Defence: The Ja-gee Attack: Book 2 of the Laner Series — Paul Arthurs

Starship captain Arthur Laner and the crew of Peregrine are preparing for a hero's welcome. They have destroyed a Ja-gee task force, put a Ja-gee warship to flight, and rescued the crew of the exploration ship Raleigh. After towing a captured alien battleship hundreds of light years to Brasilia station, they ready to hand over their bounty to Defence.
But that would have been too tidy.
Subterfuge endangers the ship. Betrayal tears the crew apart. A high-level cover-up threatens the truth.
Then, as the Ja-gee and Human space fleets prepare for battle, Peregrine is sent away to a distant star on a secret mission that could decide the fate of Humanity.
Ship and crew are designated as expendable.
Even if Laner and his crew survive, there may not be an Interstellar Concordance to return to.