Electrochemical characteristics of MCMB and LiNixCo1-xO2 electrodes in electrolytes with stabilizing additives

As part of our continuing efforts to develop advanced electrolytes to improve the performance of lithium-ion cells, especially over wide temperature ranges, we have identified electrolyte additives that can be incorporated into multicomponent electrolyte formulations that result in performance enhancement. Specifically, when electrolyte additives, such as dimethyl acetamide (DMAc) and N-methyl pyrrolidinone, are added to ternary mixtures of carbonates, improved resilience to high-temperature exposure is achieved. A number of experimental lithium-ion cells, consisting of mesocarbon microbead (MCMB) carbon anodes and LiNi(0.8)Co(0.2)O(2) cathodes, have been fabricated to study the effect that these additives have upon the performance. In addition to investigating the use of Lewis base additives that are envisioned to complex any free PF(5), other solid electrolyte interface promoting additives were also studied, including vinylene carbonate (VC) and vinyl ethylene carbonate. Significant improvement in the high-temperature resilience of Li-ion cells containing these additives was observed, with the most dramatic benefit being displayed by the addition of DMAc. When the electrochemical properties of the individual electrodes were analyzed, the degradation of the anode kinetics was slowed most dramatically by the incorporation of DMAc and the greatest retention in the cathode kinetics was observed when VC was added. (C) 2008 The Electrochemical Society.