Method for recovering lithium salt in state of charge waste lithium ion battery

Abstract

The present application relates to the technical field of electrode material recycling, and particularly relates to a method for recycling lithium salt in a lithium-ion battery with a state of charge. The method for recycling lithium salt in a lithium-ion battery with a state of charge comprises the following steps: disassembling a lithium-ion battery with a state of charge to obtain a lithium-embedded graphite negative electrode; placing the lithium-embedded graphite negative electrode into a solvent, allowing it to react and separate to obtain a lithium salt solution; and evaporating and concentrating the lithium salt solution to obtain lithium salt. The present application solves the technical problem of low leaching rate of lithium salt in the existing lithium-ion battery recycling technology, and also solves the problems of high cost, high energy consumption and poor environmental protection in the existing lithium-ion battery recycling technology.

Description

Technical Field

[0001] This invention relates to the field of electrode material recycling technology, specifically to a method for recycling lithium salts from spent lithium-ion batteries in a charged state. Background Technology

[0002] With the rapid development of the global new energy industry, the application scenarios of lithium-ion batteries continue to expand, and market demand is experiencing explosive growth. Statistics show that global demand for lithium-ion batteries is expected to approach 3600 GWh by 2030. Since the lifespan of batteries is generally 3-10 years, a large number of waste batteries will inevitably be generated in the future, making the development of efficient and sustainable recycling technologies particularly urgent.

[0003] Lithium, a key charge carrier and core element in batteries, is currently mainly extracted from hard rock and brine deposits, but the process is complex and inefficient. Although existing resources can meet market demand, the rapid expansion of the battery industry has put pressure on lithium supply, necessitating diversification of sources to mitigate risks. Against this backdrop, recovering lithium from spent lithium-ion batteries has become an important way to alleviate supply pressure and build a second lithium resource reserve.

[0004] Currently, hydrometallurgy is the mainstream technology for recycling cathode materials (such as layered, spinel, and olivine structures) from lithium-ion batteries. This method typically begins with battery dismantling to obtain "black powder" rich in metals such as lithium, cobalt, nickel, and manganese, which is then extracted through acid / alkali leaching and subsequent separation and purification steps. However, hydrometallurgical processes consume large amounts of strong acids or alkalis (up to 800 kg or more per ton of battery), are complex, and generate significant amounts of wastewater, resulting in a heavy environmental burden. In contrast, while pyrometallurgy is more adaptable to raw materials and has a simpler process, lithium readily forms stable compounds with silicon and aluminum at high temperatures, leading to leaching rates generally below 80%.

[0005] From an economic perspective, traditional recycling processes typically involve pre-discharging used batteries. If residual energy can be recovered during discharge (e.g., through grid connection or secondary use), approximately 50-150 yuan can be generated per ton of batteries, partially offsetting subsequent energy costs. However, if a discharge method without energy recovery is used, an additional processing cost of 80-200 yuan per ton is required.

[0006] However, keeping the battery in a charged state during lithium extraction offers several significant advantages: Firstly, the 10%–30% residual energy in the battery can be directly used to drive the chemical dissociation of the cathode material (such as promoting lithium-ion insertion / extraction and lattice activation), thereby reducing external energy input and decreasing lithium extraction energy consumption per ton of battery by 15%–30%. Secondly, this method avoids the cost and energy waste associated with the discharge stage, further improving the overall economic efficiency of the process. Simultaneously, operating the charged battery under controlled conditions allows for safety assurance through process design and maintains a high lithium recovery efficiency.

[0007] In summary, traditional wet and pyrometallurgical lithium extraction processes generally suffer from high energy consumption, high costs, and insufficient environmental friendliness, making them unsuitable for the large-scale green recycling industry demands. Therefore, developing a state-of-charge (SOC) based lithium extraction technology that achieves low energy consumption, low cost, environmental friendliness, and high efficiency has become a key breakthrough for the industry. Summary of the Invention

[0008] To address the problems existing in the prior art, this invention provides a method for recovering lithium salts from spent lithium-ion batteries in a state of charge, thereby solving the technical problem of low lithium salt leaching rate in existing spent lithium-ion battery recycling technologies. It can also solve the problems of high cost, high energy consumption, and poor environmental performance in existing spent lithium-ion battery recycling technologies.

[0009] The technical solution of the present invention is as follows: This invention provides a method for recovering lithium salts from spent lithium-ion batteries in a state of charge, comprising the following steps: S1. Disassemble the charged waste lithium-ion batteries to obtain lithium-intercalated graphite anodes; S2. Place the lithium-intercalated graphite anode in a solvent, allow it to stand and react, then separate to obtain a lithium salt solution; S3. Evaporate and concentrate the lithium salt solution to obtain lithium salt.

[0010] By dismantling spent lithium-ion batteries under specific states of charge (including fully charged state), the core recycling target—lithium-intercalated graphite anode—can be precisely obtained. This lays the foundation for the efficient separation and recycling of subsequent lithium salts, graphite, and copper foil, solving the technical problems of crude dismantling and inaccurate separation of target components in traditional recycling processes, leading to low recycling efficiency and low purity of recycled products. Through static reaction and separation operations at ambient temperature and pressure, multiple effects can be achieved simultaneously: First, through liquid-phase reaction, efficient leaching of lithium is achieved, allowing it to exist in the form of lithium hydroxide or lithium ethoxide, which is easily purified into lithium carbonate. This process also achieves effective separation of lithium from other heavy metals, with high recycling purity and a short process, improving the economic value of lithium recycling and solving the technical problems of low lithium leaching rate, difficulty in separating lithium from other heavy metals, and cumbersome purification processes in traditional processes. Second, by evaporating and concentrating the separated lithium salt solution, lithium salt can be directly obtained.

[0011] Meanwhile, the overall operation process of this method has the following significant advantages: First, the entire process requires no high-temperature roasting (pyrometallurgical) or high-temperature and high-pressure leaching; the reaction can be completed at room temperature or low temperature, significantly reducing energy consumption and solving the technical problems of high energy consumption in traditional pyrometallurgical processes and high equipment requirements and operating costs in wet high-temperature and high-pressure processes. Second, the complex multi-step unit operation of the traditional process of "crushing-sorting-acid leaching-lithium extraction-waste graphite treatment" is simplified to the core step of "reaction-separation." Lithium leaching, graphite desorption and purification, and copper foil separation can be achieved simultaneously in one reaction, greatly reducing equipment investment and operating costs and solving the technical problems of lengthy recycling processes, cumbersome unit operations, large equipment investment, and high operating costs in traditional recycling processes. Third, the recovered intact and clean copper foil has high purity and can be directly sold or returned to the metallurgical process, possessing higher economic value compared to traditional copper recycling products, solving the problems of low purity and high utilization costs in traditional copper foil recycling. In summary, this invention develops a method for recovering lithium salts from spent lithium-ion batteries in a state of charge, which can meet the industrial demand for large-scale, green recycling and solve the problems of high cost, high energy consumption, and poor environmental performance in existing spent lithium-ion battery recycling technologies.

[0012] Specifically, the state of charge is greater than 0%.

[0013] Furthermore, the ratio of the lithium-intercalated graphite anode to the solvent is 3 g: 30 mL.

[0014] By controlling the ratio of lithium-intercalated graphite anode to solvent to 3 g: 30 mL, it is possible to ensure that the lithium-intercalated graphite anode is fully wetted by the solvent, avoid reaction dead zones, and ensure efficient lithium leaching, complete preservation of the graphite layered structure, and non-destructive separation of copper foil. At the same time, it can avoid problems such as increased energy consumption for subsequent concentration and increased solvent recovery costs due to excessive solvent, or insufficient reaction and decreased product purity due to insufficient solvent. It is also suitable for large-scale production needs and helps to improve the economy and feasibility of the entire recycling process.

[0015] Furthermore, the solvent is selected from inorganic solvents or organic solvents.

[0016] Preferably, the inorganic solvent is water and the organic solvent is anhydrous ethanol.

[0017] Using water or anhydrous ethanol as a solvent offers the advantages of being mild, environmentally friendly, safe, efficient, and economically adaptable: both are non-toxic, harmless, and environmentally friendly green media, avoiding problems such as equipment corrosion and difficult waste treatment caused by traditional strong acids, strong alkalis, or toxic organic solvents. Furthermore, anhydrous ethanol does not produce hydrogen gas during the reaction and is inherently safe, while water is widely available and extremely low in cost. At the same time, these solvents can achieve selective extraction of lithium, simultaneously ensuring the integrity of the graphite layered structure and the non-destructive separation of copper foil. They can also reduce process energy consumption and the threshold for large-scale production, helping to achieve a greener, lower-cost, and higher-value recycling process.

[0018] Furthermore, the lithium salt is lithium carbonate; when water is used as the solvent, the leaching rate of the lithium carbonate is 98.19%; when anhydrous ethanol is used as the solvent, the leaching rate of the lithium carbonate is 72.86%.

[0019] Furthermore, in step S1, the disassembly is carried out in an inert gas atmosphere, wherein the inert gas is argon or nitrogen.

[0020] Disassembly in an inert gas atmosphere effectively isolates the active components (such as lithium-intercalated graphite, lithium salts, and residual metallic lithium) in waste lithium-ion batteries from air, preventing safety risks such as oxidation, combustion, and even explosion. It also prevents copper foil oxidation and corrosion, graphite structure damage due to oxidation, and lithium loss, ensuring the integrity and activity of the disassembled lithium-intercalated graphite anode. This lays the foundation for efficient lithium leaching in subsequent solvent reactions and high-purity recovery of graphite and copper foil, balancing process safety and product quality stability.

[0021] Furthermore, in step S2, the standing reaction time is 15-60 minutes, and the temperature is room temperature.

[0022] Furthermore, when the solvent is selected from organic solvents, S2 and S3 include: The lithium-intercalated graphite anode was placed in an organic solvent, allowed to stand and react, and then separated to obtain the anode sheet and the lithium salt solution. The lithium salt solution was concentrated by evaporation to obtain lithium salt.

[0023] Furthermore, the recycling method further includes: S4. Dry the negative electrode sheet, and then peel off the graphite and copper foil from the negative electrode sheet to obtain graphite and copper foil.

[0024] Specifically, the drying step includes: placing the negative electrode sheet in a forced-air drying oven at 80°C and drying it for 24 hours; the evaporation and concentration step includes: placing the lithium salt solution in a forced-air drying oven at 80°C and drying it for 24 hours.

[0025] The process of drying the negative electrode sheet and then peeling off the graphite and copper foil from it yields graphite and copper foil. Firstly, this process achieves graphite desorption and purification, ensuring the integrity and high purity of the recovered graphite structure. This solves the technical problems of graphite being easily oxidized and eroded in traditional pyrometallurgy and easily damaged by strong acids and alkalis in hydrometallurgy, preventing high-value reuse of graphite. Secondly, it achieves non-destructive separation of the copper foil from other components, ensuring the recovered copper foil is intact and clean, rather than fragments or copper slag. The recovered copper foil has high purity and can be directly sold as a product or returned to the metallurgical process, with a value far exceeding that of recovered copper powder or copper materials requiring remelting. This process is highly economical and solves the problems of fragmentation and low purity in traditional copper foil recovery processes.

[0026] Furthermore, when an inorganic solvent is selected as the solvent, steps S2 and S3 include: The lithium-intercalated graphite anode was placed in an inorganic solvent, allowed to stand and react, and the copper foil was removed to obtain a solution. Filtering the solution yields a lithium salt solution and crude graphite product; The lithium salt solution was concentrated by evaporation to obtain lithium salt.

[0027] Furthermore, the recycling method further includes: S4. Dry the crude graphite product to obtain graphite.

[0028] Specifically, the drying step includes: placing the filter residue in a forced-air drying oven at 80°C and drying it for 48 hours; the evaporation and concentration step includes: placing the lithium salt solution in a forced-air drying oven at 80°C and drying it for 48 hours.

[0029] Through the above steps, firstly, the non-destructive separation of copper foil from other components is achieved, ensuring that the recovered copper foil is intact and clean, rather than fragments or copper slag. The recovered copper foil has high purity and can be sold directly as a product or returned to the metallurgical process, with a value far exceeding that of recovered copper powder or copper materials that need to be remelted. This is extremely economical and solves the problems of easy fragmentation and low purity in traditional copper foil recycling processes. Secondly, the desorption and purification of graphite are achieved, ensuring that the recovered graphite has an intact structure and high purity. This solves the technical problems of graphite being easily oxidized and eroded in traditional pyrometallurgy and graphite structure being easily damaged by strong acids and alkalis in hydrometallurgy, which prevents graphite from being reused at high value. By drying the crude graphite product, high-purity graphite with electrochemical properties close to that of the original material can be obtained. This graphite can be directly used to prepare new lithium-ion battery anodes, realizing closed-loop recycling and high-value utilization of graphite materials.

[0030] The present invention also provides lithium salt recovered by the above method, wherein the lithium salt is lithium carbonate.

[0031] The beneficial effects of this invention are: Compared with traditional pyrometallurgical and hydrometallurgical methods, this invention offers several advantages. First, it achieves simultaneous high-value recovery of graphite, lithium, and copper foil, rather than focusing solely on the metals. This method enables the full-component, closed-loop, and high-value recovery of anode materials, completely overcoming the limitations of traditional recycling models. Second, the reaction system is more mild and environmentally friendly, avoiding the use of strong acids, strong alkalis, or toxic organic solvents. It innovatively uses anhydrous ethanol and water as the reaction medium. This system selectively extracts lithium while preserving the layered structure of graphite, minimizing structural damage. Furthermore, the anhydrous ethanol reaction process generates no hydrogen, ensuring excellent intrinsic safety. It produces no toxic waste gas, resulting in low emissions and a simple treatment process, perfectly aligning with the green and environmentally friendly recycling concept. Third, the recovered graphite exhibits minimal structural damage. Fourth, the sale of the recovered high-purity recycled graphite, lithium salts, and copper foil generates significant economic benefits, with recycled graphite providing a new, high-value-added source of profit.

[0032] This invention provides a method for recovering lithium salts from spent lithium-ion batteries in a state of charge. By disassembling the spent lithium-ion batteries under specific states of charge (including fully charged state), the core recovery target—lithium-intercalated graphite anode—can be accurately obtained. This lays the foundation for the efficient separation and recovery of subsequent lithium salts, graphite, and copper foil, solving the technical problems of crude disassembly and inaccurate separation of target components in traditional recycling processes, resulting in low subsequent recovery efficiency and low purity of recovered products. Through static reaction and separation operations at room temperature and pressure, multiple effects can be achieved simultaneously: First, through liquid-phase reaction, lithium is efficiently leached and exists in the form of lithium hydroxide or lithium ethoxide, which is easy to purify into lithium carbonate. This process also achieves effective separation of lithium from other heavy metals, with high recovery purity and a short process, improving the economic value of lithium recovery and solving the technical problems of low lithium leaching rate, difficulty in separating lithium from other heavy metals, and cumbersome purification processes in traditional processes. Second, by evaporating and concentrating the separated lithium salt solution, lithium salts can be directly obtained.

[0033] Meanwhile, the overall operation process of this method has the following significant advantages: First, the entire process requires no high-temperature roasting (pyrometallurgical process) or high-temperature and high-pressure leaching; the reaction can be completed under normal or low-temperature conditions, significantly reducing energy consumption. Second, the complex multi-step unit operation of the traditional process of "crushing-sorting-acid leaching-lithium extraction-waste graphite treatment" is simplified to the core step of "reaction-separation." A single reaction can simultaneously achieve graphite desorption and purification, lithium leaching, and copper foil separation, greatly reducing equipment investment and operating costs. Third, the recovered intact and clean copper foil has high purity and can be directly sold or returned to the metallurgical process, giving it higher economic value compared to traditional copper recycling products.

[0034] In summary, this invention develops a lower-cost, lower-energy-consumption, green, environmentally friendly, and highly efficient method for recovering lithium salts from spent lithium-ion batteries in a state of charge. It can meet the industrial demand for large-scale, green recycling and solves the problems of high cost, high energy consumption, and poor environmental performance in existing spent lithium-ion battery recycling technologies, and has broad application prospects. Attached Figure Description

[0035] Figure 1 This is a flowchart of an experiment for recycling graphite, lithium carbonate, and copper foil. Figure 1 a) is a lithium-intercalated graphite anode; Figure 1 b) is the negative electrode after the reaction; Figure 1 c) Figure 1 f) is the product of Example 1; Figure 1 g)- Figure 1 j) is the product of Example 2; Figure 2The image shows the scanning electron microscope-energy dispersive spectroscopy (SEM-EDS) analysis of NE. Figure 3 The graphs are XRD patterns of graphite. a is a comparison of NE-EC, NE-WC and NE, b is the NE pattern, c is the NE-WC pattern, and d is the NE-EC pattern. In this graph, Intensity is the diffraction intensity, and Theda (degree) is the diffraction angle. Figure 4 The image shows a scanning electron microscope-energy dispersive spectroscopy (SEM-EDS) image, where... Figure 4 a) is a scanning electron microscope-energy dispersive spectroscopy (SEM-EDS) image of NE-EC. Figure 4 b) is the scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) image of NE-WC; Figure 5 The image shows the inductively coupled plasma optical emission spectra (ICP-OES) analysis results for NE, NE-WC, and NE-EC samples, where Mass fraction is the mass fraction. Figure 6 This is the X-ray diffraction (XRD) pattern of lithium carbonate (Li2CO3), where Intensity is the diffraction intensity and Theda (degree) is the diffraction angle. Figure 7 The images are scanning electron microscope-energy dispersive spectroscopy (SEM-EDS) images, where a) is the SEM-EDS image of NE-W-Li and b) is the SEM-EDS image of NE-E-Li. Figure 8 The image shows the inductively coupled plasma optical emission spectra (ICP-OES) analysis results of NE-W-Li and NE-E-Li samples, where Mass fraction is the mass fraction. Detailed Implementation

[0036] The present invention will be further described in detail below through embodiments, but in no way is the invention limited.

[0037] The reaction principle in this invention is as follows: High-energy-state lithium intercalation graphite reaction principle The lithium-intercalated graphite (LiC6) anode is dark gold in color, such as... Figure 1 As shown in a), the color of the graphite electrode indicates that the negative electrode exhibits a uniform physicochemical phenomenon in the high-energy state (lithium-intercalated graphite). To further observe the surface morphology characteristics of the lithium-intercalated graphite negative electrode, scanning electron microscopy was performed, and the SEM image was obtained, as shown in [image missing]. Figure 2 As shown, the lithium-intercalated graphite exhibits two shapes: an irregular spherical structure with an uneven surface and fine particles adhering to the surface, such as... Figure 2 As shown in b); flaky structure with surface cracks and some particles, such as Figure 2 As shown in a). From Figure 2 As can be seen from b), the irregular spheres mainly contain C and O elements. Figure 2 As can be seen from a), the sheet-like structure mainly contains C and a small amount of O. The sheet-like structure is lithium-intercalated graphite, and the irregular spherical shape may be a mixture of electrolyte decomposition and graphite.

[0038] LiC6 is composed of graphite layers with lithium atoms or Li atoms intercalated between them. + With interlayer electrons e - The composite material has extremely high energy and reactivity of interlayer electrons, making lithium-intercalated graphite a strong reducing agent. The essence of the reaction with both water and anhydrous ethanol is that the highly reactive lithium in the interlayer undergoes a redox reaction with the acidic hydrogen of the hydroxyl group (-OH) in the protic solvent (H-OH, CH3CH2-OH), generating hydrogen gas and converting lithium into the corresponding lithium salts (LiOH or CH3CH2OLi). These lithium salts further react with CO2 in the air, ultimately forming the thermodynamically more stable lithium carbonate (Li2CO3). The main difference between the two lies in the reaction rate and intensity, determined by the different proton-donating abilities and reaction kinetics of water and anhydrous ethanol.

[0039] The reaction of LiC6 with water is shown in formulas (I) and (II): 2LiC6+2H2O→2C6+2LiOH+H2↑ (I) 2LiOH+CO2→Li2CO3+H2O (II) In water molecules, the H-OH bond results in hydrogen atoms carrying a partially positive charge. The active lithium in LiC6 rapidly reacts with the H atoms released from water ionization. + Alternatively, it can react directly with water molecules, stripping protons to produce hydrogen gas and strong lithium oxide. Simultaneously, graphite reverts to its original layered structure by losing interlayer lithium. The resulting LiOH is a strong base that rapidly absorbs CO2 from the air, undergoing a neutralization reaction to produce white Li2CO3.

[0040] LiC6 reacts with anhydrous ethanol as shown in formulas (III) and (IV): 2LiC6+2CH3CH2OH→2C6+2CH3CH2OLi+H2↑ (III) 2CH3CH2OLi+CO2→Li2CO3+2CH3CH2OH (IV) Anhydrous ethanol reacts similarly to water, but the reaction is milder. Compared to OH bonds, breaking the C-C and CH bonds in anhydrous ethanol requires higher energy, and anhydrous ethanol is much weaker than water (the pKa of anhydrous ethanol is 15.9, while that of water is 15.7; pKa refers to the negative logarithm of the acid dissociation constant. Although their pKa values ​​are similar, the proton dissociation and reaction kinetics of anhydrous ethanol are slower). Therefore, the reaction rate and heat release of lithium-intercalated graphite with anhydrous ethanol are much lower than those with water. It typically manifests as slow bubbling (hydrogen gas) rather than a sudden and violent exothermic reaction. The resulting anhydrous lithium ethanol (CH3CH2OLi) is a strong base; like LiOH, it rapidly absorbs carbon dioxide from the air, eventually converting into lithium carbonate. Example 1

[0041] A method for recycling lithium salts from spent lithium-ion batteries in a state of charge includes the following steps: (1) Dismantling of waste lithium-ion batteries Before dismantling, the used lithium-ion batteries are fully charged. The entire dismantling process is carried out in a glove box filled with argon / nitrogen protective gas. Operators wear insulated protective equipment and use non-metallic tools. Under these conditions, the casing of the used lithium-ion batteries is pried open, the electrode components are removed, and the positive electrode, negative electrode (also known as the lithium-intercalated graphite negative electrode), separator, tabs, and casing are collected separately for later use.

[0042] (2) Graphite-lithium carbonate-copper foil recycling Take 3 g of lithium-intercalated graphite anode (NE) and place it in a beaker containing 30 ml of anhydrous ethanol (anhydrous ethanol is an organic solvent). Let it stand at room temperature for 15 min. After the lithium-intercalated graphite anode reacts with the organic solvent anhydrous ethanol, the solution is clear, as shown. Figure 1 As shown in c); the product graphite is on copper foil, as... Figure 1 As shown in d). The copper foil is on the negative electrode. After the reaction is complete, the negative electrode is separated from the solution, that is, the negative electrode is directly removed from the solution, resulting in the negative electrode and the lithium salt solution. The reaction between the lithium-intercalated graphite and anhydrous ethanol is mild, and the graphite does not fall off but covers the copper foil. Since the copper foil is on the negative electrode, the lithium salt solution and the graphite-loaded copper foil can be separated by directly removing the negative electrode.

[0043] The negative electrode sheet was dried in an 80℃ forced-air drying oven for 24 hours, and then the graphite and copper foil were peeled off to obtain high-purity graphite and copper foil. The high-purity graphite was named NE-EC. Figure 1 As shown in e); the lithium salt solution was dried in an 80°C oven for 24 hours to obtain lithium carbonate, named NE-E-Li. Lithium carbonate is a white powder, as shown in... Figure 1 As shown in f). Example 2

[0044] A method for recycling lithium salts from spent lithium-ion batteries in a state of charge includes the following steps: (1) Dismantling of waste lithium-ion batteries Before dismantling, the used lithium-ion batteries are fully charged. The entire dismantling process is carried out in a glove box filled with argon / nitrogen protective gas. Operators wear insulated protective equipment and use non-metallic tools. Under these conditions, the casing of the used lithium-ion batteries is pried open, the electrode components are removed, and the positive electrode, negative electrode (also known as the lithium-intercalated graphite negative electrode), separator, tabs, and casing are collected separately for later use.

[0045] (2) Graphite-lithium carbonate-copper foil recycling Take 3 g of lithium-intercalated graphite anode (NE) and place it in a beaker containing 30 ml of water (water is an inorganic solvent). Let it stand at room temperature for 60 min to react. After the lithium-intercalated graphite anode reacts in water, the solution becomes turbid, as shown below. Figure 1 As shown in g), at this point, the negative electrode material has been peeled off from the copper foil. The copper foil is removed, and a solution is obtained. The solution is filtered, and after filtration, the graphite remains on the filter paper, as shown in g). Figure 1 As shown in h), the filtrate (lithium salt solution containing lithium carbonate) and filter paper (graphite) were dried separately in a forced-air drying oven at 80°C for 48 h. High-purity graphite (named NE-WC) and lithium carbonate (named NE-W-Li) were obtained; the high-purity graphite... Figure 1 As shown in i), lithium carbonate is a dark green powder, such as Figure 1 As shown in j).

[0046] Detection and Analysis The graphite and lithium carbonate recovered in Examples 1 and 2 were analyzed.

[0047] 1. Characterization of high-purity graphite recovery XRD tests were performed on the negative electrode powder and the separated graphite, and the results are as follows: Figure 3 As shown, Figure 3 Figure 'a' is a comparison graph of NE-EC, NE-WC, and NE. Figure 3 b is the spectrum of NE. Figure 3 c represents the NE-WC spectrum. Figure 3 d represents the spectrum of NE-EC. Figure 3Figure a shows the diffraction peak patterns of NE-EC, NE-WC, and NE, and the diffraction peaks of the standard graphite card. The diffraction angles of NE-WC and NE (26.381°, 42.221°, 44.391°, 50.452°, 54.542°, 59.692°, 77.243°, 83.183°, 86.823°, 93.594°) are consistent with the standard card. However, NE-WC lacks the diffraction peaks at 86.823° (110) and 93.594° (112), indicating that NE- Compared with NE-EC, WC has higher crystallinity and a more complete three-dimensional ordered structure. NE-EC has a sharp (002) peak and a clear (004) peak. Its crystal structure is very perfect in three-dimensional space. In contrast, the graphite in NE-WC has poor symmetry of the (002) peak, a very weak (004) peak, and the (110) and (112) peaks have completely disappeared. There is a camel peak at 21.570°. During the reaction, amorphous carbon is generated and partially graphitized. This graphite belongs to a disordered layer structure, with only two-dimensional order and lacking three-dimensional order.

[0048] Two types of graphite obtained by reacting lithium-intercalated graphite with water and anhydrous ethanol, respectively, were characterized by SEM. The results are as follows: Figure 4 As shown, Figure 4 a) is a scanning electron microscope-energy dispersive spectroscopy (SEM-EDS) image of NE-EC. Figure 4 b) is the scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) image of NE-WC. Figure 4 From a), it is known that the graphite structure of NE-EC is plate-like with a smooth surface. Figure 4 As shown in b), the graphite structure of NE-WC is agglomerated and relatively fragmented. SEM-EDS analysis of both showed that NE-WC contains only carbon.

[0049] ICP-OES (inductively coupled plasma atomic emission spectrometry) was performed on Cu, Co, Al, S, P, and Li elements in NE, NE-WC, and NE-EC. The results are as follows: Figure 5 As shown, Li has the highest proportion in NE (non-neutral) samples, with a mass fraction of 5.25%, while it accounts for 1.425% in NE-EC (neutral-ecologically differentiated) samples. Li has a very low proportion in NE-WC (neutral-wheat-carbonate) samples, with a mass fraction of 0.095%. In summary, the mass fraction of Li in NE is 5.25%, in NE-WC it is 0.095%, and in NE-EC it is 1.425%. The mass fractions of Cu, Co, Al, S, and P in all three samples are close to 0. The Li leaching rate was calculated using ICP-OES results. Li is leached in the form of salt, specifically lithium carbonate, therefore the Li leaching rate is equal to the lithium carbonate leaching rate.

[0050] The formula for calculating the Li leaching rate in NE-WC is shown in equation (V): Li leaching rate = [(mass fraction of Li in NE - mass fraction of Li in NE-WC) / mass fraction of Li in NE] × 100% (V); Therefore, the Li leaching rate in NE-WC is: (5.25% - 0.095%) / 5.25% = 98.19%; The formula for calculating the Li leaching rate in NE-EC is shown in equation (VI): Li leaching rate = [(mass fraction of Li in NE - mass fraction of Li in NE-EC) / mass fraction of Li in NE] × 100% (VI); Therefore, the Li leaching rate in NE-EC is: (5.25% - 1.425%) / 5.25% = 72.86%.

[0051] 2. Characterization of recovered lithium salts X-ray diffraction experiments were performed on the lithium carbonate produced in the reaction to analyze the structure and composition of the product, such as... Figure 6 As shown, Figure 6 The following are the powder XRD diffraction patterns of lithium carbonate produced in Examples 1 and 2. Figure 6 In this context, NE-E-Li refers to the lithium carbonate recovered in Example 1, and NE-W-Li refers to the lithium carbonate recovered in Example 2. The results show that the diffraction peaks of both NE-E-Li and NE-W-Li correspond to the Li₂CO₃ standard card PDF#00-022-1141. However, NE-E-Li contains a small amount of LiOH, while NE-W-Li contains a very small amount of LiOH. This is because the reaction of lithium-intercalated graphite with water is vigorous, and the high solubility of CO₂ allows LiOH to react rapidly and completely with the dissolved CO₂ to form Li₂CO₃, with only a very small amount of converted LiOH and other impurities. In contrast, the reaction of anhydrous ethanol is relatively mild and slow, and the low solubility of CO₂ results in a slow and incomplete reaction with CO₂. Therefore, the Li₂CO₃ product contains a small amount of LiOH.

[0052] SEM tests were performed on the lithium carbonate generated in Examples 1 and 2, and the results are as follows: Figure 7 As shown, Figure 7 a) is the SEM-EDS plot of NE-W-Li. Figure 7 b) is the SEM-EDS plot of NE-E-Li. (From...) Figure 7 As shown in a), the Li₂CO₃ particles of NE-W-Li are irregularly aggregated in lumps, with the surface covered with small, angular fragments. SEM-EDS analysis indicates that it mainly contains O, with a small amount of C. Figure 7As shown in b), the Li2CO3 of NE-E-Li exhibits a slender needle-like structure with a disordered and interwoven distribution. Some crystals also show a star-shaped aggregate shape. The overall structure is dense and has obvious crystal morphology characteristics. Energy dispersive spectroscopy shows that the substance mainly contains C and O elements.

[0053] The lithium carbonate crystal structures of NE-E-Li and NE-W-Li are completely different. This is because they are related to the reaction rate, the polarity of the OH bond, the ability to donate protons, and the solvation ability. The water reaction is more vigorous than that of anhydrous ethanol. The OH bond of water is more polar and more easily breaks and releases protons. In addition, water is highly polar and can effectively solvate ions. The newly formed lithium carbonate crystal nuclei are surrounded by water molecules, the contact environment of each crystal face is relatively uniform, the number of crystal nuclei is large, and they grow isotropically.

[0054] ICP-OES (inductively coupled plasma atomic emission spectrometry) was performed on Cu, Co, Al, S, P, and Li elements in NE-W-Li and NE-E-Li, and the results are as follows: Figure 8 As shown. The mass fractions of Cu, Co, Al, S, and P in both samples are close to 0, belonging to trace impurities. Converting the lithium content in the ICP-OES results to the purity of Li₂CO₃, theoretically, the lithium content in lithium carbonate (Li₂CO₃) is approximately 18.79% (…). The lithium content in NE-W-Li is 16.94%, and the lithium content in NE-E-Li is 1.44%. The theoretical purity of lithium carbonate is calculated according to formula (VII). ): (VII) Therefore, the theoretical purity of lithium carbonate in NE-W-Li is The theoretical purity of lithium carbonate in NE-E-Li is: .

[0055] In summary, the method for recovering lithium salts from spent lithium-ion batteries in a state of charge provided by this invention has the following advantages: Compared with traditional pyrometallurgical and hydrometallurgical methods, this invention offers several advantages. First, it achieves simultaneous high-value recovery of graphite, lithium, and copper foil, rather than focusing solely on the metals. This method enables the full-component, closed-loop, and high-value recovery of anode materials, completely overcoming the limitations of traditional recycling models. Second, the reaction system is more mild and environmentally friendly, avoiding the use of strong acids, strong alkalis, or toxic organic solvents. It innovatively uses anhydrous ethanol and water as the reaction medium. This system selectively extracts lithium while preserving the layered structure of graphite, minimizing structural damage. Furthermore, the anhydrous ethanol reaction process generates no hydrogen, ensuring excellent intrinsic safety. It produces no toxic waste gas, resulting in low emissions and a simple treatment process, perfectly aligning with the green and environmentally friendly recycling concept. Third, the recovered graphite exhibits minimal structural damage. Fourth, the sale of the recovered high-purity recycled graphite, lithium salts, and copper foil generates significant economic benefits, with recycled graphite providing a new, high-value-added source of profit.

[0056] This invention provides a method for recovering lithium salts from spent lithium-ion batteries in a state of charge. By disassembling the spent lithium-ion batteries under specific states of charge (including fully charged state), the core recovery target—lithium-intercalated graphite anode—can be accurately obtained. This lays the foundation for the efficient separation and recovery of subsequent lithium salts, graphite, and copper foil, solving the technical problems of crude disassembly and inaccurate separation of target components in traditional recycling processes, resulting in low subsequent recovery efficiency and low purity of recovered products. Through static reaction and separation operations at room temperature and pressure, multiple effects can be achieved simultaneously: First, through liquid-phase reaction, lithium is efficiently leached and exists in the form of lithium hydroxide or lithium ethoxide, which is easy to purify into lithium carbonate. This process also achieves effective separation of lithium from other heavy metals, with high recovery purity and a short process, improving the economic value of lithium recovery and solving the technical problems of low lithium leaching rate, difficulty in separating lithium from other heavy metals, and cumbersome purification processes in traditional processes. Second, by evaporating and concentrating the separated lithium salt solution, lithium salts can be directly obtained.

[0057] Meanwhile, the overall operation process of this method has the following significant advantages: First, the entire process requires no high-temperature roasting (pyrometallurgical process) or high-temperature and high-pressure leaching; the reaction can be completed under normal or low-temperature conditions, significantly reducing energy consumption. Second, the complex multi-step unit operation of the traditional process of "crushing-sorting-acid leaching-lithium extraction-waste graphite treatment" is simplified to the core step of "reaction-separation." A single reaction can simultaneously achieve graphite desorption and purification, lithium leaching, and copper foil separation, greatly reducing equipment investment and operating costs. Third, the recovered intact and clean copper foil has high purity and can be directly sold or returned to the metallurgical process, giving it higher economic value compared to traditional copper recycling products.

[0058] In summary, this invention develops a lower-cost, lower-energy-consumption, green, environmentally friendly, and highly efficient method for recovering lithium salts from spent lithium-ion batteries in a state of charge. It can meet the industrial demand for large-scale, green recycling and solves the problems of high cost, high energy consumption, and poor environmental performance in existing spent lithium-ion battery recycling technologies, and has broad application prospects.

Claims

1. A method for recovering lithium salts from spent lithium-ion batteries in a state of charge, characterized in that, Includes the following steps: S1. Disassemble the charged waste lithium-ion batteries to obtain lithium-intercalated graphite anodes; S2. Place the lithium-intercalated graphite anode in a solvent, allow it to stand and react, then separate to obtain a lithium salt solution; S3. Evaporate and concentrate the lithium salt solution to obtain lithium salt.

2. The method according to claim 1, characterized in that, The ratio of the lithium-intercalated graphite anode to the solvent is 3 g: 30 mL; And / or, the solvent is selected from inorganic solvents or organic solvents.

3. The method according to claim 1, characterized in that, In step S1, the disassembly is carried out in an inert gas atmosphere, wherein the inert gas is argon or nitrogen. And / or, in S2, the standing reaction time is 15 min-60 min, and the temperature is room temperature.

4. The method according to claim 1, characterized in that, When the solvent is selected from organic solvents, S2 and S3 include: The lithium-intercalated graphite anode was placed in an organic solvent, allowed to stand and react, and then separated to obtain the anode sheet and the lithium salt solution. The lithium salt solution was concentrated by evaporation to obtain lithium salt.

5. The method according to claim 4, characterized in that, The recycling method further includes: S4. Dry the negative electrode sheet, and then peel off the graphite and copper foil from the negative electrode sheet to obtain graphite and copper foil.

6. The method according to claim 5, characterized in that, The drying step includes: placing the negative electrode sheet in a forced-air drying oven at 80°C and drying it for 24 hours; The evaporation and concentration steps include: placing the lithium salt solution in a forced-air drying oven at 80°C and drying it for 24 hours.

7. The method according to claim 1, characterized in that, When an inorganic solvent is selected as the solvent, S2 and S3 include: The lithium-intercalated graphite anode was placed in an inorganic solvent, allowed to stand and react, and the copper foil was removed to obtain a solution. Filtering the solution yields a lithium salt solution and crude graphite product; The lithium salt solution was concentrated by evaporation to obtain lithium salt.

8. The method according to claim 7, characterized in that, The recycling method further includes: S4. Dry the crude graphite product to obtain graphite.

9. The method according to claim 8, characterized in that, The drying step includes: placing the filter residue in a forced-air drying oven at 80°C and drying it for 48 hours; The evaporation and concentration steps include: drying the lithium salt solution in a forced-air drying oven at 80°C for 48 hours.

10. The lithium salt recovered by the method according to any one of claims 1 to 8, characterized in that, The lithium salt is lithium carbonate.

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