Regulating the growth of aluminum electrodeposits: towards anode-free Al batteries
The high earth abundance and large specific capacity of aluminum Al on either a volume (8040 mAh cm-3) or mass (2980 mAh g-1) basis continues to drive interest in electrochemical cells that utilize metallic Al as the anode. At practical anode capacities uneven, non-planar deposition of Al during battery recharge combine with the high Young’s modulus (EAl=70Ga) of the metal to limit the electrode lifetime in all known electrolytes. Here we study the effect of a thin, textured coating composed of two-dimensional gold nanosheets with strong diffraction from (111) facets and low lattice mismatch for Al, as a substrate for regulating the Al electrodeposit morphology. We report that these coatings are not only effective in preventing Al deposition in non-planar morphologies, but have a large beneficial effect on the reversibility of Al electrodes. In Al plating/stripping studies, the textured Au coatings sustain stable cell operations for 500 cycles or more with a high Coulombic efficiency of over 99%. Full cell Al batteries composed of the Au nanosheets as the anode substrate and graphene as cathode are reported to exhibit capacity retention of 80% after 1000 charge-discharge cycles, and 74% at the 2000th cycle, exceeding the lifetimes (~200 cycles) of comparable Al batteries in which a standard stainless steel material is used as the anode substrate. Our results demonstrate that through rational design of the substrate for Al deposition, both the electrodeposit morphology and cycle life of Al-based batteries can be markedly improved.