We construct a new spectral sequence beginning at the Khovanov homology of a link and converging to the Khovanov homology of the disjoint union of its components. The page at which the sequence collapses gives a lower bound on the splitting number of the link, the minimum number of times its components must be passed through one another in order to completely separate them. In addition, we build on work of Kronheimer and Mrowka and Hedden and Ni to show that Khovanov homology detects the unlink.
Joshua Batson. Cotton Seed. "A link-splitting spectral sequence in Khovanov homology." Duke Math. J. 164 (5) 801 - 841, 1 April 2015. https://doi.org/10.1215/00127094-2881374