New stack design enhances vanadium flow batteries

A team of researchers from the Chinese Academy of Sciences (CAS) has developed a 70 kW-level high power density vanadium flow battery stack that has a volume power density of 130 kW/m³. Vanadium flow batteries are one of the preferred technologies for large-scale energy storage. Stack is the core component of a vanadium flow battery. The power density determines the cost of the stack; the higher the power density, the smaller the stack volume, resulting in lower cost under the same power output conditions.

Based on self-developed highly selective weldable porous composite membranes and weldable highly conductive bipolar plates, the researchers developed a 70 kW-level stack, using a short flow path, an ultra-thin battery structure, and low flow resistance and high distribution uniformity flow channels. The energy efficiency of this stack is 81.0% under 70 kW rated power charge and discharge conditions, and the energy efficiency is 82.1% under 60 kW constant power change and discharge conditions. In addition, the stack operates stably after more than 1200 cycles, with 1.7% energy decay.

By using this stack, a 20-foot container energy storage unit module can be upgraded from 250 to 500 kW without greatly increasing the size of power units. “This 70 kW-level stack can promote the commercialisation of vanadium flow batteries. We believe that the development of this stack will improve the integration of power units in energy,” said Professor LI Xianfeng, who led the research.

Image credit: iStock.com/Petmal