After Ichigo lost his powers after using Mugetsu against Aizen, he turned desperate to fight and protect people. This desperation led him to Ginjo who taught him how to use Fullbring powers.
Fullbring powers help humans whose parents have survived Hollow attacks before to be able to manipulate souls of all things in existence. For eg, chair, table, tea, water, air etc. Using these souls they can tap into the powers of the hollows their parents survived from.
In this his Bankai sword isn’t a straight long sword but is curved and has slight perforation for dealing more damage, if stabbed and pulled.
Also, his reiatsu reaches a new heights.