Effect of Anode on the Capacity Loss of Li-ion Cells with Redox Shuttles During Overcharge

Abstract

Redox shuttles provide a number of overcharge protection cycles for Li-ion cells. Cells with lithium anodes exhibit the largest number of protected overcharge cycles and cells with carbonaceous anodes exhibit the smallest number of protected overcharge cycles, with cells employing lithium titanate (LTO) anodes in the middle of these two extremes. Full cells with ANL-RS2 redox shuttle using lithium iron phosphate (LFP) cathodes and either graphite or LTO anodes were overcharge cycled and analyzed to explain the differing overcharge cycle life. The negative-to-positive (N/P) ratio of LFP-graphite cells decreases more rapidly than that of LFP-LTO cells, resulting in decreased overcharge cycle life. The redox shuttle ANL-RS2 likely undergoes oxidative dehydrogenation and oxygen insertion during overcharge cycling, perhaps catalyzed by the delithiated LFP cathode.