The Department of Defense, specifically the U.S. Navy and Marine Corps, is seeking innovative solutions for the development of a safe and robust sodium-ion (Na-ion) battery for use in naval aviation. The objective is to design a Na-ion battery that meets the stringent environmental, operational, and storage requirements of naval aviation systems while providing enhanced safety and leveraging domestic materials supply chains. This initiative is crucial as it aims to replace existing lead-acid and lithium-ion batteries, which pose safety and supply chain risks, with a more efficient and safer alternative. The solicitation is set to open on April 23, 2025, with applications due by May 21, 2025, and further details can be found at the provided source link.

## Description

U.S. Navy and Marine Corps currently fields lead-acid (Pb-acid), nickel-cadmium (NiCd), and limited lithium-ion (Li-ion) batteries for use across aviation platforms. Pb-acid and NiCd batteries have significantly lower energy density and service life than currently fielded Li-ion batteries used in the commercial electric vehicle market, resulting in negative impacts to aircraft performance and readiness. While Li-ion batteries are significantly more energy dense than legacy chemistries, the potential for thermal runaway events, high cost, and supply chains reliant on foreign entities of concern (FEOC) create safety, cost, and availability risks to programs. Na-ion batteries offer improvements to energy density comparable to Li-ion solutions while utilizing materials abundant domestically and abroad and may offer significant improvements to safety due to their wide thermal operating envelope. Na-ion batteries are currently in development and fielded commercially by FEOCs abroad. The objective is to design and develop a sodium-ion (Na-ion), secondary, battery solution for use across manned and unmanned aircraft that meets the environmental, operating, and storage conditions of Naval Aviation battery systems, provides increased safety over current lithium-ion battery solutions, and leverages domestic materials supply chains. Therefore, the intent of this SBIR topic is to develop a Na-ion battery that can meet the harsh environmental operating and storage conditions of Naval Aviation battery systems while providing weight and energy savings to the platform with safety improvements and leveraging the materials required in the domestic supply chain.

## Objective

Design and develop a sodium-ion (Na-ion), secondary, battery solution for use across manned and unmanned aircraft that meets the environmental, operating, and storage conditions of Naval Aviation battery systems; provides increased safety over current lithium-ion battery solutions; and leverages domestic materials supply chains.

## Phase I

Define and develop a concept for feasible battery designs including requirements compliance matrices and defined trades. Determine the feasibility of a Na-ion battery design that leverages requirements from multiple, Navy-led, battery commonality efforts that are traceable to systems engineering models of the MIL-PRF-29595 General Specification for Aircraft Rechargeable Lithium Batteries [Ref 3], its associated slash sheets, and small unmanned aerial systems (sUAS) battery designs. Develop a preliminary design review (PDR) level design and recommended validations leveraging the S9310-AQ-SAF-010 Navy Lithium Battery Safety Program [Ref 4] and MIL-PRF-29595 performance specification modified for a Na-ion battery systems.The Phase I effort will include prototype plans to be developed under Phase II.

## Phase II

Develop five (5) prototype Na-ion batteries to validate improvements to performance, including weight savings, across operational and storage environmental envelopes. Demonstrate use of the domestic materials supply chain by providing relevant bill of materials (BOMs) for prototypes, as well as outlook on future domestic materials supply chain required for Na-ion battery components. Provide report of validation findings and supply chain analysis to Navy customers and program offices that demonstrates benefits of Na-ion over commercial Li-ion solutions.

## Phase III: Dual Use Applications

Develop thirty-one (31) batteries for qualification testing to the S9310-AQ-SAF-010, MIL-PRF-29595 and designated slash sheet, MIL-STD-461, MIL-STD-704, MIL-STD-901, and MIL-STD-167 specifications and instructions for successful aircraft and ship integration. Develop four (4) additional batteries for use during flight test and demonstration for transition to the application platform identified in Phase I.To date, no Na-ion main ship aircraft battery has been developed for commercial aviation. The Na-ion battery benefits of weight savings while providing robust performance and safety across a wider envelope than Li-ion solutions may be transferrable to commercial aviation. Additionally, if Na-ion solutions cannot meet space, weight and power (SWaP) requirements for use in aircraft, the technology can be transitioned to efforts supporting electrification of Ground Support Equipment (eGSE), Uninterruptable Power Supplies (UPS), and grid energy storage domains.

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