Lattice Distortion of Current Collector upon Supporting Dimensional Changes of Electrode-Active Materials in Alkali-Metal-Ion Batteries

Abstract

A current collector, which connects the electrode-active material electronically to the external circuit, is a critical component of an alkali-metal-ion battery. However, it is the least investigated component, especially toward any damage done upon supporting dimensional changes of electrode-active materials during alkali-metal-ion insertion/removal. Against this backdrop, orientation imaging microscopy, together with kernel average misorientation analysis, presents strong evidence toward the occurrence of lattice distortion/deformation, increases of local misorientation, and geometrically necessary dislocations of Cu current collector, in significant terms, upon supporting electrochemical lithiation/delithiation of Si. Creation of such lattice defects also decreases the electronic conductivity of the current collector, thus interfering with its main function. All of the above logically contribute to instability and capacity fade of the electrode. Interestingly, the presence of a graphene-based interlayer between a-Si and Cu suppresses the above damages, thus contributing to the improvement in cyclic stability by protecting not only the active material but also the current collector.

Revealing Na-segregation at the Si/Graphene Interface and Its Implications toward the Na-storage Behavior of Si-Based Electrodes

“…The most commonly cited reasons for improvement in the cyclic stability of alloying reaction-based anode materials for Na-ion/Li-ion battery systems in the presence of graphene-based additives/interlayers is the suppression of stress-induced degradation upon alkali metal-ion insertion/removal due to the “buffering” action of the graphenic carbon and reduced charge transfer resistance. While this buffering action is a very vague term, in the case of Li insertion/removal, prior studies from our group − and Koratkar’s, Hwang’s, and also Sheldon’s , groups, among others, have indicated a strong influence of the interface between Si, graphene, and the current collector on the Li-storage behavior and associated structural–electrochemical stability. In particular, for the “Li system”, it is believed that preferential Li-segregation at the Si/graphene interface (as compared to that at Si/Cu or Si/Ni interfaces) weakens the same, thus allowing relatively constraint-free dimensional changes of Si upon lithiation/delithiation. ,,, …”

“…Details concerning the graphene and Si growth procedure/parameters, characterizations, and features have been detailed in our previous publications. 23,[31][32][33]45 2.3. Electrochemical Sodiation and Observation of Elemental Concentration Profiles.…”

“…SEM micrographs and Raman spectra obtained with the as-deposited a-Si films are presented in Figures S1 and S2 in the Supporting Information. Details concerning the graphene and Si growth procedure/parameters, characterizations, and features have been detailed in our previous publications. ,− , …”

Si Nanowires Grown on Cu Substrates via the Hot-Wire-Assisted Vapor–Liquid–Solid Method for Use as Anodes for Li-Ion Batteries

“…Numerous elements have been used as catalytic templates, such as Au, Al, Cu, Ti, Zn, and Sn, for SiNW growth. , Previous works from our group have reported the usage of Sn as the catalyst/template for SiNW growth on various substrates like glass, silicon, and stainless steel. This exploits the formation of Sn-Si eutectic alloy at a temperature of 232 °C, leading to SiNW growth at fairly low temperatures. ,− The reports cutting across all fields of applications of SiNWs grown via the VLS mechanism use the Sn template on various substrates, other than copper, even though copper is the choice of metal for commercial applications as the current collector for batteries, supercapacitors, sensors, etc. − The lack of a facile one-step growth of SiNWs on copper complicates the fabrication process and degrades the Si/substrate interface quality by adding a transfer step from other substrates to the copper substrate. , …”