High Capacity Silicon/Carbon-Fiber-Scaffold Anodes

A major cause of capacity fading of silicon anodes is the growth of the primary and secondary SEI. Thus, space must be allocated for this SEI growth. We report here on a novel anode structure consisting of a carbon-fiber scaffold on which SiNPs were coated. The space between the carbon fibers enables electrolyte penetration and SEI growth. We achieved an unprecedented combination of remarkable performance characteristics: high loadings of 2-4mAh/cm², a very low irreversible capacity (_˜20% for the 3-4mAh/cm² anodes), current efficiency greater than 99%, cycle stability both in half cells and in full battery and fast charge–discharge rates (up to 1C-rate). The capacity of the fiber-scaffold anode was in the range of 900 to 1400mAh/g of anode – three to four times that of the commercial graphite anode. These anodes have been cycled for over 100 cycles, exhibiting a stable cycle life (cells are still running). It was found that the growth in the thickness of the SEI layer and the concomitant increase in its resistivity, represents the major reason for the observed capacity loss of the anode. Our data reveal that the novel-architecture anode is expected to meet the requirements of lithium-ion batteries for portable applications.