Carbon-Laminated Silicon/Graphene Composite Anodes with Improved Capacity and Cycling Stability

An unconventional route was adopted for fabricating Si/graphene composite anodes. Well crystallized silicon powders purified from the silicon waste mortar of solar cell fabrication were mixed with graphene suspended polyvinylidene fluoride (PVDF) solutions, and calcined directly on metal current collectors. It was found that PVDF was pyrolyzed to form a carbon scaffold which laminated the Si and graphene. The graphene sheets were able to hold the Si powers, preventing them from stress-cracking due to large volume change during charge and discharge processes. Silicon anodes using conventional coating method with PVDF binder and carbon black were also fabricated for comparison. The carbon laminated Si anodes (Si/C) exhibit an initial delithiation capacity of more than 2500 mAh/g at 0.1 C, which is greatly higher than the pristine Si anode (capacity of only 8 mAh/g at 0.1 C). By adding graphene in the composite, the carbon laminated Si/graphene anodes show improved cycling stability, with a 1 C delithiation capacity of 1420 mAh/g after 60 cycles, which is twice as high as Si/C anodes. The results indicate that high capacity and high cycling stability can be achieved by a pyrolysis based carbon lamination process in which graphene and Si powders are attached to each other.