Progress and perspectives on recycling spent electrolytes in lithium-ion batteries: A review

Recovery techniques

The approaches for enhancing electrolytes can be classified into methods such as freezing techniques (Zhao, 2016; Zhu et al., 2020), mechanical techniques (Yan, 2017; Zachmann et al., 2023a), solvent extraction techniques (He et al., 2019; Hu et al., 2016; Zhu et al., 2020), and supercritical extraction techniques (Fornereto Soldan et al., 2021; Molino et al., 2020; Mönnighoff et al., 2017). Of these techniques, freezing method reduces the activity of solvent molecules in electrolyte, weakening their diffusion ability and thereby minimizing evaporation and decomposition. As a result, the electrolyte can be quickly solidified, making it easier to recover. However, this method also faces challenges like a low recovery rate, high energy consumption, and demanding equipment requirements. To address these issues, cryogenic liquid nitrogen freezing method is commonly applied in industrial production to safely treat and crush SLIBs at extremely low temperatures. In contrast, the solvent extraction technique has become the favored technique for recovering electrolytes because of small energy requirements, higher recovery rate, and capacity to recycle extracting reagent (Shi et al., 2023). The electrolyte can undergo further processing for resource recovery only after the enrichment stage. Strategies for utilizing electrolyte resources include extracting valuable components and directly employing purified electrolytes for various uses. The goal of reclaiming valuable components is to isolate organic solvent from the Li-salts present in electrolyte and transform it into products of high purity (He et al., 2019; Zhang, 2021). Once the enriched electrolyte has been acquired, it needs to undergo additional processing to be utilized as a valuable resource. It is to isolate and refine individual components of electrolytes to manufacture products while prioritizing environmental sustainability, or to remove contaminants from the electrolytes to facilitate resource recovery. Because the boiling temperatures of the various electrolyte components vary, the effective separation of lithium salts from organic solvents can be achieved using straightforward methods like distillation. But despite that, LiPF₆ contains lithium, phosphorus, fluorine, and many various elements that hold greater value than organic solutions and pose greater environmental hazards. Consequently, the strategies for utilizing lithium salt resources can be divided into two main types: direct extraction and conversion of components (He et al., 2019). Direct extraction maintains the structure of lithium salts and efficiently transforms isolated lithium salt into a higher purity LiPF₆ end product (Li et al., 2012). Hu et al. (2016) immersed the disassembled spent LIBs in an organic solvent to isolate electrolyte, subsequently concentrating extracted electrolyte in vacuum at temperatures between 100 and 140°C in anhydrous hydrogen fluoride (HF) gas environment to produce LiPF₆.The resulting lithium hexafluorophosphate has high purity and can be directly applied in the preparation of new battery electrolytes. Additionally, it enables effective resource recycling, helping to lower battery production costs, conserve resources, and promote environmental protection. Lain et al. (2001) employed a comparable technique to mechanically grind spent LIBs in an inert gas environment. Subsequently, electrolyte is extracted with solvents like acetonitrile and n-methyl-2-pyrrolidone. Ultimately, organic solvent from electrolyte was removed via low-pressure distillation, yielding purified LiPF₆. This process is straightforward to implement, allows for effective recovery, and is appropriate for industrial outputs. Zhang (2021) employed component transformation technique to isolate each element in electrolyte that was initially separated through ultrasonic solvent extraction, followed by separation of resulting electrolyte using vacuum distillation. Although different techniques have been created for extraction of valuable components from electrolytes, these techniques remain in the laboratory development phase, primarily because of their complexity, potential for secondary pollution, and high costs. As a result, some research has focused on either directly purifying or supplementing the recovered electrolyte with suitable components to create a functional new electrolyte. Cheng (2019) and Wang et al., 2020 were first to employ organic solvent soaking after manual dismantling to retrieve electrode sheets and electrolyte solution from Aqueous lithium-ion batteries (ALIBs), which have garnered widespread attention due to their high-safety, low-cost, and eco-friendly nature. He then combined them thoroughly, assessed composition and concentration of electrolyte at that moment, and finally added necessary amounts of components based on the requirements to formulate a new electrolyte product. Chen (2016) initially produced the electrolyte through a solvent extraction process, followed by low-pressure distillation to isolate organic solvent from concentrated Li-salt solution. Recent studies indicate that advancements in electrolyte recovery will depend on both process innovation and integration of existing methods. Solvent regeneration pathways have achieved recovery of LiPF₆ with purity levels exceeding 90%, enabling direct reuse in fresh electrolytes.

Resource utilization

Synergistic combinations of technologies further enhance outcomes: Mechanical pretreatment improves processing by reducing particle size, vacuum distillation under reduced pressure enables efficient purification, and solvent extraction combined with supercritical CO₂ allows selective recovery of both organic solvents and lithium salts without residual contamination. Together, these hybrid approaches represent practical pathways towards industrial scalability and environmental sustainability. When comparing individual methods, it becomes evident that no single approach is universally optimal. Solvent extraction achieves high recovery efficiency but relies on organic solvents that pose toxicity concerns and require additional recovery systems. Supercritical CO₂ offers an environmentally benign alternative, yet the cost and scale of high-pressure equipment remain barriers to commercialization. Pyrolysis is relatively scalable and energy-efficient, generating syngas by-products, though strict control of fluorine emissions is essential to prevent secondary pollution. Alkaline absorption provides a simple option but produces large volumes of high-pH wastewater that demand costly treatment. Freezing and vacuum distillation are safe and clean, but face challenges of high equipment costs or limited recovery rates. Consequently, hybrid systems that integrate physical, thermal, and chemical processes appear most promising for balancing efficiency, economic feasibility, and ecological sustainability in large-scale electrolyte recycling. Therefore, when looking at the recycling procedure to prevent additional pollution, it is essential to investigate methods for producing recovered electrolyte outputs or different higher purity organic solvents or Li-salts. Presently, strategies for utilizing electrolyte resources include recovering important components and direct use of the electrolyte following its purification. In the field of electrolyte recycling, current research has primarily concentrated on the development and optimization of processing technologies. While many studies report the maximum recovery efficiency of lithium and organic solvents or the regeneration performance of electrolytes under ideal conditions, the associated recycling costs are often overlooked. Additionally, since the recycling process typically involves the use of chemicals, heating or mechanical-physical treatments, it is essential to assess the resulting energy consumption and waste liquid generation.

Environmental and economic assessment

To comprehensively evaluate and compare different electrolyte recycling methods, incorporating economic analysis and life cycle assessment (LCA) is crucial. These tools provide valuable insights into both the economic feasibility and environmental impacts of the processes, thereby supporting the development of more sustainable and cost-effective recycling strategies (Niu et al., 2023b). Ultimately, this approach can identify the most environmentally sustainable and economically viable electrolyte treatment process for industrial-scale recycling. However, to date, there have been no comprehensive studies conducted that detail economic analysis and LCA of electrolyte recycling. Addressing this gap represents a promising direction for evaluating the economic and environmental advantages of various recycling methods.

By implementing these methods, the electrolyte from waste LIBs can be effectively recycled, preventing environmental pollution while ensuring high efficiency and sustainability. The recovered product can be reused as electrolyte in the lithium battery industry, thereby conserving resources and reducing pollution.

Physical methods

Researchers typically divide into two categories: mechanical pretreatment and manual pretreatment. These categories include processes such as skinning, dismantling, crust removal, magnetic separation (Ding et al., 2024; Hu et al., 2022), mechanical or crushing, dissolution, washing (Li et al., 2024b; Premathilake et al., 2023; Yu et al., 2023), and screening that facilitate the recovery of electrode materials from spent LIBs without resorting to chemical treatment. Numerous researchers have demonstrated benefits of pretreatments in recovery processes for spent LIBs (Contestabile et al., 2001; Zhang et al., 2014, 2018a).

Chemical methods

The chemical method is a key division of metal recovery from utilized LIBs that is further divided into two categories: pyrometallurgy and hydrometallurgy. Hydrometallurgical techniques primarily involve leaching (using acid and alkaline solutions) (Punt et al., 2022), solvent extraction (through chemical precipitation and electrolysis), filtration, and electrochemical methods (Li et al., 2023, 2024a), bioprocessing (Roy et al., 2021; Sethurajan and Gaydardzhiev, 2021), and various combinations of these processes (Lv et al., 2024). Pyrometallurgical techniques like pyrolysis have also been used to recycle electrolytes. Also, there are some other methods, like freezing and vacuum distillation, that have been explored by researchers. All the above-mentioned processes have been discussed in this section.

Pyrolysis

Pyrolysis refers to the process of breaking down materials through heat at elevated temperatures while in an inert environment and is considered a viable option for managing used LIBs (Benallal et al., 1995; Bernardes et al., 2004; Olabi et al., 2022). This method demonstrates great potential for recovering spent LIBs. The organic solvent is broken down into low-molecular-weight products. It helps preserve valuable metals from oxidation, which allows effective recovery of Co and Li and safe processing of LiPF₆ (Liu et al., 2019; Wang et al., 2019). Various studies on pyrolysis have been listed in Table 2. Further, for direct pyrolysis of electrolytes, it is recommended to use physical methods for collection prior to conventional or advanced metallurgical processing. This approach supports closed-loop recycling and helps minimize the risk of environmental pollution (Fahimi et al., 2023; Shi et al., 2024), and common physical enrichment methods of electrolytes include distillation, condensation, freezing, normal temperature dry treatment, which typically must be performed under inert gas protection (Milian et al., 2024; Yu et al., 2024).

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Table 2.

Extensive literature review on pyrolysis of electrolytes of spent LIBs.

Process	Pretreatment	Process parameter	Additional product	Outcomes/remarks	Ref.
Pyrolytic gasification of spent electrolytes	Discharging and dismantling	650°C, 30 minutes, nitrogen gas flow rate: 35 mL/minute Electrolyte/cathode material mass ratio –- 1:0.1	Methane and H2, CO, LiF syngas	• Effects of temperature and rate of nitrogen flow on electrolyte gasification rate were studied. • Lithium extraction through water leaching. • The gasification rate of electrolytes was 96.38% • Lithium extraction rate: 98.93%.	Mi et al., 2023
CO2-assisted thermolysis	Discharging and dismantling	500°C, 100 mL/minute CO2	H2, CO2, CO, C2H4, and CH4	• Valorization of electrolyte (1M LiPF6 in EC/EMC) for syngas production. NCM 811 was used as a catalyst. • CO₂ and catalyst-enhanced CO formation via gas-phase reactions. Maximizes recovery of organic and metallic compounds.	Jung et al., 2021
Pyrolysis of spent NCM LIBs	Discharging, grinding/ screening, magnetic separation	Up to 1000°C 50 mL/min, 10°C/minute, Pure N2 gas	Ni/Co powders, Mn/graphite powders	• 100–200°C: Electrolyte volatilization, E = 98.6 kJ/mol. • 400–500°C: Organics decomposition, initial cathode reduction, E = 227.2 kJ/mol. • 650–800°C: NiO, CoO reduction, E = 258.8 kJ/mol. • 850–1000°C: MnO reduction, graphite gasification, E = 334.9 kJ/mol. • Temperature adjustment enables product and phase control. Low activation energy, fast reaction, energy-saving.	Tao et al., 2023
Pyrolysis of spent LCO LIBs	Discharging, shearing crusher	500°C, 300 mL/minute, 20 minute, N2 gas	H2,HF, pyrolytic gas, lithium carbonate, and cobalt sulfate	• Fluorine is converted to HF and absorbed by Ca(OH)₂ solution. Carbonated water leaching (87.9% efficiency); crystallized as lithium carbonate. • Reductant-free acid leaching (99.1% efficiency); crystallized as cobalt sulfate. • Inexpensive, eco-friendly, selective, and high-yield recycling.	Tao et al., 2022
Synergistic vacuum catalytic co-pyrolysis	NaCl discharging, manual dismantling, vacuum pyrolysis	530°C, Catalyst—CaO-ZSM-5, 100 Pa	Light fuel (hydrocarbons and alcohols)	• An approximately 100% defluorination rate is achieved. • PVDF and electrolyte are directionally converted into light fuel, yield 91.47% • The possible reaction mechanisms of electrolyte and PVDF were proposed.	Zhang et al., 2023b
Pyrolysis-enhanced flotation technology	Discharging, mechanical crushing, vacuum pyrolysis	550°C, Heating rate: 10°C/minute, 15 minutes, 200 mL/minute N2 gas flow rate	Pyrolysis oils and gases from organic removal are by-products.	• Enhancing the hydrophilicity contrast between LiCoO2 and graphite. • LiCoO2 purity raised from 67 to 98% following a 2-stage flotation process. • Cost-effective, eco-friendly, and efficient separation method for electrode materials. • Optimize flotation parameters and address residual pyrolysis product removal.	Zhang et al., 2019
Normal temperature dry treatment	Combined with other methods	High-pressure N2 purging	—	• This design integrates efficient nitrogen-assisted electrolyte transfer, dimethyl carbonate-based settling, and a closed-loop recycling system.	Z. Yang et al., 2019
Falcon centrifuge of LiCoO2 and graphite particles	Discharging, sieving, and grinding, mechanical crushing, Falcon centrifuge	0.025 MPa, 50 Hz, High-speed centrifugal, particle size range 0.045–0.09 mm	—	• Separation based on density and particle size, with higher-density LiCoO2 forming the bottom stream. • Falcon centrifuge provides efficient, cost-effective separation of graphite and LiCoO2. • Grade of LiCoO2 is 84.87%.	Zhang et al., 2018b
Low-temperature volatilization	Discharging, physical separation,	Temp:120°C for 2 hours under nitrogen N2 gas	Light alkenes, composed of light alcohols and aromatic long-chain alkenes, are reusable as fuel.	• Particle size distribution: Active materials <0.25 mm, current collectors >1 mm. • Water cleaning: Removes active materials from current collectors (1–0.25 mm). • Color sorting: For separating current collectors. • Recovered organic electrolyte 99.91%	Zhong et al., 2019
Two-stage thermal process	Discharging, dismantling	Stage 1: 45 rpm, 85°C, 30 minutes Stage 2: 300°C	Alkali type: KOH or Ca(OH)₂	• The study identifies 300°C as the optimal temperature to maximize the organic matter content in the pyrolysis oil while minimizing gas production. • This temperature enhances electrolyte recycling and environmental safety. PF6 is present in the concentrated electrolyte.	L Wu et al., 2024a

LIBs: lithium-ion batteries; PVDF: Polyvinylidene Fluoride.

This technique has become very popular for removing organic parts like binders and electrolytes (Andooz et al., 2022; Fahimi et al., 2023; Milian et al., 2024; Shi et al., 2024). It was initially used for coal conversion, recycling rubber tires, and treating biomass, but in recent years, it has been progressively adopted for recycling of spent LIBs (Arabiourrutia et al., 2020). In a complete pyrolysis process that has been previously suggested, unsorted and crushed batteries were subjected to direct thermal treatment, allowing for the effective elimination of organic materials and reductive breakdown of cathode substances (Tao et al., 2021). Pyrometallurgical techniques, including roasting, oxygen-free pyrolysis, and molten salt processing, could transform spent LIBs into a variety of outputs like metallic alloy, slag, and gases. At reduced temperature (150°C), gaseous by-products consist of volatile organic compounds resulting from electrolyte and binder materials. When the temperature rises, the polymer breaks down and combusts (Ali et al., 2022; Zhou et al., 2021). Additionally, a method integrating pyrolysis technology and flotation has been developed to extract LiCoO₂ and graphite from used LIBs. The two-stage process of pyrolysis-enhanced flotation can improve purity of LiCoO₂ to a grade of 98% (Zhang et al., 2019).

After undergoing pyrolysis, the majority of organic substances present in spent LIBs are broken down, while key components such as aluminum, copper, and active materials remain in the residues from pyrolysis. A general flowchart of the pyrolysis of electrolytes of spent LIBs is described in Figure 2. Physical separation methods necessitate minimal use of chemical agents and produce relatively low quantities of wastewater or gas (Al-Thyabat et al., 2013; Aurbach et al., 2004; He et al., 2017).

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Figure 2.

Flowchart of recovery of electrolytes from spent LIBs using pyrolysis.

Future developments in pyrolysis technology are expected to focus on multicomponent or full-component co-pyrolysis, alongside the environmentally friendly defluorination of electrolytes. These advancements aim to enable highly efficient recovery of precious metals and the production of syngas. In summary, pyrolysis stands out from other recovery methods as a scalable and versatile technique that not only enables safe treatment of electrolytes but also facilitates recovery of valuable metals without extensive oxidation. Its compatibility with physical pretreatment methods and potential integration with hydrometallurgical or other recovery processes further enhances its applicability within closed-loop recycling systems. However, despite these advantages, key research gaps remain, including optimizing operating conditions for large-scale applications, improving efficiency in separating and purifying recovered products, and addressing energy consumption to ensure overall sustainability. Continued investigation into these areas will be essential for advancing pyrolysis as a practical and environmentally responsible solution for LIB recycling.

Solvent extraction

This method involves the collection of electrolytes through the introduction of suitable organic solvents to electrodes and separators. Introduced solvents possess a dissolution capacity that is comparable to that of the electrolyte. This involves immersing the crushed spent LIBs in the solvent, facilitating transfer of electrolyte into the solvent, and subsequently extracting electrolyte from solvent. Different approaches attempted by researchers using this process to recycle electrolytes have been presented in Table 3.

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Table 3.

Summary of solvent extraction of electrolytes of LIBs.

Process	Pretreatment	Process parameter	Additional product	Outcomes/remarks	Ref.
Solvent extraction process	Discharging, disassembling, and dismasting	DMC solution and TMS, TMOS, Temp: 60–80°C	LiPO2F2, HF	• The reaction mixture is filtered, and the liquid solvent is reused in leaching. • Organosiloxane is added, and the solid LiPO₂F₂ is purified for reuse. • Solvents and siloxanes can be recycled.	Xia et al., 2022
Detoxified approach of residual electrolyte	NaCl discharging, disassembling	250 mL, DMC solution, 24 hours, Temp: 50°C	CaF2	• DMC is used as a solvent to wash away LiPF₆, while NaOH is controlled to facilitate the complete precipitation of fluoride ions as CaF₂. • Recovers CaF₂ for economic value	Zhu et al., 2020
Solvent extraction process	Discharge and disassembly, freezing, crushing	Leaching Temp: 10- 50°C Pressure: 2000–4000 Pa, Temperature:100–140°C, Time: 5–60 minutes	EC, DMC, EMC, Diethyl carbonate	• Crystalline LiPF₆ with high purity. • The filter and centrifuge extracting solution is treated with anhydrous HF gas. • The distillation fraction is recycled for further use.	Hu et al., 2016
Exfoliating and extracting solution (AEES) method	Discharging, shedding, and sieving	0.1 M Na salt solution, PH-11.6, 292.15 K, 0.005 M auxiliary, 20 minutes	CaF2 LiPF6	• AEES was used to peel cathode materials from aluminum foils and separate graphite from copper foils by weakening interlocking and Coulomb forces. • Electrolyte recovery rates are 95.6%.	He et al., 2019
Organic solvent extraction	NaCl discharging, disassembling	DMC solution, ultrasound stirring for 2 hours, 10 kPa, 30°C, vacuum distillation	LiF, CaF2, Ca3(P O4)2	• Ionic conductivity—2.2 S cm−1 at 120°C, activation energy 4.73 kJ/mol. • DMC extraction, vacuum distillation, water leaching for OP removal, controlled LiPF6 hydrolysis, and molecular sieve purification.	Shi et al., 2024
Solvent extraction method	Disassembling, freezing, crushing, centrifugal separation	Under ultrasonic 80 KHz, organic carbonate solution, centrifuge, 20–45°C, soaking time: 0.2–1 hours	Alkali liquor (saturated NaOH/KOH)	• Organic solvents include EC, PC, EMC, and DMC. Reduced-pressure distillation separates organic solvents. • High recovery efficiency over 98%.	Qiu et al., 2019

DEC: diethyl carbonate; DMC: dimethyl carbonate; EC: ethylene carbonate; EMC: ethyl methyl carbonate; HF: hydrogen fluoride; PC: propylene carbonate; TMS: trimethylsiloxane; TMOS: tetramethyloxysilane

Electrolyte is composed of organic solvents like ethylene carbonate (EC), propylene carbonate (PC), and dimethyl carbonate (DMC), along with a Li-salt and an additive (Schmitz et al., 2014; Tasaki et al., 2011). During recycling of spent LIBs, the electrolyte is susceptible to decomposition, volatilization, and the release of harmful gases. This issue is particularly pronounced during the thermal treatment of the electrolyte, which requires a gas collection device due to significant decomposition. Consequently, using thermal treatment for electrolyte recycling raises concerns about severe environmental pollution and high energy usage. On the other hand, solvent extraction for electrolyte recycling can mitigate these issues. The electrolyte is distributed within electrode materials and the separator. Following immersion of electrode materials in an organic solvent, the electrolyte moves into organic solvent. Subsequently, the organic solvent and the electrolyte are separated through distillation based on their differing boiling points. Numerous studies have utilized carbonate solvents to recycle electrolyte.

He et al. (2019) proposed that electrolyte dissolution entails dissolution occurring on the surfaces and within the pores of the electrodes and the separator. Approximately 90% of the electrolyte present on the electrode and separator surfaces dissolves within 3 minutes, while the remaining 10% trapped in pores could be dissolved over 20 minutes. Following distillation, 96% of the electrolyte is reclaimed as an organic mixture.

Virolainen et al. (2017) submerged cathode, anode, and separators in ethylene carbonate are used to reclaim the electrolyte. Following the extraction process, organic solvent and electrolyte are isolated through vacuum fractionation, allowing recovered electrolyte to be reused. The efficiency of different solvents, including PC, diethyl carbonate (DEC), and dimethyl ether (DME), was examined for recovering electrolyte. Their findings show that the electrolyte can be fully removed within 2 hours when PC is used (Tong et al., 2005). Wang (2016) and Zhu et al. (2020) employed DMC and acid ester solvent to retrieve electrolyte from fragmented spent LIBs. The method can efficiently isolate electrolyte from the spent LIBs body or pieces using solvent, and solvent can be recycled after undergoing distillation. But during the solvent extraction process, there is a loss of extractant, which not only raises expenses but also has the potential to generate additional pollution (Lei et al., 2022; Tao et al., 2023). He et al. (2019) incorporated organic solvents into an Aqueous Exfoliating and Extracting Solution, successfully recovering electrolyte via distillation and filtration, achieving a recovery rate of 96%. The electrolyte in LIBs usually serves to distribute electrode material and separator. The electrolyte can efficiently be transferred to an organic solvent by submerging it in an appropriate organic solvent. After dissolving, electrolyte was separated and recovered through distillation (Zhang et al., 2022b). Among the various enrichment methods, distillation, condensation, ambient temperature dry treatment, and solvent extraction exhibit lower energy consumption and costs than freezing and supercritical CO₂ extraction. Consequently, these three methods are favored for industrial applications.

Electrolyte is uniformly distributed within electrode materials and the separator. Distillation is employed to separate and recover organic solvent and electrolytes (Lei et al., 2022). A general flowchart of solvent extraction of electrolyte of spent LIBs is described in Figure 3. This approach combines high efficiency, recyclability, and relatively low cost, positioning it as a practical method for industrial-scale electrolyte recovery. Nonetheless, several limitations warrant further scrutiny. Reported recovery efficiencies vary considerably depending on solvent type and process conditions, underscoring the lack of standardization across studies. In addition, the inherent toxicity and volatility of commonly used carbonate solvents pose risks of secondary pollution in cases of solvent loss, raising both environmental and operational concerns. The energy-intensive nature and cost of distillation also remain significant barriers, particularly at scale, unless integrated solvent recovery systems are employed. Future research should therefore prioritize the development of greener, less hazardous solvents, alongside process intensification strategies and energy-efficient distillation technologies, to enhance both the environmental and economic viabilities of solvent extraction.

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Figure 3.

Flowchart of recovery of electrolytes from spent LIBs using solvent extraction.

Supercritical methods

In order to accomplish the goal of separation, this method is utilized to obtain specific components from liquids or solids by employing a supercritical fluid as the extracting agent (Fornereto Soldan et al., 2021; Manjare and Dhingra, 2019; Molino et al., 2020). The supercritical fluid exists at the critical point, characterized by specific pressure and temperature, situated between the gas and liquid states. It is excellent at dissolving a wide range of compounds and has low viscosity, great permeability, and a density comparable to that of a liquid. Diffusion coefficient is nearly one hundred times higher than that of an average liquid (Knez et al., 2019; Li and Xu, 2019). It is the perfect extractant for gathering electrolytes from wasted LIBs because of these unique characteristics. Due to its accessible critical point (7.38 bar pressure and 31.1°C), the significant solubility of nonpolar organic solvents, the comparatively gentle extraction method, high extraction efficiency, nontoxic nature, and the environmentally friendly recovery of electrolytes, CO₂ stands out as a wonderful supercritical fluid extraction medium for electrolytes found in spent LIBs (Grützke et al., 2014, 2015). Several articles have discussed this topic. Liu et al. (2014) successfully extracted four aging products (diethyl carbonate, dimethyl-2,5-dioxahexane dicarboxylate, ethylmethyl-2,5-dioxahexane dicarboxylate, and diethyl-2,5-dioxahexane dicarboxylate) using supercritical CO₂. Table 4 contains the various studies for electrolyte recovery from spent LIBs using supercritical CO₂.

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Table 4.

Supercritical CO₂ for electrolyte recovery.

Process	Pretreatment	Process parameter	Outcomes/remarks	Ref.
Supercritical CO2 technology	Discharging, disassembling	Temp: 38°C, 15 minutes, 10 MPa	• The bond between cathode material and aluminum foil was compromised as a result of the extraction of organic components using supercritical CO2. • Recycled cathode materials and electrolytes exhibit high purity.	Mu et al., 2022
Transcritical CO2 extraction	Discharging, dismantling	26–52°C, 6.5–18 MPa, Time: 20 minutes	• Detection of (PF6−), fluoride (F−), and (PO2F2−) indicating electrolyte degradation. • Extraction pressure is the key factor, with an optimized model enabling efficient electrolyte recovery above 96.8%.	Mu et al., 2017
Extraction by sub and supercritical CO2	NaCl discharging, disassembling	Temp: 40°C, 8–30 MPa	• Electrochemically aged cells revealed decomposition products: DMDOHC, EMDOHC, and DEDOHC. • Subcritical CO2 with acetonitrile achieved 89% recovery of electrolyte, including LiPF6.	Rothermel et al., 2018
Supercritical CO2 extraction	Discharging, dismelting	Temp: 40°C, 15 MPa, 30 minutes, 2.0 L/minute	• Li/LiCoO2 battery using reclaimed electrolyte demonstrates initial discharge capacity of 120 mAh·g−1 and retains 85% of its capacity after 100 cycles at a rate of 0.2 C.	Liu et al., 2017
Supercritical CO2 extraction	Discharge in liquid nitrogen, disassemble	35–40°C, 50 minutes, 24 MPa, 10% acetone	• Applicable to both power-type and digital-type LIBs. • Acetone used in the extraction process is 2–10% of CO2 mass. The recovered electrolyte is about 84.56%.	Gr et al., 2022

LIB: lithium-ion batteries.

However, only small amounts of the salt LiPF₆ were able to be retrieved. The type of electrolyte had significant influence on both recovery rate and component of solvents. Moreover, the concentration of the collecting solvents changed with temperature and was related to the development of solid electrolyte interphase. Additional purification steps, similar to distillation, a process would be necessary to separate desired organic carbonates from collecting solvents (Liu et al., 2014, 2016, 2017; Mu et al., 2022). Grützke et al. (2015) revealed that extracting DMC and ethyl methyl carbonate (EMC) from conventional LiNi_1/3Co_1/3Mn_1/3O₂ (NMC)/graphite 18,650 batteries using liquid CO₂ outperformed the method employing supercritical CO₂. Incorporating solvents into the CO₂ significantly enhanced the recovery of all components, particularly for LiPF₆, addressing its extraction challenge with CO₂. Utilizing liquid CO₂ at 25°C and 60 bar for 30 minutes, along with a flow rate of 0.5 mL/minute of an acetonitrile/propylene carbonate mixture in a 3:1 ratio, resulted in the collection of approximately 89.1 wt.% of the electrolyte, largely retaining the initial composition of DMC, EMC, and EC (1:1:1), along with 1.1 mol of LiPF₆, after an additional 20 minutes (Grützke et al., 2015). Similarly, the studies by Liu et al. (2014, 2016) focused on how various operating conditions affect the efficiency of electrolyte recovery, employing both single-factor and response surface methods. They created predictive model, suggesting that extraction of electrolyte could achieve around 86% when exposed to 23 Mpa pressure at 40°C, for 45 minutes, which corresponds closely with the expected results. The extraction pressure was found to have the greatest impact on electrolyte extraction. Additionally, evaluations conducted indicated that levels of organic solvents captured in electrolyte stayed steady during supercritical CO₂ extraction process, reinforcing its efficiency. Supercritical CO₂ extraction utilizes supercritical CO₂ as the extractant, offering advantages such as high efficiency, absence of secondary environmental pollution, and no solvent residues (Mu et al., 2022). Supercritical CO₂ extraction has been employed to recover electrolytes from LIBs. The study demonstrated that higher pressures and lower temperatures lead to increased extraction rates. While this method is environmentally friendly and nontoxic, its widespread application is limited by high equipment costs and low production capacity (Zheng et al., 2024).

To summarize, while supercritical CO₂ extraction of electrolytes is characterized by being eco-friendly, stable, harmless, noncombustible, secure, and enabling straightforward separation from the electrolyte, it proves to be inadequate for lithium salts such as LiPF₆ present in the electrolyte. A general flowchart of supercritical CO₂ of electrolytes of spent LIBs is described in Figure 4. The process requires the incorporation of additional organic solvents to capture complete composition of electrolyte. Thus, while supercritical CO₂ extraction represents a green and efficient route for electrolyte recovery, further advances in process intensification, cosolvent integration, and cost reduction are needed before it can be widely adopted at an industrial scale. At present, the technique remains in an early stage of application because of its high equipment cost, sensitivity to operating parameters, and comparatively low recovery of LiPF₆. To overcome these limitations, recent studies have emphasized the value of hybrid approaches, such as solvent-assisted supercritical extraction, which combine the environmental benefits of CO₂ with the enhanced solubility provided by organic cosolvents. Such integration may bridge gap between laboratory demonstrations and practical industrial deployment, highlighting the need for continued research on scalable, hybridized processes.

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Figure 4.

Flowchart of recovery of electrolytes from spent LIBs using supercritical CO₂.

Alkaline absorption method

The alkaline absorption technique can reduce the negative effects of directly releasing the electrolyte, but it generates numerous impurity ions. This method of extracting valuable substances from electrolytes via alkali absorption faces limitations, leading to the generation of considerable amounts of high-pH wastewater, which can also incur high management costs. Table 5 shows Li extraction through Alkaline absorption method.

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Table 5.

Li extraction through the Alkaline absorption method.

Process	Experimental conditions	Key findings	Ref.
Alkaline pressure leaching (LFP cathodes)	7 mol/L NaOH, 1.5-fold theoretical Ca(OH)2 250°C, 2 hours LFP cathode material	97.88% Li extraction efficiency with high selectivity. Fe and P content < 0.3% in leach solution Final Li product: high purity	Wu et al., 2025
Alkaline solvent extraction (Brine)	Counter-current mixer-settler process Extractants: HBTA-TOPO in kerosene Source: Alkaline brine with high Na/Li ratio	Average 96% Li extraction rate over 30 hours Li concentration in stripping solution:15 g/L Good stability and minimal emulsification observed over 30 cycles	Chen et al., 2024
Hydrothermal relithiation (Spent LFP)	Alkaline solution relithiation (ambient pressure, low temp)	Effective regeneration of LFP. Regenerated LFP showed high capacity and stability	Qing et al., 2024
NaOH leaching (LFP cathodes)	2 mol/L NaOH, L/S ratio of 50:1 mL/g, 50℃,2 hours spent LFP cathodes	98.2% Li leaching efficiency Selective extraction: all Fe converted to Fe3O4 precipitate	Gaye et al., 2019

LFP: LiFePO4.

This approach entails using alkaline solution to balance out acidic electrolytes. They treated electrolyte with Ca(OH)₂, leading to the formation of CaF₂ precipitate, while Li contained in electrolyte was recovered as a LiOH solution (Zhao et al., 2017). Cui et al. (2009) applied Ca(OH)₂ three times to increase pH of electrolyte, and the exhaust gases were effectively neutralized by being sprayed with water. Jiang (2020) dismantled the used LIBs, and then immersed and filtered them in a 5–8 mol/L of NaOH solution. Next, Xylene was added to filtrate for extraction, and organic layer was distilled to separate DME. Following this, the pH of the remaining filtrate was adjusted to alkaline conditions, and sodium carbonate was added to precipitate and isolate crude lithium carbonate precipitate and isolate crude lithium carbonate. The alkaline absorption method, especially alkaline pressure leaching, shows excellent potential for efficient and selective lithium recovery with high purity, particularly from specific LIB cathode materials like LiFePO₄. While the process involves multiple steps, it offers potential economic and environmental advantages.

In summary, alkaline absorption offers high recovery efficiency and product purity compared with many solvent-based methods and avoids the intensive energy demand of pyrolysis, yet it faces significant challenges that hinder large-scale application. The process generates substantial volumes of high-pH wastewater and impurity ions, driving up environmental management costs and limiting sustainability relative to supercritical CO₂ or solvent extraction techniques. While its simplicity and foundation in mature hydrometallurgical practices enhance scalability, its multistep nature and waste management issues constrain competitiveness. As a result, the industrial viability of alkaline absorption will depend on innovations that minimize wastewater production, streamline operations, and enable integration with complementary recovery processes.

Vacuum distillation method

The method of vacuum distillation entails heating electrolyte in a vacuum atmosphere, which leads to its evaporation, followed by the retrieval of the vaporized electrolyte via condensation (Xu et al., 2023). This method of recycling would not create further pollution. Li et al. (2012) disassemble a battery in an inert gas atmosphere to achieve electrolyte, which was then isolated into an organic solvent and LiPF₆ via vacuum distillation at a lower pressure. The purified products were subjected to a purification process to upgrade their purity, resulting in a recovery of up to 82.7% of LiPF₆ in its purified form. Li et al. (2016a) processed spent LIBs in a controlled inert gas atmosphere at temperatures ranging from 50 to 300℃ to retrieve the carbonate. Due to the highly volatile nature of electrolytes in their liquid form, they can be gathered through distillation, which initially involves heating the electrolyte from used LIBs to convert it into the gas phase, followed by collection through condensation.

Alternatively, the unstable electrolyte can be solidified through freezing for collection (Gr et al., 2022). Once frozen, the electrolyte becomes inactive and is challenging to volatilize and decompose, making it relatively easy to recover. The concept of distillation relies on phase changes among solids, liquids, and gases (Zhao et al., 2017). A general flowchart of supercritical CO₂ of electrolytes of spent LIBs is described in Figure 5.

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Figure 5.

Flowchart of recovery of electrolytes from spent LIBs using vacuum distillation.

Freezing and mechanical process

Freezing technique decreases movement of solvent molecules within electrolyte through intense cooling, which decreases the capacity of molecules to diffuse, thereby significantly lowering the evaporation and breakdown of the electrolyte (Liu et al., 2018a). This method enables the rapid conversion of the electrolyte into a solid form for retrieval. It entails converting electrolytes into a solid state, enabling their recycling. Solidified electrolyte is less susceptible to evaporation or degradation, which facilitates the recovery process. Battery cores were placed in liquid nitrogen for 10–20 minutes, causing the electrolyte to solidify into granules, which were then distilled at temperatures between 95 and 120°C using a heated distillation apparatus (Zhu et al., 2020).

Tadaaki (2007) described a method for cooling solid-state LIBs to temperatures below the solidification point of the electrolyte, followed by the disassembly of the batteries to isolate the electrolyte from the crushed remains. While this approach minimizes the likelihood of spent LIBs breaking down or catching fire during disassembly, it also presents challenges, including a low recovery rate, substantial equipment demands, and significant energy consumption. Freezing technique removes potential for electrolyte recycling and decreases the electrolyte’s activity. Nevertheless, the investment in equipment and energy expenses is significant, and the yield from recovery is low (Sloop, 2010).

Mechanical methods use external forces to remove electrolytes from spent LIBs. Yan (2017) utilized rapid centrifugation to handle the filtered and broken spent LIBs, successfully isolating them in order to extract the electrolyte. Zachmann et al. (2023b) demonstrate that electrolyte solvents, particularly DMC, EMC, and EC, were successfully recovered following a processing period of 4800 seconds at 130°C. The by-products resulting from the decomposition of LiPF6, specifically phosphoryl fluoride (POF₃) and hydrogen fluoride (HF), were spotted in exhaust gas stream and collected as acidic solutions. Yang (2019) developed a device for purging electrolytes that utilizes high-pressure airflow to expel the electrolytes from solid-state lithium batteries. While both methods allow for the recycling of electrolytes without altering its composition, they fail to entirely eliminate electrolytes from spent LIBs, leading to a little recovery rate. Furthermore, the electrolyte obtained through this process does not address the issue of lithium salts being prone to decomposition, resulting in environmental pollution and diminished purity of the recovered material. The method of mechanical separation uses physical processes to extract electrolyte. Li et al. (2015) utilized high-speed centrifugation to extract electrolytes. Procedure must occur in conditions where the moisture level is ⩽20 ppm. Maintaining a lower moisture level helps to avoid water absorption by the electrolyte, ensuring the quality of the electrolytes is higher. Mao et al., 2024 dismantled and crushed under negative pressure of 40,000 Pa–100,000 Pa. Afterwards, electrolyte was volatilized by introducing high-temperature gas stream with temperatures ranging from 90℃ to 280℃. Resulting volatilized gas was then condensed, filtered, and underwent defluorination to yield pure organic solvent. Components and temperature of high-temperature gas could be adjusted according to specific recovery requirements. This advancement facilitates recycling and repurposing of electrolytes at a lower cost, while also reducing secondary pollution. The studies using vacuum distillation, freezing, mechanical processing, and other methods are shown in Table 6.

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Table 6.

Various methods for recovery of electrolytes from spent LIBs.

Process	Pretreatment	Process parameter	Outcomes/remarks	Ref.
Low-temperature thermal treatment	Discharging, stored 2 days at −18°C	130°C, 80 minutes, Pure N2, exhaust HF and POF3	• Organic Solvent: EMC, EC, and DMC recovered effectively. • EC was recovered as solid; DMC and EMC recovered as liquid. Simple, feasible, and environmentally beneficial	Zachmann et al., 2023
Vacuum distillation method	Discharging, disassembling, vacuum pyrolysis	130°C, 120 minutes, discharge capacity 400 cycles at 1°C by Li/graphite battery	• Electrolytes exhibited significant discharge capacity and outstanding cycling performance, retaining 99% of their capacity after 400 cycles at 1°C in Li/graphite batteries. • High separation coefficients (>800) due to differences in saturated vapor pressures between DMC, DEC, and EC. • Recovery efficiency is 86.93% (purity 92.45%).	Xu et al., 2023
Distillation of electrolyte	Discharging, dismantling, crushing, powder suction	Temperature: 150–300°C, Argon or Nitrogen-protected	• Dissolve electrode materials in a diluted acid-hydrogen peroxide solution. • Separate carbon as a filtering residue; reclaim as anode material after washing and drying. • Precipitate transition metals using alkali liquor; recover as cathode material after washing and drying. Recovered EC DMC	Changqing et al., 2016
Mechanically separated using centrifugal process	Discharging, dismantling and screening	Temp: 50–80°C, ultracentrifugation: (>20,000 rpm), nitrogen or Ar gas	• Treat the residual battery with organic solvents under inert gas shielding. • Soak the filtered residue in acid solutions for 2–5 hours. • Add Na2CO3 to precipitate lithium as lithium carbonate.	Yan et al., 2017
Electrolyte recovery using the freezing method	Discharging and disassemble	Liquid nitrogen, 10–20 minutes, 50–200 mL of ethylene carbonate or dimethyl carbonate, pressure: 1000–1500 Pa	• Extracts over 90% of volatile electrolytes and solvents	Zhao et al., 2017
Green process to recover hexafluorophosphate	Discharging and disassembly	Two-stage extraction using Alamine336/TBP as extractant (0.4 mol/L, 5 minutes, O/A ratio = 1).	• Used NH₃·H₂O as a scrubbing agent. Combines liquid–liquid extraction with chemical precipitation for efficient PF6⁻ recovery. • Achieved 99.47% efficiency after two-stage operation.	LJ Wu et al., 2024b
Technique for recovering electrolyte of a SLIB	Disassembly and separation decoloring discharge battery, clean impurities, and dry.	Charcoal weight ratio: 1/10–1/5, 5 hours, operate under <30% humidity, moisture ⩽20 ppm	• Centrifuge and counter-current washing of battery core with organic solvent. • Reuse distilled solvent for washing and combine with recovered electrolyte.	Li et al., 2015
Electrolyte recovering	Discharging, disassembly	Pressure: (−0.02 to −0.07) MPa, Dew point temp: −40°C	• Puncture the battery with copper or diamond needles to form a discharge orifice for electrolyte flow. • Transfer the collected electrolyte to a nitrogen-protected reactor. • Add 30–50% barium ethoxide solution to recover lithium fluoride for reuse.	Li et al., 2016b
Method for recovering electrolyte	Discharging, manually open it into an inert atmosphere.	Cycle count: 3 to 5 cycles, pressure: −200 kPa to −50 kPa, 10 minutes, N2 or Ar	• Punching system: Creates openings in the battery cell. Vacuum system: Extracts electrolyte and elution solvent. • Liquid injection system: Injects the elution solvent into the cell. Elution tank: Collects and recovers the eluate. • Electrolyte 97% recovery rate.	Wu et al., 2022

DEC: diethyl carbonate; DMC: dimethyl carbonate; EC: ethylene carbonate; EMC: ethyl methyl carbonate; HF: hydrogen fluoride; SLIBs: spent lithium ion batteries; TBP: tributyl phosphate.

Comparison of different techniques

Across “Pyrolysis”, “Solvent extraction”, “Supercritical methods”, “Alkaline absorption method”, “Vacuum distillation method” and “Freezing and Mechanical method” sections, electrolyte recovery techniques for spent LIBs differ markedly in efficiency, energy consumption and cost. Pyrolysis offers robust removal of organic components and effective integration with downstream metallurgical processes, but its pyrolysis, high operating temperatures result in substantial energy demand and associated costs, limiting its attractiveness unless coupled with energy recovery or syngas valorization. Solvent extraction achieves high recovery efficiencies (>95% in many studies) at comparatively mild conditions and is currently among the most industrially viable approaches; however, solvent loss, distillation energy requirements, and secondary pollution risks remain key challenges. Supercritical CO₂ extraction (Section “Supercritical methods”) represents a green and selective alternative with minimal solvent residues, yet high capital costs, sensitivity to operating conditions, and limited LiPF₆ recovery constrain its large-scale application to niche or hybrid systems.

Alkaline absorption demonstrates high lithium recovery and selectivity, particularly for specific cathode chemistries such as LFP, but generates significant volumes of alkaline wastewater, raising environmental management costs. Vacuum distillation stands out for its relatively simple operation, moderate recovery efficiency (≈80–90%), and absence of chemical additives, making it attractive for industrial implementation where inert atmospheres and heat integration are available; nevertheless, its economic feasibility depends strongly on energy optimization and solvent reuse. Freezing and mechanical processes offer enhanced safety during dismantling and preserve electrolyte composition, but their high energy consumption (especially cryogenic cooling), low recovery yields, and substantial equipment requirements limit their scalability and cost competitiveness. Overall, solvent extraction and vacuum distillation currently present the most balanced trade-off between efficiency, cost, and scalability for industrial electrolyte recovery, while pyrolysis and supercritical CO₂ extraction are better suited as complementary or hybrid processes. Future industrial deployment is likely to favor integrated process chains that combine physical pretreatment with low-energy separation techniques, supported by solvent recycling and waste minimization strategies (Table 7).

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Table 7.

Comparative assessment of electrolyte recovery techniques for spent LIBs.

Recovery technique	Typical recovery efficiency	Energy demand	Economic considerations	Environmental aspects	Key strengths	Major limitations
Pyrolysis	High for organics (>90% removal); indirect electrolyte recovery	High (⩾500–800°C)	High capital and operating costs; viable if heat/syngas valorization is integrated	Potential gas emissions (HF, VOCs) unless controlled; requires inert atmosphere	Effective removal of binders/electrolytes; compatible with downstream metallurgical routes	High energy consumption; limited selectivity for LiPF₆; complex gas handling
Solvent extraction	Very high (95–98% reported)	Moderate (mainly distillation)	Moderate cost; solvent loss and distillation dominate OPEX	Risk of secondary pollution due to solvent volatility/toxicity	High efficiency; mild operating conditions; solvent recyclability	Solvent loss; energy-intensive distillation; lack of standardization
Supercritical CO₂ extraction	High for organic solvents (85–97%); low for LiPF₆ without cosolvent	Moderate–High (high pressure)	Very high capital cost; high-pressure equipment	Green, nontoxic, no solvent residue	Environmentally benign; selective extraction	Poor salt recovery; costly equipment; low throughput
Alkaline absorption	High Li recovery (≈95–98%)	Moderate	Moderate chemical cost; high wastewater treatment cost	Generates large volumes of alkaline wastewater	High selectivity for Li; suitable for LFP systems	Wastewater burden; multistep process
Vacuum distillation	Moderate–High (80–90%)	Moderate (lower than pyrolysis)	Relatively low chemical cost; energy cost dominates	Minimal secondary pollution if sealed	Simple operation; no solvents; good purity	Requires inert/vacuum systems; salt decomposition risk
Freezing and mechanical methods	Low–Moderate (<80%)	High (cryogenic cooling)	High CAPEX and energy cost	Safer disassembly; minimal chemical pollution	Preserves electrolyte composition; improved safety	Low yield; energy-intensive; not standalone

HF: hydrogen fluoride; VOC: volatile organic compounds; LFP: LiFePO4. Bold text indicate Important Parameter.

The methods have shown approaches for the recovery of key electrolyte components, including Li-salts and organic solvents, from spent LIBs. The upcoming section describes the major challenges and scope of future research.

Technical challenges in electrolyte recovery from spent LIBs

Electrolyte recovery remains technically underdeveloped compared with cathode and anode recycling, primarily due to the electrolyte’s low mass fraction (typically <10 wt.% of a LIB cell) and its entrapment within porous electrode and separator structures. Experimental studies indicate that approximately 70–80% of the electrolyte is retained within cathode pores and separator matrices, significantly reducing extraction efficiency through purely mechanical or low-temperature physical methods. This structural confinement necessitates either high-energy thermal treatment or solvent-assisted extraction to achieve meaningful recovery.

Thermal routes such as pyrolysis and vacuum distillation effectively liberate organic solvents but require elevated temperatures (typically >300°C for distillation and >500°C for pyrolysis), leading to high energy consumption and partial decomposition of lithium salts such as LiPF₆ into HF and POF₃. Supercritical CO₂ extraction achieves high recovery of organic solvents (often exceeding 85–95%), yet LiPF₆ recovery remains limited (<50%) unless organic cosolvents are introduced, complicating downstream purification. These limitations collectively highlight the intrinsic difficulty of selectively and safely recovering electrolyte components without compromising energy efficiency or product purity.

These challenges emphasize the importance of upstream battery design modifications, including reduced electrode porosity, controlled electrolyte distribution, and electrolyte formulations that facilitate drainage or selective extraction at end of life.

Economic constraints and industrial scalability

From an economic standpoint, electrolyte recycling often offers lower immediate financial returns than the recovery of high-value cathode metals such as cobalt or nickel, leading to its frequent omission in industrial recycling flowsheets. Solvent extraction, while achieving recovery efficiencies above 95%, incurs recurring costs associated with solvent make-up, solvent losses, and energy-intensive distillation. Supercritical CO₂ extraction requires substantial capital investment in high-pressure vessels, compressors, and safety systems, making it economically viable only at large scales or in specialized applications.

Cryogenic freezing and vacuum-based mechanical recovery approaches demand high energy input and specialized equipment, further limiting their competitiveness. Pyrolysis partially offsets operating costs through syngas generation; however, its overall energy intensity remains high unless integrated with heat recovery systems. As a result, many current processes struggle to achieve favorable cost-to-recovery ratios when electrolytes are treated as standalone products.

Integrated hybrid systems, such as mechanical pretreatment followed by vacuum distillation or solvent-assisted low-temperature separation offer promising routes to balance recovery efficiency (>80–90%), energy demand, and operational cost, particularly when embedded within existing LIB recycling plants.

Environmental and safety challenges

Electrolytes constitute the primary source of hazardous emissions during LIB recycling due to volatile organic carbonates and fluorinated lithium salts. Decomposition of LiPF₆ can generate HF, posing severe risks to workers, equipment, and the environment. Alkaline absorption methods achieve high lithium recovery (95–98%) but generate large volumes of high-pH wastewater, increasing treatment costs and environmental burden. Inadequate control of electrolyte handling can therefore negate the environmental benefits of battery recycling, especially when secondary pollution outweighs material recovery gains.

Converting unstable lithium salts into thermodynamically stable products such as Li₂CO₃, NaF or Na₃PO₄ during recovery not only mitigates safety risks but also aligns with downstream reuse and regulatory compliance. Closed-loop solvent recovery and defluorination strategies are critical for minimizing secondary emissions.

Emerging solutions

Recent research increasingly focuses on the next-generation electrolyte formulations that enhance recyclability. Alternative solvents such as nitriles, sulfones, and ionic liquids exhibit improved thermal stability and reduced volatility, while lithium salts such as LiFSI, LiBOB, and LiBF₄ generate less HF upon degradation than LiPF₆. These advances can significantly simplify recovery and purification processes.

Modular and adaptable recovery systems are also emerging as a key strategy. Adjustable distillation ranges, flexible separation parameters, and solvent-assisted supercritical extraction enable the same recovery unit to process electrolytes with varying compositions. Notably, several studies demonstrate that revitalized electrolytes—after solvent purification, salt conversion, and re-formulation—exhibit ionic conductivity and electrochemical performance comparable to commercial electrolytes, confirming the feasibility of direct reuse rather than downcycling.

Policy and regulatory drivers

Policy frameworks summarized in Table 8 provide strong external drivers for advancing electrolyte recovery technologies. The EU Battery Regulation (2023/1542) mandates lithium recovery rates of 50% by 2027 and 80% by 2031, implicitly requiring efficient recovery not only from cathodes but also from electrolytes. Additionally, mandatory carbon footprint declaration for batteries starting in 2024 favors low-energy recovery pathways such as solvent extraction and vacuum distillation. China’s extended producer responsibility policies emphasize full life cycle management and cross-regional recycling networks, creating incentives for integrated electrolyte recovery within centralized recycling facilities. Similarly, the U.S. National Blueprint for Lithium Batteries (2021–2030) prioritizes closed-loop recycling and domestic supply chain resilience, reinforcing the importance of recovering lithium salts and solvents rather than discarding electrolytes. These policies collectively signal a shift from metal-centric recycling towards comprehensive material recovery.

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Table 8.

Policies and regulations related to battery recycling.

Country	Release date	Policies and regulations	Key elements
United States	1996 2021	Mercury-Containing and Rechargeable Battery Management Act (Battery Act) (“Mercury Battery Act,” n.d.) The National Blueprint for Lithium Batteries 2021–2030 (“Policy. The National Blueprint for Lithium Batteries-2021,” n.d.-i)	a. Eliminating the use of mercury in batteries and ensuring the efficient, cost-effective collection of spent LIBs for recycling or proper disposal. a. Proposing the implementation of end-of-life reuse strategies for LIBs and the large-scale recycling of critical raw materials. b. Planning the development and spatial organization of a comprehensive value chain for spent LIB recycling.
European Union (EU)	2006 2023	The Battery Recycling Directive (Directive 2006/66/EC) (“Policy. The Battery Recycling Directive”, n.d.-h) New Batteries Regulation (“Regulation 2023/1542,” n.d.-e)	a. The minimum battery recycling rate in the EU increased from 25% in 2012 to 45% in 2016. b. Promoting efficient collection and recycling of waste batteries and accumulators to significantly reduce their environmental impact. a. By 2027, recovery rates are targeted to reach 50% for lithium and 90% for cobalt, copper, lead, and nickel; by 2031, these targets increase to 80% for lithium and 95% for cobalt. b. Starting July 2024, the carbon footprint of power and industrial batteries must be declared, with compliance to the specified limit values required by July 2027. c. By 2025, the new recycling rate targets for lithium-ion and lead-acid batteries are set at 65 and 75%, respectively.
China	2018 2019 2022 2022	Interim Measures for the Administration of Power Battery Recycling for New Energy Vehicles (“Policy. Interim Measures for the Administration of Power Battery Recycling for New Energy Vehicles, 2018,” n.d.-d) Industry Standard Conditions for the Comprehensive Utilization of New Energy Vehicles Waste Power Batteries (“Policy. Industry Standard Conditions for the Comprehensive Utilization of New Energy Vehicles Waste Power Batteries, 2019,” n.d.-c) Accelerating the promotion of the comprehensive utilization of industrial resources implementation program (“Policy. Accelerating,” n.d.-a) Peak Carbon Implementation Program for Industry (“Policy. Peak Carbon,” n.d.-f)	a. To implement an extended producer responsibility system that clearly defines the primary party responsible for battery recycling. a. Multilevel and multipurpose rational utilization of used power batteries from new energy vehicles, primarily encompassing echelon utilization and recycling. a. Promoting collaboration across upstream and downstream sectors of the industry chain to establish recycling channels and develop a cross-regional recycling system. a. Departmental regulations, including management measures for the recycling of power batteries from new energy vehicles, will be developed and implemented.
Australia	2020 2020	Battery Stewardship Scheme (“Policy. Battery Stewardship Scheme, 2020,” n.d.-b) Recycling and waste reduction bill 2020 (“Policy. Recycling and Waste Reduction,” n.d.-g)	a. Imposing a levy of up to 4 cents per EBU (24 grams) on imported batteries, with a rebate per kilogram provided to recyclers for collection, sorting, and processing at the end of the battery’s life. a. Implementing export bans on waste plastics, waste paper, waste glass, and waste tires. b. Encouraging companies to assume greater responsibility for the waste they produce. c. Emphasizing a strategic approach to advance battery recycling efforts.
Japan	2000 2022	Basic Act for Establishing a Sound Material-Cycle Society (Lin et al., 2020) End-of-Life Vehicle Recycling Law (Tang et al., 2020)	a. Defining the roles and responsibilities of the State, local governments, enterprises, and citizens within a recycling-oriented economy and society. b. Establishing a virtuous cycle of “resources, products, renewable resources” and advancing the rational treatment and recycling of end-of-life vehicles and their components.

Quantitative assessment needs

At present, detailed economic and LCA studies on electrolyte recycling remain absent, representing a significant gap and a promising direction for advancing sustainable, scalable, and cost-effective recycling pathways that align with Sustainable Development Goals and Net-Zero commitments (Arshad et al., 2022; Kallitsis et al., 2022; Lander et al., 2021; Rajaeifar et al., 2021; Rey et al., 2021; Slattery et al., 2021). Key performance indicators, such as energy consumption, solvent loss rates, wastewater generation, and carbon footprint—are rarely reported in a standardized manner. This lack of quantitative benchmarking hinders objective comparison of competing technologies and slows industrial adoption. Future research must integrate economic modelling and LCA alongside process development to identify scalable, low-impact recovery pathways aligned with sustainability targets, net-zero commitments, and circular economy principles.