Spray-Printed and Self-Assembled Honeycomb Electrodes of Silicon-Decorated Carbon Nanofibers for Li-Ion Batteries

Abstract

Directional, micron-scale honeycomb pores in Li-ion battery electrodes were fabricated using a layer-by-layer, self-assembly approach based on spray-printing of carbon nanofibers. By controlling the drying behavior of each printed electrode layer through optimization of (i) the volume ratio of fugitive bisolvent carriers in the suspension and (ii) the substrate temperature during printing, self-assembled, honeycomb pore channels through the electrode were created spontaneously and reliably on current collector areas larger than 20 cm × 15 cm. The honeycomb pore structure promoted efficient Li-ion dynamics at high charge/discharge current densities. Incorporating an optimum fraction (2.5 wt %) of high-energy-density Si particulate into the honeycomb electrodes provided a 4-fold increase in deliverable discharge capacity at 8000 mA/g. The spray-printed, honeycomb pore electrodes were then investigated as negative electrodes coupled with similar spray-printed LiFePO4 positive electrodes in a full Li-ion cell configuration, providing an approximately 50% improvement in rate capacity retention over half-cell configurations of identical electrodes at 4000 mA/g.

Scalable Multilayer Printing of Graphene Interfacial Layers for Ultrahigh Power Lithium‐Ion Storage

“…However, there was also an additional effect that G layers also induced an increase in the local electrode porosity at the junction between LTO and G, as shown in the electrode cross-section SEM image in Figure 5b. Consistent with previous work, [30][31][32] this local porosity will facilitate ion mobility in the region of the electrode/current collector junction particularly at ultra-fast charge/discharge rates (≥ 400 C), where otherwise lithiumion "starvation" may occur, [40][41][42] as depicted in the idealized graphical illustration in Figure 5a.…”

“…As shown in previous studies, these pore structures can be useful in facilitating the dispersion of electrochemically active lithium-ions throughout the electrode, and can promote capacity at fast charging rates (≥ 20 C). [30][31][32][33][34] The thickness of the G layer interleaved between the LTO and current collector was ~ 1 µm, and the G layer on the top of LTO was ~ 2 µm. Overall, all the multi-layered hetero-electrodes were ~ 20 µm thick (see Table 1).…”

“…Spray printing process: For the spray suspension, LTO (or YP), SP and CMC in a controlled mass ratio of 95:3:2 were suspended into a mixture of deionized (DI) water and isopropyl alcohol (IPA) at a DI:IPA volume ratio of 60:40 that had optimum stability without any sediment or suspended particles, and provided the best deposition efficiency of electrode constituents onto the current collector, as reported in previous work. [31] While DI water was required to dissolve CMC, IPA helped to disperse carbon materials. In the case of the G suspension, G and CMC were formulated in a 95:5 mass ratio in the same fugitive solvent mixture.…”

Challenge-driven printing strategies toward high-performance solid-state lithium batteries

“…The resolution of the printed pattern depends on the ink components, nozzle dimensions, gas stream speed, drying process, and so on. [45][46][47] Due to the atomization and drying process, spray-printed patterns are normally porous. 48 Grant et al prepared porous organic electrodes by the "layer-by-layer" spray-printing technique.…”

High energy lithium ion capacitors using hybrid cathodes comprising electrical double layer and intercalation host multi-layers

“…For instance, hard-to-process honeycomb structures have been fabricated spontaneously over large areas of current collectors by combining spray printing with a bi-solvent drying approach, which has been exploited for a diverse range of active materials such as TiO2(B), carbon nanofibers, graphene, AC and LiFePO4 (LFP), in every case boosting electrode reaction kinetics at ultra-fast charging rates. [15][16][17][18] The spray printing process also allows for the fabrication of multi-layered LIB electrode configurations, as the electrode is formed from many sub-layers, layer-by-layer, and each layer can in principle be different in compositions to preceding or subsequent layers. For example, two layer electrodes comprising a porous TiO2 layer (next to the current collector) and a non-porous TiO2 (adjacent to the separator/cathode) showed improved ion mobility and volumetric capacity, [19] while interleaving Si/SiOx nanocomposite layers between two layers of conductive carbon reduced interfacial resistance at the electrode/current collector and avoided pulverization of the Si/SiOx.…”