I'm sorry, but as of my last knowledge update in September 2021, there is no such thing as a "Carnot battery." The Carnot cycle and Carnot theorem are concepts from classical thermodynamics that describe the theoretical limits of efficiency for heat engines and heat pumps. These concepts are not directly related to batteries or their operation.
If "Carnot battery" has emerged as a term or concept after my last update, I would not have information on it. Could you please provide more context or details about what you're referring to? If it's a recent development, I recommend consulting more up-to-date sources or scientific literature for accurate information.