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

Abstract

Silicon is a high-capacity and safer next-generation anode material for Li-ion batteries, with challenges from rapid capacity fade due to colossal volume changes during Li alloying/de-alloying. Nanostructured Si is deemed to address the above issue, with the possible usage of Si nanowires (SiNWs) on copper substrates (sans any binder or conducting additive) offering the highest performance in terms of anode capacity. However, the direct growth of SiNW on copper current collector foils is challenging and not reported earlier. Against this backdrop, we demonstrate here, for the first time, the successful growth of SiNW, with controllable features, on battery-grade copper substrates via a hot-wire-assisted vapor−liquid−solid (VLS) route. The usage of Sn as a nanotemplate has allowed bringing down the growth temperature to 400 °C, with the SiH 4 pressure and growth duration being other crucial parameters controlling various features of SiNWs, such as length, diameter, aspect ratio, effective crystalline core-to-amorphous shell ratio, morphology of the shell, and orientation with respect to the substrate. The emphasis here is on the variations of different morphological features of these nanowires with changes in process conditions as these are bound to have important implications for various electronic applications. One such application that we explore is their usage as an anode in Li-ion batteries. In the Li "half" cell, the free-standing SiNWs on copper foil exhibit reversible Li-storage capacities of ∼3556 mAh/g @ C/5 and ∼2462 mAh/g @ 1C while retaining ∼89% of the capacity after 100 cycles @ 1C. In the Li-ion "full" cell (with a home-made LiFePO 4 -based cathode), ∼97% capacity retention has been obtained after 100 cycles @ 341 μA/cm 2 . The superior electrochemical performance as an anode, the scalability of the growth technique, and the ability to tune the SiNW characteristics open up the possibility of industrial-scale application of the as-grown SiNWs on copper foil.

Constructing Si/6H-SiC Heterostructure As a High-Performance Anode for Boosting Lithium-Ion Storage

“…11 What is more, the poor intrinsic electronic conductivity (<0.01 S cm −1 ) of Si is not good for rate performance. 12 To deal with the problems caused by volume change, extensive efforts have been devoted to the design of reasonable Si nanostructures, including nanoparticles, 13,14 nanowires, 15,16 and nanotubes. 17,18 It has been revealed that, during the lithiation and delithiation processes, Si particles having a critical size of less than 150 nm will not fracture or pulverize.…”

“…To deal with the problems caused by volume change, extensive efforts have been devoted to the design of reasonable Si nanostructures, including nanoparticles, , nanowires, , and nanotubes. , It has been revealed that, during the lithiation and delithiation processes, Si particles having a critical size of less than 150 nm will not fracture or pulverize . The fabrication methods of nanostructured Si include chemical vapor deposition, magnesiothermic reduction reaction, , laser ablation, , and ball milling. − Among these methods, ball milling is cost-effective, easy for mass production, and much more possible for commercial application.…”

Si@C Core–Shell Nanostructure-Based Anode for Li-Ion Transport

“…Tripathi et al presented a notable approach by directly growing silicon nanowires (SiNWs) on copper current collector films, eliminating the need for binders or conductive additives. These Si NWs demonstrated an impressive reversible lithium storage capacity of approximately 2462 mAh g –1 at a current density of 1C . Unfortunately, the electrode can be easily pulverized due to the volume expansion caused by the lithiation of the silicon particles during the charge and discharge cycle.…”

“…These Si NWs demonstrated an impressive reversible lithium storage capacity of approximately 2462 mAh g −1 at a current density of 1C. 5 Unfortunately, the electrode can be easily pulverized due to the volume expansion caused by the lithiation of the silicon particles during the charge and discharge cycle. Subsequently, the pulverized silicon particles will form a solid electrolyte interface (SEI) film on the surface, and the formation of irreversible lithium-silicon compounds will result in the loss of active lithium during discharge.…”

Understanding the Electrolyte Chemistry Induced Enhanced Stability of Si Anodes in Li-Ion Batteries based on Physico-Chemical Changes, Impedance, and Stress Evolution during SEI Formation

“…While nanostructuring of Si, formation of core-shell structures and also composites with Si can potentially alleviate the problem associated with the volume expansion/contraction-induced mechanical degradation, [12][13][14][15][16][17][18][19][20] unless the SEI is stabilized, continuous irreversible consumption of Li-ions during the reformation of the same (and associated accrued impedance) will still cause capacity fade. One of the sustainable methods to improve the conformality of the SEI layer on Si is by incorporating additives into the electrolyte.…”