Advances in battery-grade nickel sulfate production

Precisely engineered battery-grade precursors, defined by stringent specifications regarding metal composition, particle morphology, and purity levels, are essential for synthesizing cathode materials for rechargeable batteries with superior electrochemical performance. The purpose of this review is to examine recent advancements, challenges, and future directions in the synthesis of battery-grade nickel sulfate, a key precursor for cathode active materials. Various crystallization techniques, including evaporative, cooling, antisolvent crystallization and innovative methods like eutectic freeze crystallization, are evaluated for their efficiency in achieving the required chemical purity. The removal of magnesium, which inhibits the formation of extra pure α‑nickel sulfate hexahydrate, is identified as a critical step and discussed in detail, along with strategies for minimizing other impurities like sodium and chlorine. The review also provides an in-depth analysis of solvent extraction (SX) techniques, highlighting the importance of selecting appropriate extractants and optimizing process conditions to produce high-purity battery-grade final products without the need for subsequent crystallization or electrowinning. The novel synergistic solvent extraction systems and two-circuit processes are emphasized as efficient methods for the simultaneous extraction of nickel and cobalt, thereby simplifying the production process and reducing costs. Overall, this review identifies the critical factors and technological advancements in nickel sulfate production that contribute to improved performance and cost-efficiency in lithium-ion battery manufacturing. Future directions include the integration of novel synthesis routes that bypass conventional metal salt extraction steps, enhancing the overall sustainability and scalability of battery-grade nickel sulfate production. • Battery-grade nickel sulfate synthesis demands high purity and morphology control. • Magnesium removal is key to producing extra pure α‑nickel sulfate hexahydrate. • Crystallization techniques compared for achieving battery-grade purity standards. • Synergistic solvent extraction simplifies nickel and cobalt separation processes. • Emerging synthesis routes aim to bypass conventional metal salt extraction steps.