Abstract: A battery electrolyte solution contains from 0.001 to 20% by weight of certain phosphorus-sulfur compounds. The phosphorus-sulfur compound performs effectively as a solid-electrolyte interphase (SEI) forming material. The phosphorus-sulfur compound has little adverse impact on the electrical properties of the battery, and in some cases actually improves battery performance. Batteries containing the electrolyte solution form robust and stable SEIs even when charged at high rates during initial formation cycles.