TITLE: Lithium Ion Battery Electrodes Manufacturing to Improve Power and Energy Performance
TECHNOLOGY AREA(S): Materials/Processes
OBJECTIVE: Develop novel electrode materials/designs and manufacturing processes which enable high power and high energy lithium battery performance without the use of flammable/toxic solvents.
DESCRIPTION: The DoD has need for inherently safe energy storage devices with improved high power, high energy density, and low temperature performance to reduce dismounted soldier burden. Current production methods are costly and use flammable/toxic solvents which require personal and infrastructure protective equipment to safeguard personnel and prevent facility fires. Currently the solvent most widely used is N-methyl pyrrolidone (NMP). The electrode materials are mixed with polymer binder and additives and NMP to form a slurry that is spread on a current collector foil and then dried. NMP which is first added to form the slurry and then removed by drying has flammable vapors, necessitating the use of explosion proof equipment, and is toxic. The widely used lithium metal oxide based cathodes and carbon based anodes that result from currently used processes are uniform with a lack of tunability throughout the thickness of the electrode. New multi-layer electrodes manufacturing techniques where the porosity, particle size and active material can be varied throughout the thickness of the electrode structure and do not require the use of flammable/toxic solvents have recently been demonstrated. These new electrodes circumvent the general limitation of lithium ion chemistry which limits cell design to either high power or high energy and these new multi-layer electrodes could enable simultaneous high power and high energy performance. Optimization and scale up of processes that are capable of generating these structured electrodes using conventional and nanoparticles and binders while eliminating the use of flammable/toxic solvents are needed.
PHASE I: Demonstrate and optimize a manufacturing approach to produce multi-layer electrode concept using conventional lithium ion binders and active materials without the use of flammable/toxic solvents. Characterize resulting electrode composition and structure as a function of process conditions. Determine structure property relationships and their impacts on electrochemical performance. Prepare laboratory half cells, perform high power and specific energy testing, and identify degradation processes. Demonstrate results that indicate that a specific energy >200 Wh/kg and specific power >2kW/kg and improved life cycle performance of >400 cycles are possible using multi-layer electrodes produced without using flammable/toxic solvents.
PHASE II: Optimize manufacturing processes and scale up without the use of flammable/toxic solvents. Characterize the impact on cell performance of particle size and active material identity. Prepare full cells with scaled up the processes to produce 3 Ah cells with a specific energy >250 Wh/kg and specific power >4 kW/kg and improved life cycle performance of >800 cycles. Compare battery performance of cell with commercially available batteries. Determine optimized processing conditions, cost model and report commercial viability of production process.
PHASE III DUAL USE APPLICATIONS: Development of devices for both civilian and DoD use. There are many electronic devices used in the military and civilian communities that would benefit from improved energy storage devices such as portable electronics, hybrid vehicles, etc. The reduction of the solvents required for battery production also make this topic relevant for commercial battery producers who have routinely had production issues resulting in fires to reduce production costs and increase safety. The elimination of toxic/flammable solvents will reduce Army battery costs and reduce the environmental impact associated with military battery production.
1. Handbook of Batteries, Third Edition, David Linden. Thomas Reddy, Chapters 2, 3, Sections 35.4, 35.6, 35.90
2. Marco A. Spreafico, Paula Cojocaru, Luca Magagnin, Francesco Triulzi, and Marco Apostolo, “PVDF Latex and a Binder for Positive Electrodes in Lithium-Ion Batteries, Ind. Eng. Chem. Res., 2014, 53 (22), pp 9094–9100
3. Cojocaru, P.; Pieri, R.; Apostolo, M.; Solvay Specialty Polymers Italy S.P.A. Electrodeforming composition, 2013 WO 2013/037692.
4. Jianlin Li, Beth L. Armstrong, Jim Kiggans, Claus Daniel, and David L. Wood, III; “Optimization of LiFePO4 Nanoparticle Suspensions with Polyethyleneimine for Aqueous Processing.” Langmuir, February 28, 2012, Volume 28, Issue 8, pp 3783–3790
KEYWORDS: lithium ion battery, electrodes, solvent, electrode structure
TITLE: Low Cost, Compact, and High Power Terahertz Emitter Arrays with 1550-nm Telecommunications Laser Drivers
TECHNOLOGY AREA(S): Electronics
OBJECTIVE: To develop compact, highly efficient, and high power terahertz emitter arrays driven by low cost, fiber-based 1550-nm telecommunications lasers.
DESCRIPTION: The Terahertz (THz) portion of the electromagnetic spectrum occupies the spectral range from 300 GHz to 3 THz. In the past two decades, exciting applications have emerged in concealed weapon and contraband detection for homeland security, biological-agent and biochemical detection, and biomedical imaging. THz systems also offer unique benefits for communications. Wide bandwidth and high carrier frequency have the potential to support high data rate transmission in small operational platforms. They can also provide secure communication links due to their high directionality for a given compact physical aperture and precisely controlled propagation ranges. All of these applications are highly relevant for the Army and DOD, and potentially enable unprecedented functionalities.
A key factor in the advancement of THz science and technology has been the development of ultrafast photoconductive (PC) devices. They have been implemented as PC photomixers in continuous-wave (CW) frequency-domain systems. The primary PC materials have been low-temperature-grown or heavily-Er-doped GaAs. PC photomixers driven by 800-nm diode lasers have produced narrowband THz output power >1.0 uW. Yet in spite of such impressive performance, these THz systems remain expensive because of the cost of the 800-nm laser drivers. In contrast, the 1550-nm region offers much more affordable laser sources as well as a large array of fiber-based optical components made available by the optical fiber-based telecommunications industry. For example, erbium-doped-fiber amplifier (EDFA) comes in a small, low-cost package and can produce 100 mW output power. THz systems based on PC devices driven by 1550-nm laser sources can significantly reduce system size and overall cost. It can also enable array architectures and therefore provide new functionalities. For this reason 1550-nm PC devices have been under investigation for over a decade. Most of these have been InGaAs based devices, which have suffered from low external responsivity, low resistivity, low breakdown voltage, or some combination thereof. As such, the THz output power from these devices has typically been an order of magnitude or more lower than that from GaAs-based devices at 800 nm.
A number of recent developments, such as ultrafast extrinsic PC effect in ErAs:GaAs and high-mobility InGaAs rare-earth-group-V nanocomposites, have demonstrated promising potential to achieve 1550-nm PC devices at greatly enhanced performance. By utilizing these developments and fiber-based photonic technology, this program will develop THz sources and systems based on PC devices driven by 1550-nm lasers with performance comparable to or better than devices operating at 800 nm but at significantly reduced size and overall cost. In particular, it will focus on developing high power CW THz PC photomixers. It will also include development of a 3X3 array with independently controlled fiber-based drivers to enable beam steering.
PHASE I: Select and characterize suitable PC materials for 1550-nm operation. Relevant material properties should include carrier mobility, dark resistivity, carrier lifetime, etc. Perform initial design of prototype PC photomixers at 1550 nm with performance comparable to current GaAs-based devices driven by 800-nm pump devices. Specifically, the target power levels should be >10 uW at 1 THz for a single photomixer. Perform analysis to understand factors limiting device power and efficiency. Develop strategies for improving power performance and thermal management. Perform initial design for a 3X3 photomixer array.
PHASE II: Perform full design of high power photomixers including complete thermal analysis to achieve the power level listed in Phase I. Thermal management strategies developed during Phase I should be incorporated. Fabricate and characterize devices to verify performance in terms of frequency content and output power. Design and fabricate a photomixer array in a 3 by 3 format. Each element should be fed by individual fiber input and the input to each element should be derived from the same source through a power splitter to maintain phase coherence. If necessary, in-line fiber amplifiers should be included to boost input drive to achieve high THz output power and efficiency. Characterize the THz array to verify individual element performance as well as phase coherence between array elements. Explore beam steering by adjusting relative phases of the array elements.
PHASE III DUAL USE APPLICATIONS: It is expected that these 1550-nm PC devices will be useful for compact THz systems for a wide range of army-relevant applications such as concealed weapon detection, biological-agent, biomedical imaging, and high-date-rate communications. Phase III work will develop and commercialize compact and low cost THz systems such as broadband radar, spectrometers, imagers, and high-speed communication transmitters based on these devices. Lower overall system cost and reduced size through the use of inexpensive optical fiber technology at the 1550-nm telecommunications band mean these THz systems can be widely deployed and man-portable. The performer can explore transition opportunities either through in-house development of these THz systems or by partnering with system developers as a supplier of these THz sources.
1. E.R. Brown, “Advancements in Photomixing and Photoconductive Switching for THz Spectroscopy and Imaging,” Proc. Of SPIE, Vol. 7938, Terahertz Technology and Applications IV, 793802, March, 2011
2. J. E. Bjarnason, T. L. J. Chan, A. W. M. Lee, E. R. Brown, D. C. Driscoll, M. Hanson, A. C. Gossard, and R. E. Muller, “ErAs:GaAs photomixer with two-decade tunability and 12 µW peak output power,” Appl. Phys. Lett., vol 85, pp. 3983-3985, Nov. 2004
3. J. Middendorf, W. Zhang, M. Martin, and E. Brown, “First demonstration of photomixing at 1550 nm in ErAs:GaAs,” 39th International Conference on Infrared, Millimeter, and Terahertz Wave, September, 2014
4. R. Salas, S. Guchhait, S. D. Sifferman, K. M. McNicholas, V. D. Dasika, D.J. Ironside, E. M. Krivoy, S. J. Maddox, D. Jung, M. L. Lee, and S. R. Bank, “Properties of RE-As:InGaAs Nanocomposites,” 56th Electronics Materials Conference, June, 2014
TITLE: High-Speed Cryogenic Optical Connector for Focal Plane Array Read-out
TECHNOLOGY AREA(S): Electronics
OBJECTIVE: To develop faster and more efficient free-space optical interconnect solutions for connecting focal plane arrays with high-speed read-out integrated circuits in cryogenic dewars to the outside world thru a transparent window.
DESCRIPTION: Advances in vertical cavity surface emitting lasers (or VCSELs) and/or integrated photonic modulators are desirable to solve interconnect problems at higher speeds and free-space regimes. Current VCSELs are limited to about 40 Gbps at operating temperatures from about -40 C to 85 C. An aspect of this technology currently overlooked by the main stream data center and computing applications is operation of such high-speed interconnects at cryogenic temperatures. Although prior work in cryogenic VCSELs has shown speeds up to about 10 Gbps , advances have been made in the thermal performance and speed which can be garnered for next generation focal plane array read-out. Particular advances in speed are needed based on newer high definition (HD) formats and faster frame rate requirements (up to a kHz or more). For very high sensitivity imaging, cryogenic cooling of focal plane arrays (FPAs) at 77K is required. Free-space optical interconnection thru the cryogenic dewar windows can be used to read-out the vast amount of data generated. Use of integrated photonic solutions is required due to limitations with copper twisted pair to 1 Gbps which is the primary method used to read-out focal plane array data. As the number of high speed copper signal data lines increases, so does the thermal path between the cold FPA and the warm dewar exterior. This thermal short drives increased cooling requirements on the closed cycle cryocoolers that are used in these imaging sensors – typically resulting in reduced MTBF and higher power draw. This can be combated by using larger cryocoolers, but that has direct impact on the system size, weight, and power requirements. In addition, using larger cryocoolers only postpones dealing with the problem as FPA pixel count and frame rate continue to increase. It therefore becomes necessary to realize an optically based, free space data link between the cryogenically cooled FPA and the exterior of the vacuum dewar. VCSEL arrays could be used in this small area to interface with multiple output channels. However, Read-Out Integrated Circuits (ROICs), bonded to the FPAs, may have only a limited number of output pins in order to reduce focal plane heating that occur through metallic conduction paths. Multiplexing of ROIC channels through the output channels can lead to very high data rates and require the need for advances in VCSEL and/or modulator technology. This topic aims to garner advances in VCSELs (and possibly modulators) that have excellent thermal performance as well as high-speeds at cryogenic temperatures. Interconnects with the ROICs can be made through chip-scale packaging techniques to either single VCSEL transceivers or combined to one VCSEL array based transceiver for the cryostat optical through port window. Advances in the speed of the requested interconnects will make military imaging possible at much higher frame rates, and with larger format focal plane arrays.
PHASE I: The concept design of a cryogenic active optical connector with capability of providing gain or modulation for board to board level interconnect schemes which is compatible with free-space optical interconnects, and which is tolerant to beam misalignments for beams extending to several cm’s. Potential of 40 Gbps or greater interconnects should be demonstrated for a single channel thru a cryogenic dewar window held at 77K. Low bit error rates (BERs) -approximately 1e-10 or less should be targeted. Goals of design include scalability in the number of data channels and layout flexibility for attachment to high-speed ROICs including process compatibility with mainstream electronics manufacturing.
PHASE II: This phase will further develop the concept to key technology milestones. The thrust of this effort should be placed on subsystems development, and technology demonstration. Alignment tolerances within 0.5 degrees and mm’s need to be demonstrated. Bandwidth of regenerative elements and channels should exceed 40 Gbps for a single channel with low BERs- approaching 1e-12 or less. A concept demonstration prototype shall be demonstrated within a cryogenic (77K) dewar with potential demonstrations at even lower temperatures. Proposed solutions should be compatible with both pour-filled laboratory grade liquid nitrogen dewars, as well as tactical closed-cycle cryogenic dewar configurations. Government furnished high-speed ROICs and/or FPAs will be provided for demonstration assuming availability from the Army. These ROICs will utilize digital-on-chip analog to digital conversion and the data will exit the ROIC as digital information. Offerors should assume a nominal 512 x 540 FPA at 18 micron pitch, with an objective of up to 2048 x 2160 at 18 micron pitch or equivalent. For the phase II demo, FPA data rates up to 3.0 Gbps are to be supported. A path to higher data rates should be demonstrated as well. Military robustness and functionality should be assessed at cryogenic regimes where vibration and ruggedness are possible factors. Deliverable of the completed camera unit is desired.
PHASE III DUAL USE APPLICATIONS: The commercialization pathway would consist of working with government or commercial end users to develop a specific layout and product for cryogenic temperature optical interconnects. Use of developed cryogenic VCSELs and room temperature receivers should be made in conjunction with free-space thru window regimes. Commercial applications: Potential commercial applications include high-speed focal plane read-out, high-end servers and routers, high performance signal processing and supercomputing. Military Applications: Supports Transformational Communication Architecture (TCA), integrated C4ISR optical systems, synthetic aperture ladar, signal image processing, communication routers.
1. D. Serkland, K. Geib, G. Peake, G. Keeler, A. Hsu, “850-nm VCSELs optimized for cryogenic data transmission,” Proc. of SPIE Vol. 8276 (2012)
2. E. Heyes, C. Ozturk, V. Ozguz, and Y. Guruz, “Solution-based PbS photodiodes, integrable on ROIC, for SWIR detection applications,” IEEE Electron. Dev. Lett. 34, 662 (2013)
3. S. Gunapala, S. Bandara, J. Liu, J. Mumolo, D. Ting, C. Hill, J. Nguyen, B. Simolon, J. Woolaway, S. Wang, W. Li, P. LeVan, and M. Tidrow, “Demonstration of megapixel dual-band QWIP focal plane array,” IEEE J. Quant. Electron. 46, 285 (2010)
4. S. Gunapala, D. Ting, C. Hill, J. Nguyen, A. Soibel, S. Rafol, S. Keo, J. Mumolo, M. Lee, J. Liu, B. Yang, and A. Liao, “Large area III-V infrared focal planes,” Infrared Phys. Tech. 54, 155 (2011)
5. E. Haglund, P. Westbergh, J. Gustavsson, E. Haglund, A. Larsson, M. Geen, and A. Joel, “30 GHz bandwidth 850 nm VCSEL with sub-100 fJ/bit energy dissipation at 25 – 50 Gbit/s,” Electron. Lett. 51,, 1096 (2015)
6. D. Kuchta, A. Rylyakov, C. Schow, J. Proesel, C.W. Baks, P. Westbergh, J. Gustavsson, and A. Larsson, “A 50 Gb/s NRZ modulated 850 nm VCSEL transmitter operating error free to 90°,” J. Lightwave Tech. 33, 802 (2015)
7. D. Kuchta, A. Rylyakov, C. Schow, J. Proesel, C.W. Baks, P. Westbergh, J. Gustavsson, and A. Larsson, “A 71-Gb/s NRZ modulated 850 nm VCSEL-based optical link,” IEEE Phot. Tech. Lett. 27, (2015)
OBJECTIVE: Develop and demonstrate advanced techniques for lead acid battery monitoring, diagnosis, and prognosis in order to reduce lead acid battery failures and predict battery failure.
DESCRIPTION: Absorbed Glass Mat (AGM) and flooded lead acid batteries are widely used on 95% of military ground vehicles for Starting, Lighting, and Ignition (SLI) and silent watch applications. Not only does the battery represent one of the top ten ongoing maintenance costs for military vehicles at ~$100M for maintenance costs per year, they tend to fail unexpectedly. Often the first sign of a battery issue is that the vehicle designated for a mission simply will not start. Vehicle battery degradation and failure can occur earlier than expected due both to intrinsic issues and improper maintenance. Common failure modes include: loss of electrolyte, acid stratification, improper charging profiles (failure to fully charge battery) leading to sulfation, electrode corrosion, and separator failure. Current battery testers generally measure cold cranking amps (CCA) and voltage but do not provide information about battery capacity which is arguably the most important measurement of battery performance. Recent results using electrochemical impedance spectroscopy (EIS) have shown promise providing insight into chemical state of the battery which is important to detect sulfation, electrode corrosion, and separator failure, however, system complexity and difficulty interpreting results have hampered implementation. The Army needs both hand-held and on-vehicle prognostic/diagnostic tools to capable of determine battery state of charge, capacity, level of acid stratification; sulfation, surface charge, and predict imminent failure and provide possible corrective actions regardless of cause. The goals of this topic are to develop an improved understanding of methods to understand the chemical state within a lead acid battery to detect battery degradation and failure modes and develop advanced techniques for monitoring, diagnosis, and prognosis specifically for lead acid batteries to enable reduced battery maintenance and increased battery service life. Packaging and performance requirements of vehicle battery monitoring system can be found in reference 3.
PHASE I: Conduct research with laboratory analysis and testing to demonstrate the feasibility of the proposed approach. Phase I must include a laboratory proof of concept demonstration of the proposed techniques that shows the capability to monitor state of charge and capacity within 15%, diagnose battery degradation (including acid stratification and degree of sulfation), and prognosis and identification of pending failures (greater than 85% accuracy) for both absorbed glass mat and flooded lead acid batteries.
PHASE II: Further demonstration, modification, and optimization of the proof of concept from phase I. This phase includes the, fabrication, testing and delivery of the prototype hardware and software system that can be tested both in the lab and on vehicle and must include demonstration of improved vehicle battery monitoring (uncertainty less that 10%), diagnosis, and prognosis techniques and demonstration of the techniques’ ability to improve battery life by over 15% over the baseline for current 6T military lead acid batteries (largely expected by identification of maintenance issues). This phase should also include the design of the battery testing profile and demonstration of the battery monitoring, diagnostics, and prognostics techniques for improved battery status indication to reduce battery failures and increase battery service life while retaining the battery capacity.
PHASE III DUAL USE APPLICATIONS: Technology developed in this topic could be used for military and/or commercial applications. The results from developing this battery monitoring, diagnosis, and prognosis technique should enable system incorporation into existing military vehicle systems, as well as into commercial automobiles. On-board systems could be integrated into new lead-acid vehicle batteries or automobiles to alert users of need for battery maintenance or pending failure. Alternatively the technology could be integrated into a hand held unit used during routine maintenance of the vehicle. The goal in this phase will be applied to military and commercial ground vehicle platforms.