CTAB-Influenced Electrochemical Dissolution of Silver Dendrites

Dendrite formation on the electrodes of a rechargeable battery during the charge–discharge cycle limits its capacity and application due to short-circuits and potential ignition. However, understanding of the underlying dendrite growth and dissolution mechanisms is limited. Here, the electrochemical growth and dissolution of silver dendrites on platinum electrodes immersed in an aqueous silver nitrate (AgNO₃) electrolyte solution was investigated using in situ liquid-cell transmission electron microscopy (TEM). The dissolution of Ag dendrites in an AgNO₃ solution with added cetyltrimethylammonium bromide (CTAB) surfactant was compared to the dissolution of Ag dendrites in a pure aqueous AgNO₃ solution. Significantly, when CTAB was added, dendrite dissolution proceeded in a step-by-step manner, resulting in nanoparticle formation and transient microgrowth stages due to Ostwald ripening. This resulted in complete dissolution of dendrites and “cleaning” of the cell of any silver metal. This is critical for practical battery applications because “dead” lithium is known to cause short circuits and high-discharge rates. In contrast to this, in a pure aqueous AgNO₃ solution, without surfactant, dendrites dissolved incompletely back into solution, leaving behind minute traces of disconnected silver particles. Finally, a mechanism for the CTAB-influenced dissolution of silver dendrites was proposed based on electrical field dependent binding energy of CTA⁺ to silver.