JPWO2004049476A1 - Negative electrode current collector for non-aqueous electrolyte secondary battery and method for producing the same - Google Patents

Abstract

The negative electrode current collector for a non-aqueous electrolyte secondary battery of the present invention is made of a metal foil that can be a current collector of a non-aqueous electrolyte secondary battery, and the roughness of each surface of the foil is an average surface roughness of 10 points. Rz is 3 to 10 μm, the weight per unit area is 40 to 320 g / m 2, and a sufficiently chargeable / dischargeable metal or alloy is supported on both sides or one side as a negative electrode active material. And The metal is preferably copper, iron, cobalt, nickel, zinc, silver, or an alloy of those metals.

Description

  The present invention relates to a negative electrode current collector for a non-aqueous electrolyte secondary battery, and more particularly, a non-aqueous electrolyte solution that can prevent peeling of a negative electrode active material such as tin or tin alloy from the current collector due to charge / discharge. The present invention relates to a negative electrode current collector for a secondary battery.

Electrolytic copper foil is obtained by using a drum made of titanium or stainless steel as a cathode, using a dimension stabilizing electrode or lead as an anode, performing electrolysis in a sulfuric acid copper sulfate electrolytic bath, and winding up the deposited copper as a foil. . In this case, the drum facing surface called a so-called glossy surface in the copper foil has a smooth shape in which the smooth state of the drum surface is transferred. On the other hand, the precipitation surface called a so-called mat surface varies from a smooth state to a rough state depending on the bath composition and electrolysis conditions. That is, one surface of the electrolytic copper foil is always a smooth surface. A method is also known in which an electrolytic copper foil having such characteristics is further induced in an electrolytic cell, and copper is electrodeposited on both surfaces to roughen both surfaces (see JP-A-6-260168). . There is also known a method for producing an ultrathin copper foil having a smooth surface by forming a release layer on a glossy surface of an electrolytic copper foil used as a carrier foil and electrodepositing copper on the release layer (Japanese Patent Laid-Open No. Hei. 11-317574). Furthermore, an electrolytic copper foil with a carrier foil is also obtained by forming a bonding interface layer in which an organic agent and metal particles are mixed on the surface of a carrier foil made of copper, and forming an electrolytic copper foil layer on the bonding interface layer. It is known (see JP 2001-140090 A).
By the way, various non-aqueous electrolyte secondary batteries using an electrolytic copper foil as a negative electrode current collector have been proposed. For example, a current collector is known in which a 10-point average surface roughness Rz of a glossy surface of an electrolytic copper foil having a thickness of 9 μm is 2.00 μm and a mat surface Rz is 3.52 (Japanese Patent Laid-Open No. 9-306504). No. publication). This current collector carries carbon as a negative electrode active material. In this current collector, the contact between the current collector and the negative electrode active material is reduced by making the Rz of one surface smaller than 3.0 μm and the difference in Rz between the other surface and 2.5 μm or less. To try to improve. That is, a feature of the invention is to reduce Rz of each surface of the current collector. However, no study has been made on the use of tin or a tin alloy that has been attracting attention in recent years as a negative electrode active material having a high capacity. According to the study by the present inventors, when tin or a tin alloy is supported on the current collector as a negative electrode active material to form a negative electrode, the negative electrode undergoes volume expansion due to charge / discharge in the negative electrode, resulting in a drop. It has been found that peeling occurs.

Accordingly, an object of the present invention is to provide a non-aqueous electrolyte secondary that can prevent a negative electrode active material made of a metal or an alloy such as tin or a tin alloy from peeling off from a current collector due to charge / discharge. An object is to provide a negative electrode current collector for a battery.
As a result of diligent investigations to achieve the above object, the present inventors have used metals and alloys such as tin and tin alloys as the negative electrode active material, unlike the findings described in JP-A-9-306504. In some cases, it has been found that it is preferable to roughen the surface of the foil used as the current collector to a certain extent, rather than smoothing.
The present invention has been made on the basis of the above knowledge, and is made of a metal foil that can be a current collector of a non-aqueous electrolyte secondary battery. The roughness of each surface of the foil is expressed by an average surface roughness Rz of 10 points. 3 to 10 μm, the weight per unit area is 40 to 320 g / m ² , and a sufficient charge / dischargeable metal or alloy is supported on both sides or one side as a negative electrode active material. The object is achieved by providing a negative electrode current collector for a water electrolyte secondary battery.
In addition, the present invention provides a preferred method for producing the current collector,
The metal is deposited on the peripheral surface of the cathode drum by electrolysis, and the deposited metal is peeled off from the peripheral surface to obtain a carrier foil. The deposition surface of the carrier foil is subjected to a peeling treatment, and the peeling treatment surface is electrolyzed. The present invention provides a method for producing a negative electrode current collector for a non-aqueous electrolyte secondary battery, wherein the metal is deposited, and the deposited metal is peeled from the carrier foil to obtain a replica foil.
In addition, the present invention supports a sufficiently chargeable / dischargeable metal or alloy as a negative electrode active material on both sides or one side of a current collector made of a metal foil that can be a current collector of a non-aqueous electrolyte secondary battery. In the negative electrode for a non-aqueous electrolyte secondary battery,
The foil has a surface roughness of 10 to 10 μm and an average surface roughness Rz of 3 to 10 μm, and a weight per unit area of 40 to 320 g / m ^2. A negative electrode for a secondary battery is provided.

FIG. 1A to FIG. 1D are process diagrams showing a method for producing a current collector of the present invention.
2 (a) to 2 (c) are scanning electron micrograph images showing the surface state of the copper foil in the manufacturing process in the manufacturing method shown in FIGS. 1 (a) to 1 (d).
FIG. 3A to FIG. 3C are process diagrams showing another method for producing the current collector of the present invention.

Hereinafter, the present invention will be described based on preferred embodiments thereof. The current collector of the present invention is made of a metal that can be a current collector of a non-aqueous electrolyte secondary battery. In particular, it is preferably made of a metal that can be a current collector of a lithium secondary battery. Examples of such a metal include copper, iron, cobalt, nickel, zinc, silver, and alloys of these metals. Among these metals, it is particularly preferable to use copper or an alloy thereof. Therefore, the following description will be focused on copper foil. As the copper foil, both electrolytic copper foil and rolled copper foil are used. Among these, it is preferable to use an electrolytic copper foil that makes it easy to make the surface roughness of the copper foil in the range described later and that makes it easy to make the copper foil extremely thin. In general, the electrolytic copper foil is obtained by performing electrolysis in a sulfuric acid copper sulfate electrolytic bath using a rotating drum as a cathode, depositing copper on the peripheral surface of the drum, and peeling the deposited copper.
The copper foil used in the present invention has a relatively rough surface of 3 to 10 μm in terms of the roughness of each surface expressed by 10-point average surface roughness Rz (JIS B0601). The 10-point average surface roughness Rz is the absolute height of the highest peak from the highest peak to the fifth peak measured from the average line of the portion extracted by the reference length L from the longitudinal section curve of the copper foil in the direction of the vertical magnification. The difference between the average value of the values and the average value of the absolute values of the depths of the bottom valley from the lowest valley bottom to the fifth is obtained. In the present invention, Rz was measured using a surface roughness / contour shape measuring instrument SEF-30D manufactured by Kosaka Laboratory Ltd.
As described above, each surface of the copper foil has a relatively rough Rz of 3 to 10 μm, preferably 4 to 7 μm. According to the study by the present inventors, when tin or a tin alloy is used as the negative electrode active material, it is preferable that each surface of the copper foil is relatively rough, unlike when carbon or the like is used as the negative electrode active material. It has been found. The present inventors speculate that the reason is as follows. A negative electrode active material such as tin or tin alloy is generally supported on a current collector made of copper foil by electrolysis. Alternatively, it is supported by applying a paste containing particles of the negative electrode active material on a current collector. Therefore, when the surface of the copper foil is smooth, the electrodeposited layer of the active material is also formed smoothly. Under this condition, when the volume expansion of the active material occurs due to charging / discharging of the battery, the active material has nowhere to go due to the volume expansion and cracks are generated in the active material layer. Delamination will occur. On the other hand, when the surface of the copper foil is relatively rough, the electrodeposited layer of the active material is formed rougher than when the surface of the copper foil is smooth. That is, the surface of the electrodeposition layer is relatively uneven. This unevenness provides an escape area for the volume expansion of the active material when the volume expansion of the active material occurs due to charging / discharging of the battery. As a result, the active material is less likely to be pulverized or peeled off, and the life of the battery is prolonged.
Rz on each surface of the copper foil does not have to be the same value, and any surface may be in the above range. Moreover, the uneven | corrugated state (surface profile) in each surface of copper foil does not need to be the same. However, it is preferable from the viewpoint of improving the battery performance that each surface has the same surface profile as possible. A method for producing a copper foil having such a surface profile will be described later.
The Rz value of each surface of the copper foil needs to be within the above-mentioned range, and in addition, the size (height and depth) of the unevenness is relatively uniform on each surface. It is preferable that no part or deep recess exists. This also makes it difficult for the active material to be pulverized or peeled off due to the charging / discharging of the battery, thereby prolonging the battery life. The maximum height R _max is appropriate as a parameter representing such a surface shape. R _max is defined as the maximum value among the five values when the roughness curve is equally divided and the interval between the highest peak and the deepest valley is obtained for each section. In the present invention, it is preferable that R _max of each surface of the copper foil is 3.3 to 11.5 μm, particularly 4.5 to 8 μm.
The copper foil constituting the current collector is preferably thin from the viewpoint of improving battery performance. Specifically, the thickness of the copper foil is preferably in an extremely thin state of about 5 to 20 μm, particularly about 8 to 15 μm. However, in such an extremely thin copper foil, the above-described value of Rz being a relatively large value of 3 to 10 μm may obscure the definition of the thickness of the copper foil. Therefore, in the present invention, instead of the thickness of the copper foil, the weight per unit area of the copper foil is used as a measure of the thickness. The copper foil preferably has a weight per unit area of 40 to 320 g / m ² , particularly 44 to 180 g / m ² . When converting the weight per unit area and the thickness, the density of copper was 8.96 g / cm ³ .
The copper foil constituting the current collector preferably has a tensile strength of 25 kgf / mm ² or more, particularly 35 kgf / mm ² or more from the viewpoint of good workability during battery assembly. For the same reason, the elongation of the copper foil is preferably more than 2% and not more than 20%, particularly not less than 4% and not more than 15%. Tensile strength and elongation are measured under the conditions of a distance between gauge points of 50 mm and a tensile speed of 50 mm / min using Autograph AG-I manufactured by Shimadzu Corporation. A copper foil having such mechanical characteristics can be obtained by appropriately adjusting the type and / or concentration of various additives such as chlorine and glue added to the electrolytic bath.
Next, a preferred method for producing the current collector of the present invention will be described with reference to the drawings, taking copper foil as an example. First, a carrier copper foil is produced by electrolysis. The method of electrolysis is as described above. That is, using a rotating drum as a cathode, electrolysis is performed in a sulfuric acid copper sulfate electrolytic bath to deposit copper on the drum peripheral surface. Carrier copper foil is obtained by peeling the deposited copper from the drum peripheral surface. This carrier copper foil is used as a mold for a target copper foil. Therefore, it is preferable to provide a sufficient strength by making the thickness relatively large. As shown in FIG. 1A, the cross section of the carrier copper foil 1 has a smooth glossy surface on one surface and a mat surface 1a having an uneven surface on the other surface. The glossy surface is the surface facing the drum peripheral surface, and the mat surface 1a is a precipitation surface. The mat surface 1a is adjusted so that Rz is about 3 to 10 μm by appropriately adjusting electrolysis conditions. An electron micrograph of an example of the surface state of the mat surface 1a is shown in FIG.
Next, the matte surface 1 of the carrier copper foil 1 is peeled off. Examples of the release treatment agent include nitrogen-containing compounds and sulfur-containing compounds described in paragraphs [0037] to [0038] of JP-A-11-317574 described above, and paragraph [0020] of JP-A-2001-140090. Examples include a mixture of the nitrogen-containing compound or sulfur-containing compound described in [0023] and copper fine particles. Further, as a peeling process, a chromate process or a nickel plating process may be performed.
After the mat surface 1 is subjected to a peeling treatment, copper is deposited thereon by electrolysis. By this electrolysis, a replica copper foil 2 is formed on the mat surface of the carrier copper foil 1 as shown in FIG. The replica copper foil 2 is formed so that the weight per unit area is 40 to 320 g / m ² . The surface shape of the carrier copper foil facing surface in the replica copper foil 2, that is, the surface facing the mat surface (hereinafter, this surface is referred to as the lower surface) 2b is complementary to the mat surface. Moreover, the surface shape of the upper surface 2a in the replica copper foil 2 is adjusted so that Rz is about 3 to 10 μm by appropriately adjusting the electrolysis conditions. As electrolytic conditions for obtaining such a surface shape, for example, when a copper sulfate-based solution is used in an electrolytic bath, for example, the concentration of copper is 30 to 100 g / l, the concentration of sulfuric acid is 50 to 200 g / l, chlorine The concentration may be 30 ppm or less, the liquid temperature may be 30 to 80 ° C., and the current density may be 1 to 100 A / dm ² . When using a copper pyrophosphate solution in the electrolytic bath, the copper concentration is 10 to 50 g / l, the potassium pyrophosphate concentration is 100 to 700 g / l, the liquid temperature is 30 to 60 ° C., the pH is 8 to 12, and the current is the density may be set to 1 to 10 a / dm ^2.
Next, as shown in FIG.1 (c), the replica copper foil 2 is peeled from the carrier copper foil 1 in a peeling process surface. In the replica copper foil 2 thus obtained, the Rz of each surface is 3 to 10 μm. This replica copper foil 2 is used as a current collector.
Since the lower surface 2b of the replica copper foil 2 has a complementary shape to the mat surface 1a of the carrier copper foil 1, the surface shape of the lower surface 2b is not uniform, and an active material such as tin or tin alloy is electrodeposited. May be somewhat inappropriate. An electron micrograph of an example of the surface state of the lower surface 2b is shown in FIG. Accordingly, as a post-processing, a small amount of copper 3 is deposited by electrolysis on the lower surface 2b of the replica copper foil 2, that is, the carrier copper foil facing surface of the replica copper foil 2, as shown in FIG. It is preferable to form and to arrange the surface irregularity shape of the lower surface 2b. Further, the formation of the thin layer 3 also has an advantage that the surface irregularity shape of the lower surface 2b becomes close to that of the upper surface 2a. The degree of copper deposition is preferably about 2 μm or less, which is a range in which the thin layer 3 is extremely thin and uniformly formed on the surface of the lower surface 2b and does not affect the value of Rz. FIG. 2C shows an electron micrograph of an example of the state of the lower surface 2b whose surface shape is thus adjusted. The replica copper foil 2 processed thereafter can be used as a current collector.
Another preferable method for producing the current collector of the present invention is shown in FIGS. In this manufacturing method, until the replica copper foil 2 is obtained, operations similar to those shown in FIGS. 1A to 1C described with respect to the manufacturing method described above are performed. However, the thickness of the replica copper foil 2 is set to about several tens of μm. When the replica copper foil 2 is obtained, a peeling process is performed on the lower surface of the replica copper foil 2 as shown in FIG. The peeling process can be the same as the peeling process performed on the mat surface 1 a of the carrier copper foil 1.
After performing a peeling process on the lower surface 2b, copper is deposited on the surface by electrolysis. As shown in FIG. 3B, the second replica copper foil 4 is formed on the lower surface 2b of the replica copper foil 2 by this electrolysis. The second replica copper foil 4 is formed so that its weight per unit area is 40 to 320 g / m ² . The surface shape of the replica copper foil facing surface of the second replica copper foil 4, that is, the surface facing the lower surface 2 b is complementary to the lower surface 2 b. In other words, the surface shape of the upper surface 4a of the second replica copper foil 4 is the same as the shape of the mat surface 1a of the carrier copper foil 1 manufactured first. As already described regarding the manufacture of the carrier copper foil 1, the mat surface 1 a has an Rz of 3 to 10 μm, so the Rz of the upper surface 4 a of the second replica copper foil 4 is also 3 to 10 μm.
On the other hand, the surface shape of the lower surface 4a of the second replica copper foil 4 is set such that Rz is about 3 to 10 μm by appropriately adjusting the electrolysis conditions. The electrolysis conditions for obtaining such a surface shape can be the same as the electrolysis conditions of the replica copper foil 2 manufactured previously.
Next, as shown in FIG.3 (c), the 2nd replica copper foil 4 is peeled from the replica copper foil 2 in a peeling process surface. In the second replica copper foil 4 thus obtained, Rz of each surface thereof is 3 to 10 μm. Each surface has an approximate surface uneven shape. Accordingly, each surface has a surface state suitable for electrodeposition of tin or a tin alloy. The second replica copper foil 4 can also be used as a current collector.
As still another method of the production method of the present invention, on the surface of the replica copper foil 2 obtained in FIG. 1 (c) or FIG. 1 (d) or the second replica copper foil 4 obtained in FIG. 3 (c), The method of performing a roughening process and / or a rust prevention process is mentioned. By performing these treatments, when a negative electrode active material to be described later is supported on the surface of the obtained foil, there is an advantage that the adhesion between the foil and the negative electrode active material is increased and the battery characteristics are improved.
As a roughening treatment, after a plating treatment for forming a granular metal on the surface of the foil is performed, the granular metal is covered with a dense plating layer so as not to impair the irregular shape due to the granular metal. A plating process is mentioned. The former plating process is called so-called burn plating, and the latter plating process is called so-called overlay plating. Such a roughening treatment is known as a method for roughening the surface of a copper foil for printed circuits, and is disclosed in, for example, Japanese Patent Publication No. 53-39376. Burn plating is a plating in which granular metal is deposited by a current in the vicinity of the limit current density, and overplating is a non-granular dense plating layer that is formed in a granular form by a current of about the limit current density or less. It is plating which deposits so that a metal may be covered.
Examples of the antirust treatment include (i) metal plating treatment, (ii) chromate treatment, (iii) silane coupling treatment, and the like. In the metal plating process, zinc, nickel, cobalt, or an alloy thereof is plated on the surface of the foil to prevent foil corrosion (copper corrosion in this embodiment). From the viewpoint of preventing copper corrosion, it is preferable to perform zinc or zinc alloy plating. Specifically, alloy plating such as zinc-copper, zinc-nickel, zinc-cobalt, zinc-nickel-copper, zinc-nickel-cobalt, and zinc-copper-tin can be used.
In the chromate treatment, the foil is treated with a solution containing chromic acid or dichromate as a main component to form a rust preventive coating on the surface. The anticorrosive film formed by this treatment is made of, for example, a chromium-containing metal layer, a chromium alloy layer made of a copper chromium alloy, or a chromium oxide layer. The chromate treatment is defined in JIS Z 0103, for example.
In the silane coupling treatment, the surface of the foil is treated with a silicon-containing compound generally known as a silane coupling agent. For example, R-SiX ₃ (X is a hydrolyzable substituent such as an alkoxy group or halogen, and R is a substituent having a functional group such as a vinyl group, an epoxy group, or an amino group that easily reacts with an organic substance. ) Can be used as a silane coupling agent.
There is no restriction | limiting in particular in the order of a roughening process and a rust prevention process. For example, only the roughening treatment may be performed, or only one of the rust prevention treatments (i) to (iii) may be performed. Moreover, you may combine two or more of said (i)-(iii). For example, chromate treatment or silane coupling treatment can be performed after metal plating treatment. In addition, the chromate treatment and the silane coupling treatment can be performed in this order after the metal plating treatment. Furthermore, a chromate treatment can be performed first, followed by a silane coupling treatment.
A roughening process and a rust prevention process can also be combined. For example, a roughening process can be performed first and then a rust prevention process can be performed. The order of the rust prevention treatment can be as described above.
A negative electrode active material is supported on each surface or one surface of the copper foil produced by each of the above methods to form a negative electrode for a non-aqueous electrolyte secondary battery. As the negative electrode active material, a sufficiently chargeable / dischargeable metal or alloy is used. Examples of such metals or alloys include group 13 elements and group 14 elements of the periodic table. For example, tin, aluminum, germanium, or an alloy of these metals can be given. Among these, it is particularly preferable to use tin or a tin alloy. Examples of the tin alloy include tin-copper, tin-bismuth, tin-iron, and tin-cobalt. These metals or alloys are supported by being deposited on the copper foil by electrolysis. Or it is carry | supported by apply | coating the paste containing the particle | grains of these metals or alloys on a collector. A non-aqueous electrolyte secondary battery including such a negative electrode includes a positive electrode, a separator, and a non-aqueous electrolyte in addition to the negative electrode. The form of the battery may be any of a cylindrical shape, a square shape, a coin shape, a button shape and the like. In the secondary battery thus obtained, even if charging and discharging are repeated, the active material on the negative electrode is prevented from peeling off, and the life of the battery is significantly increased.
The present invention is not limited to the embodiment. For example, in the above-described embodiment, description has been made centering on copper, which is a preferred example, as a metal that can be a current collector of a non-aqueous electrolyte secondary battery. However, the present invention is not limited to copper. For example, iron, cobalt, nickel It is equally applicable to other metals and alloys such as zinc or silver or alloys of these metals.
Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited to such examples.

Copper foil was manufactured according to the method shown to Fig.1 (a)-(c). The Rz of the mat surface of the carrier copper foil in the production process was 3.2 μm and the thickness was 18 μm. Rz and R _max of the weight as well as each side per unit area of the resulting copper (replica foil) are shown in Table 1. The table also lists the tensile strength and elongation of the copper foil.

A copper foil was obtained in the same manner as in Example 1 except that the Rz of the matte surface of the carrier copper foil in the production process was 4.7 μm and the thickness was 35 μm. Rz and R _max of the weight as well as each side per unit area of the resulting copper (replica foil) are shown in Table 1. The table also lists the tensile strength and elongation of the copper foil.

The steps shown in FIGS. 1A to 1C were the same as those in Example 2. Thereafter, as a post process, copper was deposited on the lower surface of the replica copper foil by electrolysis to form a thin layer. Rz and R _max of the weight as well as each side per unit area of the resulting copper (replica copper foil to form a thin layer of copper on the lower surface) are as shown in Table 1. The table also lists the tensile strength and elongation of the copper foil.

The steps shown in FIGS. 1A to 1C were the same as those in Example 2. However, the weight per unit area of the replica copper foil was 98.6 g / m ² . Then, 2nd replica copper foil was obtained according to the method shown to Fig.3 (a)-FIG.3 (c) with respect to replica copper foil. Rz and R _max of the weight as well as each side per unit area of the resulting copper foil (second replica copper foil) are shown in Table 1. The table also lists the tensile strength and elongation of the copper foil.

Examples 5-8

表１及び表２に示す結果から明らかなように、各実施例で得られた銅箔を負極の集電体として用いた二次電池は、比較例の銅箔を負極の集電体として用いた二次電池と同程度の不可逆容量及び初期容量を示し、更に２０サイクル容量維持率及び充放電効率が比較例の二次電池よりも向上していることが判る。特に、銅箔にスズめっきを施して負極を作製した実施例１〜４と、銅箔にスズペーストを塗布して負極を作製した実施例５〜８とで、２０サイクル容量維持率がほぼ同等であること、即ちサイクル特性がほぼ同等であることに留意すべきである。スズをペーストで塗布すると、めっきする場合に比較してスズと銅箔との密着性が低下しやすい、つまりサイクル特性が低下しやすい。しかし実施例５〜８では、粗化処理を行っており、それによって銅箔とスズとの密着性が高まっているので、実施例１〜４とほぼ同等のサイクル特性を達成している。The steps shown in FIGS. 1A to 1C were the same as those in Example 2. Thereafter, as a post-process, roughening treatment and rust prevention treatment were performed in this order. For the rust prevention treatment, galvanization treatment, chromate treatment and silane coupling treatment were carried out in this order (Example 5). The burn-off plating in the roughening treatment was performed for 10 seconds at a current density of 10 A / dm ² using a plating solution having a composition of sulfuric acid: copper sulfate = 4: 5 (weight ratio). After the burnt plating, the plate was washed with water and covered. The covering plating was performed for 1 minute using a plating solution having a composition of sulfuric acid: copper sulfate = 1: 4 (weight ratio) at a current density of 5 A / dm ² . Example 6 is the same as Example 5 except that the silane coupling treatment is not performed. Example 7 is the same as Example 5 except that chromate treatment and silane coupling treatment are not performed. Example 8 is the same as Example 5 except that no rust prevention treatment is performed. Rz and R _max of the weight as well as each side per unit area of the resulting copper (replica foil) are shown in Table 1. The table also lists the tensile strength and elongation of the copper foil.
[Comparative Example 1]
The carrier copper foil in Example 1 was used as it was.
[Comparative Example 2]
The carrier copper foil in Example 2 was used as it was.
[Performance evaluation]
Tin was deposited on the surfaces of the copper foils obtained in Examples 1 to 4 and Comparative Examples 1 and 2 by electrolysis to produce electrodes. The precipitation amount of tin was 14.6 g / m ² . Moreover, the tin paste was apply | coated to the surface of the copper foil obtained in Examples 5-8, and the electrode was created. The supported amount of tin was 44.5 g / m ² . Using the obtained electrode, a non-aqueous electrolyte secondary battery was produced as follows. The irreversible capacity (%), initial capacity (mAh / g), 20 cycle capacity retention rate (%), and charge / discharge efficiency (%) at 10 cycles were evaluated by the following methods. The results are shown in Tables 1 and 2.
<Production of non-aqueous electrolyte secondary battery>
Metal lithium was used as the counter electrode, and the electrode obtained above was used as the working electrode, and both electrodes were opposed to each other via a separator. Further, a nonaqueous electrolyte secondary battery was produced by a conventional method using a mixed solution (1: 1 volume ratio) of LiPF ₆ / ethylene carbonate and diethyl carbonate as a nonaqueous electrolyte.
<Irreversible capacity>
[1- (initial discharge capacity / initial charge capacity)] × 100
That is, it indicates the capacity remaining in the active material after being charged but not discharged.
<Initial capacity>
Indicates the initial discharge capacity.
<20 cycle capacity maintenance rate>
(20 cycle capacity retention rate) = {(20th cycle discharge capacity) / (maximum discharge capacity)} × 100
<Charge / discharge efficiency at 10 cycles>
(Charge / discharge efficiency at 10th cycle) = {(discharge capacity at 10th cycle) / (charge capacity at 10th cycle)} × 100

As is clear from the results shown in Tables 1 and 2, the secondary battery using the copper foil obtained in each example as the negative electrode current collector was used as the negative electrode current collector. It can be seen that the irreversible capacity and initial capacity are comparable to those of the secondary battery, and that the 20-cycle capacity retention rate and the charge / discharge efficiency are improved compared to the secondary battery of the comparative example. In particular, Examples 1 to 4 in which a negative electrode was produced by applying tin plating to a copper foil and Examples 5 to 8 in which a negative electrode was produced by applying a tin paste to a copper foil had almost the same 20 cycle capacity retention rate. It should be noted that the cycle characteristics are almost the same. When tin is applied as a paste, the adhesion between tin and the copper foil is likely to be lower than in the case of plating, that is, the cycle characteristics are likely to be reduced. However, in Examples 5-8, since the roughening process is performed and the adhesiveness of copper foil and tin is increasing by it, the cycling characteristics substantially equivalent to Examples 1-4 are achieved.

  According to the negative electrode current collector for a non-aqueous electrolyte secondary battery of the present invention, the negative electrode active material made of metal or alloy including tin and tin alloy is peeled off from the current collector due to charge and discharge. This can be prevented. Therefore, the secondary battery using the current collector has a low deterioration rate and a long life even when charging and discharging are repeated.

Claims (13)

It consists of a metal foil that can be a current collector of a non-aqueous electrolyte secondary battery, the roughness of each surface of the foil is 3 to 10 μm in terms of 10-point average surface roughness Rz, and the weight per unit area is 40 A negative electrode current collector for a non-aqueous electrolyte secondary battery, which is ˜320 g / m ² and has a sufficient charge / dischargeable metal or alloy supported on both sides or one side as a negative electrode active material. The negative electrode current collector for a nonaqueous electrolyte secondary battery according to claim 1, wherein the tensile strength is 25 kgf / mm ² or more and the elongation is more than 2% and 20% or less. The negative electrode current collector for a non-aqueous electrolyte secondary battery according to claim 1, wherein the negative electrode active material is made of tin, aluminum, germanium, or an alloy of these metals. The negative electrode current collector for a non-aqueous electrolyte secondary battery according to claim 1, wherein the metal or alloy is made of copper or an alloy thereof. The negative electrode current collector for a non-aqueous electrolyte secondary battery according to claim 1, wherein the metal or alloy comprises iron, cobalt, nickel, zinc, silver, or an alloy of these metals. A method for producing a negative electrode current collector for a nonaqueous electrolyte secondary battery according to claim 1, comprising:
The metal is deposited on the peripheral surface of the cathode drum by electrolysis, and the deposited metal is peeled off from the peripheral surface to obtain a carrier foil. The deposition surface of the carrier foil is subjected to a peeling treatment, and the peeling treatment surface is electrolyzed. A method for producing a negative electrode current collector for a non-aqueous electrolyte secondary battery, wherein the metal is deposited, and the deposited metal is peeled from the carrier foil to obtain a replica foil. The non-aqueous solution according to claim 6, wherein after obtaining the replica foil, a small amount of the metal is deposited by electrolysis on the carrier foil facing surface of the replica foil to adjust the surface irregularity shape of the carrier foil facing surface. A method for producing a negative electrode current collector for an electrolyte secondary battery. After obtaining the replica foil, the surface of the replica foil facing the carrier foil is stripped, the metal is deposited on the stripped surface by electrolysis, and the deposited metal is stripped from the replica foil. The method for producing a negative electrode current collector for a nonaqueous electrolyte secondary battery according to claim 6, wherein a two-replica foil is obtained. Nonaqueous electrolysis in which a sufficiently chargeable / dischargeable metal or alloy is supported as a negative electrode active material on both sides or one side of a current collector made of a metal foil that can be a current collector of a nonaqueous electrolyte secondary battery In the negative electrode for a liquid secondary battery,
The foil has a surface roughness of 10 to 10 μm and an average surface roughness Rz of 3 to 10 μm, and a weight per unit area of 40 to 320 g / m ^2. Negative electrode for secondary battery. The negative electrode for a non-aqueous electrolyte secondary battery according to claim 9, wherein the negative electrode active material is made of tin, aluminum, germanium, or an alloy of these metals. The negative electrode for a nonaqueous electrolyte secondary battery according to claim 9, wherein the metal or alloy is made of copper or an alloy thereof. The negative electrode for a non-aqueous electrolyte secondary battery according to claim 9, wherein the metal or alloy comprises iron, cobalt, nickel, zinc, silver, or an alloy of these metals. A nonaqueous electrolyte secondary battery comprising the negative electrode for a nonaqueous electrolyte secondary battery according to claim 9.

Images