(265f) Impact of Cell Chemistry and Additive Selection on Cell Performance of Ester-Based Li-Ion Batteries at Extreme Low Temperature

Conventional liquid electrolyte lithium-ion batteries (LIBs) typically suffer from poor performance at subzero temperatures due to electrolyte freezing, kinetic limitations in the (de)solvation of Li+ ions at the electrodes, and increased dendrite formation. At extreme low temperatures of -50C, conventional LIBs fail completely. As electrification continues globally, new solutions are necessary to maintain LIB reliability in the face of the challenging environmental conditions where these LIBs will be deployed.

One approach to increasing the reliability of liquid electrolyte LIBs in these challenging conditions is to replace the conventional carbonate electrolyte solvents with low freezing esters, for example methyl propionate (MP). In combination with appropriate solid electrolyte interface (SEI) formers such as fluoroethylene carbonate (FEC), several recent studies¹ have shown that MP-FEC based electrolyte formulations have excellent low temperature performance, with >80% capacity retention over 1000+ cycles at 2C² , and ~60% discharge capacity at -40C³, relative to room temperature operation.

Though recent results are promising, these new formulations still have challenges. Lithium bis(trifluoromethanesulfonyl)imide (LITFSI) salt, which is commonly used in these extreme low temperature electrolyte formulations, is known to corrode aluminum metal, the most used current collector in LIB cathodes, at high voltage and requires special additives, such as lithium difluoro(oxalato)borate salt (LIDFOB) to protect the cathode⁴. Similar issues can plague the various anode and cathode active materials most used in LIBs, which can each require their own electrolyte additives. These additives can severely impact the solvation structures of the MP-FEC electrolyte, and thus the (de)solvation kinetics that drive extreme low temperature performance. In this work, we will demonstrate the interplay of cell chemistry and electrolyte additives, and how those interactions govern the low-temperature electrochemical behavior of ester-based LIBs.

1 Li et al., “Electrolyte Design Enables Rechargeable LiFePO4/Graphite Batteries from −80°C to 80°C”; Xiang et al., “Enhanced Low-Temperature Resistance of Lithium-Ion Batteries Based on Methyl Propionate-Fluorinated Ethylene Carbonate Electrolyte”; Cho et al., “Enabling the Low-Temperature Cycling of NMC||Graphite Pouch Cells with an Ester-Based Electrolyte.”

2 Li et al., “Electrolyte Design Enables Rechargeable LiFePO4/Graphite Batteries from −80°C to 80°C.”

3 Cho et al., “Enabling the Low-Temperature Cycling of NMC||Graphite Pouch Cells with an Ester-Based Electrolyte.”

4 Kalhoff et al., “Safer Electrolytes for Lithium-Ion Batteries.”