In a new study on using seawater green batteries to store renewable energy, researchers developed a new chloride ion-based redox chemistry.

Xiaowei Teng, the James H. Manning professor of Chemical Engineering at the Worcester Polytechnic Institute, and his team, inserted chloride, the richest negatively charged ion in seawater, into iron hydroxide (Fe(OH)2) layered double hydroxide.

Seawater green batteries are a sustainable and cost-effective alternative to lithium-ion batteries. These green batteries use seawater as a source to convert electrical and chemical energy.

The team inserted chloride ions into iron hydroxide, forming a green rust intermediate crystalline material.

The material helped create a one-charge transfer FE(OH)2/ FEOOH conversion reaction while improving the cycling stability of the green battery.

The researchers further designed a small prototype of an aqueous battery powered using a water-based electrolyte. The team said their battery was assembled using electrodes made mostly from abundant elements like iron oxides and hydroxides.

The study claims that the United States produces over 15 million tons of scrap iron waste that goes untreated, and much of this waste rusts. The newly developed rechargeable alkaline iron battery chemistry boasts of repurposing such iron rust waste materials for modern energy storage.

According to Teng, while the team is yet to assess the cost of such a green battery, the eco-friendly design of their aqueous battery allows researchers to study the behavior of many earth-abundant materials that can be a better substitute for lithium.

The researchers highlighted that the seawater green battery developed by them is a potential replacement for the largely used lithium-ion batteries that can be complex for grid storage given its higher cost and due to increased dependence on nature-critical materials like cobalt, lithium, and nickel.

The study titled ‘Chloride-Insertion Enhances the Electrochemical Oxidation of Iron Hydroxide Double Layer Hydroxide into Oxyhydroxide in Alkaline Iron Batteries’ is published in the American Chemical Society’s journal Chemistry of Materials.

In another research, researchers at the Chinese Academy of Sciences claimed to have developed a stable kilowatt-scale aqueous redox flow battery with high-performance organic redox-active molecules for renewables storage.

Another study published by Purdue University studied two categories of solid electrolytes, which are ceramic electrolytes composed of sulfide and oxide and polymer electrolytes. The researchers observed that solid electrolytes provide increased thermal stability of up to 330 degrees Celsius to solid-state lithium-ion batteries compared to those with liquid electrolytes.