JP5374960B2 - Electrode plate for non-aqueous electrolyte secondary battery, method for producing the same, and non-aqueous electrolyte secondary battery - Google Patents

Description

  The present invention relates to an electrode plate used for a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery, a method for producing the same, 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 also has a memory effect during charging / discharging (when the battery is charged before it is fully charged, the battery is gradually charged. Since there is no phenomenon in which the capacity decreases, it is used in various fields such as portable devices and large devices.

  A general non-aqueous electrolyte secondary battery is composed of a positive electrode, a negative electrode, a separator, and an organic electrolyte, and the positive electrode and the negative electrode are coated with a coating composition on a current collector such as a metal foil. Thus, a material in which an electrode active material layer is formed is generally used.

  Usually, the electrode active material layer is a slurry-like electrode active material obtained by kneading and / or dispersing a dischargeable electrode active material, a binder, and, if necessary, a conductive agent and other materials in an organic solvent. It is formed by preparing a coating composition for a layer, applying the coating composition on a current collector, and then drying.

  In recent years, development of large-capacity secondary batteries has been promoted especially for fields that require high output characteristics such as electric vehicles, hybrid vehicles, and power tools. However, a battery with high impedance has a problem that it cannot fully utilize its capacity during high-power charge / discharge.

For this reason, a method is used in which the electrode active material layer has a large thin film area to reduce the impedance of the battery.
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, in the method of drying after applying the slurry-like electrode active material layer coating composition on the current collector, the active material is fixed to the current collector to form a film from the coating composition. Since a binder is required, it is difficult to reduce the thickness of the electrode active material layer, and the thickness of the layer is limited to about several tens of μm. Further, the binder hinders the permeability of the electrolytic solution into the active material and the electrode conductivity.

  Known methods for forming a thin-film electrode active material layer on a current collector include a vacuum deposition method and a sol-gel method. However, the vacuum deposition method requires a large-scale device such as a vacuum device, and the sol-gel method requires a polymerization reaction using a catalyst in order to gel the sol of the electrode active material layer on the current collector. Therefore, it takes a long time to form a film.

  Furthermore, as a method for forming a thin-film electrode active material layer on a current collector, a method in which an electrode active material layer forming liquid is atomized and sprayed on the current collector is also known.

  In the first method described in Patent Document 1, a solution based on lithium is formed into mist droplets by an ultrasonic generator (see FIG. 5 in Patent Document 1). Then, the mist droplets are vaporized through a heated injection tube while being pressurized, and sprayed onto the substrate as an atomized solution from a nozzle. Since the atomized solution is heated, a chemical reaction starts with oxygen in the air before coming into contact with the substrate, and lithium cobalt oxide as an electrode active material is synthesized. Then, those lithium cobalt oxides are deposited on the substrate to form an electrode active material layer.

  In the second method described in Patent Document 1, a precursor solution (lithium-based solution) is atomized by an ultrasonic generator to form a precursor mist droplet (see FIG. 14 in the Patent Document 1). .) The precursor mist droplets are deposited on the substrate by a heated gas stream. Note that, even by the heat source of the heated gas flow, the chemical reaction of the precursor mist droplets proceeds until the base reaches the substrate, so that lithium cobalt oxide is synthesized. Then, those lithium cobalt oxides are deposited on the substrate to form an electrode active material layer.

  The electrode active material layer formed by these methods is excellent in conductivity and the like because it can be thinned and has crystallinity. Further, since the electrode active material layer is formed by crystallization, there is an advantage that there is no need for a crystallization step (annealing step) of the electrode active material layer by heat treatment.

  However, the first and second methods described in Patent Document 1 are simpler than the vacuum apparatus used in the vacuum deposition method, but the atomized solution or the precursor mist droplets are directly applied (FIG. 5). Or an apparatus for heating indirectly (FIG. 14) is required.

  In recent years, it has become necessary to further crystallize the formed electrode active material layer for the purpose of improving the electrical characteristics of the electrode. In this case, it is necessary to heat the electrode again (annealing process). However, the electrode active material layer formed by atomizing the lithium-based solution has a phenomenon that cracks are generated by heating during the annealing process. It is known (for example, see paragraph number 0022 in Patent Document 1).

  Furthermore, by increasing the surface area of the electrode plate, the impedance of the battery is lowered or the charge amount is increased. In this case, it is generally known to use a porous material for the current collector. The porous material has irregularities on its surface or has pores. Therefore, the surface area becomes extremely large as compared with a normal material having the same outer shape.

  However, the slurry-like electrode active material layer forming liquid and the sol used in the sol-gel method are not uniformly applied along the irregularities of the porous material due to its high viscosity, or the forming liquid or sol is not formed in the pores. There is a problem that it is difficult to penetrate.

Special Table 2003-515888

  The present invention has been accomplished in view of the above circumstances, and a first object is to form an electrode plate for a non-aqueous electrolyte secondary battery that is formed in a short time and is composed of a thin electrode active material layer. Another object of the present invention is to provide a non-aqueous electrolyte secondary battery configured using the electrode plate as a positive electrode plate.

  The second object of the present invention is to provide a non-aqueous electrolyte secondary battery in which abnormalities such as cracks do not occur in the electrode active material layer provided on the electrode plate even when the manufactured electrode plate is reheated. It is in providing the non-aqueous-electrolyte secondary battery comprised using the electrode plate and its manufacturing method, and the said electrode plate as a positive electrode plate.

  A third object of the present invention is to provide a non-aqueous electrolyte secondary battery in which an electrode active material layer is provided on the entire surface with a substantially uniform thickness even when a porous material is used for the current collector. It is providing the non-aqueous-electrolyte secondary battery comprised using the electrode plate, its manufacturing method, and the said electrode plate as a positive electrode plate.

The method for producing a non-aqueous electrolyte secondary battery according to the present invention includes a non-aqueous electrolyte secondary battery using an electrode plate for a non-aqueous electrolyte secondary battery in which a positive electrode active material layer is provided on a current collector as a positive electrode plate. A method for manufacturing a secondary battery, comprising:
As a positive electrode active material, a positive electrode active material layer forming liquid containing a raw material for producing a lithium composite oxide containing at least one of cobalt, nickel, manganese, iron or titanium is used as a solvent for the positive electrode active material layer forming liquid. And spraying on at least one surface side of the current collector heated to 500 to 600 ° C., and applying the positive electrode active material forming liquid to the one surface side Attach
Chemically reacting the raw material in the positive electrode active material layer forming liquid attached to the one surface side by the heat of the current collector to produce a positive electrode active material on the current collector;
The positive electrode active material layer formed on the current collector is heated again to 400 to 600 ° C. for crystallization to form the positive electrode active material layer.

  In the present invention, since the electrode active material layer is formed by spraying the electrode active material layer forming liquid onto a current collector heated to a predetermined temperature, the slurry-like electrode active material layer coating composition is used. Thus, the electrode active material layer can be formed in a shorter time than the method using, and since the binder is not used, the electrode active material layer can be formed thinner. Further, in the present invention, since the raw material for forming the electrode active material layer by the heat on the current collector chemically reacts, the electrode active material layer has excellent adhesion to the current collector. . Further, the porosity and crystallinity of the electrode active material layer can be controlled by adjusting experimental conditions such as the temperature of the current collector.

  In the present invention, the electrode active material is synthesized from the raw material on the current collector, and the electrode active material is deposited on the current collector so as to reduce strain. It also has the feature that the stress of is small. For this reason, even if the electrode plate for a non-aqueous electrolyte secondary battery once manufactured is reheated (annealing process), the crystallization of the electrode active material layer only proceeds, and there is an abnormality such as a crack in the layer. Occurrence can be prevented.

  In the present invention, even when a porous material is used for the current collector in order to spray the electrode active material forming liquid on the current collector, surface irregularities and pores of the porous material The electrode active material forming liquid uniformly adheres to the entire surface of the part. The forming liquid causes a chemical reaction, and the electrode active material is synthesized and deposited, whereby the electrode active material layer having a uniform thickness along the surface irregularities and the surface of the pores of the porous material. Is formed.

A method for producing an electrode plate for a non-aqueous electrolyte secondary battery according to the present invention is a method for producing an electrode plate for a non-aqueous electrolyte secondary battery in which an electrode active material layer is provided on a current collector,
An electrode active material layer forming liquid containing a raw material for generating an electrode active material is heated to a predetermined temperature at a temperature not higher than the boiling point of the solvent of the electrode active material layer forming liquid. Spray on the surface side, adhere the electrode active material forming liquid to the one surface side,
The electrode active material is produced on the current collector by chemically reacting the raw material in the electrode active material layer forming liquid adhered to the one surface side by the heat of the current collector. A material layer is formed.

(Electrode plate)
The method for producing an electrode plate for a non-aqueous electrolyte secondary battery according to the present invention can be employed in any method for producing a positive electrode plate and a negative electrode plate, but is more preferably employed as a method for producing a positive electrode plate. be able to.
Below, the manufacturing method of a positive electrode plate is mentioned as a representative example, and the manufacturing method of the electrode plate for nonaqueous electrolyte secondary batteries which concerns on this invention is demonstrated.

  The method for producing a positive electrode plate for a non-aqueous electrolyte secondary battery according to the present invention includes (1) a step of preparing a positive electrode active material layer forming liquid, (2) a step of spraying and attaching a positive electrode active material layer forming liquid, and (3 ) Including a step of forming a positive electrode active material layer, and through the steps (1) to (3), a desired positive electrode plate for a non-aqueous electrolyte secondary battery is obtained, and for the non-aqueous electrolyte secondary battery A desired nonaqueous electrolyte secondary battery can be obtained using the positive electrode plate as a constituent material.

  The positive electrode plate for a non-aqueous electrolyte secondary battery according to the present invention can be manufactured using, for example, the electrode plate manufacturing apparatus 1 shown in FIG. 1, and the manufacturing method using the electrode plate manufacturing apparatus 1 is also described below. An example will be described.

(1) Preparation Step of Positive Electrode Active Material Layer Forming Solution In this step, the raw material (solute) for producing the positive electrode active material is added to a solvent so as to have a predetermined concentration and dissolved to form a positive electrode active material layer forming solution. To prepare.

  In addition, when using the electrode plate manufacturing apparatus 1 shown in FIG. 1, the prepared positive electrode active material layer formation liquid is accommodated in the storage container 2 of an electrode active material formation liquid.

  The raw material for producing the positive electrode active material is not particularly limited as long as it is generally used as a raw material for producing the positive electrode active material of the positive electrode plate for a nonaqueous electrolyte secondary battery, but cobalt, nickel, manganese, iron or A raw material for producing a lithium composite oxide containing at least one of titanium is preferably used.

  Here, the “raw material for producing the positive electrode active material” means a positive electrode active material layer forming solution sprayed and adhered on the positive electrode current collector in the step of forming a positive electrode active material layer described later (3) It means a single compound or a combination of two or more compounds that can be chemically reacted with heat applied to the positive electrode current collector to produce a positive electrode active material on the positive electrode current collector.

The raw material for generating the lithium composite oxide, for example, to produce a raw material for generating the LiCoO ₂ (lithium cobaltate), a raw material for generating the LiNiO ₂ (lithium nickel oxide), and LiMn ₂ O ₄ (lithium manganate) material, the raw material for generating a LiFeO ₂ (ferrate lithium), and LiTiO ₂ raw material or the like for generating the (lithium titanate) and the like typically.

As a raw material for producing LiCoO ₂ , a compound made of Li and a compound made of Co can be used in combination as main raw materials, and further, other raw materials can be used in combination as required.
Examples of the compound composed of Li include lithium citrate tetrahydrate, lithium perchlorate trihydrate, lithium acetate dihydrate, lithium nitrate, and lithium phosphate, and also composed of Co. Examples of the compound include cobalt (II) chloride hexahydrate, cobalt (II) formate dihydrate, cobalt (III) acetylacetonate, cobalt (II) acetylacetonate dihydrate, cobalt acetate (II ) Tetrahydrate, cobalt (II) oxalate dihydrate, cobalt (II) nitrate hexahydrate, cobalt (II) ammonium chloride hexahydrate, sodium cobalt (III) nitrite, and cobalt sulfate ( II) The heptahydrate etc. are mentioned.
The combination ratio (Li: Co = X: 1) of the compound composed of Li and the compound composed of Co used as the main raw material is not particularly limited, but is preferably 1 ≦ X <2, and preferably 1 ≦ X ≦ 1. 2 is more preferable.
When the combination ratio is less than the above range, a positive electrode plate having desired performance may not be produced efficiently.

As a raw material for producing LiNiO ₂ , a compound made of Li and a compound made of Ni can be used in combination as main raw materials, and further, other raw materials can be used in combination as required.
Examples of the compound composed of Li include lithium citrate tetrahydrate, lithium perchlorate trihydrate, lithium acetate dihydrate, lithium nitrate, and lithium phosphate, and also composed of Ni. Examples of the compound include nickel chloride (II) hexahydrate, nickel acetate (II) tetrahydrate, nickel perchlorate (II) hexahydrate, nickel bromide (II) trihydrate, nitric acid Examples include nickel (II) hexahydrate, nickel (II) acetylacetonate dihydrate, nickel (II) hypophosphite hexahydrate, and nickel (II) sulfate hexahydrate.
The combination ratio of the compound composed of Li and the compound composed of Ni used as the main raw material (Li: Ni = X: 1) is not particularly limited, but is preferably 1 ≦ X <2, and preferably 1 ≦ X ≦ 1. 2 is more preferable.
When the combination ratio is less than the above range, a positive electrode plate having desired performance may not be produced efficiently.

As raw materials for producing LiMn ₂ O ₄ , a compound made of Li and a compound made of Mn can be used in combination as main raw materials, and other raw materials can be used in combination as required.
Examples of the compound composed of Li include lithium citrate tetrahydrate, lithium perchlorate trihydrate, lithium acetate dihydrate, lithium nitrate, and lithium phosphate, and also composed of Mn. Examples of the compound include manganese acetate (III) dihydrate, manganese (II) nitrate hexahydrate, manganese (II) sulfate pentahydrate, manganese (II) oxalate dihydrate, and manganese ( III) Acetylacetonate and the like.
The combination ratio (Li: Mn = X: 1) of the compound composed of Li and the compound composed of Mn used as the main raw material is not particularly limited, but is preferably 0.5 ≦ X <1, 0.5 ≦ More preferably, X ≦ 0.6.
When the combination ratio is less than the above range, a positive electrode plate having desired performance may not be produced efficiently.

As raw materials for producing LiFeO ₂ , a compound composed of Li and a compound composed of Fe can be used in combination as main raw materials, and other raw materials can be used in combination as required.
Examples of the compound composed of Li include lithium citrate tetrahydrate, lithium perchlorate trihydrate, lithium acetate dihydrate, lithium nitrate, and lithium phosphate, and also composed of Fe. Examples of the compound include iron (II) chloride tetrahydrate, iron (III) citrate, iron (II) acetate, iron (II) oxalate dihydrate, iron (III) nitrate nonahydrate, Examples thereof include iron (II) lactate trihydrate and iron (II) sulfate heptahydrate.
The combination ratio (Li: Fe = X: 1) of the compound composed of Li and the compound composed of Fe used as the main raw material is not particularly limited, but is preferably 1 ≦ X <2, and preferably 1 ≦ X ≦ 1. 2 is more preferable.
When the combination ratio is less than the above range, a positive electrode plate having desired performance may not be produced efficiently.

As raw materials for producing LiTiO ₂ , a compound made of Li and a compound made of Ti can be used in combination as main raw materials, and other raw materials can be used in combination as required.
Examples of the compound composed of Li include lithium citrate tetrahydrate, lithium perchlorate trihydrate, lithium acetate dihydrate, lithium nitrate, and lithium phosphate, and also composed of Ti. Examples of the compound include titanium tetrachloride and titanium acetylacetonate.
The combination ratio of the compound composed of Li and the compound composed of Ti used as the main raw material (Li: Ti = X: 1) is not particularly limited, but is preferably 1 ≦ X <2, and preferably 1 ≦ X ≦ 1. 2 is more preferable.
When the combination ratio is less than the above range, a positive electrode plate having desired performance may not be produced efficiently.

  The solvent used for preparing the positive electrode active material layer forming liquid is not particularly limited as long as it can dissolve or disperse the raw material for generating the positive electrode active material. For example, an aqueous solvent; methanol, ethanol, isopropyl alcohol Lower alcohol solvents having a total carbon number of 5 or less such as toluene, propanol and butanol; aromatic hydrocarbon solvents such as toluene, ethylbenzene and xylene; diketone solvents such as acetylacetone, diacetyl and benzoylacetone; ethyl acetoacetate And ketoester solvents such as ethyl pyruvate, ethyl benzoyl acetate, and ethyl benzoyl formate; and mixed solvents thereof.

  The boiling point temperature of the solvent used for preparing the positive electrode active material layer forming liquid is preferably 40 to 200 ° C, more preferably 50 to 180 ° C, and further preferably 60 to 150 ° C.

  When the temperature of the boiling point of the solvent is less than the above range, the temperature of the boiling point of the solvent is too low. Therefore, in the next step (2) the step of spraying and attaching the positive electrode active material layer forming liquid, It becomes easy to be affected by the radiant heat from the body, and the solvent may boil off from the sprayed droplets. On the other hand, when the temperature of the boiling point of the solvent exceeds the above range, the temperature of the boiling point of the solvent is too high. Therefore, in the next step (3) forming the positive electrode active material layer, the raw material for forming the positive electrode active material layer The chemical reaction is difficult to be performed smoothly, and the film cannot be grown properly, and the adhesion to the current collector may be poor.

  The concentration of the solute (the raw material for producing the positive electrode active material) in the positive electrode active material layer forming liquid is preferably 0.001 to 5 mol / L, more preferably 0.01 to 2 mol / L, and 0 More preferably, it is 1-1 mol / L.

  When the concentration of the solute in the positive electrode active material layer forming liquid is less than the above range, the concentration of the solute in the positive electrode active material layer forming liquid is too low, so the next step (3) Formation of the positive electrode active material layer In the process, it takes time to form the positive electrode active material layer, and the productivity may be inferior. On the other hand, when the concentration of the solute in the positive electrode active material layer forming liquid exceeds the above range, the concentration of the solute in the positive electrode active material layer forming liquid is too high. (2) In the spraying / adhering step of the positive electrode active material layer forming liquid, the nozzle is likely to be clogged, and the spraying may not be performed with high accuracy.

  In this step, the positive electrode active material layer forming liquid is prepared mainly using the raw material for generating the positive electrode active material described above and the solvent described above as a constituent component, and does not require a binder, but adversely affects conductivity and the like. If necessary, a binder generally used in the preparation process of a conventional slurry-like coating composition for electrode active material layer, and if necessary, a conductive agent and a thickener are used. May be.

(2) Spray / adhesion step of positive electrode active material layer forming liquid In this step, the prepared positive electrode active material layer forming liquid obtained through the step (1) is used as a solvent for the positive electrode active material layer forming liquid. The positive electrode active material layer forming liquid is sprayed and uniformly deposited on at least one surface side of the positive electrode current collector which is atomized at a temperature equal to or lower than the boiling point and heated to a predetermined temperature.

In this step, the method for spraying the prepared positive electrode active material layer forming liquid is not particularly limited. For example, when the electrode plate manufacturing apparatus 1 shown in FIG. 1 is used, the electrode active material layer is used. The forming liquid (positive electrode active material layer forming liquid) 3 is atomized by the ultrasonic generator 4.
In addition to the ultrasonic generator 4, means such as a spray can be used for the atomization process.

  The atomized electrode active material layer forming liquid (positive electrode active material layer forming liquid) is discharged from the nozzle 7 through the pipe 6 by the pressurizing device 5 and heated to a predetermined temperature by the hot plate 10 to be heated. Spraying can be performed by spraying on the body 11 as a mist droplet 8.

  The discharge amount of the electrode active material layer forming liquid (positive electrode active material layer forming liquid) discharged from the nozzle 7 is preferably 1 to 50 ml / min, and preferably 1 to 30 ml / min from the viewpoint of suitable spraying. More preferably, it is 1-20 ml / min.

The discharge pressure of the electrode active material layer forming liquid (positive electrode active material layer forming liquid) discharged from the nozzle 7 is preferably 1 to 1 × 10 ⁷ Pa, preferably 10 to 7 × 10, from the viewpoint of suitable spraying. ⁶ Pa is more preferable, and 100 to 5 × 10 ⁶ Pa is even more preferable.

  The distance from the tip of the nozzle 7 to the surface of the current collector 11 is preferably 5 to 50 cm, more preferably 10 to 25 cm, and further preferably 15 to 20 cm, from the viewpoint of suitable spraying. preferable.

  The angle between the tip of the nozzle 7 and the surface of the current collector 11 is preferably 90 degrees from the viewpoint of uniform spraying, but is not particularly limited, and spraying may be performed by appropriately changing the angle. it can.

The amount of the electrode active material layer forming liquid (positive electrode active material layer forming liquid) attached per surface area of the positive electrode current collector is preferably 0.001 to 1 ml / cm ² , and preferably 0.01 to 0. more preferably 5 ml / cm ^2, further preferably 0.05~0.1ml / cm ^2.

  When the adhesion amount of the positive electrode active material layer forming liquid is less than the above range, the adhesion amount of the positive electrode active material layer forming liquid to the positive electrode current collector is too small. In the forming step, the reaction efficiency of the raw material for forming the positive electrode active material layer is reduced, and it takes time to form the positive electrode active material layer, which may be inferior in productivity. On the other hand, when the amount of the positive electrode active material layer forming liquid adhering to the positive electrode current collector exceeds the above range, the amount of the positive electrode active material layer forming liquid adhering to the positive electrode current collector is too large. ) In the step of forming the positive electrode active material layer, the chemical reaction of the raw material for forming the positive electrode active material layer is difficult to be performed smoothly, the film cannot be grown properly, and the adhesion to the current collector is poor. There is.

  In this step, when the positive electrode active material layer forming solution is atomized, it is not necessary to apply special heating to the positive electrode active material layer forming solution, but to the extent that the boiling point of the solvent of the positive electrode active material layer forming solution is not exceeded. There is no particular limitation as long as it is applied.

  The positive electrode current collector is not particularly limited as long as it is generally used as a positive electrode current collector of a positive electrode plate for a non-aqueous electrolyte secondary battery, but is formed from a single substance or an alloy such as aluminum, nickel, or copper. Those having high conductivity such as carbon sheets, carbon plates, and carbon textiles are preferably used.

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

  The temperature of the positive electrode current collector that is heated to a predetermined temperature is preferably 200 to 800 ° C, more preferably 300 to 600 ° C, and further preferably 350 to 500 ° C.

  Here, the “predetermined temperature” is an atmosphere immediately above the positive electrode current collector (corresponding to “atmosphere 9 immediately above the current collector” shown in FIG. 1) due to heat applied to the positive electrode current collector. Even when heated, the solvent of the positive electrode active material layer forming liquid to be sprayed disappears by boiling due to the influence of the temperature of the atmosphere (under the influence of radiant heat from the heated current collector), and the solute It means that the temperature is set so as not to spray only.

  When the temperature of the positive electrode current collector is less than the above range, the temperature of the positive electrode current collector is too low. Therefore, in the next step (3) the step of forming the positive electrode active material layer, the positive electrode active material layer is formed. The reaction efficiency of the raw material is lowered, and it takes time to form the positive electrode active material layer, which may be inferior in productivity. On the other hand, when the temperature of the positive electrode current collector exceeds the above range, the temperature of the positive electrode current collector is too high, and the solvent may boil off from the sprayed droplets and disappear.

  The temperature of the atmosphere immediately above the positive electrode current collector to be used after being heated to a predetermined temperature (region temperature in a range within 20 cm in height from the positive electrode current collector) is the temperature of the boiling point of the solvent of the positive electrode active material layer forming liquid. It is preferable to be in a temperature range within plus 50 ° C.

(3) Formation process of positive electrode active material layer In this process, the positive electrode active material layer forming liquid sprayed and adhered to at least one surface side of the positive electrode current collector obtained through the above step (2) is used as the positive electrode. As the positive electrode active material is synthesized by volatilizing the solvent of the positive electrode active material layer forming liquid by chemically reacting with the heat of the current collector and synthesizing the positive electrode active material, the positive electrode current collector is deposited upward from the surface of the positive electrode current collector. A granular film is grown (crystallized) to form a desired positive electrode active material layer.

  In this step, the method for forming the positive electrode active material layer is not particularly limited. For example, when the electrode plate manufacturing apparatus 1 shown in FIG. 1 is used, the positive electrode active material layer is heated by heat conduction from the hot plate 10. The electrode active material layer 13 can be formed by a chemical reaction caused by the heat of the current collector 11.

  The temperature of the hot plate is the most important factor for generating the electrode active material by chemically reacting the positive electrode active material layer forming liquid containing the raw material for generating the electrode active material. By sufficiently performing the above, it is possible to control the thickness, crystallinity, and the like of the electrode active material layer.

  In the present invention, the temperature of the current collector 11 heated from the hot plate is high when the current collector such as aluminum or nickel having high conductivity and high thermal conductivity is used. It is almost the same as the set temperature of the plate.

  In addition, although the environmental temperature in which the electrode plate manufacturing apparatus 1 is installed is not particularly limited, it is usually preferable to be at room temperature (about 25 ° C.).

  In this step, from the viewpoint of further increasing the crystallinity of the positive electrode active material layer to be formed, it is preferable to perform a step of heating the positive electrode current collector again (annealing step). The conditions for the annealing step are not particularly limited, but it is necessary to set the conditions such that cracks and other abnormalities do not occur in the positive electrode active material layer.

  The heating temperature in the annealing step is preferably 300 to 800 ° C, more preferably 350 to 650 ° C, and further preferably 400 to 600 ° C.

  When the heating temperature in the annealing step is less than the above range, the effect of increasing the crystallinity may not be sufficiently exhibited. On the other hand, when the heating temperature in the annealing step exceeds the above range, the positive electrode active material may be easily deteriorated.

  The heating time in the annealing step is preferably 10 to 10000 minutes, more preferably 30 to 6000 minutes, and further preferably 60 to 600 minutes.

  When the heating time in the annealing step is less than the above range, the effect of increasing the crystallinity may not be sufficiently exhibited. On the other hand, when the heating time in the annealing step exceeds the above range, the positive electrode active material may be easily deteriorated.

  The thickness of the positive electrode active material layer to be formed is preferably 0.01 to 50 μm, more preferably 0.1 to 10 μm, and further preferably 0.2 to 5 μm.

  When the thickness of the positive electrode active material layer is less than the above range, a sufficient volume energy density may not be obtained. On the other hand, when the thickness of the positive electrode active material layer exceeds the above range, abnormalities such as cracks are likely to occur in the positive electrode active material layer, and the adhesion to the current collector may be poor.

According to the method for manufacturing an electrode plate according to the present invention, the desired adhesion and homogeneity to the current collector can be obtained without the need for the press processing performed by the conventional electrode plate manufacturing method. May be applied.
As press work, it can carry out using a metal roll, an elastic roll, a heating roll, a roll press, a sheet press etc., for example.

The electrode plate manufacturing method according to the present invention does not require preheating (about 200 ° C.) as performed in the manufacturing method of Patent Document 1, the manufacturing equipment is simple, and the thickness is short. A thin desired electrode active material layer can be formed.
In addition, even when the electrode plate manufactured according to the present invention is reheated (even if an annealing process is performed), the electrode active material layer does not show any abnormalities such as cracks, and the desired electrode active material layer having a high degree of crystallinity Can be formed.
Furthermore, even when a porous material is used as a current collector, an electrode active material layer can be formed with a substantially uniform thickness on the entire surface of the current collector, and an electrode plate having excellent charge / discharge characteristics can be obtained. it can.

(Non-aqueous electrolyte secondary battery)
In the nonaqueous electrolyte secondary battery, the positive electrode plate and the negative electrode plate according to the present invention are wound through a separator such as a polyethylene porous film and stored in a battery container. And it assembles by filling a non-aqueous electrolyte in a battery container.

  The non-aqueous electrolyte 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 non-aqueous electrolyte in which a lithium salt is dissolved in an organic solvent 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 (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 an organic lithium such as LiOSO ₂ C ₇ F ₁₅ Salt; and the like.

  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.

  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, malon Examples include acid dialkyl esters and acetic acid alkyl esters.

  Examples of 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. .

Example 1
<Preparation of electrode plate for positive electrode>
LiNO ₃ [molecular weight: 68.95]; 20.7 g (0.3 mol) and Co (NO ₃ ) ₂ .6H ₂ O [molecular weight: 291.03]; 87. 3 g (0.3 mol) was used and added to 300 mL of ethanol / acetylacetone mixed solvent (volume ratio = 1: 1) and dissolved to prepare a positive electrode active material layer forming liquid having a solute concentration of 2 mol / L.

  On the hot plate heated to 500 ° C., an aluminum foil having a thickness of 15 μm, which is a positive electrode current collector, is placed, and the positive electrode active material layer forming liquid prepared above is placed on one side of the positive electrode current collector. Using the electrode plate manufacturing apparatus 1 shown in FIG. 1, spraying was performed through an ultrasonic nebulizer to form a positive electrode active material layer.

  The positive electrode active material layer formed on the positive electrode current collector is baked in an air atmosphere at 600 ° C. for 1 hour using an electric furnace (annealing step) to crystallize the positive electrode active material layer, It cut | judged to a magnitude | size (length 2cm x width 2cm), and produced the electrode plate for positive electrodes of Example 1. FIG.

In addition, when the positive electrode plate produced above was observed using a scanning electron microscope (SEM) and an X-ray diffractometer (XRD), the positive electrode active material layer had a thickness of 0. 0 on the positive electrode current collector. It was confirmed that a 5 μm LiCoO ₂ layer was formed.

<Production of tripolar beaker cell>
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.

  The positive electrode plate prepared above as a working electrode (length 2 cm × width 2 cm, weight of the positive electrode active material contained: 0.4 mg), metal lithium having a metal lithium foil pressed onto a nickel mesh as a counter electrode and a reference electrode Using the non-aqueous electrolyte prepared above as the plate and electrolyte, lead wires (nickel wires) were previously attached to each electrode plate (electrode plate for positive electrode, counter electrode, reference electrode) using a spot welder. Then, the tripolar beaker cell was assembled, the tripolar beaker cell of Example 1 was produced, and it used for the following charging / discharging test.

(Comparative Example 1)
80 parts by weight of LiCoO ₂ powder having an average particle size of 10 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 PVDF (manufactured by Kureha, KF # 1100) To 10 parts by weight, NMP (manufactured by Mitsubishi Chemical Corporation) as an organic solvent is added and dispersed, and dispersed and / or kneaded so that the solid content concentration becomes 55% by weight. A layer coating composition was prepared.

The coating amount of the positive electrode active material layer coating composition prepared above was dried on a positive electrode current collector 15 μm-thick aluminum foil with a coating amount of the positive electrode active material layer coating composition of 50 g / It was applied so that the m ^2, using an oven, subjected to drying under an air atmosphere at 120 ° C., to form a positive electrode active material layer.

Furthermore, after pressing using a roll press machine so that the coating density of the formed positive electrode active material layer is 2.0 g / cm ³ (thickness of the positive electrode active material layer: 25 μm), a predetermined size is obtained. (2 cm × 2 cm) and vacuum-dried at 120 ° C. for 12 hours to produce a positive electrode plate of Comparative Example 1. The tripolar beaker cell of Comparative Example 1 was prepared in the same manner as in Example 1. It produced and used for the following charging / discharging test.

<Charge / discharge test>
Example 1
(Charge test)
After the tripolar beaker cell prepared in Example 1 was charged at a constant current (52 μA) under a 25 ° C. environment until the voltage reached 4.2 V, the voltage reached 4.2 V In order to prevent the voltage from exceeding 4.2V, the current (discharge rate: 1C) was reduced until it became 5% or less, charged at a constant voltage, fully charged, and then suspended for 10 minutes. .

(Discharge test)
Thereafter, the three-electrode beaker cell was kept at a constant current (52 μA) (discharge rate: 1 C) until the voltage changed from 4.2 V (full charge voltage) to 3.0 V (discharge end voltage) in an environment of 25 ° C. ), The cell voltage (V) is taken on the vertical axis, the discharge time (h) is taken on the horizontal axis, a discharge curve is created, and the discharge capacity (mAh) of the electrode plate for the positive electrode is obtained. It was converted into a discharge capacity (mAh / g) per weight of the plate.

  Here, “1C” means a current value (current value that reaches the discharge end voltage) at which the constant current discharge is performed using the tripolar beaker cell and the discharge is completed in one hour. .

  Based on the constant current discharge test at the constant current (52 μA) (discharge rate: 1 C, discharge end time: 1 hour) performed as described above, the constant current (1.04 mA) (discharge rate: 20 C, discharge end time: 3 Min), constant current (2.6 mA) (discharge rate: 50 C, discharge end time: 1.2 minutes), constant current (5.2 mA) (discharge rate: 100 C, discharge end time: 0.6 minutes) In the same manner, a constant current discharge test was performed.

(Comparative Example 1)
(Charge test)
In addition, the tripolar beaker cell manufactured in Comparative Example 1 was charged at a constant current (2.1 mA) under a 25 ° C. environment until the voltage reached 4.2 V, and the voltage was 4.2 V. In order to prevent the voltage from exceeding 4.2 V, the current (discharge rate: 1 C) is reduced until it becomes 5% or less, and charging is performed at a constant voltage, and after the battery is fully charged, 10 Paused for a minute.

(Discharge test)
Thereafter, the three-electrode beaker cell is kept at a constant current (2.1 mA) (discharge rate) until the voltage changes from 4.2 V (full charge voltage) to 3.0 V (discharge end voltage) in an environment of 25 ° C. 1C), the cell voltage (V) is taken on the vertical axis, the discharge time (h) is taken on the horizontal axis, a discharge curve is created, and the discharge capacity (mAh) of the positive electrode plate is obtained. The discharge capacity per unit weight (mAh / g) was converted.

  Based on the constant current discharge test with the constant current (2.1 mA) (discharge rate: 1 C, discharge end time: 1 hour) performed as described above, the constant current (4.16 mA) (discharge rate: 20 C, discharge end time) : 3 minutes), constant current (104 mA) (discharge rate: 50 C, discharge end time: 1.2 minutes), constant current (208 mA) (discharge rate: 100 C, discharge end time: 0.6 minutes) Each of them was subjected to a constant current discharge test.

(result)
Table 1 shows the results of the charge / discharge test of the tripolar beaker cell produced in Example 1 and Comparative Example 1.
The discharge capacity retention rate (%) in Table 1 is a value calculated by the following calculation formula 1, and was used as an index for evaluating the discharge rate characteristics of the positive electrode plate.

(Summary of results)
The positive electrode plate of Comparative Example 1 was a positive electrode plate that required more time for production than Example 1 and was composed of a positive electrode active material layer that was thicker than Example 1. .
Further, when the surface state of the positive electrode active material layer of the positive electrode plate produced in Comparative Example 1 was observed, voids were observed as shown in FIG.
On the other hand, in the method for producing a positive electrode plate of Example 1, the positive electrode plate can be produced in a short time, and the positive electrode active material layer can be formed without using a binder. As a result, the thickness of the positive electrode active material layer constituting the positive electrode plate could be reduced.
Furthermore, when the surface state of the positive electrode active material layer of the positive electrode plate produced in Example 1 was observed, as shown in FIG. 2, no abnormality such as a crack was confirmed, and the positive electrode active material layer and A desired positive electrode plate excellent in adhesion with the positive electrode current collector was obtained.

From the results of the charge / discharge test shown in Table 1, the following can be understood.
In the tripolar beaker cell produced in Example 1 and Comparative Example 1, the discharge capacity at the discharge rate 1C was the same value, but the tripolar beaker cell of Comparative Example 1 had a high discharge rate. As a result, the discharge capacity retention rate suddenly decreased, and the tripolar beaker cell was inferior in discharge rate characteristics.
On the other hand, the tripolar beaker cell of Example 1 is a tripolar beaker cell with excellent discharge rate characteristics, even if the discharge rate is increased, the decrease in the discharge capacity maintenance rate is not so great. there were.

FIG. 1 is a schematic view showing an example of a production apparatus used in the method for producing an electrode plate for a nonaqueous electrolyte secondary battery according to the present invention. FIG. 2 is a surface SEM photograph of the positive electrode active material layer constituting the positive electrode plate for a non-aqueous electrolyte secondary battery according to the present invention manufactured in Example 1. FIG. 3 is a surface SEM photograph of the positive electrode active material layer constituting the positive electrode plate for a non-aqueous electrolyte secondary battery manufactured by Comparative Example 1 using a conventional slurry method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrode plate manufacturing apparatus 2 Storage container of electrode active material layer forming liquid 3 Electrode active material layer forming liquid 4 Ultrasonic generator 5 Pressurizing device 6 Pipe 7 Nozzle 8 Atomized droplet 9 Atmosphere immediately above current collector 10 Hot plate 11 Current collector 12 Electrode active material 13 Electrode active material layer

Claims (1)

A method for producing a non-aqueous electrolyte secondary battery using, as a positive electrode plate, a non-aqueous electrolyte secondary battery electrode plate provided with a positive electrode active material layer on a current collector,
As a positive electrode active material, a positive electrode active material layer forming liquid containing a raw material for producing a lithium composite oxide containing at least one of cobalt, nickel, manganese, iron or titanium is used as a solvent for the positive electrode active material layer forming liquid. And spraying on at least one surface side of the current collector heated to 500 to 600 ° C., and applying the positive electrode active material forming liquid to the one surface side Attach
Chemically reacting the raw material in the positive electrode active material layer forming liquid attached to the one surface side by the heat of the current collector to produce a positive electrode active material on the current collector;
The positive electrode active material generated on the current collector is heated again to 400 to 600 ° C. for crystallization to form the positive electrode active material layer. Production method.