Low Temperature Deposition of Highly Cyclable Porous Prussian Blue Cathode for Lithium-Ion Microbattery

Designing CoHCF@FeHCF Core-Shell Structures to Enhance the Rate Performance and Cycling Stability of Sodium-Ion Batteries

Prussian blue analogs are well suited for sodium-ion battery cathode materials due to their cheap cost and high theoretical specific capacity. Nax CoFe(CN)6 (CoHCF), one of the PBAs, has poor rate performance and cycling stability, while Nax FeFe(CN)6 (FeHCF) has better rate and cycling performance. The CoHCF@FeHCF core-shell structure is designed with CoHCF as the core material and FeHCF as the shell material to enhance the electrochemical properties. The successfully prepared core-shell structure leads to a significant improvement in the rate performance and cycling stability of the composite compared to the unmodified CoHCF. The composite sample of core-shell structure has a specific capacity of 54.8 mAh g-1 at high magnification of 20 C (1 C = 170 mA g-1 ). In terms of cycle stability, it has a capacity retention rate of 84.1% for 100 cycles at 1 C, and a capacity retention rate of 82.7% for 200 cycles at 5 C. Kinetic analysis shows that the composite sample with the core-shell structure has fast kinetic characteristics, and the surface capacitance occupation ratio and sodium-ion diffusion coefficient are higher than those of the unmodified CoHCF.

Low-Spin Fe Redox-Based Prussian Blue with excellent selective dual-band electrochromic modulation and energy-saving applications

Dual-band electrochromic materials (DBEMs) are of utmost importance for smart windows to realize independent control of the visible (VIS) and near-infrared (NIR) light. However, very few single-component DBEMs are capable of independently and effectively controlling both VIS and NIR light. Here, we present Prussian blue (PB) with remarkable performance to replace the composite DBEMs that require deliberate design and complicated preparation. Excellent durability and capacity were achieved simultaneously due to the activated low-spin Fe in PB. A dual-band electrochromic device (DBED) by using PB thin films as electrochromic layers was constructed, exhibiting superior dual-band electrochromic performance, energy storage performance and memory effect. We show that the energy-saving DBED can be bleached without applying any external bias potential, and can be colored by using a commercial photovoltaic solar panel under ambient solar irradiation. The stored energy during coloration can be further used to light up the lights. Finally, the coloration mechanism of the DBED was studied by the density functional theory calculations, to shed light on the large optical transmittance modulation in both VIS and NIR regions. The new insights will advance the design of efficient and durable DBEMs and the development of bi-functional smart windows.

3D-Printed Silicone Substrates as Highly Deformable Electrodes for Stretchable Li-Ion Batteries

Stretchable energy storage devices receive a considerable attention at present due to their growing demand for powering wearable electronics. A vital component in stretchable energy storage devices is its electrode which should endure a large and repeated number of mechanical deformations during its prolonged use. It is crucial to develop a technology to fabricate highly deformable electrode in an easy and an economic manner. Here, the fabrication of stretchable electrode substrates using 3D-printing technology is reported. The ink for fabricating it contains a mixture of sacrificial sugar particles and polydimethylsiloxane resin which solidifies upon thermal curing. The printed stretchable substrate attains a porous structure after leaching the sugar particles in water. The resulting printed porous stretchable substrates are then utilized as electrodes for Li-ion batteries (LIBs) after loading them with electrode materials. The batteries with stretchable electrodes exhibit a decent electrochemical performance comparable to that of the conventional electrodes. The stretchable electrodes also exhibit a stable electrochemical performance under various mechanical deformations and even after several hundreds of stretch/release cycles. This work provides a feasible route for constructing LIBs with high stretchability and enhanced electrochemical performance thereby providing a platform for realizing stretchable batteries for next generation wearable electronics.

Comparison of Physical/Chemical Properties of Prussian Blue Thin Films Prepared by Different Pulse and DC Electrodeposition Methods

Prussian Blue (PB) thin films were prepared by DC chronoamperometry (CHA), symmetric pulse, and non-symmetric pulse electrodeposition techniques. The formation of PB was confirmed by infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDX) and UV-Vis transmission measurements. X-ray diffraction (XRD) shows the stabilization of the insoluble form of PB. From scanning electron microscopy (SEM) studies, an increase in porosity is obtained for the shorter pulse widths, which tends to improve the total charge exchange and electrochemical stability of the films. While the film prepared by CHA suffered a degradation of 82% after 260 cycles, the degradation reduced to 24% and 34% for the samples prepared by the symmetric and non-symmetric pulse methods, respectively. Additionally, in the non-symmetric pulse film, the improvement in the charge exchange reached ~522% after 260 cycles. According to this study, the deposition time distribution affects the physical/chemical properties of PB films. These results then render pulse electrodeposition methods especially suitable to produce high-quality thin films for electrochemical devices, based on PB.

Conformal atomic layer deposition of RuOxon highly porous current collectors for micro-supercapacitor applications

3D porous electrodes have been considered as a new paradigm shift for increasing the energy storage of pseudocapacitive micro-supercapacitors for on-chip electronics. However, the conformal deposition of active materials is still challenging when highly porous structures are involved. In this work, we have investigated the atomic layer deposition (ALD) of ruthenium dioxide RuO₂on porous Au and Pt architectures prepared by hydrogen bubble templated electrodeposition, with area enlargement factors ranging from 400 to 10 000 cm²/cm². Using proper ALD conditions, a uniform RuO₂coverage has been successfully obtained on porous Au, with a specific electrode capacitance of 8.1 mF cm^-2and a specific power of 160 mW cm^-2for a minute amount of active material. This study also shows the importance of the chemical composition and reactivity of the porous substrate for achieving conformal deposition of a ruthenium oxide layer.