镁离子电池正极材料研究进展

镁离子电池(MIBs)因镁资源储量丰富、体积能量密度大、金属镁空气中相对稳定等优势,被认为是具有大规模储能应用潜力的电池体系。然而,镁离子较高的电荷密度和较强的溶剂化作用导致其在正极材料中的可逆脱嵌和固-液界面上的离子扩散相当缓慢,严重影响了MIBs的电化学性能。近年来,人们针对MIBs正极材料开展了大量工作,取得了一定进展,但是还存在不少问题。本文先从MIBs体系的特点出发,阐述其优势和目前所面临的主要挑战,然后从无机正极材料和有机正极材料两方面展开,梳理并总结了各类正极材料的局限性及其解决策略,对优化方法和材料性能间的相关性进行归纳和讨论,为今后进一步发展具有优异电化学性能的MIBs正极材料提供可能的参考。

Selective electrocatalytic CO2 reduction enabled by SnO2 nanoclusters

The development of high-performance electrocatalysts holds the decisive key to the electrochemical CO2 reduction toward value-added products. Formic acid or formate is a desirable reduction product, but its selective production is often challenging. Tin based-materials have attracted great attention for formate production, and yet their performances are far from satisfactory. In this study, we reported the preparation of SnO2 nanoclusters from the controlled self-polymerization of dopamine together with SnO32-, followed by the mild-temperature calcination. The final product consisted of large primary particles that were further made of small secondary SnO2 nanocrystals. When evaluated as the electrocatalyst for CO2 reduction in 0.5 M NaHCO3, our material exhibited impressive activity, selectivity and stability for the selective CO2 reduction to formate. A peak formate Faradaic efficiency of^73% and large partial current density of 16.3 mA/cm2 was achieved at -0.92 V versus reversible hydrogen electrode.

Recent advances in modification strategies of silicon-based lithiumion batteries

As potential alternatives to graphite,silicon(Si)and silicon oxides(SiO_(x))received a lot of attention as anode materials for lithiumion batteries owing to their relatively low working potentials,high theoretical specific capacities,and abundant resources.However,the commercialization of Si-based anodes is greatly hindered by their massive volume expansion,low conductivity,unstable solid electrolyte interface(SEI),and low initial Coulombic efficiency(ICE).Continuous endeavors have been devoted to overcoming these challenges to achieve practical usage.This review is centered on the major challenges and latest developments in the modification strategies of Si-based anodes,including structure optimization,surface/interface regulation,novel binders,and innovative design of electrolyte.Finally,outlooks and perspectives of Si-based anodes for future development are presented.

Cobalt atoms dispersed on hierarchical carbon nitride support as the cathode electrocatalyst for high-performance lithium-polysulfide batteries

Lithium-sulfur batteries are promising candidates for next-generation energy storage but are confronted with several challenges. One of the possible solutions is to design proper cathode electrocatalysts to accelerate the redox interconversion of solvated polysulfide intermediates. Herein, we report cobalt atoms dispersed on hierarchical carbon nitride support as an effective cathode electrocatalyst for lithium-polysulfide batteries. The electrocatalyst material is prepared from the simple reaction between melamine and cyanuric acid in the presence of Co^2+, followed by the Ar annealing. The product has a unique hierarchical structure consisting of many thin and porous C3 N4 nanosheets finely dispersed with Co atoms. The atomic dispersion of Co species is confirmed by X-ray absorption experiments.Electrochemical measurements reveal that it can promote the interconversion of polysulfides. As a result,batteries using this cathode electrocatalyst achieve large capacity($1400 mAh/g at 1.6 mA/cm^2), good rate performance($800 mAh/g at 12.8 mA/cm^2) and impressive cycling stability under different current densities and different sulfur loadings.

Interlayer-expanded MoS2 assemblies for enhanced electrochemical storage of potassium ions

Potassium-ion batteries are regarded as the low-cost alternative to lithium-ion batteries.However,their development is hampered by the lack of suitable electrode materials.In this work,we demonstrate that MoS2 with expanded interlayers represents a promising candidate for the electrochemical storage of potassium ions.Hierarchical interlayer-expanded MoS2 assemblies supported on carbon nanotubes are prepared via a straightforward solution method.The increased interlayer spacing not only enables the better accommodation of foreign ions,but also lowers the diffusion energy barrier and improves diffusion kinetics of ions.When investigated as the anode material of potassium ion batteries,our interlayer-expanded MoS2 assemblies exhibit an excellent electrochemical performance with large capacity(up to∼520 mAhg^−1),good rate capability(∼310 mAhg^−1 at 1,000 mAg^−1)and impressive cycling stability,superior to most competitors.

银行业涉诉资产评估案例

随着经济的发展,现阶段经济下行压力加剧,企业间的债务纠纷增多,以涉诉资产的处置拍卖为评估目的的评估项目逐渐增多。本案例研究描述了评估机构在银行业小股权涉诉评估的实务操作,列示了在实际的评估业务中,对于银行业企业价值评估可能遇到的困难和限制。同时,展现了在面对这些评估局限时,资产评估机构如何根据资产评估准则和指南指引的规范和要求以及自身评估的经验,采用合理的评估方法,选取合适的评估参数,克服评估业务中存在的问题,评估出较为准确的银行业涉诉股权的价值。