In this paper, we introduce the notion of derivations of Lie 2-algebras and construct the associated derivation Lie 3-algebra. We prove that isomorphism classes of non-abelian extensions of Lie 2-algebras are classified by equivalence classes of morphisms from a Lie 2-algebra to a derivation Lie 3-algebra.

In this paper, we construct the projective resolution of arbitrary symmetric 2-group, define the derived 2-functors in (2-SGp) and give some related properties of the derived 2-functors.

In this paper, we will construct the injective resolution of any R-2-module, define the right derived 2-functor, and give some related properties of the derived 2-functor in (R-2-Mod).