growth of MoS2. These results give an explicit proof that the presence of oxygen-containing groups and pH of the solution are crucial factors enabling formation of a lamellar structure with MoS2 NSs uniformly decorated on graphene sheets. The direct coupling of edge Mo of MoS2 with the oxygen from functional groups on GO (C–O–Mo bond) is proposed. The interfacial interaction of the C–O–Mo bonds can enhance electron transport rate and structural stability of the MoS2/G electrode, which is beneficial for the improvement of rate performance and long cycle life. The graphene sheets improve the electrical conductivity of the composite and, at the same time, act not only as a substrate to disperse active MoS2 NSs homogeneously but also as a buffer to accommodate the volume changes during cycling. As an anode material for lithium-ion batteries, the manufactured MoS2/G electrode manifests a stable cycling performance (1077 mAh g–1 at 100 mA g–1 after 150 cycles), excellent rate capability, and a long cycle life (907 mAh g–1 at 1000 mA g–1 after 400 cycles).
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IJS, KILJ, NUK, PNG, UL, UM
An amorphous SiO2/C composite anode material is synthesized via a sol–gel route combining with mechanical milling and post heat-treatment processes. The synthesized amorphous SiO2/C composite ...presents a nanostructure composing of amorphous SiO2 cluster and coating carbon layer. The amorphous SiO2/C electrode exhibits high reversible capacity (∼600 mA h g−1), stable cycling performance and excellent rate-capability. Mechanical milling causes SiO2/C composite amorphization which makes the active material possess good electrochemical activity. The coating carbon layer can not only increase electronic conductivity, but also accommodate part of the volume expansion occurred during discharge/charge process.
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► Amorphous SiO2/C composite was prepared via a facile route. ► SiO2/C electrode exhibits high specific capacity and stable cycling performance. ► SiO2/C electrode displays excellent rate-capability. ► Amorphous SiO2 shows higher electrochemical activity than crystalline one.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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► SiOx/C composite with nano-scale core–shell structure. ► The core SiOx is consisting of amorphous Si clusters and crystalline SiO2 domains. ► SiOx/C composite anode shows high ...specific capacity and good cycling stability.
Nano-sized SiOx/C composite with core–shell structure is prepared by a modified Stöber method. After heat-treatment, the O/Si ratio in SiOx/C composite is near 1 and the core of SiOx presents a structure composing of amorphous Si clusters and ordered SiO2 domains. SiOx/C composite anode shows high specific capacity (ca. 800mAhg−1), excellent cycling stability, good rate-capability but low initial coulombic efficiency. Li2O and Li4SiO4 may generate in the initial lithiation process, which, combining with the carbon shell, can buffer the volume change caused by the alloying of Si with Li, and thereby improving the cycling stability of electrode. The nano feature of SiOx/C particle and the electronic conductive nature of carbon coating layer ensure the good rate-capability of SiOx/C electrode.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Silicon suboxide (SiO
x
) is considered to be one of the most promising materials for next-generation anode due to its high energy density. For its preparation, the wet-chemistry method is a ...cost-effective and readily scalable route, while the so-derived SiO
x
usually shows lower capacity compared with that prepared by high temperature-vacuum evaporation route. Herein, we present an elaborate particle structure design to realize the wet-chemistry preparation of a high-performance SiO
x
/C nanocomposite. Dandelionlike highly porous SiO
x
particle coated with conformal carbon layer is designed and prepared. The highly-porous SiO
x
skeleton provides plenty specific surface for intimate contact with carbon layer to allow a deep reduction of SiO
x
to a low O/Si ratio at relatively low temperature (700 °C), enabling a high specific capacity. The abundant mesoscale voids effectively accommodate the volume variation of SiO
x
skeleton, ensuring the high structural stability of SiO
x
@C during lithiation/delithiation process. Meanwhile, the three-dimensional (3D) conformal carbon layer provides a fast electron/ion transportation, allowing an enhanced electrode reaction kinetics. Owing to the optimized O/Si ratio and well-engineered structure, the prepared SiO
x
@C electrode delivers an ultra-high capacity (1,115.8 mAh·g
−1
at 0.1 A·g
−1
after 200 cycles) and ultra-long lifespan (635 mAh·g
−1
at 2 A·g
−1
after 1,000 cycles). To the best of our knowledge, the achieved combination of ultra-high specific capacity and ultra-long cycling life is unprecedented.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
In an effort to improve the rate-capability of Li4Ti5O12 anode material, a dual-phase composite Li4Ti5O12–TiO2 is in situ prepared via a solvothermal route. The Li4Ti5O12–TiO2 composite shows higher ...reversible capacity and better rate-capability compared to single phase Li4Ti5O12. The TiO2 can decrease significantly the particle size of Li4Ti5O12–TiO2 powders due to a steric hindrance effect, which thereby shortens the lithium ion diffusion distance and enhances the electrode reaction. Meanwhile, anatase TiO2 can contribute some capacity to the Li4Ti5O12–TiO2 electrode. Coating the Li4Ti5O12–TiO2 composite with carbon (∼2.5 wt.%) can further improve the rate-capability of Li4Ti5O12–TiO2 electrode, a reversible capacity of ∼140 mA h g−1 is maintained after 100 cycles at 5 C.
► Dual-phase Li4Ti5O12–TiO2 was in situ prepared by a solvothermal route. ► TiO2 can prevent the grain growth and particle aggregation of Li4Ti5O12 phase. ► Li4Ti5O12–TiO2 powder displays high specific capacity and good cycling performance. ► Carbon coated Li4Ti5O12–TiO2 exhibits an excellent rate-capability.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Carbon coated Fe3O4 nanocomposite (Fe3O4/C) is synthesized via a simple sol–gel route and a subsequent carbon CVD process, with Fe2O3 xerogel as intermediate product. The nanoporous Fe2O3 xerogel is ...reduced to Fe3O4 during the CVD process. The prepared Fe3O4/C composite presents a well-distributed nanostructure composing of Fe3O4 nanoparticles coated with carbon layer. The electrode exhibits a stable reversible capacity of over 850 mAh g−1 at 0.1 A g−1, excellent cycling performance and good rate capability. Both of the nano-scale particle size of Fe3O4 and the carbon layer contribute to the excellent electrochemical performance of Fe3O4/C. An increase in electrode capacity with cycling is observed for the prepared Fe3O4/C composite when cycled at 50 °C, which is similar to other reported transition metal oxides. The preparation process of Fe3O4/C composite is facile, mild and productive.
•Nano-sized Fe3O4/C composite was prepared via a facile and productive route.•Fe3O4/C composite is composed of Fe3O4 nanoparticles and carbon coating layer.•Fe3O4/C electrode exhibits high specific capacity and stable cycling performance.•Fe3O4/C electrode displays good rate-capability.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
