In the last Pokemon (2019) anime episode, a world champion
even needs to bring back his pokemon Charizard back to Pokeball to do Daimax (a.k.a. Dynamax) transformation. However, Ash's Pikachu is able to do it without going back into Pokeball.
He also told Ash that he needs to return his pokemon into Pokeball to turn his Pikachu into Daimax.
He also gave Ash
a Daimax band to control Daimax pokemon,
but he was shocked by seeing Ash able to control Daimax pokemon without it.
How did Ash do that?