High energy batteries urgently required to power electric vehicles are restricted by a number of challenges, one of which is the sluggish kinetics of cell reactions under low temperatures. A novel approach is reported to improve the low temperature performance of high energy batteries through rational construction of low impedance anode and cathode interface films. Such films are simultaneously formed on both electrodes via the reduction and oxidation of a salt, lithium difluorobis(oxalato) phosphate. The formation mechanisms of these interface films and their contributions to the improved low temperature performances of high energy batteries are demonstrated using various physical and electrochemical techniques on a graphite/LiNi0.5Co0.2Mn0.3O2 battery using 1 m LiPF6‐ethylene carbonate/ethyl methyl carbonate (1/2, in weight) baseline electrolyte. It is found that the interface impedances, especially the one on the anode, constitute the main obstacle to capacity delivery of high energy batteries at low temperatures, while the salt containing fluorine and oxalate substructures used as additives can effectively suppress them.

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The energy density of commercial Li-ion batteries (LIBs) using LiCoO2 is adversely affected by the limited access to the Li stored in the CoO2 lattice, which is imposed partially by the instability of carbonate-based electrolytes at potentials higher than 4.5 V. In this work, we report a novel approach to fully utilize these extra Li via simultaneously stabilizing anode and cathode interfaces with a designed additive, 4-propyl-[1,3,2]­dioxathiolane-2,2-dioxide (PDTD), which strongly coordinates with Co ions dissolved in electrolytes while decomposing to form protective interphases on both cathode and anode surfaces. The Co ions present in the electrolyte deposit on the anode in the form of a coordination complex with PDTD, avoiding the formation of Co metal that will catalyze the reduction decomposition of the additive-free electrolyte. The presence of PDTD in the electrolyte enables a higher charging potential of 4.45 V for LiCoO2/graphite cells, which significantly improves the energy density and cycling stability of this cathode chemistry that has already been used extensively in commercial LIBs.

Lithium bisoxalatodifluorophosphate (LiBODFP) is a promising multifunctional lithium salt-type electrolyte additive used to enhance the performance of 5 V LiNi0.5Mn1.5O4 (LNMO)-based lithium-ion batteries (LIBs).

Performances of lithium-ion batteries at subambient temperatures are extremely restricted by the resistive interphases originated from electrolyte decomposition, especially on the anode surface. This work reports a novel strategy that an anode interphase of low impedance is constructed by applying an electrolyte additive dimethyl sulfite (DMS). Electrochemical measurements indicate that the as-constructed interphase provides graphite/LiNi0.5Co0.2Mn0.3O2 pouch cells with excellent low-temperature performance, outperforming the interphase constructed by 1,3,2-dioxathiolane 2,2-dioxide (DTD), a common commercially used electrolyte additive. Spectral characterizations in combination with theoretical calculations demonstrate that the improved performance is attributed to the unique molecular structure of DMS, which presents appropriate reduction activity and constructs the more stable and ionically conductive anode interphase due to the weaker combination of its reduction product with lithium ions than DTD. This rational design of interphases via an additive structure has been proven to be a low cost but rather an effective approach to tailor the performances of lithium-ion batteries.