JP2011204458A - Positive electrode plate for nonaqueous electrolyte secondary battery, manufacturing method of positive electrode plate for nonaqueous electrolyte secondary battery, and nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode plate for nonaqueous electrolyte secondary battery which has an electrode active material layer constituted without existence of a resin binder and has high output and input characteristics, and provide a manufacturing method of a current collector having the electrode active material layer in which the active material is adhered excellently on the surface of the current collector without using a resin binder and which is hardly separated, and to realize a nonaqueous electrolyte secondary battery having high output and input characteristics.SOLUTION: The electrode active material layer has an active material fixed on the surface of the current collector by jointing the active materials containing lithium, cobalt, nickel, and manganese without using a resin binder.

Description

  The present invention relates to a positive electrode plate used for a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery, a method for producing the positive electrode plate, and a non-aqueous electrolyte secondary battery.

  A non-aqueous electrolyte secondary battery represented by a lithium ion secondary battery has a high energy density and a high voltage, and has a memory effect during charging / discharging (when the battery is charged before it is completely discharged, Since there is no phenomenon in which the capacity decreases, it is used in various fields such as portable devices and large devices. In recent years, the use of secondary batteries has attracted attention in fields where high input / output characteristics are required, such as electric vehicles, hybrid vehicles, and power tools.

  The non-aqueous electrolyte secondary battery includes a positive electrode plate, a negative electrode plate, a separator, and an organic electrolyte. And as said positive electrode plate and negative electrode plate, what is equipped with the electrode active material layer formed by apply | coating the coating composition for electrode active material layer formation to collector surfaces, such as metal foil, is generally used. .

  The electrode active material layer-forming coating composition comprises an active material capable of inserting and releasing lithium ions, a resin binder, and a conductive material (provided that the conductive material is omitted when the active material also exhibits a conductive effect). Or, if necessary, other materials may be used and kneaded and / or dispersed in an organic solvent to prepare a slurry. A method of producing an electrode plate having an electrode active material layer by applying a coating composition for forming an electrode active material layer on the surface of a current collector to form a coating film, then drying and pressing is common. (For example, Patent Document 1 paragraphs [0019] to [0026], Patent Document 2 [Claim 1], paragraphs [0051] to [0055]).

  At this time, the active material contained in the electrode active material layer-forming coating composition is a particulate compound dispersed in the solution, and the current collector surface is simply applied to the current collector surface. Even if the electrode active material layer forming coating composition that does not easily adhere to the resin and does not contain a resin binder is applied to a current collector to form a coating film and then dried to form a film, the film is not collected. It easily peels off from the electric body. That is, the electrode active material is bound via the resin binder and is fixed to the surface of the current collector to form an electrode active material layer. Therefore, the resin binder is essentially an essential component.

  Moreover, the said electrically conductive material is used in order to ensure the electronic conductivity between each active material and collector in an electrode active material layer favorable, and to reduce the volume resistivity of electrode active material layer itself.

JP 2006-310010 A JP 2006-107750 A

  As described above, in recent years, development of large-capacity secondary batteries has been promoted particularly for fields that require high input / output characteristics such as electric vehicles, hybrid vehicles, and power tools. Even in the case of a secondary battery used in a relatively small device of a mobile phone, since the device tends to be multifunctional, improvement in input / output characteristics is expected. On the other hand, in order to improve the input / output characteristics of the secondary battery, it is necessary to reduce the impedance of the battery. This is because a battery with high impedance has a problem that its capacity cannot be fully utilized during high-speed charging.

  In order to reduce the impedance of the secondary battery, it is effective to reduce the impedance of the electrode plate. To date, a method of increasing the electrode area by thinning the electrode active material layer formed on the electrode plate is known. ing. In addition, since non-aqueous electrolytes used for lithium ion secondary batteries generally have higher resistance than aqueous electrolytes, they are thin and wide-area electrodes compared to other batteries such as lead-acid batteries from the beginning of development. A form has been developed in which the distance between the positive electrode and the negative electrode is shortened.

  However, considering the presence of components other than the active material in the electrode active material layer, there is a limit in reducing the thickness of the layer, and the lower limit of the thickness of the electrode active material layer is substantially up to several tens of μm. It was.

  The present inventors paid attention to the presence of a resin binder in the electrode active material layer as one of the factors that make it difficult to reduce the thickness of the electrode active material layer. As described above, the resin binder has been used as an essential component of the electrode active material layer until now, but the presence of the resin binder increases the volume of the electrode active material layer and physically This resulted in an increase in the thickness of the electrode active material layer. Furthermore, the present inventors have a problem that the movement distance of lithium ions and electrons becomes longer due to the presence of the resin binder between the active materials, and the permeability of the electrolytic solution in the electrode active material layer. It has been found that there is a problem that the contact area between the electrolytic solution and the active material becomes small. And it was guessed that the resin binder which causes these problems is one of the negative factors for the high input / output of the electrode plate.

  In view of the above-described situation, the present invention has been achieved particularly for the positive electrode plate among the electrode plates, and has an electrode active material layer configured without depending on the presence of the resin binder, and has high input / output characteristics. A positive electrode plate for a water electrolyte secondary battery is provided, and an active material layer adheres well to the surface of the current collector without using a resin binder, and an electrode active material layer that is difficult to peel off is provided on the current collector surface. It is an object of the present invention to provide a method for manufacturing a positive electrode plate for a non-aqueous electrolyte secondary battery, and to provide a non-aqueous electrolyte secondary battery with high input / output characteristics.

  The inventors of the present invention can further reduce the thickness of the electrode active material layer that is formed by adhering the active materials directly to each other by bonding directly to each other regardless of the presence of the resin binder. It has been found that a positive electrode plate for a non-aqueous electrolyte secondary battery capable of exhibiting very high input / output characteristics can be realized, and a positive electrode plate for a non-aqueous electrolyte secondary battery and the same are used. The present invention which is a non-aqueous electrolyte secondary battery was completed.

  In addition, the present inventors have disclosed a lithium element-containing compound, cobalt, nickel as one of means for fixing the active material to the current collector surface by bonding the active materials without using a resin binder. And a solution in which a metal element-containing compound containing two or more metal elements selected from the group consisting of manganese is dissolved is applied to the surface of the current collector and heated, whereby lithium ions are formed on the surface of the current collector. According to the production of the lithium transition metal composite compound exhibiting the insertion / release reaction as the active material, the generated lithium transition metal composite compound is bonded at least partially and directly to each other and fixed to the current collector surface and peeled off. The present inventors have found that a difficult coating film can be formed, and have completed the invention of a method for producing a positive electrode plate for a non-aqueous electrolyte secondary battery.

That is, the present invention
(1) A positive electrode plate for a nonaqueous electrolyte secondary battery comprising a current collector and an electrode active material layer composed of an active material on at least a part of the surface of the current collector,
The electrode active material layer is composed of an active material containing at least lithium and two or more metal elements selected from the group consisting of cobalt, nickel, and manganese, and the active materials are partially joined to each other. And a layer having a structure in which the active material is continuously present, and a porous layer having voids through which the electrolytic solution can penetrate,
A positive electrode plate for a non-aqueous electrolyte secondary battery, wherein at least a part of the active material contained in the electrode active material layer is bonded to the current collector,
(2) The non-aqueous electrolyte secondary battery according to (1), wherein the electrode active material layer is composed of an active material containing lithium, cobalt, nickel, and manganese as the metal element. Positive electrode plate,
(3) The non-aqueous electrolyte 2 according to (1) above, wherein the active material constituting the electrode active material layer is a lithium transition metal composite oxide or a lithium transition metal composite phosphate compound. Positive plate for secondary battery,
(4) The particle diameters of 20 arbitrarily selected active material particles are measured on the basis of the electron microscope observation of the electrode active material layer, and the arithmetic average value for the 5 points selected in ascending order of the particle diameter is activated. When the average minimum particle size of the material is used, and the arithmetic average value for the five points selected in order of increasing particle size is the average maximum particle size of the active material,
Any one of (1) to (3) above, wherein the average minimum particle size of the active material is 3 nm or more and less than 20 nm, and the average maximum particle size is 20 nm or more and less than 200 nm. The positive electrode plate for a non-aqueous electrolyte secondary battery according to the description,
(5) The positive electrode for a non-aqueous electrolyte secondary battery according to any one of (1) to (4), wherein the electrode active material layer has a thickness of 300 nm to 10 μm. Board,
(6) The above-mentioned (1), wherein the discharge capacity retention rate is 50% or more at a discharge rate of 50C or more, assuming that the discharge capacity retention rate when discharged at a discharge rate of 1C is 100%. To the positive electrode plate for a non-aqueous electrolyte secondary battery according to any one of (5),
(7) An electrode active material layer forming solution containing lithium and containing two or more metal elements selected from the group consisting of nickel, cobalt, and manganese,
The electrode active material layer forming solution is applied onto at least a part of the current collector surface to form a coating film, and then a heat source is installed on the coating film surface side of the current collector on which the coating film is formed. In this state, an electrode active material layer is formed by performing a heat treatment including a heat treatment at a temperature of 150 ° C. or higher to generate a lithium transition metal composite oxide exhibiting a lithium ion insertion / release reaction on the current collector surface. Forming a positive electrode plate for a non-aqueous electrolyte secondary battery, characterized in that
(8) preparing an electrode active material layer forming solution containing lithium and two or more metal elements selected from the group consisting of nickel, cobalt, and manganese and a phosphorus element;
Applying the electrode active material layer forming solution on at least a part of the current collector surface to form a coating film,
Next, a heating process comprising a heating process at a temperature of 200 ° C. or higher in an inert gas or reducing gas atmosphere in a state where a heat source is installed on the coating film side with respect to the current collector on which the coating film is formed. And forming an electrode active material layer by forming a lithium transition metal composite phosphate compound exhibiting a lithium ion insertion / release reaction on the surface of the current collector. Manufacturing method for positive electrode plate,
(9) After the heat treatment is performed by installing the heat source on the coating film surface side and heating the current collector on which the coating film is formed, the heat source is further installed on both surfaces of the current collector. The method for producing a positive electrode plate for a non-aqueous electrolyte secondary battery according to the above (7) or (8), characterized in that the current collector on which a coating film is formed is heated.
(10) A nonaqueous electrolyte secondary battery comprising at least a positive electrode plate, a negative electrode plate, a separator provided between the positive electrode plate and the negative electrode plate, and an electrolyte solution containing a nonaqueous solvent,
The non-aqueous electrolyte secondary battery is characterized in that the positive electrode plate is the positive electrode plate for a non-aqueous electrolyte secondary battery according to any one of (1) to (6) above. Is.

  The positive electrode plate for a non-aqueous electrolyte secondary battery of the present invention can exhibit very high input / output characteristics. It is surmised that at least one of the factors enabling the high input / output of the positive electrode plate for a non-aqueous electrolyte secondary battery of the present invention is as follows. That is, the electrode active material layer in the positive electrode plate of the present invention includes an active material containing two or more metal elements selected from the group consisting of cobalt, nickel and manganese, regardless of the presence of the resin binder. Forms a layer having a structure in which the layers are bonded to each other and a layer fixed to the surface of the current collector. For this reason, it is considered that the movement distance of lithium ions and electrons is shortened and the input / output characteristics are improved as compared with the conventional electrode active material layer using a resin binder. Moreover, the positive electrode plate of the present invention has good film adhesion of the electrode active material layer to the current collector, as in the case of the electrode plate using the conventional resin binder, and thus the film of the electrode active material layer. Good formability.

  Furthermore, the electrode active material layer in the present invention does not have a resin binder that allows the electrolytic solution to permeate well and adversely affect the behavior of lithium ions due to the presence of appropriate voids. Therefore, it is considered that lithium ions can move smoothly, and as a result, high input / output characteristics can be exhibited. In addition, the conduction of electrons between the current collector and the active material is smooth.

  In addition, the production method of the present invention, which is a method for producing a positive electrode plate for a non-aqueous electrolyte secondary battery, disperses an active material in advance in an electrode active material layer-forming coating composition as in the prior art. Unlike the method of applying to the surface of an electric conductor, drying, and press-bonding, an electrode active material layer forming solution containing lithium and containing two or more metal elements selected from the group consisting of nickel, cobalt, and manganese is collected. A method of applying to the body surface and heating is employed. According to this method, a lithium transition metal composite compound that is an active material exhibiting a lithium ion insertion / release reaction is generated on the surface of the current collector. In addition, at this time, the active materials are at least partially joined to each other, are formed on the current collector surface, and are fixed on the current collector surface to form an electrode active material layer, so that a resin binder is not used. An electrode active material layer is formed.

  And if it is a nonaqueous electrolyte secondary battery comprised using the positive electrode plate for nonaqueous electrolyte secondary batteries of the said invention, the improvement of the input / output characteristic of a positive electrode plate will improve the input / output characteristic as a battery. As a result, a non-aqueous electrolyte secondary battery with improved input / output characteristics is provided.

It is a graph which shows the result of the X-ray-diffraction apparatus (XRD) of the electrode active material layer in Example 1 of this invention.

[Positive electrode plate for non-aqueous electrolyte secondary battery]
The positive electrode plate for a non-aqueous electrolyte secondary battery of the present invention (hereinafter sometimes simply referred to as “the positive electrode plate of the present invention”) includes a current collector and at least a part of the active material on the surface of the current collector. An electrode active material layer configured to be fixed by direct bonding is provided. Below, the form of the positive electrode plate for nonaqueous electrolyte secondary batteries of this invention is demonstrated.

(Current collector)
The current collector used in the present invention is not particularly limited as long as it is generally used as a positive electrode current collector of a positive electrode plate for a nonaqueous electrolyte secondary battery. For example, aluminum foil or nickel foil is preferably used.

  The thickness of the current collector is not particularly limited as long as it is a thickness that can generally be used as a current collector for a positive electrode plate for a nonaqueous electrolyte secondary battery, but is preferably 10 to 100 μm, and preferably 15 to 50 μm. It is more preferable.

(Electrode active material layer)
In the electrode active material layer in the present invention, a layer made of a particulate active material is formed on at least a part of the surface of the current collector, and the active materials are partially and directly joined to each other. The porous layer is formed as a porous layer having a layer structure in which the active material is continuously present and having voids through which the electrolytic solution can permeate. Further, at least a part of the active material contained in the electrode active material layer is bonded to the current collector. These states can be confirmed by scanning electron microscope (SEM) observation at a magnification of about 10,000 to 50,000 times. That is, the positive electrode plate for a non-aqueous electrolyte secondary battery in which the electrode active material layer of the present invention is formed on the current collector surface is cut in a direction perpendicular to the current collector surface, and the cut surface is scanned with an electron microscope (SEM). Thus, a layer made of a particulate active material forming an electrode active material layer is observed on the surface of the current collector by observing a photograph at a magnification of about 50,000 times. In addition, it is observed from the photograph that at least a part of the active material contained in the electrode active material layer is directly attached to and bonded to the current collector.

  With respect to the electrode active material layer, “a void through which the electrolyte can permeate” is a void formed around the active material by partially and directly joining each other, and is 50,000 times larger in an electron microscope. When observed at a magnification, it means a void that is observable with the naked eye.

  The electrode active material layer can be analyzed using an X-ray diffractometer (XRD) to analyze the content of the lithium transition metal composite compound contained therein.

FIG. 1 shows the result of analyzing the electrode active material layer using an X-ray diffractometer (XRD) taking Example 1 described later as an example. From FIG. 1, the electrode active material layer is LiNi _{O 2. 33} Co _{O.I. 33} Mn _O.D. It was confirmed to be composed of ₃₃ O ₂ .

  The active material constituting the electrode active material layer in the present invention is a metal compound that exhibits a lithium ion insertion / release reaction, and at least contains lithium and is selected from the group consisting of cobalt, nickel, and manganese (transition metal group) It is comprised from the lithium transition metal complex compound containing 2 or more types of metal elements. The lithium transition metal composite compound may be a so-called binary compound composed of lithium element and two metal elements selected from cobalt, nickel, or manganese, or lithium element, cobalt, nickel Also, a so-called ternary compound composed of three kinds of metal elements of manganese and manganese may be used. Alternatively, in the range not departing from the gist of the present invention, the active material may further contain other metal elements in addition to lithium and two or more metal elements selected from cobalt, nickel or manganese. . Among them, although the reason is not clear, a lithium transition metal composite compound substantially composed of lithium, cobalt, nickel and manganese is particularly preferable as the active material in the present invention as the metal element.

  Examples of the lithium transition metal composite compound include a lithium transition metal composite oxide and a lithium transition metal composite phosphate compound.

Examples of binary lithium transition metal composite oxides include LiCoMnO ₂ , LiMnNiO ₂ , and LiCoNiO ₂ . The ternary lithium transition metal composite oxide is, for example, Li _x1 Co _x2 Ni _x3 Mn _x4 O _y1 . At this time, the number of moles of oxygen bonded to the metal element is not particularly limited because it varies depending on the oxidation state, and the number of moles of the metal element contained is not particularly limited. That is, in the ternary lithium transition metal composite oxide exemplified above, the values of x1 to x4 and y1 may be appropriately selected to be larger than 0.

Examples of binary lithium transition metal composite phosphate compounds include LiMn _0.5 Fe _0.5 PO ₄ and LiCo _0.2 Mn _0.8 PO ₄ . The ternary lithium transition metal composite phosphate compound is, for example, Li _x5 Co _x6 Ni _x7 Mn _x8 (PO ₄ ) _y2 . At this time, the number of moles of the contained metal element is not particularly limited. That is, in the ternary lithium transition metal composite phosphate compound exemplified above, the values of x5 to x8 and y2 may be appropriately selected as values larger than 0.

  In the present invention, the active material means a compound that exhibits a lithium ion insertion / release reaction. Regarding the determination of whether or not the lithium transition metal composite compound constituting the electrode active material layer exhibits a lithium ion insertion / release reaction, a charge / discharge rate characteristic evaluation described below was performed using the manufactured positive electrode plate, and charge / discharge was performed. When showing a reaction, it can be judged that a lithium ion insertion / elimination reaction is shown.

  Since the electrode active material layer in the present invention is formed by bonding the active materials to each other and adhering to the surface of the current collector without using a resin binder, the electrode active material layer is compared with the thickness of the conventional electrode active material layer. It can be formed very thin. More specifically, the electrode active material layer in the present invention can be formed to a thickness of 300 nm or more and 10 μm or less. However, the above description does not exclude the formation of the electrode active material layer in the positive electrode plate of the present invention with a thickness exceeding 10 μm. Further, when it is desired to increase the capacity, the thickness of the electrode active material layer can be appropriately determined. In addition, when forming the electrode active material layer in this invention in thickness exceeding 10 micrometers, it is desirable to add a electrically conductive material to an electrode active material layer formation solution. The thickness of the electrode active material layer is measured by measuring the thickness of the electrode active material layer at 10 points at any location using a micrometer and calculating the average value.

  In the positive electrode plate of the present invention, as described above, the electrode active material layer can be thinned. When the electrode active material layer is thin in this way, the movement distance of electrons moving between the electrode active material particles and the current collector in the electrode active material layer is shortened. This is desirable because it can contribute to the improvement of the input / output characteristics. Moreover, since there is no resin binder in the electrode active material layer in the present invention, compared with the conventional electrode active material layer in which the resin binder is used, the unit volume per unit volume of the electrode active material layer The weight of the active material is increasing. Therefore, even when the electrode active material layer is thinned, it is possible to maintain a good electric capacity.

  The particle size of the active material constituting the electrode active material layer is determined by using an electron micrograph taken at the time of electron microscope observation. That is, the particle size of the active material particles constituting the electrode active material layer is determined from the electron micrograph obtained by the electron microscope observation using image analysis type particle size distribution measurement software (manufactured by Mount Tech Co., Ltd., MAC VIEW). Can do. About the average particle diameter of active material particle | grains, a particle diameter can be measured about 20 particle | grains and it can specify by the arithmetic average value. At this time, 20 particles are arbitrarily selected. In addition, for the average minimum particle size and average maximum particle size of the active material particles, the average maximum particle size is 5 points in order of decreasing particle size, based on the measured values of 20 particle sizes arbitrarily selected. The particle size is calculated by calculating the arithmetic average for each of 5 points in order of increasing particle size. In addition, a 50,000 times magnified photograph is used for the electron micrograph used when calculating the particle size of an active material.

  The size of the particles of the active material constituting the electrode active material layer in the present invention is not particularly limited, but it is smaller than the particle size of a general active material constituting the conventional electrode active material layer. be able to. In order to achieve high input / output of the positive electrode plate, it is preferable that the particle size is small. From this viewpoint, the active material has an average minimum particle size of 3 nm or more and less than 20 nm, and an average maximum particle size of 20 nm or more. It is preferable that it is less than 200 nm. In addition, according to the manufacturing method of the positive electrode plate for nonaqueous electrolyte secondary batteries of this invention mentioned later, an electrode active material layer can be easily comprised with the very small particle size shown above. The average minimum particle size and the average maximum particle size are obtained by measuring 20 particles using an image analysis type particle size distribution measurement software (manufactured by Mount Tech Co., Ltd., MAC VIEW). It is obtained by selecting 5 points in order of increasing diameter and selecting 5 points in order of increasing particle size as the average maximum particle size, and calculating the arithmetic average for each. In the image analysis type particle size distribution measurement software, the particle to be measured is recognized based on the image of the electron microscope observation photograph, the maximum diameter of the recognized particle is measured, and the maximum particle diameter of each of the 20 particles is measured. The value is measured. Furthermore, among these, the five largest values are selected in order and the average maximum particle size is specified by arithmetically averaging those values, and the five smallest values are selected in order and the arithmetic average is calculated. Thus, the average minimum particle size is specified. Specifically, in the example of Example 1 described later, the average particle size of the particles constituting the electrode active material layer was 6 nm and the average maximum particle size was 29 nm.

  In particular, in the present invention, the average minimum particle size of the active material constituting the electrode active material layer is 3 nm or more and less than 20 nm and the average maximum particle size of the active material is 20 nm or more and less than 200 nm. Therefore, it is possible to provide a positive electrode plate having excellent input / output characteristics.

  As described above, according to the present invention in which the particle size of the active material constituting the electrode active material layer can be reduced as compared with the conventional one, the total surface area of the active material per unit volume in the electrode active material layer is compared with the conventional one. Can be increased. Since the total surface area is understood as a contact area between the active material and the electrolytic solution, an increase in the total surface area means that high input / output of the positive electrode plate is promoted, which is preferable.

(Other materials)
The electrode active material layer can be composed of only the active material described above, but may contain further additives within a range not departing from the gist of the present invention. For example, the electrode active material layer of the present invention may appropriately contain a conductive material. In general, by including a conductive material in the electrode active material layer, it is possible to ensure better electronic conductivity between each electrode active material and the current collector in the electrode active material layer, and the volume of the electrode active material layer itself. The resistivity can be lowered efficiently. Even when a conductive material is added, the thickness of the electrode active material layer can be 10 μm or less. Further, by adding the conductive material and increasing the amount of the active material, the thickness of the electrode active material layer may be formed to a thickness exceeding 10 μm. In this case, the thickness of the positive electrode plate of the present invention is easily increased. Capacity can be increased.

  As the conductive material, those usually used for a positive electrode plate for a non-aqueous electrolyte secondary battery can be used, and examples thereof include carbon materials such as carbon black such as acetylene black and ketjen black. The average particle size of the conductive material is preferably about 20 nm to 50 nm. The average particle size is obtained by an arithmetic average obtained from actual measurement using an electron microscope, as in the method of measuring the particle size of the active material. Carbon fiber (VGCF) is known as a different conductive material. The carbon fiber can conduct electricity very well in the length direction and can improve the fluidity of electricity. The fiber length is about 1 μm to 20 μm. Therefore, in addition to the particulate conductive material such as acetylene black described above, the effect of adding the conductive material can be improved by using carbon fiber together. When using a conductive material, it is necessary to keep in mind that the gap in the electrode active material layer is maintained to such an extent that the electrolytic solution can penetrate.

  In addition, the electrode active material layer of this invention is improving the electroconductivity of an electron compared with the conventional electrode active material layer by not using a resin binder. Therefore, in the electrode active material layer according to the present invention, it is possible to reduce the blending amount of the conductive material as compared with the conventional case, or an embodiment in which no conductive material is used is possible. Thus, in the electrode active material layer in which the blending amount of the conductive material is small or the conductive material is not blended practically, the weight of the active material per unit volume in the electrode active material layer is increased.

  As another optional additive, in order to further improve the adhesion between the current collector and the active material, a metal oxide that does not function as an active material may be included in the electrode active material layer. The metal oxide as the additive is not particularly limited, and examples thereof include cobalt oxide, nickel oxide, titanium oxide, zirconium oxide, tin oxide, and manganese oxide.

(Method for evaluating charge / discharge rate characteristics of electrode)
The input / output characteristics of the positive electrode plate of the present invention can be evaluated by determining the discharge capacity retention rate (%). That is, the discharge capacity retention rate is an evaluation of discharge rate characteristics, and it is generally understood that in a positive electrode plate with improved discharge rate characteristics, the charge rate characteristics are also improved. Therefore, when a desirable discharge capacity retention ratio is indicated, it is evaluated that the charge / discharge rate characteristics are improved, and as a result, the input / output characteristics are evaluated as improved. More specifically, the discharge rate 1C is set such that the theoretical value of the discharge capacity (mAh / g) of the active material is completed in 1 hour, and the discharge actually measured at the set discharge rate of 1C. The capacity (mAh / g) is set to a discharge capacity maintenance rate of 100%. The discharge capacity (mAh / g) when the discharge rate is further increased is measured, and the discharge capacity retention rate (%) can be obtained from the following equation (1).

  In the present invention, it is desirable that a discharge capacity maintenance rate of 50% or more is exhibited at a discharge rate of 50C or more. More preferably, it is desirable that a discharge capacity maintenance rate of 50% or more is exhibited at a discharge rate of 100C or more. However, if the discharge rate is 2000 C or higher, a system that can withstand a large current is required, which is not desirable.

  From another point of view, it is desirable that the discharge capacity maintenance rate is high. When the discharge rate is 50 C, the discharge capacity maintenance rate is 50% or more, or 80% or more, and even 100%. It is desirable that the rate be indicated.

  In addition, the said discharge capacity is calculated | required by measuring the discharge capacity of electrode itself with a tripolar coin cell.

[Method for producing positive electrode plate for non-aqueous electrolyte secondary battery]
Next, a method for producing a positive electrode plate for a non-aqueous electrolyte secondary battery of the present invention (hereinafter also simply referred to as “the production method of the present invention”) will be described. In the production method of the present invention, an electrode active material layer forming solution is prepared by dissolving a compound serving as a precursor of an active material in a solvent, and this is applied onto at least a part of the current collector surface. By heating, the active material which is a lithium transition metal complex compound is produced | generated on the collector surface, an electrode active material layer is formed, and the positive electrode plate for nonaqueous electrolyte secondary batteries is manufactured. Specific examples of the lithium transition metal composite compound include a lithium transition metal composite oxide and a lithium transition metal composite phosphate compound. In any case, since the generated compound needs to act as an active material, it shows a lithium ion insertion / release reaction.

One feature of the production method of the present invention is that the resin binder is not substantially added to the electrode active material forming solution, and an active material is generated on the current collector surface in the production process. At this time, a film in which the active material is fixed to the surface of the current collector is formed by utilizing the fact that the particles of the generated active material are partially directly bonded to each other and are in close contact with the current collector surface. It is. Here, in the electrode active material layer forming coating composition used in the conventional manufacturing method, since the resin binder was blended in addition to the active material, when the particle size of the active material to be used becomes small, The phenomenon that the viscosity of the coating composition for forming an electrode active material layer increased and the coating property deteriorated was observed, which was an adverse effect of thinning the electrode active material layer. However, since it is not necessary to add a resin binder to the electrode active material layer forming solution used in the production method of the present invention, the viscosity of the electrode active material layer forming solution may increase and the applicability may decrease. There is no. Therefore, the amount of application to the current collector can be easily set, and the electrode active material layer can be formed in a desired thickness. Therefore, it is easy to reduce the thickness of the electrode active material layer. That is, the film thickness of the electrode active material layer in the positive electrode plate produced in the present invention is not particularly limited, but when a thinner film thickness is desired, it can be formed to a film thickness of 300 nm or more and 10 μm or less. is there.

  Another feature of the production method of the present invention is that, as described above, the particle size of the active material generated on the surface of the current collector is very small. More specifically, the active material can be generated so that the average minimum particle size is 3 nm or more and less than 20 nm and the average maximum particle size is 20 nm or more and less than 200 nm. Reducing the particle size of the active material is effective as an approach for improving the high input / output characteristics of the positive electrode plate. By reducing the particle size of the active material, the total amount of the surface area of the active material contained in the electrode active material layer is increased, and the movement distance of lithium ions inserted and desorbed in the active material in the active material is reduced. Can be small. For this reason, the behavior of lithium ions becomes smoother, and as a result, improvement of the input / output characteristics can be realized. By the way, in the manufacture of a conventional positive electrode plate, a slurry-like coating composition for forming an electrode active material layer in which a resin binder and active material particles are blended is used. There was a tendency for the viscosity of the electrode active material layer forming coating composition to increase as it decreased. This tendency was particularly observed when active material particles having an average particle diameter of 11 μm or less or even smaller were used. Therefore, since the size of the active material particles that can be used is substantially limited, it has been disadvantageous for the above-described thinning of the electrode active material layer or optimization of the behavior of lithium ions. In addition, it has not been technically easy to produce a ternary lithium transition metal composite compound having a particle size of less than 1 μm. On the other hand, in the present invention, as described in the positive electrode plate, even the maximum average particle diameter can be formed much smaller than 11 μm. Therefore, in the positive electrode plate manufactured by the manufacturing method of the present invention, the total surface area of the active material per unit volume in the electrode active material layer can be sufficiently increased, and the input / output characteristics are improved.

  In the production method of the present invention, the reason why the average minimum particle size of the active material can be generated so small as 3 nm or more and less than 20 nm and the average maximum particle size as 20 nm or more and less than 200 nm is not clear, but is presumed as follows. That is, cobalt, nickel, and manganese selected in combination with lithium as the metal elements constituting the active material in the present invention all show relatively close thermal decomposition temperatures when viewed as the raw material compound. . For example, in an air atmosphere, thermal decomposition starts at about 220 ° C. for a cobalt element-containing compound, about 190 ° C. for a nickel element-containing compound, and about 200 ° C. for a manganese element-containing compound. Stay in the difference. Moreover, these temperature differences are not greatly different even in an inert gas or reducing gas atmosphere. Here, in the coating film, two or more metal elements selected from the group consisting of cobalt, nickel and manganese are mixed, and the step of heating the electrode active material layer forming coating layer (hereinafter referred to as “heating step”) In other words, the lithium transition metal composite oxides of various metal elements contained in the coating film do not grow independently of each other due to the closeness of the thermal decomposition temperature, but act on each other as one small lump. (In other words, it is assumed that the active material has a small particle size).

(Active material precursor)
The electrode active material layer forming solution is a solution containing a metal element constituting the active material. The metal element constituting this active material is two or more metal elements selected from the group consisting of cobalt, nickel, and manganese, and lithium. The electrode active material layer forming solution is prepared by using a metal element-containing compound containing a metal element constituting the active material generated on the current collector surface as a precursor of the active material and dissolving it in a solvent. Can do. As a metal element-containing compound, a lithium element-containing compound and two or more metal element-containing compounds each containing one or more metal elements selected from the group consisting of cobalt, nickel or manganese, or cobalt, nickel or manganese And one metal element-containing compound containing two or more selected two or more metal elements. More specifically, the lithium element-containing compound and the metal element-containing compound containing a metal element other than lithium are two or more selected from the group consisting of a cobalt element-containing compound, a nickel element-containing compound, or a manganese element-containing compound. A metal element-containing compound may be selected as an active material precursor and used as an active material precursor, or two or more metals selected from a lithium element-containing compound and cobalt, nickel, or manganese An element-containing metal element-containing compound may be used as an active material precursor, or is selected from cobalt element-containing compounds, nickel element-containing compounds, manganese element-containing compounds, cobalt, nickel or manganese Combination of four types of metal element-containing compounds containing two or more types of metal elements as appropriate A lithium element-containing compound which may be used as an active material precursor.

  Examples of the metal element-containing compound include chlorides, nitrates, sulfates, perchlorates, acetates, bromates and the like containing specific metal elements. Among them, in the present invention, chloride, nitrate, and acetate are preferably used because they are easily available as general-purpose products. In particular, nitrate is preferably used because it has good film forming properties for a wide variety of current collectors.

  Examples of the lithium element-containing compound include lithium citrate tetrahydrate, lithium perchlorate trihydrate, lithium acetate dihydrate, and lithium nitrate.

  On the other hand, the cobalt element-containing compound includes, for example, cobalt (II) chloride hexahydrate, cobalt (II) formate dihydrate, cobalt (III) acetylacetonate, and cobalt (II) acetylacetonate dihydrate. , Cobalt acetate (II) tetrahydrate, cobalt oxalate (II) dihydrate, cobalt nitrate (II) hexahydrate, cobalt chloride (II) ammonium hexahydrate, cobalt nitrite sodium (III) And cobalt (II) sulfate heptahydrate.

  Examples of the nickel element-containing compound include nickel (II) chloride hexahydrate, nickel (II) acetate tetrahydrate, nickel perchlorate (II) hexahydrate, and nickel (II) bromide. Examples thereof include hydrates, nickel (II) nitrate hexahydrate, nickel (II) acetylacetonate dihydrate, and nickel (II) sulfate hexahydrate.

  Examples of the manganese element-containing compound include manganese acetate (III) dihydrate, manganese nitrate (II) hexahydrate, manganese sulfate (II) pentahydrate, and manganese (II) oxalate dihydrate. And manganese (III) acetylacetonate.

  When producing a lithium transition metal composite phosphate compound as an active material, the electrode active material layer forming solution is a solution containing a metal element and a phosphorus element constituting the active material. Here, the metal element constituting the active material is two or more metal elements selected from the group consisting of cobalt, nickel, and manganese, and lithium.

  In addition, in preparing the electrode active material layer forming solution, when using a metal element-containing compound such as a lithium element-containing compound that does not contain a phosphorus element, the electrode active material layer forming solution further contains a phosphorus element. It is necessary to add a compound. The phosphorus element-containing compound is a compound containing at least a phosphorus element. Therefore, the phosphorus element-containing compound may contain a volatile element as an element other than the phosphorus element. Here, the volatile element refers to an element that is vaporized by applying a heating history at a predetermined temperature or higher, and preferred examples include nonmetallic elements such as hydrogen, oxygen, and nitrogen. Phosphorous element-containing compounds can include phosphoric acid compounds, phosphorous acid compounds, etc., phosphoric acid compounds can include phosphoric acid and salts thereof, and phosphorous acid compounds include phosphorous acid. And salts thereof. As the phosphorus element-containing compound, for example, phosphoric acid, phosphorous acid, hypophosphorous acid, diisopropyl phosphite, ammonium phosphate, ammonium phosphite, ammonium hypophosphite and the like can be used. Not.

  In the case of producing a lithium transition metal composite phosphate compound and preparing an electrode active material layer forming solution, when using a metal element-containing compound such as a lithium element-containing compound containing a phosphorus element, Addition of the phosphorus element-containing compound to the material layer forming solution is optional.

  The phosphorus element-containing compound mentioned here excludes those containing a phosphorus element, which are metal element-containing compounds that can be used when producing a lithium transition metal composite phosphate compound.

  For metal element-containing compounds containing phosphorus elements, for example, lithium element-containing compounds such as lithium phosphate, cobalt element-containing compounds such as cobalt phosphate, nickel element-containing compounds such as phosphoric acid Examples of manganese element-containing compounds such as nickel and nickel (II) hypophosphite hexahydrate include manganese phosphate.

When producing Li _a CoNiMnO _b (where a and b are real numbers greater than 0) as the active material on the current collector, a lithium element-containing compound, a cobalt element-containing compound, a nickel element-containing compound, and manganese as main raw materials In the case of using an element-containing compound, a ratio of a lithium element-containing compound and a combination of a cobalt element-containing compound, a nickel element-containing compound, and a manganese element-containing compound (Li: Co: Ni: Mn = X: 1: 1: 1) is not particularly limited, but the molar ratio of the metal elements contained is preferably 2.5 ≦ X <3.5, more preferably 2.8 ≦ X ≦ 3.2. It is more preferable in terms of ensuring lithium ion insertion / extraction.

  The total concentration of the lithium element and the other metal element in the solution containing the lithium element-containing compound and the other metal element-containing compound is 0.01 to 5 mol / L, particularly 0.1 to 2 mol / L. L is preferred. By setting the concentration to 0.01 mol / L or more, the current collector and the active material generated on the surface of the current collector can be satisfactorily adhered, and the active material can be fixed. In addition, by setting the concentration to 5 mol / L or less, it is possible to maintain a viscosity sufficient to allow the electrode active material layer forming solution to be applied to the current collector surface, and to form a uniform coating film. can do. In addition, examples of the metal element-containing compound other than the lithium element-containing compound in the solution include a cobalt element-containing compound, a nickel element-containing compound, and a manganese element-containing compound.

(Other additives)
In addition to the metal element compounds described above, other additives may be added to the electrode active material layer forming solution without departing from the spirit of the present invention. The said electrically conductive material can use the thing similar to the content described in description of the electrode active material layer of this invention.

  When the conductive material is added to the electrode active material layer forming solution, the added amount of the conductive material is 5 parts by weight to 20 parts by weight with respect to 100 parts by weight of the active material generated on the current collector surface. Is desirable. In addition, although the above is not the meaning which excludes adding a conductive material exceeding 20 weight, the electrode active material layer in this invention exhibits electroconductivity fully by use of a 20 weight part or less conductive material. The idea is that you can.

(solvent)
The solvent used for dissolving the lithium element-containing compound and other metal-containing metal element compounds is not particularly limited as long as it can dissolve the metal element-containing compound including the lithium element-containing compound. Although, for example, lower alcohols having a total carbon number of 5 or less such as methanol, ethanol, isopropyl alcohol, propanol, butanol, diketones such as acetylacetone, diacetyl, benzoylacetone, ethyl acetoacetate, ethyl pyruvate, ethyl benzoylacetate, Examples thereof include ketoesters such as ethyl benzoylformate, toluene, and mixed solvents thereof, or those diluted with water.

  Next, the electrode active material layer forming solution prepared as described above is applied to any region of the current collector surface by a conventionally known coating method such as printing, spin coating, dip coating, bar coating, spray coating, etc. To form a coating film. In addition, when the current collector surface is porous, has a large number of irregularities, or has a three-dimensional structure, it can be manually applied in addition to the above method. Note that the current collector used in the present invention is preferable because corona treatment, oxygen plasma treatment, and the like can be performed in advance as necessary to further improve the film forming property of the electrode active material layer.

  The amount of the electrode active material layer forming solution applied to the current collector can be arbitrarily determined according to the use of the positive plate to be produced, etc., but the electrode active material layer in the present invention is very Since it can be formed thinly, when it is desired to reduce the thickness, the electrode active material layer after heating may be thinly applied so as to have a thickness of about 300 nm to 10 μm. As described above, the electrode active material layer-forming coating film containing the metal element compound that is the precursor of the active material is formed by applying the electrode layer forming solution to the current collector.

  Next, the current collector on which the electrode active material layer-forming coating film is formed is heated. At this time, a lithium transition metal composite compound which is an active material is generated on the surface of the current collector by performing a heating step of heating at a temperature equal to or higher than the decomposition temperature of the metal element compound dissolved in the solution. When there is no phosphorus source material such as the above-described phosphorus element-containing compound in the electrode active material layer forming coating film, a lithium transition metal composite oxide can be produced as the lithium transition metal composite compound. When the coating film for forming the electrode active material layer contains a phosphorus element-containing compound as described above that serves as a source of the phosphorus element constituting the phosphate group, a lithium transition metal composite phosphate compound is produced as the lithium transition metal composite compound. can do. The generated active material is substantially free of resin binder, but is bonded to each other and fixed to the current collector surface, so that an electrode active material layer having good adhesion to the current collector can be obtained. . In this manufacturing method, in order to form the said electrode active material layer appropriately, a heat source is installed in the coating-film surface side for the said electrode active material layer formation, It is characterized by the above-mentioned. The method for installing the heat source is not particularly limited, but the heat source device may be installed on the surface side of the electrode active material layer forming coating film, or on a hot plate heated to an appropriate temperature. You may heat by installing in the position which the surface and the coating film surface for electrode active material layer formation contact | connect. The heating method is not particularly limited. In addition to the case where a hot plate is used as a heat source device, for example, whether an oven, a heating furnace, an infrared heater, a halogen heater, a hot air blower, or the like is used as the heat source device. Or a method of using two or more in combination. When the current collector used is planar, it is preferable to use a heating furnace, a hot plate, or the like.

  In this manufacturing method, as described above, after heating the coating film surface side of the current collector, the both surface sides of the current collector may be further heated in a temperature range of 150 ° C to 800 ° C. When heating the both sides, the position where the heat source is installed is, for example, a mode in which a heat source device is installed on the both sides, or a collection in which a coating film for forming an electrode active material layer is laminated in a heating furnace or the like. It includes a mode in which an electric body is installed and both sides are heated in the same environment.

  In addition, the atmosphere in the said heating process is not specifically limited. However, when the generated active material is a lithium transition metal composite oxide, the metal element contained in the active material precursor is thermally melted by carrying out the heating process of the present invention in the air atmosphere. It is preferable because it is easy to oxidize. When producing a lithium transition metal composite oxide as an active material, the heating step may be performed in an atmosphere having a low oxygen concentration or no oxygen, such as a hydrogen atmosphere or a nitrogen atmosphere. When producing a transition metal composite oxide, it is necessary that the compound blended in the electrode active material layer forming solution contains a source of oxygen element that can be used for forming the metal oxide. .

  On the other hand, when producing a lithium transition metal composite phosphate compound as an active material, it is desirable to carry out the heating step in an inert gas atmosphere or a reducing gas atmosphere. In an inert gas atmosphere or a reducing gas atmosphere, the contact between the coating film made of the electrode active material layer forming solution and oxygen is further regulated, and the formation of the lithium transition metal composite phosphate compound is further ensured. In this case, phosphorus derived from the phosphorus element-containing compound contained in the electrode active material layer forming solution by further blending a substance (oxygen element-containing compound) that can be a source of oxygen element in the electrode active material layer forming solution; A lithium transition metal composite phosphate compound can be more easily generated with a metal element derived from a metal element-containing compound and oxygen of the oxygen element-containing compound. Note that argon or nitrogen can be used as the inert gas. As the reducing gas, hydrogen or carbon monoxide can be used.

  Although the heating temperature at the time of carrying out the heating step varies depending on the type of metal element compound used, when producing a lithium transition metal composite oxide as an active material, usually in an air atmosphere (in an oxygen-existing atmosphere), By heating to a temperature range of 150 ° C. to 800 ° C., the metal element-containing compound is favorably decomposed to generate an active material. When a lithium transition metal composite phosphate compound is produced as an active material, the metal element-containing compound can be decomposed satisfactorily by heating in an inert gas or reducing gas atmosphere to a temperature range of 200 ° C. to 800 ° C. To produce an active material.

[Nonaqueous electrolyte secondary battery]
A nonaqueous electrolyte secondary battery is generally configured by providing a positive electrode plate and a negative electrode plate, and a separator such as a porous film made of polyolefin such as polyethylene between them. The container is sealed and manufactured in a state where the container is filled with a non-aqueous electrolyte.

(Electrode plate)
The non-aqueous electrolyte secondary battery of the present invention is particularly characterized in that the positive electrode plate for a non-aqueous electrolyte secondary battery of the present invention described above is used as the positive electrode plate. Conventionally, when the negative electrode plate is made of a carbonaceous material, it has been common to add a large amount of conductive material to the positive electrode plate in order to increase the conductivity of the positive electrode plate accordingly. In addition, since the porosity of the positive electrode plate is reduced and the permeability of the electrolyte solution is reduced, it is difficult to increase the input / output characteristics of the battery. However, since the positive electrode plate of the present invention has excellent input / output characteristics, the non-aqueous electrolyte secondary battery of the present invention using the positive electrode plate as a positive electrode plate does not use a large amount of conductive material as in the prior art, or is conductive. Good conductivity and high input / output characteristics can be exhibited without using any material.

  On the other hand, as a negative electrode plate used for the nonaqueous electrolyte secondary battery of the present invention, a known negative electrode plate used for a conventionally known nonaqueous electrolyte secondary battery can be appropriately selected and used. For example, a copper foil such as an electrolytic copper foil or a rolled copper foil having a thickness of about 5 to 50 μm is used as the current collector, and the electrode active material layer forming coating composition in the negative electrode plate is formed on at least a part of the current collector surface. Is formed by coating, drying, and pressing as necessary. The coating composition for forming an electrode active material layer in the negative electrode plate is generally made of natural graphite, artificial graphite, amorphous carbon, carbon black, or a carbonaceous material obtained by adding a different element to these components. Active materials, or active materials such as lithium metal and its alloys, tin, silicon, and alloys thereof, materials that can insert and desorb lithium ions, resin binders, conductive materials as necessary, etc. It is common for other additives to be dispersed and mixed.

(Non-aqueous electrolyte)
The non-aqueous electrolyte used in the present invention is not particularly limited as long as it is generally used as a non-aqueous electrolyte for a non-aqueous electrolyte secondary battery, but a lithium salt is dissolved in an organic solvent. A non-aqueous electrolyte is preferably used.

Examples of the lithium salt include inorganic lithium salts such as LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAsF ₆ , LiCl, and LiBr; LiB (C ₆ H ₅ ) ₄ , LiN (SO ₂ CF ₃ ) ₂ , LiC ( Organic compounds such as SO ₂ CF ₃ ) ₃ , LiOSO ₂ CF ₃ , LiOSO ₂ C ₂ F ₅ , LiOSO ₂ C ₄ F ₉ , LiOSO ₂ C ₅ F ₁₁ , LiOSO ₂ C ₆ F ₁₃ , and LiOSO ₂ C ₇ F ₁₅ Typical examples include lithium salts.

  Examples of the organic solvent used for dissolving the lithium salt include cyclic esters, chain esters, cyclic ethers, and chain ethers.

  Examples of the cyclic esters include propylene carbonate, butylene carbonate, γ-butyrolactone, vinylene carbonate, 2-methyl-γ-butyrolactone, acetyl-γ-butyrolactone, and γ-valerolactone.

  Examples of the chain esters include dimethyl carbonate, diethyl carbonate, dibutyl carbonate, dipropyl carbonate, methyl ethyl carbonate, methyl butyl carbonate, methyl propyl carbonate, ethyl butyl carbonate, ethyl propyl carbonate, butyl propyl carbonate, propionic acid alkyl ester, Examples include malonic acid dialkyl esters and acetic acid alkyl esters.

  Examples of the cyclic ethers include tetrahydrofuran, alkyltetrahydrofuran, dialkyltetrahydrofuran, alkoxytetrahydrofuran, dialkoxytetrahydrofuran, 1,3-dioxolane, alkyl-1,3-dioxolane, and 1,4-dioxolane.

  Examples of the chain ethers include 1,2-dimethoxyethane, 1,2-diethoxyethane, diethyl ether, ethylene glycol dialkyl ether, diethylene glycol dialkyl ether, triethylene glycol dialkyl ether, and tetraethylene glycol dialkyl ether. It is done.

  As a structure of the non-aqueous electrolyte secondary battery manufactured using the positive electrode plate, the negative electrode plate, the separator, and the non-aqueous electrolyte solution, a conventionally known structure can be appropriately selected and used. For example, the structure which winds a positive electrode plate and a negative electrode plate in the shape of a spiral via the separator like a polyethylene porous film, and accommodates in a battery container is mentioned. As another aspect, a structure in which a positive electrode plate and a negative electrode plate cut into a predetermined shape are stacked and fixed via a separator, and this is housed in a battery container may be employed. In any structure, after the positive electrode plate and the negative electrode plate are stored in the battery container, the lead wire attached to the positive electrode plate is connected to the positive electrode terminal provided in the outer container, while the lead wire attached to the negative electrode plate Is connected to a negative electrode terminal provided in the outer container, and the battery container is further filled with a nonaqueous electrification solution and then sealed to produce a nonaqueous electrolyte secondary battery.

Example 1
An aluminum plate having a thickness of 15 μm was prepared as a current collector, and an electrode active material layer prepared as follows on one side of the current collector in an amount such that the thickness of the finally obtained electrode active material layer was 4 μm The forming solution was applied with a Miya bar to form a coating film for forming an electrode active material layer.

<Preparation of electrode active material layer forming solution>
10.2 g of Li (CH ₃ COO) · 2H ₂ O [molecular weight: 102.02] as a raw material (solute) for generating an active material, and Ni (NO ₃ ) ₂ · 6H ₂ O [molecular weight: 290.8] 9.7 g, Mn (NO ₃ ) ₂ · 6H ₂ O [molecular weight: 287.0] 9.6 g, Co (NO ₃ ) ₂ · 6H ₂ O [molecular weight: 287.0] 9.7 g, acrylic A solution (solvent) obtained by mixing 3 g of resin (Oricox KC210, manufactured by Kyoeisha Chemical Co., Ltd.) and mixing these materials with water and IPA so that the weight ratio is water: isopropyl alcohol (IPA) = 2: 1. In addition to 70g, it was made to melt | dissolve, it stirred over 5 hours at the temperature of 70 degreeC and the rotation speed of 200 rpm with the bioshaker, and the electrode active material layer forming solution was prepared by hold | maintaining at room temperature after that for 24 hours.

<Heating process>
Next, the current collector with the electrode active material layer-forming coating film formed on the surface is brought into close contact with a hot plate heated to 300 ° C. from the side on which the electrode active material-forming coating film is formed, Hold for 10 minutes. After returning to room temperature, it was continuously heated to 600 ° C. in an air atmosphere over 5 hours, kept at 600 ° C. for 5 hours, then cooled to room temperature, then opened to the atmosphere, and the sample was taken out and collected An electrode plate for a non-aqueous electrolyte secondary battery (positive electrode plate) of the present invention in which an appropriate electrode active material layer was laminated as a positive electrode active material layer on the body was obtained. Then, the positive electrode plate was drawn out (cut) into a predetermined size (a disk having a diameter of 15 mm), and the positive electrode body thus obtained was used as Example 1. In the above heating, a hot plate (manufactured by AS ONE) is used to heat the side on which the electrode active material layer-forming coating film is formed, and then an electric furnace is used to heat from both sides of the current collector. A muffle furnace (D90, P90) was used.

<Evaluation of film formability>
In preparing Example 1, the positive electrode plate for a nonaqueous electrolyte secondary battery obtained above was processed to a predetermined size. In this processing operation, the electrode active material layer was peeled off, etc. Thus, the working electrode used in the charge / discharge test described later could be formed. From this, it was confirmed that the film forming property of the electrode active material layer was good. The results are shown in Table 1. Also in the examples and comparative examples described below, the favorable film forming property means that the positive electrode plate can be pulled out without any trouble as described above. On the other hand, when a part of the electrode active material layer is peeled off in the above-mentioned punching process, or the electrode active material falls from the current collector and a disc that can be used as a working electrode of a tripolar coin cell is not formed. It is assumed that the film forming property of the electrode active material layer is poor. In Table 1, in the column showing the evaluation of film forming property, “◯” indicates “film forming property is good” and “x” indicates “film forming property is bad”.

<Electron microscope observation, electrode active material layer thickness, particle size measurement, X-ray diffraction>
Using Example 1, using a scanning electron microscope (SEM) and an X-ray diffractometer (XRD) to observe a cross section cut in a direction perpendicular to the current collector surface at a magnification of 50,000 times, On the surface of the current collector, the electrode active material layer is made of a particulate ternary oxide (LiNi _0.33 Co _0.33 Mn _0.33 O ₂ ) having a thickness of 4 μm and containing lithium. The layer was deposited. Then, it was confirmed that particles of LiNi _0.33 Co _0.33 Mn _0.33 O ₂ were partially and directly joined to each other and voids were formed around the particles. In addition, from the electron micrograph obtained by the electron microscope observation, the particle size of the particles constituting the electrode active material layer was determined using 20 image analysis particle size distribution measurement software (manufactured by Mount Tech Co., Ltd., MAC VIEW). Measured and calculated the arithmetic average of 5 points in ascending order of particle size as the average minimum particle size and 5 points in order of increasing particle size as the average maximum particle size. The particle size was 29 nm (Table 1). The results of XRD analysis are shown in FIG.

Tripolar coin cell production:
Lithium hexafluorophosphate (LiPF ₆ ) is added as a solute to a mixed solvent of ethylene carbonate (EC) / dimethyl carbonate (DMC) (volume ratio = 1: 1), and the concentration of LiPF _{6 as} the solute is 1 mol. The non-aqueous electrolyte was prepared by adjusting the concentration to be / L. Then, Example 1 (15 mm diameter disc, weight of positive electrode active material contained: 1.3 mg / 1.77 cm ² ) prepared as described above as a positive electrode plate was used as a working electrode, and a counter electrode plate and a reference electrode plate A tripolar coin cell was assembled using a metal lithium plate as the electrolyte, the non-aqueous electrolyte prepared above as the electrolyte, and a porous polyethylene sheet as the separator. The example test cell 1 was subjected to the following charge / discharge test.

<Charge / discharge test>
In the example test cell 1, which is a tripolar coin cell prepared as described above, in order to evaluate the charge / discharge rate characteristics of the working electrode, the example test cell 1 was first fully charged as in the following charging test.

Charging test:
Example Test cell 1 was charged at a constant current (72 μA) under a 25 ° C. environment until the voltage reached 4.3 V. After the voltage reached 4.3 V, the voltage was 4.3 V. The current (discharge rate: 1C) was decreased until the current became 5% or less, and the battery was charged at a constant voltage, fully charged, and then suspended for 10 minutes. Here, the “1C” means a current value (current value reaching the discharge end voltage) at which constant current discharge is performed using the tripolar coin cell and discharge is completed in one hour. The constant current is set so that the theoretical discharge amount of 160 mAh / g of LiNi _0.33 Co _0.33 Mn _0.33 O _{2 as} the active material is discharged in one hour at the working electrode in the example test cell 1. It was done.

Discharge test:
Thereafter, the fully charged example test cell 1 was subjected to a constant current (72 μA) (discharge) in an environment of 25 ° C. until the voltage changed from 4.3 V (full charge voltage) to 3.0 V (discharge end voltage). A constant current discharge at a rate of 1 C), the cell voltage (V) on the vertical axis, the discharge time (h) on the horizontal axis, a discharge curve is created, and the working electrode (electrode plate for positive electrode of Example 1) The discharge capacity (mAh) was determined and converted to the discharge capacity (mAh / g) per unit weight of the working electrode.

  Subsequently, with a constant current discharge test at a constant current (72 μA) (discharge rate: 1 C, discharge end time: 1 hour) carried out as described above as a reference, a five times constant current (0.36 mA) (discharge rate: 5C, discharge end time: 12 minutes), 10 times constant current (0.72 mA) (discharge rate: 10 C, discharge end time: 6 minutes), 50 times constant current (3.6 mA) (discharge rate: 50 C, At the end of discharge: 1.2 minutes), a constant current discharge test was conducted in the same manner to determine the discharge capacity (mAh) of the working electrode at each discharge rate. From this, the discharge capacity per unit weight (mAh / g) ) Was converted.

<Calculation of discharge capacity maintenance rate (%)>
In order to evaluate the output characteristics (discharge rate characteristics) of the working electrode, each discharge capacity (mAh / g) per unit weight at each discharge rate obtained as described above is used, and the mathematical formula shown in the above equation 1 is used. The discharge capacity retention rate (%) was determined. The discharge capacity (mAh / g) and discharge capacity retention rate (%) per unit weight obtained by the above discharge test are all shown in Table 2.

(Example 2 and Example 3)
Example 1 with the exception that the coating amount of the electrode active material layer forming solution on the current collector was changed so that the film thickness of the electrode active material layer formed on the current collector became the value shown in Table 1. Similarly, a positive electrode body was prepared and used as Example 2 and Example 3.

About Example 2 and Example 3, film-forming evaluation, electron microscope observation, the film thickness measurement of an electrode active material layer, a particle size measurement, and X-ray diffraction were performed similarly to Example 1. FIG. In the electron microscope observation, it was confirmed that the electrode active material layer was formed on the current collector as in Example 1. Further, by X-ray diffraction, the compound constituting the electrode active material layer _was confirmed to be _{LiNi 0.33 Co 0.33 Mn 0.33 O 2} . Other results are shown in Table 1.

  Similar to Example Test Cell 1, Example Test Cell 2 and Example Test Cell 3 were prepared using Examples 2 and 3, respectively. Then, the charge test and the discharge test were performed in the same manner as in the example test cell 1 except that the constant current at each discharge rate was changed to the values shown in Table 2 using the example test cell 2 and the example test cell 3. Then, the discharge capacity (mAh) of the working electrode at each discharge rate was determined, and the discharge capacity per unit weight (mAh / g) was converted from this. For Example Test Cell 2 and Example Test Cell 3, the discharge capacity retention rate (%) was determined using the calculation formula (Equation 1) in the same manner as Example Test Cell 1. The results are summarized in Table 2.

(Comparative Example 1)
80 parts by weight of LiNi _0.33 Co _0.33 Mn _0.33 O ₂ powder having an average particle diameter of 5 μm as a raw material for the positive electrode active material, 10 parts by weight of acetylene black (Denka Black, manufactured by Denki Kagaku Kogyo Co., Ltd.) as a conductive agent, and N-methylpyrrolidone (NMP) (manufactured by Mitsubishi Chemical Corporation), which is an organic solvent, is added to 10 parts by weight of polyvinylidene fluoride (PVDF) (manufactured by Kureha, KF # 1100) as a resin binder, and dispersed. A slurry-like coating composition for forming a positive electrode active material layer was prepared by stirring with an Excel auto homogenizer (Nippon Seiki Seisakusho Co., Ltd.) at a rotational speed of 5000 rpm for 15 minutes so that the solid content concentration became 55% by weight. And the application amount of the coating composition for positive electrode active material layer formation after drying on the aluminum plate of thickness 15 micrometers used for the positive electrode active material layer formation coating composition prepared above as a positive electrode collector. It apply | coated so that it might become 68 g / m < ² >, It was made to dry in 120 degreeC atmospheric condition using an oven for 20 minutes, and the electrode active material layer for positive electrodes was formed on the collector surface. Furthermore, after pressing using a roll press machine so that the applied density of the formed electrode active material layer is 2.0 g / cm ³ (thickness of the positive electrode active material layer: 24 μm), a predetermined size ( And was vacuum-dried at 120 ° C. for 12 hours to produce an electrode plate for a non-aqueous electrolyte secondary battery positive electrode, which was referred to as Comparative Example 1. For Comparative Example 1, film forming properties were evaluated in the same manner as in Example 1. The results are shown in Table 1.

<Production of tripolar coin cell>
A tripolar coin cell was assembled in the same manner as Example Test Cell 1 except that Comparative Example 1 produced as described above was used as the working electrode, and this was designated as Comparative Example Test Cell 1.

<Charge test and discharge test>
About the comparative example test cell 1, except having changed the constant current in each discharge rate into the value shown in Table 2, a charge test and a discharge test are implemented like the example test cell 1, and the working electrode in each discharge rate is carried out. The discharge capacity (mAh) was determined, and the discharge capacity (mAh / g) per unit weight was converted from this. Similarly to the example test cell 1, the discharge capacity retention rate (%) was obtained using the calculation formula (Equation 1). The results are summarized in Table 2.

(Comparative Example 2)
A positive electrode plate was prepared in the same manner as in Comparative Example 1 except that the compounding amount of PVDF, which is a resin binder, was changed to 7% by weight with respect to the total solid components, and Comparative Example 2 was obtained. In Comparative Example 2, the film forming property was evaluated in the same manner as in Example 1. The results are as shown in Table 1.

<Production of tripolar coin cell>
A tripolar coin cell was assembled in the same manner as Example Test Cell 1 except that Comparative Example 2 produced as described above was used as the working electrode, and this was designated as Comparative Example Test Cell 2.

<Charge test and discharge test>
About the comparative example test cell 2, except having changed the constant current in each discharge rate into the value shown in Table 2, a charge test and a discharge test are implemented like the example test cell 1, and the working electrode in each discharge rate is carried out. The discharge capacity (mAh) was determined, and the discharge capacity (mAh / g) per unit weight was converted from this. Similarly to the example test cell 1, the discharge capacity retention rate (%) was obtained using the calculation formula (Equation 1). The results are summarized in Table 2.

(Comparative Example 3)
A positive electrode plate was prepared in the same manner as in Comparative Example 2 except that no resin binder was used, and this was used as Comparative Example 3. However, in Comparative Example 3, a part of the electrode active material layer was peeled off when drawn out into a disk having a predetermined size, and the film forming property was poor (Table 1). As a result, the charge / discharge test could not be carried out.

  Comparing Example 1 and Comparative Example 1, Example 1 is different in that the discharge capacity retention rate is also significantly higher. This difference is larger than the difference due to the difference in the amount of resin binder added as in Comparative Examples 1 and 2. Further, as shown in Comparative Example 3, when the same method as in Comparative Example 1 is used without simply adding the addition amount of the resin binder, the electrode active material layer itself can no longer be formed. End up. That is, an electrode active material layer having excellent input / output characteristics similar to that of Example 1 cannot be formed by simply reducing the resin binder or adding no resin binder using a conventional manufacturing method. . In this regard, in Example 1, an electrode active material layer having excellent input / output characteristics (that is, excellent discharge capacity retention ratio) can be formed without requiring a resin binder.

  In any of Examples 1 to 3, the particle diameter of the electrode active material layer can be reduced, and in Examples 1 and 2, the value of the average minimum particle diameter is very small, ie, a value of 10 μm or less. Value could be realized.

Claims (10)

A positive electrode plate for a non-aqueous electrolyte secondary battery comprising a current collector and an electrode active material layer composed of an active material on at least a part of the surface of the current collector,
The electrode active material layer is composed of an active material containing at least lithium and two or more metal elements selected from the group consisting of cobalt, nickel, and manganese, and the active materials are partially joined to each other. And a layer having a structure in which the active material is continuously present, and a porous layer having voids through which the electrolytic solution can penetrate,
A positive electrode plate for a non-aqueous electrolyte secondary battery, wherein at least part of the active material contained in the electrode active material layer is bonded to a current collector.
2. The positive electrode plate for a non-aqueous electrolyte secondary battery according to claim 1, wherein the electrode active material layer is composed of an active material containing lithium, cobalt, nickel, and manganese as the metal element. .
2. The positive electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein the active material constituting the electrode active material layer is a lithium transition metal composite oxide or a lithium transition metal composite phosphate compound. Board.
The particle diameters of 20 arbitrarily selected active material particles are measured based on observation of an electrode active material layer by an electron microscope, and the arithmetic average value of 5 points selected in order of decreasing particle diameter is the average of the active material. When the average maximum particle size of the active material is set to the minimum particle size, and the arithmetic average value for 5 points selected in order of increasing particle size,
The average minimum particle size of the active material is 3 nm or more and less than 20 nm, and the average maximum particle size is 20 nm or more and less than 200 nm, according to any one of claims 1 to 3, Positive electrode plate for non-aqueous electrolyte secondary battery.
5. The positive electrode plate for a non-aqueous electrolyte secondary battery according to claim 1, wherein the electrode active material layer has a thickness of 300 nm to 10 μm.
6. The discharge capacity maintenance ratio is 50% or more at a discharge rate of 50C or more, assuming that the discharge capacity maintenance ratio when discharging at a discharge rate of 1C is 100%. A positive electrode plate for a non-aqueous electrolyte secondary battery according to claim 1.
An electrode active material layer forming solution containing lithium and containing two or more metal elements selected from the group consisting of nickel, cobalt, and manganese,
Applying the electrode active material layer forming solution on at least a part of the current collector surface to form a coating film,
Next, the current collector on which the coating film is formed is subjected to a heat treatment including a process of heating at a temperature of 150 ° C. or higher with a heat source placed on the coating film side, A method for producing a positive electrode plate for a non-aqueous electrolyte secondary battery, wherein an electrode active material layer is formed by generating a lithium transition metal composite oxide exhibiting a lithium ion insertion / release reaction.
Preparing an electrode active material layer forming solution containing lithium and two or more metal elements selected from the group consisting of nickel, cobalt, and manganese and a phosphorus element;
Applying the electrode active material layer forming solution on at least a part of the current collector surface to form a coating film,
Next, a heating process comprising a heating process at a temperature of 200 ° C. or higher in an inert gas or reducing gas atmosphere in a state where a heat source is installed on the coating film side with respect to the current collector on which the coating film is formed. And forming an electrode active material layer by forming a lithium transition metal composite phosphate compound exhibiting a lithium ion insertion / release reaction on the surface of the current collector. For producing a positive electrode plate for use.
After the heat treatment is performed by heating the current collector on which the coating film is formed on the coating film side, the heat source is further installed on both sides of the current collector, The method of manufacturing a positive electrode plate for a non-aqueous electrolyte secondary battery according to claim 7 or 8, wherein the current collector is heated.
A non-aqueous electrolyte secondary battery comprising at least a positive electrode plate, a negative electrode plate, a separator provided between the positive electrode plate and the negative electrode plate, and an electrolyte containing a non-aqueous solvent,
The said positive electrode plate is a positive electrode plate for nonaqueous electrolyte secondary batteries of any one of Claim 1 to 6, The nonaqueous electrolyte secondary battery characterized by the above-mentioned.

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