Performance Of Silicon Anodes Research Articles

Investigation of the Different Structures of Xanthan Gum on the Performance of Silicon Anodes in Lithium-ion batteries

It has been proved that bio-based binders play an important role in improving the electrochemical performance of silicon (Si) anodes in lithium-ion batteries (LIBs), so the effects by their molecular structure need further investigation. In this paper, we choose xanthan gums (XGs) with eight different structures (XG-00, XG-A0, XG-AA, XG-00, XG-0P, XG-AP, XdM-A, XdM-0) as the binders of silicon anodes in LIBs, and the samples have been tested to explore that which structure of XGs is the most beneficial to the electrochemical performance of the Si anodes. Subsequently, the Si anodes with eight XGs were characterized by SEM and FT-IR. It is concluded that due to the acetylation of terminal mannose and internal mannose residues, the structure of XG can be stabilized, contributing to the material property. The XG binder with the structures of XG-A0 and XdM-A exhibits excellent cycle stability in the electrochemical performance. After cycling tests at a current density of 420 mA/g, the capacities were maintained at 1824.7 mAh/g & 1680.7 mAh/g (100 cycles), and 1294.6 mAh/g & 1364.4 mAh/g (300 cycles), respectively. Therefore, XG-A0 and XdM-A have the potential to become high-performance binders for Si anodes in LIBs.

Tuning PAA-Based Binders Towards Optimized Performance for Silicon Anode in Lithium-Ion Batteries

Poly(acrylic acid) (PAA) based binders have been widely used for silicon anodes in lithium-ion batteries to mitigate the issues caused by reversible volumetric expansion of silicon nanoparticles during lithiation/delithiation process. However, the performance of silicon anodes using PAA-based binders is still far from meeting the requirement of practical applications and the factors affecting the performance of these binders are not fully understood. Neutralization of PAA binders using LiOH is a common strategy for processing silicon anodes in lithium-ion batteries. In our previous studies, lithiated PAA solutions showed significant increased viscosity compared to straight PAA ones, which could benefit the large-scale lamination process and enable the fabrication of mechanically robust electrodes. However, lithiated PAA binders suffer more capacity loss in cycling tests due to the weakened adhesion and more severe side reaction of silicon particles that are mostly related to the increase of pH value of the binder solutions. In this work, non-lithium bases (e.g., NBu4OH, NH4OH, and Et3N) were used to neutralize and tune the viscosity of PAA solution. The resulting modified PAA binder solutions achieved desired viscosity with less increase of pH value. Notably, electrodes made with PAA-NH4 binder showed improved cell performance than electrodes made with PAA-Li binder. Despite the pH difference between PAA and PAA-Li binder solutions, the solvation behavior of the binders could also affect cycling performance. Therefore, a series of PAA solutions were prepared and investigated by small-angle X-ray scattering. The radius of gyration (Rg) of the binders were found to be significantly different depends on lithiation and the choice of solvent. Electrodes made with these binder solutions were evaluated in half cells to explore the relationship between solvation and performance of binders.

Effect of Morphologically Different Conductive Agents on the Performance of Silicon Anode in Lithium‐Ion Batteries

AbstractThe performance of electrochemical electrodes, is largely dependent on the extent of efficient electrical contacts between particles, and secondly, between the current collector and the particles, amongst other factors. We report on the electrical conductivity of silicon anode electrodes that have been prepared by using conductive agents with different morphological properties. Super P® Li (SP), VGCF®‐H vapor grown carbon fibers (VGCF), and their mixture were incorporated separately into the anode electrode to observe their distinctive resultant performance. The morphological characterization was done using scanning electron microscopy whilst the electrochemical properties of the prepared electrodes were characterized by electrical resistivity test, cyclic voltammetry, charge/discharge tests and electrochemical impedance spectroscopy. The combination of VGCF®‐H and Super P® Li, results in improved performance of the anode, due to their synergistic interactions which reduce the effects encountered during the failure of the silicon anode electrode caused by large volume changes. These findings unlock new opportunities for the exploration and development of other morphologically useful conductive agents to improve silicon anode in lithium ion batteries.

Toward Silicon Anodes for Next-Generation Lithium Ion Batteries: A Comparative Performance Study of Various Polymer Binders and Silicon Nanopowders

Silicon is widely regarded as one of the most promising anode materials for lithium ion and next-generation lithium batteries because of its high theoretical specific capacity. However, major issues arise from the large volume changes during alloying with lithium. In recent years, much effort has been spent on preparing nanostructured silicon and optimizing various aspects of material processing with the goal of preserving the electrode integrity upon lithiation/delithiation. The performance of silicon anodes is known to depend on a large number of parameters and, thus, the general definition of a "standard" is virtually impossible. In this work, we conduct a comparative performance study of silicon anode tapes prepared from commercially available materials while using both a well-defined electrode configuration and cycling method. Our results demonstrate that the polymer binder has a profound effect on the cell performance. Furthermore, we show that key parameters such as specific capacity, capacity retention, rate capability, and so forth can be strongly affected by the choice of silicon material, polymer binder and electrolyte system - even the formation of metastable crystalline Li15Si4 is found to depend on the electrode composition and low potential exposure time. Overall, the use of either poly(acrylic acid) with a viscosity-average molecular weight of 450.000 or poly(vinyl alcohol) Selvol 425 in combination with both silicon nanopowder containing a native oxide surface layer of ∼1 nm in diameter and with a monofluoroethylene carbonate-based electrolyte led to improved cycling stability at high loadings.

Effect of ethanol-assisted electrode fabrication on the performance of silicon anodes

The performance of high-silicon-content anodes was tested as a function of silicon particle-size (44 μm, 1.8 μm and 70–100 nm), surface pre-treatment and solvent chosen for anode preparation. Two simple procedures, leading to significant improvements in electrode performance are reported. First, pre-treatment of nano-Si in ethanol which unexpectedly yields functionalised surfaces improving cycling stability. Second, the use of a 30:70 solution of ethanol and water to dissolve the CMC-binder for the electrode preparation boosts specific battery capacity. Ethanol pre-treatment of nano-Si also resulted in improved adhesion of the electrode to the current collector as well as in de-agglomeration of nano-Si powder. All these treatments improved capacity stability during cycling. Changes in surface chemistry of nano-Si before and after ethanol treatment have been analysed by XPS. A stable capacity of about 1630 mAh g −1 was obtained after 25 cycles for an electrode containing 80% silicon using ethanol during electrode coating preparation.