[Defense Column] Batteries Used in Missiles

[Agency for Defense Development]Countries surrounding the Korean Peninsula, including North Korea, as well as advanced nations, have long spared no effort or investment to enhance the performance of guided weapons, primarily represented by missiles. Representative guided weapons include Intercontinental Ballistic Missiles (ISBM) and hypersonic cruise missiles (HCM). Thermal battery technology is a core technology field that supplies the essential power source for operating guided weapons with high performance and destructive power. The Agency for Defense Development (ADD) has independently developed domestically for the first time in the world a lithium anode technology using metal alloy foam, creating an opportunity to improve the performance of guided weapons.

▲ What is a thermal battery?= The batteries installed in guided weapons use special thermal batteries that are not used in civilian fields. Guided weapons such as missiles are not used during peacetime but must deliver 100% of their target performance within 1 to 2 seconds when a wartime situation occurs. Guided weapons are usually stored for more than 10 years and sometimes up to 30 years. Rechargeable batteries or dry cells used in civilian applications have a self-discharge characteristic, where their performance rapidly decreases if stored unused for several months. Therefore, civilian rechargeable batteries or dry cells cannot be used in guided weapons.

The battery developed to suit the characteristics of guided weapons is the thermal battery. Thermal batteries do not exhibit performance as batteries during storage (the electrolyte exists as an ion insulator, preventing ion passage). When an electrical signal (ignition signal) is applied to the circuit according to the guided weapon launch procedure, internal components ignite, instantly generating heat exceeding 500 degrees Celsius, causing the electrolyte to become ion-conductive and the battery to start operating. Because the battery operates by heat, it is called a thermal battery, and its formal name is thermally activated reserve battery.

. Schematic diagram of a thermoelectric cell using metal foam

▲ Lithium anode that withstands 500 degrees Celsius= Countries spare no effort or investment to develop thermal batteries used for special purposes. Thermal battery technology applies electrical, materials, and mechanical engineering technologies, among which anode technology is recognized as the most critical. The anode is the component that generates the energy of the thermal battery. Thermal batteries have their roots in lithium batteries.

This is because electricity is generated from lithium contained in the anode. However, unlike lithium battery methods used in smartphones and electric vehicles, it is quite challenging technology to stably store a large amount of lithium, which melts at 180 degrees Celsius, in an operating environment of 500 degrees Celsius. As shown in the figure below, the first-generation thermal battery anode technology uses lithium alloy (lithium-silicon alloy (Li-Si alloy)) that exists as a solid at 500 degrees Celsius.

This method has been the most widely used worldwide so far. In the 2000s, ASB, the world's leading thermal battery company in France, developed and began exporting a so-called LAN (lithium anode) by mixing iron powder with pure lithium for use as a thermal battery anode. This technology is known as the world's best technology to date.

Until now, most domestic thermal batteries have applied first-generation technology, and thermal batteries for high-performance guided weapons were entirely imported from France's ASB. In this situation, ADD developed an independent thermal battery anode technology that surpasses LAN technology, known as 'LIMFA (lithium impregnated metal foam anode),' which uses metal alloy foam material impregnated with lithium.

▲ The highest performance thermal battery anode technology currently available= In terms of performance comparison, the specific energy (A.s/g) of first-generation lithium alloy anodes is about 900 to 1100 A.s/g. The highest known performance of the second-generation LAN is about 1,300 to 1,500 A.s/g. The thermal battery anode using metal alloy foam developed by ADD shows a performance of approximately 3,009 A.s/g. This performance is the highest among known thermal battery anodes and was published in the world-renowned battery technology journal Journal of Power Sources, with related technologies patented in the United States and Japan.

▲ Plans to secure world-class thermal battery technology= The thermal battery anode technology using metal alloy foam is still under research and development for practical application and mass production. Many technical stages must be passed for the new technology to be perfectly and stably applied. Also, to verify reliability, one of the most important factors in guided weapons, numerous evaluations and researchers' efforts and determination to address issues arising during evaluations are necessary.

Developing payloads for guided weapons requires not only anodes but also world-class cathode development and research and development in various technical fields such as electrical and mechanical engineering. Furthermore, after completing thermal battery development, final performance verification must be conducted by installing the thermal battery in guided weapons that require its power, which requires significant time and effort. ADD is making its best efforts to secure world-class thermal battery technology and will continue to pursue challenges in the future.

This content was produced with the assistance of AI translation services.