Nominating the person you prefer to receive your superannuation can be done in a binding and non-binding way. A binding nomination must be followed by the super fund provided the nomination remains current and valid at the time of death.
Some binding nominations can be disputed. For example some funds require the nomination to be made to a dependant, and the definition of dependant will potentially change from fund to fund. An ex wife who met the definition at the time of the nomination when married to the member may not meet the definition after a divorce or separation.