Effect of anode binders on low-temperature performance of automotive lithium-ion batteries

The effect of styrene-butadiene rubber (SBR)/sodium salt of carboxymethyl cellulose (CMC) and poly(vinylidene fluoride) (PVdF) binders in the anodes on low-temperature performance and cyclability of automotive Li-ion batteries is investigated in 2.0 Ah cylindrical 18650 cells, composed of LiNi0.5Co0.2Mn0.3O2 as cathodes and graphite as anodes. The physical and electrochemical properties of SBR/CMC and PVdF anodes are characterized to compare their low-temperature performance. It is found that the adhesion strength of the SBR/CMC anode is slightly higher than that of the PVdF anode. On the other hand, because of its lower glass transition temperature (Tg), higher ionic conductivity and better absorption of the electrolyte, the PVdF anode results in higher electrical and ionic conductivity than observed in the SBR/CMC anode at low temperatures. These properties of the PVdF anode contribute to smaller impedance and faster Li-ion diffusion. Thus, the PVdF anode exhibits better discharge behavior and cycle performance at low temperatures than the SBR/CMC anode.