Abstract: Provided herein is an apparatus. The apparatus can include a battery cell. The battery cell can include an electrode. The apparatus can include a first solid electrolyte interphase on the electrode. The first solid electrolyte interphase can be formed from a first electrolyte having a salt concentration greater than or equal to 1 M. The apparatus can include a second solid electrolyte interphase on the electrode. The second solid electrolyte interphase can be formed from a second electrolyte different from the first electrolyte.

Abstract: A battery cell includes a cathode including a cathode active material; an anode including an anode active material; and an electrolyte including a non-aqueous polar solvent, a lithium salt, and a (R3SiO)3P(O), a (R3SiO)3P, or a mixture of any two or more thereof; wherein: R is C1 to C4 alkyl; the cathode active material has an areal density of at least 10 mg/cm2 and a press density of at least 1.7 g/cc; the anode active material has an areal density of at least 5 mg/cm2 and a press density of at least 1.3 g/cc; and the conductivity of the cathode and/or anode is increased compared to the same battery cell without the (R3SiO)3P(O), the (R3SiO)3P, or the mixture of any two or more thereof.