In-situ synthesis of interconnected SWCNT/OMC framework on silicon nanoparticles for high performance lithium-ion batteries

AbstractIn spite of silicon has a superior theoretical capacity, the large volume expansion of Si anodes during Li+ insertion/extraction is the bottle neck that results in fast capacity fading and poor cycling performance. In this paper, we report a silicon, single-walled carbon nanotube, and ordered mesoporous carbon nanocomposite synthesized by an evaporation-induced self-assembly process, in which silicon nanoparticles and single-walled carbon nanotubes were added into the phenolic resol with F-127 for co-condensation. The ordered mesoporous carbon matrix and single-walled carbon nanotubes network could effectively accommodate the volume change of silicon nanoparticles, and the ordered mesoporous structure could also provide efficient channels for the fast transport of Li-ions. As a consequence, this hybrid material exhibits a reversible capacity of 861 mAh g−1 after 150 cycles at a current density of 400 mA g−1. It achieves significant improvement in the electrochemical performance when compared with the raw materials and Si nanoparticle anodes

Geometries and Electronic States of Divacancy Defect in Finite-Size Hexagonal Graphene Flakes

The geometries and electronic properties of divacancies with two kinds of structures were investigated by the first-principles (U) B3LYP/STO-3G and self-consistent-charge density-functional tight-binding (SCC-DFTB) method. Different from the reported understanding of these properties of divacancy in graphene and carbon nanotubes, it was found that the ground state of the divacancy with 585 configurations is closed shell singlet state and much more stable than the 555777 configurations in the smaller graphene flakes, which is preferred to triplet state. But when the sizes of the graphene become larger, the 555777 defects will be more stable. In addition, the spin density properties of the both configurations are studied in this paper

Theoretical Study on Cyclopeptides as the Nanocarriers for Li+, Na+, K+ and F−, Cl−, Br−

The interaction process between a series of cyclopeptide compounds cyclo(Gly)n  (n=4,6,8) and monovalent ions (Li+, Na+, K+, F−, Cl−, and Br−) was studied using theoretical calculation. The mechanism of combination between the cyclo(Gly)n and ions was discussed through binding energy, Mulliken electron population, and hydrogen bond. It was found that for the same cyclopeptide the binding energy has the order of cyclo(Gly)n–Li+ > cyclo(Gly)n–Na+ > cyclo(Gly)n–K+ and cyclo(Gly)n–F− > cyclo(Gly)n–Br− > cyclo(Gly)n–Cl−. The binding energy manifests the stable complex of cyclo(Gly)n and ions can be formed, and the different energy shows the potential use of cyclo(Gly)n as nanocarriers for metal ions or the extractant for ions separation

Progress and future prospects of high-voltage and high-safety electrolytes in advanced lithium batteries: From liquid to solid electrolytes

Developing the next-generation high-energy density and safe batteries is of prime importance to meet the emerging demands in electronics, automobile industries and various energy storage systems. High-voltage lithium-ion batteries (LIBs) and solid-state batteries (SSBs) are two main directions attracting increasing interest in recent years, due to their potential applications in the near future. In both kinds of batteries, the electrolytes play a pivotal role but also create several bottleneck problems. In this review, recent progress in designing electrolytes for high-voltage LIBs and SSBs is summarized. First, the solvents, additives, ionic liquids and superconcentrated salts strategies for constructing high-voltage liquid electrolytes are reviewed, and then the applications of inorganic solids, solid polymers, gels and ionic liquids in solid-state electrolytes are presented. Finally, the general design rules of the electrolytes and their current limitations and future prospects are briefly discussed

Recent advances in two-dimensional nanomaterials-based electrochemical sensors for environmental analysis

With the rapidly increased concerns in environmental pollution, there have been urgent needs to develop fast, sensitive, low-cost and multiplexed sensing devices for the detection of environmental pollutants. Two-dimensional (2D) nanomaterials hold great promise due to their unique chemical and physical properties, which have been extensively employed to monitor the environmental pollutants combined with different detection techniques. In this review, we summarize recent advances in 2D nanomaterials-based electrochemical sensors for detecting heavy metal ions, organic compounds, pesticides, antibiotics and bacteria. We also discuss perspectives and challenges of 2D nanomaterials in environmental monitoring. Keywords: Two dimensional, Nanomaterials, Electrochemical sensor, Environmental monitorin

Functional polyethylene glycol-based solid electrolytes with enhanced interfacial compatibility for room-temperature lithium metal batteries dagger

The interface issues of electrodes/solid-state electrolytes have been limiting the application of room-temperature lithium metal batteries. In situ polymerization technology achieved the realization of solid-solid ultra-conformal interface contacts. However, few efforts have been directed toward the precursor compatibility of electrodes and simultaneous chemical/electrochemical performances, which may directly cause high interface impedance, severe lithium dendrites and unsatisfactory stability of assembled cells. In this work, high-performance polyethylene glycol-based solid electrolytes with enhanced interfacial compatibility was prepared by an in situ copolymerization of functional polyethylene glycol and vinylene carbonate, in which vinylene carbonate tends to preferentially produce poly(vinylene carbonate) via anionic polymerization within solid electrolyte interface layers on the lithium metal surface to stabilize Li metal, and copolymerization with polyethylene glycol improves overall electrochemical performances. The SPE-assembled Li-Li symmetrical batteries stably run for over 2000 h; meanwhile, SPEs exhibit a high room-temperature ionic conductivity (0.4 mS cm(-1)), high lithium ion transference number (0.46) and wide electrochemical stability window (5.1 V). Resultant LiFePO4/Li metal batteries show a considerable rate capability (up to 5C) and a super-long cycling performance (>300 cycles) at 1C at room temperature. In addition, assembled cells with high-loading cathodes (5.5-10.5 mg cm(-2)) deliver high initial capacities and good capacity retentions. The simple and scalable approach may enable the industrialization and application of room-temperature lithium metal batteries

Mussel-inspired polydopamine treated Si/C electrode as high-performance anode for lithium-ion batteries

In this paper, we report a mussel-inspired polydopamine coating on the Si/C electrode via a simple immersion process to improve the electrochemical performance such as cycle stability and rate capability. The nanometer-thick polydopamine coating layer enables fast Li+ transport at the interfaces and takes part in the formation of SEI due to the electron-rich amine group. The PD coated Si/C electrode exhibits good performance in long cycling test. Compare with the uncoated Si/C electrode, the capacity retention of the coated electrode is improved from 59.5% to 80% after 200 cycles. X-ray photoelectron spectroscopy, transmission electron microscopy and scanning electron microscopy prove that PD coating really promotes the formation of uniform and dense SEI and reduces cracks on the electrode surface. Meanwhile, the pulverization of electrodes which breaks the electrical contact with the current collector is alleviated. (C) 2020 Elsevier B.V. All rights reserved

Self-shutdown function induced by sandwich-like gel polymer electrolytes for high safety lithium metal batteries

Lithium-ion batteries using either liquid electrolytes or solid electrolytes have been extensively studied in recent years, but both of these encounter safety risks such as flammability of liquid electrolytes and uncontrolled dendrite growth. In this study, a sandwich gel polymer electrolyte (SGPE) with a thermal shutdown function was developed to resolve the safety issues. By adjustment of surface pore size of the SGPE, lithium dendrite growth is suppressed. Due to the sandwich structure design, the SGPE can effectively respond to an overheating environment, regulate lithium ion transport and inhibit the penetration of lithium dendrite, demonstrating a remarkably high safety of the batteries, especially at high temperature or under thermal runaway circumstances. In addition, the LiFePO4/SGPE/Li battery exhibits a high reversible capacity of 135 mA h g(-1) at 1C and maintains high capacity retention (>95%) after 200 charge-discharge cycles. This study shows a great advantage to handle thermal abuse and a stable lithium anode, suggesting a promising approach to the high safety lithium metal batteries

Novel ionic liquid based electrolyte for double layer capacitors with enhanced high potential stability

Developing electrolyte with high electrochemical stability is the most effective way to improve the energy density of double layer capacitors (DLCs), and ionic liquid is a promising choice. Herein, a novel ionic liquid based high potential electrolyte with a stabilizer, succinonitrile, was proposed to improve the high potential stability of the DLC. The electrolyte with 7.5 wt% succinonitrile added has a high ionic conductivity of 41.1 mS cm(-1) under ambient temperature, and the DLC adopting this electrolyte could be charged to 3.0 V with stable cycle ability even under a discharge current density of 6 A g(-1). Moreover, the energy density could be increased by 23.4% when the DLC was charged to 3.0 V compared to that charged to 2.7 V