The Effect of Additives upon the Performance of MCMB/LiNi_xCo_1−xO₂Li-Ion Cells Containing Methyl Butyrate-Based Wide Operating Temperature Range Electrolytes

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.