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IONICS

Integration and Optimization of Novel Ion-Conducting Solids

Today's growing demand for electricity from carbon-free, renewable resources and for alternatives to petroleum as a transportation fuel has led to a strong desire for cost-effective and durable energy storage and conversion products. The projects that make up ARPA-E's IONICS program, short for "Integration and Optimization of Novel Ion-Conducting Solids," are paving the way for technologies that overcome the limitations of current battery and fuel cell products by creating high performance separators and electrodes built with solid ion conductors. The program will focus on developing new processing methods and approaches to device integration to accelerate devices built with high performance ion-conducting solids to commercial deployment.
For a detailed technical overview about this program, please click here.    

24M Technologies

Large-Area Lithium Electrode Sub-Assemblies (LESAs) Protected by Self-Forming Microstructured Polymer-Inorganic Single-Ion Conducting Composites

24M Technologies will lead a team to develop low cost, durable, enhanced separators/solid state electrolytes to build batteries using a lithium metal anode. Using a polymer/solid electrolyte ceramic blend, 24M will be able to make a protective layer that will help eliminate side reactions that have previously contributed to performance degradation and provide a robust mechanical barrier to branchlike metal fibers called dendrites. Unimpeded, dendrites can grow to span the space between the negative and positive electrodes, causing a short-circuit. The resulting, large-area lithium electrode sub-assemblies, or LESAs, will be cost-effective solutions that are scalable to high-volume manufacturing while providing a toolbox to further tailor electrode performance.

3M

Low Cost, Durable Anion Exchange Membranes

3M will develop a new anion exchange membrane (AEM) technology with widespread applications in fuel cells, electrolyzers, and flow batteries. Unlike many proton exchange membrane (PEM) applications, the team's AEM will operate in an alkaline environment, which means lower-cost electrodes can be used. The team plans to engineer a membrane that simultaneously meets key goals for resistance, mechanical and chemical stability, and cost. They will do this by focusing on simple, hydroxide-stable polymers, such as polyethylene, and stable cations, such as tetraalkylammonium and imidazolium groups. Positively-charged cation side chains attached to the polymer backbone will facilitate passage of hydroxide ions through the electrolyte, resulting in enhanced ionic conductivity. The proposed polymer chemistry is envisioned to be low cost and can be used in alkaline environments, and can be processed into mechanically robust membrane composites. This membrane technology has the potential to enable high volume, low-cost production of AEMs. The impact of this project can be transformational as the commercial availability of high-quality AEMs has been a limiting factor in developing AEM-based devices.

American Manufacturing, Inc.

Flash Sintering System for Manufacturing Ion-Conducting Solids

American Manufacturing, in collaboration with the University of Colorado at Boulder, will develop a flash sintering system to manufacture solid lithium-conducting electrolytes with high ionic conductivity. Conventional sintering is the process of compacting and forming a solid mass by heat and/or pressure without melting it to the point of changing it to a liquid, similar to pressing a snowball together from loose snow. In conventional sintering a friable ceramic "bisque" is heated for several hours at very high temperatures until it becomes dense and strong. Oxide ceramics for solid-state electrolytes have high melting points, and some are chemically stable and do not react with lithium metal, which can reduce cost and maximize energy density. But the sintering process requires several hours at very high temperatures (1100°C). These conditions conflict with the fast movement of lithium atoms in the solid state, which is a key property of the electrolyte. Therefore, the manufacture of these electrolytes by the conventional sintering process is a key barrier to their cost and viability. In contrast, flash sintering can occur in fewer than 5 seconds, at temperatures below 800°C, and can prevent the loss of lithium experienced in conventional sintering. This project is expected to improve lithium battery technology in the following ways: lowering the cost of sintering and processing; enhancing productivity through roll-to-roll manufacturing of co-sintered multilayers ready to be inserted into devices; and hastening the discovery of new materials by shortening the time between synthesis of new chemistries and their electrochemical evaluation to days instead of months.

Colorado School of Mines

Hybrid Polyoxometalate Membranes for High Proton Conduction with Redox Ion Exclusion

The Colorado School of Mines will develop a new membrane for redox flow battery systems based on novel, low-cost materials. The membrane is a hybrid polymer that includes heteropoly acid molecules and a special purpose fluorocarbon-based synthetic rubber called a fluoroelastomer. The team will enhance the membrane's selectivity by refining the polymer structure, employing crosslinking techniques, and also through doping the polymer with cesium. The fluoroelastmer is commercially available, thereby contributing to a superior performance-to-cost ratio for the membrane. Flow battery experts at Lawrence Berkeley Laboratory will extensively test the selectivity, conductivity, and stability of the membranes developed in this project, and 3M will apply its decades of membrane fabrication experience to scale-up the new technology. If successfully developed, the separator in this project will increase efficiency and reduce cost in existing flow battery systems such as the all-iron redox flow battery.

Ionic Materials

Novel Polymer Electrolyte for Solid State Lithium Metal Battery Technology

Ionic Materials will develop a lithium metal (not lithium ion) rechargeable battery cell that employs a novel solid polymer electrolyte that enables the world's first truly safe lithium metal rechargeable battery cell. Scientists at the City University of New York have found that Ionic Material's proprietary ionic conducting polymer is the most highly lithium conducting solid state polymer material ever measured (at room temperature). This polymer has high ionic conductivity across a range of temperatures, can be reliably extruded into very thin films, is non-flammable, has attractive mechanical properties, and is compatible with a variety of different anodes and cathodes, including lithium metal. This polymer also has the potential to address a number of challenges associated with lithium metal anodes, including electrochemical stability and the ability to cycle without the growth of branchlike metal fibers called dendrites. If left unimpeded, dendrites can grow to span the space between the negative and positive electrodes, causing short-circuiting. Ionic Materials' polymer electrolyte will eliminate the risk of battery shorting due to dendrites, and speed the safe implementation of solid-state, lithium metal anode batteries. Such cells are of particular interest due to their extremely high specific energy (400 Wh/kg or more versus 285 Wh/kg for the best Li-Ion cells today) and their potential to reduce cell costs below $100/kWh, a commonly cited tipping point for the mass adoption of electric vehicles.

Iowa State University

Strong, High Li+ Ion Conductivity, Li-Impermeable Thin-Ribbon Glassy Solid Electrolytes

Iowa State University (ISU) will develop new lithium-ion-conducting glassy solid electrolytes to address the shortcomings of present-day lithium batteries. The electrolytes will have high ionic conductivities and excellent mechanical, thermal, chemical, and electrochemical properties. Because glasses lack grain boundaries, they will also be impermeable to lithium dendrites, branchlike metal fibers that can short-circuit battery cells. These glassy solid electrolytes can enhance the safety, performance, manufacturability, and cost of lithium batteries. In addition to the electrolyte development, the team will build a micro-sheet glass ribbon processing facility and optimize conditions to identify a composition that will enable low-cost fabrication. Roll-to-roll manufacturing of the long, ribbon micro-sheets could be used to mass-produce enormous volumes of lithium batteries at very low cost and in flexible, stacked-layer formats.

Oak Ridge National Laboratory

Metastable And Glassy Ionic Conductors (MAGIC)

Oak Ridge National Laboratory (ORNL) will develop glassy Li-ion conductors that are electrochemically and mechanically stable against lithium metal and can be integrated into full battery cells. Metallic lithium anodes could significantly improve the energy density of batteries versus today's state-of-the-art lithium ion cells. ORNL has chosen glass as a solid barrier because the lack of grain boundaries in glass mitigates the growth of branchlike metal fibers called dendrites, which short-circuit battery cells. The team aims to identify a glassy electrolyte with high conductivity, explore novel and cost-effective ways to fabricate this thin glass electrolyte, and design electrolyte membranes that are sufficiently robust to prevent cracking and degradation during battery fabrication and cycling. Advanced glass processing using rapid quench methods will enable a range of compositions and microstructures as well as their cost-effective fabrication as thin, dense membranes. In addition to glass composition, a range of membrane designs will be investigated by modeling and experiment. For efficient battery fabrication, the glassy membrane will likely require mechanical support and protection, which could be achieved by employing polymers or ceramic layers as a support.

Pennsylvania State University

Cold Sintering Composite Structures for Solid Lithium Ion Conductors

Pennsylvania State University (Penn State) will develop a process for cold-sintering of ceramic ion conductors below 200°C to achieve a commercially viable process for integration into batteries. Compared to liquid electrolytes, ceramics and ceramic composites exhibit various advantages, such as lower flammability, and larger electrochemical and thermal stability. One challenge with traditional ceramics is the propagation of lithium dendrites, branchlike metal fibers that short-circuit battery cells. Penn State will create ceramic and ceramic/polymer composite electrolytes that resist dendrite growth by creating optimized microstructures via cold sintering. Sintering is the process of compacting and forming a solid mass by heat and/or pressure without melting it to the point of changing it to a liquid, similar to pressing a snowball together from loose snow. However, the high temperature required for traditional sintering of ceramics limits opportunities for integration in electrochemical systems and leads to high processing costs. Cold-sintering below 200°C changes the ability to control grain boundaries within ceramic materials, creates opportunities to tune interfaces, and opens the door for integration of different materials. It also allows large area co-processing of organic and inorganic materials in a one-step process, leading to savings in fabricating costs by eliminating the separate ceramic sintering steps and high-temperature processing.

PolyPlus Battery Company

Flexible Solid Electrolyte Protected Lithium Metal Electrodes for Next Generation Batteries

PolyPlus Battery Company, in collaboration with SCHOTT Glass, will develop flexible, solid-electrolyte-protected lithium metal electrodes made by the lamination of lithium metal foil to thin solid electrolyte membranes that are highly conductive. Past efforts to improve lithium cycling by moving to solid-state structures based on polycrystalline ceramics have found limited success due to initiation and propagation of dendrites, which are branchlike metal fibers that short-circuit battery cells. A major benefit of the PolyPlus concept is that the lithium electrode is bonded to a "nearly flawless" glass surface which is devoid of grain boundaries or sufficiently large surface defects through which dendrites can initiate and propagate. These thin and flexible solid electrolyte membranes will be laminated to lithium metal foils, which can then be used to replace the graphite electrode and separators in commercial Li-ion batteries. The team's approach is based on electrolyte films made by commercial melt processing techniques, and they will work in close cooperation to develop compositions and processes suitable for high-volume, low-cost production of the lithium/glass laminate. The SCHOTT team will focus on glass composition and its relationship to physical properties while the PolyPlus team will determine electrochemical properties of the glass and provide this information to SCHOTT to further refine the glass composition. PolyPlus will also develop the Li/glass lamination process and work with the SCHOTT team on manufacturing and scale-up using high volume roll-to-roll processing.

Rensselaer Polytechnic Institute

Channeling Engineering of Hydroxide Ion Exchange Polymers and Reinforced Membranes

Rensselaer Polytechnic Institute (RPI) will develop hydroxide ion-conducting polymers that are chemically and mechanically stable for use in anion exchange membranes (AEM). Unlike PEMs, AEMs can be used in an alkaline environment and can use inexpensive, non-precious metal catalysts such as nickel. Simultaneously achieving high ion conductivity and mechanical stability has been a challenge because high ion exchange capacity causes swelling, which degrades the system's mechanical strength. To solve this problem, the team plans to decouple the structural units of the AEM that are responsible for ion conduction and mechanical properties, so that each can contribute to the overall properties of the AEM. The team will also use channel engineering to provide a direct path for ion transport, with minimal room for water, in order to achieve high ion conductivity with low swelling. If successful, the team hopes to create a pathway to the first commercial hydroxide ion exchange membrane products suitable for electrochemical energy conversion technologies.

Sila Nanotechnologies, Inc.

Melt-Infiltration Solid Electrolyte Technology for Solid State Lithium Batteries

Sila Nanotechnologies will develop solid-state ceramic lithium batteries with high energy density. Traditional methods using ceramic electrolytes significantly reduces a battery's volumetric energy density because the materials are relatively bulky. Commercially produced separator membranes are also expensive and thick because of challenges in fabrication and handling of thinner, defect-free solid-state electrolyte membranes. In addition, such membranes are often air sensitive, have low ionic conductivity, and are susceptible to the growth of branchlike metal fibers called dendrites. Unimpeded, dendrites can grow to span the space between the negative and positive electrodes, causing short-circuiting. To overcome these limitations the team proposes a shift in solid-state battery technology: melt-infiltrating of a solid-state electrolyte at moderate temperatures into a porous separator-cathode stack. This reduces cell volume by nearly three times, while resulting in a corresponding increase in energy density and cost-reduction. The result is a product with low cost and high production yield, built on a process similar to conventional organic electrolyte-filling techniques. The equipment for this process will be very similar to what is currently used in Li-ion battery manufacturing, except that it will be slightly modified for operation at elevated temperatures of up to 250-400°C. The use of equipment similar to what is currently used by industry will reduce the risks of technology scale-up.

United Technologies Research Center

Synergistic Membranes And Reactants for a Transformative Flow Battery System (SMART FBS)

United Technologies Research Center (UTRC) will develop a redox flow battery system that combines next-generation reactants with an inexpensive and highly selective membrane. This SMART-FBS project addresses the two highest cost components in redox flow battery systems: reactants and membranes. The team plans to develop these two components simultaneously using core materials that will work in tandem. Polymer membranes will be developed that include benzimidazole or pyridine structures; ionic conductivity will come from the membrane's structure that allows acid to be imbibed into the polymer. This approach will allow for the use of a low-cost polymer that is durable, selective, and highly conductive. The new reactants will be large organic molecules based upon an extensive theoretical library of potential reactants that has already been established. Multiple membranes and reactants enable a variety of technology options, which should increase the likelihood of success. The project integrates and leverages benefits from each of the team members including: UTRC's state-of-the-art redox flow battery cell performance; innovations in membranes from the University of South Carolina; TPS polymers and membrane-manufacturing capabilities of Advent Technologies; novel active materials based on Harvard University's large library of organic reactants; and Lawrence Berkley National Laboratory's proficiency in characterizing and modeling transport in ion-exchange membranes. If successful, the team's innovations will enable widespread deployment of redox flow batteries for grid-scale electrical energy storage.

University of California, San Diego

Self-Forming Solid-State Batteries

The University of California, San Diego (UC San Diego), in partnership with Liox Power and the University of Maryland, will develop a self-forming, high temperature solid-state lithium battery that solves the critical cost and performance problems impeding commercialization of solid-state batteries for electric vehicles. The battery will possess a very long life due to a chemical mechanism that repairs cycling damage automatically. This self-healing electrolyte will also limit the growth of dendrites. Dendrites are branchlike metal fibers that can grow to span the space between the negative and positive electrodes, thereby causing a short circuit. The team plans to reduce costs by designing a manufacturing process for forming solid-state electrolytes and cathodes in a single step by depositing a graded lithium/phosphorous/sulfur composite material as both the cathode and electrolyte. In theory, this composition should be able to remove any deformations due to dendrite formation by a simple thermal cycling process. A non-flammable polymer used within this composite will both add structural strength and eliminate the need for flammable liquid electrolytes. The team projects that the battery will cost half of current lithium-ion batteries while doubling the energy density.

University of Colorado, Boulder

Anion Channel Membranes

The University of Colorado, Boulder (CU-Boulder) will develop a new type of anion-exchange membrane for chloride (Cl-) transport that is based on a nanoporous lyotropic liquid crystal structure that minimizes cation crossover by molecular size-exclusion and charge exclusion. Due to a lack of suitable Cl- conducting membranes, flow batteries often use microporous membranes or cation-exchange membranes (CEM) to separate the two electrode chambers. Microporous membranes are inexpensive, but do not provide perfect barriers to intermixing of the reactants (or "crossover") that reduces the battery's efficiency and, in some cases, damages critical components. In contrast, CEMs such as Nafion provide better isolation but are far more expensive, and also permit the migration of water and protons which can change the pH (acidity) and lead to inefficiencies and undesired side reactions in the battery. This project aims to develop a low-cost separator that eliminates crossover in all-iron flow batteries. The membrane allows for ion transport via nanochannels, which are engineered to have sizes below those of common hydrated cations, thus exhibiting perfect cation rejection. In the all-iron battery, key benefits of reduced crossover include increased roundtrip efficiency as well as the reduction of pH swings and water transport, and hence the reduction or elimination of the rebalancing stacks and system management schemes. In the future, the membrane developed in this project could also be used with other lower cost redox couples, including those using two different elements as active species. The low cost, increased efficiency, and long lifetime of these membranes have the potential to significantly increase the economic viability of flow batteries.

University of Delaware

Highly Conductive, Stable and Robust Hydroxide Exchange Membranes Based on Polyaryl piperidinium

The University of Delaware (UD) with their project partners will develop a new class of hydroxide exchange membranes (HEMs) for use in electrochemical devices such as fuel cells. Hydroxide exchange membrane fuel cells (HEMFC), in contrast to PEM fuel cells, can use catalysts based on low-cost metals as well as inexpensive membranes and bipolar plates. However, a low-cost HEM that simultaneously possesses adequate ion conductivity, chemical stability, and mechanical robustness does not yet exist. To address this challenge, the team has developed a family of poly(aryl piperidinium) HEMs that are highly hydroxide conductive, chemically stable, and mechanically robust. These polymers will be designed to provide unprecedented chemical stability, while simultaneously enabling high ion-exchange capacities and low swelling ratios, and mechanical robustness. A major part of the team's project will focus on enhancing the mechanical robustness of HEMs under different levels of humidity. The feasibility of roll-to-roll membrane production will be determined as part of the commercialization efforts. The proposed HEMs have the potential to make hydrogen fuel cell vehicles economically competitive with gasoline-powered vehicles. 

Washington University

Reinforced AEM Separators Based on Triblock Copolymers for Electrode-decoupled RFBs

The Washington University team will develop new membrane separators for redox flow batteries using a styrene-ethylene-butylene block copolymer. The team will investigate three types of membrane construction to achieve the high levels of ion selectivity and mechanical stability necessary for use in flow batteries. If needed, the team will also explore the addition of inorganic silica particles in the polymer membrane to enhance selectivity. While many flow batteries utilize proton exchange membrane (PEM) separators that conduct positively-charged ions, the proposed membrane in this project is an anion exchange membrane (AEM) that will conduct negatively-charged ions. An inexpensive, durable AEM will allow for improved efficiency and lower system cost in existing flow battery systems such as the iron-chromium redox flow battery as well as enabling development of new low-cost chemistries.
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