Electrolytes for lithium-ion batteries operating at extreme conditions

An electrolyte, comprising:

• a lithium salt;
• a nonaqueous solvent comprising a carboxylate ester, a carbonate ester other than ethylene carbonate (EC), vinylene carbonate (VC), or fluoroethylene carbonate (FEC), an orthoformate, a sulfate ester, an ether, a sulfone, a nitrile, or any combination thereof, wherein the lithium salt is soluble in the nonaqueous solvent;
• a diluent comprising a fluoroalkyl ether, a fluorinated orthoformate, a fluorinated carbonate, a fluorinated borate, a fluorinated phosphate, a fluorinated phosphite, or any combination thereof, wherein the lithium salt has a solubility in the diluent at least 10 times less than a solubility of the lithium salt in the nonaqueous solvent;
• and
• an additive having a different composition than the lithium salt, a different composition than the nonaqueous solvent, and a different composition than the diluent, wherein the additive does not consist of an organophosphate,
• the electrolyte having a lithium salt-nonaqueous solvent-additive-diluent molar ratio of 1:x:y:z where 0.5≤x≤8, 0≤y≤2, and 0.5≤z≤5,
• wherein if the nonaqueous solvent consists of one or more carbonate esters, the additive does not consist of fluoroethylene carbonate (FEC) or x/y>4.