An investigation of thermal stabilizing additives and interactions between electrolytes and electrodes in lithium ion batteries.

摘要

Capacity loss of lithium ion batteries develop over the period of a few years at room temperature and accelerate at elevated temperatures. It results partly from the electrolyte decomposition and degradation of solid electrolyte interface (SEI) on the surface of electrode materials. Efforts have been made to improve performances of lithium ion batteries based on the role of electrolyte and its interactions with the electrode materials.; Dissociation of LiPF6 is the source of instability of the LIPF6-carbonate based electrolyte. The generated acidic species, PF5, HF and POF3, initiate and catalyzed the decomposition of the electrolyte. A series of Lewis bases were found to stabilize the electrolyte through reversible binding of PF5.; LiCoO2 and LiNi0.8Co0.2O2 cathode particles were also found to stabilize the electrolyte. Investigation of thermal reactions between electrolyte and the surface of cathode particles reveals that residual Li2CO3 on the surface of metal oxides is responsible for their stabilizing ability for the electrolyte. The thermal reactions deposit surface films similar to those observed on the cathode separated from aged lithium ion cells. Addition of Lewis bases to the electrolyte inhibits the growth of surface films on the cathode metal oxides stored with the electrolyte.; Additives were tested in lithium ion batteries and found to prolong the battery lifetime and improve the battery capacity retention after aging at elevated temperature. Comparative analyses of the electrodes from the aged batteries with different additives indicate that our additive inhibit the film buildup on the electrodes.