Zinc-anode battery overcomes problem of dendrite formation

A prototype zinc-anode battery system developed at the City University of New York has overcome the problem of dendrite formation and will be ready for commercialisation by autumn this year.

According to the college, zinc-anode batteries offer an environmentally friendlier and less costly alternative to nickel-cadmium (Ni-Cd) batteries and, in the longer term, could replace lead-acid batteries at the lower-cost end of the market.

However, the challenge of dendrite formation associated with zinc had to be addressed, as dendrites (crystalline structures) cause batteries to short out.

To prevent dendrite build-up, researchers developed a flow-assisted zinc-anode battery with an advanced battery management system (BMS) that controls the charge/discharge protocol.

To demonstrate the new technology and its applications, which range from peak electricity demand reduction to grid-scale energy storage, they have assembled a 36 kilowatt-hour (kWh) rechargeable battery system.

The system is said to consist of 36 individual 1kWh nickel-zinc flow-assisted cells strung together and operated by the BMS. In peak electricity demand reduction, batteries charge during low-usage periods and discharge during peak-demand periods, when surcharges for power usage are high.

‘This is affordable, rechargeable electricity storage made from cheap, non-toxic materials that are inherently safe,’ said Dr Sanjoy Banerjee, director of the college’s Energy Institute. ‘The entire Energy Institute has worked on these batteries — stacking electrodes, mounting terminals, connecting to the inverters — and they are going to be a game changer for the electric grid.’

The batteries are designed for more than 5,000–10,000 charge cycles and a useful life exceeding 10 years. The demonstration system is being expanded currently to 100kWh, with another 200kWh to be installed later this year. 

Banerjee believes initial applications for the batteries exist in industrial facilities and large, commercial properties. The Ni-Cd batteries that would be initially replaced are used in applications that range from back-up power for server farmers to very large starter motors. Other large-scale Ni-Cd applications include grid support, such as a system in Alaska that deploys a 45MW Ni-Cd battery array.

The Energy Institute’s zinc-anode battery system can be produced for a cost of between $300/kWh (£186/kWh) and $500/kWh, which for many applications has a three- to five-year payback period. The cost is being reduced and is expected to reach $200/kWh with a year.

To commercialise the batteries, researchers plan to have a company operational by autumn this year, with the goal of breaking even within two years, Banerjee said in a statement.