(Invited) Capabilities and Opportunities for Next-Generation Ag–3D Zn Batteries

Abstract

Silver–zinc batteries offer high specific energy (up to 190 Wh kg–1) and the highest specific power of any known commercial battery (up to 600 W kg–1 continuous power and 2,500 W kg–1 pulses). The Ag–Zn system operates using water-based electrolytes and nonhazardous active materials, providing an ideal battery alternative to Li-ion (flammable; explosive) and Pb-acid (toxic) in the diverse markets where these drawbacks must be avoided. Despite the many advantages of Ag–Zn batteries, adoption beyond specialized applications is hindered by a Zn anode that accesses only middling zinc specific capacity and has limited rechargeability. We have recently overcome these hurdles by developing a monolithic Zn sponge electrode that exhibits cycling durability in prototype Ni–Zn cells and a 50% greater specific capacity in Zn–air cells, both relative to the same systems that use conventional powder-bed Zn electrodes. The cathodes used in those chemistries are ill-equipped to counter-balance the specific power that the Zn sponge has to offer. Silver–zinc presents higher power and energy density than Ni–Zn batteries and a more market-ready cathode than Zn–air, making Ag–3D Zn an attractive battery chemistry with which to demonstrate the triumvirate of rechargeability, high specific energy, and high specific power. We present prototype Ag–3D Zn cells that discharge to record-breaking extreme depths-of-Zn-discharge, support rechargeability rarely seen in the Ag–Zn system, and can operate at 104–105 W kgZn –1. Toward the goal of developing next-generation Ag–3D Zn batteries, we also describe our breakthroughs and existing challenges in: (i) the design of full cell Ag–3D Zn prototypes; (ii) the fabrication of beta 2.0 Zn sponges with tunable density; and (iii) the preparation of AgxO cathodes that support the high performance of Zn sponge anodes.