Do you know what's up with molten salt batteries? I've heard GE was big on it but then after investing a ton of money they just closed it down. Is the technolo

Do you know what's up with molten salt batteries? I've heard GE was big on it but then after investing a ton of money they just closed it down. Is the technology not viable? Seemed to me like a green solution that is working ok and can be used now.