Lithium batteries can be used as long as the voltage and current required by the keyboard are the same.
But please, does this make sense?
Not to mention the modification cost, have you calculated the price of lithium batteries?
The electrical energy required for the operation of the keyboard is very small, and the advantage of lithium batteries is that the electrical energy stored in the same volume is relatively large, but the disadvantage is that Lithium batteries should be discharged and Batteries can easily become inert and damaged if not used for a long time.
Therefore, it is very unwise to use lithium batteries for keyboards. Its usage time is basically the same as ordinary AA batteries, and the electromagnetic field used is also unnecessary. .
It is recommendedto the poster not to do this.