How to collaborate with unmotivated postdocs
How can I properly motivate my postdoc to get him work for me?


You don't. Changing anyone's behavior is difficult; changing your "superior's" behavior will be even less successful and will lead to conflict. 

I would start by trying to figure out how long the post-doc is planning to be around. It may be that he is on his way out; this would explain both his lack of focus and the professor's apathy.

In any case, I agree with the discussion in the comments -- the situation as you describe it is inexcusable. But as a PhD student, your options are very limited. I would suggest asking the professor for a private meeting. In the meeting, I suggest making the following points.


You successfully published a paper in a top journal
The post-doc contributed virtually nothing to this work, and in fact delayed progress
You feel it "may have been inappropriate" to even list the post-doc as an author of the paper
Based on this experience, you think it would be more fruitful to work independently from the post-doc on future efforts.


The professor will likely not be receptive to this, and will make some vague promise about speaking to the post-doc. So, the real question you should be asking (yourself) is:


  Should I finish my PhD with this advisor or find another group?


If you are willing to leave (and you are sure!), you can mention this to your advisor if his initial reaction is not satisfactory. This may change the calculation for him -- or he may be more candid with you (e.g., telling you that he is about to fire the post-doc). Or he may let you go. 

If you are close to graduation, then it's probably worth sticking this out. Adding people as authors when they didn't contribute much does not really rise to the level of serious academic misconduct, so I would simply avoid relying on the post-doc as much as possible.