There can be one more reason,the electronegativity diffrence in Li and F is more as compared to Li and Br,so LiF is more ionic,hence more stable,hence more Lattice energy
Anyone who has never made a mistake has never tried anything new
You can never solve a problem on the level on which it was created.
When you are courting a nice girl an hour seems like a second. When you sit on a red-hot cinder a second seems like an hour. That's relativity
Purpose of solving a problem is not simply to get the answer(the answer is only an evidence) but to develop your thinking ability