TECHNOLOGY AREA(S): Air Platform, Materials/Processes, Space Platforms

ACQUISITION PROGRAM: PMA 275 V-22 Osprey

OBJECTIVE: Leverage additive manufacturing (AM) for innovative battery design, fabrication, packaging, and integration.

DESCRIPTION: Naval aviation uses electrochemical storage devices, such as batteries, for aircraft emergency power, avionics, weapons, and other equipment.� These devices broadly belong to primary and secondary rechargeable batteries with different types of material chemistries such as lithium/MnO2, lead-acid, nickel-cadmium, and lithium-ion.� Battery chemistries have evolved over the decades where the desired key performance parameters (KPPs) are energy density >700Wh/L, specific energy >200Wh/Kg, power density >1500W/Kg, light weight, high cycle >2000 cycles and calendar life > 6 years, environmental friendliness, and affordable cost without compromising on safety, which is paramount for Navy applications.

Battery development efforts are focused on improving the energy and power density without compromising safety.� To date, Li-ion batteries with ~3X power and energy density and ~1/3 weight are replacing the matured lead-acid and nickel-cadmium batteries chemistry technologies.� Efforts are underway to develop next-generation batteries, with Li-S and Li-O2 having up to 10X theoretical energy density compared to Li-ion battery chemistries.� These battery cells, modules, and packs are packaged in rigid, metal containers and pouches in various geometries.� The degrees of freedom associated with such rigid form factors are limited, and pose major challenges for battery encapsulation, packaging, and integration.� As such, a need exists for compact, flexible batteries that could also be conformal to the structure.� Eliminating bulky containers that house cells removes the deadweight of the batteries and improves their energy density.� Such batteries will have a huge impact not only on naval aviation batteries, but also on flexible and wearable sensor technologies powered by batteries.

Electrode materials with novel architectures (i.e., composite, three-dimensional (3D)) have the potential to improve both ionic and electronic conductivity (a.k.a., transport phenomena of electrochemical devices), resulting in increased energy density per volume and weight with high Columbic efficiency while maintaining high cycle life, a stable solid-electrolyte interphase (SEI), and improved safety.� Such high energy-density, electrode materials reduce the amount of material needed to make cells as well as the number of cells needed for building the pack and battery module.� As a result, the amount of supporting hardware material needed to assemble the battery is reduced, resulting in positive cost benefits ($400/KWh).

There is an immediate need for disruptive battery manufacturing technologies that meet the energy, power, packaging, interconnect, and integration requirements for current and next-generation batteries.� Innovative two-dimensional (2D) and 3D architectural designs for the fabrication and integration of batteries compatible with the large-scale manufacturability are key enablers.� Technological advancements that provide paradigm shifts in electrochemical device design, manufacturing to accommodate novel geometries, materials, non-traditional processing, and fabrication methods to improve reliability and costs are needed.

AM, commonly known as "3D printing," is a set of legacy and emerging technologies that fabricate parts using a layer-by-layer technique where material is placed precisely as directed from a 3D digital file [Ref 1].� AM is a suite of manufacturing processes made up of techniques such as extrusion and dispenser printing, inkjet printing, screen printing, material extrusion, directed energy deposition, and powder bed fusion.� The material in each layer may be polymer, ceramic, metal, or composite depending on the application.� AM techniques offer revolutionary approaches to design, fabrication of battery cells with high power and energy density with improved safety, and customized production manufacturing.

AM enables new design innovations, higher performing build parts, short lead time, fast prototyping, supply chain and inventory benefits, construction of complex parts, smaller runs, and consolidation of complex assemblies into single parts.� New topologies that were not previously possible are now possible with AM, which frees constraints imposed by conventional manufacturing processes where different components are pieced together given the limitations of stamping out current collector metals/electrodes when they are no longer needed to allow better material properties, optimum designs, novel packaging, and integration concepts to emerge [Ref 2]. The degrees of freedom associated with the AM process eliminate packaging and integration challenges and allow flexible and integral configuration layouts along with novel material properties, thereby positioning the technique for a functional device fabrication with flexible form factors. Successful development has the potential to allow batteries to be printed in the field.

Although AM is promising, its full potential can be realized if the following challenges are overcome, including ensuring that the AM processes are robust to maintain battery performance, not only during the fabrication process but also during long-term usage for reliability [Refs 2-5]. The software challenges associated with creating 3D digital files still remain, and the software tools to design, model, and develop electronic files have not matched hardware development.� Even though computer-aided design tools have made tremendous progress, their applicability to AM for complex designs is still evolving.� AM is an innovative technique that allows the fabrication of customized, freeform products and opens new design spaces for battery applications.� It is currently applicable only to niche markets with low-volume production of customized parts.� As such, low costs and high-production speeds are necessary for mass production.

The developed system must be compatible and functional with the existing aircraft operational, environmental, and electrical requirements [Refs 5�8].� The requirements include, but are not limited to, an altitude of up to 65,000 feet, electromagnetic interference of up to 200V/m, operation over a wide air temperature range from -40�C to +71�C with exposure of up to +85�C [Ref 5], and withstand carrier-based vibration and shock loads [Ref 6].� The AM- based battery system must meet additional requirements such as low self-discharge (< 5% per month) and high Coulombic efficiency (> 95%).� The AM-based battery system must have diagnostic and prognostic capabilities to ensure safe operation and service life of the battery.

Firms must build prototype battery cells with demonstrated functionality in Navy relevant operating conditions and a fully functional integrated battery system. [Refs 5-8].

PHASE I: Develop novel design approaches for both hardware and software, and demonstrate feasibility to fabricate batteries using AM processes as a proof of concept.� Phase I will include plans to develop a prototype during Phase II.

PHASE II: Build prototype battery cells and demonstrate AM benefits in improving battery KPPs specified in the description section as compared to baseline cells.� Demonstrate the functionality of battery cells under Navy-relevant operating conditions.

PHASE III DUAL USE APPLICATIONS: Complete a fully functional battery product and demonstrate unique AM integration, processing, and packaging concepts to improve reliability and produce lower $/KWh costs.� Commercial aerospace, automobile, and consumer electronics markets will hugely benefit with batteries developed by AM techniques.� In these industries, the technology should be considered a game-changer.

REFERENCES:

1. Frazier, W. E. �Metal Additive Manufacturing: A Review�, Journal of Materials Engineering and Performance, June 2014, Volume 23, Issue 6, pp. 1917-1928. https://link.springer.com/article/10.1007/s11665-014-0958-z

2. Cobb, C. & Ho, C. �Additive Manufacturing: Rethinking Battery Design. The Electrochemical Society Interface, Spring 2016, pp 75-78. https://www.researchgate.net/publication/303532082_Additive_Manufacturing_Rethinking_Battery_Design

3. Sun, Ke, Wei, Teng-Sing, Ahn, Bok Yeop, Seo, Jung Yoon, Dillon, Shen J., and Lewis, Jennifer A. Lewis. �3D Printing of Interdigitated Li-ion Microbattery Architectures.� Adv. Materials, 2013, 24, 4539-4543 and reference therein.� https://www.researchgate.net/publication/239942285_3D_Printing_of_Interdigitated_Li-Ion_Microbattery_Architectures

4. Kyeremateng, N. A. �Self-organized TiO2 Nanotubes for 2D or 3D Li-Ion Microbatteries�, ChemElectroChem, 2014, 1, pp. 1442-1466. http://onlinelibrary.wiley.com/doi/10.1002/celc.201402109/abstract

5. MIL-PRF-29595A- Performance Specification: Batteries and Cells, Lithium, Aircraft, General specification for (21 Apr 2011) [Superseding MIL-B-29595]. http://everyspec.com/MIL-PRF/MIL-PRF-010000-29999/MIL-PRF-29595A_32803/

6. MIL-STD-810G � Department of Defense Test Method Standard: Environmental Engineering Considerations Laboratory Tests (31 Oct 2008). http://everyspec.com/MIL-STD/MIL-STD-0800-0899/MIL-STD-810G_12306/

7. MIL-PRF-461F � Department of Defense Interface Standard: Requirements for the Control of Electromagnetic Interference Characteristics of Subsystems and Equipment (10 Dec 2007). http://everyspec.com/MIL-STD/MIL-STD-0300-0499/MIL-STD-461F_19035/

8. NAVSEA S9310-AQ-SAF-010, (15 July 2010). Technical Manual for Batteries, Navy Lithium Safety Program Responsibilities and Procedures. http://everyspec.com/USN/NAVSEA/NAVSEA_S9310-AQ-SAF-010_4137/

KEYWORDS: Additive Manufacturing; Electrochemical Device; Battery; Novel Designs; Fabrication; Reliability