Monolithic Nanoporous Zn Anode for Rechargeable Alkaline Batteries.

ABSTRACT

The fabrication of monolithic nanoporous zinc bears its significance in safe and inexpensive energy storage; it can provide the much needed electrical conductivity and specific area in a practical alkaline battery to extend the short cycle life of a zinc anode. Although this type of structure has been routinely fabricated by dealloying, that is, the selective dissolution of an alloy, it has not led to a rechargeable zinc anode largely because the need for more reactive metal as the dissolving component in dealloying limits the choices of alloy precursors. Here, we apply the mechanism of dealloying, percolation dissolution, to design a process of reduction-induced decomposition of a zinc compound (ZnCl2) for nanoporous zinc. Using naphthalenide solution, we confine the selective dissolution of chloride to the compound/electrolyte interface, triggering the spontaneous formation of a network of 70 nm wide percolating zinc ligaments that retain the shape of a 200 µm thick monolith. We further reveal that this structure, when electrochemically oxidized and reduced in an alkaline electrolyte, undergoes surface-diffusion-controlled coarsening toward a quasi-steady-state with a length scale of ∼500 nm. The coarsening dynamics preserves the continuous zinc phase, enabling its uniform reaction and 200 cycles of stable performance at 40% depth of discharge (328 mAh/g) in a Ni-Zn battery.