Ann: Presentation - Diggers & Dealers Mining Forum - August 2022, page-17

MnSo4 is 32% Mn and then Sulphate being the vast majority,, then there are the impurities which are in Parts Per Million PPM.
When coming from Manganese metal to MnSo4 there is a Selenium impurity, which is why E25 are now looking to use traditional Leaching methods to produce MnSo4.
E25 are still trying to purify their product to get ultra high purity MnSo4, yes they may say battery grade, but that is the absolute bottom end of the purity spectrum.
EMN (Euro Manganese) has a process to not use Selenium to produce MnSo4 from their Mn Flake metal, but it is very high cost, and I have never seen them report good purity for basttery grade MnSo4 either.
Mn Energy is a WA unlisted company who has produced ultra high purity MnSo4, they have had it trialled by the Future Battery Industry CRC here in WA and it worked perfectly in the Precursor cathode that was produced.
I am not a chemist so DYOR.