Synthesis of binder-like molecules covalently linked to silicon nanoparticles and application as anode material for lithium-ion batteries without the use of electrolyte additives

Abstract

Abstract A chemically modified silicon anode is prepared for application as anode in lithium-ion batteries by covalent attachment of polyacrylic acid to enable self-adhesion between the active material particles. The polyacrylic acid polymer is formed by atom transfer radical polymerization using 1-(bromoethyl)benzene initiator groups initially bonded to a hydrogenated silicon surface. The grafting of 1-(bromoethyl)benzene and polyacrylic acid is confirmed by various material characterization techniques. The electrochemical performance of the silicon anodes is also evaluated by galvanostatic cycling. The chemically modified composite silicon anode (with active material loading of 0.9–1 mg cm −2 ) showed a significantly improved performance in terms of: gravimetric capacitance (more than 2000 mAh g −1 ) after 300 cycles and 80% capacity retention with an average 99.6% Coulombic efficiency at a current density of 0.34 A g −1 . However, the unmodified electrode cycled 75 times in the same conditions only retains 46% of its initial capacity with an average 95.1% Coulombic efficiency. The new composite Si electrode performs better at high charge/discharge rate and allows the use of larger proportion of the active material by reducing the amount of binder. It is noteworthy that these composite silicon electrodes are tested without the use of expensive electrolyte additives.