Valuable metals recovery by molten salts electrolysis.

As the currently available methods for recycling of valuable metals from batteries and old electronics (commonly called eWaste) are in need of improvement, this project focuses on the development of a novel valuable metals recovery method by electrolysis in molten salts. The process proposed consists of three steps: metal oxides dissolution in borate salts, liquid-liquid interface ion transfer between the borate and chloride layer, and electrodeposition from the chloride phase. Inherent borate salts stability and its affinity to metals, coupled with the chloride salts large electrochemical window enables a stable and efficient (semi)-continuous process concept to be explored. Two electrolytic cell concepts akin to an industrial set-up were designed. The first composed of three interconnected chambers each for one of the three steps of the process, or a simpler, single-vessel solution relying on the immiscibility of the molten phases. For the needs of a laboratory scale testing the smaller, one vessel solution has been assembled. The proposed recycling method is a novel solution for the recovery of valuable metals considered and evaluated in this work; Co, Cu, Ni, and Mn, present in most Li-ion and Ni-MH batteries, but also other metals suitable for electrodeposition present in the eWaste or other metal-rich waste streams. The process proposed was designed, evaluated and resulted in a successful recovery of all of the metals considered. Novel and promising experimental data on the metal oxides dissolution in molten borate salts is reported. Boron oxide salts were assessed, with the sodium borate achieving significant metals concentrations ranging from 4-20 wt%. Metals distribution between the oxide and halide layers was evaluated, and was found to be biased towards the borate layer due to its structure resulting in high metal affinity, with the metal ions concentration in the chloride layer around 1 wt% for the evaluated salts combination. This enables the sodium borate phase to work as a buffer, feeding the dissolved metal required for the electrodeposition into the chloride layer sustaining the process. Liquid-liquid interface transfer and diffusion phenomena in the melt as well as the metal electrodeposition parameters were studied using a range of (electro)-analytical methods, validating the main steps of the proposed metal recovery process. The system was evaluated in a three-electrode set-up (WE: tungsten, CE; graphite, QRE: tungsten) and the formal redox reaction potentials were reported for the following feedstock: Co2O3 [-0.733/-1.848 V], CuO [-1.297/-2.375 V], Mn2O3 [-1.552 V] and NiO [-1.734 V] versus chlorine evolution. The recovered metals were analysed and found to form high purity (~99 %) dendritic deposits (SA/V of 950 cm-1), which also supports the assumption of a diffusion controlled process. This marks the successful outcome of this proof-of-concept process, providing a feasible, alternative valuable metals recovery method design

The solubility of specific metal oxides in molten borate glass

The solubility of Co3O4, Cu2O, CuO, NiO, and Mn2O3 in molten B2O3 and Na2O–2B2O3 has been studied at a temperature of 900°C under static conditions. The concentration of the dissolved metal oxides was determined by X-EDS and XPS elemental analysis. Uniformity of metal distribution has been confirmed using X-EDS and backscatter electron image mapping. It was found that the solubility of all metal oxides increased significantly with Na2O content in the B2O3 solvent. The impact of a temperature increase of 150°C and the influence of K2O doping were evaluated and found to not cause any significant change

In-situ electronics and communications for intelligent energy storage

Lithium-ion batteries are increasingly common in high-power, safety–critical applications such as aerospace, spaceflight, automotive and grid storage. The voltage and power specifications of such applications usually require large numbers of individual cells combined in series and parallel to form a battery pack. It is then the role of the Battery Management System (BMS) to monitor these cells condition and ensure they remain within safe operating limits. To minimise cost and complexity, it is typical to monitor only a fraction of the cells in a battery pack. This creates potential safety and reliability issues and requires conservative limits imposed on the overall system to ensure safe operation. This is insufficient in high-power, safety–critical applications and thus alternative approaches to battery management are required. Here we demonstrate the development of novel miniature electronic devices for incorporation in-situ at a cell-level during manufacture. This approach enables local cell-to-cell and cell-to-BMS data communication of sensor data without the need for additional wiring infostructure within a battery module assembly. The electronics firmware and hardware integration within the cell’s electrode stack is demonstrated to function after triggering post cell formation and through cycling and electrochemical impedance analysis. This work shows that the proposed approach has a negligible impact on the cells’ performance and highlights a new technique for active monitoring of the cell’s in-situ conditions. This research will enable new methods of cells characterization and monitoring for optimum electrochemical and thermal performance while improving system safety

Metal recovery by electrodeposition from a molten salt two-phase cell system

A novel electrochemical recovery method of Co, Cu, Mn and Ni from a reactor based on two immiscible molten phases, to enable selective metal plating, sufficient feedstock dissolution and protection from re-oxidation, was designed and characterised through voltammetry and chronoamperometry. The immiscible phases in the electrolytic cell were NaCl and Na2O-2B2O3 at 1173 K, and the metal feedstock to be recovered was either metal chlorides or metal oxides of Co, Cu, Mn and Ni. Metals could be successfully recovered as plated metal deposits and the formal redox reaction potentials were reported. Metals thermodynamic behaviour differences between the cells were analysed. Analysis of the metal deposits showed that the recovered metals were of high purity (∼99%). This offers an alternative method to recycle valuable metals present in the growing e-waste stream

Thermo-electrochemical instrumentation of cylindrical Li-ion cells

The performance evaluation and optimisation of commercially available lithium-ion cells is typically based upon their full cell potential and surface temperature measurements, despite these parameters not being fully representative of the electrochemical processes taking place in the core of the cell or at each electrode. Several methods were devised to obtain the cell core temperature and electrode-specific potential profiles of cylindrical Li-ion cells. Optical fibres with Bragg Gratings were found to produce reliable core temperature data, while their small mechanical profile allowed for low-impact instrumentation method. A pure metallic lithium reference electrode insertion method was identified, avoiding interference with other elements of the cell while ensuring good contact, enabling in-situ observations of the per-electrode electrochemical responses. Our thermo-electrochemical instrumentation technique has enabled us to collect unprecedented cell data, and has subsequently been used in advanced studies exploring the real-world performance limits of commercial cells

Wireless Communication Test on 868 MHz and 2.4 GHz from inside the 18650 Li-Ion Enclosed Metal Shell

As the RF communication on 18650 Li-ion cell level has not been reported due to its challenges and constrains, in this work, a valid wireless data link is demonstrated in an enclosed empty metal shell at 868 MHz and 2.4 GHz based on the IEEE 802.15.4 standard. The experimental tests are carried out using two generic unturned radiative structures, a wire loop fitted inside a cell shell, and an open terminal sub miniature version A (SMA), subsequently oriented vertically and horizontally relative to the ground plane. Based on signal strength indicator, bit error rate, and packet error rate, the test characterized a payload of 120 bytes at the highest speed of 150 kbps and 250 kbps supported by the IEEE 802.15.4 for the two communication frequencies. A MATLAB simulation is used in parallel to determine the three-dimensional radiative pattern of the two structures, whereas a three-ray model for multipath range propagation is implemented to complete the empirical experiments. It was demonstrated through testing communication of up to 10 m for both operating frequencies, proving the concept of wireless cell communication within short ranges, an essential feature for monitoring the health of each cell inside future electric vehicles (EVs)

DC Power Line Communication (PLC) on 868 MHz and 2.4 GHz Wired RF Transceivers

Efficient management through monitoring of Li-ion batteries is critical to the progress of electro-mobility and energy storage globally, since the technology can be hazardous if pushed beyond its safety boundaries. Battery management systems (BMSs) are being actively improved to reduce size, weight, and cost while increasing their capabilities. Using power line communication, wireless monitoring, or hybrid data links are one of the most advanced research directions today. In this work, we propose the use of radio frequency (RF) transceivers as a communication unit that can deliver both wired and wireless services, through their superior analog and digital signal processing capability compared to PLC technology. To validate our approach computational simulation and empirical evaluation was conducted to examine the possibility of using RF transceivers on a direct current (DC) bus for wired BMS. A key advantage of this study is that it proposes a flexible and tested system for communication across a variety of network scenarios, where wireless data links over disrupted connections may be enabled by using this technology in short-range wired modes. This investigation demonstrates that the IEEE 802.15.4-compliant transceivers with operating frequencies of 868 MHz and 2.4 GHz can establish stable data links on a DC bus via capacitive coupling at high data rates