This appears to be hardcoded functionality in the Excel Exporter module.
If you felt comfortable changing Java code, you could fork the module, change the default quote character from the constant to an empty character, and see if that gives you the functionality you require.
Alternatively, you could put a request in the ideas forum to make this functionality configurable.
@Ravan (your profile isn't public so I am unfortunately unable to message you).
I just noticed this tread because I had the same problem.
Change the reference of CSVWriter.DEFAULT_QUOTE_CHARACTER to CSVWriter.NO_QUOTE_CHARACTER to completely remove all quotes.