The whole thing is pretty hazy in the episode. If there's any blame, maybe throw it at the editor.
Order of events: Episode 2
-The battle happens. The Shinzou is nearly destroyed by a Klingon ship, who turns around and leaves them alone, then they(the Shinzou) is nearly destroyed by an asteroid field.
-The admiral rescues the Shinzou with a tractor beam. He hails Captain Georgiou and tells her that there were heavy losses on both sides. He will now contact the Klingons.
-He hails the Klingins, and recommends a cease fire, "Because when we're not talking..." T'Kuvma is listening to the admiral, turns on his comm, and shows us his respectable English skills.
*Apparently he recloaked the sarcophagus ship during the battle(?).
-T'Kuvma agrees to the cease fire, and prepares his envoy(or claims he will)
*this is where the haziness is most opaque.
-The Sarcophagus ship decloaks and is "running over" the admiral's falgship(like a tank running over a toyota).
-The Admiral self-destructs his ship, which may or may not have disabled the sarcophagus ship.
-At this point, the battle seemingly ends. Every surviving Klingon ship in the Klingon fleet just leaves at warp 10.
-The Shinzou is half adrift. The sarcophagus ship is just chillin'. Things are quiet. T'Kuvma announces to his men "Time to collect our dead."
-Back on the Shinzou, Georgiou says "T'Kuvma lured Starfleet to a massacre. It's time I repaid him." She plans to destroy his mammoth vessel by sacrificing herself in a shuttlepod.
-Burnham pops in. "You can't do that, Captain! You'll make a martyr of him." Georgiou replies "I trusted you, but it appears I never really knew you."
-Then Burnham says "let me go in your place," then she says "I have a plan."
-they now beam the photon torpedo(?) Onto the corpse being dragged off the battlefield. And we know the rest.