Anodes for Li-ion batteries prepared from microcrystalline silicon and enabled by binder’s chemistry and pseudo-self-healing

Abstract

Silicon, while suffering from major degradation issues, has been recognized as a next promising material to replace currently used graphite in the anodes of Li-ion batteries. Several pathways to mitigate the capacity fading of silicon has been proposed, including optimization of the electrode composition. Within the present work we evaluated different binder formulations to improve the long-term performance of the Li-ion batteries’ anodes based on industrial grade silicon (Si) which is typically characterized by a particle sizes ranging from 100 nm to 5.5 microns. The decrease of pH in a binder formulation was found to detrimental for the cycling performance of Si due to enhanced formation of an ester-type bonding between the carboxylic group of the binder and hydroxyl group on the Si surface as well as cross-linking. Furthermore, the present work was focused on the use of the industrial grade Si with very high loading of Si material (up to 80% by weight) to better highlight the effects of the surface chemistry of Si and its influence on the performance of Si-based anodes in Li-ion batteries. The tested system allowed to establish a pseudo self-healing effect that manifests itself through the restoration of the anode capacity by approximately 25% and initiates after approximately 20 cycles. The stabilization of the capacity is attributed to self-limiting lithiation process. Such effect is closely related to SEI formation and transport properties of an electrode prepared from silicon of industrial grade.

Ultrathin Silicon Nanolayer Implanted NixSi/Ni Nanoparticles as Superlong‐Cycle Lithium‐Ion Anode Material

“…Binders also play a crucial role in maintaining the structural integrity of silicon and stabilizing the electrode–electrolyte interface. [ 18–22 ] For instance, a conductive self‐healing polymeric binder, constructed by grafting ureido–pyrimidinone (UPy)–functionalized poly(acrylic acid) with poly(ethylene glycol) (PEG) was developed using hydrogen bonding for Si. [ 19 ] Similarly, by introducing mechanically robust covalent bonding between Si nanopowder and a linear polymeric binder through an esterification reaction a stable Si anode was reported.…”

The Composition of Oxygen Functional Groups on Graphite Surfaces

“…[63] Furthermore, carboxyl and carbonyl groups improve the mechanical properties of a graphite anode as they allow binder materials to bind to the anode both covalently and through hydrogen bonding, which leads to higher adhesion to the anode. [64,65] In comparison to hydroxyl and ketonic rich surfaces, carboxyl and carbonyl rich graphite anodes possess a more superior structural integrity, leading to LIBs with higher cyclabilities. [66] The competition between the stability and cyclability of LIBs in relation to the concentration of surface carboxyl and carbonyl groups shows the importance of fine tuning the graphite anode surface structure and composition so that the trade-off between the two properties can be carefully controlled.…”

Advanced and Emerging Negative Electrodes for Li-Ion Capacitors: Pragmatism vs. Performance

“…Various examples of nanostructured Si-nanoparticles, core/shell structures, nanowires, nanotubes, and nanoporous structures-have been reported over the years to mitigate the volume expansion-caused capacity fading [77]. Binder chemistry is also of critical importance for the performance of Si-based anodes [78,79]. Another challenge of Si is its low electronic conductivity and poor Li + diffusion which affect high rate cycling; however, in LICs, Si operates in its lithiated state, partially mitigating such problems.…”