JP4945016B1 - Method for producing positive electrode current collector for non-aqueous electrolyte secondary battery and method for producing positive electrode for non-aqueous electrolyte secondary battery - Google Patents

Abstract

Provided are a method for producing a positive electrode current collector for a non-aqueous electrolyte secondary battery and a method for producing a positive electrode for a non-aqueous electrolyte secondary battery that can improve the electron conductivity between the active material and the current collector.
The method for producing a positive electrode current collector for a non-aqueous electrolyte secondary battery according to the present invention is a method for producing a positive electrode current collector for a non-aqueous electrolyte secondary battery in which the surface of an aluminum current collecting base material is roughened with an etching agent. The etching agent is an alkaline aqueous etching agent containing an alkali source and amphoteric metal ions, and a ferric ion aqueous solution containing a ferric ion source, a cupric ion source, a manganese ion source, and an inorganic acid. It is 1 type or more chosen from a system type etching agent.
[Selection] Figure 3

Description

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

  Nonaqueous electrolyte secondary batteries are used in various electronic devices such as mobile phones and laptop computers as portable power sources because they can withstand heavy load discharge and can be repeatedly used by charging. As these electronic devices are being made smaller and lighter one after another, non-aqueous electrolyte secondary batteries as portable power sources will be further reduced in size, weight, and energy density. There is an increasing demand.

  In recent years, electric vehicles, hybrid vehicles, fuel cell vehicles, and the like have attracted attention due to soaring petroleum resources and the increasing global environmental protection movement, and some of them have been put into practical use. In these drive systems, a secondary battery is indispensable as an auxiliary power source and the like, and a high-power secondary battery that can cope with sudden start / acceleration of an automobile is desired. From such a background, non-aqueous electrolyte secondary batteries that have the highest energy density among the secondary batteries and are capable of expressing high output are promising.

  Among non-aqueous electrolyte secondary batteries that meet these requirements, lithium ion secondary batteries, in particular, are widely used because of their high energy density, and the market is growing significantly.

  The positive electrode of a lithium ion secondary battery usually has a lithium-containing transition such as lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium iron oxide, or lithium iron phosphate on a current collector made of aluminum or the like. It is obtained by forming an active material layer containing a metal compound. For example, in Patent Document 1 below, the surface of the current collector is anodized in hydrochloric acid in order to prevent deterioration of the adhesion at the interface between the active material and the current collector due to expansion and contraction of the active material due to charge and discharge. And a method for producing a positive electrode in which an active material layer is formed on the roughened surface after roughening.

JP 2008-210564 A

  However, the inventors have found that it is difficult to improve the electron conductivity between the active material and the current collector in the conventional positive electrode manufacturing method.

  The present invention has been made in view of the above circumstances, and a method for producing a positive electrode current collector for a non-aqueous electrolyte secondary battery capable of improving electronic conductivity between an active material and a current collector, A method for producing a positive electrode for a non-aqueous electrolyte secondary battery is provided.

The method for producing a positive electrode current collector for a non-aqueous electrolyte secondary battery according to the present invention is a method for producing a positive electrode current collector for a non-aqueous electrolyte secondary battery in which the surface of an aluminum current collecting base material is roughened with an etching agent. There,
An aqueous alkaline etching agent containing an alkali source and amphoteric metal ions, and an aqueous ferric ion etching agent containing a ferric ion source, a cupric ion source, a manganese ion source, and an inorganic acid. Is a method for producing a positive electrode current collector for a non-aqueous electrolyte secondary battery.

A method for producing a positive electrode for a non-aqueous electrolyte secondary battery according to the present invention is a method for producing a positive electrode for a non-aqueous electrolyte secondary battery in which an active material layer is formed on an aluminum positive electrode current collector,
The aluminum positive electrode current collector is a positive electrode current collector obtained by the method for producing a positive electrode current collector for a non-aqueous electrolyte secondary battery of the present invention,
It is a manufacturing method of the positive electrode for nonaqueous electrolyte secondary batteries which forms the said active material layer on the roughened surface of the said positive electrode electrical power collector.

  The “aluminum” in the present invention may be made of aluminum or an aluminum alloy. In this specification, “aluminum” refers to aluminum or an aluminum alloy.

  According to the method for producing a positive electrode current collector for a nonaqueous electrolyte secondary battery and the method for producing a positive electrode for a nonaqueous electrolyte secondary battery according to the present invention, the surface of the aluminum current collector substrate is roughened with a specific etching agent. Therefore, it is considered that the electron conductivity between the active material and the current collector can be improved by increasing the contact area between the current collector and the active material.

It is the scanning electron micrograph which image | photographed the roughening surface of the electrical power collector of Example 1 on the conditions of magnification: 3500 times and imaging | photography angle: 45 degrees. It is the scanning electron micrograph which image | photographed the roughened surface of the electrical power collector of Example 2 on the conditions of magnification: 3500 times and imaging | photography angle: 45 degrees. It is the scanning electron micrograph which image | photographed the roughening surface of the electrical power collector of Example 3 on the conditions of magnification: 3500 times and imaging | photography angle: 45 degrees. It is the scanning electron micrograph which image | photographed the roughening surface of the electrical power collector of Example 3 on the conditions of magnification: 10000 time and imaging | photography angle: directly above. It is the scanning electron micrograph which image | photographed the cross section of the electrical power collector of Example 3 on the conditions of magnification: 3500 times. It is the scanning electron micrograph which image | photographed the roughening surface of the electrical power collector of Example 4 on the conditions of magnification: 3500 times and imaging | photography angle: 45 degrees. It is the scanning electron micrograph which image | photographed the roughening surface of the electrical power collector of Example 5 on the conditions of magnification: 3500 times and imaging | photography angle: 45 degrees. 4 is a scanning electron micrograph of the surface of the current collector of Comparative Example 1 taken under conditions of a magnification of 3500 times and an imaging angle of 45 °. It is a scanning electron micrograph which image | photographed the roughened surface of the electrical power collector of the comparative example 2 on the conditions of magnification: 3500 times and imaging | photography angle: 45 degrees. It is a scanning electron micrograph which image | photographed the roughening surface of the electrical power collector of the comparative example 3 on the conditions of magnification: 3500 times and imaging | photography angle: 45 degrees. It is the scanning electron micrograph which image | photographed the roughening surface of the electrical power collector of Example 12 on the conditions of magnification: 3500 times and imaging | photography angle: 45 degrees. It is the scanning electron micrograph which image | photographed the roughening surface of the electrical power collector of Example 12 on magnification: 10000 time and imaging | photography angle: directly above. It is the scanning electron micrograph which image | photographed the cross section of the electrical power collector of Example 12 on the conditions of magnification: 3500 times. It is the scanning electron micrograph which image | photographed the roughened surface of the electrical power collector of Example 13 on conditions with a magnification of 3500 times and an imaging angle of 45 degrees. It is the scanning electron micrograph which image | photographed the roughening surface of the electrical power collector of Example 13 on magnification | multiplying_factor: 10000 time and imaging | photography angle: directly above. It is the scanning electron micrograph which image | photographed the cross section of the electrical power collector of Example 13 on the conditions of magnification: 3500 times.

[Aluminum current collector]
The aluminum current collecting base material (hereinafter also simply referred to as “base material”) that can be used in the present invention is not particularly limited as long as it can be used for the positive electrode of the nonaqueous electrolyte secondary battery, and various shapes can be used. . For example, a base material having a foil shape, an expanded metal shape, a punching metal shape, a foam metal shape, a net shape, or the like can be used, and a foil-like base material is preferable from the viewpoint of forming a uniform roughened surface. In addition, the thickness of the substrate that can be used in the present invention is preferably 10 μm or more, and more preferably 15 μm or more from the viewpoint of obtaining sufficient strength. Moreover, from a viewpoint of raising the filling amount of an active material, 50 micrometers or less are preferable and 30 micrometers or less are more preferable.

[Etching agent]
In this invention, 1 or more types chosen from the said alkaline aqueous solution type etching agent and said ferric ion aqueous solution type etching agent are used as an etching agent which roughens a base material. In the present invention, since the surface of the aluminum current collector substrate is roughened with the specific etching agent, the contact area between the current collector and the active material is increased, and electrons between the active material and the current collector are increased. It is thought that conductivity can be improved. From the viewpoint of obtaining a good roughened shape suitable for electron conduction, it is preferable to use the alkaline aqueous solution type etching agent as the etching agent. Hereinafter, each component of the etching agent that can be used in the present invention will be described.

(Alkali aqueous etchant)
First, the alkaline aqueous etching agent will be described. The alkaline aqueous etching agent contains an alkali source and an amphoteric metal ion, and may contain a thio compound, an oxidizing agent, various additives, and the like as necessary.

<Alkali source>
Although it does not specifically limit as an alkali source, NaOH and KOH are preferable from a viewpoint of the solubility of aluminum, and a viewpoint of cost reduction. From the viewpoint of obtaining a good roughened shape, the content of the alkali source is preferably 0.60% by weight or more, more preferably 1.45% by weight or more as a hydroxide ion. More preferably, it is 50% by weight or more. Further, from the viewpoint of obtaining an appropriate roughening treatment rate, the content of the alkali source is preferably 22.80% by weight or less, more preferably 16.30% by weight or less as hydroxide ions. More preferably, it is 12.25% by weight or less.

<Amotropic metal ions>
The amphoteric metal ions are not particularly limited as long as they are other than Al ions, and examples thereof include Zn ions, Pb ions, Sn ions, Sb ions, Cd ions, etc., and a viewpoint of obtaining a good roughened shape suitable for electron conduction. In view of reducing the environmental load, Zn ions and Sn ions are preferable, and Zn ions are more preferable. The content of amphoteric metal ions is preferably 0.2% by weight or more, more preferably 0.5% by weight or more, from the viewpoint of obtaining a good roughened shape suitable for electron conduction. More preferably, it is 0.0% by weight or more. Further, from the viewpoint of obtaining an appropriate roughening treatment rate, the content of amphoteric metal ions is preferably 6.0% by weight or less, more preferably 4.4% by weight or less, 3.5 More preferably, it is not more than% by weight.

  Amphoteric metal ions can be contained in an alkaline aqueous etching agent by blending an amphoteric metal ion source. Examples of amphoteric metal ion sources include zinc nitrate, zinc borate, zinc chloride, zinc sulfate, zinc bromide, basic zinc carbonate, zinc oxide, zinc sulfide and the like in the case of a Zn ion source. In the case of Sn ion source, tin chloride (IV), tin chloride (II), tin acetate (II), tin bromide (II), tin diphosphate (II), tin oxalate (II), oxidation Examples include tin (II), tin (II) iodide, tin (II) sulfate, tin (IV) sulfide, and tin (II) stearate.

<Thio compound>
The alkaline aqueous etching agent that can be used in the present invention may be blended with a thio compound from the viewpoint of obtaining a good roughened shape suitable for electron conduction by performing a fine roughening treatment. When the thio compound is blended, from the same viewpoint, the content of the thio compound is preferably 0.05% by weight or more, more preferably 0.1% by weight or more, and 0.2% by weight or more. More preferably. From the same viewpoint, the content of the thio compound is preferably 25.0% by weight or less, more preferably 20.0% by weight or less, and further preferably 15.0% by weight or less.

  The thio compound is not particularly limited, but is preferably one or more selected from thiosulfate ions and thio compounds having 1 to 7 carbon atoms from the viewpoint of obtaining a good roughened shape suitable for electron conduction, It is more preferable that it is 1 or more types selected from a thiosulfate ion and a C1-C3 thio compound. Among these, ions such as thiosulfate ions can be contained in the alkaline aqueous etching agent by blending the ion source.

  Examples of the thio compounds having 1 to 7 carbon atoms include thiourea (carbon number 1), ammonium thioglycolate (carbon number 2), thioglycolic acid (carbon number 2), thioglycerol (carbon number 3), and L-thioproline. (Carbon number 4), dithiodiglycolic acid (carbon number 4), β, β′-thiodipropionic acid (carbon number 5), sodium N, N-diethyldithiocarbamate trihydrate (carbon number 5), 3,3′-dithiodipropionic acid (carbon number 6), 3,3′-dithiodipropanol (carbon number 6), o-thiocresol (carbon number 7), p-thiocresol (carbon number 7), etc. Can be mentioned.

<Oxidizing agent>
The alkaline aqueous etching agent that can be used in the present invention may contain an oxidizing agent in order to redissolve the amphoteric metal that precipitates on the substrate surface by a substitution reaction with aluminum during the roughening treatment of aluminum. . When the oxidizing agent is blended, the content of the oxidizing agent is preferably 0.5% by weight or more, more preferably 1.0% by weight or more, from the viewpoint of resolubility of the amphoteric metal. More preferably, it is 0.0% by weight or more. Further, from the viewpoint of obtaining a good roughened shape suitable for electron conduction, the content of the oxidizing agent is preferably 10.0% by weight or less, more preferably 8.4% by weight or less, More preferably, it is 6.0% by weight or less.

Examples of the oxidizing agent include chloric acid such as chlorous acid and hypochlorous acid and salts thereof, oxidizable metal salts such as permanganate, chromate, dichromate and cerium (IV) salt, nitro group Examples thereof include peroxides such as contained compounds, hydrogen peroxide and persulfate, and nitrate ions. Of these, nitrate ions are preferred from the viewpoint of stability in an alkaline aqueous etching agent.

  Nitrate ions can be contained in an alkaline aqueous etching agent by blending a nitrate ion source. Examples of nitrate ion sources include nitric acid, sodium nitrate, potassium nitrate, barium nitrate, calcium nitrate, ammonium nitrate, and zinc nitrate.

A surfactant may be added to the alkaline aqueous etching agent that can be used in the present invention to prevent unevenness due to surface contaminants such as fingerprints, and other additives may be added as necessary. . Other additives include additives for suppressing sludge generation associated with aluminum dissolution, such as monoethanolamine, diethanolamine, alkanolamines such as triethanolamine, azoles such as imidazole, citric acid, malic acid, glucone. Examples thereof include oxycarboxylic acids such as acids and salts thereof. When these other components are added, the content is preferably about 0.1 to 5% by weight.

  The alkaline aqueous etching agent that can be used in the present invention can be easily prepared by dissolving the above-described components in ion-exchanged water or the like.

(Ferric ion aqueous solution based etchant)
Next, the ferric ion aqueous solution type etching agent will be described. The ferric ion aqueous solution-based etching agent contains a ferric ion source, a cupric ion source, a manganese ion source, and an inorganic acid, and may contain various additives as necessary.

<Ferric ion source>
The ferric ion source in the aqueous ferric ion solution-based etchant that can be used in the present invention is a component that oxidizes aluminum. Examples of the ferric ion source include ferric nitrate, ferric sulfate, and ferric chloride. Among the ferric ion sources, ferric chloride is preferable because it has excellent solubility and is inexpensive.

  The content of the ferric ion source is preferably 1.5 to 9.0% by weight as iron ions, more preferably 2.5 to 7.0% by weight, still more preferably 4.0 to 6%. 0.0% by weight. If the said content is 1.5 weight% or more, the fall of the roughening rate (dissolution rate) of aluminum can be prevented. On the other hand, when the content is 9.0% by weight or less, the roughening rate can be properly maintained, and thus uniform roughening is possible.

<Copper ion source>
The cupric ion source in the ferric ion aqueous solution etchant that can be used in the present invention is a component for quickly removing the oxide film formed on the substrate surface before the treatment. Examples of the cupric ion source include cupric sulfate, cupric chloride, cupric nitrate, and cupric hydroxide. Of the cupric ion sources, cupric sulfate is preferred because it is inexpensive.

  The content of the cupric ion source is preferably 0.05 to 1.0% by weight as copper ions, more preferably 0.10 to 0.8% by weight, and still more preferably 0.15 to 0. 4% by weight. When the content is 0.05% by weight or more, the oxide layer can be easily removed. On the other hand, if the content is 1.0% by weight or less, substitutional precipitation of metallic copper on the substrate surface can be prevented.

<Manganese ion source>
The manganese ion source in the ferric ion aqueous solution-based etching agent that can be used in the present invention is a component for uniformly roughening the surface of the substrate. Examples of the manganese ion source include manganese sulfate, manganese chloride, manganese acetate, manganese fluoride, and manganese nitrate. Of the manganese ion sources, manganese sulfate and manganese chloride are preferable because they are inexpensive.

  The content of the manganese ion source is preferably 0.02 to 1.5% by weight as manganese ions, more preferably 0.06 to 0.6% by weight, and still more preferably 0.10 to 0.5% by weight. %. If the said content is 0.02 weight% or more, the effect of adding a manganese ion source can fully be exhibited. On the other hand, if the content is 1.5% by weight or less, cost reduction is facilitated.

<Inorganic acid>
The inorganic acid in the aqueous ferric ion solution-based etchant that can be used in the present invention is a component that dissolves aluminum oxidized by ferric ions. Examples of the inorganic acid include hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, perchloric acid, sulfamic acid, and the like. Of the inorganic acids, sulfuric acid is preferred because it has almost no odor and is inexpensive.

  The content of the inorganic acid is preferably 5 to 30% by weight, more preferably 7 to 25% by weight, and still more preferably 12 to 18% by weight. When the content is 5% by weight or more, it is possible to prevent a decrease in the roughening rate (dissolution rate) of aluminum. On the other hand, when the content is 30% by weight or less, crystallization of the aluminum salt can be prevented when the liquid temperature is lowered, so that workability can be improved.

  A surfactant may be added to the ferric ion aqueous solution etchant that can be used in the present invention to prevent unevenness due to surface contaminants such as fingerprints, and other additives may be added as necessary. May be.

  The ferric ion aqueous solution type etching agent of the present invention can be easily prepared by dissolving each of the above components in ion exchange water or the like.

  Next, a method for roughening the surface of the substrate using the above-described etching agent will be described. First, the case of using an alkaline aqueous etching agent will be described.

  When roughening using an alkaline aqueous etching agent, if there is significant contamination such as machine oil on the surface of the substrate to be treated, degreasing and then roughening with the alkaline aqueous etching agent. Just do it. Examples of the roughening treatment method include treatment methods such as immersion and spraying. The treatment temperature is preferably 20 to 40 ° C., and the treatment time is preferably about 10 to 300 seconds. After the treatment, washing and drying are usually performed.

  In the present invention, it is preferable that the roughened surface is acid-washed for the purpose of removing the precipitated amphoteric metal after the roughening treatment using an alkaline aqueous etching agent. The acid used for the acid cleaning is not particularly limited as long as it can dissolve amphoteric metals, but in particular, roughening with one or more aqueous solutions selected from nitric acid aqueous solution, sulfuric acid aqueous solution, and aqueous solution containing sulfuric acid and hydrogen peroxide It is preferable to treat the surface. This is because the amphoteric metal deposited on the substrate surface can be removed and the substrate surface can be repassivated at the same time, so that the oxidation resistance against a high potential can be improved. Examples of the treatment of the aqueous solution include treatment by dipping, spraying, and the like. The treatment temperature is preferably 20 to 40 ° C., and the treatment time is preferably about 5 to 40 seconds. After the treatment, washing and drying are usually performed.

  In the case of using an aqueous nitric acid solution, the concentration of nitric acid is preferably 5 to 65% by weight and more preferably 25 to 45% by weight from the viewpoint of amphoteric metal removal performance and corrosiveness to aluminum. In the case of using an aqueous sulfuric acid solution, the concentration of sulfuric acid is preferably 5 to 60% by weight and more preferably 20 to 40% by weight from the viewpoint of amphoteric metal removal performance and corrosiveness to aluminum.

  When using an aqueous solution containing sulfuric acid and hydrogen peroxide, the concentration of sulfuric acid is preferably 5 to 60% by weight from the viewpoint of amphoteric metal removal performance and corrosiveness to aluminum, and is 20 to 40% by weight. It is more preferable. From the same viewpoint, the concentration of hydrogen peroxide is preferably 1 to 40% by weight, and more preferably 5 to 30% by weight.

  In the present invention, after the roughened surface is treated with one or more aqueous solutions selected from the above-described acid cleaning, particularly an aqueous nitric acid solution, an aqueous sulfuric acid solution, and an aqueous solution containing sulfuric acid and hydrogen peroxide, the treated surface is further treated. Anodization treatment (alumite treatment) may be performed. When the anodizing treatment is performed, the oxidation resistance against a high potential can be further improved.

  In the present invention, after the roughening treatment using an alkaline aqueous etching agent, hydrohalic acid such as hydrochloric acid and hydrobromic acid, or one or more metals selected from alkali metals and alkaline earth metals are used. The roughened surface may be cleaned using an alkaline aqueous solution containing a hydroxide. When the roughened surface is washed with hydrohalic acid or an alkaline aqueous solution, the roughened surface is slightly etched, so that the shape of the roughened surface can be controlled. Thereby, the roughened surface shape suitable for the magnitude | size and shape of the positive electrode active material particle to be used can be formed. In order to form a roughened surface having deeper recesses, it is preferable to treat with hydrohalic acid. The alkaline aqueous solution is an aqueous solution not containing amphoteric metal ions.

  In the case of cleaning with the hydrohalic acid, it is preferable to use hydrohalic acid having a hydrogen halide concentration of 1 to 35% by weight from the viewpoint of easily controlling the shape of the roughened surface. Hydrochloric acid is preferably hydrochloric acid from the viewpoints of cost and handling.

  When washing with the hydrohalic acid, examples of the treatment method include treatment by dipping, spraying, and the like. The treatment temperature is preferably 20 to 40 ° C., and the treatment time is preferably about 5 to 300 seconds. After the treatment, washing and drying are usually performed.

  When washing with the alkaline aqueous solution, it is preferable to use an alkaline aqueous solution having a hydroxide concentration of 1 to 48% by weight from the viewpoint of easily controlling the shape of the roughened surface. As the hydroxide, potassium hydroxide and sodium hydroxide are preferable from the viewpoints of cost and handling.

  In the case of washing with the alkaline aqueous solution, examples of the treatment method include treatment by dipping and spraying. The treatment temperature is preferably 20 to 40 ° C., and the treatment time is preferably about 5 to 300 seconds. After the treatment, washing and drying are usually performed. Moreover, when wash | cleaning a roughened surface with the said alkaline aqueous solution, it is preferable to further acid-wash the roughened surface after washing | cleaning. This is because the amphoteric metal deposited by the treatment with the alkaline aqueous etching agent can be removed. The acid used for the acid cleaning, the treatment conditions, and the like are the same as in the case of the acid cleaning performed for the purpose of removing the amphoteric metal described above.

  Next, the case where a ferric ion aqueous solution type etching agent is used is demonstrated. Even when using ferric ion aqueous solution type etching agent, if there is significant contamination such as machine oil on the substrate surface of the object to be treated, after degreasing, roughening with ferric ion aqueous solution type etching agent What is necessary is just to process. Examples of the roughening treatment method include treatment methods such as immersion and spraying. The treatment temperature is preferably 20 to 30 ° C., and the treatment time is preferably about 10 to 300 seconds. After the treatment, washing and drying are usually performed.

  When roughening is performed using a ferric ion aqueous solution-based etching agent, the unevenness of the substrate surface may become too fine. In such a case, it is fine with a sodium hydroxide aqueous solution having a concentration of about 1 to 5% by weight. Only the excessive portion should be dissolved and removed. In this case, it is preferable that the smut remaining on the surface after the treatment with an aqueous sodium hydroxide solution is dissolved and removed with dilute nitric acid. The ferric ion aqueous solution etchant after roughening the substrate can easily aggregate and precipitate dissolved aluminum by adding sodium hydroxide, calcium hydroxide, etc. to neutralize it. The waste liquid treatment is easy.

  The surface of the base material is roughened into a concavo-convex shape by a roughening treatment using the alkaline aqueous solution type etching agent or the ferric ion aqueous solution type etching agent. In this case, the etching amount (dissolution amount) of the aluminum in the depth direction is preferably 0.1 to 3.0 μm when calculated from the weight, specific gravity and surface area of the dissolved aluminum, and 0.2 to 2. More preferably, it is 5 micrometers, and it is still more preferable that it is 0.5-2.0 micrometers. If the etching amount is within the above range, a good roughened shape suitable for electron conduction can be obtained. The etching amount can be adjusted by the processing temperature, processing time, and the like.

  In the present invention, when the substrate is roughened using the alkaline aqueous solution-based etchant or the ferric ion aqueous solution-based etchant, the entire surface of the substrate may be roughened, and the active material layer Only the surface on which is formed may be partially roughened.

  Moreover, in this invention, you may use together the process by the said aqueous alkali solution type etching agent, and the process by a ferric-ion aqueous solution type etching agent. The order of processing in this case is not limited. In addition, wet etching with other etching agents and various dry etchings may be used in combination as long as the effects of the present invention are not impaired.

  The positive electrode current collector for a non-aqueous electrolyte secondary battery obtained by the roughening treatment described above (hereinafter also simply referred to as “current collector”) is formed by forming an active material layer on the roughened surface. Thus, a positive electrode for a non-aqueous electrolyte secondary battery (hereinafter also simply referred to as “positive electrode”) is obtained. Hereinafter, an embodiment of a method for producing a positive electrode will be described using a positive electrode for a lithium ion secondary battery as an example.

The active material constituting the active material layer of the positive electrode for a lithium ion secondary battery is not particularly limited as long as it has a function of occluding and releasing lithium, and examples thereof include metal chalcogenide-based positive electrode materials. Specifically, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium iron oxide, lithium-containing nickel cobalt composite oxide (binary positive electrode material), lithium-containing nickel manganese cobalt composite oxide (three Primary cathode material), or lithium-containing transition metal compounds such as lithium-containing olivine transition metal phosphates such as lithium iron phosphate and lithium manganese phosphate; transition metal compounds such as manganese dioxide; carbonaceous materials such as graphite fluoride Materials etc. can be used. More specifically, LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiFeO ₂ , LiFePO ₄ , and these non-stoichiometric compounds and transition metals obtained by substituting some of the transition metals contained therein with other transition metals _compounds, using _{MnO 2, TiS 2, FeS 2} , Nb 3 S 4, Mo 3 S 4, CoS 2, V 2 O 5, P 2 O 5, CrO 3, V 3 O 3, TeO 2, GeO 2 , etc. be able to. These may be used alone or in combination of two or more. Of these, lithium-containing transition metal compounds are preferred from the viewpoint of excellent thermal stability, capacity, and output characteristics. In addition, lithium iron phosphate has higher electron conduction resistance than other lithium-containing transition metal compounds. However, when the current collector obtained by the method of the present invention is used, an active material containing lithium iron phosphate and a collector are collected. It is possible to improve electronic conductivity with the electric body. That is, even if an active material having a high electron conduction resistance such as lithium iron phosphate is used, according to the present invention, the contact area between the current collector and the active material is increased. It is considered that the electron conductivity can be improved.

  A conductive agent can also be used as a constituent material of the active material layer. The conductive agent may be anything as long as it is an electron conductive material that does not cause a chemical change at the charge / discharge potential of the active material used. For example, natural graphite (such as flake graphite), graphite such as artificial graphite, carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, metal fiber, etc. Conductive fibers, metal powders such as carbon fluoride and aluminum, conductive whiskers such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide, organic conductive materials such as polyphenylene derivatives, etc. Can be included alone or as a mixture thereof. Among these conductive agents, artificial graphite and acetylene black are particularly preferable. Although the addition amount of a electrically conductive agent is not specifically limited, 1-50 weight part is preferable with respect to 100 weight part of active materials, and 1-30 weight part is more preferable.

  The method for forming the active material layer on the roughened surface of the current collector is not particularly limited, and a known active material layer forming method can be employed. For example, an active material, a conductive agent, a binder, and a solvent are mixed. It is possible to adopt a method in which a slurry is prepared, and this slurry is applied and dried on the roughened surface of the current collector.

  As the binder, any of conventional binders used for forming a positive electrode can be used, but polyvinylidene fluoride (PVDF), polyamideimide, polytetrafluoroethylene, polyethylene, polypropylene, polymethyl methacrylate, and the like are preferable. Can be used. As content of a binder, 1-20 weight part is preferable with respect to 100 weight part of active materials, and 1-10 weight part is more preferable.

  As the solvent, any conventional solvent used for forming a positive electrode can be used. For example, N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide, methyl ethyl ketone, tetrahydrofuran, acetone, ethanol , Ethyl acetate and the like are preferably used. Any conventionally known additive used for forming the positive electrode can be added to the slurry.

  The viscosity of the slurry at 25 ° C. is preferably 1000 mPa · s or more, and more preferably 2000 mPa · s or more, from the viewpoint of adjusting the thickness of the obtained active material layer to an appropriate range. Further, from the viewpoint of applicability to the current collector, the viscosity is preferably 15000 mPa · s or less, and more preferably 10000 mPa · s or less. The thickness of the active material layer is usually 1 μm or more, preferably 3 μm or more, and is usually 100 μm or less, preferably 80 μm or less, more preferably 60 μm or less.

  The solid content concentration of the slurry is preferably 20 to 60% by weight, more preferably 25 to 55% by weight, from the viewpoint of preferable slurry viscosity.

  The positive electrode obtained by the above method is laminated (or wound) together with the negative electrode and the separator in the manufacturing process of the lithium ion secondary battery. And a lithium ion secondary battery is manufactured by inject | pouring electrolyte solution, a polymer electrolyte, etc. into this laminated body (or wound body).

  Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. For example, in the above embodiment, the method of forming the active material layer directly on the base material has been described as an example. However, an intermediate layer made of graphite or the like is formed on the base material, and the active material layer is formed on the intermediate layer. It may be formed.

  Moreover, although the said embodiment demonstrated the positive electrode for lithium ion secondary batteries as an example, this invention optimizes a collector surface structure and is between collector / active material layers (or intermediate | middle layer). This is a technique for improving the electron conductivity between the active material and the current collector by controlling the interface, and is not limited to a positive electrode for a lithium ion secondary battery. For example, the present invention can also be applied to a positive electrode for a nonaqueous electrolyte secondary battery other than a lithium ion secondary battery such as a magnesium ion secondary battery or a calcium ion secondary battery.

  Next, examples of the present invention will be described together with comparative examples. In addition, this invention is limited to a following example and is not interpreted.

(Preparation of current collector)
First, an aqueous solution having the composition shown in Table 1 was prepared. In the obtained aqueous solution (30 ° C.), an aluminum foil (thickness 20 μm) defined in JIS A1050H H18 is immersed and shaken, and after etching by the etching amount shown in Table 1, it is washed with water and 35% by weight Was immersed in a nitric acid aqueous solution (30 ° C.), rocked for 20 seconds, washed with water and dried. Among the obtained current collectors, the roughened surfaces of the current collectors of Examples 1 to 5 and Comparative Examples 1 to 3 were observed using a scanning electron microscope (SEM). SEM photographs at that time are shown in FIGS. Although all of the examples were roughened uniformly, Comparative Example 2 and Comparative Example 3 had uneven unevenness.

(Preparation of positive electrode)
First, LiMn ₂ O ₄ (64.0% by weight), acetylene black (3.6% by weight), polyvinylidene fluoride (4.0% by weight), and N-methyl-2-pyrrolidone (28.4% by weight) Were mixed to prepare a positive electrode active material slurry. Next, the slurry was applied on the roughened surface of the current collector and dried to obtain a positive electrode (14 mm × 20 mm) in which an active material layer having a thickness of 60 μm was formed on the current collector. In addition, the density of the active material layer of the obtained positive electrode was 2.4 g / cm ³ .

(Measurement of AC impedance)
Using a cell test system 147060BEC type manufactured by Solartron, an alternating current of 0.1 Hz, 1.0 Hz, 1 kHz, and 20 kHz was applied to the positive electrode in an atmosphere at 25 ° C., and the alternating current impedance was measured. The results are shown in Table 2. Note that the AC impedance in the high-frequency region tends to be easily affected by resistance mainly derived from electron conduction because ion conduction in the active material layer is suppressed.

  As shown in Table 2, in the frequency region of 1 kHz or more, all of the examples were able to reduce the AC impedance value as compared with the comparative example.

(Production of test cell)
First, mesocarbon microbeads (65.7% by weight), acetylene black (1.4% by weight), polyvinylidene fluoride (3.5% by weight), and N-methyl-2-pyrrolidone (29.4% by weight) Were mixed to prepare a negative electrode active material slurry. Next, the slurry was applied on a rolled copper foil (no surface treatment) having a thickness of 20 μm and dried to obtain a negative electrode (14 mm × 21 mm) in which an active material layer having a thickness of 35 μm was formed on the rolled copper foil. In addition, the density of the active material layer of the obtained negative electrode was 1.3 g / cm ³ . Next, a mixture of the negative electrode, a positive electrode obtained by the same method as the positive electrode used for the AC impedance measurement, a porous polyethylene separator, ethylene carbonate (EC), and methyl ethyl carbonate (MEC). A test cell was assembled using an electrolyte obtained by dissolving 1M LiPF ₆ in a solvent (volume ratio EC: MEC = 3: 7). At this time, the facing area (electrode effective area) was 2.8 cm ^2, and an aluminum laminate was used as the exterior material.

(Measurement of internal resistance by current pause method)
Using a cell test system 147060BEC manufactured by Solartron, internal resistance was measured by the following method. First, after the test cell was fully charged, discharge under a load of 0.5 C (current amount to be fully discharged in 2 hours) was performed in an atmosphere at 25 ° C., and the discharge was stopped 12 minutes after the start of discharge. The internal resistance of the cell was measured based on the voltage change. At this time, the component in which the voltage is instantaneously recovered at the same time as the discharge is stopped is defined as an ohmic component, the component in which the voltage is gradually recovered thereafter is defined as an equilibrium component, and the sum thereof is defined as the internal resistance by the current pause method. The results are shown in Table 3. The ohmic component mainly represents resistance derived from electron conduction, and the equilibrium component represents resistance mainly derived from ion conduction inside the cell.

  As shown in Table 3, all of the examples were able to reduce the resistance value of the ohmic component as compared with the comparative example. From this result, it was confirmed that the electron conductivity between the active material and the current collector can be improved according to the present invention.

  Next, the results of evaluating the internal resistance of the cell using the current collectors of the above examples and comparative examples and using lithium iron phosphate as the active material will be described.

First, olivine-type lithium iron phosphate (56.3% by weight), acetylene black (5.3% by weight), polyvinylidene fluoride (4.6% by weight), and N-methyl-2-pyrrolidone (33.8% by weight) ) Was mixed to prepare a positive electrode active material slurry. Next, the positive electrode (14 mm × 20 mm) in which an active material layer having a thickness of 50 μm was formed on the current collector by applying the slurry on the roughened surface of each current collector of the above Examples and Comparative Examples and drying the slurry. Got. In addition, the density of the active material layer of the obtained positive electrode was 2.0 g / cm ³ .

  Next, a test cell was prepared in the same manner as described above, and the internal resistance was measured by the current pause method in the same manner as described above. The results are shown in Table 4.

  As shown in Table 4, all of the examples were able to significantly reduce the resistance value of the ohmic component as compared with the comparative example. From this result, it was confirmed that the electron conductivity between the active material and the current collector can be improved according to the present invention.

  Next, the results of evaluating the high rate discharge characteristics of the cell using lithium-containing nickel manganese cobalt composite oxide as the active material will be described.

(Preparation of current collector of Example 12)
First, an aqueous solution having the same composition as in Example 2 was prepared. In the obtained aqueous solution (30 ° C.), an aluminum foil (thickness 20 μm) defined in JIS A1050H H18 was immersed and swung, and etched by an etching amount of 1.0 μm (equivalent to 2.70 g / m ² ). After that, it was washed with water. Subsequently, it was immersed in hydrochloric acid (hydrogen chloride concentration: 7% by weight) at 25 ° C., rocked for 30 seconds, washed with water and dried to obtain a current collector of Example 12. The roughened surface of the current collector of Example 12 obtained was observed using a scanning electron microscope (SEM). SEM photographs at that time are shown in FIGS.

(Preparation of current collector of Example 13)
First, an aqueous solution having the same composition as in Example 2 was prepared. In the obtained aqueous solution (30 ° C.), an aluminum foil (thickness 20 μm) defined in JIS A1050H H18 was immersed and swung, and etched by an etching amount of 1.0 μm (equivalent to 2.70 g / m ² ). After that, it was washed with water. Next, it was immersed in a 5% by weight sodium hydroxide aqueous solution (25 ° C.), rocked for 2 minutes, washed with water, and further immersed in a 35% by weight nitric acid aqueous solution (30 ° C.) for 20 seconds. The current collector of Example 13 was obtained by rocking, washing with water and drying. The roughened surface of the current collector obtained in Example 13 was observed using a scanning electron microscope (SEM). SEM photographs at that time are shown in FIGS.

  Using the current collectors of Examples 12 and 13 obtained above and the current collectors of Example 3 and Comparative Example 1 described above, a positive electrode was produced, and a test cell was produced using the positive electrode to obtain a high rate of the cell. The discharge characteristics were evaluated. Details are shown below.

(Preparation of positive electrode)
LiNi _1/3 Mn _1/3 Co _1/3 O ₂ (42.8 wt%), acetylene black (3.5 wt%), polyvinylidene fluoride (3.5 wt%) and N-methyl-2-pyrrolidone (50.2 wt%) was mixed to prepare a positive electrode active material slurry. Next, after punching the current collector into a disk shape having a diameter of 10 mm, the slurry is applied on the roughened surface and dried to form an active material layer having a thickness of 20 μm on the current collector Got. In addition, the density of the active material layer of the obtained positive electrode was 1.8 g / cm ³ .

(Production of test cell)
A disk-shaped negative electrode (diameter 16 mm) made of metallic lithium is prepared as the negative electrode, and this negative electrode, the positive electrode, a separator made of porous polyethylene, a mixed solvent of ethylene carbonate (EC) and dimethyl carbonate (DMC) (capacity ratio is EC: DMC = 1: 1) was used in a cell (trade name: HC flat cell) manufactured by Hosen Co., Ltd. using an electrolytic solution in which 1M LiPF ₆ was dissolved to prepare a test cell.

(Evaluation of high-rate discharge characteristics)
The test cell was allowed to stand for 8 hours in an atmosphere at 25 ° C., and then cycles 1 to 7 shown in Table 5 were sequentially performed in an atmosphere at 25 ° C. And the discharge capacity maintenance factor in 5C, 10C, and 15C was computed with the following formula | equation. The results are shown in Table 6. In addition, the discharge capacity of cycles 1, 5 to 7 used for calculating the discharge capacity retention rate was an average value of actually measured values obtained by three measurements during each cycle.
Discharge capacity retention rate at 5C (%) = discharge capacity at cycle 5 / discharge capacity at cycle 1 × 100
Discharge capacity retention rate at 10 C (%) = discharge capacity at cycle 6 / discharge capacity at cycle 1 × 100
Discharge capacity retention rate at 15 C (%) = discharge capacity at cycle 7 / discharge capacity at cycle 1 × 100

  As shown in Table 6, the discharge capacity retention rate in each of the Examples was significantly improved as compared with Comparative Example 1. This is presumably because, in the examples, the electron conductivity between the active material and the current collector was improved, and the current collection efficiency was improved.

Claims (12)

A method for producing a positive electrode current collector for a non-aqueous electrolyte secondary battery, wherein the surface of an aluminum current collector substrate is roughened with an etching agent,
An aqueous alkaline etching agent containing an alkali source and amphoteric metal ions, and an aqueous ferric ion etching agent containing a ferric ion source, a cupric ion source, a manganese ion source, and an inorganic acid. The manufacturing method of the positive electrode electrical power collector for nonaqueous electrolyte secondary batteries which is 1 or more types chosen from these.   The method for producing a positive electrode current collector for a non-aqueous electrolyte secondary battery according to claim 1, wherein the etching agent is the alkaline aqueous solution type etching agent.   The method for producing a positive electrode current collector for a non-aqueous electrolyte secondary battery according to claim 1, wherein the alkaline aqueous etching agent further contains a thio compound.   4. The method for producing a positive electrode current collector for a non-aqueous electrolyte secondary battery according to claim 3, wherein the content of the thio compound in the alkaline aqueous etching agent is 0.05 to 25.0 wt%.   The method for producing a positive electrode current collector for a non-aqueous electrolyte secondary battery according to claim 3 or 4, wherein the thio compound is at least one selected from a thiosulfate ion and a thio compound having 1 to 7 carbon atoms.   The method for producing a positive electrode current collector for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 5, wherein the alkaline aqueous etching agent further contains nitrate ions.   After roughening the surface of the aluminum current collector substrate with the alkaline aqueous etching agent, the surface is roughened with one or more aqueous solutions selected from an aqueous nitric acid solution, an aqueous sulfuric acid solution, and an aqueous solution containing sulfuric acid and hydrogen peroxide. The manufacturing method of the positive electrode electrical power collector for nonaqueous electrolyte secondary batteries of any one of Claims 1-6 which processes a chemical conversion surface.   After the surface of the aluminum current collector is roughened with the alkaline aqueous etching agent, hydrohalic acid and one or more metal hydroxides selected from alkali metals and alkaline earth metals are contained. The manufacturing method of the positive electrode electrical power collector for nonaqueous electrolyte secondary batteries of any one of Claims 1-6 which processes a roughening surface with 1 or more types of aqueous solution selected from alkaline aqueous solution.   The non-aqueous electrolyte 2 according to any one of claims 1 to 8, wherein an etching amount in a depth direction when the surface of the aluminum collector base material is roughened is 0.1 to 3.0 µm. A method for producing a positive electrode current collector for a secondary battery. A method for producing a positive electrode for a non-aqueous electrolyte secondary battery, wherein an active material layer is formed on an aluminum positive electrode current collector,
The positive electrode current collector made of aluminum is a positive electrode current collector obtained by the production method according to any one of claims 1 to 9,
The manufacturing method of the positive electrode for nonaqueous electrolyte secondary batteries which forms the said active material layer on the roughened surface of the said positive electrode electrical power collector.   The manufacturing method of the positive electrode for nonaqueous electrolyte secondary batteries of Claim 10 in which the said active material layer contains a lithium containing transition metal compound.   The method for producing a positive electrode for a non-aqueous electrolyte secondary battery according to claim 11, wherein the lithium-containing transition metal compound is lithium iron phosphate.