The effect of additives upon the ability of meso-carbon microbead (MCMB) carbon/ LiNi x Co 1−x O 2 lithium-ion cells containing methyl butyrate-based electrolytes to provide operation over a wide temperature range (−60 to +60 • C) was investigated. A number of electrolyte additives were studied, including mono-fluoroethylene carbonate (FEC), lithium oxalate, vinylene carbonate (VC), and lithium bis(oxalato borate) (LiBOB). The intent of incorporating these additives into methyl butyrate-based electrolytes is to widen the operating temperature range of these systems, especially at warm temperatures. A number of formulations were investigated in experimental three-electrode MCMB/ Li x Ni y Co 1−y O 2 lithium-ion cells, based on an electrolyte that has previously been demonstrated to provide good low temperature performance (to −60 • C), namely 1.00M LiPF 6 in ethylene carbonate (EC) + ethyl methyl carbonate (EMC) + methyl butyrate (MB) (20:20:60 v/v%). In addition to studying the charge and discharge behavior of the cells, a number of electrochemical techniques were also employed, including Electrochemical Impedance Spectroscopy (EIS), Tafel polarization and linear polarization to understand the interfacial effects on the intercalation kinetics.

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The effects of lithium-ion electrolyte additives in ester-rich low temperature electrolyte blends, including vinylene carbonate (VC), lithiuma bis(oxalato) borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), propane sultone (PS) and lithium bis(fluorosulfonyl)imide (LiFSI), upon the likelihood of lithium plating are investigated in graphite-LiNiCoAlO2 three-electrode cells. Although metallic lithium is generally absent in lithium-ion cells, certain conditions, particularly charging at low temperature and/or at high rate, can lead to lithium metal plating on the surface rather than intercalating into the carbon anode. Metallic lithium reacts with the electrolyte and forms dendrites upon continuous plating, which can lead to cell shorting and capacity loss. The type of carbon anode, electrolyte, and solid-electrolyte-interphase (SEI) all influence this behavior. SEI stabilizing additives are generally detrimental to low temperature charging performance, however, 0.1 M LiFSI was found to be advantageous to low temperature charging. When charged at a C/5 rate to 4.10 V, lithium plating was evident at ∼20 °C higher temperature with VC and LiBOB additives compared to the baseline electrolyte without any additives (plating appears at −10 °C rather than −30 °C with the baseline electrolyte). In contrast, the cell containing 0.10 M LiFSI as an additive did not display lithium plating until −40 °C, or 10 °C lower than the baseline cell.

Exploration missions to the moons of the outer planets (such as Europa) pose unique challenges regarding the design of the spacecraft power source. Current aerospace qualified primary battery technologies cannot adequately meet the mass and volume requirements of proposed missions. Although they have not been used in prior deep space landed missions, lithium carbon-fluoride (Li/CF x ) technologies were identified as a potentially viable option, both with and without blends of manganese dioxide (MnO 2 ). To meet the performance requirements over the intended operating conditions of future NASA missions requires further development of this technology, in particular in the delivery of a high specific energy at moderate to low temperatures, and low discharge rates. A cell development effort was therefore pursued with an industrial battery cell manufacturer. Low (50 mA) and medium (250 mA) discharge rates were used to assess the performance of D-size cells under mission relevant conditions, between 0 • C and −40 • C. Select AA-size and C-size cells were also evaluated using similar rates scaled to the lower cell capacities. Developmental Li/CF x -MnO 2 D-size cells designed for higher specific energy over these conditions were fabricated and tested, targeting operation between 0 and −40 • C and a 50 mA constant discharge current, as the baseline operating condition.

The development and subsequent incorporation of flame retardant additives (FRAs) has become a priority for Li-Ion battery research and development. Triphenyl phosphate (TPP) was studied to ascertain the safety benefits and electrochemical performance when incorporated into a LiPF 6 /ethylene carbonate (EC)/ethyl methyl carbonate (EMC) electrolyte system. The flammability of electrolytes containing TPP was investigated via self-extinguishing time and flash point analysis. The electrochemical stability was studied by cyclic voltammetry (CV), battery cycling in graphite/LiNi 0.8 Co 0.2 O 2 cells, electrochemical impedance spectroscopy (EIS) and Tafel polarization. In order to better understand the role of TPP, ex-situ surface analysis of the cycled electrodes was conducted with X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Incorporation of TPP results in a moderate decrease in the flammability of the electrolyte with relatively minor detrimental effects on the performance of the cells and thus is a promising additive for lithium ion batteries.