Effect of polymeric binder type on the thermal stability and tolerance to roll-pressing of spherical natural graphite anodes for Li-ion batteries

The polymeric binder is seen to affect the thermal stability and deformation of spherical graphite used in lithium ion battery anodes. Spherical natural graphite anodes are prepared using three different binders: two aqueous-based binders, polyacrylic acid (PAA) and a mixture of carboxy-methyl cellulose and styrene butadiene rubber (abbreviated CMC/SBR), and an organic-based binder, polyvinylidene fluoride (PVDF). The thermal stability of fully lithiated electrodes is measured by differential scanning calorimetry (DSC). The PAA binder effectively suppresses heat evolution (43% (PVDF) and 23% (CMC/SBR) less heat) at low temperatures up to 200 °C during DSC scans of the lithiated electrodes, compared to the PVDF and CMC/SBR binders. In addition, the PAA binder allows the graphite electrode to maintain an appropriate porous structure (13% greater porosity than the PVDF and CMC/SBR electrodes) even at high electrode density after 6 kgf cm−2 compression, thus leading to enhanced effective cycles (11% (PVDF) and 60% (CMC/SBR) greater capacity after 50 cycles).