Method of recycling active metal of lithium secondary battery

Abstract

In a method for recovering active metals from a lithium secondary battery, positive active material particles containing a lithium-transition metal oxide are prepared. The positive active material particles are subjected to reduction treatment. The reduced positive active material particles are subjected to ultrasonically dispersed hydration. The hydrated transition metal slurry is recovered. The recovery rate of lithium and transition metals can be increased by resolving aggregation using ultrasonic dispersion.

Description

Technology Field

[0001] The present invention relates to a method for recovering an active metal from a lithium secondary battery. More specifically, it relates to a method for recovering an active metal from the positive electrode of a lithium secondary battery. Background Technology

[0002] Recently, rechargeable batteries are being widely applied and developed as power sources for portable electronic communication devices such as camcorders, mobile phones, and laptop PCs, as well as for vehicles such as hybrid and electric cars. Among rechargeable batteries, lithium-ion batteries have been actively developed and applied due to their high operating voltage and energy density per unit weight, as well as their advantages in charging speed and weight reduction.

[0003] A lithium metal oxide can be used as an active material for the positive electrode of the above-mentioned lithium secondary battery. The above-mentioned lithium metal oxide may additionally contain transition metals such as nickel, cobalt, and manganese.

[0004] As the aforementioned high-cost, valuable metals are used in the active materials for the cathode, more than 20% of the manufacturing cost is spent on manufacturing the cathode material. In addition, as environmental protection issues have recently come to the forefront, research on recycling methods for active materials for the cathode is being conducted.

[0005] For example, lithium and transition metals can be separated and recovered by reducing spent cathode active material. However, if the reduction reaction conditions are not properly controlled, clumping or aggregation of active material particles may occur. In this case, the proportion of unrecovered lithium and transition metals may increase, and the purity of the recovered active metals may also decrease.

[0006] For example, Korean Registered Patent No. 10-0709268 discloses a device and method for recycling waste manganese batteries and alkaline batteries, but it fails to present a dry-based method for regenerating valuable metals with high selectivity and high yield. Prior art literature

[0007] Korean Registered Patent No. 10-0709268 The problem to be solved

[0008] One objective of the present invention is to provide a method for recovering active metals of lithium secondary batteries with high efficiency and high purity. means of solving the problem

[0009] In a method for recovering an active metal of a lithium secondary battery according to exemplary embodiments, positive active material particles comprising a lithium-transition metal oxide are prepared. The positive active material particles are subjected to reduction treatment. The reduced positive active material particles are subjected to ultrasonically dispersed hydration. The hydrated transition metal slurry is recovered.

[0010] In some embodiments, lithium precursor particles, transition metal oxide particles, and transition metal particles may be formed from the positive electrode active material particles by the reduction treatment.

[0011] In some embodiments, aggregates of the lithium precursor particles, the transition metal oxide particles, and the transition metal particles may be formed by the reduction treatment.

[0012] In some embodiments, the aggregate may be decomposed through the ultrasonic dispersion hydration.

[0013] In some embodiments, the aggregate can be broken down into particles with a particle size of 300 μm or less through the ultrasonic dispersion hydration.

[0014] In some embodiments, the ultrasonic dispersion hydration may include a solid-liquid two-phase process.

[0015] In some embodiments, ultrasonic waves with a power of 50 to 110 W can be applied in the ultrasonic dispersion hydration.

[0016] In some embodiments, ultrasonic waves with a power of 2.5 to 5.5 W / g per 1 g of aggregate can be applied during the ultrasonic dispersion hydration.

[0017] In some embodiments, ultrasonic waves with a power of 0.6 to 1.4 W / g per 1g of the transition metal slurry recovered from the ultrasonic dispersion hydration may be applied.

[0018] In some embodiments, the reduction treatment of the anode active material particles may be performed in a fluidized bed reactor using a reducing gas.

[0019] In some embodiments, the recovered transition metal slurry can be rehydrated.

[0020] In some embodiments, the positive active material particles may be heat-treated at a temperature of 500°C or lower before reduction treatment of the positive active material particles. Effects of the invention

[0021] According to the exemplary embodiments described above, lithium precursors can be recovered, for example, through a dry-based process utilizing a dry reduction process from waste cathode active material. Thus, lithium precursors can be obtained with high purity without complex leaching processes or additional processes resulting from wet-based acid solution processes.

[0022] According to exemplary embodiments, aggregation can be resolved through ultrasonic dispersion for aggregates generated due to excessive dry reduction process or excessive increase in the heat of reduction reaction. Accordingly, the recovery rate of the slurry containing transition metals in the hydration process can be improved and the amount of unrecovered aggregates can be reduced.

[0023] In some embodiments, the ultrasonic dispersion may proceed in a two-phase state of solid and liquid to improve the slurry recovery rate. Brief explanation of the drawing

[0024] FIG. 1 is a schematic flowchart illustrating a method for recovering active metal from a lithium secondary battery according to exemplary embodiments. FIGS. 2 to 4 are schematic diagrams showing particle flow and phase change in the reduction and hydration processes. Specific details for implementing the invention

[0025] Embodiments of the present invention provide a method for recovering active metal of high purity and high yield from a lithium secondary battery through a reduction reaction.

[0026] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. However, this is merely illustrative and the present invention is not limited to the specific embodiments described illustratively.

[0027] As used in this specification, the term "precursor" is used to collectively refer to a compound containing a specific metal to provide the specific metal included in the electrode active material.

[0028] FIG. 1 is a schematic flowchart illustrating a method for recovering active metal from a lithium secondary battery according to exemplary embodiments. FIGS. 2 to 4 are schematic diagrams showing particle flow and phase change in the reduction process and the hydration process.

[0029] Referring to Fig. 1, for example, in step S10, a positive active material mixture can be prepared.

[0030] According to exemplary embodiments, active material particles (e.g., waste cathode active material particles) can be prepared from a waste cathode of a lithium secondary battery.

[0031] The above lithium secondary battery may include an electrode assembly comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode. The positive electrode and the negative electrode may each include a positive active material layer and a negative active material layer coated on a positive current collector and a negative current collector, respectively.

[0032] For example, the positive active material included in the positive active material layer may include an oxide containing lithium and a transition metal.

[0033] In some embodiments, the positive active material may include a compound represented by the following chemical formula 1.

[0034] [Chemical Formula 1]

[0035] Li x M1 a M2 b M3 c O y

[0036] In Chemical Formula 1, M1, M2 and M3 may be transition metals selected from Ni, Co, Mn, Na, Mg, Ca, Ti, V, Cr, Cu, Zn, Ge, Sr, Ag, Ba, Zr, Nb, Mo, Al, Ga, or B. In Chemical Formula 1, 0 <x≤1.1, 2≤y≤2.02, 0<a<1, 0<b<1, 0<c<1, 0<a+b+c≤1일 수 있다.

[0037] In some embodiments, the positive electrode active material may be an NCM-based lithium oxide containing nickel, cobalt, and manganese.

[0038] The waste cathode can be recovered by separating the cathode from the above-described waste lithium secondary battery. As described above, the waste cathode comprises a cathode current collector (e.g., aluminum (Al)) and a cathode active material layer, and the cathode active material layer may include a conductive material and a binder together with the cathode active material described above.

[0039] The conductive material may include, for example, carbon-based materials such as graphite, carbon black, graphene, carbon nanotubes, etc. The binder may include, for example, resin materials such as vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidenefluoride (PVDF), polyacrylonitrile, and polymethylmethacrylate.

[0040] In some embodiments, the positive active material layer can be peeled off from the positive current collector, and the separated positive active material layer can be crushed to produce positive active material particles. Accordingly, the positive active material particles can be manufactured in powder form and, for example, collected in the form of black powder.

[0041] The above-described positive active material particles comprise a lithium-transition metal oxide powder as described above, and may include, for example, an NCM-based lithium oxide powder (e.g., Li(NCM)O2). In this case, M1 in Chemical Formula 1, M2 and M3 can be Ni, Co, and Mn, respectively.

[0042] The term "anode active material particle" as used in this application may refer to a raw material introduced into the reducing reaction treatment described below after the anode current collector has been substantially removed from the waste anode. In one embodiment, the anode active material particle may include the NCM-based lithium oxide. In one embodiment, the anode active material particle may partially include a component derived from the binder or the conductive material.

[0043] In some embodiments, the average particle size (D50) (average particle size in the volume cumulative distribution) of the positive active material particles may be 5 to 100 μm. Within this range, a reducing reaction can be easily performed through the fluidized bed reactor described below.

[0044] For example, in the S20 process, the positive active material particles can be reduced in a reducing reactor (100).

[0045] Referring to FIGS. 2 and 3, the above-described positive active material particles (50) can be introduced into a reducing reactor (100) (e.g., step S21).

[0046] In some embodiments, the positive active material particles (50) may be heat-treated before reduction treatment. By the heat treatment, impurities such as the conductive material and binder contained in the positive active material particles (50) can be removed or reduced, thereby allowing the lithium-transition metal oxide to be reduced to a high purity.

[0047] The heat treatment temperature can be performed, for example, at about 500°C or lower, about 100 to 500°C in one embodiment, preferably about 350 to 450°C. Within this range, the impurities can be substantially removed while preventing the decomposition and damage of the lithium-transition metal oxide.

[0048] In one embodiment, the heat treatment may be performed within a reducing reactor (100). In this case, a carrier gas, such as nitrogen (N2), helium (He), or argon (Ar), is injected through a gas injection unit (110) located at the bottom of the reducing reactor (100), and fluidization heat treatment may be performed within the reducing reactor (100).

[0049] In one embodiment, the positive active material particles (50) may be introduced into a reducing reactor (100) after heat treatment.

[0050] For example, the positive active material particles (50) can be reduced in step S23. According to exemplary embodiments, the reducing reactor (100) may be provided as a fluidized bed reactor. By injecting a reducing gas from the bottom of the reducing reactor (100) through the gas injection unit (110), a fluidized bed formed by the positive active material particles (50) within the reducing reactor (100) can be formed and a reduction reaction can be induced.

[0051] The reducing gas may include hydrogen (H2). The reducing gas may further include a carrier gas such as nitrogen, helium, or argon (Ar).

[0052] As the reducing gas is supplied from the bottom of the reducing reactor (100) and comes into contact with the positive active material particles (50), the positive active material particles (50) can move to the top of the reducing reactor (100) or remain in the reducing reactor (100) and react with the reducing reaction gas.

[0053] As described above, the reducing gas can be injected to form a fluidized bed. As the positive active material particles (50) come into contact with the reducing gas within the fluidized bed and repeatedly rise, stay, and fall, the reaction contact time increases and the dispersion of the particles can be enhanced.

[0054] In addition, as the reducing gas is supplied from the bottom of the reducing reactor (100) and comes into contact with the positive active material particles (50), the positive active material particles (50) can move to the top of the reducing reactor (100), thereby expanding the reaction area.

[0055] However, the concept of the present invention is not necessarily limited to a fluidized bed reaction. For example, a stationary reaction may be performed in which a mixture of anode active materials is pre-loaded into a batch reactor or a tubular reactor and then a reducing reaction gas is supplied.

[0056] In some embodiments, a dispersion plate (120) may be disposed at the bottom of the reducing reactor (100). The rising and ejection of the reducing gas may be facilitated through injection holes included in the dispersion plate (120).

[0057] As the reduction reaction is initiated, lithium precursor particles (60) can be generated from the positive active material particles (50). For example, as the reduction process proceeds, the Li(NCM)O2 crystal structure collapses, causing Li to detach from the crystal structure and be reduced in the form of lithium hydroxide (LiOH), lithium oxide (e.g., Li2O) and / or lithium carbonate (Li2CO3). In a preferred embodiment, the lithium precursor particles (50) may include lithium hydroxide (LiOH).

[0058] Meanwhile, transition metals can be reduced from the above crystal structure to produce transition metal oxide particles (70). For example, the transition metal oxide particles (70) may include transition metal oxides such as NiO and CoO.

[0059] Referring to FIG. 3, for example, in step S25, as the reduction reaction proceeds further, additional transition metal particles (75) may be generated. For example, the transition metal particles (75) may include nickel (Ni) or cobalt (Co). As the transition metal particles (75) are formed, aggregation or gathering of the particles may be initiated as the heat of reaction increases.

[0060] If the reduction reaction proceeds excessively, for example at step S27, clumping or sintering between particles may occur, and aggregates (80) may be formed.

[0061] For example, the reduction reaction temperature can be controlled to 500°C or lower to prevent excessive reduction. However, the temperature inside the reducing reactor (100) may increase to more than 500°C due to the reaction heat generated during the reduction reaction, and accordingly, the transition metal oxide particles (70) or the positive active material particles (50) may be excessively reduced to produce transition metal particles (75).

[0062] Additionally, aggregates (80) are formed by metallic bonding or sintering between transition metal particles (75), and lithium precursor particles (60) and transition metal oxide particles (70) may be attached and included within the aggregates (80).

[0063] Referring to FIGS. 1 and 4, particles generated by a reduction reaction can be hydrated with ultrasonic dispersion (e.g., process S30).

[0064] For example, water can be supplied to the aggregates (80) generated by the reduction treatment described above to hydrate them. The hydration can be performed together with ultrasonic dispersion. The hydration can be performed by introducing water into a reducing reactor (100), or by introducing the aggregates (80) together with water into a separate storage container.

[0065] For example, after immersing the ultrasonic probe (150) in the aqueous solution into which the aggregates (80) are introduced, power can be applied through the power supply unit (P).

[0066] For example, as indicated in step S34, through ultrasonic dispersion hydration, the lithium precursor particles (50) can be substantially dissolved in an aqueous solution while the sintering of the aggregate (80) is eliminated. Additionally, the transition metal oxide particles (70) and transition metal particles (75) contained in the aggregate (80) can be individually separated and dispersed in a solid state within the aqueous solution.

[0067] As described above, by performing ultrasonic dispersion together with the hydration of lithium precursor particles (50) to decompose aggregates (80), the recovery rate of transition metals can be significantly increased.

[0068] Referring again to FIG. 1, for example, a transition metal-containing slurry can be recovered through a filtration process (e.g., process S40).

[0069] As described above, the aggregate (80) can be substantially broken down into individual particles or microparticles through an ultrasonic dispersion process. Thus, the fraction remaining as aggregate (80) and not recovered can be substantially removed, and the transition metal components can be substantially and completely recovered into the slurry.

[0070] In some embodiments, aggregates having a particle size of 1000 μm or more can be substantially decomposed and removed through the ultrasonic dispersion process. For example, through the ultrasonic dispersion process, aggregates (80) can all be decomposed into particles having a particle size of 300 μm or less.

[0071] The transition metal components contained in the above transition metal slurry can be acid-treated and recovered as transition metal precursors. For example, NiSO4, CoSO4, and MnSO4 can be recovered as transition metal precursors, respectively, using a sulfuric acid solution.

[0072] The lithium precursor particles (50) dissolved in the aqueous solution can be recovered as a lithium precursor in the form of lithium hydroxide, for example, through a crystallization process. In some embodiments, a rehydration process (e.g., a washing process) may be performed on the transition metal slurry. Through the rehydration, the lithium components remaining in the transition metal slurry may be dissolved again to increase the lithium precursor recovery rate.

[0073] As described above, according to exemplary embodiments, the hydration and dispersion process can be carried out as a solid-liquid two-phase process utilizing ultrasound. Accordingly, the time for resolving aggregation is shortened, and a transition metal recovery rate of substantially close to 100% can be secured.

[0074] In a comparative example, water is introduced into a reducing reactor (100) to decompose the aggregate (80), and then a carrier gas is supplied through a gas injection unit (110) to perform fluidization hydration.

[0075] In this case, as the dispersion process is carried out as a three-phase process of solid-liquid-gas, the time required to resolve aggregation increases excessively, and the recovery rate of lithium and transition metals may also be significantly reduced.

[0076] However, according to the exemplary embodiments described above, by using a two-phase dispersion process utilizing ultrasound, the time for re-aggregation of particles is significantly shortened, thereby preventing re-aggregation and significantly increasing the recovery rate of lithium and transition metals.

[0077] In some embodiments, the power (W) applied during the ultrasonic dispersion may be 50 W or more. In this case, the dispersion time is shortened and substantially improved transition metal and lithium recovery rates can be obtained.

[0078] Preferably, the power (W) applied during the ultrasonic dispersion may be 50 to 110 W. For example, if the applied power exceeds 110 W, an additional increase in recovery rate is not obtained, and it may not be economically desirable.

[0079] In some embodiments, the power applied per 1g of aggregate (80) may be 2.5W / g or more, preferably 2.5 to 5.5W / g.

[0080] In some embodiments, the power applied per 1 g of recovered transition metal slurry may be 0.6 W / g or more, preferably 0.6 to 1.4 W / g or more.

[0081] Specific experimental examples are presented below to aid in understanding the present invention; however, these are merely illustrative of the invention and do not limit the appended claims. It is obvious to those skilled in the art that various changes and modifications to the embodiments are possible within the scope and spirit of the invention, and that such variations and modifications fall within the scope of the appended claims.

[0082] Examples

[0083] 1 kg of cathode material separated from spent lithium secondary batteries was heat-treated at 450°C for 1 hour. The heat-treated cathode material was cut into small units and ground through milling to obtain a Li-Ni-Co-Mn oxide cathode active material sample. 200 g of the cathode active material sample was introduced into a fluidized bed reactor, and while maintaining the internal temperature of the reactor at 480°C, 100% nitrogen gas was injected from the bottom of the reactor at a flow rate of 5.5 L / min to perform fluidized heat treatment for 3 hours.

[0084] After the heat treatment process, the reactor temperature was lowered to 460°C, and a 20 vol% hydrogen / 80 vol% nitrogen mixed gas was injected from the bottom of the reactor at a flow rate of 5.5 L / min for 4 hours to carry out the reduction reaction. During this time, the internal temperature of the fluidized bed reactor was maintained at 460°C. After the reduction reaction, the reactor temperature was lowered to 25°C, and 20 g of aggregate was collected.

[0085] 60g of water was added to 20g of the above aggregate, and after immersing the ultrasonic probe in the aqueous solution, the aggregation dissolution process was performed under the power and dispersion time conditions listed in Table 1.

[0086] Comparative example

[0087] 60g of water was added to 20g of aggregate collected by carrying out a reduction reaction in the same way as in the example, and dispersion was performed for 300 minutes while supplying nitrogen (N2) gas into the aqueous solution instead of ultrasonic dispersion.

[0088] After collecting the transition metal-containing slurry through the dispersions obtained from the examples and comparative examples, a washing process was performed. Subsequently, the slurry recovery rate and lithium recovery rate were measured as follows.

[0089] 1) Measurement of slurry recovery rate

[0090] The weight of the aggregates generated after the reduction process (A) and the weight of the solid aggregates remaining inside the reactor after the dispersion process without being dispersed into a slurry (B) were measured, and the slurry recovery rate (= (1-B / A)*100) (%) was calculated.

[0091] 2) Measurement of lithium recovery rate

[0092] Water was added in an amount equal to 19 times (by weight) to the dispersion in a slurry state and stirred, and then the lithium precursor in which lithium hydroxide and lithium carbonate were dissolved in water was recovered. The lithium recovery rate (%) was calculated by measuring the weight of lithium dissolved in water relative to the weight of lithium in the initial cathode active material sample.

[0093] The evaluation results are listed together in Table 1 below.

[0094] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative example Authorized power (W) 5 20 50 50 110 110 - Authorization time (min) 30 30 5 15 3 5 Slurry recovery rate (%) 25 37 82 100 86 100 75 Lithium recovery rate (%) 20 30 72 95 76 95 64

[0095] Meanwhile, in the examples, power was calculated based on 1g of recovered slurry and 1g of aggregate, and is listed in Table 2 below.

[0096] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Power (W / g) based on 1g of slurry 0.06 0.25 0.63 0.63 1.38 1.38 Power (W / g) based on 1g of aggregate 0.25 1.00 2.50 2.50 5.50 5.50

[0097] Referring to Tables 1 and 2, in the examples where ultrasonic dispersion hydration was performed, an improved recovery rate was secured at a shortened dispersion time compared to the comparative example where a three-phase dispersion process was performed overall.

[0098] For example, in Examples 3 to 6, when ultrasonic dispersion was performed using a power supply of 50W or more, a slurry recovery rate of 80% or more and a lithium recovery rate of 70% or more were secured. Explanation of the symbols

[0099] 50: Cathode active material particles 60: Lithium precursor particles 70: Transition metal oxide particles 75: Transition metal particles 80: Aggregate 100: Reducing reactor 110: Gas injection section 120: Dispersion plate

Claims

Claim 1 A method for recovering an active metal of a lithium secondary battery, comprising the steps of: preparing positive active material particles containing a lithium-transition metal oxide; reducing the positive active material particles; ultrasonically dispersing and hydrating the reduced positive active material particles; and recovering a hydrated transition metal slurry, wherein the reduction treatment step comprises forming lithium precursor particles, transition metal oxide particles, and transition metal particles from the positive active material particles, wherein aggregates of the lithium precursor particles, transition metal oxide particles, and transition metal particles are formed in the reduction treatment step, and the ultrasonically dispersing and hydrating step comprises decomposing the aggregates, and wherein the reduction treatment of the positive active material particles is performed in a fluidized bed reactor using a reducing gas. Claim 2 delete Claim 3 delete Claim 4 delete Claim 5 A method for recovering active metal of a lithium secondary battery according to claim 1, wherein the aggregate is decomposed into particles with a particle size of 300 μm or less through the step of ultrasonically dispersing and hydrating. Claim 6 A method for recovering active metal of a lithium secondary battery according to claim 1, wherein the step of ultrasonically dispersing and hydrating comprises a two-phase process of solid-liquid phases. Claim 7 A method for recovering active metal of a lithium secondary battery according to claim 1, wherein the step of ultrasonically dispersing and hydrating comprises applying ultrasonic waves with a power of 50 to 110 W. Claim 8 A method for recovering active metal of a lithium secondary battery according to claim 1, wherein the step of ultrasonically dispersing and hydrating comprises applying ultrasound with a power of 2.5 to 5.5 W / g per 1 g of aggregate. Claim 9 A method for recovering an active metal of a lithium secondary battery according to claim 1, wherein the step of ultrasonically dispersing and hydrating comprises applying ultrasonic waves with a power of 0.6 to 1.4 W / g per 1g of the recovered transition metal slurry. Claim 10 delete Claim 11 A method for recovering an active metal of a lithium secondary battery according to claim 1, further comprising the step of rehydrating the recovered transition metal slurry. Claim 12 A method for recovering active metal of a lithium secondary battery according to claim 1, further comprising the step of heat-treating the positive active material particles at a temperature of 500°C or lower prior to the step of reducing the positive active material particles.

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