Silicon Anodes In Lithium-ion Batteries Research Articles

Multifunctional molecular design as an efficient polymeric binder for silicon anodes in lithium-ion batteries.

This work demonstrates the design, synthesis, characterization, and study of the electrochemical performance of a novel binder for silicon (Si) anodes in lithium-ion batteries (LIBs). Polymeric binders with three different functional groups, namely, carboxylic acid (COOH), carboxylate (COO(-)), and hydroxyl (OH), in a single polymer backbone have been synthesized and characterized via (1)H NMR and FTIR spectroscopies. A systematic study that involved varying the ratio of the functional groups indicated that a material with an acid-to-alcohol molar ratio of 60:40 showed promise as an efficient binder with an initial columbic efficiency of 89%. This exceptional performance is attributed to the strong adhesion of the binder to the silicon surface and to cross-linking between carboxyl and hydroxyl functional groups, which minimize the disintegration of the Si anode structure during the large volume expansion of the lithiated Si nanoparticle. Polymers with multiple functional groups can serve as practical alternative binders for the Si anodes of LIBs, resulting in higher capacities with less capacity fade.

3D Visualization of Inhomogeneous Multi-Layered Structure and Young’s Modulus of SEI on Silicon Anode for Lithium-Ion Batteries

3D visualization of inhomogeneous multi-layered structure and Young’s Modulus of SEI on silicon anode for lithium-ion batteriesJieyun Zheng, Hao Zheng, Fei Luo, Wenjun Li and Hong Li*Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, ChinaCorrespond to hli@iphy.ac.cnIntroductionSolid Electrolyte interphase (SEI) grown on electrode surface in non-aqueous lithium batteries was firstly purposed by Peled in 1979.1 Grate efforts have been paid since then to explore the chemical composition, structure and formation mechanism of SEI during cycling. Many techniques such as X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), transmission electronic microscopy (TEM), second ion mass spectroscopy (SIMS), electrochemical impedance spectroscopy (EIS), mass spectroscopy (MS) and thermo gravimetric-differential scanning calorie (TG-DSC) have been used to get a complete picture of SEI. It is generally accepted that the SEI is layer-structured with inorganic part such as Li2CO3, Li2O, LiF covers the electrode first and followed by the organic part such as LiCH3, LiOCO2CH3 and LiOCH3 covers the first layer. However, profound understanding of micro-structure of the SEI still remains a challenge. A particular example is silicon which is a promising high capacity anode for the next generation lithium batteries but it suffers from large volume variation and continuous formation/destruction of unstable SEI film. Herein, an atomic force microscopy (AFM) based method2 is developed which can directly and three-dimensionally (3D) visualize the multi-layered structure and mechanical properties of the SEI formed on silicon anode materials. We, thus, propose a novel mechanism of the dynamic process of the SEI formation on the silicon anode accordingly.Based on force curve method, a cross-section 3D image of the SEI film on silicon thin film anode can be provided. Single-layered, double-layered, and multi-layered structures with various Young’s Modulus and thickness coexist at different sites on the surface of silicon. The SEI layers with higher Young’s modulus have higher probability to appear at the bottom layer. The total coverage without additive in the electrolyte of the SEI is only about 50% even when the electrode in a half cell was discharged to 0.005 V vs Li+/Li and kept potentialstatistically for 48 hours.Our recent investigations on formation process, electrochemical stability, layered structure and coverage, mechanical properties, influences of temperatures, additives, impurity on the SEI, will be introduced in this meeting. Acknowledge:Financial support from CAS project (KJCX2-YW-W26), "Strategic Priority Research Program" of the Chinese Academy of Sciences，Grant No. XDA09010102 and National project 973 (2012CB932900) are appreciated.Reference: [1] E. Peled, J. Electrochem. Soc. 1979, 126, 2047[2] J. Zhang, R. Wang, X. Yang, W. Lu, X. Wu, X. Wang, H. Li, L. Chen, Nano letters 2012, 12, 2153

N-doped graphitic self-encapsulation for high performance silicon anodes in lithium-ion batteries

N-doped sites at CNT and graphene trigger spontaneous encapsulation of Si particles by simple pH control at room temperature. Significantly, N-doped CNT encapsulated Si composite electrode materials show remarkable cycle life and rate performance in battery operations. Superior capacity retention of 79.4% is obtained after 200 cycles and excellent rate capability of 914 mA h g−1 is observed at a 10 C rate.

Improving the performance of silicon anode in lithium-ion batteries by Cu2O coating layer

The influence of a 200 nm Cu2O coating layer on the electrochemical performance of an 800 nm Si thin-film anode was investigated by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge/discharge measurements. The electrochemical performance of the Si thin-film anode was improved by the coating layer. The coated Si anode exhibited higher values of conductivity in comparison with the pristine Si anode. Scanning electron microscopy images of the anodes after cycling test showed that the coated Si anode after cycling test had less cracks than the pristine Si anode. The galvanostatic charge/discharge measurements reveal that the cyclability and rate capability of the coated Si thin-film anode were better than the pristine Si thin-film anode.

Towards High-Capacity Silicon Anodes for Lithium-Ion Batteries: Comparative Performance Study of Commercially Available Polymer Binders and Silicon Nanopowders

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A three-dimensional graphene scaffold supported thin film silicon anode for lithium-ion batteries

Three-dimensional (3D) silicon (Si) thin films supported on a graphene scaffold were prepared as an anode electrode for lithium-ion batteries. The as-prepared Si anode exhibited a gravimetric capacity as high as 1560 mA h g−1 at a current density of 797 mA g−1 and a capacity retention of 84% after 500 cycles relative to the capacity value in the 50th cycle. Meanwhile, specific capacities of 1083 and 803 mA h g−1 were demonstrated after 1200 cycles at 2390 mA g−1 and 7170 mA g−1, respectively. The high specific capacity and excellent cyclability and rate performance could be ascribed to the highly porous 3D architecture of the graphene scaffold, which possesses good electrical conductivity and the feature of mechanical flexibility. The results presented here pave a new way for synthesis of Si–graphene hybrid materials using microwave plasma-enhanced chemical vapor deposition as robust and scalable Si-based anodes for lithium ion batteries.

Effect of modified elastomeric binders on the electrochemical properties of silicon anodes for lithium-ion batteries

Silicon has been investigated intensively as a promising anode material for rechargeable lithium-ion batteries. The choice of a binder is very important to solve the problem of the large capacity fade observed along cycling. The effect of modified elastomeric binders on the electrochemical performance of crystalline nano-silicon powders was studied. Compared with the conventional binder (polyvinylidene fluoride (PVDF)), Si electrodes using the elastomeric styrene butadiene rubber (SBR) and sodium carboxymethyl cellulose (SCMC) combined binder show an improved cycling performance. The reversible capacity of the Si electrode with the SCMC/SBR binder is as high as 2221 mA·h/g for 30 cycles in a voltage window between 0.005 and 2 V. The structure changes from SEM images of the silicon electrodes with different binders were used to explore the property improvement.

Micromechanisms of Capacity Fade in Silicon Anode for Lithium-Ion Batteries

Large volume change and associated stress generation is known to cause failure of the silicon thin film anode used for Lithium-ion batteries after a few cycles. Experimental observations suggest that plastic deformation of the underlying Cu substrate and degradation of the active/inactive interface are the primary reasons responsible for the capacity fade. The goal of the present study is to examine the interplay between these mechanisms using a computational mechanics approach. In the present study, a novel multi-physics finite element framework has been developed to simulate the lithiation and de-lithiation induced failure of amorphous Si (a-Si) thin film on Cu foil. The numerical framework is based on the finite deformation of the active silicon wherein diffusion of lithium occurs, plastic deformation of the Cu foil, and debonding of the active/inactive interface. The effect of substrate property, interfacial energy and kinetics of interface degradation has been examined.

Progression of Solid Electrolyte Interphase Formation on Hydrogenated Amorphous Silicon Anodes for Lithium-Ion Batteries

Silicon anodes based on an alloy reaction with lithium have a large theoretical specific capacity making them an appealing candidate for use in lithium-ion batteries. A major factor influencing the power cyclability and cycle life of the battery is the formation of the solid electrolyte interphase (SEI) layer. In this work, the progression of SEI formation on hydrogenated amorphous Si (a-Si:H) anodes is determined as a function of applied electrochemical potential during the first charging cycle by combining cyclic voltammetry measurements with detailed surface chemical analysis. During this first lithiation cycle, the SEI layer begins to form at 1.8 V by decomposition of the LiPF6 electrolyte to LiF, LixPFy, and PFy. The SEI layer, with LiF as the major species, continues to form upon further charging and forms a nonuniform layer on the surface of the electrode. At 0.4 V the Li atoms begin to penetrate the a-Si:H network, and upon full charging at 0.0 V, the anode itself is comprised in part by Si–Li, Si...

Modified Solid Electrolyte Interphase of Silicon Nanowire Anodes for Lithium-Ion Batteries

Solid electrolyte interphase (SEI) plays a significant role in maintaining reversible capacities by protecting silicon anodes of lithium-ion batteries from chemical reactions with electrolyte and mechanical failures. In this work, silicon nanowires were functionalized and applied as anode material for lithium-ion batteries to study the effects of modified SEI via surface functionalization. The results from cyclicvoltammetry, charge/discharge and SEI characterizations (XPS, FTIR, and AFM) showed that by modifying the silicon surface the capacity retention varied significantly within 15 consecutive cycles; electrochemically and chemically grafted monolayer prevent silicon from reaction with electrolyte, while impedes lithium insertion so as to compromise lithium storage in silicon; by introducing coupling agent, such as trimethoxymethylsilane to form Si-O-Si cross-linking, the anode capacity retention was greatly improved by forming a chemically and mechanically stable SEI on silicon.

Porous Silicon Anode for Lithium-Ion Batteries, Prepared by Electrodeposition onto Virus Enabled 3-D Current Collector

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Carbon scaffold structured silicon anodes for lithium-ion batteries

A unique methodology of fabricating Si anodes for lithium-ion batteries with porous carbon scaffold structure is reported. Such carbon scaffold Si anodes are fabricated via carbonization of porous Si-PVdF precursors which are directly deposited on the current collector. Unlike the conventional slurry casting method, binder and conductive additives are not used in the preparation of the carbon scaffold Si anodes. The carbon scaffold Si anode has a close-knit porous carbon structure that can not only accommodate the Si volume change, but also facilitate the charge transfer reaction. These advantages are demonstrated by the superior capacity, cycle stability and rate performance of the carbon scaffold Si anodes.

The Influence of Fluorinated Aromatic Isocyanates on the Cycling Performance of Silicon Anodes in Lithium-Ion Batteries

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