Recycle, Recover and Repurpose Strategy of Spent Li-ion Batteries and Catalysts: Current Status and Future Opportunities

Designing Low Toxic Deep Eutectic Solvents for the Green Recycle of Lithium-Ion Batteries Cathodes

The Lithium-ion battery (LIB) is one of the main energy storage equipment. Its cathode material contains Li, Co, and other valuable metals. Therefore, recycling spent LIBs can reduce environmental pollution and resource waste, which is significant for sustainable development. However, traditional metallurgical methods are not environmentally friendly, with high cost and environmental toxicity. Recently, the concept of green chemistry gives rise to environmental and efficient recycling technology, which promotes the transition of recycling solvents from organic solvents to green solvents represented by deep eutectic solvents (DESs). DESs are considered as ideal alternative solvents in extraction processes, attracting great attention due to their low cost, low toxicity, good biodegradability, and high extraction capacity. It is very important to develop the DESs system for LIBs recycling for sustainable development of energy and green economic development of recycling technology. In this work, the applications and research progress of DESs in LIBs recovery are reviewed, and the physicochemical properties such as viscosity, toxicity and regulatory properties are summarized and discussed. In particular, the toxicity data of DESs are collected and analyzed. Finally, the guidance and prospects for future research are put forward, aiming to explore more suitable DESs for recycling valuable metals in batteries.

Repurposing Kraft black Liquor as Reductant for Enhanced Lithium-Ion Battery Leaching

The economic advantages of H2SO4 make it the acid of choice for the hydrometallurgical treatment of waste lithium-ion batteries (LIBs). However, to facilitate the full dissolution of the higher valency metal oxides present in the cathode black mass, a suitable reducing agent is required. Herein, the application of industrial black liquor (BL) obtained from the Kraft pulping for papermaking is investigated as a renewable reducing agent for the enhanced leaching of transition metals from LIB powder with H2SO4. The addition of acidified BL to H2SO4 significantly improved the leaching efficiency for a range of LIB cathode chemistries, with the strongest effect observed for manganese-rich active material. Focusing on NMC111 (LiMnxCoyNizO2) material, a linear correlation between the BL concentration and the leaching yield of Mn was obtained, with the best overall leaching efficiencies being achieved for 2.0 mol L-1 H2SO4 and 50 vol % of BL at 353 K. A quasi-total degradation of oxygenated and aromatic groups from the BL during NMC111 dissolution was observed after leaching, suggesting that these chemical groups are essential for LIB reduction. Finally, the leached transition metals could be easily recovered by pH adjustment and oxalic acid addition, closing the resource loop and fostering resource efficiency.

Highly Stable Metal-Organic Framework with Redox-Active Naphthalene Diimide Core as Cathode Material for Aqueous Zinc-Ion Batteries

Recently, metal-organic frameworks (MOFs) as the cathode materials for aqueous zinc-ion batteries (ZIBs) received growing attention. Herein, a novel MOF, Ni-Ndi-trz (Ndi-trz=2,7-di(4H-1,2,4-triazol-4-yl)benzo[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetraone) was synthesized through a solvothermal method. Its rational design using a naphthalene diimide (Ndi) core allowed the formation of a four-fold interpenetrated pcu (primitive cubic) topology. The as-synthesized Ni-Ndi-trz is highly stable over a wide pH range (0-12) for 30 days, which is critical to ensure the decent cyclability of zinc-ion batteries (ZIBs). When used as the cathode material of ZIBs, it shows a high initial specific capacity of 90.7 mAh g^-1 and excellent cycling stability. Remarkably, three-electrode system tests, ex situ FTIR, UV/Vis and XPS spectra revealed that the Ndi core of Ni-Ndi-trz undergoes a reversible interconversion between the keto and enol forms when interacting with Zn²⁺ ions. This work may shed light on the feasibility of designing novel MOFs and exploring their mechanisms for zinc ion batteries.

A sustainable approach for selective recovery of lithium from cathode materials of spent lithium-ion batteries by induced phase transition

Recycling of spent lithium-ion batteries (LIBs) has attracted widespread attention because of their dual attributes to environmental protection and resource conservation. Utilization of strong corrosive acids is currently the preferred way to recover valuable metals from spent LIBs, but the extensive use of chemical reagents can pose serious environmental risks. Herein, this research proposes a green process for selective recovery of lithium using the material of spent LIBs itself without adding exogenous reagents, mechanochemistry induced phase transition. The leaching efficiency of Li can reach 94% by employing the copper foil separated from spent LIBs as the co-grinding additive during the mechanochemical reaction process. Then, the high value LiOH·H₂O can be prepared through direct evaporation and crystallization without adding any precipitant. Meanwhile, cobalt is almost remained in the leaching residue which can be recovered through a step-by-step separation process. XRD, XPS, and SEM-EDS characterizations show that LiCoO₂ and copper foil are transformed into the soluble Li₂O, and insoluble CuO and CoO under the mechanical force. Finally, the soluble Li₂O is dissolved in water to prepare the LiOH solution, and the insoluble CuO and CoO are transformed into Cu₂O and Co(OH)₂. On the basis of the experimental investigation, it is proven that the proposed process is suitable for selectively recovering Li from all types of cathode materials without generating salty wastewater or introducing chemical reagents. Thus, the proposed approach can ensure the efficient recovery of valuable metals from spent LIBs while avoiding the potential threat to the environment and human health.

Second-life battery systems for affordable energy access in Kenyan primary schools

As the world transitions to net zero, energy storage is becoming increasingly important for applications such as electric vehicles, mini-grids, and utility-scale grid stability. The growing demand for storage will constrain raw battery materials, reduce the availability of new batteries, and increase the rate of battery retirement. As retired batteries are difficult to recycle into components, to avoid huge amounts of battery waste, reuse and repurposing options are needed. In this research, we explore the feasibility of using second-life batteries (which have been retired from their first intended life) and solar photovoltaics to provide affordable energy access to primary schools in Kenya. Based on interviews with 12 East African schools, realistic system sizes were determined with varying solar photovoltaic sizes (5-10 kW in 2.5 kW increments) and lithium-ion battery capacities (5-20 kWh in 5 kWh increments). Each combination was simulated under four scenarios as a sensitivity analysis of battery transportation costs (i.e., whether they are sourced locally or imported). A techno-economic analysis is undertaken to compare new and second-life batteries in the resulting 48 system scenarios in terms of cost and performance. We find that second-life batteries decrease the levelized cost of electricity by 5.6-35.3% in 97.2% of scenarios compared to similar systems with new batteries, and by 41.9-64.5% compared to the cost of the same energy service provided by the utility grid. The systems with the smallest levelized cost of electricity (i.e., 0.11 USD/kWh) use either 7.5 kW or 10 kW of solar with 20 kWh of storage. Across all cases, the payback period is decreased by 8.2-42.9% using second-life batteries compared to new batteries; the system with the smallest payback period (i.e., 2.9 years) uses 5 kW solar and 5 kWh storage. These results show second-life batteries to be viable and cost-competitive compared to new batteries for school electrification in Kenya, providing the same benefits while reducing waste.

Citric acid-based deep eutectic solvent (CA-DES) as a new soil detergent for the removal of cadmium from coking sites

In order to solve the problem of soil pollution caused by excess heavy metals, cadmium (Cd), a novel soil-washing agent organic chelating acid-based deep eutectic solvent (OCA-DES), was investigated for the removal of Cd from the contaminated soil of coking plant. Four kinds of OCA-DES were prepared by mixing choline chloride (Ch-Cl) with four organic chelating acids (citric acid, oxalic acid, tartaric acid, and malic acid), respectively, to compare their washing efficiency of Cd from soil. The effects of washing operation conditions on the Cd removal efficiency were investigated. Side effects of citric acid-based deep eutectic solvent (CA-DES) on soil were analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR). The results showed that CA-DES had the best Cd removal efficiency and could reach as high as 93.75%, under ideal conditions. CA-DES mainly washed extractable and reducible Cd. The CA-DES washing process has less side effects on soil and hardly eroded the soil or changed the mineral structure of the soil. The main roles of CA-DES washing Cd include (1) hydrogen bonds capturing Cd; (2) the carboxyl group(-COOH) forming soluble chelate with Cd; and (3) releasing H⁺ ions in exchange for Cd. This study demonstrates that CA-DES, a novel soil-washing agent, has excellent removal of cadmium from soil and is environment-friendly.

Environmental behavior, human health effect, and pollution control of heavy metal(loid)s toward full life cycle processes

Heavy metal(loid)s (HMs) have caused serious environmental pollution and health risks. Although the past few years have witnessed the achievements of studies on environmental behavior of HMs, the related toxicity mechanisms, and pollution control, their relationship remains a mystery. Researchers generally focused on one topic independently without comprehensive considerations due to the knowledge gap between environmental science and human health. Indeed, the full life cycle control of HMs is crucial and should be reconsidered with the combination of the occurrence, transport, and fate of HMs in the environment. Therefore, we started by reviewing the environmental behaviors of HMs which are affected by a variety of natural factors as well as their physicochemical properties. Furthermore, the related toxicity mechanisms were discussed according to exposure route, toxicity mechanism, and adverse consequences. In addition, the current state-of-the-art of available technologies for pollution control of HMs wastewater and solid wastes were summarized. Finally, based on the research trend, we proposed that advanced in-operando characterizations will help us better understand the fundamental reaction mechanisms, and big data analysis approaches will aid in establishing the prediction model for risk management.

Porous Carbons Derived from Desiliconized Rice Husk Char and Their Applications as an Adsorbent in Multivalent Ions Recycling for Spent Battery

Recycling of spent lithium-ion batteries (LIBs) has attracted increasing attentions recently on account of continuous growth demand for corresponding critical metals/materials and environmental requirement of solid waste disposal. In this work, rice husk as one of the most abundant renewable fuel materials in the world was used to prepare rice husk char (RC) and applied to recycle multivalent ions in waste water from hydrometallurgical technology dispose of spent LIBs. Rice husk char with specific surface area and abundant pores was obtained via pickling and desilication process (DPRC). The structural characterization of the obtained rice husk char and its adsorption capacity for multivalent ions in recycled batteries were studied. XRD, TEM, SEM, Raman, and BET were used for the characterization of the raw and the modified samples. The results show rice husk chars after desilication has more flourishing pore structure and larger pore size about 50–60 nm. Meanwhile, after desilication, the particle size of rice husk char decreased to 31.392 μm, and the specific surface area is about 402.10 m2/g. Its nitrogen adsorption desorption curve (BET) conforms to the type IV adsorption isotherm with H3 hysteresis ring, indicating that the prepared rice husk char is a mesoporous material. And the adsorption capacity of optimized DPRC for Ni, Co, and Mn ions is 7.00 mg/g, 4.84 mg/g, and 2.67 mg/g, respectively. It also demonstrated a good fit in the Freundlich model for DPRC-600°C, and a possible adsorption mechanism is proposed. The study indicates biochar materials have great potential as an adsorbent to recover multivalent ions from spent batteries.

Recycling of cathode material from spent lithium-ion batteries: Challenges and future perspectives

The intrinsic advancement of lithium-ion batteries (LIBs) for application in electric vehicles (EVs), portable electronic devices, and energy-storage devices has led to an increase in the number of spent LIBs. Spent LIBs contain hazardous metals (such as Li, Co, Ni, and Mn), toxic and corrosive electrolytes, metal casting, and polymer binders that pose a serious threat to the environment and human health. Additionally, spent LIBs may serve as an economic source for transition metals, which could be applied to redesigning under a closed-circuit recycling process. Thus, the development of environmentally benign, low cost, and efficient processes for recycling of LIBs for a sustainable future has attracted worldwide attention. Therefore, herein, we introduce the concept of LIBs and review state-of-art technologies for metal recycling processes. Moreover, we emphasize on LIB pretreatment approaches, metal extraction, and pyrometallurgical, hydrometallurgical, and biometallurgical approaches. Direct recycling technologies combined with the profitable and sustainable cathode healing technology have significant potential for the recycling of LIBs without decomposition into substituent elements or precipitation; hence, these technologies can be industrially adopted for EV batteries. Finally, commercial technological developments, existing challenges, and suggestions are presented for the development of effective, environmentally friendly recycling technology for the future.

A Novel Low-Temperature Fluorination Roasting Mechanism Investigation of Regenerated Spent Anode Graphite via TG-IR Analysis and Kinetic Modeling

Spent anode graphite, a hazardous solid waste discarded from the recovery of spent lithium-ion batteries (LIBs), had created social and environmental issues but has been scarcely investigated. Thus, a feasible, environmentally friendly, and economical process of low-temperature fluorination roasting and water leaching technology was proposed to regenerate spent graphite anodes. The results showed that the physical and chemical properties of regenerated graphite with a purity of 99.98% reached the graphite anode standard of LIBs and exhibited a stable specific capacity (340.9 mAh/g), capacity retention (68.92% after 470th cycles), and high initial Coulombic efficiency (92.13%), much better than that of waste carbon residue and similar to that of commercial graphite. Then the reaction mechanism and kinetic modeling of fluorination roasting of spent anode material was mainly explored by differential thermogravimetry and nonisothermal analysis methods. The results showed that the complexation and phase-transformation process of non-carbon valuable components in spent anode graphite occurred through three consecutive reactions in the 80-211 °C temperature intervals. The reaction mechanism of the whole process can be kinetically characterized by three successive reactions: third-order chemical reaction, Z-L-T eq, and second-order chemical reaction. Moreover, the thermodynamic functions of the fluorination roasting were calculated by the activated complex theory (transition state), which indicated the process was nonspontaneous. The mechanistic information was in good agreement with thermogravimetric-infrared spectroscopy (TG-IR), electron probe microanalysis, scanning electron microscopy, energy-dispersive spectrometry, and simulation experiments results.

Towards Recycling of LLZO Solid Electrolyte Exemplarily Performed on LFP/LLZO/LTO Cells

All-solid-state lithium ion batteries (ASS-LIBs) are promising due to their safety and higher energy density as compared to that of conventional LIBs. Over the next few decades, tremendous amounts of spent ASS-LIBs will reach the end of their cycle life and would require recycling in order to address the waste management issue along with reduced exploitation of rare elements. So far, only very limited studies have been conducted on recycling of ASS-LIBS. Herein, we investigate the recycling of the Li7 La3 Zr2 O12 (LLZO) solid-state electrolyte in a LiFePO4 /LLZO/Li4 Ti5 O12 system using a hydrometallurgical approach. Our results show that different concentration of the leaching solutions can significantly influence the final product of the recycling process. However, it was possible to recover relatively pure La2 O3 and ZrO2 to re-synthesize the cubic LLZO phase, whose high purity was confirmed by XRD measurements.

Literature Review, Recycling of Lithium-Ion Batteries from Electric Vehicles, Part I: Recycling Technology

During recent years, emissions reduction has been tightened worldwide. Therefore, there is an increasing demand for electric vehicles (EVs) that can meet emission requirements. The growing number of new EVs increases the consumption of raw materials during production. Simultaneously, the number of used EVs and subsequently retired lithium-ion batteries (LIBs) that need to be disposed of is also increasing. According to the current approaches, the recycling process technology appears to be one of the most promising solutions for the End-of-Life (EOL) LIBs—recycling and reusing of waste materials would reduce raw materials production and environmental burden. According to this performed literature review, 263 publications about “Recycling of Lithium-ion Batteries from Electric Vehicles” were classified into five sections: Recycling Processes, Battery Composition, Environmental Impact, Economic Evaluation, and Recycling & Rest. The whole work reviews the current-state of publications dedicated to recycling LIBs from EVs in the techno-environmental-economic summary. This paper covers the first part of the review work; it is devoted to the recycling technology processes and points out the main study fields in recycling that were found during this work.

Cobalt Recovery from Li-Ion Battery Recycling: A Critical Review

The increasing demand for Li-ion batteries for electric vehicles sheds light upon the Co supply chain. The metal is crucial to the cathode of these batteries, and the leading global producer is the D.R. Congo (70%). For this reason, it is considered critical/strategic due to the risk of interruption of supply in the short and medium term. Due to the increasing consumption for the transportation market, the batteries might be considered a secondary source of Co. The outstanding amount of spent batteries makes them to a core of urban mining warranting special attention. Greener technologies for Co recovery are necessary to achieve sustainable development. As a result of these sourcing challenges, this study is devoted to reviewing the techniques for Co recovery, such as acid leaching (inorganic and organic), separation (solvent extraction, ion exchange resins, and precipitation), and emerging technologies—ionic liquids, deep eutectic solvent, supercritical fluids, nanotechnology, and biohydrometallurgy. A dearth of research in emerging technologies for Co recovery from Li-ion batteries is discussed throughout the manuscript within a broader overview. The study is strictly connected to the Sustainability Development Goals (SDG) number 7, 8, 9, and 12.

Electric car battery: An overview on global demand, recycling and future approaches towards sustainability

Li-ion batteries are daily present in our electronic devices. These batteries are used in electric and hybrid vehicles supporting the current agreements to decrease greenhouse gas emissions. As a result, the electric vehicle demand has increased in the world. As Li-ion batteries are composed of critical metals in which there is a risk of interruption of supply in the medium term, recycling is the key to a sustainable future without internal combustion vehicles. Understanding the current scenario and future perspectives is important for strategies of new battery design, recycling routes and reverse logistics, as well as policies for sustainable development. This paper presents an overview of current and future vehicles used worldwide. An increase from 1.3 to 2 billion vehicles is expected worldwide until 2030; an outstanding demand will occur mainly in BRICS countries. The data demonstrated a correlation between the number of vehicles in use and GDP. Patents and processes designed for recycling Li-ion batteries and the new developments on pyro-, hydro-, and bio-metallurgical routes have been revised. The manuscript describes the importance and benefits of recycling as regards the supply of critical metals and future trends towards a circular economy.

Extraction of valuable metals from discarded AMOLED displays in smartphones using Bacillus foraminis as an alkali-tolerant strain

With the alarming rate of e-waste generation, resource recovery from secondary metal sources is essential for sustainable resource utilization and to prevent the release of potentially toxic elements into the environment. In the current study, the first-time extraction of Ag, Mo, and Cu from active-matrix organic light-emitting diode (AMOLED) screens of discarded smartphones have been achieved using organic acids produced by Bacillus foraminis cultured on a modified Horikoshi medium. The influences of initial pH, inoculation size, and pulp density on the bioleaching process were evaluated over six-day experiment. Maximum extraction of Ag, Mo, and Cu (100, 56.8, and 41.4%) at optimal values of three investigated factors was obtained over a 12-day bioleaching experiment. A diverse assemblage of organic acid was produced in the optimized bioleaching condition, including tartaric (12.1 mM), formic (49.8 mM), acetic (21.5 mM), lactic (78.5 mM), citric (2.7 mM), and propionic (69.6 mM) acid. The contact angle analysis highlighted more hydrophobicity of powder after the bioleaching. FTIR and CHNO data also confirmed the role of bioleaching in the powder wettability alteration. The sequential extraction method revealed high mobility of In, Fe, Co, Cu, Cr, and Mo and low mobility of Ag. The results exhibited high tolerance of alkali-tolerant bacteria to potentially toxic elements and its superior performance in the bioleaching of discarded mobile screens at high pulp density.

Reuse of LiCoO2 Electrodes Collected from Spent Li-Ion Batteries after Electrochemical Re-Lithiation of the Electrode

The recycling of used Li-ion batteries is important as the consumption of batteries is increasing every year. However, the recycling of electrode materials is tedious and energy intensive with current methods, and part of the material is lost in the process. In this study, an alternative recycling method is presented to minimize the number of steps needed in the positive electrode recovery process. The electrochemical performance of aged and re-lithiated Mg-Ti-doped LiCoO2 and stoichiometric LiCoO2 was investigated and compared. The results showed that after re-lithiation the structure of original LiCoO2 was restored, the capacity of an aged LiCoO2 reverted close to the capacity of a fresh LiCoO2 , and the material could thus be recovered. The re-lithiated Mg-Ti-doped LiCoO2 provided rate capability properties only slightly declined from the rate capability of a fresh material and showed promising cyclability in half-cells.

A green, efficient, closed-loop direct regeneration technology for reconstructing of the LiNi0.5Co0.2Mn0.3O2 cathode material from spent lithium-ion batteries

Lithium nickel manganese cobalt oxide in the spent lithium ion batteries (LIBs) contains a lot of lithium, nickel, cobalt and manganese. However, how to effectively recover these valuable metals under the premise of reducing environmental pollution is still a challenge. In this work, a green, efficient, closed-loop direct regeneration technology is proposed to reconstruct LiNi_0.5Co_0.2Mn_0.3O₂ (NCM523) cathode materials from spent LIBs. Firstly, the failure mechanism of NCM523 cathode materials in the spent LIBs is analyzed deeply. It is found that the spent NCM523 material has problems such as the dissolution of lithium and transition metals, surface interface failure and structural transformation, resulting in serious deterioration of electrochemical performance. Then NCM523 material was directly regenerated by supplementing metal ions, granulation, ion doping and heat treatment. Meanwhile, PO₄^3- polyanions were doped into the regenerated NCM material in the recovery process, showing excellent electrochemical performance with discharge capacity of 189.8 mAh g^-1 at 0.1 C. The recovery process proposed in this study puts forward a new strategy for the recovery various lithium nickel cobalt manganese oxide (e.g., LiNi_1/3Co_1/3Mn_1/3O₂, LiNi_0.5Co_0.2Mn_0.3O₂, LiNi_0.6Co_0.2Mn_0.2O₂ and LiNi_0.8Co_0.1Mn_0.1O₂) and accelerates the industrialization of spent lithium ion battery recycling.

Extremophiles, a Nifty Tool to Face Environmental Pollution: From Exploitation of Metabolism to Genome Engineering

Extremophiles are microorganisms that populate habitats considered inhospitable from an anthropocentric point of view and are able to tolerate harsh conditions such as high temperatures, extreme pHs, high concentrations of salts, toxic organic substances, and/or heavy metals. These microorganisms have been broadly studied in the last 30 years and represent precious sources of biomolecules and bioprocesses for many biotechnological applications; in this context, scientific efforts have been focused on the employment of extremophilic microbes and their metabolic pathways to develop biomonitoring and bioremediation strategies to face environmental pollution, as well as to improve biorefineries for the conversion of biomasses into various chemical compounds. This review gives an overview on the peculiar metabolic features of certain extremophilic microorganisms, with a main focus on thermophiles, which make them attractive for biotechnological applications in the field of environmental remediation; moreover, it sheds light on updated genetic systems (also those based on the CRISPR-Cas tool), which expand the potentialities of these microorganisms to be genetically manipulated for various biotechnological purposes.

Sustainable recycling of LiCoO2 cathode scrap on the basis of successive peroxymonosulfate activation and recovery of valuable metals

Increasing demand and waste of lithium-ion batteries (LIBs) has adversely affected resources and the environment. Multistage utilization of spent LIBs is essential to their sustainable development. Here, we propose a simple recycling method of LiCoO₂ cathode scrap, based on the first use of the cathode scrap as a catalyst to degrade organic pollutants via peroxymonosulfate activation, and subsequent recovery of valuable metals from the used catalyst. Compared with pristine LiCoO₂, the LiCoO₂ cathode scrap exhibits excellent catalytic performance due to the active sites generated, such as the vacancy generation and electronic structure modulation by the degradation of LiCoO₂ during the continuous lithiation and delithiation processes. The removal efficiency of cathode scrap to the o-phenylphenol exceeds 98% within 60 min, and the degradation efficiency is still above 95% after the 10th use because its unique sandwich and porous structure ensure the stability and recyclability. After multiple catalytic reactions, due to the generation of crack, the separation of the sandwich structure, and further degradation of active materials, the leaching efficiency of transition metals from the cathode scrap in deep eutectic solvent is promoted. 86% of lithium and 95% of cobalt are leached from the used catalyst respectively. This study provides a promising strategy for the sustainable development of LIBs and promotes the utilization of spent LIBs in multiaspect.