April 22, 2016 | by Alfredo Carpineti
Hang on renewables this is only the beginning. We have seen great leaps in renewable production due to investment and markets. Product efficiency has grown dramatically while cost has plummeted at unprecedented rates.
The last couple of years we have witnessed this happening on the storage side as it is very apparent that if renewables wants to really be a competitive power option it needs to be available on demand. This article posted below from IFLScience! focus' on the science aspect so it will be interesting to discover what the financial feasibility reveals.
Poor battery life is the number one complaint when it comes to smartphones and laptops. As a wireless society, having to tether ourselves down to power up our gadgets seems more and more a nuisance. And while researchers are looking into wireless charging, if batteries were better we would have to worry less.
Now, a new technology promises just that. Researchers from the University of California, Irvine, have invented a nanowire-based battery that can be recharged hundreds of thousands of times, a significant leap towards a battery that doesn’t require replacing.
Nanowires possess several ideal characteristics for electric storage and transmission. They are highly conductive and thousands of times thinner than a human hair, which means they can be arranged to provide a large surface area for electron transfer. Unfortunately, nanowires are usually very fragile and don’t do well after repeated charging and discharging.
The researchers, whose findings are published in the American Chemical Society’s Energy Letters, have coated gold nanowires in manganese dioxide and cocooned them in a Plexiglas-like gel. This combination keeps all the properties of the nanowires' intact and makes them resistant to fractures.
Mya Le Thai, the lead study author, has charged and discharged the battery up to 200,000 times without breaking the nanowires and without loss of capacity.
“Mya was playing around, and she coated this whole thing with a very thin gel layer and started to cycle it,” said senior author Reginald Penner, chair of UCI’s chemistry department, in a statement. “She discovered that just by using this gel, she could cycle it hundreds of thousands of times without losing any capacity.”
“That was crazy,” he added, “because these things typically die in dramatic fashion after 5,000 or 6,000 or 7,000 cycles at most.”
The researchers believe that the combination of the PMMA (plexiglass-like) gel electrolyte and the magnesium oxide gives flexibility and structure to the nanowires, preventing cracking and thus extending their operational life.
“The coated electrode holds its shape much better, making it a more reliable option,” Thai said. “This research proves that a nanowire-based battery electrode can have a long lifetime and that we can make these kinds of batteries a reality.”
We demonstrate reversible cycle stability for up to 200 000 cycles with 94–96% average Coulombic efficiency for symmetrical δ-MnO2 nanowire capacitors operating across a 1.2 V voltage window in a poly(methyl methacrylate) (PMMA) gel electrolyte. The nanowires investigated here have a Au@δ-MnO2 core@shell architecture in which a central gold nanowire current collector is surrounded by an electrodeposited layer of δ-MnO2 that has a thickness of between 143 and 300 nm. Identical capacitors operating in the absence of PMMA (propylene carbonate (PC), 1.0 M LiClO4) show dramatically reduced cycle stabilities ranging from 2000 to 8000 cycles. In the liquid PC electrolyte, the δ-MnO2 shell fractures, delaminates, and separates from the gold nanowire current collector. These deleterious processes are not observed in the PMMA electrolyte.
Degradation and Failure Discovery Platform. (a) Schematic diagram showing critical dimensions of the Au@δ-MnO2 all-nanowire capacitor investigated here. The PMMA gel layer, consisting of 20 (w/w)% PMMA in 1.0 M LiClO4 and PC, is 180 μm in thickness. (b) Low-magnification image of a several Au@δ-MnO2 nanowires on the capacitor surface. (c) High-magnification SEM image of the gold nanowire core of the Au@δ-MnO2 nanowires with lateral dimensions of 35 nm (h) × 240 nm (w). (d) High-magnification SEM image of a Au@δ-MnO2 nanowire showing the morphology of the electrodeposited δ-MnO2 shell with a mean thickness of 124 nm.(1) (e) Photograph of the capacitor containing 750 parallel nanowire loops patterned onto a glass microscope slide.
(Below) SEM (a–d) and AFM (e–h) images of gold (a,e), and Au@δ-MnO2 core@shell (b–d, f–h) nanowires: (a,e) gold nanowire comprising the core of Au@δ-MnO2 core@shell nanowires. A height versus distance amplitude trace is shown below each AFM image. (b,f) Au@δ-MnO2 core@shell nanowire prepared by electrodepositing MnO2 onto the gold nanowire shown in (a) for 5 s. (c,g) MnO2 deposited for 10 s. (d,h) MnO2 deposited for 40 s. (i–k) Charge storage performance for all nanowire capacitors composed of Au@MnO2 nanowires. All data here were acquired using the PMMA gel electrolyte except in the case of the 222 nm shell thickness, where data for the PMMA gel electrolyte and PC-only electrolyte are both shown (k). (i) Cyclic voltammograms at 100 mV/s for capacitors prepared with three MnO2 shell thicknesses, 143, 222, and 300 nm, as indicated. (j) Galvanostatic charge/discharge curves for nanowire capacitors at 1 A/g. Total Csp values are 19, 34, and 56 F/g for tMnO2 values of 300, 222, and 143 nm, respectively. (k) Csp versus scan rate for MnO2 nanowire arrays. For the 222 nm shell thickness, data for PMMA (solid green line) and no PMMA electrolytes (dashed green line) are compared. Error bars represent ±1σ for three as-prepared capacitors at each tMnO2.
Cycle stability of Au@δ-MnO2 core@shell nanowire capacitors. (a,b) Csp versus cycles for MnO2 shell thicknesses as indicated. Also plotted (top) is the Coulombic efficiency for the 222 nm MnO2 shell thickness. Other shell thicknesses were virtually identical. (b) Detail showing the first 20 000 cycles in (a). (c) CVs at 100 mV/s for the 222 nm MnO2 shell thickness acquired for cycle 1 and cycle 100 000, as indicated. (d) Csp versus scan rate for the 222 nm MnO2 shell thickness, for data acquired at 6000, 40,000, 75 000, and 95 000 cycles, as indicated
Figure 4. SEM analysis of Au@δ-MnO2 nanowires before and after cycling. (a–d) SEMs at low (a,c) and higher (b,d) magnification show two identical, as-prepared Au@δ-MnO2 nanowires with shells of thickness 220 nm. (e,f) SEMs of the same nanowire shown in (a,b) after 4000 charge/discharge cycles. The short-range loss of MnO2, from 100 to 500 nm domains, is readily apparent in these images (green arrows). (g,h) SEMs of the same nanowire shown in (c,d) after 100 000 charge/discharge cycles. In contrast to (e,f), using the PMMA gel electrolyte, no shell loss is observed in this case. SEM analysis of Au@δ-MnO2 nanowires before and after cycling. In PC without PMMA, short-range loss of MnO2 (e,f) precedes long-range loss of the MnO2 shell over a length scale of microns. SEM images of a single nanowire loop of a Au@δ-MnO2 core@shell structure without PMMA (i) and with PMMA (j) document the loss of the MnO2 shell (green arrows) in the absence of the PMMA
Scheme 1. (a) Illustration of the Two-Stage Progression of Degradation for Au@δ-MnO2 Nanowires in PC Electrolyte without PMMA gela and (b) Addition of PMMA to the PC Electrolyte Forestalling Both of These Degradation Modes