Key Takeaways & Executive Findings
- •• • Direct regeneration via hydrothermal synthesis using Na2SO3 as a reducing agent in Li2SO4 solution achieved a reversible specific capacity of 135.9 mAh/g at 1C, with 99% capacity retention after 100 cycles, demonstrating economic viability and cycling stability. • • Pyrometallurgical recovery typically requires temperatures above 800°C, leading to high energy consumption and hazardous gas emissions; however, NaOH/Na2CO3 activation enables decomposition of Fe-PO4 bonds at 600°C/900°C, reducing energy demand. • • Hydrometallurgical processes, the mainstream route, involve leaching, purification, and product synthesis; challenges remain in deep removal of impurities like Al, Ti, and F, which degrade product quality. • • The review highlights that current recovery often prioritizes lithium over iron and phosphorus, resulting in insufficient high-value utilization of Fe/P resources; innovative approaches such as converting delithiated LiFePO4 into NaFeS2 are proposed to address this.
Abstract
With the rapid development of China's lithium-ion power battery industry, the recycling of large-scale retired batteries has become a critical link for the sustainable development of the new energy vehicle industry. The recovery of cathode materials from spent lithium iron phosphate (LiFePO4) batteries is a current research hotspot, significant for resource recycling and environmental protection. This study systematically reviews recent progress in recycling technologies for spent LiFePO4 cathode materials, mainly including direct regeneration, pyrometallurgy, and hydrometallurgy. It focuses on analyzing the current research status of key steps in hydrometallurgy, such as leaching of valuable elements, deep removal of impurities, and product regeneration, and compares the advantages and limitations of various methods. Addressing core issues in current recovery processes, such as insufficient high-value utilization of iron and phosphorus resources and difficulty in deep impurity removal, this study proposes corresponding solutions and technical prospects, aiming to provide theoretical reference and engineering guidance for efficient, clean, and high-value recycling of spent LiFePO4 batteries.
1. Introduction
The rapid expansion of China's lithium-ion battery market, driven by the 'dual carbon' goals, has led to an unprecedented surge in battery production and subsequent retirement. By 2025, the annual retired capacity of power batteries is projected to reach 80 GWh, with cumulative retirements hitting 274 GWh. This poses significant environmental and resource challenges, as improper disposal of spent batteries can lead to heavy metal contamination and loss of valuable materials. Among various battery chemistries, LiFePO4 batteries dominate the Chinese market due to their low cost, long cycle life, and thermal stability, making their recycling a strategic priority.
Existing commercial recycling methods, primarily pyrometallurgy and hydrometallurgy, have been criticized for high energy consumption, hazardous emissions, and incomplete recovery of iron and phosphorus. Direct regeneration methods, while promising, face issues of uniformity and high energy input. The bottleneck lies in achieving efficient separation of impurities (Al, Ti, F) and simultaneous recovery of lithium, iron, and phosphorus in a cost-effective and environmentally benign manner. This review systematically evaluates recent advances in direct regeneration, pyrometallurgy, and hydrometallurgy, with a focus on hydrometallurgical innovations that address these challenges, offering insights into scalable and sustainable recycling pathways.
Loading authentic research manuscript (Pages 1–5)...
CHEN Weiju, YU Xinyi, JIANG Yang (2026). Research Progress on Recycling Technologies for Cathode Materials of Spent Lithium Iron Phosphate Batteries. Chinese Journal of Environmental Engineering. https://doi.org/10.12030/j.cjee.202507058
Research & Educational Purpose Only: The translations, structured abstracts, analytical annotations, and data reports provided by SinoGreenTechare intended exclusively for academic research, internal corporate R&D, and educational benchmarking. They do not constitute formal engineering, chemical safety, legal, or professional advice.
Copyright & Intellectual Property Notice: Original copyright of the underlying source articles and experimental data remains with the respective authors, institutions, and original publishing journals. SinoGreenTech claims intellectual property only over its proprietary translations, analytical syntheses, and AEO structured enhancements in accordance with international fair use and academic citation principles.
Frequently Asked Questions
What are the main technical bottlenecks in the hydrometallurgical recovery of spent LiFePO4 cathode materials, and how do they impact industrial scalability?
The primary bottlenecks include the incomplete leaching of valuable metals, especially iron and phosphorus, and the difficulty in deep removal of impurities such as aluminum, titanium, and fluoride. These impurities can precipitate during product synthesis, leading to low-purity products that fail to meet battery-grade specifications. For instance, aluminum and titanium impurities in the leachate can co-precipitate with iron phosphate, reducing its electrochemical performance. Industrial scalability is hindered by the need for multiple purification steps, which increase cost and complexity. The review suggests that innovative approaches like selective precipitation using Fe(III) at high temperatures can effectively remove Al and Ti, but these require careful control of pH and temperature, posing engineering challenges.
How does direct regeneration via hydrothermal synthesis compare to high-temperature solid-state repair in terms of energy consumption and product quality?
Hydrothermal synthesis operates at lower temperatures (typically 150-200°C) compared to high-temperature solid-state methods (above 600°C), significantly reducing energy consumption. It also yields more uniform particle size and composition, as demonstrated by SONG et al. and JING et al., who achieved discharge capacities of 141.9 and 147.9 mAh/g at 1C, respectively. However, hydrothermal methods require high-pressure equipment, posing safety risks and higher capital costs. In contrast, solid-state repair is simpler but suffers from non-uniformity and lithium volatilization at high temperatures. The choice depends on trade-offs between energy efficiency, product quality, and process safety.
What are the environmental and economic advantages of using molten salt-assisted pyrometallurgy compared to conventional high-temperature smelting?
Molten salt-assisted methods, such as using NaOH/Na2CO3 as activators, can lower the reaction temperature from above 800°C to 600-900°C, reducing energy consumption and minimizing the volatilization of hazardous substances like HF. For example, LI et al. and ZHANG et al. achieved decomposition of Fe-PO4 bonds at 150°C and 600°C/900°C, respectively, enabling recovery of lithium salts and iron oxides. This approach also facilitates easier separation of iron via magnetic separation. However, challenges include the recovery and recycling of the salt agents, potential equipment corrosion, and the need for process scale-up, which currently limits its industrial application.
How can the recovery of iron and phosphorus be improved to achieve high-value utilization, given that current processes often focus on lithium recovery?
Current hydrometallurgical processes often prioritize lithium recovery, leaving iron and phosphorus in the residue as low-value byproducts. To enhance their recovery, innovative methods such as converting delithiated LiFePO4 into NaFeS2 (as proposed by HE et al.) can be employed, which allows for the recovery of phosphorus in a more valuable form. Additionally, the use of selective leaching agents and precipitation techniques can separate iron and phosphorus as battery-grade iron phosphate (FePO4) or lithium iron phosphate (LiFePO4) for reuse in new batteries. For instance, WU et al. demonstrated the regeneration of battery-grade FePO4 and Li2CO3 from spent LiFePO4/C powder, achieving high purity suitable for battery applications.
What are the key impurities in spent LiFePO4 cathode materials, and what methods are effective for their removal to meet battery-grade purity standards?
Key impurities include aluminum (from current collectors), titanium (from additives), and fluoride (from electrolyte decomposition). These impurities can adversely affect the electrochemical performance of regenerated materials. Effective removal methods include high-temperature co-precipitation triggered by Fe(III) for Al and Ti removal, as reported by WU et al., achieving efficient separation. For fluoride removal, adsorption using amorphous or crystalline AlOOH has been shown to be effective. Additionally, solvent extraction and ion exchange techniques are employed for selective separation. The review emphasizes that achieving deep removal of these impurities is critical for producing high-purity products that meet battery-grade specifications, and ongoing research focuses on optimizing these purification steps.
Related Chinese Research & Cross-Citations
Analysis of National and Local Policies for Medical Waste Treatment and Disposal in China
The escalating generation of medical waste, driven by healthcare expansion and frequent medical activities, poses significant environmental and public health risks. Under the framework of ecological civilization, China is developing a comprehensive policy system for medical waste treatment and disposal, yet the current framework remains nascent and exhibits inconsistencies between national and local policies. This study systematically analyzes the status of national and local policies from 2003 to 2024, collecting 413 policy documents (166 from national ministries and 247 from provincial governments). The analysis examines temporal evolution, regional distribution, and policy focus, alongside the influence of medical waste output, treatment technologies, facility infrastructure, and major epidemic responses. Findings reveal distinct policy phases: initial self-disposal, exploratory management, foundational system building, and rapid development. Regional disparities are pronounced, with eastern coastal areas showing more advanced policies due to greater technical and financial resources. The surge in medical waste, particularly during the COVID-19 pandemic, underscores the need for enhanced regulatory guidance. Non-incineration technologies are gaining traction for their environmental and cost benefits, and facility coverage has improved but remains uneven. The study proposes five policy principles to foster technological innovation and industrial upgrading, ensuring safe medical waste management and environmental protection.
Kinetic Analysis and Simulation of Pollutant Removal in Sewage Networks
This study investigates pollutant removal characteristics and kinetic behaviors in sewage networks, and analyzes their impact on the carbon-to-nitrogen ratio (C/N, as COD/TN) of influent to wastewater treatment plants. Source water quality sampling at drainage outlets revealed spatial and temporal variations in C/N, with domestic sewage exhibiting higher C/N than industrial sewage, and diurnal peaks reaching 6.92 versus 4.71 during off-peak hours. Using a pilot-scale adjustable sewage network system in Kunshan, experiments were conducted under high (0.491 m·s−1) and low (0.089 m·s−1) flow velocities, monitoring pollutant removal over 144 hours. Pseudo-first-order kinetics were applied to model COD and TN removal. Results showed that COD (including SCOD and PCOD), BOD5, and SS achieved approximately 80% removal within 144 h, with higher removal at low flow velocity. TN, NH3-N, and TP exhibited lower overall removal rates. Kinetic fitting revealed that COD removal rate constants (kCOD) were significantly higher than those for TN (kTN), and both decreased with increasing flow velocity: at low velocity, kCOD=0.0167 h−1 and kTN=0.0029 h−1; at high velocity, kCOD=0.0127 h−1 and kTN=0.0020 h−1. Simulations based on actual source pollutant concentrations indicated that the time for C/N to drop to the denitrification critical value of 4.50 was 12.24 h at high velocity, but shortened to 9.49 h at low velocity. These findings demonstrate that increasing flow velocity effectively retards the decline of C/N. Therefore, regulating network flow velocity to reduce hydraulic retention time is a key strategy for maintaining adequate C/N at the terminal and ensuring denitrification efficiency in wastewater treatment plants.
Preparation of Trimetallic-Carbon Composite Catalysts and Their Application in Catalytic Ozonation of Industrial Wastewater
Advanced oxidation processes (AOPs) are promising for degrading organic pollutants in water treatment. Heterogeneous catalytic ozonation (HCO) has gained attention due to its high oxidation efficiency, strong interference resistance, and low secondary pollution. In this study, a series of trimetallic-carbon composite ozone catalysts were prepared via an organic precursor calcination method using γ-Al2O3 as support. This method enhanced catalytic activity and mechanical strength while overcoming the limitations of carbon materials (low mechanical strength) and metal-based materials (poor mass transfer). The optimized catalyst, CA-FeCoCu, comprising Fe, Co, Cu, carbon, and alumina, exhibited excellent performance in phenol degradation and real industrial wastewater treatment. Characterization revealed that the synergistic effect of trimetals and the introduction of multiple carbon types increased specific surface area and hydroxyl radical (·OH) generation. In a pilot-scale fixed-bed reactor, the CA-FeCoCu/O3 system reduced COD from 120 mg·L−1 to below 40 mg·L−1, with an O3 consumption ratio (O/C) of less than 1, effectively lowering operational costs. This work provides a new strategy for developing efficient and stable heterogeneous O3 catalysts and offers a reference for the practical application of HCO in industrial wastewater treatment.
Differentiated Characteristics of Suspended Particulate Matter and Their Effects on Water Quality in the Middle and East Routes of the South-to-North Water Diversion Project
This study investigates the spatiotemporal differentiation of suspended particulate matter (SPM) characteristics, sources, and their impacts on water quality between the Middle Route (closed artificial channel) and East Route (open natural water system) of the South-to-North Water Diversion Project. Thirty sampling sites (13 on the Middle Route, 17 on the East Route) were established, and samples were collected during dry and wet seasons. Water quality parameters and SPM characteristics were analyzed, including particle size distribution, total suspended solids (TSS), chlorophyll a, and stable carbon and nitrogen isotopes. Results show that the Middle Route maintains good and stable water quality, with SPM dominated by coarse particles (>63 μm, 61.43%–94.68%), total phosphorus (TP) <0.01 mg·L−1, and a significant positive correlation between chlorophyll a and coarse particles (r=0.60), indicating algal aggregation dominates particle formation. In contrast, the East Route exhibits high and fluctuating nitrogen and phosphorus concentrations, with SPM dominated by fine particles (<20 μm, 51.26%–88.61%), TP ranging from 0.03 to 1.11 mg·L−1, and a positive correlation with fine particles, suggesting significant external inputs. Carbon and nitrogen isotope analysis reveals that Middle Route SPM primarily originates from autochthonous algae (contribution >46.75%), while East Route SPM is influenced by both terrestrial C3 plants and algae. The distinct engineering and management approaches of the two routes lead to significant differences in SPM characteristics and sources, thereby affecting water quality dynamics. The Middle Route requires an 'algal reduction and hydrodynamic optimization' strategy to control algal-derived coarse particle deposition, whereas the East Route benefits from 'retention-sedimentation and wetland purification' to reduce external fine particles and pollutant inputs. This research provides theoretical support and practical guidance for differentiated SPM management in long-distance water diversion systems.
Combined Ozone Micro-Nano Bubble Oxidation and Powdered Activated Carbon Adsorption for Removal of Taste and Odor Compounds from Drinking Water
Algal-derived taste and odor compounds (2-methylisoborneol, 2-MIB, and geosmin, GSM) in drinking water sources are poorly removed by conventional treatment. This study systematically evaluated the standalone and combined performance of ozone micro-nano bubbles (O3-MNBs) oxidation and powdered activated carbon (PAC) adsorption for removing 2-MIB, GSM, and algal cells from source water. Results showed that O3-MNBs pre-oxidation achieved >97.5% removal of odorants at 400 ng·L−1 and 67.2% algal cell removal within 30 min. When applied as a deep treatment stage, the degradation rate constant (k) was 10.1%–25.6% higher than in pre-oxidation due to lower background matrix interference. Both pre-oxidation and deep treatment reduced effluent concentrations of 2-MIB and GSM to below 10 ng·L−1, with oxidation kinetics fitting pseudo-first-order models (R²>0.95). PAC adsorption of both compounds followed pseudo-second-order kinetics (R²>0.99), with GSM equilibrium adsorption capacity approximately 20.0% higher than that of 2-MIB. In pure water, adsorption capacity increased by >10.0% compared to raw water. Based on kinetic models, a quantitative prediction method was established for O3-MNBs oxidation and PAC adsorption processes, aiming to achieve efficient odorant removal and cost optimization, providing theoretical support for advanced drinking water purification and smart water plant construction.
Pulsed Electric Field Enhancement of Nitrogen Removal Performance and Microbial Community Structure Response in Anammox Granular Sludge
This study investigated the effects of a ring-shaped pulsed electric field (PEF) (1.5 V, 4 h on-time per cycle) on nitrogen removal performance and microbial community structure of anammox granular sludge (AnGS). Two anaerobic sequencing batch reactors (R1 control, R2 with PEF) were operated under stepwise increasing nitrogen loading rates (NLR). At NLR below 1,155 mg·(L·d)−1, R2 exhibited total nitrogen removal efficiency (TRE) 7.5%–17.0% higher than R1, with biomass, specific anammox activity (SAA), and extracellular polymeric substances (EPS) increased by 5%–7%, 21%–71%, and 54%–77%, respectively. However, at NLR above 1,320 mg·(L·d)−1, the toxic effect of nitrite dominated, and PEF enhancement diminished or even reversed to inhibition. Microbial community analysis revealed that at low-to-moderate NLR, PEF increased the relative abundance of Planctomycetes and key anammox bacteria (Candidatus Brocadia and Candidatus Jettenia), along with enhanced community richness (Chao1) and diversity (Shannon/Simpson indices). At high NLR, PEF decreased microbial richness compared to R1. Principal component analysis and redundancy analysis indicated that PEF was the key factor driving community differences at low-to-moderate NLR, whereas nitrite concentration became the dominant factor at high NLR. This study provides theoretical support for enhancing the resilience and engineering application of anammox processes.