JP7472474B2 - Method and device for dissolving metals from lithium-ion battery positive electrode material - Google Patents

Description

The present invention relates to a method and device for dissolving metals contained in positive electrode materials for lithium-ion batteries.

Lithium-ion batteries are widely used in smartphones, electric vehicles, etc., and the global market for small consumer batteries (cylindrical, rectangular, laminated), EVs, ESS, UPS, and BTS is expected to reach 4 trillion yen in 2021.

Positive electrode materials used in lithium-ion batteries include cobalt-based (lithium cobalt oxide ( _LiCoO2 )), nickel-based (lithium nickel oxide ( _LiNiO2 )), manganese-based (lithium manganese oxide ( _LiMn2O4 )), iron phosphate-based ( _lithium iron phosphate ( _LiFePO4 )), and ternary _materials such as _NCA ( _{LiNi0.8Co0.15Al0.05O2} ) and NMC (LiNi1 _{/ 3Mn1} / _{3Co1 /3O2 )} .

As such, the cathode material of lithium-ion batteries contains rare metals such as lithium, cobalt, nickel, and manganese. These rare metals are only produced in a limited number of countries, and reserves are small, raising concerns about price hikes and depletion. To ensure a stable supply of rare metals, there is an urgent need to develop recycling technology for lithium-ion batteries.

There are two methods for recycling lithium-ion batteries: the dry method, in which the batteries are melted and then the metal components such as Co, Ni, and Cu are recovered as metals through magnetic separation or refining, and the wet method, in which the batteries are disassembled and separated into their individual components, and then the positive electrode material is treated with chemicals to dissolve and leach the metal components, which are then recovered through extraction or electrolysis.

When recovering metals from materials that contain metals or metal compounds, it is common to add acid and heat the material. In this case, to increase the efficiency of metal recovery, it is necessary to dissolve as much metal as possible in a short period of time. However, the metal components in the positive electrode material of lithium-ion batteries are metal oxides, which are difficult to ionize and do not easily dissolve in an acid solution, making it difficult to recover metals using wet methods.

As a way to recover metals from the positive electrode material of lithium-ion batteries using a wet method, for example, Patent Document 1 discloses a method in which, when treating scrap of Li, Co, Ni, and Mn oxides with sulfuric acid, a transition metal compound (manganese sulfate) that is less noble than the metal to be leached is added to insolubilize the Mn, dissolving 90% by weight or more of the Li, Ni, and Co.

Patent Document 2 discloses a method for efficiently recovering metals from scrap, in which scrap of Li, Co, Ni, and Mn oxides is treated with 0.3 equivalents of sulfuric acid to dissolve the Li, then filtered to recover the Li from the filtrate, and 0.7 equivalents of sulfuric acid is added to the filtration residue to dissolve the Co and Ni.

However, the method of Patent Document 1 requires the separate addition of a metal compound such as manganese sulfate, which leads to an increase in the amount of metal to be recovered, and therefore cannot be said to be a simple method for dissolving metals. Furthermore, the method of Patent Document 2 requires the treatment with sulfuric acid to be carried out in two stages, which makes the operation complicated, and therefore cannot be said to be a simple method for dissolving metals.

JP 2015-178642 A JP 2016-69706 A

The present invention was made in consideration of the above problems, and aims to provide a method and apparatus for efficiently and easily dissolving metals from lithium ion battery positive electrode materials into an acidic solution.

As a result of intensive research into solving the above problems, the inventors discovered that by irradiating a positive electrode material with microwaves in the presence of an acidic solution and heating it, the amount of metal leaching into the acidic solution increases, which led to the completion of the present invention.

In other words, the present invention is as follows.

(1) When dissolving the metal contained in the positive electrode material of a lithium-ion battery in an acidic solution,
As the acidic solution, a 1 to 3 mol/L aqueous hydrochloric acid solution is used,
The dissolving method is characterized in that the acidic solution is heated by irradiating it with microwaves while being in contact with the cathode material , thereby maintaining the liquid temperature during contact in the range of 60 to 80°C .
(2) The method for dissolving according to (1) above, wherein the positive electrode material is a positive electrode material containing one or more metals selected from the group consisting of cobalt, manganese, and nickel, and lithium metal.

(3) A dissolving apparatus for dissolving a metal contained in a positive electrode material of a lithium ion battery in an acidic solution, comprising:
A storage tank for storing the acidic solution;
a cathode material filling device for filling the cathode material powder;
a microwave reaction device that irradiates the cathode material filling device with microwaves in the presence of the acidic solution to heat the acidic solution ;
a liquid circulation system that circulates the acidic solution in the storage tank to the cathode material filling device;
Equipped with
The microwave reactor is equipped with a temperature control panel with a PID control function, and the output of the microwave reactor is PID controlled,
A dissolution apparatus characterized in that it does not have a heating tank for heating the acidic solution.

According to the present invention, by irradiating the positive electrode material with microwaves in the presence of an acidic solution, heating proceeds due to dielectric loss, etc., and it is possible to leach cobalt, manganese, and nickel metals in larger amounts (approximately 2 to 5 times the amount) than when heated with a heater. This makes it possible to recover rare metals at low cost.

FIG. 1 is a schematic diagram illustrating an embodiment of a dissolution apparatus of the present invention. FIG. 13 is a diagram showing test results of a positive electrode material (LiCoO ₂ ). FIG. 1 is a diagram showing test results of a positive electrode material (LiMnO ₄ ). FIG. 13 is a diagram showing test results of a positive electrode material (LiNiO ₂ ).

[Dissolution method]
The dissolution method of the present invention is a method for dissolving metals contained in a positive electrode material obtained by dismantling a lithium-ion battery positive electrode material in an acidic solution, and is characterized in that the positive electrode material is heated by irradiating it with microwaves in the presence of the acidic solution.

The lithium ion battery positive electrode material may be any known positive electrode material without limitation. Specifically, cobalt-based positive electrode materials such as lithium cobalt oxide (LiCoO ₂ ), nickel-based positive electrode materials such as lithium nickel oxide (LiNiO ₂ ), manganese-based positive electrode materials such as lithium manganese oxide (LiMn ₂ O ₄ ), iron-based positive electrode materials such as lithium iron phosphate (LiFePO ₄ ), NCA-based positive electrode materials such as LiNi _0.8 Co _0.15 Al _0.05 O ₂ , and NMC-based positive electrode materials such as LiNi _1/3 Mn _1/3 Co _1/3 O ₂ , may be used.

Among these positive electrode materials, the preferred positive electrode materials targeted by the present invention are lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, and lithium iron phosphate, which have a relatively simple composition and are likely to be in demand soon for the recovery of metals from waste batteries. Among these, the most preferred are cobalt-based positive electrode materials, which are the most expensive, and manganese-based positive electrode materials, which are relatively safe and have a high prevalence in Japan, and the most preferred is cobalt-based positive electrode materials.

The positive electrode material to be the target of metal dissolution may be dismantled or scrapped waste lithium-ion batteries collected as waste, or intermediate products in the manufacturing process of lithium-ion batteries. There are no particular limitations on the positive electrode material as long as it is derived from waste lithium-ion batteries. It is more preferable if the positive electrode material is one that has been sieved and is available as a powder.

In the present invention, when dissolving metal from a cathode material, the cathode material is heated by irradiating it with microwaves in the presence of an acidic solution. The microwave irradiation method is not limited and can be performed continuously or intermittently, with continuous irradiation being preferred from the viewpoint of rapid dissolution processing.

The mechanism by which a substance is heated by microwaves depends on the microwave energy, which is calculated using the following formula, and it is known that the effect of dielectric heating is significant.
Microwave energy = dielectric heating + magnetic heating (relative permeability ≒ 1) + Joule heating

In other words, it is believed that the larger the dielectric loss of a substance is, the easier it is to heat it with microwaves. Examples of solvents with large dielectric loss include water, methanol, and acetone, while examples of solvents with small dielectric loss include benzene and toluene.

In addition, according to the book "Microwave Chemistry" by Satoshi Horikoshi et al. (published by Sankyo Publishing in December 2013), the microwave heating effect on major solids is known to be highest for cobalt oxide, followed by nickel oxide and manganese oxide at similar levels (see Table 1). In this respect, cobalt oxide is a substance that is easier to heat with microwaves than manganese oxide and nickel oxide.

In the present invention, the metal contained in the positive electrode material is dissolved in an acidic solution. As the acid of the acidic solution, strong acids such as hydrochloric acid, sulfuric acid, or nitric acid are preferable, and hydrochloric acid is preferable because it has good solubility of the salt (chloride) produced. As the solvent of the acidic solution, water, methanol, and acetone, which are solvents with large relative dielectric loss, are preferable. The above-mentioned methanol (boiling point of about 65°C) and acetone (boiling point of about 56°C) have disadvantages such as the inability to increase the liquid temperature during dissolution treatment at normal pressure due to their low boiling points and the need to recover the solvent after dissolution treatment. Water is a more preferable solvent because it allows dissolution treatment at a higher temperature and does not require solvent recovery. As the acidic solution, an aqueous hydrochloric acid solution is the most preferable.

The concentration of the hydrochloric acid solution is preferably 1 to 3 mol/L, more preferably 1.2 to 2.8 mol/L, and even more preferably 1.5 to 2.5 mol/L. The amount of hydrochloric acid used is preferably 2 to 5 times the equivalent of the target cathode material (metal oxide). More preferably, it is 2.2 to 4.8 times equivalent, and particularly preferably 2.5 to 4.5 times equivalent. If the amount of acid used is too small, the amount of metal dissolved per unit time decreases, resulting in inefficiency. On the other hand, if the amount of acid used is too large, not only will the amount of metal dissolved per unit time reach a plateau, but post-processing to neutralize the excess acid will become complicated, which may result in high costs.

In the dissolution method of the present invention, the dissolution time is usually 1 to 10 hours. The dissolution method may be batch or continuous, as long as it is a method that can be irradiated with microwaves.

[Dissolving apparatus]
1 is a schematic diagram illustrating one embodiment of the dissolving apparatus of the present invention. The dissolving apparatus 1 includes at least a cathode material filling device 3 for filling a cathode material 2, a microwave reaction device 4 for irradiating microwaves to the cathode material 2, a liquid storage tank 5 for storing an acidic solution for dissolving the cathode material, and a liquid circulation system 6 for returning the acidic solution containing the metal dissolved in the liquid to the liquid storage tank 5 after sending the acidic solution in the liquid storage tank 5 to the cathode material filling device 3. The liquid storage tank 5 is preferably equipped with a stirring device 11.

In FIG. 1, the liquid circulation system 6 includes a liquid delivery pipe 6a, a three-way valve 6b for adjusting the liquid flow direction, a stop valve 6c, and a liquid delivery pump 6d. The liquid circulation system 6 is for circulating the acidic solution within the dissolution device 1, and is not limited to the example shown in FIG. 1. Furthermore, the configurations and combinations of the pipes, pumps, valves, and other elements in general devices can be used.

In the present invention, the microwave reactor 4 is for irradiating microwaves to the cathode material 2 in the cathode material filling device 3. In order to level out the amount of microwave irradiation, the microwave reactor 4 is preferably equipped with a thermometer 12 (temperature sensor) for measuring the temperature of the acidic solution in the device 3, and a microwave reactor temperature control panel 7 (with PID control function) for temperature control. By PID controlling the output of the microwave reactor 4 based on the temperature data of the acidic solution detected by the thermometer 12 and the set temperature of the control panel 7, the liquid temperature of the acidic solution can be maintained at a substantially constant temperature while continuously irradiating microwaves.

The frequency of the microwaves to be irradiated is preferably 1 to 6 GHz, and more preferably 1.5 to 4 GHz. At frequencies below 1 GHz and above 6 GHz, the dielectric loss of the positive electrode material is small, so the amount of metal dissolved from the positive electrode material decreases, making it difficult to efficiently recover the metal.

The liquid temperature near the cathode material during microwave irradiation is preferably kept at 60°C or higher, and more preferably in the range of 60°C to 80°C, in order to improve the efficiency of metal dissolution. If the temperature is below 60°C, the metal dissolution rate decreases and a long period of treatment is required, resulting in low dissolution efficiency. On the other hand, if the temperature exceeds 80°C, the amount of hydrochloric acid gas that vaporizes increases and the hydrochloric acid concentration in the liquid decreases, which also results in a slower metal dissolution rate and lower dissolution efficiency.

The cathode material 2 is filled inside the cathode material filling device 3. The form of the cathode material 2 varies depending on the method of recovery from the lithium ion battery, but it may be in any form, such as scrap, solid, or powder. In order to improve the efficiency of dissolving the cathode material, a form with a large surface area is preferable. For example, coarsely pulverized products, finely pulverized products, powder products, etc. are preferred forms. In the case of coarsely pulverized products, etc., they may be further pulverized and then fed to the dissolving device.

In order to ensure the contact time of the acidic solution with the cathode material 2 and to increase the efficiency of dissolving the metal by microwave irradiation, the cathode material filling device 3 is preferably configured so that the acidic solution is circulated through the cathode material 2 from below the device 3 and discharged from above the device 3. The acidic solution that has dissolved the metal and is discharged outside the device 3 is then returned to the liquid storage tank 5, making it possible to dissolve a large amount of metal in a short leaching operation.

The acidic solution returned to the storage tank 5 is again supplied from the storage tank 5 to the cathode material filling device 3, so that it circulates between the storage tank 5 and the cathode material filling device 3. When discharging the acidic solution that has circulated through the cathode material filling device 3 to the outside of the device, the three-way valve 6b is closed and the stop valve 6c is opened. When supplying the acidic solution from the storage tank 5 to the cathode material filling device 3 and when circulating the acidic solution, the stop valve 6c and the three-way valve 6b are opened.

The acid solution is circulated within the device 1 until the metal concentration in the acid solution reaches a predetermined concentration or higher. It is advisable to measure the metal concentration in the acid solution by providing an appropriate sampling location within the liquid circulation system and sampling and analyzing the acid solution from that location at appropriate times.

The circulation rate of the acid solution in the circulation system is preferably set to approximately 5 ml/min to 20 ml/min in terms of the efficiency of dissolving the metal. If the circulation rate is within this range, the dissolution rate of the metal will not become extremely slow.

By carrying out the above dissolution process, valuable metals such as Co, Ni, and Mn contained in the positive electrode material can be recovered.

The dissolution method and dissolution device of the present invention are suitable as a method for dissolving positive electrode materials recovered from lithium ion batteries for vehicle use, power storage, etc. In addition, the lithium ion battery may be a liquid electrolyte, gel electrolyte, polymer electrolyte, solid electrolyte, etc., and the type of electrolyte is not limited.

Next, the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples.

Example 1
The dissolution apparatus (1) shown in FIG. 1 was used.
A cathode material filling device (3) for filling the cathode material (2) was installed inside a microwave reaction device (4). A 200 ml five-neck flask equipped with a Liebig cooling tube (10) and a magnetic stirrer (11) was prepared as a liquid storage tank (5) separately from the device. The liquid storage tank (5) and the cathode material filling device (3) were connected by a liquid circulation system (6) equipped with a pipe (6a), a three-way valve (6b) and a stop valve (6c). The liquid was flowed from the liquid storage tank (5) to the bottom of the cathode material filling device (3) via a pump (6d), the liquid was discharged from the top of the device, and the discharged liquid was returned to the liquid storage tank again, so that the liquid was circulated between the liquid storage tank (5) and the cathode material filling device (3).
The temperature of the microwave reactor temperature control panel (7) was set to 70° C., and microwaves with a frequency of 2.45 GHz and a maximum output of 700 W were continuously irradiated under PID control. During this time, the liquid temperature was maintained at 70° C. The temperature measured by the thermometer (12) was stored in the data logger (8) and the PC (9).

3 g (0.031 mol) of powdered positive electrode material LiCoO ₂ (reagent) was placed in the positive electrode material filling device (3), and 180 mL of 2 mol/L hydrochloric acid solution (HCl: 0.36 mol, approximately 3 times equivalent to the positive electrode material) was placed in a five-neck flask (liquid storage tank). After starting circulation of the hydrochloric acid solution and irradiating it with microwaves for a predetermined time, the Co concentration dissolved in the hydrochloric acid solution in the flask was measured by the 1-(2-pyridylazo)-2-naphthol (PAN) method using a measuring device: PCII manufactured by DKK-TOA Corporation. The measurement results are shown in Figure 2.
The microwave irradiation time was set to three conditions of 1 hour, 2 hours, and 5 hours. In FIG. 2, the relationship between the amount of dissolved Co and the amount of consumed electric power is shown instead of the irradiation time.

Example 2
The same operation as in Example 1 was carried out except that 3 g (0.032 mol) of powdered positive electrode material LiMnO ₂ (reagent) and 180 mL of hydrochloric acid solution (about 2.8 times equivalent to the positive electrode material) were placed in the positive electrode material filling device (3). The Mn concentration dissolved in the hydrochloric acid solution after microwave irradiation was measured by the periodate oxidation method using a measuring device: HI709 manufactured by Hanna Instruments Japan Co., Ltd. The measurement results are shown in FIG.

Example 3
The same operation as in Example 1 was carried out except that 2 g (0.021 mol) of plate-shaped positive electrode material LiNiO ₂ (cut into a plate-shaped product of about 10 mm × 10 mm square) was placed in the positive electrode material filling device (3) and 180 mL of hydrochloric acid solution (about 4.4 times equivalent to the positive electrode material) was placed in the positive electrode material filling device (3). The Ni concentration dissolved in the hydrochloric acid solution after microwave irradiation was measured using the same device and method as in Example 1. The measurement results are shown in FIG.

(Comparative Examples 1 to 3)
In Examples 1 to 3, except that a ribbon heater was wrapped around the cathode material filling device for heating instead of irradiating microwaves from the microwave reactor, circulation of the hydrochloric acid solution was started and heating was performed for a predetermined period of time, and then the concentrations of Co, Ni, and Mn dissolved in the hydrochloric acid solution in the flask were measured in the same manner as in Examples 1 to 3. The measurement results are shown in Figures 2 to 4.
In Comparative Examples 1 to 3, the heating time was set to three conditions of 1 hour, 2 hours, and 5 hours. As in Examples 1 to 3, the relationship between the amount of dissolved metal and the amount of power consumed was shown in the figure instead of the heating time.

From the above experimental results, it was found that there was a difference in the amount of metal dissolved per unit of electric power between microwave heating and heater heating.
In the case of microwave irradiation, the irradiation time and power consumption are not necessarily directly proportional, but when the maximum amount of dissolved metal in the case of microwave irradiation is compared with the maximum amount of dissolved metal in the case of heater heating, in the case of Co, the amount was 11,000 ppm (equivalent to 109% of the Co tested) in the case of microwave irradiation, whereas the amount was 4,800 ppm (equivalent to 48% of the Co tested) in the case of heater heating, which shows that about twice the amount of Co dissolved in the case of heater heating was dissolved in the case of microwave irradiation.

In addition, when comparing the amount of Co dissolved at the same power consumption of about 150 Wh, microwave irradiation dissolved 10,000 ppm (equivalent to 99% of the Co tested), whereas heater heating dissolved a maximum of 4,800 ppm (equivalent to 48% of the Co tested). This also shows that microwave irradiation dissolved about twice the amount of Co as heater heating, and that microwave irradiation is more advantageous in terms of energy usage than heater heating.

In the case of Mn, when comparing the maximum amount of dissolved metal, the microwave irradiation yielded 4,700 ppm (corresponding to 47% of the Mn tested) and the heater heating yielded 2,200 ppm (corresponding to 23% of the Mn tested). As in the case of Co, the microwave irradiation yielded approximately twice the amount of dissolved metal as the heater heating.
When comparing the amount of dissolution when the power consumption is the same, the difference is not as significant as in the case of Co, but with a power consumption of about 60 Wh, microwave irradiation resulted in 2,300 ppm (equivalent to 24% of the Mn tested), while heater heating resulted in 2,000 ppm (equivalent to 20% of the Mn tested), indicating that microwave heating is also advantageous in terms of energy.

In the case of Ni, the difference was not as great as in the cases of Co and Mn, but the maximum amount of dissolved metal was 5,200 ppm (equivalent to 78% of the Ni tested) with microwave irradiation and 5,000 ppm (equivalent to 75% of the Ni tested) with heater heating, meaning that the amount dissolved was slightly greater with microwave irradiation than with heater heating.
In addition, when the power consumption was the same, the amount of dissolution was 4,300 ppm (equivalent to 63% of the Ni tested) with microwave irradiation at a power consumption of approximately 70 Wh, while the amount of dissolution was a maximum of 3,500 ppm (equivalent to 51% of the Ni tested) with heater heating, indicating that microwave heating is more advantageous in terms of energy.

According to the dissolution method of the present invention, since the metal contained in the positive electrode material is heated by microwaves, particularly good results were obtained for _LiCoO2 , which has a large relative dielectric loss. Also, a significant difference was observed for _LiMnO2 compared to conventional heater heating. It was also found that microwave irradiation is more advantageous than heater heating for _LiNiO2 , although not as much as for _LiCoO2 and _LiMnO2 .

The present invention has been described above, but it goes without saying that the present invention can be modified in various ways within the scope of the present invention, such as by installing multiple cathode material filling devices in one microwave reactor or by using multiple microwave reactors.

According to the present invention, valuable metals used in the positive electrode material can be recovered from waste lithium-ion batteries and the like at low cost.

REFERENCE SIGNS LIST 1 Dissolving device 2 Cathode material 3 Cathode material filling device 4 Microwave reactor 5 Liquid storage tank 6 Liquid circulation system 6a Piping 6b Three-way valve 6c Stop valve 6d Pump 7 Microwave reactor temperature control panel 8 Data logger 9 PC
10 Cooling pipe 11 Stirring device 12 Thermometer

Claims (3)

When the metals contained in the positive electrode material of a lithium-ion battery are dissolved in an acidic solution,
As the acidic solution, a 1 to 3 mol/L aqueous hydrochloric acid solution is used,
The dissolving method is characterized in that the acidic solution is heated by irradiating it with microwaves while being in contact with the cathode material , thereby maintaining the liquid temperature during contact in the range of 60 to 80°C . The dissolution method according to claim 1, wherein the positive electrode material is a positive electrode material containing one or more metals selected from the group consisting of cobalt, manganese, and nickel, and lithium metal. A dissolving apparatus for dissolving metals contained in a positive electrode material of a lithium ion battery in an acidic solution,
A storage tank for storing the acidic solution;
a cathode material filling device for filling the cathode material powder;
a microwave reaction device that irradiates the cathode material filling device with microwaves in the presence of the acidic solution to heat the acidic solution ;
a liquid circulation system that circulates the acidic solution in the storage tank to the cathode material filling device;
Equipped with
The microwave reactor is equipped with a temperature control panel with a PID control function, and the output of the microwave reactor is PID controlled,
A dissolution apparatus characterized in that it does not have a heating tank for heating the acidic solution.