Lithium-ion (Li-ion) batteries are a widely used and important technology. Recent expansion of Li-ion batteries into automotive applications has resulted in intense scientific interest. In Li-ion batteries the multitude of reactions occurring under harsh conditions along with difficulties in characterization have made calculations and simulations an important part of this research. Application of atomic level methods has expanded the knowledge concerning the basic chemistry of the Li-ion battery, especially as applied to electrolytes and their relationship to the solid electrolyte interphase (SEI), a key component of many Li-ion batteries. In this chapter we review methods for atomic-level computations and simulations of Li-ion battery electrolytes with a focus on the chemistry of the organic solvents of the electrolyte. Each section includes a short overview of computational methodology and some applications, followed by a highlight of recent work. The first section describes how quantum chemical methods can be used to interrogate problems in Li-ion batteries. The highlighted work in this section is a study of the reactions of organic solvent on model systems to form an oligomeric SEI layer. In the next section the use of classical and ab initio molecular dynamics to simulate reactions in the SEI layer is reviewed and two studies are highlighted. The final method is the use of data from ab initio calculations to screen electrolytes for improved reactivity. The chapter closes with a section on the future outlook of atomic-level modeling of Li-ion electrolytes.