JPWO2016111063A1 - Lithium ion battery and method for manufacturing the same, and lithium ion battery manufacturing apparatus - Google Patents

Abstract

A lithium ion battery having a separator having a shutdown function and a heat resistance function is provided. In order to solve the above-described problems, the lithium ion battery of the present invention has a two-layered insulation with a silica particle layer as a lower layer and a polypropylene particle layer as an upper layer on a negative electrode layer formed on the surface of a current collector foil. The layer is formed by a single coating process using an insulating material containing two kinds of fine particles having different specific gravities. Similarly, an insulating layer having a two-layer structure including a silica particle layer as a lower layer and a polypropylene particle layer as an upper layer on the positive electrode layer formed on the surface of the current collector foil includes two kinds of fine particles having different specific gravities. It is formed by a single coating process using an insulating material. The silica particle layer has a heat resistance function, and the polypropylene particle layer has a shutdown function.

Description

  The present invention relates to a lithium ion battery, a manufacturing method thereof, and a lithium ion battery manufacturing apparatus.

  As a background art of this technical field, there is JP-A-2003-045491 (Patent Document 1). This publication includes a positive electrode sheet delivery mechanism, a positive electrode material coating mechanism, a positive electrode forming heating mechanism, an electrolysis and insulating material coating mechanism, an electrolysis and insulator forming heating mechanism, and a negative electrode sheet. Secondary equipped with a state material delivery mechanism, a negative electrode material coating mechanism, a negative electrode formation heating mechanism, an electrolysis / insulation material coating mechanism, an electrolysis / insulator formation heating mechanism, and a winding mechanism A battery manufacturing apparatus is described. The winding mechanism is formed by laminating a positive electrode sheet material to which a positive electrode material and electrolysis and an insulating material are fixed, and a negative electrode sheet material to which a negative electrode material and an electrolysis and insulating material are fixed, to form a predetermined shape. It is a turning mechanism.

JP 2003-054991 A

  Conventionally, an insulating material such as polypropylene (PP) is used for a separator that electrically separates a positive electrode and a negative electrode. By using this insulating material, the separator can have a shutdown function. That is, a separator made of an insulating material such as polypropylene is a porous film, and in a lithium ion battery, an electrolytic solution is held in the pores of the separator to form a lithium ion conduction path between the positive electrode and the negative electrode. . When the lithium ion battery abnormally generates heat, the separator is dissolved and the pores are closed, and lithium ion conduction is blocked. Thereby, the reaction in the lithium ion battery is stopped, and further increase in the lithium ion battery temperature can be prevented.

  However, a separator made of an insulating material such as polypropylene melts at about 180 ° C. For this reason, when the temperature of the lithium ion battery rises to about 200 ° C., the separator melts, a mixed layer is formed at the interface between the separator and the positive electrode or the interface between the separator and the negative electrode, the separator becomes thin, and the positive electrode and the negative electrode A short circuit is likely to occur. Therefore, the separator provided in the conventional lithium ion battery has a problem that it has a shutdown function but is inferior in heat resistance.

  Therefore, the present invention provides a lithium ion battery having a separator having a shutdown function and a heat resistance function.

  In order to solve the above problems, a lithium ion battery according to the present invention mainly includes polypropylene particles having a first specific gravity, and mainly includes an upper layer having a shutdown function and silica particles having a second specific gravity greater than the first specific gravity. And a separator composed of a lower layer having a heat resistance function.

  In addition, the method of manufacturing a lithium ion battery according to the present invention includes a step of applying a slurry-like electrode material on the surface of a current collector foil to form a first coating film, and a slurry on the surface of the first coating film. Forming a second coating film by applying a coating-like insulating material, wherein the insulating material is mixed with polypropylene particles having a first specific gravity and silica particles having a second specific gravity greater than the first specific gravity. ing.

  ADVANTAGE OF THE INVENTION According to this invention, the lithium ion battery which has a separator provided with the shutdown function and the heat-resistant function can be provided.

  Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

1 is a schematic diagram showing an apparatus for manufacturing an electrode plate constituting a lithium ion battery according to Example 1. FIG. 4 is a process diagram of a specific manufacturing process of the lithium ion battery according to Example 1. FIG. 2 is a photograph showing an enlarged cross section of a negative electrode plate after drying according to Example 1. FIG. 3 is a graph showing the concentration distribution of polypropylene in the thickness direction of an insulating layer according to Example 1. FIG. 6 is a schematic diagram illustrating an example of a winding process according to Example 1. FIG. (A) And (b) is principal part sectional drawing which respectively shows the 1st modification of a structure of the electrode winding body by Example 1, and a 2nd modification. 6 is a schematic diagram showing a separator manufacturing apparatus according to Example 2. FIG. 6 is a perspective view schematically showing a configuration of an electrode winding body according to Example 2. FIG. It is a schematic diagram explaining an example of the aspect of the winding process by Example 2. FIG.

  In the following embodiments, when necessary for the sake of convenience, the description will be divided into a plurality of sections or embodiments. However, unless otherwise specified, they are not irrelevant to each other, and one is the other. There are some or all of the modifications, details, supplementary explanations, and the like.

  In the following embodiments, when necessary for the sake of convenience, the description will be divided into a plurality of sections or embodiments. However, unless otherwise specified, they are not irrelevant to each other, and one is the other. There are some or all of the modifications, details, supplementary explanations, and the like.

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

  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.

  In addition, when referring to “consisting of A”, “consisting of A”, “having A”, and “including A”, other elements are excluded unless specifically indicated that only that element is included. It goes without saying that it is not what you do. 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.

  In all the drawings for explaining the following embodiments, parts having the same function are denoted by the same reference numerals, and repeated explanation thereof is omitted. Hereinafter, embodiments will be described in detail with reference to the drawings.

  In the following description, the positive electrode and the negative electrode are collectively referred to as “electrode”, the positive electrode plate and the negative electrode plate are collectively referred to as “electrode plate”, and the positive electrode material and the negative electrode material are collectively referred to as “electrode material”. In the following description, the positive electrode material, the negative electrode material, and the insulating material before the drying process using the drying furnace are substances having fluidity including liquids such as a binder solution and an organic solvent. In the following description, the positive electrode material coated and dried film is described as the positive electrode layer, the negative electrode material coated and dried film as the negative electrode layer, and the insulating material coated and dried film as the insulating layer. The positive electrode layer and the negative electrode layer are collectively referred to as an “electrode layer”. In the following description, “the surface of the current collector foil (current collector plate)” refers only to the front surface, not the entire surface including the front surface and the back surface of the current collector foil.

  In this embodiment, a lithium ion battery will be exemplified as a secondary battery that is an electricity storage device, and a lithium ion battery, a method for manufacturing the lithium ion battery, and a lithium ion battery manufacturing apparatus will be described. However, the present invention is not limited to this.

  In the first embodiment, two or more kinds of fine particles having different specific gravities are mixed with this insulating material in the step of applying a slurry-like insulating material to be a separator constituting the lithium ion battery. Thus, a coating film having a multilayer structure composed of a layer having a shutdown function and a layer having a heat resistance function (insulating layer after drying) is formed by a single coating process.

≪Lithium-ion battery manufacturing equipment≫
The electrode plate manufacturing apparatus constituting the lithium ion battery according to the first embodiment will be described with reference to FIG. FIG. 1 is a schematic diagram showing an apparatus for manufacturing an electrode plate constituting the lithium ion battery according to the first embodiment.

  As shown in FIG. 1, an apparatus for manufacturing an electrode plate constituting a lithium ion battery according to Example 1 includes a current collecting metal foil roll 2 for feeding a current collecting foil (current collecting plate) 1, and a current collecting foil 1. It has a winding roll 3 for winding. The current collector foil 1, which is a thin plate-like metal foil, is conveyed between the current collector metal foil roll 2 and the take-up roll 3 while being supported by a plurality of rollers. Here, a plurality of rollers are used to convey the current collector foil 1 at a constant speed, and these plurality of rollers are referred to as a roller conveyance system, that is, a conveyance unit.

  A die coater 4, a die coater 5, and a drying chamber 6 are arranged in order from the current collecting metal foil roll 2 side to the take-up roll 3 side in the conveyance path of the current collecting foil 1. Further, a back roller 7 a is disposed facing the die coater 4, and a back roller 7 b is disposed facing the die coater 5. The current collector foil 1 to be conveyed passes between the die coater 4 and the back roller 7a, between the die coater 5 and the back roller 7b, and inside the drying chamber 6. Here, the electrode material 9 is supplied from the tank 8 to the die coater 4, and the insulating material 11 is supplied from the tank 10 to the die coater 5.

  In FIG. 1, an electrode material 9 used to form an electrode layer that constitutes an electrode of a lithium ion battery is composed of an active material capable of releasing and occluding lithium ions by charging and discharging, and a conductive auxiliary powder. It is a high-viscosity slurry liquid kneaded and blended with a binder and a solvent for binding.

≪Lithium-ion battery manufacturing method≫
Below, the manufacturing method of a lithium ion battery is demonstrated concretely using FIGS. FIG. 2 is a process diagram of a specific manufacturing process of the lithium ion battery according to the first embodiment. FIG. 3 is a photograph showing an enlarged cross section of the negative electrode plate after drying according to Example 1. FIG. 4 is a graph showing the concentration distribution of polypropylene in the thickness direction of the insulating layer according to the first embodiment. FIG. 5 is a schematic diagram for explaining an example of a winding process according to the first embodiment.

  Each of the positive electrode and the negative electrode constituting the lithium ion battery is basically manufactured by the same process, although there are differences in the material of the current collector foil 1 and the material of the film applied to the current collector foil 1. Therefore, in the following, the manufacturing steps of the positive electrode and the negative electrode will be described without being divided. For example, an electrode material, which is a coating material described later, includes a case where it is a positive electrode material and a case where it is a negative electrode material. In each case, the electrode material is composed of different materials. Here, it goes without saying that, in the positive electrode manufacturing process, a current collector foil and a coating material made of a positive electrode material are used, and a material used only for the negative electrode manufacturing process is not used. Similarly, in the negative electrode manufacturing process, it is needless to say that a current collector foil and a coating material made of a negative electrode material are used and a 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 according to the first embodiment, first, the electrode material 9 for forming the positive electrode or the negative electrode of the lithium ion battery is kneaded and mixed.

<First coating process (electrode material)>
Next, the collected slurry-like electrode material 9 is collected from the current-collecting metal foil roll 2 using the die coater 4 provided in the first coating portion disposed so as to face the back roller 7a. Thinly and uniformly applied on the surface of the foil 1. Here, the electrode material 9 is supplied from the tank 8 to the die coater 4. Below, the film | membrane which consists of the electrode material 9 coated on the surface of the current collection foil 1 by the 1st coating process is called a 1st coating film. For example, a slit die coater can be used for the first coating unit, but another device may be used as a device for coating the electrode material 9.

<Second coating process (insulating material)>
Next, the slurry-like insulating material 11 is thinly and uniformly coated on the surface of the first coating film using the die coater 5 provided in the second coating portion disposed so as to face the back roller 7b. . Here, the insulating material 11 is supplied from the tank 10 to the die coater 5. Below, the film | membrane which consists of the insulating material 11 coated on the surface of the 1st coating film by the 2nd coating process is called a 2nd coating film. 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 insulating material 11.

The insulating material 11 includes two or more kinds of fine particles having different specific gravities, for example, polypropylene (PP) particles and inorganic oxide particles are mixed. The inorganic oxide particles are, for example, silica (SiO ₂ ) particles or alumina (Al ₂ O ₃ ) particles. Further, for example, polyethylene (PE) particles can be used instead of polypropylene particles. Furthermore, the insulating material 11 contains a binder for binding the fine particles, for example, a polyvinylidene fluoride polymer or a rubber polymer. The size of the polypropylene particles is, for example, about 0.1 to 10 μm, and the size of the silica particles is, for example, about 0.1 to 10 μm.

  For example, when the slurry-like insulating material 11 in which two kinds of fine particles having different specific gravities are mixed is applied on the surface of the first coating film, the layer made of fine particles having a relatively low specific gravity becomes the upper layer, and the specific gravity is relatively large. The layer composed of large fine particles becomes the lower layer, and a second coating film having a two-layer structure is formed.

The specific gravity of polypropylene, for example, 0.90~0.91g / cm ³ or so, the specific gravity of polyethylene, for example 0.91~0.92g / cm ³ order. On the other hand, the specific gravity of silica is about 1.8 to 2.1 g / cm ³ , and the specific gravity of alumina is about 3.9 to 4.1 g / cm ³ , for example. Therefore, for example, when a slurry-like insulating material 11 in which polypropylene particles and silica particles are mixed is applied on the surface of the first coating film, a layer made of polypropylene particles having a relatively small specific gravity (hereinafter referred to as a polypropylene particle layer). ) Is an upper layer, and a layer made of silica particles having a relatively large specific gravity (hereinafter referred to as a silica particle layer) is a lower layer, and a second coating film having a two-layer structure is formed.

<Drying process>
Next, the current collector foil 1 coated with the first coating film in the first coating process and further coated with the second coating film in the second coating process is dried in the drying chamber 6 which is a hot air drying furnace. Carry in. In the drying chamber 6, the solvent component in the first coating film and the second coating film is heated and evaporated to dry the first coating film and the second coating film, and the electrode layer and the insulating layer are collectively removed. Form. That is, the first coating film becomes an electrode layer by a drying process, and the second coating film becomes an insulating layer by a drying process. Thereby, the electrode plate which consists of the current collection foil 1 and the electrode layer and insulating layer which were laminated | stacked in order on the single side | surface of the current collection foil 1, ie, a positive electrode plate or a negative electrode plate, is formed, respectively. Thereafter, the electrode plate is wound around the winding roll 3.

  FIG. 3 is an enlarged photograph showing a cross section of the negative electrode plate after drying.

  A negative electrode layer NEL is formed on the surface of the current collector foil 1. The current collector foil 1 is made of, for example, aluminum (Al) or copper (Cu) foil, and the thickness thereof is, for example, about 10 to 20 μm. The negative electrode layer NEL is made of, for example, a graphite material or a carbonaceous material, and the thickness thereof is, for example, about 10 to 500 μm.

  Furthermore, an insulating layer IL is formed on the surface of the negative electrode layer NEL, with the upper layer being a polypropylene particle layer PL and the lower layer being a silica particle layer SL. The thickness of the insulating layer IL is, for example, about 5 to 50 μm.

  The polypropylene particle layer PL has a shutdown function that blocks current. That is, when the lithium ion battery abnormally generates heat, the polypropylene particle layer PL is melted and the pores of the polypropylene particle layer PL are blocked, thereby interrupting the current. However, the polypropylene particle layer PL melts at 180 ° C. or higher.

  However, since the silica particle layer SL that does not melt up to about 1,000 ° C. is formed between the negative electrode layer NEL and the polypropylene particle layer PL, the polypropylene particle layer PL melts at a temperature of 180 ° C. or higher. However, since the silica particle layer SL is present, insulation can be maintained.

  Therefore, by forming the insulating layer IL having the upper layer as the polypropylene particle layer PL and the lower layer as the silica particle layer SL, it has a shutdown function (function of the polypropylene particle layer PL) and a heat resistance function (function of the silica particle layer SL). An insulating layer IL, that is, a separator can be formed. Further, as described in the above <Second coating step (insulating material)>, the polypropylene particle layer PL and the silica particles are simultaneously mixed by mixing the slurry-like insulating material 11 with the polypropylene particles and the silica particles. The layer SL can be applied on the surface of the current collector foil 1. Therefore, the insulating layer IL composed of a layer having a shutdown function (for example, a polypropylene particle layer PL) and a layer having a heat resistance function (for example, a silica particle layer SL) can be formed without increasing the coating process. .

  Here, the negative electrode plate has been described. Similarly, in the positive electrode plate as well, insulation composed of a layer having a shutdown function (for example, a polypropylene particle layer PL) and a layer having a heat resistance function (for example, a silica particle layer SL). A layer IL can be formed.

  FIG. 4 is a graph showing the concentration distribution of polypropylene in the thickness direction of the insulating layer.

  As described above in <Second coating step (insulating material)>, a slurry-like insulating material in which two kinds of fine particles having different specific gravities are mixed is applied to the first coating film (electrode layer after drying). When coated on the surface, the layer composed of fine particles with relatively small specific gravity becomes the upper layer, and the layer composed of fine particles with relatively large specific gravity becomes the lower layer, and a second coating film having a two-layer structure (insulating layer after drying) Is formed. Thereby, for example, as shown in FIG. 3, the insulating layer (the second coating film before drying) has a two-layer structure of the polypropylene particle layer PL having a shutdown function and the silica particle layer SL having a heat resistance function. However, the polypropylene particle layer PL made only of polypropylene particles and the silica particle layer SL made only of silica particles are not completely separated into two layers. In particular, at the interface between the polypropylene particle layer PL and the silica particle layer SL, polypropylene particles and silica particles are mixed.

  As shown in FIG. 4, the polypropylene particles have a concentration distribution in the thickness direction of the insulating layer. That is, the polypropylene particles are hardly contained in the insulating layer on the electrode layer side, and most of them are contained in the insulating layer on the surface side. Further, at the interface between the polypropylene particle layer PL and the silica particle layer SL, the polypropylene particles increase rapidly (silica particles decrease rapidly) as compared with the case of surface segregation. However, at the interface, the polypropylene particles and the silica particles cannot be completely separated, and the polypropylene particles and the silica particles are mixed.

  Therefore, the polypropylene particle layer PL shown in FIG. 3 is not composed only of polypropylene particles, and silica particles are mixed especially at the interface between the polypropylene particle layer PL and the silica particle layer SL. That is, the polypropylene particle layer PL is a layer in which the concentration of polypropylene particles is higher than the concentration of silica particles. Similarly, the silica particle layer SL shown in FIG. 3 is not composed only of silica particles, and particularly, polypropylene particles are mixed at the interface between the polypropylene particle layer PL and the silica particle layer SL. That is, the silica particle layer SL is a layer in which the concentration of silica particles is higher than the concentration of polypropylene particles.

  A two-layer structure in which polypropylene particles and silica particles are completely separated is considered to be superior in terms of a shutdown function and a heat resistance function than a two-layer structure in which polypropylene particles and silica particles are not completely separated. However, even if it is not completely separated, the insulating layer IL is formed by a layer containing a large amount of polypropylene particles having a high effect as a shutdown function and a layer containing a large amount of silica particles having a high effect as a heat resistance function. It can have both a function and a heat resistance function.

<Processing process>
Next, the current collector foil 1 is subjected to processing such as compression and cutting. Here, an example in which an electrode plate (positive electrode plate or negative electrode plate) in which an electrode layer (positive electrode layer or negative electrode layer) and an insulating layer are formed on one surface (front surface) of the current collector foil 1 has been described. When manufacturing an electrode plate in which an electrode layer and an insulating layer are formed on both surfaces (front and back surfaces) of the current collector foil 1, <kneading / mixing step>, <first After performing <Coating process (electrode material)>, <Second coating process (insulating material) process> and <Drying process>, and before <Processing process>, it is wound around a winding roll. The reverse electrode plate is reversed, and the back surface of the current collector foil 1 is applied again through the same process.

2. Battery cell assembly <winding process>
Next, a positive electrode (current collector foil 1 and positive electrode layer) and an insulating layer having a size required for the battery cell are cut out from the positive electrode plate. Similarly, a negative electrode (current collector foil 1 and negative electrode layer) and an insulating layer having a size necessary for the battery cell are cut out from the negative electrode plate. Subsequently, after superposing a positive electrode having an insulating layer formed on the surface thereof and a negative electrode having an insulating layer formed on the surface thereof, the laminate is bonded together.

  FIG. 5 is a schematic diagram for explaining an example of the aspect of the winding process.

  The positive electrode PER includes a current collector foil 1 and positive electrode layers PEL formed on both surfaces of the current collector foil 1, and an insulating layer PIL is formed on the positive electrode layer PEL. The negative electrode NER includes a current collector foil 1 and negative electrode layers NEL formed on both surfaces of the current collector foil 1, and an insulating layer NIL is formed on the negative electrode layer NEL. Here, the insulating layer PIL is a layer having a shutdown function (for example, a polypropylene particle layer PPL), and a layer having a heat resistance function (for example, a silica particle layer PSL) positioned between the layer having the shutdown function and the positive electrode layer PEL. It consists of. Similarly, the insulating layer NIL includes a layer having a shutdown function (for example, a polypropylene particle layer NPL), and a layer having a heat resistance function (for example, a silica particle layer NSL) positioned between the layer having a shutdown function and the negative electrode layer NEL. It consists of.

  A positive electrode PER having an insulating layer PIL formed on the surface thereof and a negative electrode NER having an insulating layer NIL formed on the surface thereof are stacked and wound around the axis CR, so that the electrode winding body WRF is obtained. It is formed. In this case, a layer having a heat resistance function (for example, a silica particle layer PSL), a layer having a shutdown function (for example, a polypropylene particle layer PPL), and a layer having a shutdown function (for example, polypropylene) between the positive electrode layer PEL and the negative electrode layer NEL. A separator composed of a particle layer NPL) and a layer having a heat resistance function (for example, a silica particle layer NSL) can be sandwiched. Thereby, a separator having a shutdown function and high heat resistance can be obtained.

  In FIG. 5, each of both surfaces of the current collector foil 1 is composed of a layer having a shutdown function (for example, a polypropylene particle layer PPL) and a layer having a heat resistance function (for example, a silica particle layer PSL) via the positive electrode layer PEL. An insulating layer PIL having a layer structure was formed. Similarly, a two-layer structure including a layer having a shutdown function (for example, a polypropylene particle layer NPL) and a layer having a heat resistance function (for example, a silica particle layer NSL) on both surfaces of the current collector foil 1 via the negative electrode layer NEL. An insulating layer NIL was formed. And although the electrode winding body WRF formed by winding these was illustrated, the structure of the electrode winding body WRF is not limited to this.

  For example, as shown in FIG. 6A, on the positive electrode PER side, a layer having a shutdown function (for example, a polypropylene particle layer PPL) and a layer having a heat resistance function (for example, a silica particle layer PSL) are formed on the positive electrode layer PEL. An insulating layer PIL having a two-layer structure is formed. On the other hand, on the negative electrode NER side, an insulating layer NIL having a one-layer structure made of a layer having a heat resistance function (for example, a silica particle layer NSL) is formed on the negative electrode layer NEL. And an electrode winding body can also be formed by winding these.

  Also in this case, between the positive electrode layer PEL and the negative electrode layer NEL, a layer having a heat resistance function (for example, a silica particle layer PSL), a layer having a shutdown function (for example, a polypropylene particle layer PPL), and a layer having a heat resistance function (for example, silica) Since the separator SP made of the particle layer NSL) can be sandwiched, a separator SP having a shutdown function and high heat resistance can be obtained.

  Further, as shown in FIG. 6B, on the positive electrode PER side, a layer having a shutdown function (for example, a polypropylene particle layer PPL) and a layer having a heat resistance function (for example, a silica particle layer PSL) are formed on the positive electrode layer PEL. An insulating layer PIL having a two-layer structure is formed. On the other hand, only the negative electrode layer NEL is formed on the negative electrode NER side without forming an insulating layer. And an electrode winding body can also be formed by winding these.

  In this case, a layer having a heat resistance function between the positive electrode layer PEL formed on the surface of the current collector foil 1 of the positive electrode PER and the negative electrode layer NEL formed on the surface of the current collector foil 1 of the negative electrode NER. A separator SP composed of (for example, a silica particle layer PSL) and a layer having a shutdown function (for example, a polypropylene particle layer PPL) is sandwiched. That is, a layer having a heat-resistant function is not formed between a layer having a shutdown function (for example, a polypropylene particle layer PPL) and the negative electrode layer NEL, and a layer having a shutdown function at a temperature of 180 ° C. or higher, for example, polypropylene. The particle layer may melt, and a mixed layer may be formed at the interface between the layer having a shutdown function (for example, the polypropylene particle layer PPL) and the negative electrode layer NEL. However, since the layer having the shutdown function (for example, the polypropylene particle layer PPL) also includes, for example, silica particles (see FIG. 4), the insulating layer is formed by mixing only the polypropylene particles, for example, with the insulating material. Than, heat resistance improves.

<Welding and assembly process>
Next, a group of electrode pairs of a positive electrode PER and a negative electrode NER, which are joined together with a separator 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 battery can, and then an electrolytic solution is injected.

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

As the electrolyte of the non-aqueous electrolyte, for example, LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiB (C ₆ H ₅ ) ₄ , CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, or a mixture thereof is used. can do. As the organic solvent, for example, ethylene carbonate, dimethyl carbonate, propylene carbonate, diethyl carbonate, ethyl methyl carbonate, or the like can be used. Further, examples of the organic solvent include 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, diethyl ether, sulfolane, methyl Sulfolane, acetonitrile or propionitrile can be used. Furthermore, as the organic solvent, the above-mentioned mixed liquid of organic solvents can be used.

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

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

<Single 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 a lithium ion battery, ie, a single battery, is completed.

≪Each material of lithium ion battery≫
Next, each material used for manufacturing the lithium ion battery according to the first embodiment will be described.

  As the positive electrode active material used in Example 1, a spinel-structure lithium-containing composite oxide containing lithium cobaltate or Mn (manganese), or Ni (nickel), Co (cobalt), or Mn (manganese) is used. A composite oxide or the like can be used. Moreover, olivine type compounds, such as olivine type iron phosphate, can also be used for a positive electrode active material. However, the positive electrode active material is not limited to these materials, and other materials may be used. Since the lithium-containing composite oxide having a spinel structure containing Mn (manganese) is excellent in thermal stability, for example, a highly safe battery can be configured.

Further, as the positive electrode active material, only a lithium-containing composite oxide having a spinel structure containing Mn (manganese) may be used, but other positive electrode active materials may be used in combination. Examples of the other positive electrode active material include an olivine type compound represented by Li ₁ + xMO ₂ (−0.1 <x <0.1). Examples of the metal M in this formula include Co (cobalt), Ni (nickel), Mn (manganese), Al (aluminum), Mg (magnesium), Zr (zirconium) or Ti (titanium).

Further, a lithium-containing transition metal oxide having a layered structure can be used for the positive electrode active material. Specific examples of the lithium-containing transition metal oxide having a layered structure, LiCoO ₂ or _{LiNi 1 -xCo x -yAl y O 2} (0.1 ≦ x ≦ 0.3,0.01 ≦ y ≦ 0.2) such as Is mentioned. As the lithium-containing transition metal oxide having a layered structure, an oxide containing at least Co (cobalt), Ni (nickel), and Mn (manganese) can be used. Examples of the oxide containing Co (cobalt), Ni (nickel), and Mn (manganese) include LiMn _1/3 Ni _1/3 Co _1/3 O ₂ , LiMn _5/12 Ni _5/12 Co _1/6 O ₂ or LiNi _3/5 Mn _1/5 Co _1/5 O ₂ .

  For the negative electrode active material used in Example 1, for example, a graphite material such as natural graphite (flaky graphite), artificial graphite, or expanded graphite can be used. Also, as the negative electrode active material, an easily graphitizable carbonaceous material such as coke obtained by firing pitch can be used. In addition, examples of the negative electrode active material include amorphous carbon obtained by low-temperature firing of furfuryl alcohol resin (PFA: Poly Furfuryl Alcohol) or polyparaphenylene (PPP: Poly-Para-Phenylen) and a phenol resin. The non-graphitizable carbonaceous material can be used.

  In addition to the above carbon material, Li (lithium) or a lithium-containing compound can also be used as the negative electrode active material. Examples of the lithium-containing compound include a lithium alloy such as Li—Al or an alloy containing an element that can be alloyed with Li (lithium) such as Si (silicon) or Sn (tin). Furthermore, an oxide-based material such as Sn (tin) oxide or Si (silicon) oxide can also be used for the negative electrode active material. This oxide-based material may not contain Li (lithium).

  The conductive auxiliary agent used in Example 1 is used as an electronic conductive auxiliary agent contained in the positive electrode layer, and is preferably a carbon material such as carbon black, acetylene black, graphite, carbon fiber, or carbon nanotube. Among the carbon materials, acetylene black is particularly preferable from the viewpoint of the effect of the addition amount on the conductivity and the productivity of the positive electrode slurry for coating. This conductive auxiliary agent can also be contained in the negative electrode layer.

  The binder used for the electrode layer of Example 1 preferably contains a polymer for binding the active material and the conductive additive to each other. As the binder material, for example, polyvinylidene fluoride-based polymers, water-soluble polymers such as polyvinyl alcohol and derivatives thereof, or rubber-based polymers are preferably used. The polyvinylidene fluoride polymer is a polymer of a fluorine-containing monomer group containing, for example, 80% by mass or more of vinylidene fluoride whose main component is a monomer. Two or more polymers may be used in combination. Further, the binder can be preferably used in a form dissolved in a solvent or an emulsion in which polymer particles are dispersed in a solvent.

  Examples of the fluorine-containing monomer group for synthesizing the polyvinylidene fluoride-based polymer include vinylidene fluoride or a mixture of vinylidene fluoride and another monomer, and a monomer mixture containing 80% by mass or more of vinylidene fluoride. It is done.

  Examples of the other monomer include vinyl fluoride, trifluoroethylene, trifluorochloroethylene, tetrafluoroethylene, hexafluoropropylene, and fluoroalkyl vinyl ether.

  Examples of the rubber-based polymer include styrene butadiene rubber (SBR), ethylene propylene diene rubber, and fluorine rubber.

  The binder content in the electrode layer, that is, the first coating film is preferably 0.1% by mass or more and 10% by mass or less based on the electrode layer after drying. More preferably, the binder content is 0.3% by mass or more and 5% by mass or less. If the binder content is too small, the mechanical strength of the electrode layer after drying is insufficient, and the electrode layer is peeled off from the current collector foil. Moreover, when there is too much content of a binder, there exists a possibility that the amount of active materials in an electrode layer may reduce and battery capacity may become low.

  In addition to the binder, a thickener for adjusting the viscosity of the electrode material may be used. The thickener is preferably used with a binder provided in the form of an emulsion. Examples of the thickener include ethyl cellulose, hydroxyl ethyl cellulose, carboxymethyl cellulose, or carboxymethyl cellulose sodium salt (CMC-NA) polyacrylic acid soda.

The insulating material used in Example 1 contains two or more kinds of fine particles having different specific gravities. Examples of the fine particles having a relatively small specific gravity include polypropylene (PP: Polypropylene) and polyethylene (PE: Polyethylene). A layer made of these fine particles has a shutdown function. The specific gravity of polypropylene, for example, 0.90~0.91g / cm ³ or so, the specific gravity of polyethylene, for example 0.91~0.92g / cm ³ order. Examples of the fine particles having a relatively large specific gravity include inorganic oxides such as silica (SiO ₂ ) or alumina (Al ₂ O ₃ ), and a layer made of these fine particles has a heat resistance function. The specific gravity of silica is about 1.8 to 2.1 g / cm ³ , and the specific gravity of alumina is, for example, about 3.9 to 4.1 g / cm ³ . Further, a resin is used as a binder for binding fine particles used for the insulating material. As the binder, a polyvinylidene fluoride-based polymer or a rubber-based polymer is preferably used as in the case of the electrode material. Moreover, you may use thickeners, such as carboxymethylcellulose.

  The current collector foil used in Example 1 is not limited to a sheet-like foil, and the base thereof may be a pure metal such as aluminum (Al), copper (Cu), stainless steel, or titanium (Ti). Alternatively, an alloy conductive material can be used. As the current collector foil, for example, a net, a punched metal, a foam metal, a foil processed into a plate shape, or the like is used. The thickness of the conductive substrate constituting the current collector foil is, for example, 5 μm to 30 μm, and more preferably 8 μm to 20 μm.

<< Effects of the first embodiment >>
The effects of the first embodiment will be described below.

  In the step of applying the insulating material 11 to be the separator SP, the surface of the first coating film (electrode layer after drying) is mixed with the slurry-like insulating material 11 by mixing two or more kinds of fine particles having different specific gravities. A second coating film (an insulating layer after drying) having a multilayer structure including a layer having a shutdown function and a layer having a heat resistance function is formed simultaneously. This 2nd coating film is an insulating layer used as separator SP which electrically isolates positive electrode PER and negative electrode NER after drying.

  Thereby, since separator SP can have both a shutdown function and a heat-resistant function, the reliability of a lithium ion battery can be improved. In addition, since the layer having the shutdown function and the layer having the heat resistance function can be formed in the same coating process, the number of manufacturing processes is not increased and the TAT (Turn around time) of the electrode plate is increased. Not invited.

  In Example 1 described above, a separator formed on the surface of the electrode by a continuous coating process (<first coating process (electrode material)> and <second coating process (insulating material)>). In the second embodiment, the separator alone and the manufacturing method thereof will be described.

≪Separator manufacturing method≫
Below, the manufacturing method of a separator is demonstrated concretely using FIG. FIG. 7 is a schematic diagram illustrating a separator manufacturing apparatus according to the second embodiment.

  As shown in FIG. 7, the separator manufacturing apparatus is substantially the same as the configuration excluding the first coating section provided in the electrode plate manufacturing apparatus shown in FIG. 1, and thus detailed description thereof is omitted. Further, the insulating material used when manufacturing the separator is also substantially the same as the insulating material described in the first embodiment, and a detailed description thereof will be omitted.

<Coating process>
First, the slurry-like insulating material 11 is thinly and uniformly applied on the surface of the sheet 12 using the die coater 5 provided in the coating portion disposed so as to face the back roller 7. The sheet 12 is, for example, a PET film (polyester film). Here, the insulating material 11 is supplied from the tank 10 to the die coater 5. For example, a slit die coater can be used for the coating unit, but another device may be used as a device for coating the insulating material 11.

As described in Example 1 above, the insulating material 11 contains two or more kinds of fine particles having different specific gravities, for example, polypropylene particles and inorganic oxide particles are mixed. The inorganic oxide particles are, for example, silica (SiO ₂ ) particles or alumina (Al ₂ O ₃ ) particles. Moreover, it can replace with a polypropylene particle and can use a polyethylene particle etc., for example. Furthermore, the insulating material 11 contains a binder for binding the fine particles, for example, a polyvinylidene fluoride polymer or a rubber polymer.

As described in the first embodiment, for example, when the slurry-like insulating material 11 in which two kinds of fine particles having different specific gravities are mixed is applied on the surface of the sheet 12, the particles are formed of fine particles having a relatively small specific gravity. The layer is an upper layer, and the layer made of fine particles having a relatively large specific gravity is the lower layer, and a coating film having a two-layer structure is formed. For example, when a slurry-like insulating material 11 in which polypropylene particles and silica particles are mixed is applied on the surface of the sheet 12, a polypropylene particle layer (specific gravity of polypropylene: 0.90 to 0.91 g / cm ³ ) becomes an upper layer, The silica particle layer (specific gravity of silica: 1.8 to 2.1 g / cm ³ ) is the lower layer, and a coating film having a two-layer structure is formed.

<Drying process>
Next, the sheet | seat 12 which coated the coating film by the coating process is conveyed in the drying chamber 6 which is a hot air drying furnace. In the drying chamber 6, the solvent component in the coating film is heated and evaporated to dry the coating film and form a separator.

  In the case of a separator composed of a polypropylene particle layer and a silica particle layer, the polypropylene particle layer is located in the upper layer, and the silica particle layer is located in the lower layer (sheet 12 side). Here, the polypropylene particle layer is a layer in which the concentration of polypropylene particles is higher than the concentration of silica particles, and has a shutdown function. The silica particle layer is a layer in which the concentration of silica particles is higher than the concentration of polypropylene particles, and has a heat resistance function.

  Therefore, by forming a separator composed of a polypropylene particle layer and a silica particle layer, a separator having a shutdown function (a function of the polypropylene particle layer) and a heat resistance function (a function of the silica particle layer) can be formed. In addition, since the slurry-like insulating material 11 can be mixed with polypropylene particles and silica particles and simultaneously coated on the surface of the sheet 12, it has a shutdown function without increasing the coating process. A separator composed of a layer (for example, a polypropylene particle layer) and a layer having a heat resistance function (for example, a silica particle layer) can be formed.

  Thereafter, the sheet 12 is peeled off, and the separator is wound on the winding roll 3.

≪Configuration of electrode winding body≫
The structure of the electrode winding body according to the second embodiment will be described with reference to FIGS. FIG. 8 is a perspective view schematically showing the configuration of the wound body according to the second embodiment. FIG. 9 is a schematic diagram for explaining an example of a winding process according to the second embodiment.

  The electrode winding body WRF includes a positive electrode PER, a separator SP, and a negative electrode NER that are wound around an axis CR. Cut out the film-shaped positive electrode PER and film-shaped negative electrode NER of the size required for the battery cell, and cut out the film-shaped separator SP for separating the positive electrode PER and the negative electrode NER in the size required for the battery cell. After stacking the separator SP between the positive electrode PER and the negative electrode NER, they are put together.

  Here, the separator SP has a function of preventing electrical contact between the positive electrode PER and the negative electrode NER and allowing lithium ions to pass therethrough. Further, the separator SP has a multilayer structure, and includes, for example, a layer having a shutdown function (for example, a polypropylene particle layer) and a layer having a heat resistance function (for example, a silica particle layer).

  Thus, according to the second embodiment, a highly reliable separator SP having both a shutdown function and a heat resistance function can be manufactured. Further, since the layer having the heat resistance function and the layer having the shutdown function can be formed by the same coating process, the separator SP can be manufactured without increasing the manufacturing TAT.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, 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.

  The present invention includes at least the following embodiments.

[Appendix 1]
A separator including a plurality of particles having different specific gravities.

[Appendix 2]
In the separator according to appendix 1,
The separator includes first particles having a first specific gravity and second particles having a second specific gravity greater than the first specific gravity,
The separator is
A first layer containing more of the first particles than the second particles;
A second layer containing more of the second particles than the first particles;
Have

[Appendix 3]
In the separator described in Appendix 2,
The first particles are polypropylene particles or polyethylene particles, and the second particles are inorganic oxide particles.

[Appendix 4]
In the separator described in Appendix 3,
The inorganic oxide particles are silica particles or alumina particles.

[Appendix 5]
In the separator described in Appendix 2,
The first layer has a shutdown function;
The second layer has a heat resistance function.

[Appendix 6]
A separator manufacturing method comprising the following steps:
(A) A step of applying a slurry-like insulating material on the surface of the sheet to form a coating film;
(B) drying the coating film to form a separator made of the coating film on the surface of the sheet;
(C) a step of separating the sheet and the separator;
Here, the insulating material includes a plurality of particles having different specific gravities.

[Appendix 7]
In the method for manufacturing a separator according to appendix 6,
The insulating material includes polypropylene particles or polyethylene particles and inorganic oxide particles.

[Appendix 8]
In the method for manufacturing a separator according to appendix 7,
The inorganic oxide particles are silica particles or alumina particles.

[Appendix 9]
In the method for manufacturing a separator according to appendix 6,
The insulating material includes first particles having a first specific gravity, and second particles having a second specific gravity greater than the first specific gravity,
The spacer is
A first layer containing more of the first particles than the second particles;
A second layer containing more of the second particles than the first particles;
Have

[Appendix 10]
In the method for manufacturing a separator according to appendix 9,
The first layer has a shutdown function;
The second layer has a heat resistance function.

1 Current collector foil (current collector plate)
2 Current collecting metal foil roll 3 Scatter roll 4, 5 Die coater 6 Drying chamber 7, 7a, 7b Back roller 8 Tank 9 Electrode material 10 Tank 11 Insulating material 12 Sheet IL Insulating layer CR Axis core NEL Negative electrode layer NER Negative electrode NIL Insulating Layer NPL polypropylene particle layer NSL silica particle layer PEL positive electrode layer PER positive electrode PIL insulating layer PL polypropylene particle layer PPL polypropylene particle layer PSL silica particle layer SL silica particle layer SP separator WRF electrode winding body

Claims (13)

A positive electrode having a positive electrode layer formed on the surface of the first current collector foil;
A negative electrode having a negative electrode layer formed on the surface of the second current collector foil;
A separator sandwiched between the positive electrode and the negative electrode to insulate the positive electrode and the negative electrode;
An electrolytic solution in which a charge / discharge reaction is performed between the positive electrode and the negative electrode;
A lithium ion battery comprising:
The separator is a lithium ion battery including a plurality of particles having different specific gravities. The lithium ion battery according to claim 1,
The separator includes first particles having a first specific gravity and second particles having a second specific gravity greater than the first specific gravity,
The separator is
A first layer containing more of the first particles than the second particles;
A second layer containing more of the second particles than the first particles, and formed between the positive electrode and the first layer or between the negative electrode and the first layer;
A lithium ion battery. The lithium ion battery according to claim 2,
The lithium ion battery, wherein the first particles are polypropylene particles or polyethylene particles, and the second particles are inorganic oxide particles. The lithium ion battery according to claim 3,
The said inorganic oxide particle is a lithium ion battery which is a silica particle or an alumina particle. The lithium ion battery according to claim 2,
The first layer has a shutdown function;
The second layer is a lithium ion battery having a heat resistance function. (A) a step of applying a slurry-like electrode material on the surface of the current collector foil to form a first coating film;
(B) applying a slurry-like insulating material on the surface of the first coating film to form a second coating film;
(C) The first coating film and the second coating film are dried, and an electrode layer made of the first coating film and an insulating layer made of the second coating film are stacked on the surface of the current collector foil. Forming the process,
Have
The method for manufacturing a lithium ion battery, wherein the insulating material includes a plurality of particles having different specific gravities. In the manufacturing method of the lithium ion battery of Claim 6,
The method for manufacturing a lithium ion battery, wherein the insulating material includes polypropylene particles or polyethylene particles and inorganic oxide particles. In the manufacturing method of the lithium ion battery of Claim 7,
The method for producing a lithium ion battery, wherein the inorganic oxide particles are silica particles or alumina particles. In the manufacturing method of the lithium ion battery of Claim 6,
The insulating material includes first particles having a first specific gravity, and second particles having a second specific gravity greater than the first specific gravity,
The insulating layer is
A first layer containing more of the first particles than the second particles;
A second layer containing more of the second particles than the first particles and formed between the electrode layer and the first layer;
A method for producing a lithium ion battery. In the manufacturing method of the lithium ion battery according to claim 9,
The first layer has a shutdown function;
The method for producing a lithium ion battery, wherein the second layer has a heat resistance function. A transport unit for transporting the current collector foil;
On the surface of the current collector foil, a first coating part that forms a first coating film by applying a slurry-like electrode material;
A second coating portion that forms a second coating film by applying a slurry-like insulating material on the surface of the first coating film;
The first coating film and the second coating film are dried to form an electrode layer made of the first coating film and an insulating layer made of the second coating film on the surface of the current collector foil. A drying section;
With
The said insulating material is a manufacturing apparatus of a lithium ion battery containing several particle | grains from which specific gravity differs mutually. The lithium ion battery manufacturing apparatus according to claim 11,
The said insulating material is a manufacturing apparatus of a lithium ion battery containing a polypropylene particle or a polyethylene particle, and an inorganic oxide particle. In the manufacturing apparatus of the lithium ion battery according to claim 12,
The said inorganic oxide particle is a manufacturing apparatus of a lithium ion battery which is a silica particle or an alumina particle.