A New Approach to Lithium-Ion Battery Recycling: Eliminating Waste Through Electrochemical Salt Splitting

As electric vehicles and renewable energy storage systems become increasingly widespread, demand for lithium-ion batteries has surged. Global battery production has expanded dramatically over the past decade, creating an urgent need for efficient recycling technologies capable of recovering critical materials such as lithium, cobalt, nickel, and manganese. While battery recycling is often presented as a key component of a sustainable energy future, existing recycling methods face significant economic and environmental challenges. “Recycling spent batteries, particularly the critical mineral-containing cathodes, is necessary both to avoid toxic waste buildup and prevent gross inefficiencies when sourcing the materials for new batteries” (Misleh et. al).

A recent study from researchers Jason Misleh, Gage Wright, and Benjamin Charnay in the Kanan group at Stanford University introduces a promising alternative. Their process uses an electrochemical diaphragm flow cell to recycle lithium-ion batteries while dramatically reducing chemical waste and energy consumption. The work demonstrates how innovative process engineering can address one of the less visible sustainability challenges: making recycling itself more sustainable.

The Problem with Conventional Battery Recycling

Most lithium-ion batteries are currently recycled through hydrometallurgical processes. In these systems, strong acids dissolve valuable metals from battery cathodes, and strong bases are later used to separate and recover them by precipitating the transition metals and lithium, respectively.

While effective, this approach has a major drawback. The acids and bases are consumed during recycling and ultimately converted into large quantities of salt waste. “Traditional hydrometallurgical LIB recycling processes use super-stoichiometric quantities of acid and base and generate large volumes of salt waste that pose an environmental burden” (Misleh et. al). Argonne National Lab’s EverBatt modeling estimates that a typical hydrometallurgy recycling process would produce as much as 800 kg of sodium sulfate for every 1000 kg of battery materials recycled (Aqua Metals, 2023).

This creates several problems. Companies must continuously purchase fresh chemical reagents, increasing operating costs. Large volumes of waste salts require disposal or further treatment, creating additional environmental impacts. Furthermore, contamination from sodium-based chemicals can complicate lithium recovery, reducing process efficiency.

Researchers have long proposed regenerating these chemicals electrochemically rather than continually consuming new reagents. “Electrochemical regeneration of acid and base from salt offers a zero-waste alternative but faces challenges with respect to throughput and energy consumption, with current densities typically limited to ≤ 100 mA/cm2 and energy demands > 0.10 kWh/mol” (Misleh et al., n.d.). Existing electrochemical approaches typically rely on expensive ion-exchange membranes that limit throughput, increase energy consumption, and can degrade when exposed to impurities commonly found in recycling streams (Misleh et. al).

The Innovation: A IEM-Free Electrochemical System

Researchers in the Kanan group developed a diaphragm flow cell that avoids the use of traditional ion-exchange membranes altogether and subsequently avoids the inherent resistivity of IEMS in compared electrochemical systems. The nonselective diaphragm flow cell relies on a high concentration of supporting electrolyte to outcompete the transport of acid and base, which allows for concentrated acid and base streams and prevents acid-base recombination.

Instead of relying on selective membranes to separate ions, the system uses a concentrated lithium sulfate electrolyte and a porous diaphragm. This design allows the cell to generate acidic and basic streams directly from lithium sulfate while maintaining high efficiency.

The process operates in four primary stages:

1. Lithium sulfate is electrochemically split into an acidic stream, LiHSO4 acid, and a basic stream, LiOH base.

2. The acid dissolves valuable metals from spent battery cathodes.

3. Lithium is recovered as lithium carbonate.

4. Nickel, manganese, and cobalt are recovered as metal hydroxides through precipitation.

At the end of the process, lithium sulfate is regenerated and returned to the electrochemical cell, creating a closed-loop system with zero waste generation.

This represents a significant departure from conventional hydrometallurgical recycling, which continually consumes fresh chemicals and produces waste salts as byproducts.

Performance and Results

“In summary, we have developed a low-energy electrochemical method to recycle NMC and LCO cathode materials while generating zero waste” (Misleh et. al).

The researchers tested their system on two widely used battery chemistries: lithium cobalt oxide (LCO) and nickel-manganese-cobalt (NMC) cathodes.

The process successfully recovered more than 90% of valuable metals while operating at industrially relevant material concentrations. Importantly, the system maintained strong performance even when recycling electrolytes were repeatedly reused, demonstrating robustness that would be essential for commercial deployment.

Perhaps the most impressive result was the energy efficiency of the electrochemical cell itself. Previous electrochemical salt-splitting systems typically operated at relatively low current densities and consumed substantial electrical energy due to membrane resistance. By eliminating ion-exchange membranes, the Stanford design achieved current densities up to 500 mA/cm² while maintaining energy demands as low as 0.033–0.097 kWh per mole of acid and base produced. These values are substantially lower than many previously reported systems (Misleh et. al).

The design also proved tolerant to impurities that would normally foul or degrade conventional membranes, reducing a major operational challenge for industrial recycling facilities.

Why This Matters

Battery recycling is often discussed in terms of recovering critical minerals, but the sustainability of the recycling process itself is equally important.

A recycling technology that requires large quantities of chemicals, generates significant waste streams, or consumes excessive energy may reduce some environmental impacts while creating others. The process pioneered in the Kanan lab addresses this issue directly by closing material loops within the recycling system.

If successfully scaled, technologies like this could help create a more circular battery economy in which critical minerals are repeatedly recovered and reused with minimal waste generation.

This is particularly important as governments around the world implement stricter battery recycling requirements. Regulations in the European Union, for example, require increasingly high recovery rates for lithium, cobalt, nickel, and copper over the coming decade. Efficient recycling technologies will be necessary to meet these targets while keeping costs manageable.

References

1. Aqua Metals. (2023, June 22). The Sodium Sulfate Dilemma: The Unforeseen Challenge of Lithium Battery Recycling. aquametals. https://aquametals.com/news/the-unforeseen-challenge-of-lithium-battery-recycling-the-sodium-sulfate-dilemma/

2. Misleh, J. W., Wright, G., Charnay, B. P., & Kanan, M. W. (n.d.). Li-ion battery recycling by energy-efficient, high-throughput Li2SO4 salt splitting in a diaphragm flow cell. Watt, 1(4). https://link.springer.com/article/10.1007/s44503-026-00003-3