Porous Si coated with S-doped carbon as anode material for lithium ion batteries

A novel porous Si/S-doped carbon composite was prepared by a magnesiothermic reaction of mesoporous SiO2, subsequently coating with a sulfur-containing polymer-poly(3,4-ethylene dioxythiophene), and a post-carbonization process. The as-prepared Si composite was homogeneously coated with disordered S-doped carbon with 2.6 wt.% S in the composite and retained a high surface area of 58.8 m(2) g(-1). The Si/S-doped carbon composite exhibited superior electrochemical performance and long cycle life as an anode material in lithium ion cells, showing a stable reversible capacity of 450 mAh g(-1) even at a high current rate of 6,000 mA g(-1)

Mechanistically informed data-driven modeling of cyclic plasticity via artificial neural networks

A mechanistically informed data-driven approach is proposed to simulate the complex plastic behavior of microstructured/homogenized solids subjected to cyclic loading, especially to simulate the Masing effect. Our proposed approach avoids the complicated mathematical construction of an appropriate yield surface, and does not require a large amount of data for training, by virtue of its mechanistic character, which couples the methods and tools of data science to the principles of mechanics. Specifically, a data-processing method is herein advanced to extract specific internal variables that characterize cyclic plastic behavior, which cannot be measured directly via physical experiments. A yield surface, represented by an artificial neural network (ANN), is then trained by stress–strain data and the extracted internal variables. Finally, the ANN is integrated into a finite element computational framework to solve different boundary value problems (BVPs). Results for demonstrative examples are presented, which illustrate the effectiveness and the reliability of the proposed approach for solids containing voids and particles in their microstructure. Compared with direct numerical simulation (DNS), our approach seems to predict the average levels of stress and plastic strain under cyclic loading more efficiently, as well as the regions of strain localization. In addition, results for a homogenized three-dimensional truss structure demonstrate that our approach can accurately describe the evolution of key internal variables. Our mechanistic approach requires much less data than the general pure data-driven methods, which shows a possible computational efficiency compared with the pure data-driven approach. Limitations of our proposed approach are also discussed

Nanostructured silicon/porous carbon spherical composite as a high capacity anode for Li-ion batteries

A nanostructured silicon/porous carbon spherical composite was prepared by a simple hydrothermal method using glucose as a carbon source and Pluronic F127 as a soft template/pore forming agent in the presence of silicon nanoparticles, and a subsequent carbonization process. In this composite, silicon nanoparticles were individually and separately coated with a porous carbon shell with a thickness of 15-20 nm and a pore size of 3-5 nm. The composite electrode exhibited excellent cycling stability and rate capability, delivering a stable capacity of 1607 mA h g(-1) at a current density of 0.4 A g(-1) after 100 cycles, and a reversible capacity of 1050 mA h g(-1) even at a high current density of 10 A g(-1). Detailed analysis of cyclic voltammetry and electrochemical impedance spectroscopy revealed that the composite showed favorable electrochemical kinetics due to the nano-sized porous carbon shell, which facilitated the formation of a solid electrolyte interface film and the transportation of Li ions and electrons, and decreased the charge transfer resistance, thus significantly improving the electrochemical performance compared with the bare nano-Si electrode

Novel core-shell structured Si/S-doped-carbon composite with buffering voids as high performance anode for Li-ion batteries

A novel core-shell structured Si/S-doped-carbon composite with buffering voids (Si/v-SC), was prepared by a facile hydrothermal method using glucose as carbon source and simultaneously chemical polymerization of 3,4-ethylenedioxythiophene (EDOT) in the presence of Si@SiO2 nanoparticles, and followed by carbonization and removal of the SiO2 layer. The results showed that the Si nanoparticles were embedded in the S-doped-carbon buffer space to form a core-shell structure. Compared to the Si/carbon composite (Si/v-C) without S-doping in carbon layer, the Si/v-SC composite electrode showed improved cycling and rate performance, exhibiting a reversible capacity of 664 mA h g(-1) over 300 cycles at the current of 0.4 A g(-1) and a high capacity of 537 mA h g(-1) even at 10 A g(-1). The effects of S-doping on the properties of carbon material were further investigated. XRD and Raman test revealed that the S-doping increased the interspace of carbon crystal face, and improved the amorphous structure of carbon and thus the initial coulombic efficiency

triethoxysilanewitholigoethyleneoxidesubstituentasfilmformingadditiveforgraphiteanode

{3-2-(2-methoxyethoxy) ethoxy-propyl} triethoxysilane (TESM2) was synthesized and used as an electrolyte additive to improve the performances of lithium-ion batteries (LIBs). The electrochemical properties of the electrolyte (1 mol/L lithium hexafluorophosphate (LiPF _6)/ethylene carbonate (EC):diethylene carbonate (DEC):dimethyl carbonate (DMC), 1:1:1) with different contents of TESM2 were characterized by ionic conductivity measurement, galvanostatic charge/discharge test of graphite/Li half cells, and electrochemical impedance spectroscopy. Both the cycling performances and C-rate capabilities of graphite/Li half cells were significantly improved with an optimized content of 15% TESM2 in the electrolyte. The graphite/Li half cell delivered a very high specific capacity of 370 mAh/g at 0.2C rate without any capacity loss for 60 cycles, and retained a capacity of 292 mAh/g at 2C rate. The solid electrolyte interphase (SEI) film on the surface of the graphite anode was investigated by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), indicating that TESM2 was effectively involved in the formation of SEI film on the surface of graphite

Nano-structured composite of Si/(S-doped-carbon nanowire network) as anode material for lithium-ion batteries

Novel nanostructured silicon composites, Si/Poly(3,4-ethylenedioxythiophene) nanowire network (Si/PNW) and Si/(S-doped-carbon nanowire network) (Si/S-CNW), are prepared by a soft-template polymerization of 3,4-ethylenedioxythiophene (EDOT) using sodium dodecyl sulfate (SDS) as surfactant with the presence of Si nanoparticles and a subsequent carbonization of Si/PNW, respectively. The presence of Si nanoparticles in the soft-template polymerization of EDOT plays a critical role in the formation of PEDOT nanowire network instead of 1D nanowire. After the carbonization of PEDOT, the S-doped-carbon nanowire network matrix shows higher electrical conductivity than PNW counterpart, which facilitates to construct robust conductive bridges between Si nanoparticles and provide large electrode/electrolyte interfaces for rapid charge transfer reactions. Thus, Si/S-CNW composite exhibits excellent cycling stability and rate capability as anode material, retaining a specific capacity of 820 mAh g(-1) after 400 cycles with a very small capacity fade of 0.09% per cycle. (C) 2015 Elsevier B.V. All rights reserved

Micro/nano-structured SnS2 negative electrodes using chitosan derivatives as water-soluble binders for Li-ion batteries

Micro/nano-structured SnS2 was prepared by a hydrothermal method using biomolecular l-cysteine and SnCl4 center dot 5H(2)O as sulfur source and tin source, respectively. The electrochemical performances of SnS2 electrodes were investigated using water-soluble binders of carboxymethyl chitosan (C-chitosan) and chitosan lactate, and compared with the conventional water-soluble sodium carboxymethyl cellulose (CMC) and non-aqueous polyvinylidene difluoride (PVDF). SnS2 electrode using the water-soluble binders (C-chitosan, chitosan lactate, and CMC) showed higher initial coulombic efficiency, larger reversible capacity, and better rate capabilities than that of PVDF. In addition, SnS2 electrode using C-chitosan binder exhibited somewhat worse cycling stability, but better rate capability at a high rate of 5C than CMC

Allyl cyanide as a new functional additive in propylene carbonate-based electrolyte for lithium-ion batteries

Allyl cyanide (AC) was investigated as a film-forming additive in propylene carbonate (PC)-based electrolytes for graphite anode in lithium-ion batteries. The film-forming behavior of AC was characterized with cyclic voltammetry, electrochemical impedance spectroscopy, scanning electron microscopy, and Fourier transform infrared spectroscopy. By adding 2 wt% AC in the electrolyte of 1 M LiPF6-PC/DMC (1:1, in vol), the exfoliation of graphite anode was effectively suppressed over cycling. Graphite/Li half-cell showed an initial coulombic efficiency of 75 % and a specific capacity of 300 mAh/g after 48 cycles. A possible reductive polymerization mechanism of AC on the surface of graphite was proposed

Facile synthesis of nanostructured Li4Ti5O12/PEDOT:PSS composite as anode material for lithium-ion batteries

A poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) coated Li4Ti5O12 (LTO/PP) composite is synthesized by a facile and convenient approach, which involves dispersing LTO in an aqueous solution of PEDOT: PSS, followed by rotary evaporation accompanied by an ultrasonic procedure. After the coating process, LTO is covered by a homogeneous PEDOT: PSS layer, which effectively improves the electrical conductivity and processing capability of LTO to form a more homogeneous electrode sheet, and thus impart more favorable electrochemical kinetics as compared with the pristine LTO electrode. The LTO/PP electrode exhibits better reversible capacity and rate capability compared with the LTO electrode, delivering a reversible capacity of 177.2 mA h g(-1) at 0.1C and reaching a capacity of 169.1 mA h g(-1) with a capacity retention of 97.8% after 100 cycles at 0.5C. At the rate of 10C, the LTO/PP electrode delivers a capacity as high as 161.1 mA h g(-1) (91.0% of the value achieved at 0.1C), as compared to 144.5 mA h g(-1) for the pristine LTO electrode

A novel MoS2/C nanocomposite as an anode material for lithium-ion batteries

A novel molybdenum disulfide/carbon (MoS2/C) nanocomposite is synthesized by a simple hydrothermal method using glucose as a carbon source and Pluronic F127 as promoting agent in presence of MoS2 nanoparticles and followed by carbonization. Pluronic F127 is used as an essential agent which inhibits the spontaneous formation of carbon microspheres during the hydrothermal reaction. The composite electrode exhibits excellent cycling stability and rate capability, delivering a reversible capacity of 882.6 mA h g(-1) at a current density of 50 mA g(-1) and a capacity retention of 82.8% after 100 cycles at a current density of 100 mA g(-1). At a higher current density of 300/500 mA g(-1), it still retains a capacity of 603.6/461.6 mA h g(-1) respectively, as compared to 295.6/228.4 mA h g(-1) for the pristine MoS2 electrode. The composite shows favorable electrochemical kinetics compared with pristine MoS2 due to the incorporation of homogenous conductive carbon layer and its nanostructured morphology. (C) 2017 Elsevier B.V. All rights reserved