용융염 전지, a molten salt battery

용융염을 전해질로 사용하는 전지이다. 열전지나 액체금속전지라고도 불리운다. 본래 2차 세계대전 중 독일 과학자 게오르크 오토 에르프에 의해 발명됐는데, 당시에는 재충전이 불가능한 열전지로, 전지에 500도 이상의 열을 가해 전해질 역할을 하는 염과 애노드 역할을 하는 금속, 캐소드 역할을 하는 금속이 액화되면서 에너지를 방출하는 방식이었다. 이런 방식의 열전지는 주로 알루미늄 제련 공장에서 사용되는데, 이는 열전지가 막대한 에너지 밀도를 지닌데다 고압의 전력을 출력해낼 수 있어 알루미늄 전기분해 제련법에 사용되기에 적합했기 때문이다. 이외에 유도미사일 탑재용 전지로 사용되기도 한다.

재충전이 가능한 용융염 전지는 1960년대부터 연구되고 있었다. 배터리용 염의 용융점은 98도로 사실 그리 높은 온도가 아니기에, 애노드와 캐소드 역할을 하는 금속만 잘 찾는다면 상대적으로 낮은 온도에서도 작동이 가능한 전지를 개발할 수 있다. 즉 충전 및 방전 과정에서 발생하는 열만으로도 염의 액체상태를 유지할 수 있게 하면 되는 것이다. 특히 풍력과 태양광 발전같은 재생에너지의 확대로 고용량의 전력을 저장할 수 있는 배터리 기술의 필요성이 대두되는 상황에서 용융염 전지는 이에 대한 해법이 될 수 있다. 실제로 MIT에서 상용화가 가능한 용융염 전지의 개발에 성공했다. 현재 기술로 컨테이너 박스 크기만한 공간에 약 200가구가 사용가능한 2MWh 정도의 전력을 저장할 수 있다.

액체금속이라는 이름에서도 알 수 있다시피 애초에 휴대성이 아닌 경제성과 에너지 밀도에 초점을 맞춘 전지이다.

 

 

 

It is a battery that uses molten salt as an electrolyte. It is also called a thermoelectric cell or liquid metal cell. Originally invented during World War II by German scientist Georg Otto Erf, it was a non-rechargeable heat cell at the time. At that time, a salt that serves as an electrolyte, a metal that acts as an anode, and a metal that acts as a cathode are liquefied to release energy. This type of thermal cell is mainly used in aluminum smelting plants because the thermal cell has a huge energy density and can output high-pressure power, making it suitable for use in aluminum electrolysis smelting methods. It is also used as a battery for guided missiles.

A molten salt battery that can be recharged has been studied since the 1960s. The melting point of the battery salt is 98 degrees, which is not a very high temperature, so a battery that can operate even at a relatively low temperature can be developed if only the metal serving as an anode and a cathode is well found. In other words, it is sufficient to maintain the liquid state of the salt only with the heat generated during the charging and discharging process. In a situation where the need for battery technology capable of storing high-capacity power emerges especially due to the expansion of renewable energy such as wind and solar power generation, molten salt batteries can be a solution to this. In fact, MIT succeeded in developing a molten salt battery that can be commercialized. With the current technology, about 200 households can store about 2 MWh of power in a space the size of a container box.

As the name liquid metal indicates, it is a battery that focuses on economic feasibility and energy density, not portability.