JP2009266492A - Power collector, its manufacturing method, negative electrode body, its manufacturing method, and lithium ion secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide: a power collector allowing strength to be improved by increasing a surface area; its manufacturing method; a negative electrode body having the power collector; its manufacturing method; and a lithium ion secondary battery equipped with the negative electrode body. <P>SOLUTION: This power collector is provided with a copper layer having, on a surface thereof, a plurality of recessed parts each having a depth of 4-8 μm and having needle-like copper having a length of 0.5-2 μm projected all over the surface thereof. In this negative electrode body, a tin thin film is formed on the power collector. This lithium ion secondary battery is equipped with the negative electrode body. In this manufacturing method of a power collector, the plurality of recessed parts each having a depth of 4-8 μm are formed on the surface of the copper layer, and needle-like copper having a length of 0.5-2 μm is projected on the surface of the copper layer having the recessed parts by electrodeless plating. In this manufacturing method of the negative electrode body, the recessed parts having a depth of 4-8 μm are formed on the surface of the copper layer, the needle-like copper having a length of 0.5-2 μm is projected on the surface of the copper layer having the recessed parts by electrodeless plating, and a tin-plated layer is formed on the surface of the copper layer having the needle-like copper. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a current collector and a manufacturing method thereof, a negative electrode body and a manufacturing method thereof, and a lithium ion secondary battery.

  A lithium ion secondary battery has a higher energy density than other secondary batteries and can be operated at a high voltage. For this reason, it is used as a secondary battery that can be easily reduced in size and weight in information equipment such as a mobile phone, and in recent years, there is an increasing demand for large-sized power such as for hybrid vehicles.

  The lithium ion secondary battery includes a positive electrode layer and a negative electrode layer, and an electrolyte filled therebetween, and the electrolyte is composed of a non-aqueous liquid or the like. The manufactured lithium ion secondary battery is discharged after being charged, and is regenerated by charging after discharging. When charging a lithium ion secondary battery, lithium ions are extracted from the positive electrode active material contained in the positive electrode layer, and the extracted lithium ions move to the negative electrode layer through the electrolyte and are absorbed into the negative electrode layer. Is done. On the other hand, during discharge of the lithium ion secondary battery, lithium ions are released from the negative electrode active material contained in the negative electrode layer, and the released lithium ions move to the positive electrode layer through the electrolyte and enter the positive electrode layer. . Thus, at the time of charge / discharge of the lithium ion secondary battery, lithium ions move between the positive electrode active material and the negative electrode active material.

  In the lithium ion secondary battery, electric energy is taken out when lithium ions move from the negative electrode active material to the positive electrode active material. Therefore, in order to improve the performance of the lithium ion secondary battery, it is important to use a negative electrode layer in a form in which lithium ions easily enter and exit, and in order to obtain such a form, the area of the interface between the negative electrode layer and the electrolyte is important. It is effective to increase. If the surface area of the negative electrode layer can be increased, the interface between the negative electrode layer and the electrolytic solution is easily formed, and the area of the interface can be increased. Therefore, in order to improve the performance of the lithium ion secondary battery, it is considered effective to use a negative electrode layer having an increased surface area (hereinafter sometimes referred to as “negative electrode body”).

Several technologies that have been disclosed so far have been disclosed for the purpose of improving the performance of a lithium ion secondary battery and for applying a lithium ion secondary battery with improved performance. . For example, in Patent Document 1, an inert gas is previously blown into an electroless copper plating solution containing copper ions, a complexing agent, a hypophosphite compound, a reduction reaction initiation metal catalyst, and an acetylene-containing polyoxyethylene surfactant. After that, an electroless plating method characterized by depositing a metal film on an object to be plated is disclosed. In Patent Document 2, before forming each active material on the current collector surface of at least one of the negative electrode and the positive electrode, an oxide layer made of a whisker-like oxide is formed on the current collector surface, and then the oxidation is performed. A method for producing a lithium secondary battery comprising a treatment for reducing a layer is disclosed. Further, Patent Document 3 discloses a surface-treated copper foil in which copper needles are formed on the surface from the surface of the foil body so as to protrude from the surface at an average density of 5 to 900 / μm ² , and the surface treatment. A battery electrode using a copper foil as a current collector is disclosed. Patent Document 4 discloses that lithium and an alloy can be formed on a current collector having a three-dimensional structure composed of one type selected from the group consisting of a foam metal and a fibrous metal sintered body. A nonaqueous electrolyte secondary battery using a negative electrode in which a thin film is formed by depositing a material containing various elements has been disclosed. Patent Document 5 discloses a current collector for a negative electrode of a lithium secondary battery having a current collector with a granular copper electrodeposition layer.

JP-A-4-116176 Japanese Patent Laid-Open No. 11-307102 JP 11-167922 A JP 2004-71305 A JP 2006-190514 A

  By the technique currently disclosed by patent document 1-patent document 5, it is thought that it becomes possible to form the negative electrode layer which increased the surface area using electroless copper plating. However, there has been a problem that the surface area increasing effect by these techniques is insufficient. In addition, since the needle-like body (acicular copper) formed by these techniques has insufficient strength, it is easy to break when used in contact with other members such as a separator, and the needle-like body breaks. There was also a problem that the effect of increasing the surface area was lost.

  Therefore, the present invention is capable of increasing the surface area and ensuring the strength, a current collector and a method for producing the current collector, a negative electrode body in which a tin layer is formed on the surface of the current collector, and It is an object of the present invention to provide a manufacturing method and a lithium ion secondary battery including the negative electrode body.

In order to solve the above problems, the present invention takes the following means. That is,
The first aspect of the present invention includes a copper layer having a plurality of recesses having a depth of 4 μm or more and 8 μm or less on the surface, and needle-like copper having a length of 0.5 μm or more and 2 μm or less protruding from the entire surface. It is a current collector.

  In the present invention, the form of the “copper layer” is not particularly limited, but for example, a form constituted by a copper foil or a form constituted by a copper plating layer formed on the surface of the substrate. it can. Further, “entire surface” means the entire surface of the copper foil including the surface of the recess.

  A second aspect of the present invention is a negative electrode body comprising the current collector according to the first aspect of the present invention and a tin thin film formed on the surface of the current collector.

  In the second aspect of the present invention, the negative electrode body is preferably bent in a bellows shape.

  A third aspect of the present invention is a lithium ion secondary battery comprising the negative electrode body according to the second aspect of the present invention.

  According to a fourth aspect of the present invention, a roughening step of forming a plurality of recesses having a depth of 4 μm or more and 8 μm or less on the surface of the copper layer by etching and a liquid containing at least hypophosphorous acid as a reducing agent are used. An electroless plating step of projecting needle-shaped copper having a length of 0.5 μm or more and 2 μm or less by electroless plating on the surface of the copper layer that has undergone the forming step. is there.

  According to a fifth aspect of the present invention, a roughening step of forming a recess having a depth of 4 μm or more and 8 μm or less on the surface of the copper layer by etching and a liquid containing at least hypophosphorous acid as a reducing agent are performed. An electroless plating process in which needle-shaped copper having a length of 0.5 μm or more and 2 μm or less is projected by electroless plating on the surface of the copper layer that has undergone the process, and a tin plating layer on the surface of the copper layer that has undergone the electroless plating process And a tin plating process to be formed.

  In the fifth aspect of the present invention, the copper layer is a copper plating layer formed on the surface of the base material, and after the tin plating step, a base material removal step for removing the base material is provided. Prior to the step, a bellows step of bending the base material into a bellows shape is preferably provided.

  Here, “the bellows step of bending the base material into a bellows shape” means that when the bellows step is provided before the tin plating step, the step of bending the base material on which the copper plating layer is not formed, or copper It means that the step of bending the base material on which the plating layer is formed into a bellows shape is a bellows step. Moreover, when a bellows process is provided after a tin plating process, the process of bending the base material in which the tin plating layer was formed in the surface of a copper layer to a bellows form means that it is a bellows process.

  In the fifth aspect of the present invention, a reduction firing step of firing the copper tin plating electrode in a reducing atmosphere may be further provided after the tin plating step.

  Further, in the fifth aspect of the present invention provided with the base material removal step and the bellows step, a reduction firing step of firing the copper tin plating electrode in a reducing atmosphere between the tin plating step and the base material removal step is further provided. It may be provided.

  In the first aspect of the present invention, acicular copper having a length of 0.5 μm or more and 2 μm or less protrudes from the entire surface of the copper layer including the surfaces of a plurality of recesses having a depth of 4 μm or more and 8 μm or less. By controlling the depth of the recess and the length of the acicular copper, a current collector including a copper layer with an increased surface area can be provided. Furthermore, by controlling the length of the acicular copper to 0.5 μm or more and 2 μm or less, a current collector that can ensure the strength that the acicular copper is difficult to break even when it contacts other members. Can be provided. Therefore, according to the first aspect of the present invention, it is possible to provide a current collector capable of increasing the surface area and ensuring the strength.

  In the negative electrode body according to the second aspect of the present invention, a tin thin film is formed on the surface of the current collector that can increase the surface area and ensure the strength. By increasing the surface area of the tin thin film that functions as the negative electrode active material, the capacity of the negative electrode body can be increased. Further, by increasing the surface area, it is possible to provide a negative electrode body having a predetermined amount of tin thin film while reducing the thickness of the tin thin film. By reducing the thickness of the tin thin film, ions can enter and exit The amount of expansion / contraction associated with can be suppressed. Further, by forming the tin thin film on the surface of the acicular copper, a gap can be interposed between the adjacent acicular copper, so that the sliding of tin due to the expansion / contraction of the tin thin film can be suppressed. Since the durability of the negative electrode body can be improved by suppressing the expansion / contraction of the tin thin film and the sliding of the tin, the capacity and durability can be improved according to the second aspect of the present invention. The negative electrode body which can be provided can be provided.

  In the second aspect of the present invention, a negative electrode body that can increase the capacity per unit volume can be provided by bending the negative electrode body into a bellows shape.

  The lithium ion secondary battery according to the third aspect of the present invention includes the negative electrode body according to the second aspect of the present invention. Therefore, according to the third aspect of the present invention, it is possible to provide a lithium ion secondary battery capable of improving capacity and durability.

  According to a fourth aspect of the present invention, there is provided a current collector in which needle-like copper is projected on the entire surface of a copper layer including the surfaces of a plurality of recesses formed in a roughening step in an electroless plating step. Such a current collector can increase the surface area and ensure strength. Therefore, according to the fourth aspect of the present invention, it is possible to provide a method of manufacturing a current collector that can increase the surface area and can manufacture a current collector that can ensure strength. it can.

  In the fifth aspect of the present invention, the negative electrode body is manufactured through a step of forming a tin thin film on the surface of the current collector capable of increasing the surface area and ensuring the strength. The negative electrode body manufactured in this way can improve capacity and durability. Therefore, according to the fifth aspect of the present invention, it is possible to provide a method for producing a negative electrode body that can produce a negative electrode body capable of improving capacity and durability.

  In addition, in the fifth aspect of the present invention, a negative electrode body manufacturing method capable of manufacturing a negative electrode body capable of increasing the capacity per unit volume by providing a bellows process can be provided.

  Further, in the fifth aspect of the present invention, an alloy layer containing copper and tin can be formed at the interface between the copper layer and the tin plating layer by providing a reduction firing step after the tin plating step. By forming the alloy layer, durability can be improved. Therefore, the manufacturing method of the negative electrode body which can manufacture the negative electrode body which can improve durability can be provided by setting it as the form provided with a reduction | restoration baking process.

  The present invention will be described below with reference to the drawings. In addition, the form shown below is an illustration of this invention and this invention is not limited to the form shown below.

1. Current collector and manufacturing method thereof 1.1. Current Collector FIG. 1 is a conceptual diagram showing an example of a current collector 10 according to the present invention. In FIG. 1, a part of the current collector 10 of the present invention is shown enlarged. Hereinafter, the current collector 10 of the present invention will be described with reference to FIG.

  As shown in FIG. 1, the current collector 10 of the present invention is made of a copper foil (hereinafter sometimes referred to as “copper foil 10”), and has a plurality of recesses 1, 1,. Further, needle-shaped copper 2, 2,... Protrudes from the entire surface of the copper foil 10 including the surfaces of the recesses 1, 1,. The surface area is increased by forming a plurality of recesses 1, 1,... On the surface and projecting the acicular coppers 2, 2,... Over the entire surface of the copper foil 10 including the surfaces of the recesses 1, 1,. Can be increased. Further, the strength can be ensured by controlling the lengths of the acicular coppers 2, 2,. Therefore, according to the present invention, it is possible to provide the current collector 10 capable of increasing the surface area and ensuring the strength.

  In the current collector 10, the depth of the recesses 1, 1,... Is 4 μm or more from the viewpoint of easily obtaining an effect of increasing the surface area. In addition, the depth of the recesses 1, 1,. In the current collector 10, the depth of the recesses 1, 1,... Is preferably 5 μm or more and 7 μm or less. Further, in the current collector 10, the length of the needle-shaped coppers 2, 2,... Further, from the viewpoint of forming needle-shaped coppers 2, 2,... That are not easily broken even when they are in contact with other members, the length of the needle-shaped coppers 2, 2,. In the current collector 10, the lengths of the acicular coppers 2, 2,... Are preferably 1 μm or more and 2 μm or less.

  In the said description regarding the electrical power collector of this invention, although the electrical power collector 10 which consists of copper foil was illustrated, the electrical power collector of this invention is not limited to the said form. The current collector of the present invention may have a copper layer in which needle-like copper having a length of 0.5 μm or more and 2 μm or less is formed on the entire surface including a plurality of recesses having a depth of 4 μm or more and 8 μm or less. Other forms such as a current collector configured by coating the surface of the copper foil 10 with a conductive material are also possible.

1.2. 2. Current Collector Manufacturing Method FIG. 2 is a flowchart showing an example of steps provided in the current collector manufacturing method of the present invention. Moreover, FIG. 3 is a conceptual diagram which shows the example of the process with which the manufacturing method of the electrical power collector of this invention is equipped. 3, components having the same configuration as in FIG. 1 are denoted by the same reference numerals as those used in FIG. 1, and description thereof is omitted as appropriate. Hereinafter, the manufacturing method of the current collector of the present invention will be described with reference to FIGS.

  As shown in FIG.2 and FIG.3, the manufacturing method of the electrical power collector of this invention is equipped with the roughening process (process S11) and the electroless-plating process (process S12), and passes through process S11 and process S12. Thus, the current collector 10 of the present invention is manufactured.

<Step S11>
Step S11 is a step of forming a plurality of recesses 1, 1,... Having a depth of 4 μm or more and 8 μm or less on the surface of the copper foil by etching the copper foil having a predetermined surface roughness (unevenness). . The depth of the recesses 1, 1,... Is 4 μm or more in order to produce a current collector capable of sufficiently increasing the surface area, and the depth of the recesses 1, 1,. The reason for this is to make it difficult to break even when it comes into contact with other members, and to allow needle-shaped copper to protrude uniformly in the next step.

<Step S12>
In step S12, needle-shaped copper having a length of 0.5 μm or more and 2 μm or less is projected by electroless plating on the surface of the copper foil that has undergone the above-described step S11 using a liquid containing at least hypophosphorous acid as a reducing agent. It is a process. The length of the acicular copper plating can be controlled by adjusting the plating time.

  The current collector 10 manufactured through the steps S11 and S12 has a plurality of recesses 1, 1,... Having a depth of 4 μm or more and 8 μm or less, and the entire surface has a length of 0.5 μm or more and 2 μm or less. Are projected. By adopting such a configuration, the surface area can be increased, and the strength of the needle-shaped copper is controlled to be 0.5 μm or more and 2 μm or less to ensure the strength that does not break even when it comes into contact with other members. can do. Therefore, according to this invention, the manufacturing method of the electrical power collector which can manufacture the electrical power collector 10 which can increase a surface area and can ensure intensity | strength can be provided. .

  In the manufacturing method of the current collector of the present invention, the interval between the recesses (or the interval between the projections) provided on the surface of the copper foil etched in step S11 is not particularly limited. From the viewpoint of suppressing contact of acicular copper formed on the surface or the like, the interval is preferably set to 3 μm or more. On the other hand, from the viewpoint of easily obtaining the effect of increasing the surface area, the interval is preferably set to 10 μm or less. A more preferable interval is 5 μm or more and 8 μm or less. Furthermore, the width of the convex part (sometimes referred to as “convex part 3, 3,...”) Sandwiched between adjacent concave parts 1, 1,... Is not particularly limited, but is in contact with other members. Even if it is a case, it is preferable that the width | variety of the convex part 3, 3, ... shall be 1 micrometer or more from a viewpoint of setting it as the form in which the acicular copper formed by process S12 does not break easily. On the other hand, it is preferable that the width of the convex portions 3, 3,. More preferably, the width of the convex portions 3, 3,... Is 1.5 μm or more and 4 μm or less.

  In the method for producing a current collector of the present invention, the form of the copper foil used in step S11 and the method of providing irregularities on the surface of the copper foil are not particularly limited. As the copper foil used in step S11, a metal material typified by electrolytic copper foil, rolled copper foil, or the like can be used. Furthermore, as a method of providing irregularities on the surface of the copper foil, in addition to a chemical roughening method typified by etching or the like, a physical roughening method typified by sandblasting, buffing, brush polishing or the like is exemplified. be able to.

2. Negative electrode body and manufacturing method thereof 2.1. 4. Negative electrode body FIG. 4: is a conceptual diagram which shows the example of the form of the negative electrode body 20 of this invention concerning 1st Embodiment. FIG. 4 shows an enlarged part of the negative electrode body 20 of the present invention. 4, components having the same configuration as in FIG. 1 are denoted by the same reference numerals as those used in FIG. 1, and description thereof is omitted as appropriate. Hereinafter, the negative electrode body 20 of the present invention according to the first embodiment will be described with reference to FIG.

  As shown in FIG. 4, the negative electrode body 20 of the present invention according to the first embodiment includes a current collector 10 and a tin thin film 11 formed on the surface of the current collector 10. Since tin can take in and out ions (for example, lithium ions, etc.), the negative electrode body 20 of the present invention can be used, for example, in the negative electrode layer of a lithium ion secondary battery.

  In the negative electrode body 20 of the present invention, the tin thin film 11 is formed on the surface of the current collector 10 whose surface area is increased by the recesses 1, 1,. Therefore, since the surface area of the tin thin film can be increased as compared with the conventional negative electrode body using tin as the negative electrode active material, the negative electrode body 20 capable of increasing the capacity according to the present invention. Can be provided. Moreover, when the same mass tin film is formed on the conventional negative electrode body having a surface area insufficient as compared with the present invention and the negative electrode body 20 of the present invention, the negative electrode body 20 of the present invention For example, the thickness of the tin thin film 11 can be made thinner than the tin thin film formed on the conventional negative electrode body. When the thickness of the tin thin film 11 is thus reduced, the amount of expansion / contraction associated with the entry / exit of ions can be suppressed. When the amount of expansion / contraction is suppressed, durability when charging / discharging is repeated can be improved. Therefore, according to the present invention, the negative electrode body 20 capable of improving durability is provided. be able to. Further, by forming the tin thin film 11 also on the surfaces of the acicular coppers 2, 2,..., Gaps can be interposed between the adjacent acicular coppers 2, 2,. Tin sliding due to expansion / contraction can be suppressed. When tin sliding is suppressed, the amount of tin that functions as a negative electrode active material can be maintained and durability can be improved. Therefore, according to the present invention, the negative electrode can improve durability. A body 20 can be provided. As mentioned above, according to this invention, the negative electrode body 20 which can increase a capacity | capacitance and can improve durability can be provided.

  FIG. 5 is a conceptual diagram showing a form example of the negative electrode body 21 of the present invention according to the second embodiment. FIG. 5 shows an enlarged part of the negative electrode body 21 of the present invention. 5, components having the same configuration as in FIG. 4 are denoted by the same reference numerals as those used in FIG. 4, and description thereof is omitted as appropriate. Hereinafter, the negative electrode body 21 of the present invention according to the second embodiment will be described with reference to FIG.

  As shown in FIG. 5, the negative electrode body 21 of the present invention has a shape in which the negative electrode body 20 is bent into a bellows shape. By setting it as this form, the negative electrode body 21 which can increase the capacity | capacitance per unit volume can be provided. Here, since the negative electrode body 21 of the present invention is formed by bending the negative electrode body 20 into a bellows shape, the surface has irregularities. When a negative electrode body having a smooth surface is bent, it becomes difficult to distribute an electrolyte (for example, an electrolyte solution composed of a non-aqueous liquid, etc., the same applies hereinafter) over the entire surface of the negative electrode body. Since the entire surface of the negative electrode body 21 is an uneven surface, the electrolyte can be spread over the entire surface even in a state of being bent into a bellows shape.

  In the negative electrode bodies 20 and 21 of the present invention, the thickness of the tin thin film 11 formed on the surface of the current collector 10 is not particularly limited. From the standpoint of providing the negative electrode bodies 20 and 21 capable of improving the durability by suppressing the amount of expansion / contraction associated with charging / discharging, it is preferable to reduce the thickness of the tin thin film 11. On the other hand, it is preferable to increase the thickness of the tin thin film 11 from the viewpoint of providing the negative electrode bodies 20 and 21 in a form that easily increases the capacity. The thickness of the tin thin film 11 can be appropriately determined in consideration of the balance between durability and capacity. In the negative electrode bodies 20 and 21 of the present invention, the thickness of the tin thin film 11 is preferably set to 0.1 μm, for example.

  In the said description regarding the negative electrode body 20 and 21 of this invention, although the form in which the tin thin film 11 was directly formed in the surface of the electrical power collector 10 (copper foil 10) was illustrated, this invention is limited to the said form. It is not a thing. In the present invention, a copper plating layer is preferably provided between the copper foil 10 and the tin thin film 11 from the viewpoint of easily improving the electronic conductivity of the negative electrode body. In the case where a copper plating layer is provided between the copper foil 10 and the tin thin film 11, the thickness of the copper plating layer is set to 1 μm or more from the viewpoint of suppressing the formation of pinholes during the preparation of the copper plating layer. It is preferable.

  Further, in the negative electrode body of the present invention, from the viewpoint of suppressing the formation of an alloy layer containing copper and tin resulting from direct plating of tin on the surface of copper, the copper foil 10 and the tin thin film 11 are used. Between the two, a nickel plating layer is preferably provided. In the case where a nickel plating layer is provided between the copper foil 10 and the tin thin film 11, the thickness of the nickel plating layer is set to 1 μm or more from the viewpoint of suppressing the formation of pinholes during the production of the nickel plating layer. It is preferable.

  In addition, in the negative electrode body of the present invention, by directly forming tin on the surface of copper and positively forming an alloy layer containing copper and tin, a negative electrode body that can improve durability, etc. From the viewpoint, it is preferable that the nickel plating layer is not provided. When the alloy layer containing copper and tin is positively formed between the copper foil and the tin thin film, the negative electrode bodies 20 and 21 are sintered in a reducing atmosphere after the tin thin film 11 is formed. Is preferred.

2.2. Method for Manufacturing Negative Electrode Body FIG. 6 is a flowchart showing an example of steps provided in the method for manufacturing the negative electrode body of the present invention according to the first embodiment. Moreover, FIG. 7 is a conceptual diagram showing an example of a process provided in the method for manufacturing a negative electrode body of the present invention according to the first embodiment. 7, components having the same configuration as in FIG. 4 are denoted by the same reference numerals as those used in FIG. 4, and description thereof is omitted as appropriate. Hereinafter, the manufacturing method of the negative electrode body according to the first embodiment of the present invention will be described with reference to FIGS. 4, 6, and 7.

  As shown in FIG.6 and FIG.7, the manufacturing method of the negative electrode body of this invention concerning 1st Embodiment is a copper plating process (process S21), a roughening process (process S22), and an electroless-plating process ( Step S23), a tin plating step (Step S24), and a base material removal step (Step S25) are provided. That is, in the manufacturing method of the negative electrode body of the present invention according to the first embodiment, the negative electrode body 20 is manufactured through steps S21 to S25.

<Step S21>
Step S21 is a step of forming a copper plating layer 10a on the surface of the substrate 30 by forming a copper plating film on the surface of the substrate 30 made of a resin film. The method for forming the copper plating layer 10a is not particularly limited, and a known method can be used. In addition, the thickness of the copper plating layer 10a formed in step S21 is not particularly limited as long as it is thicker than the depth of the recess formed in step S22 described later. However, from the viewpoint of forming a negative electrode body in a form in which the capacity is easily increased, it is preferable to make it as thin as possible within the range in which the concave portion can be formed.

<Step S22>
In step S22, by etching the copper plating layer 10a formed in step S21, a plurality of recesses 1, 1,... Having a depth of 4 μm or more and 8 μm or less are formed on the surface of the copper plating layer 10a. This is a step of producing the copper plating layer 10b. The depth of the recesses 1, 1,... Is 4 μm or more in order to manufacture a negative electrode body capable of sufficiently increasing the surface area, and the depth of the recesses 1, 1,. To make it difficult to break even when it comes into contact with other members, to make needle-shaped copper uniformly protrude in the electroless plating process, and to form a tin plating layer uniformly in the subsequent tin plating process It is.

<Step S23>
Step S23 uses a liquid containing at least hypophosphorous acid as a reducing agent, and the entire surface of the copper plating layer 10b prepared in Step S22 is needle-shaped having a length of 0.5 μm to 2 μm by electroless plating. This is a step of producing a copper plating layer 10c from which copper 2, 2,. The length of the needle-shaped copper 2, 2,... Is 0.5 μm or more in order to produce a negative electrode body capable of sufficiently increasing the surface area. The length is set to 2 μm or less in order to obtain acicular copper 2, 2,... Having a strength that does not break even if a tin plating layer is formed in the tin plating step. The length of the acicular copper 2, 2,... Can be controlled by adjusting the plating time.

<Step S24>
In step S24, a tin plating film is formed on the surface of the copper plating layer 10c prepared in step S23, thereby producing a copper tin plating electrode 10d in which the tin thin film 11 is formed on the surface of the copper plating layer 10c. It is a process. The thickness of the tin thin film 11 formed in step S24 is not particularly limited, but it is possible to manufacture a negative electrode body capable of suppressing the amount of expansion / contraction associated with charge / discharge and improving the durability. From the viewpoint of, for example, it is preferable to reduce the thickness of the tin thin film 11. On the other hand, it is preferable to increase the thickness of the tin thin film 11 from the viewpoint of making it possible to manufacture a negative electrode body in a form that easily increases the capacity. The thickness of the tin thin film 11 can be appropriately determined in consideration of the balance between durability and capacity. The thickness of the tin thin film 11 formed in step S24 is preferably 0.1 μm or more, for example.

<Step S25>
Step S25 is a step of manufacturing the negative electrode body 20 by removing the base material 30 after the step S24. Step S25 is not particularly limited as long as the negative electrode body 20 capable of increasing the surface area and capable of securing the strength can be manufactured. be able to.

  The negative electrode body 20 manufactured through the steps S21 to S25 has a plurality of recesses 1, 1,... Having a depth of 4 μm or more and 8 μm or less, and the entire surface has a length of 0.5 μm or more and 2 μm or less. Are projected, and a tin thin film 11 is formed on the entire surface of the copper plating layer including the surfaces of the needle-shaped coppers 2, 2,. Therefore, since the surface area of the tin thin film 11 can be increased as compared with the conventional negative electrode body using tin as the negative electrode active material, the negative electrode body capable of increasing the capacity according to the present invention. The manufacturing method of the negative electrode body which can manufacture 20 can be provided. Moreover, when the same mass tin film is formed on the conventional negative electrode body manufactured by the conventional manufacturing method and the negative electrode body 20 manufactured through steps S21 to S25, For example, the thickness of the tin thin film 11 can be made thinner than the tin thin film formed on the conventional negative electrode body. When the thickness of the tin thin film 11 is thus reduced, the amount of expansion / contraction associated with the entry / exit of ions can be suppressed. When the amount of expansion / contraction is suppressed, durability when charging / discharging is repeated can be improved. Therefore, according to the present invention, the negative electrode body 20 capable of improving durability can be manufactured. The manufacturing method of a negative electrode body can be provided. Further, by forming the tin thin film 11 also on the surfaces of the acicular coppers 2, 2,..., Gaps can be interposed between the adjacent acicular coppers 2, 2,. Tin sliding due to expansion / contraction can be suppressed. If tin sliding is suppressed, the amount of tin that functions as a negative electrode active material can be maintained and durability can be improved. Therefore, according to the present invention, the negative electrode body that can improve durability The manufacturing method of the negative electrode body which can manufacture 20 can be provided. As mentioned above, according to this invention, the manufacturing method of the negative electrode body which can manufacture the negative electrode body 20 which can increase a capacity | capacitance and can improve durability can be provided.

  In the method for producing a negative electrode body of the present invention, the interval between the recesses 1, 1,... Formed by etching in step S22 is not particularly limited, but needles formed on the surface of the recesses in step S23. From the standpoint of suppressing copper contact, the distance is preferably 3 μm or more. On the other hand, from the viewpoint of easily obtaining the effect of increasing the surface area, the interval is preferably set to 10 μm or less. A more preferable interval is 5 μm or more and 8 μm or less. Furthermore, although the width | variety of the some convex part 3, 3, ... pinched | interposed into the some recessed part 1, 1, ... formed by process S22 is not specifically limited, When it contacts with another member, However, from the standpoint of making the needle-shaped copper formed in step S23 difficult to break, it is preferable that the width of the convex portions 3, 3,. On the other hand, it is preferable that the width of the convex portions 3, 3,. More preferably, the width of the convex portions 3, 3,... Is 1.5 μm or more and 4 μm or less.

  FIG. 8 is a flowchart showing an example of steps provided in the method for manufacturing a negative electrode body according to the second embodiment of the present invention. Moreover, FIG. 9 is a conceptual diagram which shows the form example of the bellows process and base-material removal process with which the manufacturing method of the negative electrode body of this invention concerning 2nd Embodiment is equipped. 9, those having the same configuration as in FIG. 7 are denoted by the same reference numerals as those used in FIG. 7, and description thereof will be omitted as appropriate. Hereinafter, the manufacturing method of the negative electrode body of the present invention according to the second embodiment will be described with reference to FIGS.

  As shown in FIG. 8, the manufacturing method of the negative electrode body of the present invention according to the second embodiment includes a copper plating step (step S31), a roughening step (step S32), and an electroless plating step (step S33). And a tin plating step (step S34), a reduction firing step (step S35), a bellows step (step S36), and a base material removal step (step S37). That is, in the manufacturing method of the negative electrode body of the present invention according to the second embodiment, the negative electrode body 21 is manufactured through steps S31 to S37. Here, steps S31 to S34 are the same steps as steps S21 to S24 described above. Therefore, in the description regarding the manufacturing method of the negative electrode body of the present invention according to the second embodiment, description regarding these steps is omitted, and Steps S35 to S37 will be described.

<Step S35>
In step S35, the copper tin plating electrode 10d produced in step S34 which takes the same form as step S24 is baked in a reducing atmosphere, so that a copper tin alloy layer is formed at the interface between the copper plating layer 10c and the tin thin film 11. This is a step of producing the copper tin plating electrode 10e formed with the. By firing in a reducing atmosphere, the formation of an oxide film on the surface of the copper tin plating electrode 10e can be suppressed, and the copper tin plating electrode 10e capable of improving the entrance and exit of ions and electrons is produced. Can do. The reducing atmosphere in step S35 is not particularly limited as long as it is an atmosphere that can prevent / suppress the formation of an oxide film on the surface of the copper tin plating electrode 10e, and may be, for example, a mixed atmosphere of argon and hydrogen. it can. Further, the firing temperature in step S35 can form a copper-tin alloy layer by diffusing copper and tin at the interface between the copper plating layer and the tin thin film 11, and is equivalent to the copper-tin plating electrode 10d (preferably substantially omitted). If it is the temperature which can produce the copper tin plating electrode 10e which has the external shape of the same), it will not specifically limit. The firing temperature in step S35 can be, for example, about 200 ° C. The firing time in step S35 can form a copper-tin alloy layer by diffusing copper and tin at the interface between the copper plating layer and the tin thin film 11, and has the same outer shape as the copper-tin plating electrode 10d. The time is not particularly limited as long as the copper tin plating electrode 10e can be produced. The firing time in step S35 can be, for example, about 30 minutes to 600 minutes.

<Step S36>
Step S36 is a step of producing the copper tin plating electrode 10f bent in a bellows shape by bending the copper tin plating electrode 10e produced in the step S35 into a bellows shape (see FIG. 9). In addition, in FIG. 9, although the copper tin plating electrode 10f bent in the three layers was illustrated, process S36 is not limited to the said form.

<Step S37>
Step S37 is a step of manufacturing the negative electrode body 21 bent into a bellows shape by removing the base material 30 after the step S36. Step S37 is not particularly limited as long as the negative electrode body 21 can be manufactured by removing the base material 30, and can be a known form.

  Since the copper tin alloy layer is formed between the copper plating layer 10c and the tin thin film 11, the negative electrode body 21 manufactured through the steps S31 to S37 suppresses the performance degradation associated with charge / discharge. (Improves durability). Moreover, since the negative electrode body 21 is bent in a bellows shape, the capacity per unit volume can be increased. That is, according to the present invention, a method for producing a negative electrode body that can produce a negative electrode body 21 that can ensure strength, improve durability, and increase the capacity per unit volume. Can be provided.

  In the above description regarding the method for producing a negative electrode body of the present invention, the embodiment in which the reduction firing step is provided when the bellows step is provided is illustrated. However, the method for producing the negative electrode body of the present invention is limited to the embodiment. It is not a thing. Even if the manufacturing method of the negative electrode body of the present invention is not provided with a bellows process, it is possible to adopt a form in which a reduction firing process is provided. In this case, a reduction firing process may be provided between the tin plating process and the substrate removal process.

  Moreover, in the said description regarding the manufacturing method of the negative electrode body of this invention, although the form provided with a copper plating process was illustrated, the manufacturing method of the negative electrode body of this invention is not limited to the said form. The copper layer on which the recesses and needle-like copper are formed may be manufactured by a method other than copper plating.

  Moreover, in the said description regarding the manufacturing method of the negative electrode body of this invention concerning 2nd Embodiment, although the form provided with a reduction baking process and a bellows process was illustrated, the manufacturing method of the negative electrode body of this invention is reduction baking. It is also possible to adopt a form in which no process or bellows process is provided.

  Moreover, although the said description regarding the manufacturing method of the negative electrode body of this invention concerning 2nd Embodiment illustrated the form provided with a bellows process between a tin plating process and a base material removal process, the negative electrode of this invention The manufacturing method of a body is not limited to the said form. When the bellows process is provided, the bellows process may be provided before the base material removal process. For example, the bellows process may be provided as a preprocess of the copper plating process or a preprocess of the tin plating process. Is also possible. However, from the viewpoint of making it possible to form a copper plating layer having a uniform thickness on the surface of the substrate, it is preferable that a bellows process be provided after the copper plating process. Moreover, it is preferable that a bellows process is provided after a tin plating process from a viewpoint of making it possible to form the tin plating layer of uniform thickness on the whole surface of the copper plating layer in which the acicular copper was formed.

  In addition, in the method for producing a negative electrode body according to the present invention, from the standpoint that the surface area of the produced negative electrode body can be further increased, a group having a plurality of holes by forming holes in advance, etc. The material is preferably subjected to a copper plating process or the like. As another form which increases the surface area of the negative electrode body manufactured further, the form etc. which form a pinhole by a copper plating process can be illustrated.

3. Lithium ion secondary battery and manufacturing method thereof 3.1. Lithium Ion Secondary Battery FIG. 10 is a conceptual diagram showing a form example of the lithium ion secondary battery of the present invention, and shows an enlarged partial cross section of the lithium ion secondary battery. 10, components having the same configuration as in FIG. 9 are denoted by the same reference numerals as those used in FIG. 9, and description thereof is omitted as appropriate. In addition, in order to facilitate understanding of the present invention, in FIG. 10, the description of the recesses, acicular copper, and tin thin film provided in the negative electrode body is omitted. Hereinafter, the lithium ion secondary battery of the present invention will be described with reference to FIGS. 9 and 10.

  The lithium ion secondary battery 100 of the present invention shown in FIG. 10 includes a current collector 40, a positive electrode layer 50 disposed so as to be in contact with the current collector 40, a negative electrode body 21, and a positive electrode layer 50 and a negative electrode. A separator 60 is provided between the electrode body 21 and a non-aqueous electrolyte solution 70 is filled between the positive electrode layer 50 and the negative electrode body 21. Irregularities are formed on the surface of the negative electrode body 21 provided in the lithium ion secondary battery 100. Therefore, the electrolytic solution 70 can be spread over the entire surface of the negative electrode body 21 even when bent in a bellows shape. Thus, since the lithium ion secondary battery 100 is provided with the negative electrode body 21, according to the present invention, it is possible to ensure strength, improve durability, and capacity per unit volume. The lithium ion secondary battery 100 can be provided.

  In the above description regarding the lithium ion secondary battery 100 of the present invention, the mode in which the negative electrode body 21 bent in a bellows shape is illustrated, but the lithium ion secondary battery of the present invention is not limited to this mode. Absent. The lithium ion secondary battery of the present invention may be configured to include the negative electrode body 20 of the present invention that is not bent into a bellows shape. However, since the capacity per unit volume can be increased by bending the negative electrode body into a bellows shape, from the viewpoint of making a lithium ion secondary battery capable of increasing the capacity per unit volume, etc. It is preferable that the negative electrode body of the present invention bent in a bellows shape is provided.

  The lithium ion secondary battery of the present invention is not particularly limited as long as the negative electrode body of the present invention is provided. A well-known thing can be used for a positive electrode layer.

3.2. Manufacturing Method of Lithium Ion Secondary Battery The manufacturing method of the lithium ion secondary battery of the present invention is such that the form of other steps is as long as the negative electrode body provided in the lithium ion secondary battery is manufactured by the method of the present invention. It is not particularly limited. Processes other than the process of manufacturing the negative electrode body can be in a known form.

  Hereinafter, the present invention will be described with reference to examples.

1) Production of current collector and surface observation For the purpose of removing the oxide film and the like on the surface of the copper foil and performing the roughening treatment in the next step uniformly, at a spray pressure of 0.1 MPa to 0.15 MPa, Pretreatment was performed by bringing NBP (30 ° C.) manufactured by EBARA ELECTRIC CO., LTD. Into contact with the surface of an electrolytic copper foil having a thickness of 18 μm for 30 seconds. Thereafter, NBDII (30 ° C.) manufactured by Ebara Densan Co., Ltd. is brought into contact with the surface of the electrolytic copper foil that has undergone the pretreatment for 90 seconds at a spray pressure of 0.1 MPa to 0.15 MPa. A roughening treatment (hereinafter sometimes referred to as a “roughening step”) for forming a plurality of recesses having a depth of 6 μm on the surface of the copper foil was performed. Thereafter, the surface of the electrolytic copper foil is subjected to an electroless copper plating treatment for 10 minutes using a treatment liquid (60 ° C.) having the following composition for the electrolytic copper foil whose surface has been cleaned. A plurality of needle-shaped copper having a size of 1 μm was projected to manufacture a current collector according to the example. The composition of the treatment solution used for the electroless copper plating treatment is copper sulfate; 15 g / L, nickel sulfate; 3 g / L, complexing agent (citric acid); 15 g / L, buffer (boric acid); 10 g / L. And a reducing agent (hypophosphorous acid); 20 g / L, and a surfactant (PEG 1000); 1 g / L, and the pH of the treatment solution was 8.5.

  On the other hand, the collector which concerns on a comparative example was manufactured by the process similar to the manufacturing method of the collector concerning the said Example except not performing a pre-processing and a roughening process.

2) Surface Observation of Current Collector A scanning electron microscope image (hereinafter referred to as “SEM image”) of the surface of the electrolytic copper foil after the completion of the roughening step for producing the current collector according to the example is shown in FIG. FIG. 12 shows SEM images of the surface of the current collector according to the example manufactured through the electroless copper plating process. Moreover, the SEM image of the collector surface concerning a comparative example is shown in FIG.

  From FIG. 12, in the current collector according to the example manufactured by the method for manufacturing a current collector of the present invention, a plurality of acicular copper was formed on the entire surface of the electrolytic copper foil, and the surface area was greatly increased. On the other hand, from FIG. 13, the current collector according to the comparative example manufactured by a method different from the method of manufacturing the current collector according to the present invention has an effect of increasing the surface area as compared with the current collector according to the example. Reduced. That is, according to the present invention, a current collector capable of increasing the surface area could be provided. As described above, according to the current collector of the present invention, the surface area can be increased, and the length of the acicular copper is controlled, so that the strength can be ensured.

3) Production of negative electrode body-1
The tin plating process which forms a tin plating layer over 120 minutes using the process liquid (70 degreeC) which shows a composition with respect to the electrical power collector concerning the said Example and the electrical power collector concerning the said comparative example below. To form a tin thin film having a thickness of 0.1 μm on the surface of acicular copper to produce a negative electrode body (hereinafter, a negative electrode having a tin thin film formed on the surface of the current collector according to the above example) The electrode body is referred to as “negative electrode body according to example”, and the negative electrode body in which a tin thin film is formed on the surface of the current collector according to the comparative example is referred to as “negative electrode body according to comparative example 1”). Here, the composition of the treatment solution used for the tin plating treatment was tin chloride; 60 g / L, potassium hydroxide; 300 g / L, complexing agent (potassium citrate); 250 g / L, surfactant (PEG 1000); It was 50 ppm. In addition to the negative electrode body according to the example and the negative electrode body according to comparative example 1, a tin thin film is formed on the surface of the electrolytic copper foil that has not been subjected to the roughening treatment or the like by using the above-described tin plating treatment liquid. Thus, a negative electrode body according to Comparative Example 2 was manufactured.

4) Surface observation of negative electrode body Using a laser microscope, the surface area of the negative electrode body according to the example, the surface area of the negative electrode body according to comparative example 1, and the surface area of the negative electrode body according to comparative example 2 were measured. . When the surface area of the negative electrode body according to Comparative Example 2 is 1, the surface area of the negative electrode body according to Example is about 10, while the surface area of the negative electrode body according to Comparative Example 1 is about 4. It was. Moreover, from FIG. 14 which shows the SEM image of the negative electrode body surface concerning an Example, the unevenness | corrugation on the surface of the negative electrode body concerning an Example was maintained even after the tin thin film was formed. That is, according to the present invention, it was possible to produce a negative electrode body with an increased surface area compared to the conventional art. As described above, according to the negative electrode body of the present invention, the capacity can be increased, and the thickness of the tin thin film is controlled to 0.1 μm, so that the durability can be improved.

5) Production of negative electrode body-2
After preparing a copper plating layer having a thickness of 7 μm on the surface of the polymethyl methacrylate film substrate, pretreatment, roughening treatment, electroless copper plating treatment, and Then, tin plating treatment was performed to produce a copper tin plating electrode. Thereafter, the copper tin plating electrode was subjected to a reduction firing process for 300 minutes in a reducing atmosphere of 200 ° C. (a mixed atmosphere of argon and hydrogen). Subsequently, a bellows treatment for folding the copper tin plating electrode that had undergone the reduction firing process into a three-layer bellows shape was performed. Thereafter, the copper tin plating electrode subjected to the bellows treatment was immersed in a cyclohexane solvent at 25 ° C. for 30 minutes to perform a substrate removal treatment for removing the substrate, whereby the negative electrode according to Example 2 The body was manufactured. On the other hand, by forming a tin thin film having a thickness of 3 μm on the surface of the electrolytic copper foil whose surface is not roughened by using the above-described tin plating treatment liquid, the negative electrode body according to Comparative Example 3 is obtained. Manufactured.

6) Durability Evaluation of Lithium Ion Secondary Battery CR2032-type coin battery incorporating the negative electrode body according to Example 2 above (hereinafter referred to as “lithium ion secondary battery of Example” or simply “Example”). A CR2032-type coin battery (hereinafter referred to as “a lithium ion secondary battery of a comparative example” or simply “comparative example”) incorporating the negative electrode body according to the comparative example 3 was prepared. In addition, the lithium ion secondary battery of an Example and the lithium ion secondary battery of a comparative example differed only in the negative electrode body, and other specifications were common. The battery capacities of the lithium ion secondary battery of the example and the lithium ion secondary battery of the comparative example were both 3 mAh.

  With the current C / 10, the initial capacities of the lithium ion secondary battery of the example and the lithium ion secondary battery of the comparative example were confirmed. Thereafter, the charge / discharge cycle of repeating charge / discharge at the current C / 5 (upper limit voltage 1.5V, lower limit voltage 0.01V) is repeated 50 times, and the ratio between the discharge capacity X of the first cycle and the discharge capacity Y of the 50th cycle From (100 × Y / X), the capacity retention rate (%) was evaluated. The results are shown in Table 1.

  From Table 1, the capacity retention rate of the lithium ion secondary battery of the example was 67%, whereas the capacity retention rate of the lithium ion secondary battery of the comparative example was 24%. That is, it was possible to improve durability by using the lithium ion secondary battery of the present invention having a bellows-like negative electrode body. Moreover, the negative electrode body of the present invention can increase the surface area. Therefore, according to the lithium ion secondary battery of the present invention having the bellows-like negative electrode body, capacity and durability can be improved.

It is a conceptual diagram which shows the example of the form of the electrical power collector 10 of this invention. It is a flowchart which shows the process example with which the manufacturing method of the electrical power collector of this invention is equipped. It is a conceptual diagram which shows the example of the process with which the manufacturing method of the electrical power collector of this invention is equipped. It is a conceptual diagram which shows the example of the form of the negative electrode body 20 of this invention concerning 1st Embodiment. It is a conceptual diagram which shows the example of a form of the negative electrode body 21 of this invention concerning 2nd Embodiment. It is a flowchart which shows the process example with which the manufacturing method of the negative electrode body of this invention concerning 1st Embodiment is equipped. It is a conceptual diagram which shows the example of the process with which the manufacturing method of the negative electrode body of this invention concerning 1st Embodiment is equipped. It is a flowchart which shows the process example with which the manufacturing method of the negative electrode body of this invention concerning 2nd Embodiment is equipped. It is a conceptual diagram which shows the form example of a bellows process. It is a conceptual diagram which shows the example of a form of the lithium ion secondary battery of this invention. It is a SEM image of the electrolytic copper foil surface after completion | finish of a roughening process. It is a SEM image of the collector surface concerning an Example. It is a SEM image of the collector surface concerning a comparative example. It is a SEM image of the negative electrode body surface concerning an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Concave part 2 ... Acicular copper 3 ... Convex part 10 ... Current collector 11 ... Tin thin film 20, 21 ... Negative electrode body 30 ... Base material 40 ... Current collector 50 ... Positive electrode layer 60 ... Separator 70 ... Electrolyte solution 100 ... Lithium ion secondary battery

Claims (9)

And a copper layer having a plurality of recesses having a depth of not less than 4 μm and not more than 8 μm on the surface, and a needle-like copper having a length of not less than 0.5 μm and not more than 2 μm protruding on the entire surface. body. A negative electrode body comprising: the current collector according to claim 1; and a tin thin film formed on a surface of the current collector. The negative electrode body according to claim 2, wherein the negative electrode body is bent in a bellows shape. A lithium ion secondary battery comprising the negative electrode body according to claim 2. A roughening step of forming a plurality of recesses having a depth of 4 μm or more and 8 μm or less on the surface of the copper layer by etching;
Using a liquid containing at least hypophosphorous acid as a reducing agent, acicular copper having a length of 0.5 μm or more and 2 μm or less is projected by electroless plating on the surface of the copper layer that has undergone the roughening step. An electroplating process;
A method for producing a current collector, comprising: A roughening step of forming a recess having a depth of 4 μm or more and 8 μm or less on the surface of the copper layer by etching;
Using a liquid containing at least hypophosphorous acid as a reducing agent, acicular copper having a length of 0.5 μm or more and 2 μm or less is projected by electroless plating on the surface of the copper layer that has undergone the roughening step. An electroplating process;
Forming a tin plating layer on the surface of the copper layer that has undergone the electroless plating step, and a tin plating step;
The manufacturing method of the negative electrode body characterized by having. The copper layer is a copper plating layer formed on the substrate surface,
After the tin plating step, a substrate removing step for removing the substrate is provided,
The method of manufacturing a negative electrode body according to claim 6, further comprising a bellows step of bending the base member into a bellows shape before the base material removing step. The method for producing a negative electrode body according to claim 6, further comprising a reduction firing step of firing the copper tin plating electrode in a reducing atmosphere after the tin plating step. The negative electrode body according to claim 7, further comprising a reduction firing step of firing the copper tin plating electrode in a reducing atmosphere between the tin plating step and the base material removal step. Manufacturing method.