If this is your requirement, you don’t have to step up the DC.
10 watt is the Power rating. Remember the equation, Power = Voltage * Current.
The Voltage of the LED must be less than 2V, but it require very high current to glow brightly. So all you have to do is to use a very good quality battery and connect the LED with a resistor in series.
The value of the resistor can be calculated using the equation,
Resistance = Voltage / Current.
If this resistance is greater than the internal resistance of the battery that you are using (you can get from the datasheet) then you can directly connect the LED.