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Researchers Develop Solid But Flexible Electrolyte For Bendable Batteries

Unknown Lamer posted about 2 years ago | from the stretch-armstrong-2.0 dept.

Power 41

hypnosec writes "Korean scientists have developed a 'fluid-like' polymer electrolyte used in lithium-ion batteries that would pave way for flexible batteries and flexible smartphones. The discovery was made by a joint team of researchers that was led by Professor Lee Sang-young of Ulsan National Institute of Science and Technology. The new electrolyte, though flexible, is made of solid materials hence making the batteries more stable than the lithium-ion batteries used today." Paper, but full text is paywalled.

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Why do we need flexible phones? (3, Interesting)

Yarhj (1305397) | about 2 years ago | (#42602451)

I've seen flexible phones given as the justification for dozens of research projects over the last few years, but does anyone actually want them? I have no real need or desire to roll my phone up and put it in my pocket -- it would just fit worse than it does now. I'd much rather have a battery that lasts through an entire day.

Re:Why do we need flexible phones? (1)

djsmiley (752149) | about 2 years ago | (#42602541)

If they don't shatter when you drop them, I can see that being a plus for many people..... however its not for me. I don't drop my stuff :D

Re:Why do we need flexible phones? (4, Informative)

ledow (319597) | about 2 years ago | (#42603483)

I drop every gadget I've ever owned. Some of them multiple times every day. And I mean, drop, as in pull something out of my pocket and my satnav/phone/etc. goes flying out with it at high speed and whacks against a wall and then hits the floor.

I have yet to actually BREAK a gadget like that. I have scratched screens slightly but never to the point they were unusable. Hell, most of my gadgets end up going through the washing machine and dryer at least once in their life.

A flexible phone just seems to have other ways to break it - flexing it too far, applying pressure at odd angles when flexed, etc. Unless I can actually fold it like paper, it's going to have a point where it breaks. And if I can fold it like paper, then it's going to have to suffer what a piece of paper (like a receipt) can go through in the bottom of your pocket afresh EVERY DAY without problems.

Hell, most paper receipts in my pocket don't last 24 hours without tearing or being so folded and smudged that they are unreadable. I can't imagine a plastic device of any material tolerating that at all.

If a phone is "flexible", it has to be VERY flexible. Almost ridiculously flexible. I don't think this generation or even the next of flexible gadgets will be. But if it's solid, it only has to be quite solid, and have a little band of rubber in the right place and it's nigh-on invincible in daily use, and we already know how to do that (whether manufacturer's BOTHER to do it is another matter, I'm still waiting for a laptop with decent hinges on the screen because that's killed every laptop I've ever owned).

I honestly don't think that if I took one of these "flexible" phones and tried to fold it in half along a sharp crease that it would work afterwards. And that's exactly the kind of thing that would happen in my pocket with my large bunch of keys, wallet, GPS, etc. in it at various times of the day.

All being flexible does is give you ways to put even more pressure on the materials. Solid devices cannot occupy each other's spaces, and internal materials are protected by an external core (which means only half your things have to be able to take abuse).

But a flexible phone, thrown in my pocket, will uncurl, curve, twist and bend as I walk and EVERY component has to suffer that. Then when I throw my keys in or ram a chocolate bar into my pocket, it's going to put huge pressure on the edges of those curves and make things bend perpendicular to anything it's already experiencing and that's going to snap it, break it, pop it (I imagine if you flex one area, it will have to "pop" into a shape to relief the stress, like those squidgy-balls-in-a-net), or just make the internals wear to the point that a vital connection stops working.

Seriously, the "gentle-wibble" that I see in demos today isn't flexibility that's practical. Show me a phone you can screw up like a piece of paper while in the heat of the moment and then just throw, and it survives it thousands of times over, then you might have a material that can live up to public consumption.

My car aerial is "flexible", but I can't get it back to straight if I kink it. That's the sort of flexible they are selling, but not the sort they are promising.

Re:Why do we need flexible phones? (0)

Anonymous Coward | about 2 years ago | (#42606795)

There are probably a few people out there that wants a phone that flexes for the novelty, etc. The trick is to then put the flexible phone in a rigid case, and treat it as a more durable rigid phone, subsidized by the people who want that novelty. You could go either two ways with that then. You can make the rigid case out of less material, so it is not quite as rigid now, but enough to not easily bend in regular use while any bending it transmits to the phone in dropping or rough handling would be well within the flexibility limits of the phone. Alternatively, just make the case, etc., as rigid as normal, but now there is one less failure point. Way too many electronics I've seen fail, either in the short term or long term, due to slight flexing from handling damaging a solder point. Sometimes it is a design flaw, because of the location of components and mounting that allows that to happen way too quickly. But if the device was designed to be flexed quite a bit, and was tested to that effect, then may gain some resilience for those that flex it no where near those limits.

Re:Why do we need flexible phones? (0)

Anonymous Coward | about 2 years ago | (#42602545)

I've seen flexible phones given as the justification for dozens of research projects over the last few years, but does anyone actually want them?

Not me. I'd rather they spend their R&D time and money on getting me a decent cell signal here in NJ and when I'm in the canyons of NYC. AT&T, I'm talking to you (though I'm sure all the major carriers in the US suck at this). I'm still hitting 'Edge' cell towers in my area - and even more so after Sandy knocked things around.

Flexible phone? No! Cell service? Yes!

Re:Why do we need flexible phones? (5, Interesting)

Anonymous Coward | about 2 years ago | (#42602585)

A flexible battery might allow 'more' battery to be inserted in an available space. If your device has space leftover that isn't nicely cubical, finding a battery to fill it is difficult. This could reduce that problem.

There's also flexible keyboards you can roll up, so a flexible tablet could have its uses.
There was also a story long time ago about clothes that generated power from movement or some such thing. Having the batteries in the clothing would be easier to use than a separate battery pack.

Re:Why do we need flexible phones? (3, Funny)

vlm (69642) | about 2 years ago | (#42602903)

A flexible battery might allow 'more' battery to be inserted in an available space.

Adult entertainment novelty items. The phone's "vibrate motor" comes in handy too.

Re:Why do we need flexible phones? (0)

Anonymous Coward | about 2 years ago | (#42602637)

You probably don't need a flexible phone. There are however people who need them, or rather, they need a phone that won't break and have to buy the more expensive rugged phones. A flexible phone can be dropped, stomped on, driven over or whatever without breaking. If you don't want it fold-able you can glue it on a hard base and the base could crack without loss of phone functionality. You can mold a thick rubber casing around the flexible phone and you get a pretty much indestructible phone. (For normal accidents that is. Intentional incineration is hard to protect against.)

There is also the market segment for intelligent clothing.

Re:Why do we need flexible phones? (0)

Anonymous Coward | about 2 years ago | (#42602721)

Flexible phones may not warrant the volume of research thats being pumped into them, but thankfully, the markets will decide if these features are to be successful in the end or not. Someone seems to think so. For that I am glad. How often does a discovery or process actually stop at the application it was intended to be used for? Think velcro! Great for securing astronauts to bedding, sure. But the applications that came after it are endless...

I suspect that even if "flexible phones" are not the ideal use-case for bendable batteries, the knowledge gained by this research will prove useful in some other industry or application. Its for this reason I applaud them for their discovery, and challenge the entrepreneurial thinkers to apply it in ways not originally conceived by the developers. Maybe as a power source for pace-makers or some other bio/electric device? Who knows!

Any yay for any additional research going into batteries at all. With electric vehicles and portable devices exploding in pervasiveness, any insight into energy storage technologies are welcome!

Re:Why do we need flexible phones? (0)

Anonymous Coward | about 2 years ago | (#42602827)

Clearly you are wrong. You want a 6" or 7" flexible phone that you can roll up in your pocket so that it looks like you are lugging around a boner all day. Sheesh.

Re:Why do we need flexible phones? (4, Insightful)

MacTO (1161105) | about 2 years ago | (#42603041)

The talk of rolling and folding is just to get people excited.

A far more realistic use would be to make more durable devices: something that you can put into your purse or pocket and not have to worry about as much. (Example: the screen won't crack if the case is twisted a bit.) I'm guessing that it will also allow for much thinner devices, since they don't have to worry about making rigid cases.

Re:Why do we need flexible phones? (2)

q.kontinuum (676242) | about 2 years ago | (#42603215)

According to the article the new batteries are more durable, faster to produce and safer. That they are also flexible is probably a nice side effect. As for the use cases: Maybe currently this would be more interesting for tablets. I'd like them to be bendable like a journal, much easier to pack them in my bag.

Re:Why do we need flexible phones? (1)

NatasRevol (731260) | about 2 years ago | (#42603327)

Are you really so short sighted?

The battery is flexible - it can fit into all available space, giving much more usable energy.

If the battery is flexible, then the casing can be. It's a useful extension of the form factor, think medical devices. Not just phones - that's how people sell it to the MBAs for research money.

Re:Why do we need flexible phones? (0)

Anonymous Coward | about 2 years ago | (#42603447)

I've seen flexible phones given as the justification for dozens of research projects over the last few years, but does anyone actually want them? I have no real need or desire to roll my phone up and put it in my pocket -- it would just fit worse than it does now. I'd much rather have a battery that lasts through an entire day.

Flexible phones? you're so limited... It's dildos. Flexible, rubbery dildos.

Re:Why do we need flexible phones? (1)

Lawrence61 (868933) | about 2 years ago | (#42604281)

I have no need for a flexable phone either.

Re:Why do we need flexible phones? (0)

Anonymous Coward | about 2 years ago | (#42604613)

Bracelet. You use your bracelet as a phone and if you need a tablet, you take it off your hand and unfold it.

Re:Why do we need flexible phones? (1)

ryzvonusef (1151717) | about 2 years ago | (#42607073)

You should check out the Nokia Morph Phone Concept.

http://www.youtube.com/watch?v=IX-gTobCJHs [youtube.com]

They had certain ideas about the possible applications of a flexible phone.

Re:Why do we need flexible phones? (1)

Hentes (2461350) | about 2 years ago | (#42607295)

Right now we have three kinds of portable devices: phones, tablets and laptops. A foldable, self-powered touchscreen could serve as all three, while communicating with the computing unit in your bag/pocket wirelessly.

Re:Why do we need flexible phones? (0)

Anonymous Coward | about 2 years ago | (#42607465)

I think flexible paper-like tablet PCs might be a better application than flexible phones

Flexible watch (0)

Anonymous Coward | about 2 years ago | (#42608991)

I know a lot of people use their phone for a time piece now.
But still, I'd buy a ultra thin watch with the battery in the band!
Something like the Tron watch might be possible.

Liquid energy (1)

Prokur (2445102) | about 2 years ago | (#42602547)

Interesting ideas come to my mind if such "liquid" would be really liquid

Re:Liquid energy (0)

Anonymous Coward | about 2 years ago | (#42603479)

I don't think that's what's meant by "energy drink"...

Re:Liquid energy (1)

kelemvor4 (1980226) | about 2 years ago | (#42606751)

I don't think that's what's meant by "energy drink"...

Your cell phone disagrees!

It's got what plants crave! (0, Offtopic)

Anonymous Coward | about 2 years ago | (#42602671)

It's got what plants crave!

cellphones shmellphones (3, Insightful)

Anonymous Coward | about 2 years ago | (#42602697)

According to the researchers, conventional batteries that use liquefied electrolytes are inflexible and are at the risk of explosion. The new electrolyte though flexible is made of solid materials hence making the batteries more stable than the lithium-ion batteries used today.

“Because the new battery uses flexible but solid materials, and not liquids, it can be expected to show a much higher level of stability than conventional rechargeable batteries” said an official of Korean Science Ministry notes Korean Joongang Daily.

The process of creating these flexible batteries is faster than that used to manufacture conventional batteries. The new flexible polymer electrolyte is spread on electrodes which are then blasted with UV light for about 30 seconds.

Flexibility is minor news. Great news is: electric cars just became safer and cheaper. Extra good news for me personally is: soon there'll finally be cars worth buying on the market.

Re:cellphones shmellphones (1)

ledow (319597) | about 2 years ago | (#42603259)

"just became" = "might, possibly, maybe, years in the future, when the economies of scale bring this down to the same price as a 'normal' battery"

Personally, I'd just rather we worked out how to reduce the weight of batteries. It would have much, much more effect and wins all round. Second would be power capacity, but that's obvious and comes as part of the reduction of weight too.

Re:cellphones shmellphones (0)

Anonymous Coward | about 2 years ago | (#42604359)

Personally, I'd just rather we worked out how to reduce the weight of batteries. It would have much, much more effect and wins all round. Second would be power capacity, but that's obvious and comes as part of the reduction of weight too.

Done [slashdot.org] , and done!

Weave a thin conductive fabric, print just.enough.thick layer of electrode (Lithium) material upon it, spread electrolyte "jam" over it, UV bake it for 30 secs, strap another patch of CNT fiber fabric over it and you have a LIB cell that is light as a LIB was never before! Oh, and flexibility stays, of course. You can roll them into cylinders or whatever ...

Re:cellphones shmellphones (0)

Anonymous Coward | about 2 years ago | (#42603603)

"Flexibility is minor news. Great news is: electric cars just became safer and cheaper. Extra good news for me personally is: soon there'll finally be cars worth buying on the market."

Finally! Flexible electric cars for the pothole-ridden US roads.

Article text (1)

krakass (935403) | about 2 years ago | (#42603021)

Rechargeable lithium-ion batteries, the most popular energy source for mobile electronic devices, are rapidly expanding their range of applications into fields such as electrical vehicles, grid energies, and flexible electronic devices.1 This strong market demand stimulates the need for development of advanced lithium ion battery technologies capable of improving energy storage densities, cycle life, charge/discharge rates, and design flexibility.2, 3

One strategy to address certain of these goals involves advanced structural design in the electrodes, along with associated new material development. For example, three dimensional (3D) electrodes can yield improvements in rate capability and capacity retention.4–6 These advantages are further enhanced in high-capacity anode materials, such as silicon and tin, which undergo large changes in volume during charge/discharge cycling.7, 8 One challenge for 3D electrodes, particularly in integration of active components, arises from difficulties in securing conformal electrolytes that can also prevent electrical shorts between electrodes.6 Although liquid electrolytes ensure excellent electrochemical performance and good physical contact with 3D electrodes, they suffer from potential leakage, leading to safety concerns. More importantly, liquid electrolytes limit choices in cell design due to their fluidic characteristics and the need for separator membranes in cell assembly. This situation motivates the development of self-supporting solid-state electrolytes that can conform to 3D electrodes and, at the same time, provide sufficient mechanical deformability for reliable use, especially for applications in flexible electronics and other demanding areas of envisioned use.

Among various solid-state electrolytes, gel polymer electrolytes (GPEs), which are generally composed of polymer matrix and liquid electrolyte, are widely used in lithium-ion batteries owing to their excellent ionic conductivity, low rates of safety failure, and mechanical flexibility.9–11 In general, conventional GPEs are prepared using a predesigned frame via solution casting of liquid state mixtures (i.e., liquid electrolytes and polymers dissolved in organic solvents or liquid electrolytes/polymerizable monomers), followed by solvent evaporation or chemical cross-linking for solidification. The initial, liquid-state, mixtures for GPEs have limited dimensional stability before solidification due to their intrinsically fluidic characteristics, thereby restricting their facile application to complex-structured systems such as 3D batteries.

To the best of our knowledge, there are no polymer electrolytes that are both shape-conformable to 3D electrodes and mechanically flexible without impairing their electrochemical performance. Moreover, it is still challenging to secure dimensional stability (as a solid form) of polymer electrolytes during electrolyte preparation and cell assembly process.6, 12

In the following, we demonstrate a facile and scalable approach to the fabrication of highly ion-conductive and bendable polymer electrolytes that can be also conformable to 3D micropatterned architectures of electrodes over large areas. These polymer electrolytes can also be directly writable or printable onto substrates of interest (including electrodes with complex geometries) due to well-tuned rheological characteristics. The materials are a kind of composite gel polymer electrolyte (hereinafter, referred to as “c-GPE”), composed of a UV (ultraviolet)-cured ethoxylated trimethylolpropane triacrylate (ETPTA) polymer matrix, high-boiling point liquid electrolyte (1M LiPF6 in ethylene carbonate (EC)/propylene carbonate (PC) = 1/1 (v/v)), and alumina (Al2O3) nanoparticles (Figure 1a). The ETPTA monomer, which contains trivalent vinyl groups that participate in UV-crosslinking,13, 14 serves as a mechanical framework (after UV-curing). The chemical structure of the ETPTA, along with 2-hydroxy-2-methyl-1-phenyl-1-propanon (HMPP, a photo-initiator), appears in Figure S1 in ESI. The Al2O3 nanoparticles are incorporated as a functional filler to control the rheological properties of the electrolyte mixture and enable direct printing on a substrate such as an electrode.

Figure 1. a) Conceptual illustration of an imprintable, flexible, shape-conformable c-GPE. b) Dripping characteristic of a liquid electrolyte that does not incorporate Al2O3 nanoparticles (designated as F-solution). c) Non-dripping behavior of UV-curable electrolyte mixture before UV-crosslinking reaction (designated as V-solution). d) Comparison of viscosity (as a function of shear rate) between the F- and V-solution.

As a control sample, an electrolyte mixture (hereinafter, referred as “F-solution”) comprised of the ETPTA monomer and liquid electrolyte without Al2O3 nanoparticles, was also cast onto an LiCoO2 cathode. Due to its fluidic character, the F-solution flows easily when it is vertically tilted (Figure 1b). By contrast, an otherwise similar solution with Al2O3 nanoparticles (hereinafter, referred as “V-solution”) is highly viscous and undergoes limited flow even before UV crosslinking (Figure 1c). Viscosity measurements reveal that the F-solution exhibits traditional Newtonian behavior, yielding a viscosity of 11 cP. The V-solution, on the other hand, shows a non-Newtonian response, (i.e., typical shear-thinning behavior), wherein the viscosity increases by 4 orders of magnitude as compared to the F-solution (Figure 1d). This unique rheological feature of the V-solution can facilitate its application in writable or printable electrolyte systems.

It should be noted that the rheological behavior of the V-solution depends strongly on composition ratio and dispersion state of the Al2O3 nanoparticles. Here, the Al2O3 content was varied between 33% and 80%, as determined by the amount of Al2O3 in total weight (= Al2O3 + ETPTA + liquid electrolyte) (See Figure S2 in ESI). Among the various compositions, an Al2O3 content of 66% was found to exhibit optimal rheological properties, for printing and comforming to complex-structured substrates.

Direct UV-assisted nanoimprint lithography (UV-NIL)15–18 was exploited to construct 3D shape-comformable polymer electrolytes from the rheologically tuned V-solution. The UV-IL technique is a well known, versatile patterning technology for production of diverse micro- and nanostructures for microelectronics, optoelectronic devices, and high-density magnetic data storage. Here, we used PDMS stamps for UV-NIL, featuring a maze-like structure with a repeating surface grating (wall thickness and height were 10 m, respectively) in 1.5 cm × 1.5 cm dimensions. We also explored silicon anode pillars on a rigid silicon wafer as columnar structure6, 19, of a type that is prefered for 3D electrodes designed to accomodate severe volume change during charge-discharge cycle. These two structures were used to investigate not only the applicability of polymer electrolyte on flexible and rigid substrates but also replication of round and angular patterns. PDMS stamps were formed using the casting and curing procedures of soft lithography with a master fabricated by exposure (365 nm UV mask-aligner; Karl-Suss) of photoresist SU-8 (Micro Chem) on a silicon wafer. Pressing such stamps against cast layers of V-solutions followed by UV exposure through the stamps yielded solid replicas while in contact (Figure 2a). A SEM image of a molded c-GPE with maze patterns demonstrates the high fidelity that can be achieved in this process, where the structures show well-defined vertical edge profiles and high mechanical stability (Figure 2b). A high-magnification, cross sectional SEM image shows that the Al2O3 nanoparticles are uniformly dispersed through the c-GPE (see Figure S3 in ESI).

Figure 2. a) Steps for fabricating an imprintable, bendable, and shape-conformable polymer electrolyte (c-GPE) via direct UV-assisted nanoimprint lithography (UV-NIL) b) A SEM photograph (surface) of a c-GPE with a maze-pattern (an inset is a cross-sectional image). c) Photographs demonstrating highly-bendable and twistable features of c-GPE. d) FT-IR spectra depicting acrylic C = C double bonds of V-solution (before UV-irradiation) and c-GPE (after UV-irradiation).

The mechanical bendability of the c-GPE as a self-standing film (thickness 150 m) was quantitatively measured using a bending test (under longituidinal strain ranged from 10 to 30 mm, strain rate = 10 mmmin1). The c-GPE offers strong resistance to mechanical breakage upon appreciable bending (bending radius 0.5 cm), even at a low concentration of polymer matrix (i.e., ETPTA/liquid electrolyte = 15/85 w/w). Also, the c-GPE retains dimensional stability until the 29th bending cycle. (Fracture occurs upon additional cycles, as in Figure S4 in ESI). The c-GPE was also mechanically stable under the twisting (bending radius 0.35 cm) (Figure 2c) deformations. Moreover, the maze patterns do not distort even after being subjected to five cycles of bending stress (bending radius 0.5 cm) (see Figure S5 in ESI), which reflects the excellent structural stability of the c-GPE.

The FT-IR measurements before and after UV-irradiation show that the characteristic peaks assgined to acrylic C = C bonds (1610 1625 cm1)13, 14 disappear (Figure 2d), which verifies that the crosslinking reaction is successfully completed in the c-GPE. This process was further confirmed by estimating the gel content of c-GPE, after solvent (dimethyl carbonate followed by acetone) extraction to remove the incorporated liquid electrolytes and any unreacted monomers.20 Over 99% by weight remained relative to the initial weight of UV curable monomer. This result verifies that the UV-curing reaction of ETPTA monomer in the c-GPE was nearly complete. The solid electrolyte characteristics (electrochemical stability, ionic conductivity, and cell performance) of the c-GPE are examined. Linear sweep voltammograms indicate that no significant decomposition of any components in the c-GPE takes place below 4.5 V vs. Li/Li+. This high anodic stability suggests potential for application to high-voltage lithium-ion batteries (Figure 3a). Figure 3a shows that the ionic conductivity of the c-GPE is more than 103 S cm1 at room temperature, with values that increase with temperature. Another advantageous feature of the c-GPE is that no weight loss is observed below temperature of 100 C, as observed from the TGA result due to the presence of high-boiling point liquid electrolyte (i.e., 1M LiPF6 in EC/PC) (Figure 3b).

Figure 3. a) Electrochemical stability window for a c-GPE (an inset shows temperature-dependent ionic conductivity of c-GPE). b) TGA profiles showing difference in thermal stability compared to a conventional carbonate-based liquid electrolyte (1M LiPF6 in EC/DEC = 1/1 v/v) and c-GPE. c) Charge/discharge profiles of a cell (lithium metal/flat-shaped c-GPE/LiCoO2 cathode) as a function of cycle number (at a constant charge/discharge current density = 0.5 C/0.5 C under a voltage range of 3.0–4.2 V). d) Cycling performance (= capacity retention with cycling and coulombic efficiency of a cell, lithium metal/flat-shaped c-GPE/LiCoO2 cathode).

Cycling performance of the cell (LiCoO2 cathode/c-GPE/lithium metal anode) was examined using a flat c-GPE film, where the cell was cycled between 3.0 and 4.2 V at a constant charge/discharge current density (= 0.5 C/0.5 C). The cell exhibits highly stable charge/discharge profiles up to the 50th cycle (Figure 3c). In addition, the couloumb efficiency is 97%, thereby contributing to the negligible capacity loss during cycling (Figure 3d).

To explore the feasibility of applying the c-GPE to 3D- electrodes, cells were prepared using silicon anodes that are patterned into arrays of columns supported by similarly structured copper on a silicon wafer. The fabrication involved sputter deposition of silicon to a thickness of 40 nm onto the copper in pillars with heights of 18 m,21 where the electrode area is 0.9 cm × 0.9 cm. The electrode was incorporated into a cell that employs lithium metal as the counter electrode and c-GPE as the solid electrolyte (see Figure S6 in ESI). As shown in Figure 4, an inverse replica of the 3D silicon structure is successfully formed in the c-GPE, allowing good contact with the anode. Analysis of the SEM images (Figure 4c) shows that the imprinted c-GPE has a height (18 m) and radius (153 m), well matched with the dimension of the 3D silicon anode.

Figure 4. a) Charge/discharge profiles of a cell comprising a 3D Si anode/c-GPE/lithium metal as a function of cycle number (at a constant charge/discharge current density = 0.5 C/0.5 C under a voltage range of 0.01–1.5 V). b) A SEM photograph of a 3D pillar (height = 18 m, radius = 153 m) structured current collector. c) A SEM photograph (surface) of inversely-replicated c-GPE (i.e., after being detached from the 3D pillar structured Si anode), where the inset is a cross-sectional image. d) A SEM photograph (surface) of an inversely-replicated c-GPE disassembled from a cell after the 10th cycle of operation (the inset is a cross-sectional image).

Figure 4a shows the cycling performance of the cell (Si anode/c-GPE/Li metal) using inversely-replicated c-GPE as an electrolyte, where the cell was cycled between 0.01 and 1.5 V at a constant charge/discharge current density (= 0.5 C/0.5 C). The cell shows capacity loss due to SEI (solid electrolyte interphase) layer formation at the first cycle and gradual capacity decay afterwards. This charge/discharge behavior of the cell is similar to the previously reported results for 3D Si anodes.22 From a calculation based on the 40 nm thickness silicon, the initial charge (i.e., lithiation of silicon anode) capacity is found to be 2680 mAh g1. Although the capacity retention with cycling is not ideal, because the 3D-structured cells are not optimized, the overall cycling performance is promising compared to that of c-GPE with non-optimized Al2O3 content. Moreover, Figure 4d shows that the inversely-replicated structure of the c-GPE is almost unchanged, even after the 10th cycle, compared to the initial shape (Figure 4c). This result demonstrates dimensional stability in the imprinted c-GPE and verifies the successful application of the shape-conformable c-GPE to the 3D-structured cells. It also suggests that the good cycling performance in the optimized c-GPE formulation results from its outstanding imprintability, shape conformability, flexibility, and electrochemical performance. These attributes can facilitate the development of 3D-structured battery systems.

Figure 5 shows that Al2O3 content of 33% (or 80%) leads to unsuccessful integration on 3D Si anodes due to non-optimized rheological properties, consistent with the previous result (Figure S2). It should be noted that the structure of the imprinted c-GPEs has a significant influence on the cell performance. For instance, c-GPE with Al2O3 content of 33%, where the c-GPE exhibits highly fluidic characteristic, most of the 3D Si anode remains uncoated. As a result, no meaningful charge/discharge reaction is obtained, likely due to internal short-circuit between the anode and cathode. For c-GPE with Al2O3 content of 80%, the Al2O3 nanoparticles agglomerate, and the c-GPE does not completely cover the 3D Si anode. The mechanical compliance diminishes, and large-sized pinholes and cracks appear. Due to this non-uniform morphology of the imprinted c-GPE, the cell assembled with the c-GPE does not provide normal charge/discharge behavior. More specifically, excessively large charge capacity and very low coulombic efficiency ( 9%) at the 1st cycle are observed. The cell in this case might be partially internally short-circuited due to the poorly-imprinted c-GPE on the 3D Si anode.

Figure 5. Charge/discharge profiles of a cell comprising 3D Si anode/non-optimized c-GPE/lithium metal as a function of cycle number (at a constant charge/discharge current density = 0.5 C/0.5 C): (a) Al2O3 content = 33%; (b) Al2O3 content = 80%.

In summary, we successfully fabricated highly ion-conductive, bendable polymer electrolytes that are also conformable to 3D micropatterned architectures of electrodes over large areas. More notably, the polymer electrolytes can be directly writable or printable onto complex, contoured substrates, owing to the structural uniqueness and well-tuned rheological characteristics. A persistent challenge in the development of 3D-structured or flexible batteries is in the maintenance of good contact between polymer electrolytes and electrodes, to facilitate electrochemical reaction at the interface. In this respect, the polymer electrolytes introduced here can be important.

woo (1)

strack (1051390) | about 2 years ago | (#42603023)

Well thats a relief. Thats whats always bothered me about batteries. Just how gosh darn inflexible they are. Cough.

Re:woo (1)

ledow (319597) | about 2 years ago | (#42603157)

A flexible battery, means flexible devices.

It also means a much more custom-shaped battery which could also mean either smaller devices (with weird shaped batteries) or impossible-to-source replacement batteries.

You're right, in that I'd much rather have 1% more battery life than anything flexible, but you can also see why some companies would love this technology to exist.

"Flexible" is the new "tablet" which only took 20+ years to appear after it first became viable and probably won't last another 5 before it's superceded by something else.

Solid and flexible electrolyte? (1)

blind biker (1066130) | about 2 years ago | (#42603381)

Like Nafion, which is several decades old.

Article Should Read (0)

Anonymous Coward | about 2 years ago | (#42603415)

Technology copied from US company Solicore which developed and has already been selling this technology for 10 years. Yawn.

Electrolytes (0)

Anonymous Coward | about 2 years ago | (#42604107)

Wasn't this addressed in "Idiocracy"? "It's got ELECTROLYTES."

mo3 doLwn (-1, Redundant)

Anonymous Coward | about 2 years ago | (#42604169)

*BSD but FreeBSD Be treated by your obligated to care Fucking market don't ffel thAt Get tough. I hope

How different from LiPo? (1)

Arrepiadd (688829) | about 2 years ago | (#42604975)

The cell phone I bought quite a few years ago (more than a decade) has a Li-pol battery [wikipedia.org] .
This seems to be based on a similar idea (they mention a polymer matrix as well) so solid but flexible electrolyte is not a first, as I have a consumer device over a decade old that has exactly that.[1]
The novelty seems to be (from reading the actual pay-walled article, God forbid!) that this can be printed. But even this may just be similar to all of these "in a computer" patents. Maybe back then it was also true, but now printable is fashion in science.
So, this seems to be a case of "scientists develop an improved version of what has been on consumer devices for over a decade. Expect to see it in the market by 2030 due to costs."

[1] Granted, it's packaged in a non-flexible case, but I that's how I like my phones to be anyway.

Other benifits beyond flexible batteries (0)

Anonymous Coward | about 2 years ago | (#42605125)

Having a solid electrolyte opens up other opportunities beyond just a flexible battery. If it has decent performance (most solid electrolytes have way too high impedance), a solid electrolyte opens up a lot of possibilities, such as different manufacturing techniques, and increased safety.

I can just see the marketing slogans (1)

CCarrot (1562079) | about 2 years ago | (#42605309)

Welcome to the new iPhone 11*...now limper than ever!

*Note: substitute 'Galaxy XYZ' if you're an Apple fan

Sigh... (1)

P-niiice (1703362) | about 2 years ago | (#42607485)

If only my contract had any flex.

Would the manufacturing be less toxic? (1)

Forever Wondering (2506940) | about 2 years ago | (#42609383)

IIRC, current lithium ion battery production produces a fair amount of pollution. Would the new process improve on that?

Flexible phones? (1)

chronokitsune3233 (2170390) | about 2 years ago | (#42609989)

Seriously? I can understand how that might be one application of a flexible battery, but you'd also need the handset itself to be flexible, meaning all of the plastic covering, the SoC and any buttons, assuming it had any like volume adjustment buttons and a power button, would need to be flexible too (not just the battery).
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