Atomistic mechanisms of lithium insertion in amorphous silicon

Understanding the lithium–silicon alloying behavior is essential for achieving maximum charge capacity in the negative electrodes of lithium-ion batteries. Our atomistic simulations show that in amorphous silicon with a disordered network structure, inserted lithium atoms can find equilibrium positions in the interstices of big rings. Alternatively, lithium is incorporated into the network by the destruction and reformation of smaller rings. These atomic-level mechanisms are characterized by using the network topology measure of ring statistics, which are correlated to the lithiation responses of silicon electrodes. The results reveal the influence of lithium concentrations on the electro-chemical–mechanical behavior of silicon. Implications on the reversibility and dynamics of the lithiation process are discussed.

▶ Lithiation of amorphous Si is critically controlled by the evolution of atomic-level structures. ▶ The volume and voltage responses of lithiated Si can be directly correlated to the variation of ring statistics, which characterizes the medium range order of an amorphous structure. ▶ The Li–Si alloying behavior depends sensitively on the local Li concentration.