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Innovative, High-Energy, High Power, Light-Weight Battery Storage Systems Based on Li-air, Li-sulfur (Li-S) Chemistries


As the Navy modernizes its Fleet, the energy needs of naval aircraft are increasing significantly. Meeting the energy demands of these aircraft is a formidable challenge which requires looking beyond current Lithium-ion (Li-ion) batteries. The state-of-the-art Li-ion cells have a theoretical specific energy of 387 Wh/kg (watt hour/kilogram) and energy density of about 1015 Wh/L (volumetric energy density), respectively. The specific energy of the Li-ion cells are attractive because, in comparison to nickel-cadmium and lead-acid batteries, Li-ion batteries offer significant advantages – decreased weight (~1/3) and increased capacity (~3X). The decrease in weight would result in cost savings due to lower fuel consumption during flight or the ability to increase payload, which increases mission capability. Li-air and Li-S are two emerging chemistries that can meet such energy demands. There are two types of rechargeable Li-air batteries undergoing research, namely, non-aqueous and aqueous systems. The theoretical specific energy for the non-aqueous system (organic electrolyte based) is 3505 Wh/kg and the theoretical energy density is about 3436 Wh/L, which are about ten times greater than the Li-ion cells. The corresponding parameters for the aqueous systems are 3582 Wh/kg and 2234 Wh/L, respectively, which are also approximately ten times greater than the Li-ion cells [1]. The Li-sulfur cells have a theoretical specific energy of 2567 Wh/kg with a theoretical energy density of 2200 Wh/L. Each component of the non-aqueous Li-air battery faces unique technical challenges. For example, dendrite formation on the Li metal anode raises safety concerns that impact the capacity retention of the cell and contribute to voltage gap during cycling process. One of the challenges for the aqueous type Li-air is the requirement of a Li-ion conducting membrane to protect the Li metal. The polysulphide solubility is a concern for the Li-S batteries [1-3]. These challenges lead to low specific energy and poor cycling efficiency for the current Li-air and Li-sulfur systems. Combinations of material innovations and advancement in obtaining stable interfaces are key to solving such challenges. Disruptive new Li-air and Li-S concepts have the potential to increase cycle life, round trip efficiency, and power density from their current levels which are critical to the development of reliable next-generation battery chemistry technologies. The purpose of the topic is to develop 28V (Volt) DC (Direct Current) / 270 VDC electrical energy storage devices based on emerging chemistries such as Li-air and Li-S. The offerors must demonstrate the minimum specific energy for Li-air cells in the range of 600-1000 Wh/kg or higher (at least 3X higher than Li-ion cells) or in the range 400 – 800 Wh/kg for Li-S cells. The offerors must propose innovative approaches to overcome the challenges mentioned above to achieve the defined threshold values with the goal of approaching theoretical energy density as objective values. The battery system to be developed (28V / 270V DC) must be stable under aircraft operational, environmental, electrical, and safety requirements governed by applicable government documents [4-5]. The requirements include, but are not limited to, sustained operation over a wide temperature range from -40 deg (degrees) C (Celsius) to +71 deg C, including exposure to +85 deg C and the ability to withstand carrier based shock and vibration loads, altitude range up to 65,000 ft (feet), per MIL-STD-810G [6], and electromagnetic interference of up to 200 V/m (Volts Per Meter), per MIL-STD-461F [7]. Proposed innovative pathways must meet additional requirements of low self-discharge (< 5% per month), good cycle life (> 2000 cycles at 100% Depth of discharge (DOD)), and long calendar life (4-7 years' service life) at cell level (threshold) and at battery product level (objective). The diagnostic/prognostic capabilities of the system that will lead to developing a safer, reduced total ownership cost functional product should also be addressed. PHASE I: Design and develop an innovative concept to address low specific energy and low cycle life and demonstrate the feasibility of Li-air and or Li-S battery at full-cell level. Perform critical safety and electrical performance evaluations of Li-air and/or Li-sulfur batteries. PHASE II: Develop a prototype and demonstrate the functionality of a Li-air and/or Li-S battery over a wide-temperature range, under select harsh environmental, storage, and cycling conditions. In addition, initiate the scale-up and design processes and develop preliminary cost structure. PHASE III: The functional aircraft-worthy prototype battery product should be developed with performance specifications satisfying targeted acquisition requirements coordinated with Navy technical point of contacts. Complete testing per military performance specifications and transition to appropriate platforms (Ex. F/A-18E/F, F-35 etc.). Commercialize the Li-air, Li-S battery technology and leverage the advantages of scalable manufacturing process to develop a cost-effective manufacturing process for technology transition to various system integrations for both DOD and civilian applications.
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