Catanionic synergetic effect of sodium dodecyl sulphate and cetyl trimethyl ammonium bromide surfactants on the electrochemical performance of porous carbon anodes in lithium-ion batteries

Carbon-derived materials are suitable for use as anodes in lithium-ion batteries due to low production cost and abundance. However, there is a need to improve the electrochemical performance with various modifications due to the limited capacity. In this study, a porous carbon is modified with anionic sodium dodecyl sulphate (SDS) and cationic cetyl trimethyl ammonium bromide (CTAB) surfactants and prepared as an anode for use in lithium-ion batteries. Morphological and structural properties change with the addition of surfactants, and the use of only one or two of them together has different effects. The morphology formed by adding only SDS is homogeneous and only CTAB is heterogeneous. When both surfactants are used SDS also provides homogeneous dispersion of CTAB. The changes in I_2D/I_G and I_D/I_G ratios obtained from Raman analyses show that the layer arrangement and the ratio of defects in the structure have changed. Electrochemical performances with different surfactant amounts are compared by using charge/discharge tests, cyclic voltammetric tests and differential capacity analysis (dQ/dV). The combined use of SDS and CTAB creates a synergetic effect (catanionic) and increases the capacity nearly 1.5 times by improving wetting, amount of lithium-ion storage areas and reducing the irreversible loss of capacity caused by solid electrolyte interface.