JP5359148B2 - Solvent recovery system and solvent recovery method - Google Patents

Description

  The present invention relates to a solvent recovery system and a solvent recovery method.

  In recent years, lithium ion secondary batteries have attracted attention as secondary batteries for motor driving that hold the key to commercialization of electric vehicles and hybrid electric vehicles. Lithium ion secondary batteries generally have a structure in which flat electrodes are formed on the plane of a metal foil as a current collector, and a plurality of these are laminated.

  The electrode is formed by applying a slurry containing an active material, a binder, a conductive agent, and a solvent that uniformly disperses them to a metal foil and evaporating the solvent to dry the electrode. For example, in the invention described in Patent Document 1, the slurry is heated by an induction coil that applies heat by the action of a magnetic field, and the solvent in the slurry is evaporated. In order to prevent deterioration and performance degradation, the induction coil is cooled by, for example, a refrigerant pipe during heating.

The evaporated solvent is collected and processed according to environmental measures at the factory or the like. For the recovery of the solvent, a cooling condensation method or an adsorption method is mainly used. The cooling condensation method is a method in which the evaporated solvent is cooled and condensed to be recovered, and the adsorption method is a method in which the evaporated solvent is adsorbed on an adsorbent and recovered. In any method, since the recovery rate is improved due to the temperature decrease of the solvent, the solvent discharge can be suppressed by cooling the evaporated solvent.
JP 2004-335374 A

  However, the temperature of the heated and evaporated solvent is rising, and energy is required for cooling. For this reason, efficient cooling of the solvent, and hence realization of energy saving becomes a problem.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a solvent recovery system and a solvent recovery method that can efficiently cool the solvent and realize energy saving.

The solvent recovery system of the present invention for achieving the above object includes a drying unit that evaporates a solvent contained in a slurry used for electrode formation applied to a metal foil by an induction coil that applies heat by the action of a magnetic field; A recovery unit for recovering the evaporated solvent. Moreover, the solvent collection | recovery system of this invention has a cooling part which cools an induction coil, and cools the evaporated solvent by the cooling part which cools an induction coil between a drying part and a collection | recovery part.

  In order to achieve the above object, the solvent recovery method of the present invention comprises a drying step of evaporating a solvent contained in a slurry used for electrode formation applied to a metal foil by an induction coil that applies heat by the action of a magnetic field; A recovery step of recovering the evaporated solvent. Moreover, the solvent collection | recovery method of this invention has a cooling process which cools the evaporated solvent by the cooling part which cools an induction coil between a drying process and a collection process.

  In the present invention, the evaporated solvent is cooled by the cooling unit that cools the induction coil. That is, the present invention uses the cooling unit to cool the evaporated solvent, so that the solvent can be efficiently cooled to realize energy saving.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic diagram showing a solvent recovery system according to an embodiment, and FIG. 2 is a schematic diagram for explaining a solvent recovery device.

  In brief, the solvent recovery system 10 of the present embodiment recovers the solvent that evaporates in the process of producing the electrode of the lithium ion secondary battery, and recovers the evaporated solvent after cooling. In the production of an electrode of a lithium ion secondary battery, a slurry 64 containing a solvent is applied to both surfaces of a metal foil 63 as a current collector, and the solvent in the slurry 64 evaporates in the process of heating and solidifying the slurry 64.

  As shown in FIG. 1, the solvent recovery system 10 cools the induction coil 37, 38 that evaporates the solvent in the slurry 64 by the induction coils 37, 38 that apply heat, and the induction coil 37, 38. And a cooling device 50 (corresponding to a cooling unit). The solvent recovery system 10 includes a circulation unit 20 that circulates the evaporated solvent, and a solvent recovery device 29 (corresponding to a recovery unit) that is connected to the circulation unit 20 and recovers the solvent.

  In addition to the induction coils 37 and 38, the drying furnace 30 has a magnetic core 39 made of ferrite and a casing 31 surrounding them. Further, the drying furnace 30 has an inlet 32 and an outlet 33 through which the metal foil 63 passes in the casing 31.

  The plurality of induction coils 37 face one surface of the metal foil 63. On the other hand, the plurality of induction coils 38 face the other surface of the metal foil 63. The induction coils 37 and 38 are made of copper tubes. The induction coils 37 and 38 are electrically connected to a power source (not shown), and a magnetic field is applied to the metal foil 63 to inductively heat the metal foil 63. Due to the heat of the metal foil 63, the solvent in the slurry 64 evaporates and the solidification of the slurry 64 proceeds. Since the magnetic core 39 covers each of the induction coils 37 and 38 to form a magnetic path, the induction coils 37 and 38 can efficiently heat the slurry 64.

  The slurry 64 for forming an electrode includes a positive electrode slurry used for forming a positive electrode and a negative electrode slurry used for forming a negative electrode.

  The positive electrode slurry has, for example, a positive electrode active material, a conductive additive, and a binder, and by adding a solvent, these are uniformly dispersed to have a predetermined viscosity. The positive electrode active material is, for example, lithium manganate. The conductive auxiliary agent is, for example, acetylene black. The binder is, for example, PVDF (polyvinylidene fluoride). The solvent is, for example, NMP (normal methyl pyrrolidone).

  The positive electrode active material is not particularly limited to lithium manganate, but it is preferable to apply a lithium-transition metal composite oxide from the viewpoint of capacity and output characteristics. For example, carbon black or graphite can be used as the conductive assistant. The binder is not limited to PVDF.

  On the other hand, the negative electrode slurry has, for example, a negative electrode active material, a conductive additive, and a binder, and by adding a solvent, these are uniformly dispersed to have a predetermined viscosity. The negative electrode active material is, for example, graphite. The conductive assistant, binder, and solvent are, for example, acetylene black, PVDF, and NMP, respectively.

  The negative electrode active material is not particularly limited to graphite, and hard carbon or lithium-transition metal composite oxide can also be used. For example, carbon black or graphite can be used as the conductive assistant. The binder is not limited to PVDF.

  The solvent for the positive electrode slurry and the solvent for the negative electrode slurry are not limited to NMP, and known solvents can be used. The solvent for the positive electrode slurry and the solvent for the negative electrode slurry are the same and are preferably a single solvent from the viewpoint of reuse.

  A slide die 61 having straight slits applies the slurry 64 to the metal foil 63 intermittently. The portion where the metal foil 63 is exposed between the slurry 64 and the slurry 64 serves as a tab for electrically connecting the batteries or battery terminals and the metal foil 63.

  For the metal foil 63, an appropriate material such as aluminum, copper, nickel, iron, or stainless steel can be used. Specifically, for example, a metal foil 63 such as aluminum can be used for the positive electrode current collector, and a metal foil 63 such as copper can be used for the negative electrode current collector. Although there is no restriction | limiting in particular about the specific thickness of the metal foil 63, For example, in the case of aluminum, it is a thin film of about 20 micrometers, and in the case of copper, it is about 10 micrometers.

  The number of electrodes used for one unit cell is very large, and in order to mass-produce the electrodes, it is common to apply slurry 64 to a long metal foil 63 and continuously produce it. In the case of continuous production in this way, a roll-to-roll system is suitable for the electrode stacking (storage) system.

  For this reason, in this embodiment, the winding roll 65 which winds up the metal foil 63 conveys the metal foil 63 from the supply roll 62 which supplies the metal foil 63. The supply roll 62 winds the metal foil 63, and the take-up roll 65 winds the metal foil 63 while being driven to rotate by the motor M. The slit die 61 applies a slurry 64 to the metal foil 63 being conveyed. The applied slurry 64 moves as the metal foil 63 is conveyed and passes through the drying furnace 30.

  The drying furnace 30 includes an air supply port 34 that is a gas outlet on the lower side of the conveyance path through which the metal foil 63 passes, and an exhaust port 35 for discharging evaporated solvent on the upper side of the conveyance path. Since the evaporation amount of the solvent in the slurry 64 is larger on the inlet 32 side than on the outlet 33 side of the drying furnace 30 where the heating is completed, the exhaust port 35 is the inlet 32 of the inlet 32 and the outlet 33 of the drying furnace 30. Located on the side.

  The circulation unit 20 includes a pipe 28 that communicates with the exhaust port 35 and the intake port 27 for taking gas into the drying furnace 30, a pipe 26 that communicates with the intake port 27 and the air supply port 34, and a blower connected to the pipe 26. The fan 24 is used. While the drying furnace 30 heats the slurry 64 to evaporate the solvent, the blower fan 24 operates.

  When the blower fan 24 is activated, an inert gas such as nitrogen introduced into the drying furnace 30 and the circulation unit 20 circulates as a carrier gas for transporting the evaporated solvent. The carrier gas containing the evaporated solvent flows into the drying furnace 30 through the exhaust port 35, the pipe 28, the intake port 27, and the pipe 26, and through the small hole of the punching metal 36 provided in the air supply port 34. , Continually circulating. The solvent recovery device 29 is connected to the pipe 28 between the exhaust port 35 and the intake port 27 to recover the solvent contained in the carrier gas.

  A controller 60 mainly composed of a CPU and a memory controls the drying furnace 30, the slit die 61, the motor M, and the blower fan 24. The controller 60 controls the operation of the drying furnace 30 and adjusts the output of the induction coils 37 and 38. The controller 60 also controls the operation of the slit die 61 to adjust the application amount, application thickness, etc. of the slurry 64. The controller 60 controls the operation of the motor M to adjust the conveyance speed of the metal foil 63. The controller 60 also controls the operation of the blower fan 24 to adjust the flow rate of the carrier gas to be circulated. The memory of the controller 60 stores a program for controlling the operation.

  The cooling device 50 that cools the induction coils 37 and 38 includes a chiller 51 for circulating the refrigerant and keeping the circulating refrigerant at a constant temperature, and a refrigerant pipe 52 communicating with the chiller 51. The refrigerant is, for example, water.

  The refrigerant pipe 52 is in contact with the magnetic core 39 (the parts denoted by reference numerals 54 and 55 in FIG. 1 and referred to as heat removal units 54 and 55). Further, the refrigerant pipe 52 is in contact with the pipe 28 between the drying furnace 30 and the solvent recovery device 29 so as to be wound around (the part indicated by reference numeral 53 in FIG. 1 and referred to as the heat removal unit 53).

  The water flowing through the refrigerant pipe 52 flows out of the chiller 51, passes through the heat removal unit 53, passes through the heat removal units 54 and 55, and returns to the chiller 51. The cooling device 50 cools the magnetic core 39 and the induction coils 37 and 38 by the heat removal units 54 and 55. In addition, the cooling device 50 cools the evaporated solvent before being discharged from the drying furnace 30 and reaching the solvent recovery device 29 by the heat removal unit 53. Since the water as the refrigerant passes through the heat removal unit 53 before passing through the heat removal units 54 and 55, the cooling device 50 can enhance the cooling effect of the evaporated solvent.

  The solvent recovery device 29 condenses and recovers the solvent. Specifically, as shown in FIG. 2, the solvent recovery device 29 has a coiled pipe 21 through which a refrigerant flows, and a carrier gas 23 containing a solvent is brought into contact with the pipe 21 to condense the solvent. To recover the liquid 25. The solvent recovered by the solvent recovery device 29 is reused after being subjected to centrifugal separation or distillation heating. Moreover, you may dispose of the collect | recovered solvent in a processing place.

  The effect of this embodiment will be described.

  In the present embodiment, the cooling device 50 cools the evaporated solvent between the drying furnace 30 and the solvent recovery device 29. That is, in the present embodiment, the cooling device 50 is used to cool the evaporated solvent, so that the solvent can be efficiently cooled to realize energy saving.

  In the present embodiment, since the cooling device 50 cools the atmosphere in the drying furnace 30 as well as the induction coils 37 and 38 and the magnetic core 39 by the heat removal units 54 and 55, the temperature of the atmosphere in the drying furnace 30 is reduced. The rise is suppressed, and the solvent is easily condensed in the solvent recovery device 29.

  In this embodiment, since the solvent recovery device 29 cools the carrier gas and condenses and recovers the solvent, the circulating carrier gas can be cooled, and when the carrier gas returns to the drying furnace 30, the induction coils 37, 38 and Helps cool the magnetic core 39.

  In this embodiment, the atmosphere in the drying furnace 30 is not heated, but the solvent in the slurry 64 is evaporated by the induction coils 37 and 38 that directly apply heat to the slurry 64. For this reason, for example, compared with the case where the atmosphere is heated such as when hot air is applied to the slurry 64 to evaporate the solvent, the temperature rise of the atmosphere in the drying furnace 30 is suppressed, and the carrier gas discharged from the drying furnace 30 is reduced. Temperature rise is suppressed. Therefore, the condensation of the solvent is easy, and the solvent recovery device 29 can recover the solvent efficiently.

  The slurry 64 of this embodiment contains a single solvent. Therefore, in this embodiment, it is prevented that a plurality of solvents are mixed and collected, and reuse after collection is easy.

  The exhaust port 35 of the drying furnace 30 is provided on the side of the inlet 32 where the evaporation amount of the solvent in the slurry 64 is large, out of the inlet 32 and the outlet 33 of the drying furnace 30, and this embodiment improves the solvent recovery rate. It can be improved.

  In the present embodiment, since the carrier gas containing the solvent circulates, the solvent recovery device 29 can recover the solvent that cannot be recovered at a time in the process of circulation, thereby improving the recovery rate. Therefore, this embodiment can suppress the discharge of the solvent.

  Further, in this embodiment, since the carrier gas containing the solvent circulates, backflow is prevented, and the solvent contained in the carrier gas surely passes through the solvent recovery device 29. Therefore, this embodiment has a good solvent recovery rate.

  Further, since the carrier gas containing the solvent circulates while the solvent evaporates in the drying furnace 30, the induction coils 37 and 38 and the magnetic core 39 can be cooled by this flow.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims. For example, the solvent recovery device 29 is not limited to the one described above, and may be another known device that recovers the solvent. Specifically, what adsorb | sucks a solvent to adsorption materials, such as activated carbon, and collect | recovers a solvent is mentioned.

It is the schematic which shows a solvent collection | recovery system. It is the schematic for demonstrating a solvent collection | recovery apparatus.

Explanation of symbols

10 solvent recovery system,
20 Circulation section,
24 blower fan,
26, 28 piping,
29 Solvent recovery device (recovery unit),
30 Drying oven (drying section),
31 casing,
32 entrance,
33 Exit,
34 Air inlet,
35 Exhaust port,
36 punching metal,
37, 38 induction coil,
39 Magnetic core,
50 Cooling device (cooling part),
51 Chiller,
52 refrigerant pipe,
53, 54, 55 Heat removal part,
60 controller,
61 Slit die,
62 supply rolls,
63 metal foil,
64 slurry,
65 take-up roll,
M motor.

Claims (5)

A drying unit that evaporates the solvent contained in the slurry used for electrode formation applied to the metal foil by an induction coil that applies heat by the action of a magnetic field;
A recovery unit for recovering the evaporated solvent;
A cooling unit for cooling the induction coil,
A solvent recovery system that cools the evaporated solvent by a cooling unit that cools the induction coil between the drying unit and the recovery unit.   The solvent recovery system according to claim 1, wherein the slurry contains a single solvent. The slurry is heated while moving in the drying unit with the conveyance of the metal foil,
3. The solvent recovery according to claim 1, wherein an exhaust port of the drying unit for discharging the evaporated solvent is provided on the inlet side of an inlet and an outlet of the drying unit through which the metal foil passes. system.   The solvent recovery system according to claim 1, wherein the evaporated solvent circulates through the recovery unit and the drying unit while the solvent evaporates in the drying unit. A drying step of evaporating the solvent contained in the slurry used for electrode formation applied to the metal foil by an induction coil that applies heat by the action of a magnetic field;
A recovery step of recovering the evaporated solvent;
A cooling method for cooling the evaporated solvent by a cooling unit that cools the induction coil between the drying step and the recovery step.

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