To fight global warming, one of the solutions researchers are working on is to generate electricity from renewable energy sources like solar and wind. But the availability of solar and wind energy is highly intermittent and varies within a day as well as from season to season. To provide a reliable electricity by filling the gap between electricity generation and demand timing, a cost effective, long-term high-energy storage device is required. Zinc air battery is considered as one of the potential options for long-term high-energy storage at very low cost. Discharging zinc will provide electricity whenever it is required. The discharge product, zinc oxide, can be recycled back to zinc by electrodeposition when the electricity generation is excess which serves the energy storage purpose. It is proven that zinc-air battery can have specific energy density equivalent to that of lithium-ion batteries. They are inherently very safe and can be deployed in large scale at low cost due to abundant availability of zinc indigenously. But the parasitic hydrogen evolution reaction (HER) hampers the faradaic efficiency during both recycling and discharging process. To achieve a high round trip energy efficiency and to store recycled zinc for months, HER must be suppressed. Here, a customised mechanically refuellable zinc-air flow battery is being developed to achieve high specific energy, round-trip energy efficiency and long-term storage. With major focus on zinc recycling process, the challenges we are currently facing and possible solutions that can improve energy efficiency will be discussed.