Electrochemical lithium refining: how Enso supports LiOH production

In the first article of this series, we explored why lithium refining and lithium recycling are becoming increasingly important for batteries, electric mobility and energy storage. As lithium demand grows, the challenge is no longer limited to securing raw materials. It also involves transforming lithium-containing streams into high-quality battery materials through processes that are efficient, scalable and increasingly circular.

This second article looks more closely at the technology behind that transformation.

The electrochemical route starts from a simple principle: lithium can be present in different salt streams, and those salts can be split through electrolysis to obtain lithium hydroxide (LiOH).

In lithium processing, two salts are particularly relevant: lithium chloride (LiCl) and lithium sulphate (Li₂SO₄). Lithium chloride can be obtained from brines, including those extracted from salar deposits. Lithium sulphate, by contrast, is typically generated through the treatment of hard-rock minerals such as spodumene, or it can appear in streams associated with battery recycling.

In both cases, De Nora’s technology is designed to convert the lithium salt into lithium hydroxide monohydrate, the form used in battery applications. The configuration of the electrolyser changes depending on the salt: a two-compartment cell is used for lithium chloride, while a three-compartment cell is typically used for lithium sulphate.

This flexibility is important because Enso is not limited to one lithium feedstock. It is part of a broader salt splitting platform that can be applied to various industrial streams, aiming to convert salts into valuable chemical products and reduce waste.

When the starting material is lithium chloride, the process uses a two-compartments electrochemical cell.

Lithium chloride is fed to the anodic side of the cell. During electrolysis, chlorine gas is generated at the anode. The lithium ion migrates through a cation-exchange membrane towards the cathodic compartment, where it combines with hydroxide ions to form lithium hydroxide. At the cathode, hydrogen is also produced.

The overall reaction can be summarised as:

2LiCl + 2H₂O → 2LiOH + Cl₂ + H₂

The industrial value of the process is not only in producing LiOH, since by-products can also be valorised. Chlorine and hydrogen can be recombined to produce hydrochloric acid, which may be reused in upstream process steps.

This is one of the circularity elements of the process: instead of using expensive chemicals, generating waste streams that need to be managed or disposed of, the electrochemical route can produce streams that are potentially useful within the broader lithium processing chain.

When the starting material is lithium sulphate, the process usually requires a three-compartments cell.

In this configuration, lithium sulphate is fed into the central compartment. Through the electrochemical process, lithium hydroxide is produced at the cathode, while sulphuric acid is formed at the anode. Oxygen and hydrogen are also generated as part of the process.

The overall reaction can be summarised as:

Li₂SO₄ + 3H₂O → 2LiOH + H₂SO₄ + ½O₂ + H₂

The production of sulphuric acid is particularly relevant because this acid can be reused in upstream operations, for example, in the treatment of hard-rock lithium minerals such as spodumene. In this way, the electrochemical step can support a more integrated process, where chemicals generated in one stage are reused in another.

This makes lithium sulphate processing especially relevant not only for primary refining, but also for recycling routes, where lithium-containing streams may be recovered after the treatment of end-of-life battery materials.

Conventional lithium hydroxide production can involve several chemical steps. Depending on the feedstock, these may include precipitation, washing, conversion to lithium carbonate, further reaction to lithium hydroxide, purification and one or more crystallisation stages.

The electrochemical route aims to simplify this chain.

In the case of lithium chloride, De Nora’s internal process comparison shows that several steps of the conventional route can be replaced by a single electrolysis stage. In the conventional route, lithium chloride may first be converted into lithium carbonate, which is then crystallised, washed, converted into lithium hydroxide and further purified. With direct electrochemical conversion, purified brine can be fed to the electrolyser and converted directly into lithium hydroxide.

In the case of lithium sulphate, the same logic applies. The electrochemical route can avoid intermediate solid precipitation and washing steps, while producing lithium hydroxide and sulphuric acid in one process.

The potential benefits concern both capital expenditure (Capex), meaning the investment required to build the plant, and operating expenditure (Opex), meaning the cost of running it over time. 

First, fewer process steps can mean lower Capex, because the plant requires fewer units and less process complexity. Second, reducing the use of bulk chemical reagents can help lower Opex, depending on electricity prices, reagent costs and waste disposal costs. Third, the process can reduce or avoid some waste by-products associated with conventional routes, replacing them with chemical streams that may be recovered or reused.

The technology at the centre of De Nora’s lithium refining and recovery approach is Enso.

Enso is a two- or three-compartment electrolyser designed for salt splitting processes. In lithium applications, this means converting lithium chloride or lithium sulphate into lithium hydroxide monohydrate. More broadly, Enso can be applied to other salt streams, including sodium sulphate, sodium carbonate, ammonium sulphate, TMA salts and sodium chloride.

One of the most important features of Enso is its industrial origin. Its design builds on De Nora Japan’s extensive experience in chlor-alkali, lithium and other heavy-duty electrochemical processes. Chlor-alkali is a large-scale industrial electrochemical process, and this background is central to the reliability and robustness of the platform.

This is a significant distinction. Enso is not a laboratory device that De Nora is trying to scale up. It is derived from industrial electrochemical know-how developed for demanding operating environments. This matters because lithium refining and recycling require not only chemical performance, but also long-term reliability, maintainability, safety and operability.

As Michele Sponchiado, Business Development Manager - Energy Transition and Hydrogen Business Unit at De Nora, points out, “This is one of the strengths of the equipment. It was built for large chlor-alkali plants. It is not something developed in the laboratory and then scaled up. It was born for large, demanding industrial installations, so it is very reliable and high-performing.”

De Nora’s Enso line-up is structured to accompany customers throughout the scale-up path.

The Lab configuration is used for initial data acquisition. It allows De Nora and the customer to test brine pre-treatment requirements, operating conditions and product purity. This stage is important because lithium-containing streams may vary significantly depending on their origin, and the quality of the brine fed to the electrochemical step is a critical factor.

The Demo configuration is used for process optimisation, analysis, development and final validation. It can be installed at the customer’s site and continuously operated with the real process stream, providing more representative data on performance, energy consumption and product quality.

From there, the technology can be scaled to commercial size through Plant and Plant XL configurations. These are the industrial product sizes intended for large-scale deployment.

The choice between configurations depends on the application. For three-compartment cells, De Nora typically uses the Plant size, partly due to present limitations in the size of anion-exchange membranes available on the market. For two-compartment cells, Plant XL can be used where possible, because its larger active area can improve economic performance at scale.

Sponchiado describes the logic of this pathway as a way to reduce scale-up risk: “We can accompany the customer from laboratory tests to the industrial installation. The intermediate cell is fundamental because it can run continuously with the customer’s real brine, and the results are then used to scale up to industrial cells.”

This structured scale-up path is particularly important in lithium applications, where different feedstocks and impurity profiles can affect process performance.

As electrochemical processes scale up, energy consumption becomes a key variable. This is especially true in regions where electricity prices are high.

For this reason, De Nora can propose an additional technology option: the Oxygen Depolarized Cathode, or ODC. This technology can reduce the cell voltage and therefore, lower the specific energy consumption of the process.

At the same time, De Nora’s lithium applications are moving from development towards industrial deployment. Public and confidential projects show how the technology can be applied both to primary lithium processing and to recovery from used lithium-ion batteries.

In a conventional configuration, hydrogen is produced at the cathode. In some industrial sites, this hydrogen may not have a direct use. If it cannot be valorised, it becomes a stream that needs to be managed.

ODC offers an alternative. Instead of producing hydrogen at the cathode, the cell is designed to consume oxygen. This changes the cathodic reaction and reduces the cell voltage. Since energy consumption is directly linked to cell voltage, this can significantly reduce the specific energy required by the process.

De Nora’s internal material compares a cathode evolving hydrogen with a gas-diffusion electrode consuming oxygen. The ODC configuration reduces the energy requirement in the reference case shown, making it especially relevant where electricity cost is a major factor.

Sponchiado explains the principle in practical terms: “Instead of evolving hydrogen at the cathode, reduce oxygen. The consequence is that the cell voltage drops by around 0.7 to 0.8 volts, and therefore the specific energy consumption decreases substantially.”

De Nora’s lithium and salt splitting technology is already being applied in industrial projects.

One public example is Mangrove Lithium, a technology provider that has developed a patented electrochemical process to convert lithium sourced from both mining and used battery recycling into high-quality battery-grade lithium hydroxide. De Nora Japan supplies the stack electrolyser, which is the core of Mangrove’s electrochemical lithium refining platform. The application covers the conversion of LiCl/Li₂SO₄ into LiOH·H₂O, with a reported capacity of 1,000 tonnes per year and start-up planned in 2026.

Another public case is Tuleva, a US company active in the sustainable production of clean-energy materials. De Nora will supply a complete plant comprising two ion-exchange membrane bipolar electrolysis systems. The plant, to be built in Arkansas, is designed for an overall capacity of 11,000 tonnes per year of LiOH·H₂O, with execution planned for 2026/27 and start-up in 2028.

These projects show how Enso can support the move from process development to commercial deployment.