A modulated MOF as a modification layer on copper foil for lithium dendrite suppression

Abstract

Lithium metal is considered a promising anode material due to its high theoretical capacity and low redox potential. However, after repeated charging and discharging, the lithium metal electrode tends to form lithium dendrites and dead lithium, which can penetrate through the separator and cause short circuits. In this study, Cu-BTC (Cu₃(BTC)₂) metal–organic frameworks (MOFs) with a manipulated specific surface area (SSA) and particle size using an acetate buffer modulator were used as a modification layer on copper foil to enhance electrode cycle life. Utilizing the modulator for Cu-BTC increased the cycle life from 95 to 220 cycles at a current density of 1 mA cm⁻² when the SSA was doubled. The modification layer with the smallest Cu-BTC size reached up to 520 cycles compared to unmodulated large MOFs of 80 cycles at 1 mA cm⁻². Furthermore, to improve the wettability, lithiophilic silver was added to Cu-BTC. Compared to undecorated MOFs, the cycle life was slightly increased to 115 cycles in silver-doped Cu-BTC with large particle sizes. However, silver doping was detrimental to the cycle life of small-sized Cu-BTC, which decreased to 70 cycles at 1 mA cm⁻². The results indicate that silver doping was effective when the MOF was large. The MOF particle size, rather than silver introduction, significantly affects the overall electrochemical performance of the electrode.