JP2017135055A - Powder for separator, slurry for separator, lithium ion battery, and method of manufacturing lithium ion battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a separator used for lithium ion batteries.SOLUTION: A slurry 124 for separators is used in forming an insulating separator interposed between a positive electrode layer and a negative electrode layer of a lithium ion battery. The slurry 124 for separators includes: inorganic oxide particles (for example, silicon dioxide particles) 120; dispersant particles (for example, polyvinyl pyrrolidone particles) 127 for dispersing the inorganic oxide particles 120 in the slurry; a binder 128 for binding the inorganic oxide particles 120; and a solvent 129 for dissolving the binder 128.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a powder for a separator used for a separator of a lithium ion battery, a slurry for the separator, a lithium ion battery, and a method for producing the same.

  With the development of portable electronic devices, small secondary batteries that can be repeatedly charged are used as power supply sources for these portable electronic devices. Among these, lithium ion secondary batteries that have high energy density, long cycle life, low self-discharge property, and high operating voltage are attracting attention. Lithium ion secondary batteries have the advantages described above, and are therefore widely used in portable electronic devices such as digital cameras, notebook personal computers, and mobile phones.

  An electrode group which is a main part of the lithium ion secondary battery is composed of a separator, a positive electrode, and a negative electrode. Since a polyolefin film is used for the separator, heat resistance is low. In order to improve the heat resistance of the separator, there is a method in which a slurry in which heat-resistant fine particles are dispersed is applied to the separator or the electrode. However, since the slurry is fine particles, it easily aggregates.

  Japanese Patent Laid-Open No. 2011-18590 (Patent Document 1) discloses a method of applying a slurry composed of metal hydroxide fine particles, a thickener and a medium to a separator or an electrode for the purpose of preventing aggregation of the slurry for the separator. Is disclosed.

JP 2011-18590 A

  By applying a slurry in which heat-resistant fine particles are dispersed to the separator or the electrode, the heat resistance of the separator or the electrode can be improved. However, in this case, since a new process for applying a slurry in which heat-resistant fine particles are dispersed is added to the current process, there is a problem that the manufacturing cost increases.

Moreover, in the said patent document 1, although the metal hydroxide is used as a heat resistant fine particle, since a metal hydroxide has good affinity with water, water tends to adsorb | suck to the surface of a separator. When a very small amount of water is mixed in the electrolyte of the lithium ion battery, water (H ₂ O) and LiPF ₆ react to generate hydrofluoric acid (HF). Hydrofluoric acid is highly corrosive and may corrode metal parts such as electrode foils and containers that are constituent materials of lithium ion batteries.

  An object of the present invention can improve the reliability of a separator of a lithium ion battery. Moreover, it is providing the technique which can form a separator with little moisture adsorption | suction.

  The above object and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

  Of the embodiments disclosed in the present application, the outline of typical ones will be briefly described as follows.

  The separator powder in one embodiment includes inorganic oxide particles and dispersant particles for dispersing the inorganic oxide particles in the separator slurry.

  The slurry for a separator in one embodiment includes inorganic oxide particles, dispersant particles for dispersing the inorganic oxide particles, a binder for binding the inorganic oxide particles, and a solvent for dissolving the binder. And having.

  In one embodiment, a lithium ion battery includes a positive electrode layer containing a positive electrode active material, a negative electrode layer containing a negative electrode active material, an insulating separator interposed between the positive electrode layer and the negative electrode layer, and lithium ions The separator includes inorganic oxide particles and dispersant particles for dispersing the inorganic oxide particles.

  In one embodiment, a method for manufacturing a lithium ion battery includes: (a) a step of applying an electrode slurry on a metal foil; (b) a step of applying a separator slurry on the electrode slurry; and (c) the electrode. And drying the slurry for separator and the slurry for separator to form an electrode sheet having an electrode film on the metal foil and a separator on the electrode film. Further, the separator slurry used in the step (b) includes inorganic oxide particles, dispersant particles for dispersing the inorganic oxide particles, a binder for binding the inorganic oxide particles, and the binder. And a solvent for dissolving the adhesive.

  Among the inventions disclosed in the present application, effects obtained by typical ones will be briefly described as follows.

  In the manufacturing process of the lithium ion battery, the reliability of the separator can be improved. In addition, moisture adsorption of the separator can be reduced.

It is the schematic which shows an example of schematic structure and an operation principle of the lithium ion battery of embodiment of this invention. It is a conceptual diagram which shows an example of the manufacturing apparatus of the lithium ion battery of embodiment of this invention. FIG. 3 is an enlarged partial cross-sectional view illustrating an example of a structure of an A part illustrated in FIG. 2. FIG. 3 is an enlarged partial cross-sectional view illustrating an example of a structure of a B part illustrated in FIG. 2. It is a graph which shows an example of the density | concentration of the dispersing agent in embodiment of this invention, and the relationship of the viscosity of the slurry for separators. It is a graph which shows an example of the electrical property of the separator in embodiment of this invention. It is a graph which shows an example of the relationship of the moisture adsorption amount of the separator in embodiment of this invention. It is a flowchart which shows an example of the manufacturing procedure of the lithium ion battery of embodiment of this invention.

  In the following embodiments, the description of the same or similar parts will not be repeated in principle unless particularly necessary.

  Further, in the following embodiment, when it is necessary for the sake of convenience, the description will be divided into a plurality of sections or embodiments, but they are not irrelevant to each other unless otherwise specified. The other part or all of the modifications, details, supplementary explanations, and the like are related.

  Also, in the following embodiments, when referring to the number of elements (including the number, numerical value, quantity, range, etc.), particularly when clearly indicated and when clearly limited to a specific number in principle, etc. Except, it is not limited to that specific number. Furthermore, it may be a specific number or more.

  Further, in the following embodiments, the constituent elements (including element steps) are not necessarily indispensable unless otherwise specified and clearly considered essential in principle. Needless to say.

  Further, in the following embodiments, regarding constituent elements and the like, when “consisting of A”, “consisting of A”, “having A”, and “including A” are specifically indicated that only those elements are included. It goes without saying that other elements are not excluded except in the case of such cases. Similarly, in the following embodiments, when referring to the shapes, positional relationships, etc. of the components, etc., the shapes are substantially the same unless otherwise specified, or otherwise apparent in principle. And the like are included. The same applies to the above numerical values and ranges.

  Hereinafter, embodiments will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments, and the repetitive description thereof will be omitted. Further, even a plan view may be hatched for easy understanding of the drawing.

<Structure and operating principle of lithium-ion battery>
FIG. 1 is a schematic diagram showing an example of a schematic configuration and an operating principle of a lithium ion battery according to an embodiment of the present invention.

  In this embodiment, a lithium ion battery is taken up as an example of a secondary battery that is an electricity storage device, and a separator powder and a separator slurry used when forming a separator of a lithium ion battery, and a method of manufacturing a lithium ion battery An apparatus for manufacturing a lithium ion battery will be described.

  First, the structure and operating principle of the lithium ion battery shown in FIG. 1 will be described. As an example of a lithium ion battery, research and development of a large-sized lithium ion battery capable of realizing a high capacity, a high output, and a high energy density, such as an electric vehicle battery and a power storage battery, has been promoted. In particular, in the automobile industry, in order to cope with environmental problems, development of an electric vehicle that uses a motor as a power source and a hybrid vehicle that uses both an engine (internal combustion engine) and a motor as a power source are in progress. . Lithium ion batteries have attracted attention as power sources for such electric vehicles and hybrid vehicles. However, since the lithium ion battery has a high operating voltage and high energy density, sufficient countermeasures against abnormal heat generation due to an internal short circuit or an external short circuit are required.

A lithium ion battery 10 shown in FIG. 1 is a kind of non-aqueous electrolyte secondary battery, and is a secondary battery in which lithium ions 113 in the electrolyte are responsible for electrical conduction. Cathode material (active material, the electrode material 122a) to the lithium metal oxide (e.g., Li (MnCoNiO _X)) using the negative electrode material (active material, the electrode material 122b) carbon material graphite, etc. (for example, carbon ( C)), and the electrolyte is mainly an organic solvent such as ethylene carbonate and a lithium salt such as lithium hexafluorophosphate. In the battery, lithium ions 113 exit from the positive electrode and enter the negative electrode during charging, and conversely during discharge, the lithium ions 113 exit from the negative electrode and enter the positive electrode.

  The structure of the lithium ion battery 10 includes, for example, a positive electrode plate (an electrode sheet 125a including an electrode foil (metal foil) 110 such as an Al foil) 110 coated with a positive electrode material (electrode material 122a) and a negative electrode material (electrode material 122b). An electrode plate obtained by winding a coated negative electrode plate (electrode sheet 125b including an electrode foil (metal foil) 110 such as Cu foil) and an insulating separator (insulating film) 124a that prevents contact between the positive electrode plate and the negative electrode plate. It has a round body. In the lithium ion battery 10, the electrode winding body is inserted into the outer can 20, and an electrolyte solution 114 (for example, organic solvent + lithium salt) is injected into the outer can 20.

  That is, in the lithium ion battery 10, a positive electrode plate (electrode sheet 125a) obtained by applying a positive electrode material to an electrode foil (metal foil) 110a, and a negative electrode plate (electrode sheet 125b) obtained by applying a negative electrode material to the electrode foil (metal foil) 110b. Are formed in a band shape, and are wound in a cross-sectional spiral shape via the separator 124a so that the positive electrode plate and the negative electrode plate formed in a band shape are not in direct contact with each other, thereby forming the electrode winding body.

  In the following description, the positive electrode sheet 125a and the negative electrode sheet 125b are collectively referred to as an “electrode sheet 125”. The positive electrode foil 110a and the negative electrode foil 110b are collectively referred to as “electrode foil 110”. Furthermore, the electrode slurry 122a which is a positive electrode material and the electrode slurry 122b which is a negative electrode material are collectively referred to as an “electrode material 122”. A paste-like material applied on the base material or the electrode film (positive electrode layer, negative electrode layer) 126 for forming the separator 124a is referred to as “separator slurry (insulating material) 124”.

<Lithium-ion battery manufacturing equipment>
An electrode sheet manufacturing apparatus (hereinafter referred to as a lithium ion battery manufacturing apparatus) constituting the lithium ion battery of this embodiment will be described. 2 is a conceptual diagram showing an example of a lithium-ion battery manufacturing apparatus according to an embodiment of the present invention, FIG. 3 is an enlarged partial cross-sectional view showing an example of the structure of part A shown in FIG. 2, and FIG. 4 is shown in FIG. It is an expanded partial sectional view which shows an example of the structure of B part.

  The configuration of the lithium ion battery manufacturing apparatus shown in FIG. 2 will be described. The lithium ion battery manufacturing apparatus shown in FIG. 2 is an apparatus for manufacturing the electrode sheet 125 constituting the lithium ion battery 10 shown in FIG. An apparatus for manufacturing a lithium ion battery includes a transport unit that transports an electrode foil 110 (also referred to as a current collector foil) 110 that is a metal foil, and a slurry-like electrode material (for electrodes) on a surface 111 of the electrode foil 110 shown in FIG. A first coating part 108 for applying a slurry 122, and a second coating part 109 for applying a slurry-like insulating material 124 (slurry for separator) onto the electrode material 122 of the electrode foil 110. . In addition, it is preferable that the 1st coating part 108 and the 2nd coating part 109 are one coating part which performs 1st coating and 2nd coating.

  Furthermore, the lithium ion battery manufacturing apparatus includes a drying furnace 130 that is a drying unit that dries the electrode material 122 and the insulating material 124, and a measurement unit 145 that measures the film thickness of the electrode sheet 125. In addition, by drying the electrode material 122 and the insulating material 124 in the drying furnace 130, as shown in FIG. 4, the electrode film 126 formed of the electrode material 122 and the electrode film 126 are formed on the electrode foil 110. And a separator (insulating film) 124a formed of the insulating material 124.

  Moreover, the manufacturing apparatus of a lithium ion battery is a thin plate-like, and the delivery roll 101 which sends out the electrode foil (metal foil) 110 provided with the surface 111 shown in FIG. 3 and FIG. 4 and the back surface 112 of the other side, and an electrode A winding roll 107 for winding the foil 110 is provided. As a result, the electrode foil 110 is transported in the transport direction S while being supported by the plurality of rollers 102, 103, 104, 105, 106 between the feed roll 101 and the take-up roll 107. Here, a plurality of rollers are used to convey the electrode foil 110 at a constant speed, and these plurality of rollers are referred to as a roller conveyance system, that is, a conveyance unit.

  A first coating unit 108, a second coating unit 109, a drying furnace 130, and a measurement unit 145 are provided in order from the delivery roll 101 side to the take-up roll 107 side in the transport path of the electrode foil 110. .

  In the first coating unit 108 shown in FIG. 2, a coater 121 (for example, a slit die coater) that discharges an electrode slurry 122 that is a slurry-like electrode material, and a roller 102 that faces the coater 121 are arranged. The electrode foil 110 to be conveyed passes between the coater 121 and the roller 102. In the first coating unit 108, a predetermined amount of electrode slurry (electrode material) 122 is applied from the coater 121 onto the electrode foil 110.

  The electrode slurry 122 used to form the electrode film 126 that constitutes the electrode of the lithium ion battery 10 shown in FIG. 1 is composed of an active material and a conductive aid that can release and occlude lithium ions 113 by charging and discharging. It is a highly viscous slurry liquid in which powder is kneaded and prepared with a binder (binder) and a solvent for binding these powders.

  On the other hand, the second coating unit 109 is provided with a coater (for example, a slit die coater) 123 that discharges a separator slurry 124 that is a slurry-like insulating material, and a roller 103 that faces the coater 123. The conveyed electrode foil 110 passes between the coater 123 and the roller 103. In the second coating unit 109, a predetermined amount of separator slurry 124 is applied from the coater 123 onto the electrode slurry 122 on the electrode foil 110. That is, the separator slurry 124 is laminated on the electrode slurry 122 on the electrode foil 110 as shown in FIG.

  In the drying furnace 130, the electrode slurry 122 and the separator slurry 124 on the conveyed electrode foil 110 are heated and solidified. That is, the electrode slurry 122 is heated with hot air to form the electrode film 126 shown in FIG. 4, and the separator slurry 124 is heated to become the separator 124a. Thereby, the electrode film 126 and the separator 124a are laminated on the electrode foil 110 to form the electrode sheet 125.

  In addition, the measurement unit 145 includes a micrometer 142 and a roller 106 that faces the micrometer 142. Thereby, in the measurement part 145, the micrometer 142 measures the total film thickness including the electrode film 126 and the separator 124a in the conveyed electrode sheet 125.

<Separator powder>
FIG. 5 is a graph showing an example of the relationship between the concentration of the dispersant and the viscosity of the separator slurry in the embodiment of the present invention.

  The separator powder of the present embodiment is a powder (powder) included in the separator slurry 124 (see FIG. 3) forming the separator 124a of the lithium ion battery 10 shown in FIG.

  In the present embodiment, the result of evaluating the case where the separator powder includes the inorganic oxide particles 120 shown in FIG. 3 and the dispersant particles 127 for dispersing the inorganic oxide particles 120 in the slurry. explain. Here, fine particles of silicon dioxide were used as the inorganic oxide particles 120, and fine particles of polyvinyl pyrrolidone (PVP) were used as the dispersant particles 127. The added amount of the dispersant particles 127 is 0.3 wt% to 3.0 wt% with respect to the inorganic oxide particles 120. As a comparative example, when the dispersant particles 127 are not included, the concentration of the dispersant particles 127 is inorganic. The case of 4.0 wt% and 10.0 wt% with respect to the oxide particles 120 was used, respectively.

  Then, a powder (separator powder) in which inorganic oxide fine particles (inorganic oxide particles 120) and dispersant fine particles (dispersant particles 127) are mixed is formed, and a solvent (solvent 129 shown in FIG. 3) is formed. ) And N-methyl-2-pyrrolidone (NMP) as a binder, and polyvinylidene fluoride (PVDF) as a binder 128 are added and kneaded to form a separator slurry 124. The formed separator slurry 124 is put in a glass container, and the presence or absence of a precipitate is observed when left for 1 hour. The results are summarized in Table 1. When the dispersant particles 127 are not included (when the dispersant concentration is 0 wt%), 1% precipitate is generated, and no slurry is generated in the slurry containing the dispersant (separator slurry 124). Obtained.

  Next, these separator slurries 124 were coated with a slit die coater so that the coating gap was at least twice the slurry film thickness, and the presence or absence of vertical streak defects occurring in the coated slurry film was evaluated. The vertical stripe defect is a coating unevenness defect in which the thickness of the slurry applied due to clogging of the nozzle of the slit die coater becomes non-uniform. Then, in order to determine whether this vertical streak defect was caused by a large coating gap of the slit die coater or caused by aggregation of fine particles in the slit die coater, the tip of the slit die coater was cleaned. The presence or absence of defective vertical muscles was evaluated immediately after. The results are shown in Table 2.

  When the dispersant concentration was 0.3 wt%, 1.0 wt%, and 3.0 wt%, stable coating without occurrence of vertical stripe defects could be achieved. From this result, it can be inferred that by applying the dispersant concentration to 0.3 wt% to 3.0 wt%, it is possible to perform stable application without causing vertical stripe defects.

  Further, when no dispersant was added, no vertical streak defect occurred after cleaning the tip of the slit die coater, which was caused by the aggregation of inorganic oxide particles 120 in the slit die coater. It is thought that the vertical muscle is defective.

  The results of measuring the viscosity of the separator slurry 124 are shown in FIG. According to FIG. 5, when the concentration of the dispersant is in the range of 0.3 wt% to 3.0 wt%, the viscosity of the slurry is greater than 0 Pa · s and 3 Pa · s or less. That is, when the coating gap of the slit die coater is increased, it is understood that the viscosity of the separator slurry 124 needs to be lower than 0 Pa · s and lower than 3 Pa · s.

  From the above results, in the separator powder including the inorganic oxide particles 120 and the dispersant particles 127, the dispersant concentration (the concentration of the dispersant particles 127) is the concentration of the inorganic oxide (the concentration of the inorganic oxide particles 120). ) To 0.3 wt% to 3 wt%. At this time, it is preferable to add silicon dioxide particles as the inorganic oxide particles 120 and polyvinyl pyrrolidone particles as the dispersant particles 127.

  Further, the separator powder may contain a binder for binding the inorganic oxide particles 120, and in this case, it is preferable to use a binder that is easily soluble.

<Separator slurry>
FIG. 6 is a graph showing an example of the electrical characteristics of the separator in the embodiment of the present invention, and FIG. 7 is a graph showing an example of the relationship of the moisture adsorption amount of the separator in the embodiment of the present invention.

  The separator slurry 124 shown in FIG. 3 is formed by the following procedure. The content (concentration) of polyvinyl pyrrolidone (PVP) as the dispersant (dispersant particle 127) is 0.3 wt% with respect to the inorganic oxide (inorganic oxide particle 120), and the inorganic oxide (inorganic oxide particle 120) As a solvent, and N-methyl-2-pyrrolidone (NMP) as a solvent 129 and polyvinylidene fluoride (PVDF) as a binder 128 are kneaded. As a comparative example, a separator is prepared by kneading silicon dioxide fine particles as an inorganic oxide, N-methyl-2-pyrrolidone (NMP) as a solvent, and polyvinylidene fluoride (PVDF) as a binder. Forming a slurry.

First, an electrode slurry (positive electrode slurry) 122a is made of LiMn _1/3 N _1/3 Co _1/3 O ₂ powder as a positive electrode active material, carbon black as a conductive additive, and N- It is formed by kneading methyl-2-pyrrolidone (NMP) and polyvinylidene fluoride (PVDF) as a binder.

  Also, the electrode slurry (negative electrode slurry) 122b was bound with spherical graphite powder as a negative electrode active material, carbon black as a conductive additive, and N-methyl-2-pyrrolidone (NMP) as a solvent. It is formed by kneading polyvinylidene fluoride (PVDF) as an agent.

  Next, a positive electrode with a separator is formed by the following procedure. The electrode slurry 122a is applied by a slit die coater, and the separator slurry 124 is applied by a slit die coater on the state where the electrode slurry 122a is undried (not dried).

  On the other hand, a negative electrode with a separator is formed by the following procedure. The electrode slurry 122b is applied by a slit die coater, and the separator slurry 124 is applied by a slit die coater on the state where the electrode slurry 122b is undried (not dried).

  As a comparative example, an electrode that does not contain a dispersant in the separator slurry is formed by the same procedure.

  And the laminate type cell was formed using the said electrode with a separator, and the presence or absence of the short circuit was evaluated. The evaluation results are shown in Table 3.

  From the results of Table 3, when the dispersant (dispersant particles 127) is contained in at least one of the positive electrode and negative electrode separator slurries (Examples A, B, and C in Table 3), the short circuit of the cell is caused. It turns out that it does not occur. This is an effect due to the addition of the dispersant (dispersant particles 127). Further, when both the positive electrode and the negative electrode separator slurry do not contain the dispersant (dispersant particles 127) (comparative example), a short circuit occurs. This is a result of not adding the dispersant (dispersant particles 127).

  In addition, the battery characteristics of the laminate type cell formed in this embodiment were evaluated. As a comparative example in Table 3, the battery characteristics of a laminate type cell using a sheet separator that is a constituent member of a lithium ion battery and formed in advance in a sheet shape were also evaluated. Here, a discharge curve in the case of a high discharge current (current that discharges 100% in 6 minutes) is shown in FIG. It was found that the discharge capacity of the separator 124a of the present embodiment is larger than that of the above-described sheet separator, and the characteristics are excellent.

  Next, evaluation of the amount of moisture adsorbed on the surface of the above-described positive electrode with a separator will be described. As a comparative example, the amount of moisture adsorbed on the surface of the positive electrode not having the separator layer was also evaluated. The evaluation was performed by a method in which each electrode was vacuum-dried at 120 ° C. for 24 hours, left in a constant temperature and humidity chamber, and a change in the weight of the electrode after a predetermined time was measured.

  The result is shown in FIG. From FIG. 7, it can be seen that the amount of adsorbed water is larger on the positive electrode single film than on the positive electrode film with separator, and therefore the positive electrode with separator of the present embodiment suppresses the adsorption of water. This indicates that there are few hydrophilic molecules on the surface of the separator 124a, which is an effect of using the inorganic oxide particles 120.

  As described above, in the separator slurry 124 of the present embodiment including the inorganic oxide particles 120, the dispersant particles 127, the binder 128, and the solvent 129 as shown in FIG. As described in the item of powder, the concentration of the dispersant (dispersant particle 127) contained in the separator slurry 124 is 0.3 wt% to 3.0 wt% with respect to the concentration of the inorganic oxide particles 120. preferable. Furthermore, it is preferable that the viscosity of the separator slurry 124 at that time is a low viscosity greater than 0 Pa · s and 3 Pa · s or less.

  Further, it is preferable to add silicon dioxide particles as the inorganic oxide particles 120 and polyvinyl pyrrolidone particles as the dispersant particles 127.

<Method for producing lithium ion battery>
FIG. 8 is a flowchart showing an example of the manufacturing procedure of the lithium ion battery according to the embodiment of the present invention.

  Hereinafter, the manufacturing method of a lithium ion battery is concretely demonstrated along the flow shown in FIG.

  Each of the positive electrode and the negative electrode constituting the lithium ion battery 10 shown in FIG. 1 is manufactured by basically the same process, although there are differences in the material of the electrode foil 110 and the material of the film applied to the electrode foil 110. The Below, it demonstrates without dividing each manufacturing process of a positive electrode and a negative electrode. For example, an electrode slurry (electrode material) 122, which will be described later, includes a case where it is a positive electrode material and a case where it is a negative electrode material. Is done. Here, it goes without saying that in the positive electrode manufacturing process, the electrode foil 110 and the coating material made of the positive electrode material are used, and the material used only in the negative electrode manufacturing process is not used. Similarly, in the negative electrode manufacturing process, it is needless to say that the electrode foil 110 and the coating material made of the negative electrode material are used, and the material used only for the positive electrode manufacturing process is not used.

1. Production of electrode plates (positive and negative plates) <Kneading / mixing process>
In the manufacturing process of the lithium ion battery 10 according to the present embodiment, first, the electrode slurry 122 that is an electrode material for forming the positive electrode or the negative electrode of the lithium ion battery 10 is kneaded and mixed.

<First coating process (electrode material)>
Next, the electrode slurry 122, which is the adjusted slurry-like electrode material shown in FIG. 3, is used by using the coater 121 provided in the first coating portion disposed so as to face the roller 102 shown in FIG. A thin and uniform coating is performed on the surface of the film-like electrode foil (metal foil) 110 supplied from the delivery roll 101. In the first coating unit 108, for example, a slit die coater can be used as the coater 121, but another apparatus may be used as an apparatus for applying the electrode slurry 122.

<Second coating process (insulating material)>
Next, the separator slurry 124, which is the slurry-like insulating material shown in FIG. 3, is applied to the electrode slurry using the coater 123 provided in the second coating portion disposed so as to face the roller 103 shown in FIG. Apply thinly and evenly on the surface of 122. Here, for example, a slit die coater can be used for the second coating unit, but another device may be used as a device for coating the separator slurry 124.

  Here, the separator slurry 124 binds the inorganic oxide particles 120 as shown in FIG. 3, the dispersant particles 127 for dispersing the inorganic oxide particles 120, and the inorganic oxide particles 120 as described above. The insulating material includes a binder 128 and a solvent 129 that dissolves the binder 128. The concentration of the dispersant (dispersant particles 127) is preferably 0.3 wt% to 3.0 wt% with respect to the concentration of the inorganic oxide particles 120. Furthermore, it is preferable that the viscosity of the separator slurry 124 at that time is a low viscosity greater than 0 Pa · s and 3 Pa · s or less. Further, it is preferable to add silicon dioxide particles as the inorganic oxide particles 120 and polyvinyl pyrrolidone particles as the dispersant particles 127.

  In addition, it is preferable that a 1st coating process and a 2nd coating process are performed by one coating part. Further, in the second coating step in which the separator slurry 124 is applied on the electrode slurry 122, the separator slurry 124 is applied on the electrode slurry 122 that has not been dried (undried).

<Drying process>
Next, as shown in FIGS. 2 and 3, an electrode foil 110 coated with the electrode slurry 122 in the first coating process and further coated with the separator slurry 124 in the second coating process is prepared. Then, it is conveyed into a drying furnace 130 which is a hot air drying furnace. In the drying furnace 130, the solvent component in the electrode slurry 122 and the separator slurry 124 is heated and evaporated to dry the electrode slurry 122 and the separator slurry 124, and the electrode film 126 shown in FIG. A separator 124a, which is an insulating film, is formed at a time. That is, the coated electrode slurry 122 shown in FIG. 3 becomes the electrode film 126 by the drying process, and the coated separator slurry 124 becomes the separator 124a by the drying process. Accordingly, the electrode shown in FIG. 4 has the electrode film 126 formed by the electrode slurry 122 on the electrode foil (metal foil) 110 and the separator 124a formed by the separator slurry 124 on the electrode film 126. A sheet 125 is formed. That is, a positive electrode plate or a negative electrode plate is formed.

<Film thickness measurement process>
In the measurement unit 145 shown in FIG. 2, the micrometer 142 is used to measure the total film thickness including the electrode film 126 and the separator 124a in the conveyed electrode sheet 125 shown in FIG.

  Thereafter, the electrode sheet 125 is taken up by the take-up roll 107.

<Processing process>
Next, processing such as compression and cutting is performed on the electrode foil 110. Here, an example in which the electrode sheet (positive electrode plate or negative electrode plate) 125 in which the electrode film (positive electrode layer or negative electrode layer) 126 and the separator 124a are formed on one surface (surface 111) of the electrode foil 110 has been described. When manufacturing the electrode sheet 125 in which the electrode film 126 and the separator 124a are formed on both surfaces (the front surface 111 and the back surface 112) of the electrode foil 110, first, <kneading / mixing step is performed on the surface 111 of the electrode foil 110. >, <First coating step (electrode material)>, <second coating step (insulating material)>, <drying step>, and <film thickness measurement step>. Then, before performing <processing process>, the electrode sheet 125 wound up by the winding roll 107 is reversed, and the back surface 112 of the electrode foil 110 is applied again through the same process.

2. Battery cell assembly <winding process>
Next, the positive electrode (the electrode foil 110 and the electrode film 126) and the separator 124a shown in FIG. Similarly, a negative electrode (electrode foil 110 and electrode film 126) and a separator 124a having a size necessary for the battery cell are cut out from the negative electrode plate (electrode sheet 125). Subsequently, the positive electrode having the separator 124a formed on the surface 111 and the negative electrode having the separator 124a formed on the surface 111 are stacked, and then the laminate is combined.

<Welding and assembly process>
Next, a group of positive and negative electrode pairs that are joined together with the separator 124a interposed therebetween is assembled and welded. In this welding / assembly process, for example, an aluminum ribbon is wound around the positive electrode current collecting tab, and the positive electrode current collecting tab is connected to the aluminum ribbon by ultrasonic welding.

<Liquid extraction process>
Next, the welded electrode pair group is placed in the outer can (battery can) 20 shown in FIG.

  As the electrolytic solution 114, a nonaqueous electrolytic solution is used. The lithium ion battery 10 is a battery that performs charging / discharging using insertion of lithium ions 113 into and desorption of lithium ions 113 from the active material, and the lithium ions 113 move through the electrolytic solution. Lithium is a strong reducing agent and reacts violently with water to generate hydrogen gas. Therefore, in the lithium ion battery 10 in which the lithium ions 113 move in the electrolytic solution 114, the aqueous solution cannot be used as the electrolytic solution 114. For this reason, in the lithium ion battery 10, a nonaqueous electrolytic solution is used as the electrolytic solution 114.

<Sealing process>
Next, the battery cell is produced by completely sealing the outer can 20.

<Charging / discharging process>
Next, the formed battery cell is repeatedly charged and discharged.

<Battery cell inspection process>
Next, the battery cell performance and reliability are inspected (for example, the capacity and voltage of the battery cell, and the current and voltage during charging or discharging). Thereby, the battery cell of the lithium ion battery 10 is completed.

3. Module Assembly Next, in the module assembly process, a battery module is configured by combining a plurality of battery cells in series, and a battery module (battery system) is configured by connecting a controller for charge / discharge control (module assembly). . Thereafter, in the module inspection process, the battery module assembled in the module assembly process is inspected for performance and reliability (for example, inspection of the capacity and voltage of the battery module, current and voltage during charging or discharging) (module inspection). ).

  In the assembly of the electrode sheet 125, the case where the separator 124a is formed by applying the separator slurry 124, which is an insulating material, to both the positive electrode sheet 125 and the negative electrode sheet 125 has been described. Alternatively, the separator slurry 124 may be applied to only one of them to form the separator 124a, and these electrode sheets 125 may be wound.

  Thus, the assembly of the lithium ion battery 10 as shown in FIG. 1 is completed. The lithium ion battery 10 of the present embodiment includes a positive electrode layer (positive electrode film 126) including a positive electrode active material, a negative electrode layer (negative electrode film 126) including a negative electrode active material, the positive electrode layer, and the negative electrode layer. Insulating separator 124a interposed between and electrolyte solution 114 to which lithium ions 113 can move.

  The separator 124a includes inorganic oxide particles 120 and dispersant particles 127 for dispersing the inorganic oxide particles 120. The concentration of the dispersant particles 127 is preferably 0.3 wt% to 3 wt% with respect to the concentration of the inorganic oxide particles 120.

  Further, it is preferable that silicon dioxide particles are added as the inorganic oxide particles 120 and polyvinylpyrrolidone particles are added as the dispersant particles 127.

  In the assembly of the lithium ion battery 10 of the present embodiment, the separator slurry 124 to be the separator 124a is applied to the applied electrode slurry 122 in an undried state (the drying process is not performed) with a slit die coater. That is, since the electrode slurry 122 and the separator slurry 124 are applied by the coating unit of the coating apparatus (lithium ion battery manufacturing apparatus), the slurry can be applied in the same coating process.

  As a result, it is not necessary to add a new process for applying the separator slurry.

  Therefore, an increase in manufacturing cost can be suppressed in assembling the lithium ion battery 10.

  When the separator slurry 124 is applied onto the undried electrode slurry 122, a mixed layer in which the electrode slurry 122 and the separator slurry 124 are mixed is generated. When the thickness of the mixed layer is increased, a short circuit is likely to occur. Therefore, it is necessary to reduce the thickness of the mixed layer. In order to reduce the thickness of the mixed layer, it is necessary to increase the coating gap of the slit die coater to more than twice the coating thickness of the slurry and to apply at a low pressure.

  On the other hand, when the coating gap is increased, it is necessary to reduce the viscosity of the slurry in order to maintain the stability of the coating film (thickness uniformity). However, if the viscosity of the slurry is reduced, the fine particles in the slurry Aggregation tends to occur.

  Therefore, in the separator powder and the separator slurry 124 according to the present embodiment, by adding a dispersant (dispersant particles 127) in a range where the viscosity of the slurry is lowered, the coating film thickness is made uniform. A stable coating can be realized.

  Specifically, the viscosity of the separator slurry 124 is set to a low viscosity greater than 0 Pa · s and 3 Pa · s or less. And it is preferable to add polyvinylpyrrolidone particles as the dispersant particles 127.

  As a result, the uneven coating of the slurry can be reduced and the stability of the coating film (thickness uniformity) can be improved. As a result, the reliability of the separator 124a can be improved.

  Further, by adding polyvinyl pyrrolidone particles as the dispersant particles 127 to the separator powder or the separator slurry 124, the thickness of the mixed layer of the electrode slurry 122 and the separator slurry 124 can be reduced. Generation | occurrence | production of a short circuit can be suppressed.

  Further, in the separator powder and separator slurry 124 of the present embodiment, the inorganic oxide particles 120 are added as heat-resistant fine particles. For example, silicon dioxide particles are added as the inorganic oxide particles 120. Thereby, the heat resistance of the separator 124a can be improved and the reliability of the separator 124a can be improved.

  Moreover, since the inorganic oxide particle 120 does not contain water in the molecule, moisture adsorption on the surface of the separator 124a after the drying treatment can be reduced. Thereby, the reliability of the separator 124a can be improved.

  Although the invention made by the present inventors has been specifically described based on the embodiment, the present invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.

  For example, in the above embodiment, in the manufacturing process of the lithium ion battery 10, the electrode slurry (electrode material) 122 is applied (first coating) in the first coating unit 108, and the second coating is continuously performed. Although the case where the separator slurry (insulating material) 124 is applied (second coating) in the processing section 109 has been described, the application of the electrode slurry 122 and the application of the separator slurry 124 may be performed together. For example, using a slit die coater in which two nozzles are integrally formed, the electrode slurry 122 and the separator slurry 124 are simultaneously dropped from the slit die coater to apply the electrode slurry 122 and the separator slurry 124. Also good.

  In the above embodiment, the technical idea of the present invention has been described by taking a lithium ion battery as an example. However, the technical idea of the present invention is not limited to a lithium ion battery. And it can apply widely to an electrical storage device (for example, a battery, a capacitor, etc.) provided with the separator which isolate | separates a positive electrode and a negative electrode electrically.

10 Lithium ion batteries 110, 110a, 110b Electrode foil (metal foil)
120 Inorganic oxide particles 122, 122a, 122b Slurries for electrodes (electrode materials)
124 Slurry for separator (insulating material)
124a Separator 125, 125a, 125b Electrode sheet 126 Electrode film (positive electrode layer, negative electrode layer)
127 Dispersant particles 128 Binder 129 Solvent

Claims (15)

A separator powder included in a separator slurry forming a separator of a lithium ion battery,
Inorganic oxide particles;
Dispersing agent particles for dispersing the inorganic oxide particles in the separator slurry;
A separator powder. In the separator powder according to claim 1,
The density | concentration of the said dispersing agent particle is a powder for separators which is 0.3 wt%-3 wt% with respect to the density | concentration of the said inorganic oxide particle. In the separator powder according to claim 1,
The said inorganic oxide particle is a powder for separators which is a particle | grain of silicon dioxide. In the separator powder according to claim 1,
The dispersing agent particles are particles of polyvinyl pyrrolidone, and are separator powders. In the separator powder according to claim 1,
A separator powder comprising a binder that binds the inorganic oxide particles. A separator slurry for forming a lithium ion battery separator,
Inorganic oxide particles;
Dispersant particles for dispersing the inorganic oxide particles;
A binder for binding the inorganic oxide particles;
A solvent for dissolving the binder,
A separator slurry. The separator slurry according to claim 6,
The concentration of the dispersant particles is 0.3 wt% to 3 wt% with respect to the concentration of the inorganic oxide particles, and the viscosity of the dispersant particles is greater than 0 and 3 Pa · s or less. Slurry. The separator slurry according to claim 6,
The separator slurry, wherein the inorganic oxide particles are silicon dioxide particles. A positive electrode layer containing a positive electrode active material that occludes and releases lithium ions;
A negative electrode layer containing a negative electrode active material that occludes and releases lithium ions;
An insulating separator interposed between the positive electrode layer and the negative electrode layer;
An electrolyte in which the lithium ions can move;
Have
The separator is a lithium ion battery including inorganic oxide particles and dispersant particles for dispersing the inorganic oxide particles. The lithium ion battery according to claim 9,
The lithium ion battery has a concentration of the dispersant particles of 0.3 wt% to 3 wt% with respect to the concentration of the inorganic oxide particles. (A) applying a slurry for electrodes on the surface of the metal foil;
(B) applying an insulating separator slurry on the electrode slurry;
(C) drying the electrode slurry and the separator slurry, an electrode film formed by the electrode slurry on the metal foil, and a separator formed by the separator slurry on the electrode film; Forming an electrode sheet having
Have
The separator slurry used in the step (b) is:
Inorganic oxide particles;
Dispersant particles for dispersing the inorganic oxide particles;
A binder for binding the inorganic oxide particles;
A solvent for dissolving the binder,
A method for producing a lithium ion battery, comprising: In the manufacturing method of the lithium ion battery according to claim 11,
In the step (b), the separator slurry is applied onto the electrode slurry that has not been dried. In the manufacturing method of the lithium ion battery according to claim 11,
The concentration of the dispersant particles is 0.3 wt% to 3 wt% with respect to the concentration of the inorganic oxide particles, and the viscosity of the dispersant particles is greater than 0 and 3 Pa · s or less. Battery manufacturing method. In the manufacturing method of the lithium ion battery according to claim 11,
The method for producing a lithium ion battery, wherein the dispersant particles are polyvinylpyrrolidone particles. In the manufacturing method of the lithium ion battery according to claim 11,
The method for producing a lithium ion battery, wherein the inorganic oxide particles are silicon dioxide particles.

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