Northvolt has filed a patent for a process that allows for the direct preparation of battery grade metal sulfate solutions from electrolytically produced metal objects. The process involves subjecting the metal objects to an aqueous leaching solution containing acid leaching agents and liquid oxidizing agents at an elevated temperature and with vigorous mixing. The patent also includes a leaching arrangement comprising a leaching column or reaction vessel. GlobalData’s report on Northvolt gives a 360-degree view of the company including its patenting strategy. Buy the report here.
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Process for preparing battery grade metal sulfate solutions
A recently filed patent (Publication Number: US20230312368A1) describes a process for preparing battery grade metal sulfate solutions. The process involves subjecting electrolytically produced metal objects to an aqueous leaching solution at an elevated temperature and acid pH in a continuous process with mixing. The leaching solution consists of at least one acid leaching agent and an oxidizing agent in liquid form.
In one embodiment of the process, the mixing is achieved by recirculating the aqueous leaching solution through a leaching column operating in counter-current mode. This ensures efficient mixing and contact between the metal objects and the leaching solution.
The resulting battery grade metal sulfate solution has a residual sulfuric acid concentration in the range of 0-10 g/l, preferably 0-6 g/l. The specific metal objects used in the process determine the type of metal sulfate solution produced. For example, if nickel cathode plates, squares, rounds, tubes, crowns, or chippings are used, a battery grade nickel sulfate solution is obtained. Similarly, if cobalt cathode plates, squares, rounds, tubes, crowns, or chippings are used, a battery grade cobalt sulfate solution is obtained.
The acid leaching agent used in the process can be sulfuric acid, hydrochloric acid, nitric acid, oxalic acid, citric acid, or a combination of these. The liquid oxidizing agent can be hydrogen peroxide, halogens, halogen compounds such as chlorates and perchlorates, citric acid, or oxalic acid.
The leaching solution can also comprise a mixture of sulfuric acid and citric acid. The pH of the solution is maintained in the range of 1-6, preferably pH 1-4. The oxidizing agent used in the process is hydrogen peroxide in liquid form.
The temperature during the process is maintained between 50°C and the boiling point of the leaching solution, preferably between 75°C and the boiling point. This ensures optimal conditions for the leaching process.
The process includes a step of separating metal fines from the recirculating leaching solution. Additionally, a step of removing copper is included, where metallic copper is deposited on the metal fines and the fines are removed from circulation.
The patent also describes an arrangement for performing the process. The arrangement includes at least one reactor vessel with a recirculation loop, a pump, a solid/liquid separator, inlets for the addition of acid, liquid oxidizing agent, and electrolytically produced metal objects, and an outlet for removal of the metal sulfate solution. This arrangement allows for the continuous addition of metal objects and removal of battery grade metal sulfate solution without interrupting the process.
The reactor vessel in the arrangement is a substantially vertical column adapted for adding metal objects at one end and introducing recirculating leaching solution in a counter-current mode. The reactor vessel is made from a fiber reinforced polymer material, providing durability and resistance to corrosion.
In summary, the patent describes a process and arrangement for preparing battery grade metal sulfate solutions through the leaching of electrolytically produced metal objects. The process involves specific conditions of temperature, pH, and the use of acid leaching agents and oxidizing agents. The resulting metal sulfate solutions can be used in battery manufacturing.
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