Battery systems based on lithium difluorophosphate

A lithium-ion battery comprising:

• a negative electrode;
• a positive electrode;
• and
• a nonaqueous electrolyte consisting essentially of a lithium salt, a nonaqueous solvent and an additive mixture, wherein the nonaqueous solvent comprises methyl acetate, the lithium salt consists essentially of lithium hexafluorophosphate, and the additive mixture comprises:
• a first operative additive of 1,3,2-dioxathiolane-2,2-dioxide or another sulfur-containing additive selected from the group consisting of:
• methylene methane disulfonate, trimethylene sulfate, 3-hydroxypropanesulfonic acid γ-sultone, and glycol sulfite, wherein a concentration of the first operative additive is at a concentration of at most about 2% by weight;
• and
• a second operative additive of fluoroethylene carbonate, wherein a concentration of the second operative additive is at a concentration of at most about 2% by weight;
• wherein the positive electrode comprises a grain size of greater than 0.5 micrometers;
• wherein the battery has 95% retention of initial capacity after 200 cycles between 3.0 V and 4.3 V at a charging rate of C/3 CCCV at 40° C.