Chemical and Electrochemical Lithiation of van der Waals Tetrel-Arsenides

Lithiation of van der Waals tetrel-arsenides, GeAs and SiAs, has been investigated. Electrochemical lithiation demonstrated large initial capacities of over 950 mAh g⁻¹ accompanied by rapid fading over successive cycling in the voltage range 0.01–2 V. Limiting the voltage range to 0.5–2 V achieved more stable cycling, which was attributed to the intercalation process with lower capacities. Ex situ powder X-ray diffraction confirmed complete amorphization of the samples after lithiation, as well as recrystallization of the binary tetrel-arsenide phases after full delithiation in the voltage range 0.5–2 V. Solid-state synthetic methods produce layered phases, in which Si-As or Ge-As layers are separated by Li cations. The first layered compounds in the corresponding ternary systems were discovered, Li_0.9Ge_2.9As_3.1 and Li₃Si₇As₈, which crystallize in the Pbam (No. 55) and P2/m (No. 10) space groups, respectively. Semiconducting layered GeAs and SiAs accommodate the extra charge from Li cations through structural rearrangement in the Si-As or Ge-As layers and eventually by replacement of the tetrel dumbbells with sets of Li atoms. Ge and Si monoarsenides demonstrated high structural flexibility and a mild ability for reversible lithiation.     

Double-Shelled C@MoS2 Structures Preloaded with Sulfur: An Additive Reservoir for Stable Lithium Metal Anodes

The growth of Li dendrites hinders the practical application of lithium metal anodes (LMAs). In this work, a hollow nanostructure, based on hierarchical MoS₂ coated hollow carbon particles preloaded with sulfur (C@MoS₂/S), was designed to modify the LMA. The C@MoS₂ hollow nanostructures serve as a good scaffold for repeated Li plating/stripping. More importantly, the encapsulated sulfur could gradually release lithium polysulfides during the Li plating/stripping, acting as an effective additive to promote the formation of a mosaic solid electrolyte interphase layer embedded with crystalline hybrid lithium-based components. These two factors together effectively suppress the growth of Li dendrites. The as-modified LMA shows a high Coulombic efficiency of 98 % over 500 cycles at the current density of 1 mA cm⁻². When matched with a LiFePO₄ cathode, the assembled full cell displays a highly improved cycle life of 300 cycles, implying the feasibility of the proposed LMA.     

Micro/Nanoengineered α-Fe2O3 Nanoaggregate Conformably Enclosed by Ultrathin N-Doped Carbon Shell for Ultrastable Lithium Storage and Insight into Phase Evolution Mechanism

The Fe-based transition metal oxides are promising anode candidates for lithium storage considering their high specific capacity, low cost, and environmental compatibility. However, the poor electron/ion conductivity and significant volume stress limit their cycle and rate performances. Furthermore, the phenomena of capacity rise and sudden decay for α-Fe₂O₃ have appeared in most reports. Here, a uniform micro/nano α-Fe₂O₃ nanoaggregate conformably enclosed in an ultrathin N-doped carbon network (denoted as M/N-α-Fe₂O₃@NC) is designed. The M/N porous balls combine the merits of secondary nanoparticles to shorten the Li⁺ transportation pathways as well as alleviating volume expansion, and primary microballs to stabilize the electrode/electrolyte interface. Furthermore, the ultrathin carbon shell favors fast electron transfer and protects the electrode from electrolyte corrosion. Therefore, the M/N-α-Fe₂O₃@NC electrode delivers an excellent reversible capacity of 901 mA h g⁻¹ with capacity retention up to 94.0 % after 200 cycles at 0.2 A g⁻¹. Notably, the capacity rise does not happen during cycling. Moreover, the lithium storage mechanism is elucidated by ex situ XRD and HRTEM experiments. It is verified that the reversible phase transformation of α↔γ occurs during the first cycle, whereas only the α-Fe₂O₃ phase is reversibly transformed during subsequent cycles. This study offers a simple and scalable strategy for the practical application of high-performance Fe₂O₃ electrodes.     

Microwave Synthesized In2S3@CNTs with Excellent Properties inLithium‐Ion Battery and Electromagnetic Wave Absorption

The three‐dimensional nanoflower‐like β‐In₂S₃ composited with carbon nanotubes (CNTs) has been synthesized by a single mode microwave‐assisted hydrothermal technique. The In₂S₃ and CNTs nanocomposites (In₂S₃@CNTs) were investigated as the anode materials of lithium batteries (LIBs) and the electromagnetic wave absorption materials. For LIBs applications, the In₂S₃@CNTs nanocomposite exhibited excellent cycling stability with a high reversible charge capacity of 575 mA⋅h⋅g^–1 after 300 cycles at 0.5 A⋅g^–1. In addition, the In₂S₃@CNTs used as electromagnetic wave absorber displayed a maximum reflection loss of –42.75 dB at 11.96 GHz with a thickness of 1.55 mm.     

Polyimides as cathodic materials in lithium batteries: Effect of the chemical structure of the diamine monomer

Polyimides are being investigated as alternative, environmentally friendly and safe organic electrode materials for lithium and sodium batteries. However, further improvements need the proper chemical design of these polymers. In this paper, the effect of chemical structure of polyimides on their performance as cathodic materials in lithium batteries was investigated in detail. More in particular, we studied polyimides based on seven different diamine monomers in combination with best performing naphthalenic dianhydride monomer. The first set included the so‐called cardo diamines possessing additional redox‐active carbonyl group with the goal to enhance the theoretical capacity of the polymer. Second, several aromatic diamines including additional functionalities such as cyclic amides, anthrone, or quinolidinium groups were investigated. Finally, aliphatic diamines, containing oxyethylene moieties and thus capable to increase the ionic conductivity of the resulting polymer system, were explored. Among the different polyimides, the “cardo” one based on naphthalenic dianhydride and aromatic aniline phthalein with an additional carbonyl group showed the best results in terms of battery performance. Such polyimide was capable to deliver up to 130 mAhg⁻¹ specific capacity (87% of the theoretical value) at 25 °C and at a current density of 250 mAg⁻¹ during 100 charge/discharge cycles. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 714–723     

Enrichment of Lithium,Potassium, Copper,and Uranium Isotopes by Electromigration in a Cation Exchange Membrane

The ion exchange membrane can be used as an effective medium of electromigration for the separation of isotopes by the following reasons.     

锂离子进入碳纳米管端口速度的分子动力学模拟

锂离子进入碳纳米管端口的速度V Li是影响锂离子电池充电性能的重要因素.采用分子动力学模拟方法,研究了直径、温度、电场强度和端口改性官能团四种因子对其影响.运用正交实验方法,分析得出了各因子及其不同水平的影响规律.结果表明,四种因子的影响力度由大到小依次为:电场强度、官能团类型、碳纳米管直径和温度.在本文的模拟条件下,随着电场强度和碳纳米管直径的增大,V Li逐渐增加,且在电场强度下的增幅会更显著;碳纳米管端口官能团分别改性为氢原子(—H),羟基(—OH),氨基(—NH2)以及羧基(—COOH)时,V Li会逐步降低;随着温度的增大,V Li先增加后减小,但整体波动偏幅不大.     

Electrospun‐Technology‐Derived High‐Performance Electrochemical Energy Storage Devices

Electrospinning, as a novel nontextile filament technology, is an important method to prepare continuous nanofibers and has shown its remarkable advantages, such as a broadly applicable material system, controllable fiber size and structure, and simple process. Electrospun nanofiber membranes prepared by electrospinning have shown promising applications in many fields, such as supercapacitors, lithium‐ion batteries, and sodium‐ion batteries, owing to their large specific surface area and adjustable network pore structure. The principle of electrospinning and key points relevant to its usage in the preparation of high‐performance electrochemical energy storage materials are reviewed herein based on recent publications, particularly focusing on research progress of relative materials. Also, this review describes a distinctive conclusion and perspective on the future challenges and opportunities in electrospun nanomaterials.     

NMR and FT-IR Investigation of Spinel LiMn2O4 Cathode Prepared by the Tartaric Acid Gel Process

The structure of the lithium manganese tartrate precursor and the synthesis mechanism of LiMn₂O₄ were investigated by FT-IR, NMR, TG/DSC, and XRD in this study. The results of FT-IR and ⁷Li and ¹³C NMR measurements revealed that lithium ions bond with carboxylic acid ligands and the O–H stretching modes of tartaric acid. Manganese ion bonds only with carboxylic acid. Lithium and manganese ions were trapped homogeneously on an atomic scale throughout the precursor. Such a structure eliminates the need for long-range diffusion during the formation of lithium manganese oxides. Therefore, spinel LiMn₂O₄ was synthesized at temperatures as low as 300°C. In this work, the electrochemical properties of Li/Li_xMn₂O₄ were studied. It is clear that the discharge curves exhibit two pseudo plateaus as the LiMn₂O₄ is fired to higher temperatures. The discharge capacity of LiMn₂O₄ increases from 84 to 117 mAh/g as the calcination temperature increases from 300 to 500°C. The LiMn₂O₄ powders calcined at low temperatures with a high specific surface area and an average valence of manganese exhibit a better cycle life.