There is an increasing demand for Li-ion batteries (LiB) in portable electronic devices and energy storage in stationary applications and electric vehicles. Lithium (Li) is a high-tech metal found only in a few locations worldwide, and its extraction is costly, energy-demanding and pollutes the environment. The demand for batteries has resulted in an ever-increasing amount of used and spent LiB, containing large amounts of Li. Current Li recovery and recycling methods are complex, expensive, and environmentally damaging, so it is necessary to develop efficient alternative methods.

Biotechnology-based methods for recovering metals represent a promising approach to integrating and/or replacing current technologies. Those methods use the metabolic capabilities of microorganisms to carry out processes typically done using physicochemical approaches. One such bio-based strategy is the exploitation of the ability of some microbial species to transfer electrons to solid external electron acceptors, such as metals or electrodes, an approach known as microbial electrochemical technology. This project aims to design and optimise a bioelectrochemical system (BES) to recover high purity Li.

In BESs such as microbial fuel cells (MFCs), electrical energy is produced from the microbial degradation in the anode of organic compounds (e.g., wastewaters). Microorganisms degrade nutrients and transfer electrons to the anode; the electrons circulate to the cathode, generating an electric current. In the cathode, the electrons are used to reduce an electron acceptor (e.g., metals). When the cathode is colonised by microorganism able to transfer the electrons to Li, high purity recyclable Li can be recovered from waste streams.

In this project, we will design and analyse a microbial electrochemical system for the recovery of Li from actual LiB waste, focusing on the main aspects affecting the process, such as the microorganisms and their capabilities, the design of the system (configuration, types of electrodes, catalysts, metal concentration, etc.), and the operational conditions that produce increased yields and efficiencies of Li recovery. We will screen diverse microbial species and communities for their capability to remove Li from the waste and test them in different reactor designs (microbial fuel cell, microbial electrochemical cell, microbial desalination cell and tubular reactors). We will conduct a detailed life cycle assessment and techno-economic analysis to evaluate the environmental and economic implications of the process, which will allow us to explore the feasibility of economic scales of operation and understand the role of bio-based metal recycling in the circular economy.

The combination of experimental approaches with sustainability assessment will provide a clear understanding of the system and generate strategies for scale-up. The project will deliver an optimal biotechnology-based solution for attaining high purity and yield of Li from LiB waste. Recovered Li can be returned to LiB, which will be proven by testing its quality to complete the economic circularity of Li.

Technical Abstract:
The increased use of Li-ion batteries (LiB) has caused a high demand for Li, a high-tech metal found only in a few locations worldwide. Li production is costly, energy-demanding, and environmentally damaging: It is essential to design and optimize methods for recovery spent Li. Li recycling is complex, expensive and inefficient, recovering only a small quantity of low-grade Li. The EU Green Deal 2020 set regulations to achieve 65% recycling efficiency for LiB and 70% material recovery rate for Li by 2030.
Similar regulations are expected to be introduced in the UK to ensure the high recovery of strategic metals.

We will design and optimise a bioelectrochemical system (to recover high purity Li. Exploiting the ability of some microbial species to transfer electrons to external acceptors, we will design a microbial electrochemical system to recover Li from LiB waste, focusing on the main aspects affecting the process: microorganisms, reactor configuration, electrodes, metal concentration, substrates, etc. We will screen diverse microbial species and microbial communities for their capability to remove Li from the waste and test them in different reactor designs (MFC, MEC, MDC, tubular). This will provide a qualitative and quantitative correlation between metal removal, the composition of the microbial community, electrochemical performance and the characterisation of different designs of microbial electrochemical reactors for efficient processing of LiB.

We will conduct a detailed life cycle assessment and techno-economic analysis to analyse the environmental and economic implications of the process to reach circular economy-focused policy requirements. Combining sustainability assessment with experimentation will facilitate understanding of the system and guide scale-up strategies. The ultimate objective is the optimisation of this biotechnology-based solution for attaining high purity and yield of recyclable Li from spent LiB's black mass waste.