Generate a new table with each click in Firebase and Ionic3

How can I generate a new table in Firebase every time I click on the save button of my application?

I have this function in my .ts ...

guardar(){
    let i: number = 1;
    let j = i++;
    (this.fdb.list("/Usuario :"+j).push(this.nombre),
    this.fdb.list("/Usuario :"+j).push(this.apellido);}

... but I save the data in the same table.