Flexible, non-cytotoxic battery concept. Optical images of an intra-oral implantable device that relies on millimeter-sized flexible, biocompatible lithium-ion battery as a rapid powering solution. (© Nature Publishing Group)
Researchers have demonstrated a novel approach toward smart orthodontics based on near-infrared red light from a mechanically flexible LED powered by flexible bio-safe batteries all integrated in a single 3D-printed dental brace.
|As the team from King Abdullah University of Science and Technology (KAUST) demonstrates in their paper in NPJ Flexible Electronics (“Flexible and biocompatible high-performance solid-state micro-battery for implantable orthodontic system”), integration of red light therapy enhances bone regeneration, reducing overall time to wear the dental brace and unburdening users from expense. Furthermore, 3D printing allows personalized (instead of one size fits all) transparent dental brace.|
|“Integration of electronic devices in 3D printed dental aligners, as we have demonstrated here, is a pragmatic approach towards implementing a flexible electronic technology in personalized advanced healthcare, particularly in orthodontics,” Muhammad Mustafa Hussain, an Associate Professor of Electrical Engineering at KAUST, tells Nanowerk. ” The next stage of our work will be to demonstrate diagnostics in the smart dental brace in which sensors are able to detect the pressure exerted by aligners on teeth. This might help orthodontists estimate the force required by aligners; thus providing both diagnostic and treatment capabilities in dental braces. “|
|The scientific core of the team’s findings is to approach flexible energy storage solutions in a way that is pragmatic, fast and well integrated with other components. A major challenge to integrate any traditional lithium-based energy storage is their toxicity. The scientists circumvented this issue by introducing non-toxic micro-scale flexible batteries to be used as on-demand power supply.|
|Furthermore, they integrated near-infrared (NIR) capability as well as an optoelectronic system of light emitting diodes (LED) arrays in a personalized, 3D-printed semi-transparent dental brace. Of course, such a device would not have been possible without an appropriate energy storage solution.|
|Key to this smart brace is the use of a high-performance flexible solid-state microbattery. A standalone all thin-film lithium-ion battery already can be readily thinned down to about 30 microns thickness to achieve flexibility. The team’s flexing process for thin-film-based micro-batteries achieves two major objectives: 1) utilization of mature and reliable CMOS process with 90% yield and repeated electrochemical measurements on multiple devices, and 2) the ability to withstand high annealing temperatures of cathode material or soldering that are unachievable using direct film deposition on plastic substrates.|
|“Our flexile biocompatible lithium-ion battery can be transferred on polyethylene terephthalate (PET) and interconnected via aluminum engraved interconnections to create a battery module,” explains Hussain. “During testing we found that the battery module exhibits minimal strain while most of the stress is experienced by the PET film.”|
|Continuous intra-oral NIR light therapy for patients is becoming a growing necessity for accelerating the rate of the bone remodeling process. Near-infrared light can be absorbed by bone cells to stimulate the bone regeneration for faster orthodontic treatment.|
|That’s why the team integrated near-infrared LEDs with the flexible batteries and interconnected them on a soft PET substrate. The whole device is embedded in semi-transparent 3D-printed brace.|
|To summarize, this smart dental brace relies on two main functionalities: Firstly, a customizable, personalized, and semitransparent brace, which provides required external loading to stimulate healthy rebuilding of bone structures. Secondly, a miniaturized, soft, biocompatible optoelectronic system for an intraoral (conformable on the mouth) near-infrared light therapy, which allows rapid, temporally specific control of osteogenic cell activity via targeted exposure and light sensitive proteins present in bone cells.|
|“The combination of both strategies in one single platform provides affordable, multifunctionality dental braces,” concludes Hussain. “Such capability enhances the bone regeneration significantly and reduces the overall cost and discomfort. Our future work will include integration of compliant soft-substrate-based LEDs and miniaturized ICs with enhanced wireless capability for smart gadget-based remote control for cleaning and therapy.”
@ Michael Berger © Nanowerk
Molecular models shows the initial state of battery chemistry that leads to instability in a test cell featuring a magnesium anode
Rechargeable batteries based on magnesium, rather than lithium, have the potential to extend electric vehicle range by packing more energy into smaller batteries. But unforeseen chemical roadblocks have slowed scientific progress.
And the places where solid meets liquid – where the oppositely charged battery electrodes interact with the surrounding chemical mixture known as the electrolyte – are the known problem spots.
Now, a research team at the U.S. Department of Energy’s Joint Center for Energy Storage Research, led by scientists at Lawrence Berkeley National Laboratory (Berkeley Lab), has discovered a surprising set of chemical reactions involving magnesium that degrade battery performance even before the battery can be charged up.
The findings could be relevant to other battery materials, and could steer the design of next-generation batteries toward workarounds that avoid these newly identified pitfalls.
The team used X-ray experiments, theoretical modeling, and supercomputer simulations to develop a full understanding of the chemical breakdown of a liquid electrolyte occurring within tens of nanometers of an electrode surface that degrades battery performance. Their findings are published online in the journal Chemistry of Materials (“Instability at the Electrode/Electrolyte Interface Induced by Hard Cation Chelation and Nucleophilic Attack”).
The battery they were testing featured magnesium metal as its negative electrode (the anode) in contact with an electrolyte composed of a liquid (a type of solvent known as diglyme) and a dissolved salt, Mg(TFSI)2.
While the combination of materials they used were believed to be compatible and nonreactive in the battery’s resting state, experiments at Berkeley Lab’s Advanced Light Source (ALS), an X-ray source called a synchrotron, uncovered that this is not the case and led the study in new directions.
These molecular models show the initial state of battery chemistry that leads to instability in a test cell featuring a magnesium (Mg) anode. (Credit: Berkeley Lab)
“People had thought the problems with these materials occurred during the battery’s charging, but instead the experiments indicated that there was already some activity,” said David Prendergast, who directs the Theory of Nanostructured Materials Facility at the Molecular Foundry and served as one of the study’s leaders.
“At that point it got very interesting,” he said. “What could possibly cause these reactions between substances that are supposed to be stable under these conditions?”
Molecular Foundry researchers developed detailed simulations of the point where the electrode and electrolyte meet, known as the interface, indicating that no spontaneous chemical reactions should occur under ideal conditions, either. The simulations, though, did not account for all of the chemical details.
“Prior to our investigations,” said Ethan Crumlin, an ALS scientist who coordinated the X-ray experiments and co-led the study with Prendergast, “there were suspicions about the behavior of these materials and possible connections to poor battery performance, but they hadn’t been confirmed in a working battery.”
Commercially popular lithium-ion batteries, which power many portable electronic devices (such as mobile phones, laptops, and power tools) and a growing fleet of electric vehicles, shuttle lithium ions – lithium atoms that become charged by shedding an electron – back and forth between the two battery electrodes. These electrode materials are porous at the atomic scale and are alternatively loaded up or emptied of lithium ions as the battery is charged or discharged.
In this type of battery, the negative electrode is typically composed of carbon, which has a more limited capacity for storing these lithium ions than other materials would.
So increasing the density of stored lithium by using another material would make for lighter, smaller, more powerful batteries. Using lithium metal in the electrode, for example, can pack in more lithium ions in the same space, though it is a highly reactive substance that burns when exposed to air, and requires further research on how to best package and protect it for long-term stability.
Magnesium metal has a higher energy density than lithium metal, meaning you can potentially store more energy in a battery of the same size if you use magnesium rather than lithium.
Magnesium is also more stable than lithium. Its surface forms a self-protecting “oxidized” layer as it reacts with moisture and oxygen in the air. But within a battery, this oxidized layer is believed to reduce efficiency and shorten battery life, so researchers are looking for ways to avoid its formation.
To explore the formation of this layer in more detail, the team employed a unique X-ray technique developed recently at the ALS, called APXPS (ambient pressure X-ray photoelectron spectroscopy). This new technique is sensitive to the chemistry occurring at the interface of a solid and liquid, which makes it an ideal tool to explore battery chemistry at the surface of the electrode, where it meets the liquid electrolyte.
Simulations show the weakening of a bond in a liquid solvent due to the presence of free-floating hydroxide ions, which contain a single oxygen atom bound to a hydrogen atom. In this illustration, atoms are color-coded: hydrogen (white), oxygen (red), carbon (light blue), magnesium (green), nitrogen (dark blue), sulfur (yellow), fluorine (brown). This process degrades battery performance. (Credit: Berkeley Lab)
Even before a current was fed into the test battery, the X-ray results showed signs of chemical decomposition of the electrolyte, specifically at the interface of the magnesium electrode. The findings forced researchers to rethink their molecular-scale picture of these materials and how they interact.
What they determined is that the self-stabilizing, thin oxide surface layer that forms on the magnesium has defects and impurities that drive unwanted reactions.
“It’s not the metal itself, or its oxides, that are a problem,” Prendergast said. “It’s the fact you can have imperfections in the oxidized surface. These little disparities become sites for reactions. It feeds itself in this way.”
A further round of simulations, which proposed possible defects in the oxidized magnesium surface, showed that defects in the oxidized surface layer of the anode can expose magnesium ions that then act as traps for the electrolyte’s molecules.
If free-floating hydroxide ions – molecules containing a single oxygen atom bound to a hydrogen atom that can be formed as trace amounts of water react with the magnesium metal – meet these surface-bound molecules, they will react.
This wastes electrolyte, drying out the battery over time. And the products of these reactions foul the anode’s surface, impairing the battery’s function.
It took several iterations back and forth, between the experimental and theoretical members of the team, to develop a model consistent with the X-ray measurements. The efforts were supported by millions of hours’ worth of computing power at the Lab’s National Energy Research Scientific Computing Center.
Researchers noted the importance of having access to X-ray techniques, nanoscale expertise, and computing resources at the same Lab.
The results could be relevant to other types of battery materials, too, including prototypes based on lithium or aluminum metal. Prendergast said, “This could be a more general phenomenon defining electrolyte stability.”
Crumlin added, “We’ve already started running new simulations that could show us how to modify the electrolyte to reduce the instability of these reactions.” Likewise, he said, it may be possible to tailor the surface of the magnesium to reduce or eliminate some of the unwanted chemical reactivity.
“Rather than allowing it to create its own interface, you could construct it yourself to control and stabilize the interface chemistry,” he added. “Right now it leads to uncontrollable events.”
Source: By Glenn Roberts Jr., Lawrence Berkeley National Laboratory
Scientists have designed a novel silicon-based anode to provide lithium batteries with increased power and better stability.
As the world shifts towards renewable energy, moving on from fossil fuels, but at the same time relying on ever more energy-gobbling devices, there is a fast-growing need for larger high-performance batteries. Lithium-ion batteries (LIBs) power most of our portable electronics, but they are flammable and can even explode, as it happened to a recent model of smartphone. To prevent such accidents, the current solution is to encapsulate the anode — which is the negative (-) electrode of the battery, opposite to the cathode (+) — into a graphite frame, thus insulating the lithium ions. However, such casing is limited to a small scale to avoid physical collapse, therefore restraining the capacity — the amount of energy you can store — of the battery.
Looking for better materials, silicon offers great advantages over carbon graphite for lithium batteries in terms of capacity. Six atoms of carbon are required to bind a single atom of lithium, but an atom of silicon can bind four atoms of lithium at the same time, multiplying the battery capacity by more than 10-fold. However, being able to capture that many lithium ions means that the volume of the anode swells by 300% to 400%, leading to fracturing and loss of structural integrity. To overcome this issue, OIST researchers have now reported in Advanced Science the design of an anode built on nanostructured layers of silicon — not unlike a multi-layered cake — to preserve the advantages of silicon while preventing physical collapse.
This new battery is also aiming to improve power, which is the ability to charge and deliver energy over time.
“The goal in battery technology right now is to increase charging speed and power output,” explained Dr. Marta Haro Remon, first author of the study. “While it is fine to charge your phone or your laptop over a long period of time, you would not wait by your electric car for three hours at the charging station.”
And when it comes to providing energy, you would want your car to start off quickly at a traffic light or a stop sign, requiring a high spike in power, rather than slowly creeping forward. A well-thought design of a silicone-based anode might be a solution and answer these expectations.
The idea behind the new anode in the Nanoparticles by Design Unit at the Okinawa Institute of Science and Technology Graduate University is the ability to precisely control the synthesis and the corresponding physical structure of the nanoparticles. Layers of unstructured silicon films are deposited alternatively with tantalum metal nanoparticle scaffolds, resulting in the silicon being sandwiched in a tantalum frame.
“We used a technique called Cluster Beam Deposition,” continued Dr. Haro. “The required materials are directly deposited on the surface with great control. This is a purely physical method, there are no need for chemicals, catalysts or other binders.”
“We used a technique called Cluster Beam Deposition,” continued Dr. Haro. “The required materials are directly deposited on the surface with great control. This is a purely physical method, there are no need for chemicals, catalysts or other binders.”
The outcome of this research, led by Prof. Sowwan at OIST, is an anode with higher power but restrained swelling, and excellent cyclability — the amount of cycles in which a battery can be charged and discharged before losing efficiency. By looking closer into the nanostructured layers of silicon, the scientists realized the silicon shows important porosity with a grain-like structure in which lithium ions could travel at higher speeds compared to unstructured, amorphous silicon, explaining the increase in power. At the same time the presence of silicon channels along the Ta nanoparticle scaffolds allows the lithium ions to diffuse in the entire structure. On the other hand, the tantalum metal casing, while restraining swelling and improving structural integrity, also limited the overall capacity — for now.
However, this design is currently only at the stage of proof-of-concept, opening the door to numerous opportunities to improve capacity along with the increased power.
“It is a very open synthesis approach, there are many parameters you can play around,” commented Dr. Haro. “For example, we want to optimize the numbers of layers, their thickness, and replace tantalum metal with other materials.”
With this technique paving the way, it might very well be that the solution for future batteries, forecast to be omnipresent in our lives, will be found in nanoparticles.
Material provided by Okinawa Institute of Science and Technology (OIST) Graduate University. Note: Content may be edited for style and length.
- Marta Haro, Vidyadhar Singh, Stephan Steinhauer, Evropi Toulkeridou, Panagiotis Grammatikopoulos, Mukhles Sowwan. Nanoscale Heterogeneity of Multilayered Si Anodes with Embedded Nanoparticle Scaffolds for Li-Ion Batteries. Advanced Science, 2017; 1700180 DOI: 10.1002/advs.201700180
Electric power: When batteries are eco-villains in the production, according to a new report. Photo: Tomas Oneborg / SvD / TT
Huge hopes tied to electric cars as the solution to automotive climate problem. But the electric car batteries are eco-villains in the production. Several tons of carbon dioxide has been placed, even before the batteries leave the factory.
IVL Swedish Environmental Research Institute was commissioned by the Swedish Transport Administration and the Swedish Energy Agency investigated lithium-ion batteries climate impact from a life cycle perspective. There are batteries designed for electric vehicles included in the study. The two authors Lisbeth Dahllöf and Mia Romare has done a meta-study that is reviewed and compiled existing studies.
The report shows that the battery manufacturing leads to high emissions. For every kilowatt hour of storage capacity in the battery generated emissions of 150 to 200 kilos of carbon dioxide already in the factory. The researchers did not study individual bilmärkens batteries, how these produced or the electricity mix they use. But if we understand the great importance of play battery take an example: Two common electric cars on the market, the Nissan Leaf and the Tesla Model S, the batteries about 30 kWh and 100 kWh.
Even when buying the car emissions have already occurred, corresponding to approximately 5.3 tons and 17.5 tons, the batteries of these sizes. The numbers can be difficult to relate to. As a comparison, a trip for one person round trip from Stockholm to New York by air causes the release of more than 600 kilograms of carbon dioxide, according to the UN organization ICAO calculation.
Another conclusion of the study is that about half the emissions arising from the production of raw materials and half the production of the battery factory. The mining accounts for only a small proportion of between 10-20 percent.
The calculation is based on the assumption that the electricity mix used in the battery factory consists of more than half of the fossil fuels. In Sweden, the power production is mainly of fossil-nuclear and hydropower why lower emissions had been achieved.
The study also concluded that emissions grow almost linearly with the size of the battery, even if it is pinched by the data in that field. It means that a battery of the Tesla-size contributes more than three times as much emissions as the Nissan Leaf size. It is a result that surprised Mia Romare.
– It should have been less linear as the electronics used is not increased to the same extent. But the battery cells are so sensitive as production looks today, she says.
– One conclusion is that you should not run around with unnecessarily large batteries, says Mia Romare
The authors emphasize that a large part of the study has been about finding out what data is available and find out what quality they are. They have in many cases been forced to conclude that it is difficult to compare existing studies together.
We’ve been frustrated, but it is also part of the result, says Lisbeth Dahllöf.
His colleague, Mats-Ola Larsson at IVL has made a calculation of how long you have to drive a petrol or diesel before it has released as much carbon dioxide as battery manufacturing has caused. The result was 2.7 years for a battery of the same size as the Nissan Leaf and 8.2 years for a battery of the Tesla-size, based on a series of assumptions (see box below).
– It’s great that companies and authorities for ambitious environmental policies and buying into climate-friendly cars. But these results show that one should consider not to choose an electric car with a bigger battery than necessary, he says, noting that politicians should also take this on in the design of instruments.
An obvious part to look at the life cycle analysis is recycling. The authors note that the characteristics of the batteries is the lack of the same, since there is no financial incentive to send batteries for recycling, as well as the volumes are still small.
Cobalt, nickel and copper are recovered but not the energy required to manufacture electrodes, says Mia Romare and points out that the point of recycling the resource rather than the reduction of carbon emissions.
Peter Kasche the report originator Energy Agency emphasizes the close of the linear relationship between the battery size and emissions is important.
– Somehow you really get to see so as to optimize the batteries. One should not run around with a lot of kilowatt hours unnecessarily. In some cases, a plug-in hybrid to be the optimum, in other cases a clean vehicle battery.
So counted IVL
Mats-Ola Larsson has made a number of assumptions in the calculation of emissions from a battery of the Nissan Leaf size and a battery of Tesla’s size takes 2.7 and 8.2 years to “run together into” a normal petrol or diesel:
The average emissions of new Swedish cars in 2016 were 126 grams of carbon dioxide per kilometer. The value has been adjusted to 130 because some of the cars that are classified as electric vehicles are plug-in hybrids, which sometimes runs on fossil fuels.
While adoption of petrol and diesel have 18 percent renewable fuels, which affect emissions.
Average Mileage per year is 1224 mil under Traffic Analysis.
Recently, Researchers in Tsinghua University have proposed a nitrogen-doped graphene matrix with densely and uniformly distributed lithiophilic functional groups for dendrite-free lithium metal anodes, appearing in the journal Angewandte Chemie International Edition.
Since lithium metal possesses an ultrahigh theoretical specific capacity (3860 mAh g-1) and the lowest negative electrochemical potential (-3.040 V vs. the standard hydrogen electrode), lithium metal has been regarded as the most promising electrode material for next-generation high-energy-density batteries. However, the application of lithium metal batteries is still not in sight. “Lithium dendrite growth has hindered the development of lithium metal anodes,” said Dr. Qiang Zhang, the corresponding author, a faculty at Department of Chemical Engineering, Tsinghua University. “Lithium dendrites that form during repeated lithium plating and stripping cycles can not only induce many ‘dead Li’ with irreversible capacity loss, but also cause internal short circuits in batteries and other hazardous issues.”
“We found that a lithiophilic material with good metallic lithium affinity can guide the lithium metal nucleation. Therefore, designing a lithium-plating matrix with a high surface area and lithiophilic surface makes sense for a safe and efficient lithium metal anode,” said Xiao-Ru Chen, an undergraduate student in Tsinghua University. “So we employed a nitrogen-doped graphene matrix with densely and uniformly distributed nitrogen containing functional groups to guide lithium metal nucleation and growth.”
“The nitrogen containing functional groups are lithiophilic sites, confirmed by our experimental and DFT calculation results. Lithium metal can plate with uniform nucleation during the charging process, followed by growth into dendrite-free morphology. While on the normal Cu foil-based anode, the nucleation sites are scattered, which may cause lithium dendrite growth more easily,” said Xiang Chen, a Ph.D. student at Tsinghua University.
With the lithiophilic nitrogen-containing functional groups, the N-doped graphene matrix can regulate the nucleation process of lithium electrodeposition. As a result, dendrite-free lithium metal deposits were obtained. Additionally, this matrix shows impressive electrochemical performance. The Coulombic efficiency of the N-doped graphene-based electrode at a current density of 1.0 mA cm-2 and a cycle capacity of 1.0 mAh cm-2 can reach 98 percent for nearly 200 cycles.
“We have proposed a new strategy based on lithiophilic site-guided nucleation to settle the tough dendrite challenge in this publication,” said Qiang. “Further research is required to investigate and control the lithium nucleation in lithium metal batteries. We believe that the practical application of lithium metal anodes can be finally realized.” The control of the nucleation process of lithium plating with a lithiophilic matrix has shed a new light on all lithium metal-based batteries, such as Li-S, Li-O2 and future Li-ion batteries.
Explore further: New battery coating could improve smart phones and electric vehicles
More information: Rui Zhang et al. Lithiophilic Sites in Doped Graphene Guide Uniform Lithium Nucleation for Dendrite-Free Lithium Metal Anodes, Angewandte Chemie International Edition (2017). DOI: 10.1002/anie.201702099
NREL’s Agreement with Forge Nano helps fundamentally enhance lithium-ion battery safety, durability, and lifetime
The U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) has entered into an exclusive license agreement with Forge Nano to commercialize NREL’s patented battery materials and systems capable of operating safely in high-stress environments. A particular feature of the technology is the encapsulation of materials with solid electrolyte coatings that can be designed to meet the increasingly demanding needs of any battery application.
These lithium-ion batteries feature a hybrid solid-liquid electrolyte system, in which the electrodes are coated with a solid electrolyte layer. This layer minimizes the potential for the formation of an internal short circuit between electrodes to prevent “thermal runaway,” or the uncontrolled increase in battery cell temperature that can result in a fire or an explosion.
In addition, coating of the electrode materials reduces the stress on traditional polymer separators that are currently necessary components in commercial lithium-ion batteries and can allow for thinner separators designed for higher power devices. This advancement has the potential to reduce both the cost and weight of the battery device, while substantially increasing safety and lifetime.
Lab-scale testing of NREL’s hybrid solid-liquid electrolyte system has shown increased electrode durability and reliability without compromised electrochemical performance. “The cells are less likely to fail, even in demanding, real-world conditions like high temperatures and fast recycle rates,” said Ahmad Pesaran, whose team of engineers in NREL’s Energy Storage group invented the technology.
Forge Nano, formerly PneumatiCoat Technologies, is a Colorado-based company specializing in the scale-up and manufacturing of cost-effective Atomic Layer Deposition (ALD) encapsulated materials. Forge Nano presented its technology at the 2013 and 2017 NREL Industry Growth Forum, the nation’s premier clean energy investment event. A year later, NREL approached the company as a potential licensee after conducting a licensee search in the battery technology area.
“This license agreement will allow Forge Nano to offer further customized lithium-ion battery materials for high performance devices by utilizing our patented high-throughput ALD system that has already been successfully tested at the pilot scale and in large format pouch cells,” Paul Lichty, CEO of Forge Nano, said. “The incorporation of this technology into Forge Nano’s offering will lead to a substantial reduction in cost per unit energy of lithium-ion batteries.”
NREL has more than 800 technologies available for licensing. Companies interested in partnering to advance research on or commercialize renewable energy technologies can visit the EERE Energy Innovation Portal, which features descriptions of all renewable energy technologies funded by the Department of Energy’s Office of Energy Efficiency and Renewable Energy.
NREL is the U.S. Department of Energy’s primary national laboratory for renewable energy and energy efficiency research and development. NREL is operated for the Energy Department by The Alliance for Sustainable Energy, LLC.
Visit NREL online at www.nrel.gov
To learn more about Forge Nano visit: Forge Nano
- Lithium-Ion battery inventor 94 year old John Goodenough has stumped researchers evaluating his recent discovery and resulting claims.
- Greater Energy Density
- Faster/ Rapid Re-Charging
- SAFE! Non-Exploding
- Low Cost Materials
- Low Cost to Manufacture
Is the discovery the answer to much needed Energy Storage for Renewable Energies? The Electric Vehicle (EVs) ?
Watch the Video and tell us what you think? Leave us your Comments!
The electrode in lithium-ion (Li-ion) batteries is an integrated system in which both active materials and binder systems play critical roles in determining its final properties. In order to improve battery performance, a lot of research is focusing on the development of high-capacity active materials. However, without an efficient binder system, these novel materials can’t fulfill their potentials.
A group of researchers now has contributed to this field from a slight different aspect, developing a high-performance and general binder system for batteries. This entirely new binder system with a nano-architecture promotes both electron and ion transport, which enhances the energy per unit mass and volume of the electrode.This work by Guihua Yu group at University of Texas at Austin and Esther Takeuchi group at Stony Brook University, demonstrates a new generation of nanostructured conductive polymer gel based novel binder materials for fabrication of high-energy lithium-ion battery electrodes.
This gel framework could become a next-generation binder system for commercial Li-ion batteries.”Compared to conventional binder system which typically consists of conductive additive and polymer binder, our novel binder plays dual functionalities simultaneously combining conductive and adhesive features, thus greatly improving the better utility of active electrode materials,”Professor Yu tells Nanowerk.
“More importantly, owing to its unique 3D network structure, this gel binder promotes both electron and ion transport in electrode and improves the distribution of active particles, thus enhancing the rate performance and cycle life of battery electrodes.”He points out that this invention is important because it presents a new generation of powerful yet scalable binder materials for lithium ion batteries that show great potential in industrial manufacturing.This novel gel binder can overcome the drawbacks of conventional binder systems, leading to next-generation lithium ion battery with high performance.
The researchers have reported their findings in two papers in Nano Letters (“Nanostructured Conductive Polymer Gels as a General Framework Material To Improve Electrochemical Performance of Cathode Materials in Li-Ion Batteries”) and Advanced Materials (“A Tunable 3D Nanostructured Conductive Gel Framework Electrode for High-Performance Lithium Ion Batteries”).
Schematic of synthetic and structural features of commercial lithium iron phosphate (C-LFP)/cross-linked polypyrrole (C-PPy) hybrid gel framework. The conductive polymer chains can be polymerized in situ with electrode materials and cross-linked by molecules with multiple functional groups, resulting in a polymeric network connecting all active particles. (Reprinted with permission by American Chemical Society) (click on image to enlarge)
“A traditional binder system in Li-ion battery electrodes is a binary hybrid with components acting separate functionalities,” explains Yu. “In such system, polymer binders such as polyvinylidene fluoride (PVDF) adhere the active materials and other additives together to hold the mechanical integrity while a conductive additive (usually carbon particles) ensures the conductivity of the entire electrode.”In these electrodes, electrons transport through chains of particles while ions move through the liquid or solid electrolyte that fills the pores of the electrode.
However, the conductive phases are randomly distributed, which may lead to bottlenecks and poor contacts that impede effective access to parts of the battery.And both organic and inorganic components tend to aggregate, which also negatively impact electron and ion transport.The team’s novel conductive gel binder can overcome these drawbacks and thus improve the rate and cyclic performance of Li-ion batteries.
The conductive polymer gels potentially could also be used for responsive/smart electronics such as biosensors, artificial skins and soft robotics.The scientific core of this work is that three-dimensional nanostructured conductive polymer gels can be built up by tunable molecule crosslinking and this unique conductive framework material can promote the electron/ion transport within battery electrodes.
“Firstly, our work provides a new method for synthesis of conductive polymer gel,” elaborates Yu. “Traditionally, conductive polymer gels are synthesized by template-based method, which usually results in low conductivity and poor mechanical properties. The method we developed is to crosslink conductive polymer chains with functional molecules with multiple functional groups, enabling a network, interconnected structure promoting high electronic conductivity and electrochemical activity.”
“Secondly, we demonstrated that this newly developed conductive polymer gel can be used as binder system and significantly improve conventional lithium-ion battery performance owing to their advantageous structural features,” he continues. “The ease of processability and excellent chemical and physical properties of these nanostructured conductive gels enable a new class of binder materials for fabricating next-generation high-energy lithium-ion batteries.”Although the researchers’ binder gel is mechanically strong, it lacks flexibility and stretchability.
The plan is to further modify the mechanical properties by tailoring the molecular backbones of conductive polymers through the addition of side chains or other building block polymers.The scientists further intend to demonstrate the versatility of their gel binders for other important electrode materials, such as some commercial electrode materials, as well as some next-generation ultrahigh-capacity materials, such as silicon, and sulfur.
by Michael Berger @ Nanowerk