Selective cobalt and nickel electrodeposition for lithium-ion battery recycling through integrated electrolyte and interface control

Multiplexed and Membraneless Redox-Mediated Electrochemical Separations Through Bipolar Electrochemistry

Redox-active electrosorbents are promising platforms for selective separations. However, these platforms face intrinsic challenges in extracting multiple species simultaneously, as their binding mechanisms are typically tailored to separate a single ion preferentially. Here, bipolar electrochemistry is leveraged to introduce a new strategy for the multiplexed use of redox-active and capacitive materials for separations. Using polyvinyl ferrocene (PVF)-, Prussian blue analog (PBA)-functionalized, and carbon-based electrodes, multicomponent separations within a modular bipolar electrode (BPE) platform are demonstrated. The multiplexed BPE system provides distinct electrochemical environments within each BPE pair, enabling parallel selective separations. With three identical PVF BPEs, arsenic uptake increased linearly from 41.4 to 115.4 mgAs gPVF -1, highlighting the scalability of the system. Moreover, deploying three distinct BPE pairs-PBA, PVF, and carbon-enables simultaneous potassium recovery (11.0 mg g-1), arsenic removal (19.8 mg g-1), and desalination (4.2 mg g-1) from secondary wastewater, demonstrating real-world applicability. This wireless, membraneless architecture enables process-intensified selective separations by precisely controlling local electric fields on individual redox-active materials, facilitating electrosorption and regeneration across diverse BPE systems within a unified process.

One-step green hydrometallurgical recycling of spent lithium-ion batteries' cathode

The transition towards a low-carbon future hinges on the advancement of Lithium-ion battery (LIBs) technology, which has spurred a significant demand for raw materials and the management of waste batteries containing hazardous substances. Developing efficient and environmentally friendly recycling strategies is essential to tackle these challenges. Here, we introduce a one-step green hydrometallurgical recycling of spent lithium-ion batteries' cathode on the basis of contact-electro-catalytic (CEC) process. It combines the separation of the cathode materials in pretreatment, and leaching in a single step. Specifically, electrode pieces are directly dealt with the CEC treatment, which can remove organic binders (e.g. Polyvinylidene Fluoride) and reduce high-valence metal ions. Results indicate that the leaching efficiency of lithium, nickel, cobalt, and manganese can reach 99.6 %, 98.3 %, 99.4 %,97.4 %. Plus, SiO2 is a cost-effective and readily available catalyst requiring no modification. Therefore, the CEC-assisted one-step hydrometallurgical recycling exhibits sustainability, rapidness, high efficiency, and eco-friendly for LIBs recycling.

Emerging Trends and Future Opportunities for Battery Recycling

The global lithium-ion battery recycling capacity needs to increase by a factor of 50 in the next decade to meet the projected adoption of electric vehicles. During this expansion of recycling capacity, it is unclear which technologies are most appropriate to reduce costs and environmental impacts. Here, we describe the current and future recycling capacity situation and summarize methods for quantifying costs and environmental impacts of battery recycling methods with a focus on cathode active materials. Second use, electrification of pyrometallurgy and hydrometallurgy, direct recycling, and electrochemical recycling methods are discussed as leading-edge methods for overcoming state of the art battery recycling challenges. The paper ends with a discussion of future issues and considerations regarding solid-state batteries and co-optimization of battery design for recycling.

Tactfully introducing amphoteric group into electroactive membrane motivates highly efficient H2O splitting for reversible removal and recovery of nickel(II)

Membrane-based electro-deposition (MED) is an original process promising for reversible removal and recovery of toxic heavy metal ions from wastewater. The removal efficiency of heavy metal ions, however, was limited by the poor membrane surface H2O splitting in the conventional ion exchange membrane (IEM). Inspired by the amphoteric interface-triggered ion exchange resin regeneration phenomenon in electro-deionization, herein we subtly introduced the amphoteric group into IEM as a proof of concept to solve the above bottleneck. By virtue of the "electronic porter" role of the amphoteric -3OS-R-N(CH3)3+, the electron extraction from adsorbed H2O could be accelerated, extending the H2O splitting from the conventional membrane surface to the bulk membrane interior. Such an H2O splitting extension favorably produced an intensified and well-modeled OH- production region at the anodic side of IEM, enhancing the Ni2+ basic deposition accordingly. This special characteristic allowed our MED to realize a super-eminent metal ion removal rate (10.5 mol·h-1·m-2) along with an ultra-low specific energy consumption (0.1 kWh·mol-1) for Ni2+ removal, which considerably surpassed those of state-of-the-art heavy metal ion removal processes reported yet. Further, the deposited Ni2+ could be in situ recovered in conjunction with the facile polarity reversal method. The amphoteric electroactive membrane with high H2O splitting activity is expected to pave the path to engineering MED for efficient heavy metal ion removal and recovery.

Investigation of oxidation-reduction processes of nickel hydroxide precipitation and their carbothermical reduction

Most of the known methods for the chemical production of nickel nano- and microparticles, nickel oxides and hydroxides use various reducing agents and solvents, which are often toxic to the environment. As a rule, these methods are energy-consuming, lengthy and multi-stage, requiring complex equipment. Therefore, the development of a simple and "green" process for the synthesis of nickel-containing particles, including those with magnetic properties, remains one of the priority tasks. In this paper, a new physicochemical method for oxidation-reduction contact deposition of nickel(II) hydroxide nano-microparticles on the surface of magnesium particles from aqueous solutions of nickel-containing electrolyte is proposed. This method is based on the local corrosion of microgalvanic cells' formation with predominant hydrogen depolarization. The proposed method was used to obtain nickel(II) hydroxide samples and study their morphology using SEM, as well as their phase composition using XRD analysis. It has been proven that the shape and structure of the resulting Ni(OH)2 particles depend on the contact deposition conditions: depending on the surface state of the magnesium particles as a reducing agent, it is possible to obtain both plate-shaped α/β-Ni(OH)2 particles and three-dimensional β-Ni(OH)2 "flowers" with different degrees of crystallinity.

Progress and challenges in the use of electrochemical oxidation and reduction processes for heavy metals removal and recovery from wastewaters

Heavy metals-laden industrial wastewater represents both a threat to ecosystems and human health and, in some instances, a potential source of valuable metals however the presence of organic ligands that bind the metals in heavy metal complexes (HMCs) renders metal removal (and, where appropriate, recovery) difficult. Electrochemical-based oxidation and reduction processes represent a potentially promising means of degrading the organic ligands and reducing their ability to retain the metals in solution. In this state-of-the-art review, we provide a comprehensive overview of the current status on use of electrochemical redox technologies for organic ligand degradation and subsequent heavy metal removal and recovery from industrial wastewaters. The principles and degradation mechanism of common organic ligands by various types of electrochemical redox technologies are discussed in this review and consideration given to recent progress in electrode materials synthesis, cell architecture, and operation of electrochemical redox systems. Furthermore, we highlight the current challenges in application of electrochemical redox technologies for treatment of HMC-containing wastewaters including (i) limited understanding of the chemical composition of industrial wastewaters, (ii) constrained mass transfer process affecting the direct/indirect electron transfer, (iii) absence of approaches to convert recovered metal into high-value-added products, and (iv) restricted semi-or full-industrial-scale application of these technologies. Potential strategies for improvement are accordingly provided to guide efforts in addressing these challenges in future research.

Reductive Dissolution of NCM Cathode through Anaerobic Respiration by Shewanella putrefaciens

The consumption of lithium-ion batteries (LIBs) has considerably increased over the past decade, leading to a rapid increase in the number of spent LIBs. Exposing spent LIBs to the environment can cause serious environmental harm; however, there is a lack of experimentally obtained information regarding the environmental impacts of abandoned cathode materials. Here, we report the interactions between Shewanella putrefaciens, a microorganism commonly found in diverse low-oxygen natural settings, and LiNi0.6Co0.2Mn0.2O2 (NCM622) under anaerobic conditions. We present compelling evidence that the anaerobic respiration of Shewanella putrefaciens triggers ∼59 and ∼78% dissolution of 0.2 g/L pristine and spent NCM622, respectively. We observed that Shewanella putrefaciens interacted with the pristine and the spent NCM622 under anaerobic conditions at a neutral pH and room temperature and induced the reduction of Ni, Co, and Mn, resulting in the subsequent dissolution of Li, Ni, Co, and Mn. Moreover, we found that secondary mineralization occurred on the surface of reacted NCM622. These findings not only shed light on the substantial impact of microbial respiration on the fate of discarded cathode materials in anaerobic environments but also reveal the potential for sustainable bioleaching of cathodes in spent LIBs.

Redox-Responsive Halogen Bonding as a Highly Selective Interaction for Electrochemical Separations

Leveraging specific noncovalent interactions can broaden the mechanims for selective electrochemical separations beyond solely electrostatic interactions. Here, we explore redox-responsive halogen bonding (XB) for selective electrosorption in nonaqueous media, by taking advantage of directional interactions of XB alongisde a cooperative and synergistic ferrocene redox-center. We designed and evaluated a new redox-active XB donor polymer, poly(5-iodo-4-ferrocenyl-1-(4-vinylbenzyl)-1H-1,2,3-triazole) (P(FcTS-I)), for the electrochemically switchable binding and release of target organic and inorganic ions at a heterogeneous interface. Under applied potential, the oxidized ferrocene amplifies the halogen binding site, leading to significantly enhanced uptake and selectivity towards key inorganic and organic species, including chloride, bisulfate, and benzenesulfonate, compared to the open-circuit potential or the hydrogen bonding donor analog. Density functional theory calculations, as well as spectroscopic analysis, offer mechanistic insight into the degree of amplification of σ-holes at a molecular level, with selectivity modulated by charge transfer and dispersion interactions. Our work highlights the potential of XB in selective electrosorption by uniquely leveraging noncovalent interactions for redox-mediated electrochemical separations.

Emerging Processes for Sustainable Li-Ion Battery Cathode Recycling

The colossal growth in the use of Li-ion batteries (LiBs) has raised serious concerns over the supply chain of strategic minerals, e.g., Co, Ni, and Li, that make up the cathode active materials (CAM). Recycling spent LiBs is an important step toward sustainability that can establish a circular economy by effectively tackling large amounts of e-waste while ensuring an unhindered supply of critical minerals. Among the various methods of LiB recycling available, pyro- and hydrometallurgy have been utilized in the industry owing to their ease of operation and high efficiency, although they are associated with significant environmental concerns. Direct recycling, a more recent concept that aims to relithiate spent LiBs without disrupting the lattice structure of the CAMs, has been realized only in the laboratory scale so far and further optimization is required before it can be extended to the bulk scale. Additionally, significant progress has been made in the areas of hydrometallurgy in terms of using ecofriendly green lixiviants and alternate sources of energy, e.g., microwave and electrochemical, that makes the recycling processes more efficient and sustainable. In this review, the latest developments in LiB recycling are discussed that have focused on environmental and economic viability, as well as process intensification. These include deep eutectic solvent based recycling, electrochemical and microwave-assisted recycling, and various types of direct recycling.

Contact-electro-catalysis (CEC)

Contact-electro-catalysis (CEC) is an emerging field that utilizes electron transfer occurring at the liquid-solid and even liquid-liquid interfaces because of the contact-electrification effect to stimulate redox reactions. The energy source of CEC is external mechanical stimuli, and solids to be used are generally organic as well as in-organic materials even though they are chemically inert. CEC has rapidly garnered extensive attention and demonstrated its potential for both mechanistic research and practical applications of mechanocatalysis. This review aims to elucidate the fundamental principle, prominent features, and applications of CEC by compiling and analyzing the recent developments. In detail, the theoretical foundation for CEC, the methods for improving CEC, and the unique advantages of CEC have been discussed. Furthermore, we outline a roadmap for future research and development of CEC. We hope that this review will stimulate extensive studies in the chemistry community for investigating the CEC, a catalytic process in nature.

Rational Electrochemical Design of Cuprous Oxide Hierarchical Microarchitectures and Their Derivatives for SERS Sensing Applications

Rational morphology control of inorganic microarchitectures is important in diverse fields, requiring precise regulation of nucleation and growth processes. While wet chemical methods have achieved success regarding the shape-controlled synthesis of micro/nanostructures, accurately controlling the growth behavior in real time remains challenging. Comparatively, the electrodeposition technique can immediately control the growth behavior by tuning the overpotential, whereas it is rarely used to design complex microarchitectures. Here, the electrochemical design of complex Cu2O microarchitectures step-by-step by precisely controlling the growth behavior is demonstrated. The growth modes can be switched between the thermodynamic and kinetic modes by varying the overpotential. Cl- ions preferably adhered to {100} facets to modulate growth rates of these facets is proved. The discovered growth modes to prepare Cu2O microarchitectures composed of multiple building units inaccessible with existing methods are employed. Polyvinyl alcohol (PVA) additives can guarantee all pre-electrodeposits simultaneously evolve into uniform microarchitectures, instead of forming undesired microstructures on bare electrode surfaces in following electrodeposition processes is discovered. The designed Cu2O microarchitectures can be converted into noble metal microstructures with shapes unchanged, which can be used as surface-enhanced Raman scattering substrates. An electrochemical avenue toward rational design of complex inorganic microarchitectures is opened up.

Research on the facile regeneration of degraded cathode materials from spent LiNi0.5Co0.2Mn0.3O2 lithium-ion batteries

Rational reusing the waste materials in spent batteries play a key role in the sustainable development for the future lithium-ion batteries. In this work, we propose an effective and facile solid-state-calcination strategy for the recycling and regeneration of the cathode materials in spent LiNi0.5Co0.2Mn0.3O2 (NCM523) ternary lithium-ion batteries. By systemic physicochemical characterizations, the stoichiometry, phase purity and elemental composition of the regenerated material were deeply investigated. The electrochemical tests confirm that the material characteristics and performances got recovered after the regeneration process. The optimal material was proved to exhibit the excellent capacity with a discharge capacity of 147.9 mAh g-1 at 1 C and an outstanding capacity retention of 86% after 500 cycles at 1 C, which were comparable to those of commercial NCM materials.

Sequential separation of critical metals from lithium-ion batteries based on deep eutectic solvent and electrodeposition

The rise and development of electric vehicles have brought much attention to the recycling of lithium-ion batteries (LIBs). However, the recovery of critical metals from LiNixCoyMn1-x-yO2 (NCM) is a challenge, especially for the nickel and cobalt, which have similar chemical properties. Here, a novel ternary deep eutectic solvent (DES) composed of choline chloride, ethylene glycol, and tartaric acid was proposed. Our protocol of DES synthesis, nickel separation, and leaching of cobalt and manganese were integrated into one step, which significantly simplified the recovery process. The crystallization occurring during DES leaching was subjected to detailed investigation. The lithium, nickel, and cobalt were sequentially separated as Li2CO3, NiO, and Co(OH)2 by anterior formic acid leaching and posterior electrodeposition. After electrodeposition, DES was reused. This work provides new ideas for the sequential separation of critical metals from NCM and has great application prospects.

Potential environmental and human health menace of spent graphite in lithium-ion batteries

The growing demand for lithium-ion batteries for portable electronics and electric vehicles results in a booming lithium battery market, leading to a concomitant increase in spent graphite. This research investigated the potential impacts of spent graphite on environmental and human health using standardized toxicity extraction and Life Cycle Impact Assessment models. The spent graphite samples were classified as hazardous waste due to the average nickel content of 337.14 mg/L according to Chinese regulations. Besides, cadmium and fluorine were the other elements that exceeded the regulations threshold. Easily ignored aluminum and heavy metal cobalt are other harmful elements according to the results of Life Cycle Impact Assessments. All the metallic harmful elements mainly exist in a transferable state. Thermogravimetry infrared spectrometry coupled with mass spectrometry was employed to recognize the emitted gases and explore gas emission behavior. Inorganic gases of CO, H2S, SO2, SO3, oxynitride, HCl, and fluoride-containing gases were detected. Sulfur-containing gases released from spent graphite were contributed by the residual sulfuric acid after leaching. The correlation between the evolution of emitted gases and the heating schedule was established simultaneously. The research comprehensively illustrates the pollution of spent graphite and provides assistance for the design of green recycling schemes for spent graphite.

Electrochemical treatment of wastewaters containing metal-organic complexes: A one-step approach for efficient metal complex decomposition and selective metal recovery

Metal-organic complexes, especially those of ethylenediaminetetraacetic acid (EDTA) with metals such as copper (Cu) and nickel (Ni) (denoted here as Cu-EDTA and Ni-EDTA), are common contaminants in wastewaters from chemical and plating industries. In this study, a multi-electrode (ME) system using a two-chamber reactor and two pairs of electrodes is proposed for simultaneous electrochemical oxidation of a wastewater containing both Cu-EDTA and Ni-EDTA complexes as well as separation and selective recovery of Cu and Ni onto two different cathodes via electrodeposition. Our results demonstrate that the ME system successfully achieved 90% EDTA removal, 99% solid Cu recovery at the Cu recovery cathode and 56% Ni recovery (33.3% on the Ni recovery cathode and 22.6% in the solution) after a four-hour operation. The system further achieved 85.5% Ni recovery after consecutive five cycles of operation for 20 h. While Cu removal was mainly driven by the direct reduction of EDTA-complexed Cu(II) at the cathode, oxidation of EDTA within the Ni-EDTA complex at the anode was a prerequisite for Ni removal. The oxidation of metal-bound EDTA and free EDTA was driven by •OH and direct electron transfer on the PbO2 anode surface and graphite anode, respectively. We further show that ME system performs well for all pH conditions, treatment of real wastewaters as well as wastewaters containing other metals ions (Cr and Zn) along with Cu/Ni. The separation efficiency of Cu and Ni is dependent on applied electrode potential as well as nature and concentration of binding ligand present with comparatively lower separation efficiency achieved in the presence of weaker binding capacity and/or at lower ligand concentration and lower applied electrode potential. As such, some optimization of electrode potential is required depending on the nature/concentration of ligands in the wastewaters. Overall, this study provides new insights into the design and operation of EAOP technology for effective organic abatement and metal recovery from wastewaters containing mixtures of various metal-organic complexes.

Molecularly Selective Polymer Interfaces for Electrochemical Separations

The molecular design of polymer interfaces has been key for advancing electrochemical separation processes. Precise control of molecular interactions at electrochemical interfaces has enabled the removal or recovery of charged species with enhanced selectivity, capacity, and stability. In this Perspective, we provide an overview of recent developments in polymer interfaces applied to liquid-phase electrochemical separations, with a focus on their role as electrosorbents as well as membranes in electrodialysis systems. In particular, we delve into both the single-site and macromolecular design of redox polymers and their use in heterogeneous electrochemical separation platforms. We highlight the significance of incorporating both redox-active and non-redox-active moieties to tune binding toward ever more challenging separations, including structurally similar species and even isomers. Furthermore, we discuss recent advances in the development of selective ion-exchange membranes for electrodialysis and the critical need to control the physicochemical properties of the polymer. Finally, we share perspectives on the challenges and opportunities in electrochemical separations, ranging from the need for a comprehensive understanding of binding mechanisms to the continued innovation of electrochemical architectures for polymer electrodes.

Anions Regulation Engineering Enables a Highly Reversible and Dendrite-Free Nickel-Metal Anode with Ultrahigh Capacities

The development of safe and high-energy metal anodes represents a crucial research direction. Here, the achievement of highly reversible, dendrite-free transition metal anodes with ultrahigh capacities by regulating aqueous electrolytes is reported. Using nickel (Ni) as a model, theoretical and experimental evidence demonstrating the beneficial role of chloride ions in inhibiting and disrupting the nickel hydroxide passivation layer on the Ni electrode is provided. As a result, Ni anodes with an ultrahigh areal capacity of 1000 mAh cm-2 (volumetric capacity of ≈6000 mAh cm-3 ), and a Coulombic efficiency of 99.4% on a carbon substrate, surpassing the state-of-the-art metal electrodes by approximately two orders of magnitude, are realized. Furthermore, as a proof-of-concept, a series of full cells based on the Ni anode is developed. The designed Ni-MnO2 full battery exhibits a long lifespan of 2000 cycles, while the Ni-PbO2 full battery achieves a high areal capacity of 200 mAh cm-2 . The findings of this study are important for enlightening a new arena toward the advancement of dendrite-free Ni-metal anodes with ultrahigh capacities and long cycle life for various energy-storage devices.

Closed-loop recycling of spent lithium-ion batteries based on selective sulfidation: An unconventional approach

The facile recycling of spent lithium-ion batteries (LIBs) has attracted considerable attention because of its great importance to environmental protection and resource utilization. A novel process is developed for cyclic utilization of spent LiNixCoyMnzO2 (NCM) batteries. The spent NCM was converted into water-soluble Li2CO3, acid-dissolved MnO, and nickel-cobalt sulfides through selective sulfidation, based on roasting condition optimization and thermodynamic calculation. More than 98 % of lithium is extracted preferentially from calcined NCM through water leaching, and over 99 % of manganese is extracted selectively from water leaching residue with H2SO4 solution of 0.4 mol/L in the absence of additional reductant. The nickel and cobalt sulfides were concentrated into the leaching residue without metal impurities. The obtained Li2CO3, MnSO4, and nickel-cobalt sulfides can be regenerated as new NCM, showing good electrochemical performance, and its discharge capacity is 169.8 mAh/g at 0.2C. After 100 cycles at 0.2C, the discharge specific capacity can still be maintained at 143.24 mAh/g, and its capacity retention ratio is as high as 92  %. An environmental assessment and economic evaluation indicate that the process is an economical and eco-friendly approach for green recycling of spent LIBs.

Investigating the Electrochemically Driven Capture and Release of Long-Chain PFAS by Redox Metallopolymer Sorbents

The remediation of perfluoroalkyl substances (PFAS) is an urgent challenge due to their prevalence and persistence in the environment. Electrosorption is a promising approach for wastewater treatment and water purification, especially through the use of redox polymers to control the binding and release of target contaminants without additional external chemical inputs. However, the design of efficient redox electrosorbents for PFAS faces the significant challenge of balancing a high adsorption capacity while maintaining significant electrochemical regeneration. To overcome this challenge, we investigate redox-active metallopolymers as a versatile synthetic platform to enhance both electrochemical reversibility and electrosorption uptake capacity for PFAS removal. We selected and synthesized a series of metallopolymers bearing ferrocene and cobaltocenium units spanning a range of redox potentials to evaluate their performance for the capture and release of perfluorooctanoic acid (PFOA). Our results demonstrate that PFOA uptake and regeneration efficiency increased with more negative formal potential of the redox polymers, indicating possible structural correlations with the electron density of the metallocenes. Poly(2-(methacryloyloxy)ethyl cobaltoceniumcarboxylate hexafluorophosphate) (PMAECoPF₆) showed the highest affinity toward PFOA, with an uptake capacity of more than 90 mg PFOA/g adsorbent at 0.0 V vs Ag/AgCl and a regeneration efficiency of more than 85% at -0.4 V vs Ag/AgCl. Kinetics of PFOA release showed that electrochemical bias greatly enhanced the regeneration efficiency when compared to open-circuit desorption. In addition, electrosorption of PFAS from different wastewater matrices and a range of salt concentrations demonstrated the capability of PFAS remediation in complex water sources, even at ppb levels of contaminants. Our work showcases the synthetic tunability of redox metallopolymers for enhanced electrosorption capacity and regeneration of PFAS.

Mechanochemical upcycling of spent LiCoO2 to new LiNi0.80Co0.15Al0.05O2 battery: An atom economy strategy

The use of strong acids and low atom efficiency in conventional hydrometallurgical recycling of spent lithium-ion batteries (LIBs) results in significant secondary wastes and CO2 emissions. Herein, we utilize the waste metal current collectors in spent LIBs to promote atom economy and reduce chemicals consumption in a conversion process of spent Li1-xCoO2 (LCO) → new LiNi0.80Co0.15Al0.05O2 (NCA) cathode. Mechanochemical activation is employed to achieve moderate valence reduction of transition metal oxides (Co3+→Co2+,3+) and efficient oxidation of current collector fragments (Al0→Al3+, Cu0→Cu1+,2+), and then due to stored internal energy from ball-milling, the leaching rates of Li, Co, Al, and Cu in the ≤4 mm crushed products uniformly approach 100% with just weak acetic acid. Instead of corrosive precipitation reagents, larger Al fragments (≥4 mm) are used to control the oxidation/reduction potential (ORP) in the aqueous leachate and induce the targeted removal of impurity ions (Cu, Fe). After the upcycling of NCA precursor solution to NCA cathode powders, we demonstrate excellent electrochemical performance of the regenerated NCA cathode and improved environmental impact. Through life cycle assessments, the profit margin of this green upcycling path reaches about 18%, while reducing greenhouse gas emissions by 45%.

Selective recovery of lithium and ammonium from spent lithium-ion batteries using intercalation electrodes

Recycling lithium-ion batteries has recently become a major concern. Ammonia leaching is commonly employed in such battery recycling methods since it has various advantages such as low toxicity and excellent selectivity toward precious metals. In this study, an electrochemical system with intercalation-type electrodes was used to investigate the selective recovery of lithium and ammonium from ammonia battery leachate. Using an activated carbon electrode as a counter electrode, the selectivity of lithium from the lithium manganese oxide (LMO) electrode and the selectivity of ammonium from the nickel hexacyanoferrate (NiHCF) electrode were examined within the system. The LMO//NiHCF system was next evaluated for lithium and ammonium recovery using a synthetic solution as well as real ammonia battery leachate. When compared to previous ammonium recovery methods, the results revealed good selectivity of lithium and ammonium from each LMO and NiHCF electrode with relatively low energy consumption for ammonium recovery (2.43 Wh g-N^-1). The average recovery capacity of lithium was 1.39 mmol g^-1 with a purity of up to 96.8% and the recovery capacity of ammonium was 1.09 mmol g^-1 with 97.8% purity from the pre-treated leachate. This electrochemical method together with ammonia leaching can be a promising method for selective resource recovery from spent lithium-ion batteries.

Application of Hydrophobic Deep Eutectic Solvents in Extraction of Metals from Real Solutions Obtained by Leaching Cathodes from End-of-Life Li-Ion Batteries

This paper presents the results of applying hydrophobic deep eutectic solvents (HDESs) for the extraction of metal ions from a real hydrochloric acid solution after leaching the cathodes of three different types of Li-ion batteries. Aliquat 336-, D2EHPA- and menthol-based HDESs developed by us were used in this study. The optimal HCl leaching conditions chosen are 80 °C, 2 M HCl, 6 h, solid:liquid ratio = 1:25. The results of stepwise separation of the major elements using extraction with HDESs are presented. The HDESs used in the cross-current extraction made it possible to extract all elements with extraction ratios above 98%. It was shown that the suggested method could potentially be used in the process of recycling end-of-life Li-ion batteries.

A green and sustainable strategy toward lithium resources recycling from spent batteries

Recycling lithium from spent batteries is challenging because of problems with poor purity and contamination. Here, we propose a green and sustainable lithium recovery strategy for spent batteries containing LiFePO₄, LiCoO₂, and LiNi_0.5Co_0.2Mn_0.3O₂ electrodes. Our proposed configuration of "lithium-rich electrode || LLZTO@LiTFSI+P3HT || LiOH" system achieves double-side and roll-to-roll recycling of lithium-containing electrode without destroying its integrity. The LiTFSI+P3HT-modified LLZTO membrane also solves the H⁺/Li⁺ exchange problem and realizes a waterproof protection of bare LLZTO in the aqueous working environment. On the basis of these advantages, our system shows high Li selectivity (97%) and excellent Faradaic efficiency (≥97%), achieving high-purity (99%) LiOH along with the production of H₂. The Li extraction processes for spent LiFePO₄, LiNi_0.5Co_0.2Mn_0.3O₂, and LiCoO₂ batteries is shown to be economically feasible. Therefore, this study provides a previously unexplored technology with low energy consumption as well as high economic and environmental benefits to realize sustainable lithium recycling from spent batteries.

Electrochemical Methods for Water Purification, Ion Separations, and Energy Conversion

Agricultural development, extensive industrialization, and rapid growth of the global population have inadvertently been accompanied by environmental pollution. Water pollution is exacerbated by the decreasing ability of traditional treatment methods to comply with tightening environmental standards. This review provides a comprehensive description of the principles and applications of electrochemical methods for water purification, ion separations, and energy conversion. Electrochemical methods have attractive features such as compact size, chemical selectivity, broad applicability, and reduced generation of secondary waste. Perhaps the greatest advantage of electrochemical methods, however, is that they remove contaminants directly from the water, while other technologies extract the water from the contaminants, which enables efficient removal of trace pollutants. The review begins with an overview of conventional electrochemical methods, which drive chemical or physical transformations via Faradaic reactions at electrodes, and proceeds to a detailed examination of the two primary mechanisms by which contaminants are separated in nondestructive electrochemical processes, namely electrokinetics and electrosorption. In these sections, special attention is given to emerging methods, such as shock electrodialysis and Faradaic electrosorption. Given the importance of generating clean, renewable energy, which may sometimes be combined with water purification, the review also discusses inverse methods of electrochemical energy conversion based on reverse electrosorption, electrowetting, and electrokinetic phenomena. The review concludes with a discussion of technology comparisons, remaining challenges, and potential innovations for the field such as process intensification and technoeconomic optimization.

Selective Extraction of Transition Metals from Spent LiNix Coy Mn1-x-y O2 Cathode via Regulation of Coordination Environment

The complexity of chemical compounds in lithium-ion batteries (LIBs) results in great difficulties in the extraction of multiple transition metals, which have similar physicochemical characteristics. Here, we propose a novel strategy for selective extraction of nickel, cobalt, and manganese from spent LiNi_x Co_y Mn_1-x-y O₂ (NCM) cathode through the regulation of coordination environment. Depending on adjusting the composition of ligand in transition metal complexes, a tandem leaching and separation system is designed and finally enables nickel, cobalt, and manganese to enrich in the form of NiO, Co₃ O₄ , and Mn₃ O₄ with high recovery yields of 99.1 %, 95.1 %, and 95.3 %, respectively. We further confirm that the combination of different transition metals with well-designed ligands is the key to good selectivity. Through our work, fine-tuning the coordination environment of metal ions is proved to have great prospects in the battery recycling industry.

Mechanistic Study of Controlled Zinc Electrodeposition Behaviors Facilitated by Nanoscale Electrolyte Additives at the Electrode Interface

Nanoparticle organic hybrid materials (NOHMs) are liquid-like materials composed of an inorganic core to which a polymeric canopy is ionically tethered. NOHMs have unique properties including negligible vapor pressure, high oxidative thermal stability, and the ability to bind to reactive species of interest due to the tunability of their polymeric canopy. This makes them promising multifunctional materials for a wide range of energy and environmental technologies, including electrolyte additives for electrochemical energy storage (e.g., flow batteries) and the electrochemical conversion of CO₂ to chemicals and fuels. Due to their unique transport behaviors in fluid systems, an understanding of the near-electrode surface behavior of NOHMs in electrolyte solutions and their effect on electrochemical reactions is still lacking. In this work, the complexation of zinc (Zn) by NOHMs with an ionically tethered polyetheramine canopy (HPE) (NOHM-I-HPE) was studied using attenuated total reflectance Fourier transform infrared and Carbon-13 nuclear magnetic resonance spectroscopy. Additionally, various electrochemical techniques were employed to discern the role of NOHM-I-HPE during zinc electrodeposition, and the results were compared to those of the electrochemical system containing untethered HPE polymers. Our findings confirmed that NOHM-I-HPE and HPE reversibly complex zinc in the aqueous electrolyte. NOHM-I-HPE and HPE were found to block some of the electrode active sites, reducing the overall current density during electrodeposition, while facilitating the formation of smooth zinc deposits, as revealed by surface imaging and diffraction techniques. Observed variations in the current density responses and the degree of passivation created by the NOHM-I-HPE and HPE adsorbed on the electrode surface revealed that their different packing behaviors at the electrode-electrolyte interface influence the zinc deposition mechanism. The presence of the nanoparticle and ordering offered by the NOHMs as well as the structured conformation of the polymeric canopy allowed the formation of void spaces and free volumes for enhanced transport behaviors. These findings provided insights into how structured electrolyte additives such as NOHMs can allow for advancements in electrolyte design for controlled deposition of metal species from energy-dense electrolytes or for other electrochemical reactions.

Separation and recovery of graphite from spent lithium–ion batteries for synthesizing micro-expanded sorbents

A new class of carbon adsorbent based on spent graphite is developed for the treatment of dye wastewater.

l-Lysine derived fabrication of Cu@Ni core–satellite nanoassemblies as efficient non-Pt catalysts for the methanol oxidation reaction

With assistance of l-lysine, Cu@Ni core–satellite nanoassemblies were fabricated, which could serve as efficient non-Pt electrocatalysts for the methanol oxidation reaction due to both the component effects and structural features.