Tea-derived carbon materials as anode for high-performance sodium ion batteries

Sodium-ion batteries(SIB) have attracted widespread attention in large-scale energy storage fields owing to the abundant reserve in the earth and similar properties of sodium to lithium. Biomass-based carbon materials with low-cost, controllable structure, simple processing technology, and environmental friendliness tick almost all the right boxes as one of the promising anode materials for SIB. Herein, we present a simple novel strategy involving tea tomenta biomass-derived carbon anode with enhanced interlayer carbon distance(0.44 nm) and high performance, which is constructed by N,P co-doped hard carbon(Tea-1100-NP) derived from tea tomenta. The prepared Tea-1100-NP composite could deliver a high reversible capacity(326.1 m Ah/g at 28 m A/g), high initial coulombic efficiency(ICE = 90% at 28 m A/g),stable cycle life(262.4 m Ah/g at 280 m A/g for 100 cycles), and superior rate performance(224.5 m Ah/g at 1400 m A/g). Experimental results show that the excellent electrochemical performance of Tea-1100-NP due to the high number of active N,P-containing groups, and disordered amorphous structures provide ample active sites and increase the conductivity, meanwhile, large amounts of microporous shorten the Na+diffusion distance as well as quicken ion transport. This work provides a new type of N,P co-doped high-performance tomenta-derived carbon, which may also greatly promote the commercial application of SIB.

NaHCO_(3)-induced porous PbI_(2) enabling efficient and stable perovskite solar cells

Driven by their many unique features,perovskite solar cells(PSCs)have become one of the most promising candidates in the photovoltaic field.Two-step preparation of perovskite film is advantageous for its higher stability and reproducibility compared to the one-step method,which is more suitable for practical application.However,the incomplete conversion of the dense lead iodide(PbI_(2))layer during the sequential spin-coating of formamidinium/methylammonium(FA^(+)/MA^(+))organic amine salts severely affect the performance of PSCs.Herein,sodium bicarbonate(NaHCO_(3))is used to induce the formation of porous PbI_(2),which facilitates the penetration of the FA^(+)/MA^(+)ions and the formation of a perovskite film with high crystallinity and large grain microstructure.Meanwhile,the introduction of Na^(+)not only improves the energetic alignment of the PSC,but also increases the conductivity via p-doping.As a result,the optimized NaHCO_(3)-modified PSC achieves a champion power conversion efficiency of 24.0% with suppressed hysteresis.Moreover,the significant reduction in defect density and ion migration as well as a mild alkaline environment enhance the stability of device.The unencapsulated NaHCO_(3)-modified PSCs maintain over 90% of their original efficiency upon storage in ambient air(30%–40% relative humidity)for 2160 h.We have demonstrated an ingenious strategy for controlling the quality of perovskite and improving the performance of device by low-temperature foaming of simple inorganic molecules of NaHCO_(3).

Identification of differential brain regions in MCI progression via clustering-evolutionary weighted SVM ensemble algorithm

Mild cognitive impairment(MCI)as the potential sign of serious cognitive decline could be divided into two stages,i.e.,late MCI(LMCI)and early MCI(EMCI).Although the different cognitive states in the MCI progression have been clinically defined,effective and accurate identification of differences in neuroimaging data between these stages still needs to be further studied.In this paper,a new method of clustering-evolutionary weighted support vector machine ensemble(CEWSVME)is presented to investigate the alterations from cognitively normal(CN)to EMCI to LMCI.The CEWSVME mainly includes two steps.The first step is to build multiple SVM classifiers by randomly selecting samples and features.The second step is to introduce the idea of clustering evolution to eliminate inefficient and highly similar SVMs,thereby improving the final classification performances.Additionally,we extracted the optimal features to detect the differential brain regions in MCI progression,and confirmed that these differential brain regions changed dynamically with the development of MCI.More exactly,this study found that some brain regions only have durative effects on MCI progression,such as parahippocampal gyrus,posterior cingulate gyrus and amygdala,while the superior temporal gyrus and the middle temporal gyrus have periodic effects on the progression.Our work contributes to understanding the pathogenesis of MCI and provide the guidance for its timely diagnosis.