Direct regeneration of spent LiFePO4 materials via a green and economical one-step hydrothermal process

Study on selective recovery of lithium from cathode materials of decommissioned lithium batteries and its impact on corporate economic and environmental benefits

With the accelerated depletion of non-renewable resources and increased demand for lithium batteries, green recycling of lithium has become a key issue nowadays. In this study, the effects of the mass ratio of potassium persulfate to the active material of battery cathode material, roasting temperature, time, liquid-solid ratio and leaching time on the leaching rate of lithium, cobalt, nickel and manganese were investigated. For lithium-cobalt oxide battery materials, the optimal conditions were a mass ratio of K₂S₂O₇ to LiCoO₂ of 2:3, a roasting temperature of 700 °C for 60 min, and a lithium leaching rate of 98.51% and a selective leaching rate of 99.86%. For the ternary material NCM523, the optimal conditions were 1:2 mass ratio, and the lithium leaching rate reached 98.97%. The method has a positive corporate environmental impact by reducing the need for hazardous chemicals, lowering waste and operating costs, and avoiding harmful emissions. It is scalable and cost-effective and meets the needs of the battery recycling industry for environmentally friendly resource recovery. The K2S2O₇roasting-water leaching process proposed in this study effectively overcomes the problems of acid depletion and environmental pollution in the traditional recovery process, and provides a green and sustainable solution for the efficient recovery of lithium in lithium batteries in the future.

Direct Liquid-Phase Regeneration of Eluting Spent LiFePO4 Upgrade for Fast-Charging Cathodes Under Low Temperature and Ambient Pressure

With the widespread adoption of lithium iron phosphate (LiFePO4, LFP)-based power batteries, it is anticipated that a huge volume of spent LFP cathodes will be generated in the near future. Therefore, it is imperative to develop advanced, ecofriendly, and efficient recycling technologies for spent LFP cathodes. In this work, a low-temperature direct hydrothermal regeneration strategy with a rapid eluting process is introduced for the spent LFP cathodes. This regeneration strategy can effectively achieve multiple goals, including supplementing Li+ ions, eliminating irreversible phase transitions, maintaining the bulk initial structure, and repairing the evenly carbon-coated layer. Moreover, the regenerated LFP can induce the formation of a thinner and more uniform CEI film during the initial charge-discharge process, achieving a fast Li+ ion diffusion rate, enhanced discharge capability, and improved structural stability. Thus, the regenerated LFP exhibits a high initial discharge capacity of 164.2 mAh g-1 at a 0.1 C rate with an initial Coulombic efficiency of 98% and 132 mAh g-1 at 5 C with a remarkable capacity retention rate of 93.1% after 800 cycles. Specifically, this direct regeneration method is shorter in process and lower in cost compared with the traditional hydrometallurgy, enabling an eco-friendly regeneration under a mild environment, which shows a huge development potential in industrial applications.

Interfacial Metal-Solvent Chelation for Direct Regeneration of LiFePO4 Cathode Black Mass

Direct regeneration of spent lithium-ion batteries presents a promising approach to effectively reuse valuable resources and benefit the environment. Unlike controlled laboratory conditions that commonly facilitate impurity purification and minimize structural damage, the LiFePO4 cathode black mass faces significant interfacial challenges, including structure deterioration, cathode-electrolyte interphase residues, and damage from storage procedures, which hinder lithium replenishment and structure regeneration. Here, a metal-solvent chelation reaction using a lithium acetylacetonate solution is introduced to address these challenges under ambient conditions. This method regulates the near-surface structure through strong chelation between Acac‒ anions and Fe (III) elements, thus effectively eliminating the degraded amorphous phase and residual fluorine compounds. By direct lithium connection and reducing diffusion barriers, the reconstructed surface facilitates the re-lithiation process. The regenerated LiFePO4 cathodes demonstrate a capacity retention of 88.5% after 400 cycles at 1 C, while also outperforming traditional recycling methods in terms of environmental and economic benefits. This approach provides a promising solution for regenerating degraded LiFePO4 cathodes from actual dismantled black mass, thereby accelerating the practical application of battery recycling.

Design Principles for Efficient Hydrothermal Relithiation of Spent Lithium Iron Phosphate

Direct regeneration, which involves replenishing lithium in spent cathode materials, is emerging as a promising recycling technique for spent lithium iron phosphate (s-LFP) cathodes. Unlike solid-state regeneration, the aqueous relithiation method consumes less energy, ensures even lithium replenishment, and significantly recovers the capacity of s-LFP. However, liquid-phase lithium replenishment formulations are generally less standardized. In this study, we propose designing principles for hydrothermal relithiation recipes to achieve efficient relithiation while ensuring a high yield of relithiated LFP products, assisted by various electrochemical techniques. This led to the discovery of an economical hydrothermal relithiation approach. Specifically, using sulfurous acid (H2SO3) as the reducing agent and LiOH as the lithium source in the hydrothermal precursor, we achieved complete relithiation at a mild hydrothermal temperature of 90 °C with a high yield (only 3.1% mass loss) of relithiated LFP products. The regenerated LFP recovers approximately 29% of its capacity and exhibits remarkable capacity retention (98.9%). This research highlights a significant advancement in the efficient hydrothermal regeneration of s-LFP, presenting a green and economically viable method for LFP recycling and setting a benchmark for sustainable battery recycling technologies.

A review on direct regeneration of spent lithium iron phosphate: From waste to wealth

Lithium iron phosphate (LFP) batteries are widely used due to their affordability, minimal environmental impact, structural stability, and exceptional safety features. However, as these batteries reach the end of their lifespan, the accumulation of waste LFP batteries poses environmental hazards. Recycling these batteries is crucial for mitigating pollution risks and enabling secondary resource utilization. Traditional metallurgical recycling methods offer limited economic returns for waste LFP batteries due to their relatively low value compared to other types of cathode materials. Therefore, direct regeneration has emerged as a simpler, more cost-effective, and promising alternative. Given the stable crystal structure of LFP after decommissioning, direct regeneration by repairing lithium vacancy defects presents significant potential. This paper critically reviews the research progress on LFP regeneration, particularly focusing on developments over the past five years, and evaluates the industrial feasibility and pros and cons of these methods. Grounded in the concepts of wealth and waste, this paper adopts a novel perspective to discuss the processes of LFP degeneration and regeneration. It examines the dual attributes of waste and wealth in waste LFP batteries, elucidating the relationship and transformation between these two aspects. In particular, the paper discusses the value of LFP in its three forms-new, second-life, and waste-and the environmental and safety impacts of waste LFP batteries. It emphasizes the importance of converting waste into wealth and the role of regeneration as a potential means in the LFP recycling process. The paper objectively assesses the current challenges and opportunities, aiming to provide insights into the importance of LFP battery recycling and to explore potential avenues for advancing regeneration technologies through this comprehensive review.

Direct Regeneration of Degraded LiFePO4 Cathode via Reductive Solution Relithiation Regeneration Process

The rapid growth of electronic devices, electric vehicles, and mobile energy storage has produced large quantities of spent batteries, leading to significant environmental issues and a shortage of lithium resources. Recycling spent batteries has become urgent to protect the environment. The key to treating spent lithium-ion batteries is to implement green and efficient regeneration. This study proposes a recycling method for the direct regeneration of spent lithium iron phosphate (LFP) batteries using hydrothermal reduction. Ascorbic acid (AA) was used as a low-cost and environmentally friendly reductant to reduce Fe3+ in spent LiFePO4. We also investigated the role of AA in the hydrothermal process and its effects on the electrochemical properties of the regenerated LiFePO4 cathode material (AA-SR-LFP). The results showed that the hydrothermal reduction direct regeneration method successfully produced AA-SR-LFP with good crystallinity and electrochemical properties. AA-SR-LFP exhibited excellent electrochemical properties, with an initial discharge specific capacity of 144.4 mAh g-1 at 1 C and a capacity retention rate of 98.6% after 100 cycles. In summary, the hydrothermal reduction direct regeneration method effectively repairs the defects in the chemical composition and crystal structure of spent LiFePO4. It can be regarded as a green and effective regeneration approach for spent LiFePO4 cathode materials.

Dynamic Li+ Capture through Ligand-Chain Interaction for the Regeneration of Depleted LiFePO4 Cathode

After application in electric vehicles, spent LiFePO4 (LFP) batteries are typically decommissioned. Traditional recycling methods face economic and environmental constraints. Therefore, direct regeneration has emerged as a promising alternative. However, irreversible phase changes can significantly hinder the efficiency of the regeneration process owing to structural degradation. Moreover, improper storage and treatment practices can lead to metamorphism, further complicating the regeneration process. In this study, a sustainable recovery method is proposed for the electrochemical repair of LFP batteries. A ligand-chain Zn-complex (ZnDEA) is utilized as a structural regulator, with its ─NH─ group alternatingly facilitating the binding of preferential transition metal ions (Fe3+ during charging and Zn2+ during discharging). This dynamic coordination ability helps to modulate volume changes within the recovered LFP framework. Consequently, the recovered LFP framework can store more Li-ions, enhance phase transition reversibility between LFP and FePO4 (FP), modify the initial Coulombic efficiency, and reduce polarization voltage differences. The recovered LFP cells exhibit excellent capacity retention of 96.30% after 1500 cycles at 2 C. The ligand chain repair mechanism promotes structural evolution to facilitate ion migration, providing valuable insights into the targeted ion compensation for environmentally friendly recycling in practical applications.