A nanowire battery that won’t die

Imagine a battery that never stops holding a charge. An experimental energy storage electrode lasts as long as researchers have had the patience to charge and recharge it—so far, more than 100,000 times (ACS Energy Lett. 2016, DOI: 10.1021/acsenergylett.6b00029). Nanowire battery electrodes can provide a lot of power in a small footprint, says Reginald M. Penner of the University of California, Irvine, but they are prone to breaking. Penner’s group used a test setup to study manganese dioxide-coated gold nanowires, a potential lithium-ion battery cathode material. The group tested the wires with a typical liquid electrolyte and with a polymethyl methacrylate (PMMA) gel electrolyte—commonly used in solid-state batteries. Cathodes paired with the liquid electrolyte survived 2,000 to 8,000 charge cycles, but the one with PMMA survived 100,000 full charges and discharges—even in a test system designed to encourage failure. The gel may hold the MnO₂ in place, Penner says, preventing it from breaking off of the gold below. Or the gel may slowly leak into pores in the MnO2 and plasticize it, preventing fracturing, he suggests.