RESUMO
High-capacity anode materials (e.g., Si) are highly needed for high energy density battery systems, but they usually suffer from low initial coulombic efficiency (CE), short cycle life, and low-rate capability caused by large volume changes during the charge and discharge process. Here, a novel dendrimer-based binder for boosting the electrochemical performance of Si anodes is developed. The polyamidoamine (PMM) dendrimer not only can be used as binder, but also can be utilized as a crosslinker to construct 3D polyacrylic acid (PAA)-PMM composite binder for high-performance Si microparticles anodes. Benefiting from maximum interface interaction, strong average peeling force, and high elastic recovery rate of PAA-PMM composite, the Si electrode based on PAA-PMM achieves a high specific capacity of 3590 mAh g-1 with an initial CE of 91.12%, long-term cycle stability with 69.80% retention over 200 cycles, and outstanding rate capability (1534.8 mAh g-1 at 3000 mA g-1 ). This work opens a new avenue to use dendrimer chemistry for the development of high-performance binders for high-capacity anode materials.
RESUMO
The introduction of 'defects' to the thermoset crosslinking network is one of the most applicable strategies for improving the modulus and toughness simultaneously. However, the reinforcement effect disappears when the 'defects' proportion exceeds the threshold. The speculated mechanism was that the aggregation and entanglement of the 'defects' chains changed the matrix topology, making the stacking structure more compact. However, the 'defects' are hardly directly observed in the experiment. As the result, the relationship between the 'defects' proportion and the package state of the matrix, and the effect on the material's mechanical performance was not explored. Herein, the network of bisphenol-A diglycidyl (DGEBA) with diethyltoluenediamine (DETDA) as the hardener was constructed using MD simulation, and n-butylamine was decorated on the matrix by replacing a proportion of DETDA acting as the 'defects'. The results indicated that the aliphatic chains aggregated and entangled at a low concentration, occupying the voids in the rigid aromatic crosslinking structure, thus lowering the free volume. The strong non-bonding interactions drew the matrix segments close together, thus reinforcing the resin. However, the microphases formed by the aliphatic chains no longer filled the voids but created a new free volume and loosened the network when the content increased, which reduced the mechanical performance of the material. The experimental results were consistent with the findings in the simulations. The moduli of the resin increased with the increase in the n-butylamine content first and then declined. The maximum moduli of the thermosets was 3.4 GPa in S30, which was about 25% higher compared with the control; the corresponding elongation at break was 8.9%, which was about 46% improved compared with the control.
RESUMO
To clarify the effects of tillage with mulching on potato yield and soil water and heat characteristics, we conducted a field experiment for two consecutive years in arid region of southern Ningxia. The results showed that tillage depths and mulching materials had significant impacts on soil water storage at 0-100 cm layer during the potato sowing period. The interactive effects of tillage depths and mulching materials were not significant. In 2019, the highest soil water storage was obtained in the subsoiling 30 cm with plastic film mulching, while soil water storage under the subsoiling 40 cm with straw mulch was the highest in 2020. Subsoiling 30 cm with plastic film mul-ching and subsoiling 40 cm with straw mulch significantly increased soil water storage by 16.9% and 33.4% compared with the plowing 15 cm with no mulch (CK), respectively. Tillage depths and mulching materials significantly affected soil water storage in the key growth period of potato. Among the tillage systems, the straw mulching plots and plastic film mulching plots had the strongest effect of soil water conservation. Irrespective of the mulching materials, soil water storage was significantly improved in the subsoiling 30-40 cm plots. Mulching materials and the interaction between tillage depths and mulching materials significantly affected soil effective accumulated temperature at 0-25 cm soil layer after sowing to budding. Among the tillage systems, the plastic film mulching plots significantly increased the average soil effective accumulated temperature by 9.3%, whereas the straw mulching plots significantly reduced the temperature by 18.7%, in comparison with no mulching plots. The highest soil effective accumulated temperature during the whole growth period was obtained in the subsoiling 30 cm with plastic film mulching and subsoiling 40 cm with plastic film mulching treatments in 2019 and 2020. The highest potato tuber yield and economic benefit in 2019 were found in the subsoiling 30 cm with straw mulching treatment, respectively, being 84.6% and 107.9% higher than CK. In 2020, the improvement effect of subsoiling 40 cm with straw mulch on potato tuber yield and economic benefit was the strongest, respectively, which were significantly increased by 81.7% and 105.7%, compared with CK. Tillage depths and mulching materials had significant interactive effects on the water and heat use efficiency of crop. The higher water use efficiency was obtained in the subsoiling 30-40 cm with straw mulch treatments, whereas the accumulated temperature use efficiency was increased significantly under different tillage depths with straw mulching treatments compared with CK. Soil water and effective accumulated temperature during the tuber formation stage were the main factors affecting potato total yield, with stronger effect of soil water than that of soil effective accumulated temperature. Therefore, the treatments of subsoiling 30-40 cm with straw mulch could improve soil moisture and heat condition, and realize potato yield and income increase and efficient use of water and heat resources, which have application and popularization value in dryland potato cultivation of southern Ningxia.
