Effects of the Formulations of Silicon‐Based Composite Anodes on their Mechanical, Storage, and Electrochemical Properties

Abstract

In this work, the effects of the formulation of silicon-based composite anodes on their mechanical, storage, and electrochemical properties were investigated. The electrode formulation was changed through the use of hydrogenated or modified (through the covalent attachment of a binding additive such as polyacrylic acid) silicon and acetylene black or graphene sheets as conducting additives. A composite anode with a covalently grafted binder had the highest elongation without breakages and strong adhesion to the current collector. These mechanical properties depend significantly on the conductive carbon additive used and the use of graphene sheets instead of acetylene black can improve elongation and adhesion significantly. After 180 days of storage under ambient conditions, the electronic conductivity and discharge capacity of the modified silicon electrode showed much smaller decreases in these properties than those of the hydrogenated silicon composite electrode, indicating that the modification can result in passivation and a constant composition of the active material. Moreover, the composite Si anode has a high packing density. Consequently, thin-film electrodes with very high material loadings can be prepared without decreased electrochemical performance.

High areal capacity battery electrodes enabled by segregated nanotube networks

“…To demonstrate that high C/A can be achieved using SNCs, we produced sets of 2 m Table 3−5). [9][10][11][24][25][26][27][28][29] The disconnection of silicon from the electrode due to crack-formation is a known capacityloss mechanism in Si-based LiBs. 30 These extremely thick electrodes are relatively stable ( Fig.…”

Structural Lithium-Ion Battery Cathodes and Anodes Based on Branched Aramid Nanofibers

“…The superior mechanical performance of the Si coated on CNT fabric is attributed to the CNT fabric that provides structural support, whereas the performance of the Si/CS-GA is attributed to the CS-GA cross-linkers that strongly bind with Si. Graphite/PVDF/AB (commercial anode), PU/Cu/Si, rGO/NC/Si, and Si/PAA/AB demonstrated inferior mechanical performance with comparable electrochemical properties to our Si anodes. The relatively low electrochemical performance of our structural anodes may be attributed to the low Si content compared to most of the literature reports and the higher C-rate used for testing (0.6 C vs 0.04–0.1 C for the literature data, as shown in Table S4).…”

“…Finally, we compared the energy storage and mechanical performance of our structural anodes with others from the literature in an Ashby plot of the tensile strength vs the Young’s modulus vs the capacity after prolonged cycling (Figure f and Table S4). Our Si anodes were compared against graphite/PVDF/AB (88.8:8:3.2, wt/wt, as the commercial anode), polyurethane (PU)/Cu/Si (12:79.7:8.3, wt/wt), Si coated on CNT fabric (47:53, wt/wt), rGO/nanocellulose (NC)/68 wt % Si, Si/PAA/AB (78:2:20, wt/wt), and Si/chitosan cross-linked with glutaraldehyde (CS-GA)/CB (60:20:20, wt/wt) . Overall, our anodes demonstrated intermediate mechanical performance with relatively lower capacity values.…”

“…In addition, free-standing structural silicon-based electrodes are challenging to fabricate and typically suffer from brittle behavior. Only a handful of studies on mechanically strong Si-based anodes have been reported. − Si nanoparticle/poly­(acrylic acid) (PAA)/acetylene black (AC) composite electrodes exhibited capacity values of 2500 mAh/g Si at 0.09 C with a low tensile strength of 12 MPa and a Young’s modulus of 1.1 GPa . Further improvement in the mechanical performance of the Si-based anodes is necessary for integration in structural applications.…”

An Overview on Protecting Metal Anodes with Alloy‐Type Coating

“…However, important volume changes during the lithiation and delithiation process limit the cycle life [36–39] . Significant improvements have been made through the formulation of the electrode in order to mitigate this issue, and long‐life cycling has been reported for lithium‐ and sodium‐based systems [40,41] . Nevertheless, alloy‐type elements are not mature for commercial rechargeable LIB, and even though silicon is under the spotlights, its use is limited to being an additive in graphite‐based negative electrodes to increase the capacity [37,42] …”