prismatic zinc air cells with characteristics suitable for both stationary storage and mobility applications. Mechanical recharge Rechargeable systems may mechanically replace the anode and electrolyte, essentially operating as a refurbishable primary cell, or may use zinc powder or other methods to replenish the reactants. Mechanically recharged systems were investigated for military electronics uses in the 1960s because of the high energy density and easy recharging. However, primary lithium batteries offered higher discharge rates and easier handling. Mechanical recharging systems have been researched for decades for use in electric vehicles. Some approaches use a large zinc–air battery to maintain charge on a high discharge–rate battery used for peak loads during acceleration. Zinc granules serve as the reactant. Vehicles recharge via exchanging used electrolyte and depleted zinc for fresh reactants at a service station. The term zinc–air fuel cell usually refers to a zinc–air battery in which zinc metal is added and zinc oxide is removed continuously. Zinc electrolyte paste or pellets are pushed into a chamber, and waste zinc oxide is pumped into a waste tank or bladder inside the fuel tank. Fresh zinc paste or pellets are taken from the fuel tank. The zinc oxide waste is pumped out at a refueling station for recycling. Alternatively, this term may refer to an electrochemical system in which zinc is a co-reactant assisting the reformation of hydrocarbons at the anode of a fuel cell. The benefits of mechanical recharging systems over rechargeable batteries include the decoupling of energy and power components, providing design flexibility for different charge rate, discharge rate, and energy capacity requirements. Materials Catalysts Cobalt oxide/carbon nanotube hybrid oxygen reduction catalyst and nickel-iron layered double hydroxide oxygen evolution cathode catalysts exhibited higher catalytic activity and durability in concentrated alkaline electrolytes than precious metal platinum and iridium catalysts. The resulting primary zinc–air battery showed peak power density of ~265 mW/cm3, current density of ~200 mA/cm3 at 1 V and energy density >700 Wh/kg. Rechargeable Zn–air batteries in a tri-electrode configuration exhibited an unprecedented small charge–discharge voltage polarization of ~0.70 V at 20 mA/cm3, high reversibility and stability over long charge and discharge cycles. In 2015, researchers announced a carbon-based, metal-free electrocatalyst that works efficiently in both reduction and oxygenation reactions. Organic compound aniline, polymerized into long chains in a phytic acid solution, was freeze-dried into a stable, mesoporous carbon aerogel with 2–50 nm pores, providing high surface area and room for