JP2014207192A - Process of manufacturing positive electrode active material slurry, process of manufacturing positive electrode active material powder, and process of manufacturing positive electrode plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of recovering a positive electrode active material from a positive electrode waste at low cost and low environmental load and reusing it in a state where high battery performance is maintained.SOLUTION: By rolling and stirring a positive electrode waste in a polar solvent, peeling an active material, a conductive material, and a binder from a substrate, removing the substrate, obtaining a positive electrode active material powder or a positive electrode active material slurry containing the active material, the conductive material, and the binder, and using it for a positive electrode plate, it becomes possible to reuse a positive electrode active material at low cost that maintains high performance.

Description

  The present invention relates to a positive electrode active material slurry and a positive electrode active material powder manufacturing method for recovering and reusing a positive electrode active material from a positive electrode waste material of a lithium ion secondary battery, and a positive electrode plate manufacturing method using the positive electrode active material.

Recently, one of the global environmental issues, in the CO ₂ reduction is urged as global warming prevention measures, serious active electric vehicle is expected to be one of the solutions. A secondary battery is mounted on a battery of the electric vehicle, and a lithium ion secondary battery (hereinafter referred to as LIB) is mainly mounted. Furthermore, LIB will be installed in mobile electric devices such as mobile phones, smartphones, notebook computers, and secondary batteries for power storage, and it is expected that the demand for LIB will increase rapidly in the future.

  Metals such as cobalt, nickel, and lithium are mainly used for the positive electrode active material of LIB, and these metals are indispensable materials for the positive electrode plate of LIB. However, there are concerns about the stable supply due to the uneven distribution of these metals and the risk of price increases.

  Under such circumstances, in order to solve global environmental problems and supply risks while maintaining the LIB market, which will continue to increase, studies on methods for recovering and recycling active materials containing valuable metals used in LIB cathode plates Has been made. In particular, as a method for recovering the positive electrode active material efficiently and at low cost, the active material is peeled off from the substrate of the positive electrode plate, and decomposed by applying thermal energy at a high temperature to remove the binder and conductive material adhering to the active material. A method of performing processing has been proposed (Patent Document 1).

  However, when thermal energy in a high temperature region is applied to the positive electrode active material, it is considered that a reduction reaction occurs in which the conductive material mixed with the active material extracts oxygen in the active material. Also, in the LIB positive electrode plate, there are cases where a plurality of types of active materials are mixed so that the reaction in the battery becomes an ideal combination, but the recovery is performed from the mixed positive electrode plate. When heat energy in the high temperature region is applied to the positive electrode active material, a reaction in which Li is selectively deprived from one active material to the other active material and each decomposition reaction proceed, resulting in decomposition / degradation. There is a concern that (= deactivation as an electrode) will continue.

Furthermore, these materials must be newly added in the coating process by decomposing the binder and conductive material contained in the positive electrode plate using thermal energy. It is conceivable that the manufacturing cost of the plate increases. Moreover, since this processing method requires thermal energy in a high temperature region, it may lead to an increase in the load on the global environment such as CO ₂ emission.

  Patent Document 2 discloses a technique in which a positive electrode plate coated with a positive electrode mixture containing a positive electrode active material is pulverized and mixed with an organic solvent to obtain a pulverized positive electrode paint. However, in this method, since the positive electrode plate is pulverized together with the substrate, the substrate is separated by the difference in particle size and specific gravity, and the positive electrode active material that has not been peeled off from the substrate cannot be recovered, and the substrate is mixed into the pulverized positive electrode However, there was a problem that was inevitable.

JP 2010-34021 A Japanese Patent Laid-Open No. 10-92417

  Therefore, in the present invention, excessive heat energy is not applied in the active material recovery process, and the use of necessary materials (conductive material, binder and polar solvent) in the process from recovery of active material to application (reuse) is minimized. The manufacturing method of the slurry or powder of the positive electrode active material which shows high battery characteristics while being low-cost and low environmental load, and the manufacturing method of a positive electrode plate using the same are proposed.

  That is, the present invention rolls and stirs the positive electrode waste material in a polar solvent to peel off the active material, the conductive material and the binder from the substrate, removes the substrate, and polarizes the active material, the conductive material and the binder. It is a manufacturing method of the positive electrode active material slurry which obtains a solvent slurry (this invention 1).

  Further, the present invention is a method for producing a positive electrode active material slurry according to the first aspect of the present invention, wherein the active material, the conductive material and the binder are peeled from the substrate in a polar solvent having a liquid temperature of 80 ° C. or less (the second aspect of the present invention). ).

  Moreover, this invention is a manufacturing method of the positive electrode active material slurry of this invention 1 or 2 whose polar solvent is N-methyl-2-pyrrolidone (this invention 3).

  Moreover, this invention is a manufacturing method of the positive electrode active material slurry in any one of this invention 1-3 which does not include the process of drying polar solvent slurry (this invention 4).

  Moreover, this invention is a positive electrode active material which dries the polar solvent slurry containing the active material, the electrically conductive material, and the binder obtained by the manufacturing method of the positive electrode active material slurry in any one of this invention 1-3. This is a method for producing a powder (Invention 5).

  Moreover, this invention is a manufacturing method of the positive electrode active material powder of this invention 5 whose drying temperature is 100 degrees C or less (this invention 6).

  In addition, the present invention provides a positive electrode mixture containing either the positive electrode active material slurry obtained by the production method according to any of the first to fourth aspects of the present invention or the positive electrode active material powder according to the fifth or sixth aspects of the present invention. It is the manufacturing method of the positive electrode plate which apply | coats and dries (this invention 7).

  According to the present invention, since the entire amount of the positive electrode mixture component on the substrate of the positive electrode waste material is recovered, the conductive material, the binder, and the active material can be reduced in the application process to the new substrate. The manufacturing cost can be kept low.

  Further, according to the present invention, the polar solvent used when the positive electrode active material or the like is peeled from the substrate can be used as the solvent for the positive electrode mixture, and the manufacturing cost of the positive electrode plate can be kept low.

  Further, according to the present invention, heat energy in the high temperature region is not applied consistently in the process of recovering the positive electrode active material from the positive electrode waste material, so that it can be reused for the positive electrode plate while maintaining high performance.

Recycling process of cathode waste materials for lithium ion secondary batteries Powder X-ray diffraction pattern of heat-treated recovered positive electrode active material

  The configuration of the present invention will be described in detail as follows.

  The present invention provides a polar solvent slurry containing an active material, a conductive material and a binder by rolling and stirring the positive electrode waste material in a polar solvent to peel off the active material, the conductive material and the binder from the substrate, and removing the substrate. Is what you get.

  In the present invention, the positive electrode waste material is a positive electrode plate for a lithium ion secondary battery prepared by applying a positive electrode mixture in which a positive electrode active material powder is mixed with a binder together with a conductive material, a binder, and the like to a substrate. . The positive electrode waste material may be a defective coating product at the time of manufacturing the positive electrode plate, a yield product generated at the time of manufacturing the battery, or a positive electrode plate taken out by disassembling the used battery. In particular, the present invention shows a high effect in the regeneration of a positive electrode plate that has been discarded without being used as a battery and whose performance has been deteriorated by exposure to an atmosphere of normal temperature and humidity. Further, the positive electrode waste material includes the waste of the positive electrode mixture generated at the time of manufacturing the positive electrode plate.

  The positive electrode plate which is a positive electrode waste material is preferably cut to about 5 to 10 mm square before the peeling step in a polar solvent. If the size of the positive electrode plate in the peeling step is too large, the peeling efficiency is lowered. If it is too small, the substrate may be mixed into the slurry when the substrate is separated after the peeling step.

  As the positive electrode active material contained in the positive electrode waste material, lithium metal oxide is generally used, and examples thereof include lithium cobalt oxide, lithium nickelate, and lithium composite oxide containing a plurality of metal species. In addition, a plurality of types of positive electrode active materials may be mixed so that the reaction in the battery is an ideal combination.

  As the substrate contained in the positive electrode waste material, a band-shaped aluminum foil or the like is usually used.

  In the present invention, the active material, the conductive material and the binder can be peeled from the substrate by rolling and stirring the positive electrode waste material in a polar solvent. Examples of the apparatus for rolling and stirring the positive electrode waste material in the polar solvent include a ball mill, a bead mill, a stamp mill, and an attritor. When using a ball mill, the ball is made of resin balls such as fluororesin, nylon and polyethylene, ceramic balls such as solid alumina and zirconia, Ceramic spheres or metal spheres coated with resin, nylon, polyethylene or the like are preferable. The ball diameter is preferably 5 to 20 mm. If it is too small, balls may be mixed into the slurry when the substrate is separated after the peeling step. Moreover, it is preferable that the filling rate of the ball | bowl to a ball mill reactor shall be 30-50 volume%.

  Since the substrate extends by rolling the positive electrode waste material, the active material and the like can be easily separated from the substrate. Further, since the active material and the like are peeled off while the size of the substrate is large, only the substrate can be easily removed from the polar solvent slurry after the peeling step.

  Further, the positive electrode active material and the like peeled off from the substrate may agglomerate in the solvent. In the present invention, since the agitation is performed simultaneously with the peeling, a sufficiently dispersible slurry having good dispersibility is used. Can be obtained.

  The polar solvent used in the present invention may be any solvent that does not dissolve the positive electrode active material and can dissolve the binder. In particular, a solvent that can be used as a component of the positive electrode mixture is preferable, and for example, N-methyl-2-pyrrolidone is preferable.

  Moreover, it is preferable to perform this invention by 5-50 weight% of positive electrode waste material density | concentration at the time of peeling. By increasing the concentration of the positive electrode waste material at the time of peeling, the amount of the polar solvent used can be reduced, and the production cost can be suppressed. Therefore, the positive electrode waste material concentration is more preferably 40 to 50% by weight.

  In the present invention, the active material, the conductive material, and the binder are preferably peeled from the substrate in a polar solvent having a liquid temperature of 80 ° C. or lower. If peeling is performed at a high temperature, loss due to evaporation of the polar solvent and alteration of the positive electrode active material and the polar solvent slurry may be caused, which is not preferable. More preferably, the active material, the conductive material, and the binder are peeled from the substrate in a polar solvent having a liquid temperature of 40 ° C. or lower. When peeling is performed at a liquid temperature exceeding 40 ° C., the peeling efficiency usually increases. However, according to the method of the present invention, sufficient peeling efficiency can be obtained even at 40 ° C. or lower, and the cost and environmental load are reduced. it can.

  After peeling off the active material, conductive material and binder from the substrate, the substrate is removed to obtain a polar solvent slurry containing the active material, conductive material and binder.

  The method for removing the substrate is a method that can remove only the substrate while leaving the components such as the active material, the conductive material and the binder contained in the positive electrode mixture used for the positive electrode waste material in the polar solvent slurry, Any method commonly used may be used.

  The polar solvent slurry obtained by the above method does not include a drying step, and is preferably used as a positive electrode active material slurry for a positive electrode mixture.

  The positive electrode active material slurry in the present invention contains a positive electrode active material, a conductive material, and a binder in the same manner as the positive electrode mixture used for the positive electrode waste material, and in particular, a polar solvent can be used for the positive electrode mixture. When it is a thing, it can be used independently as a positive electrode compound material. At this time, the concentration of the positive electrode active material slurry may be controlled so that the concentration of the polar solvent becomes a desired concentration from the peeling step, or after obtaining the polar solvent slurry, it is concentrated or diluted to obtain a desired concentration. It is good.

  Moreover, the positive electrode active material slurry in the present invention may be newly added with a positive electrode active material, a conductive material, a binder, and a polar solvent to form a positive electrode mixture. By using the positive electrode active material slurry in the present invention, the amount of conductive material and binder added can be reduced, and the polar solvent required for the production of the positive electrode active material slurry can be used as it is as the solvent for the positive electrode mixture. Can be used effectively as At this time, the density | concentration of a positive electrode active material slurry can be adjusted to a desired density | concentration according to the positive electrode compound material to produce.

  Moreover, positive electrode active material powder can be obtained by drying the whole amount of the polar solvent slurry containing the active material, the conductive material and the binder obtained by the above-described method.

  The positive electrode active material powder obtained by drying the whole amount of the polar solvent slurry without solid-liquid separation contained a positive electrode active material, a conductive material and a binder in the same manner as the positive electrode mixture used in the positive electrode waste material. It becomes powder. Therefore, the positive electrode mixture using the positive electrode active material powder produced by the present invention can reduce the amount of conductive material and binder added.

  In the present invention, in order to obtain the positive electrode active material powder by drying the polar solvent slurry, the drying temperature is preferably 100 ° C. or lower. If drying is performed at a temperature exceeding 100 ° C., the positive electrode active material may be deteriorated, which is not preferable. Further, when drying is performed at a high temperature, the conductive material and the binder contained in the positive electrode active material powder may be decomposed.

  In recovering the positive electrode active material, it is preferable that the conductive material and the binder contained in the positive electrode mixture used in the positive electrode waste material and the residue of the polar solvent used when the positive electrode active material is peeled from the substrate in the present invention are preferable. If not, after the polar solvent slurry obtained by the above-mentioned method is dried, a positive electrode active material powder from which other components are removed by further degreasing treatment can be obtained.

  The degreasing treatment is a heat treatment for decomposing and removing a conductive material, a binder and the like. The temperature of the degreasing treatment is preferably 100 ° C. or higher and 400 ° C. or lower. Moreover, it is preferable that the processing time of a degreasing process is 1 hour or more and 10 hours or less. If the temperature of the degreasing process exceeds 400 ° C., the positive electrode active material changes in quality, and the battery characteristics deteriorate. The temperature of the degreasing treatment is more preferably 150 ° C. or higher and 350 ° C. or lower.

  The positive electrode active material powder in the present invention may be mixed with a polar solvent without using a new positive electrode active material, conductive material and binder, and may be used as a positive electrode mixture, or a new positive electrode active material, conductive material or binder. Alternatively, a positive solvent may be added to form a positive electrode mixture.

  A positive electrode plate can be manufactured by applying a positive electrode mixture containing either a positive electrode active material slurry or a positive electrode active material powder obtained by the manufacturing method according to the present invention to a substrate and drying it.

  In the following examples, the positive electrode waste material is composed of 90% by weight of a positive electrode active material mixed with lithium nickelate, lithium cobaltate, and lithium manganate, 6% by weight of carbon as a conductive material, and 4% by weight of PVDF as a binder. A positive electrode plate obtained by applying a mixed positive electrode mixture to an Al foil and drying it, which has been stored in a normal temperature and normal humidity atmosphere for a long time, is used.

The powder X-ray diffraction measurement of the positive electrode active material powder was performed using D8 manufactured by Bruker AXS Co., Ltd.
This was done using ADVANCE. The measurement was performed by filling positive electrode active material powder in a dedicated substrate and using a CuKα ray source in a diffraction angle range of 2θ = 10 to 90 ° to obtain a powder X-ray diffraction diagram.

  As for battery characteristics, a cycle characteristic test and a rate characteristic test using a coin cell were performed.

  A positive electrode plate produced using a positive electrode active material slurry or a positive electrode mixture containing a positive electrode active material powder obtained in Examples was used for the positive electrode, and metallic lithium was used for the negative electrode, each of which was formed from a microporous polypropylene film. Combined through a separator. The electrolyte was obtained by dissolving 1 mol of lithium hexafluorophosphate (LiPF6) in a 1: 1 mixed solvent of ethylene carbonate (EC) and methyl ethyl carbonate (MEC). An aqueous electrolyte secondary battery was prepared.

  Cycle characteristics were measured using the coin type battery at a temperature of 60 ° C., a final voltage of 3.0 to 4.3 V, a C rate of 0.1 C, and a discharge capacity up to 51 cycles. Table 1 shows the measurement results of the cycle characteristics.

  The rate characteristics are as follows. Using the coin-type battery, discharge at the second cycle with a temperature of 25 ° C., a final voltage of 3.0 to 4.3 V, and a C rate of 0.1 C, 1 C, 2 C, 5 C, and 10 C, respectively. The capacity was measured. Table 2 shows the measurement results of the rate characteristics.

Comparative Example 1
A coin-type non-aqueous electrolyte secondary battery was produced using the positive electrode waste as the positive electrode.

Example 1
Place 250 g of positive electrode waste material cut to 10 mm square and 529 g of balls into a 1 L ball mill reactor, add 0.3 L of N-methyl-2-pyrrolidone as a polar solvent, and stir at a liquid temperature of 30 ° C. for 3 hours. The active material, conductive material and binder were peeled off. As the ball mill ball, an iron ball coated with a fluorine resin having a spherical diameter of 10 mm was used. In addition, the slurry separated into the Al foil and the active material was passed through a sieve (aperture 53 μm) and separated into an Al foil (on the sieve) and a polar solvent slurry. The polar solvent slurry was concentrated to 50% by weight so that it could be directly applied to a new Al foil to obtain a positive electrode active material slurry (positive electrode mixture). The obtained positive electrode mixture was applied to an Al foil and dried, followed by compression molding with a roller press to obtain a belt-like positive electrode plate.

Example 2
A polar solvent slurry was obtained in the same manner as in Example 1. The whole amount of the obtained polar solvent slurry was dried at 80 ° C. to obtain a positive electrode active material powder. N-methyl-2-pyrrolidone as a polar solvent was added to the obtained positive electrode active material powder to obtain a positive electrode active material slurry (positive electrode mixture) having a concentration of 50% by weight. The obtained positive electrode mixture was applied to an Al foil and dried, followed by compression molding with a roller press to obtain a belt-like positive electrode plate.

Examples 3-10
A polar solvent slurry was obtained in the same manner as in Example 1. As shown in Table 2, the obtained polar solvent slurry was completely dried at 80 ° C., and then degreased at 200 ° C., 300 ° C., and 400 ° C. for 1 h, 5 h, and 7 h, respectively. Got. The positive electrode active material powder 90% by weight, 6% by weight of carbon as a conductive material, and 4% by weight of PVDF dissolved in N-methyl-2-pyrrolidone as a binder were mixed to form a positive electrode mixture Got. The obtained positive electrode mixture was applied to an Al foil and dried, followed by compression molding with a roller press to obtain a belt-like positive electrode plate.

  As shown in Table 1, the cycle characteristics of the battery using the positive electrode active material slurry (Example 1) or the positive electrode active material powder (Example 2) according to the present invention and the battery using the positive electrode waste material (Comparative Example 1) are compared. did. The battery of Comparative Example 1 using the positive electrode waste material showed the highest discharge capacity at the first cycle, but the discharge capacity greatly decreased as the number of cycles increased. On the other hand, in the battery of Example 1, the discharge capacity at the first cycle showed the same value as that of the battery of Comparative Example 1, and even when the number of cycles was repeated, the range of decrease in the discharge capacity was small.

  The deterioration of the cycle characteristics of the battery of Comparative Example 1 using the positive electrode waste material was deteriorated due to the fact that the characteristics originally possessed by the positive electrode active material used for the positive electrode waste material were stored in an environment of normal temperature and humidity. It is thought that. According to the present invention, the positive electrode active material can be recovered as it is from the positive electrode waste material and its characteristics can be recovered.

  As shown in Table 2, the battery of Example 1 using the positive electrode active material slurry prepared without removing the positive electrode active material from the positive electrode plate in a solvent, concentrating and drying was at a rate of 0.1 C. The discharge capacity was as high as 118.5 mAh / g. The battery of Example 1 maintained a high discharge capacity regardless of the increase in C rate.

  Even the batteries of Examples 2 to 10 using the positive electrode active material powder obtained by drying the slurry could be charged and discharged at a high level. Among them, the discharge capacity at a rate of 0.1 C is highest in the sample degreased at a temperature of 300 ° C., and the degreasing time is 5 h. Was 115.5 mAh / g. However, the sample degreased at a temperature of 200 ° C. or higher had a large decrease in discharge capacity as the C rate increased. On the other hand, it was shown that the sample dried at a temperature of 80 ° C. was not easily affected by the increase in C rate, and the rate of decrease in discharge capacity was small.

Reference Example 250 g of positive electrode waste material cut to 10 mm square and 529 g of balls were placed in a 1 L ball mill reactor, 0.3 L of N-methyl-2-pyrrolidone was added as a polar solvent, and the mixture was stirred at a liquid temperature of 30 ° C. for 3 hours. The active material, conductive material and binder were peeled from the foil. As the ball mill ball, an iron ball coated with a fluorine resin having a spherical diameter of 10 mm was used. The slurry separated into the Al foil and the active material was passed through a sieve (aperture 53 μm) and separated into an Al foil (on the sieve) and a polar solvent slurry. The entire amount of the obtained polar solvent slurry was dried at 80 ° C., and then the binder and the conductive material were degreased in increments of 100 ° C. from 300 ° C. to 700 ° C. for 5 h. To obtain a positive electrode active material powder. A diffraction diagram obtained by performing powder X-ray diffraction on the obtained positive electrode active material powder is shown in FIG. The positive electrode active material powder recovered from the positive electrode waste material changed the quality of the positive electrode active material by heating in a region exceeding 400 ° C. Cationic mixing occurs when the temperature exceeds 400 ° C., and nickel oxide is separated from lithium nickelate when heated above 500 ° C. Further, when heating was performed at 600 ° C. or higher, a reaction in which lithium in lithium nickelate was taken into lithium manganate occurred. Therefore, applying thermal energy in a high temperature region causes deterioration of the active material. In particular, in the positive electrode active material in which a plurality of active materials are mixed, the movement of Li between the active materials proceeds, and thus the electrode is deactivated. Occur.

  According to the present invention, it is easy to peel off the positive electrode substrate and the active material, and in the process of recovering the positive electrode active material from the positive electrode waste material, the heat energy in the high temperature region is not consistently applied, so that it is high by a simpler method. It is possible to regenerate the positive electrode plate maintaining the performance.

Claims (7)

The positive electrode active material is obtained by rolling and stirring the positive electrode waste material in a polar solvent to peel off the active material, the conductive material and the binder from the substrate, and removing the substrate to obtain a polar solvent slurry containing the active material, the conductive material and the binder. A method for producing a material slurry. The manufacturing method of the positive electrode active material slurry of Claim 1 which peels an active material, a electrically conductive material, and a binder from a board | substrate in a polar solvent whose liquid temperature is 80 degrees C or less. The method for producing a positive electrode active material slurry according to claim 1, wherein the polar solvent is N-methyl-2-pyrrolidone. The manufacturing method of the positive electrode active material slurry in any one of Claims 1-3 which does not include the process of drying polar solvent slurry. The manufacturing method of the positive electrode active material powder which dries the polar solvent slurry containing the active material, the electrically conductive material, and the binder obtained by the manufacturing method of the positive electrode active material slurry in any one of Claims 1-3. The method for producing a positive electrode active material powder according to claim 5, wherein the drying temperature is 100 ° C. or less. The positive electrode active material slurry obtained by the manufacturing method in any one of Claims 1-4, or the positive electrode compound material containing either the positive electrode active material powder of Claim 5, 5 is applied to a board | substrate, and is dried. A manufacturing method of a board.