JP2008041347A - Negative electrode for lithium ion secondary battery, and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a negative electrode for a lithium ion secondary battery that is excellent in cycle characteristics, by preventing an active material from being peeled off or falling off from a Cu foil or a Cu alloy foil being a current collector, even when charge/discharge are repeated although having a high discharge capacity. <P>SOLUTION: After applying Sn plating onto the surface of a negative-electrode current collector 2 composed of a Cu foil or a Cu alloy foil, the Sn plating is Cu-Sn-alloyed by executing prescribed heat treatment so as to manufacture the negative electrode 1 for a lithium ion secondary battery by forming a Cu-Sn alloy layer 3. Plasma treatment is applied onto the surface of the negative-electrode current collector 2 before applying the Sn plating onto the surface. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a negative electrode for a lithium ion secondary battery and a negative electrode for a lithium ion secondary battery.

  Lithium ion secondary batteries are now widely used in mobile devices. As a negative electrode of a lithium ion secondary battery, a carbon-based material is formed as an active material on a negative electrode current collector made of Cu foil or Cu alloy foil.

  This negative electrode for a lithium ion secondary battery is generally a rolled Cu foil or rolled Cu alloy foil, or an electrolytic Cu foil or electrolytic Cu alloy foil coated with a carbon-based material dissolved in a binder and a solvent, Obtained by drying and hot roll pressing.

In the carbon-based material, LiC ₆ that is a compound of carbon and lithium acts as an active material, and lithium ions can be occluded by intercalation or released by deintercalation.

At this time, the theoretical discharge capacity (maximum capacity) per unit weight of LiC ₆ is said to be 372 mAh / g. Since the capacity of the carbon-based active material cannot be increased beyond this value, recently, a Sn-based active material having a higher discharge capacity (approximately 1000 mAh / g for Li _4,4 Sn), a Si-based active material. Studies on practical use such as (approximately 4000 mAh / g for Li _4,4 Si) are being actively conducted.

In the Sn-based material, when Sn is formed on the Cu foil surface by electrolytic plating and heat treatment is performed at 200 ° C. for 24 hours, the plating layer changes to a multilayer structure of Sn / Cu ₆ Sn ₅ / Cu ₃ Sn, There is a report that cycle characteristics are improved in order to relieve stress due to expansion and contraction of an active material during charge and discharge and suppress separation (see Non-Patent Document 1).

  In such a conventional method for producing a negative electrode for a lithium ion secondary battery, an apparatus 41 for producing a negative electrode for a lithium ion secondary battery as shown in FIG. 4 is used. In this manufacturing apparatus 41, the coil c made of the Cu foil 2 is sent out from the sending machine 42, the pretreatment such as degreasing and pickling of the Cu foil 2 is performed in the pretreatment apparatus 43, and the Sn foil is applied to the Cu foil 2 in the plating treatment apparatus 45. Plating is performed, this is heat-treated with a heat treatment device 46, and the negative electrode for a lithium ion secondary battery obtained with a winder 47 is taken up.

In addition, in a negative electrode for a lithium ion secondary battery using Cu ₆ Sn ₅ as an active material, the Cu foil base material is subjected to Sn plating and subjected to heat treatment, or Cu—Sn alloy plating with a cyan plating solution. Cu ₆ Sn ₅ is formed (see Patent Document 1).

Nobuyuki Tamura and 4 others, “Electrochemical characteristics of high-capacity tin negative electrode materials for lithium secondary batteries”, Sanyo Electric Technical Report, Vol. 34, No1, pp. 87-93 (2002) JP 2004-87232 A Japanese Patent Laid-Open No. 7-252657

  The development of batteries is progressing to a point where the carbon-based material is almost close to the theoretical capacity, and it is difficult to greatly improve the discharge capacity in the future. For this reason, as described above, Sn-based and Si-based materials have been developed.

  However, these materials have a drawback that volume expansion is extremely large when lithium ions are occluded. Specifically, the volume expansion of the carbon-based material is 1.5 times, whereas the volume expansion of the Sn-based material is about 3.5 times and that of the Si-based material is about 4 times.

  Due to this large volume change, the active material is pulverized from the Cu foil as a current collector along with the charge / discharge cycle, causing a problem that the battery characteristics are drastically deteriorated. It was the biggest obstacle.

  Therefore, in the case of Sn-based materials, attempts have been made to use it as a thin film of Sn alloy or Sn compound (hereinafter referred to as “alloy” includes “compound”) rather than as a thin film of pure Sn.

For example, Cu ₆ Sn ₅ which is a Sn compound has been studied for use as a negative electrode active material. The method for forming Cu ₆ Sn _{5 includes,} as described in Patent Document 1, a method of performing a heat treatment after performing Sn plating on a Cu foil substrate, and a method of directly performing Cu—Sn alloy plating with a cyan plating solution. Are known.

However, although Cu ₆ Sn ₅ is formed as an active material by these methods, the collapse of the active material due to expansion / contraction associated with charge / discharge is reduced, but it has not been sufficient.

  In addition, the method using a cyan plating solution has a problem in terms of safety and environment, and there is a problem that a manufacturing facility such as a waste liquid treatment becomes large and causes a cost increase.

  For this reason, a negative electrode for a lithium ion secondary battery having further excellent cycle characteristics without lowering the negative electrode active material from the Cu foil or Cu alloy foil, which is a current collector, even after repeated charging and discharging, and a low cost Therefore, a manufacturing method excellent in environmental safety has been demanded.

  Accordingly, the object of the present invention is to eliminate such problems and prevent the active material from being peeled off or dropped from the Cu foil or Cu alloy foil as a current collector even when charging and discharging are repeated while having a high discharge capacity. An object of the present invention is to provide a method for producing a negative electrode for a lithium ion secondary battery excellent in cycle characteristics and a negative electrode for a lithium ion secondary battery.

  The present invention was devised in order to achieve the above object, and the invention of claim 1 is characterized in that a predetermined heat treatment is performed after Sn plating is applied to the surface of a negative electrode current collector made of Cu foil or Cu alloy foil. In the method for producing a negative electrode for a lithium ion secondary battery by forming a Cu—Sn alloy layer by applying the Sn plating to a Cu—Sn alloy, before applying Sn plating to the surface of the negative electrode current collector And a method for producing a negative electrode for a lithium ion secondary battery, wherein the surface is subjected to plasma treatment.

  Invention of Claim 2 is a manufacturing method of the negative electrode for lithium ion secondary batteries of Claim 1 which performs the said heat processing for 5-200 hours at 150-231 degreeC.

The invention of claim 3, wherein the Cu-Sn alloy layer is a Cu ₆ Sn ₅ compound in which claim 1 or 2 for a lithium ion secondary battery negative electrode manufacturing method according.

  A fourth aspect of the present invention is the method for producing a negative electrode for a lithium ion secondary battery according to any one of the first to third aspects, wherein the surface of the negative electrode current collector is preliminarily roughened by Cu plating or etching. It is.

  A fifth aspect of the present invention is a negative electrode for a lithium ion secondary battery manufactured using the manufacturing method according to any one of the first to fourth aspects.

  According to the present invention, the Sn plating adhesion is remarkably increased, and the effect is maintained even after the heat treatment. Therefore, the Cu foil or Cu which is a current collector even when charging and discharging are repeated while having a high discharge capacity. A negative electrode for a lithium ion secondary battery having excellent cycle characteristics can be produced without causing the active material to peel off or fall off from the alloy foil.

  As a result of intensive studies to achieve the above object, the inventors of the present invention performed plasma treatment on the surface of the negative electrode current collector made of Cu foil or Cu alloy foil before Sn plating. It was found that the surface purification effect and the surface activation treatment by the treatment were successful. By this plasma treatment, the adhesion with the Sn-plated Cu foil or Cu alloy foil applied to the surface of the Cu foil or Cu alloy foil is remarkably increased as compared with the case where the plasma treatment is not performed.

  As a result, the present inventors have excellent cycle characteristics while having a high discharge capacity without causing the active material to peel off or drop off from the Cu foil or Cu alloy foil as the current collector even when charging and discharging are repeated. The knowledge that a negative electrode for a lithium ion secondary battery can be obtained has been obtained, and the present invention has been completed based on this knowledge.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the accompanying drawings.

  Fig.1 (a)-FIG.1 (c) are figures which show the manufacturing method of the negative electrode for lithium ion secondary batteries which is the suitable 1st Embodiment of this invention.

As shown in FIG.1 (c), the negative electrode 1 for lithium ion secondary batteries which concerns on 1st Embodiment is from the compound of Cu and Sn on the surface of the negative electrode collector 2 which consists of Cu foil or Cu alloy foil. A Cu—Sn alloy layer 3 containing an intermetallic compound such as a Cu ₆ Sn ₅ compound is formed.

  The Cu—Sn alloy layer 3 is formed into a Cu—Sn alloy by subjecting the negative electrode current collector 2 made of Cu foil or Cu alloy foil and a Sn plating film formed on the surface thereof to a predetermined heat treatment. Can be obtained.

The Cu foil used in the present invention may be a rolled Cu foil or an electrolytic Cu foil, but if the active material expands with the charge / discharge cycle, a large tensile stress is applied to the Cu foil, so a Cu foil with as high a strength as possible is recommended. Is done. In this sense, a rolled Cu foil to which a high-strength Cu alloy can be applied is preferable. For example, a normal rolled Cu foil or electrolytic Cu foil has a tensile strength of about 300 to 400 N / mm ² , but if a Cu—Ni—Si-based so-called Corson Cu alloy is used, a high strength of 700 N / mm ² or more is obtained. A rolled Cu foil can be obtained. Therefore, it is preferable to use such a Cu foil as the negative electrode current collector 2.

  A Cu plating film may be formed on the surface of the negative electrode current collector 2 in advance by performing Cu plating for forming an intermetallic compound by reacting with Sn.

  At this time, in order to maintain the adhesion between the Cu plating film and the negative electrode current collector 2, it is preferable that the surface of the negative electrode current collector 2 is subjected to a roughening treatment in advance by Cu plating or etching. The effect is demonstrated if the surface roughness is Ra = 0.1 μm or more.

  This roughened surface is also effective in securing adhesion during the charge / discharge cycle of the Cu—Sn alloy layer 3. Therefore, in order to prevent the roughened unevenness from changing to the Cu—Sn alloy layer 3 due to diffusion, a diffusion barrier layer made of Ni, Co, or the like is formed on the roughened surface formed by the roughening treatment to 1 μm or less. You may form on the roughening surface by thickness.

  Here, the manufacturing apparatus of the negative electrode for lithium ion secondary batteries used for the manufacturing method of the negative electrode 1 for lithium ion secondary batteries which concerns on 1st Embodiment is demonstrated.

  As shown in FIG. 2, the negative electrode manufacturing apparatus 21 for a lithium ion secondary battery has basically the same configuration as the manufacturing apparatus 41 described in FIG. 4 except for the plasma processing apparatus 24.

  That is, the manufacturing apparatus 21 is a continuous processing apparatus for the negative electrode current collector 2, and includes a feeder 22 that sends out a coil c around which a strip-shaped negative electrode current collector 2 made of Cu foil or Cu alloy foil is wound, and a negative electrode current collector. A pretreatment device 23 for pretreatment of the surface of the body 2, a plasma treatment device 24 such as a high-frequency plasma generator for plasma-treating the surface of the negative electrode current collector 2 after the pretreatment, and a surface of the negative electrode current collector 2 after the plasma treatment A plating treatment device 25 for performing Sn plating on the substrate, a heat treatment device 26 for heat-treating the negative electrode current collector 2 after the plating treatment, and a winder 27 for winding up the negative electrode 1 for lithium ion secondary batteries obtained thereby. Prepare.

  Next, the manufacturing method of the negative electrode 1 for lithium ion secondary batteries is demonstrated.

  First, as shown in FIG. 2, the coil c formed of the negative electrode current collector 2 is sent out by the feeder 22, and the pretreatment (degreasing, pickling, etc.) of the surface of the negative electrode current collector 2 is performed by the pretreatment device 23. The roughening treatment of the surface of the negative electrode current collector 2 may be performed before the pretreatment or may be performed immediately after the pretreatment.

  Then, before the Sn plating is applied to the negative electrode current collector 2, the plasma processing is performed on the surface of the negative electrode current collector 2 by the plasma processing apparatus 24.

The plasma treatment is performed by generating plasma P by direct discharge, high frequency discharge or microwave discharge in N ₂ gas, inert gas such as Ar, He, Ne, Kr, Xe, or a mixed gas thereof ( FIG. 1 (a)). Each gas may contain about several percent O ₂ . The gas flow rate is preferably 30-60 sccm. The plasma treatment time is preferably 5 to 30 minutes.

Thereafter, Sn plating is performed on the surface of the negative electrode current collector 2 after the plasma treatment by the plating treatment apparatus 25 to form the Sn plating film 11 (FIG. 1B). The thickness of the Sn plating film 11 is preferably 5 μm or more. Sn plating may be electroplating or electroless plating. Usually, electroplating is performed in a sulfuric acid bath in which SnSO ₄ is dissolved.

  Further, a heat treatment (thermal diffusion) step is subsequently performed on the negative electrode current collector 2 after the plating treatment by the heat treatment apparatus 26. The heat treatment is preferably performed at 150 to 231 ° C. for 15 to 200 hours.

The reason is that if the heat treatment temperature is as low as less than 150 degrees or the heat treatment time is less than 15 hours, the alloy is not alloyed and the formation of Cu ₆ Sn ₅ becomes insufficient, and the heat treatment time exceeds 200 hours. This is because if it is long, it takes too much production time and the production cost becomes high. Further, when the heat treatment temperature is 232 ° C. or higher, Sn becomes higher than the melting point of Sn and Sn is melted.

  In this heat treatment step, Cu or Cu alloy and Sn are reacted to form Sn-plated film 11 as a Cu—Sn alloy, and Cu—Sn alloy layer 3 containing these intermetallic compounds is formed (FIG. 1C). ), The negative electrode 1 for a lithium ion secondary battery is obtained.

The intermetallic compound contained in the Cu—Sn alloy layer 3 is preferably a Cu ₆ Sn ₅ compound. Cu ₆ Sn ₅ is excellent in charge / discharge capacity and cycle characteristics. As an intermetallic compound contained in the Cu—Sn alloy layer 3, a Cu ₃ Sn compound may be generated. However, since the Cu ₃ Sn compound has a small charge / discharge capacity, a Cu ₆ Sn ₅ compound is desirable.

  The operation of the first embodiment will be described.

  The manufacturing method of the negative electrode 1 for a lithium ion secondary battery according to the present embodiment is such that the surface of the negative electrode current collector 2 made of Cu foil or Cu alloy foil is subjected to plasma treatment before Sn plating is performed. Yes.

In the plasma P, ions and radical atoms of N ₂ gas and inert gas are generated, and these ions and radical atoms act on the surface of the negative electrode current collector 2, so that the surface of the negative electrode current collector 2 is surfaced. Impurities such as O, C, and hydrocarbon are removed, and the surface of the negative electrode current collector 2 is cleaned (surface cleaning effect by plasma treatment).

Further, ions and radical atoms generated by the plasma P act on the surface of the negative electrode current collector 2, so that the surface of the negative electrode current collector 2 has the same diameter as that of N ₂ gas or inert gas ions or radical atoms. As a result, a large number of fine pores are formed, so that the surface of the negative electrode current collector 2 is activated (surface activation effect by plasma treatment).

  According to the manufacturing method according to the present embodiment, the surface of the negative electrode current collector 2 is subjected to plasma treatment, so that the surface cleaning effect and the surface activation effect are obtained, and the negative electrode current collector made of Cu foil or Cu alloy foil is obtained. The adhesion between the Sn plating film 11 and the negative electrode current collector 2 can be significantly increased as compared with the case of normal Sn plating in which Sn plating is performed immediately after pretreatment (degreasing, pickling, etc.). The effect of this adhesion is maintained even after heat treatment.

Therefore, according to the manufacturing method according to the present embodiment, the Cu—Sn alloy layer 3 as an active material from the Cu foil or Cu alloy foil that is the negative electrode current collector even when charging and discharging are repeated while having a high discharge capacity. Thus, the negative electrode 1 for a lithium ion secondary battery having excellent cycle characteristics can be produced without causing the Cu ₆ Sn ₅ compound contained in the material to peel off or fall off.

  Moreover, the negative electrode 1 for lithium ion secondary batteries manufactured with the manufacturing method which concerns on this embodiment is the negative electrode collector 2 which consists of Cu foil or Cu alloy foil, and Cu-Sn alloy compared with the conventional plating single film | membrane. Since the adhesiveness with the layer 3 is good, the Cu—Sn alloy layer 3 does not fall off from the negative electrode current collector 2 even if the charge / discharge cycle is repeated, and the life is long.

  In particular, in order to absorb internal stress due to deformation of the negative electrode current collector, a hole having a plane anisotropy such as a rhombus shape, an ellipse shape, a ship shape, etc., rather than a simple flat Cu foil or Cu alloy foil. In many cases, a Cu foil or a Cu alloy foil having a complex shape such as a concavo-convex shape or a mesh shape is used as a negative electrode current collector (see, for example, JP-A-2005-32524).

  Even if the negative electrode current collector of such a concave and convex shape or mesh shape is complicated, if the manufacturing method according to the present embodiment is used, the entire surface of the negative electrode current collector can be uniformly cleaned and activated. The effect which it did is exhibited more notably.

  A second embodiment will be described.

  As shown in FIG. 3B, the negative electrode 31 for a lithium ion secondary battery has a Cu—Sn alloy layer 3 formed on the surface of the negative electrode current collector 2, and further porous (porous) Sn. This is a negative electrode structure in which a Sn oxide film layer 4 made of an oxide film is formed. An infinite number of extremely fine holes may be formed in the Sn oxide film layer 4 along the film thickness direction.

These fine holes contribute to a significant increase in reaction sites during the reaction between lithium ions and the Sn oxide film layer 4 via the electrolyte, and smooth lithium ion doping / de-doping (intercalation / deintercalation). To improve charge / discharge characteristics. In addition, it is considered that the Li _x Sn compound is finally generated by the reaction between the lithium ions and the Sn oxide film layer 4.

  Conventionally, the active material was pulverized due to the significant volume expansion at this time, and the cycle characteristics deteriorated. However, in the negative electrode 31 for a lithium ion secondary battery, the Sn oxide film layer 4 has a porous structure, thereby reducing the volume. Expansion was relieved and cycle characteristics were greatly improved.

  The size of the holes needs to be extremely fine, and the diameter needs to be several hundred nm or less, preferably 100 nm or less.

  In order to form such fine holes along the film thickness direction, a method of anodizing the Sn oxide film layer 4 can be employed. For example, the Sn plating film can be formed by performing constant potential electrolysis in an oxalic acid solution. The size of the hole and the oxide film formation thickness are controlled by the potential and time at this time.

More specifically, after the step of FIG. 1B, as shown in FIG. 3A, the surface side of the Sn plating film 11 is anodized to form a SnO _x film (Sn oxide film layer) 32. . At this time, it is necessary not to use the entire Sn plating film 11 as an oxide film, but to partially leave Sn on the negative electrode current collector 2 side.

  Subsequently, by performing a heat treatment (thermal diffusion) step, as shown in FIG. 3B, the remaining Sn reacts with Cu on the Cu foil side to form these Cu-Sn alloy layers 3, When the Sn oxide film layer 4 is formed to form a negative electrode structure, a negative electrode 31 for a lithium ion secondary battery is obtained.

This negative electrode 31 for a lithium ion secondary battery greatly improves the cycle characteristics as compared with the case of using only the Cu—Sn alloy layer 3. The temperature of the thermal diffusion process at this time may be equal to or lower than the melting point of Sn, and the time is taken so that Cu ₆ Sn ₅ that is an intermetallic compound is generated as much as possible and Cu ₃ Sn and remaining Sn are reduced as much as possible. To do.

  As described above, it is necessary to form Sn with a thickness of 5 μm on the Cu foil in order to ensure the normal charge / discharge capacity. The thickness to be polished is preferably 1/3 or less of the entire Sn plating film 11. Sn oxide reacts with Li to produce Li oxide and Sn, but Li oxide does not contribute to the charge / discharge cycle because it is not reduced again. Therefore, if the Sn oxide film layer 4 is made too thick, the irreversible capacity increases, which is not preferable.

  As described above, the negative electrode 31 for a lithium ion secondary battery manufactured by the manufacturing method according to the second embodiment has a Cu—Sn Cu—Sn alloy layer 3 formed on the negative electrode current collector 2 and a porous Sn. It is covered with an oxide film layer 4. For this reason, a lithium ion secondary battery having a high energy density, excellent cycle characteristics, and capable of being reduced in size can be supplied as compared with a conventional carbon-based active material as a negative electrode.

(Example)
A rolled Cu foil having a thickness of 18 μm was prepared, and first, roughening treatment was performed by electrodeposition of Cu. The conditions were an electrolytic solution of copper sulfate 150 g / L and sulfuric acid 150 g / L. After electrolysis at a liquid temperature of 30 ° C. and a current density of 20 A / dm ² , copper sulfate 250 g / L and sulfuric acid 100 g / L of electrolytic solution A Cu plating was performed at a liquid temperature of 30 ° C. and a current density of 10 A / dm ² to obtain a surface roughness Ra = 0.12 μm.

  After the roughening treatment, the surface of the negative electrode current collector 2 made of Cu foil fed out from the coil c is subjected to a pretreatment consisting of degreasing and pickling, followed by plasma treatment, and then electroplating by the method of FIG. Was applied with Sn plating at 5 μm to produce a negative electrode 1 for a lithium ion secondary battery.

More specifically, a high-frequency plasma generator is used as the plasma processing apparatus 24. After reducing the pressure in the chamber by 6.7 × 10 ⁻³ Pa (5 × 10 ⁻⁵ Torr), Ar gas is reduced to 66.7 Pa (0.5 Torr). ) And high-frequency plasma was generated for 20 minutes (30 W / cm ³ ).

Thereafter, Ni plating with a thickness of 0.3 μm was first applied in a normal watt bath to form a diffusion barrier layer. 2.7 μm-thick Cu plating is performed with the plating solution that has been subjected to the covering Cu plating, and further, the conditions of a stannous sulfate 50 g / L, sulfuric acid 100 g / L, and a current density of 3 A / dm ² in an appropriate amount of the plating solution Then, Sn plating was performed. The film thickness at this time was set to 7 μm.

  The Sn-plated Cu foil thus produced was further anodized under a predetermined condition in a 0.5 M oxalic acid solution, subsequently subjected to thermal diffusion treatment to prepare a negative electrode sample, and a test cell having metallic lithium as a counter electrode was manufactured. The charge / discharge characteristics were evaluated.

A polypropylene thin film was used as the separator, and a mixed solution (1: 1) of ethylene carbonate and diethyl carbonate in which 1M LiPF ₆ was dissolved was used as the electrolyte. Charging / discharging was performed at a constant current density of 0.25 mA / cm ^{2 in} the range of 0.01 to 1V.

(Conventional example)
For comparison with the examples, a rolled Cu foil having the same thickness of 18 μm was prepared, and the surface of the Cu foil fed out from the coil c was subjected to a pretreatment consisting of degreasing and pickling by the method of FIG. 5 μm of Sn plating was applied by electroplating to produce a conventional negative electrode for a lithium ion secondary battery.

  Here, in the negative electrode for lithium ion secondary batteries manufactured according to FIG. 2 and FIG. 4, the results of examining the discharge capacity maintenance rate with respect to the initial cycle after 10 cycles of the charge / discharge test are shown in Table 1.

  As can be seen from Table 1, in the examples in which the plasma treatment was performed, the discharge capacity of 80% was maintained even after 10 cycles of the charge / discharge test, and the cycle characteristics were excellent. On the other hand, in the conventional example in which the plasma treatment is not performed, the discharge capacity is only 11%, and the cycle characteristics are significantly inferior to those in the examples, and the effectiveness of the present invention has been proved.

  Table 2 shows the results of examining the adhesion between the negative electrode current collector and the Cu—Sn alloy layer after 10 cycles of the charge / discharge test. The evaluation method was performed by visual confirmation after dismantling the test cell.

  As shown in Table 2, in the example in which the plasma treatment was performed, the negative electrode current collector 2 and the Cu—Sn alloy layer 3 were in close contact with each other before charge / discharge and after 10 cycles. On the other hand, in the conventional example in which the plasma treatment is not performed, the negative electrode current collector and the Cu—Sn alloy layer that were in close contact before charging and discharging were peeled off after 10 cycles.

Fig.1 (a)-FIG.1 (c) are schematic diagrams which show the manufacturing method of the negative electrode for lithium ion secondary batteries which is the suitable 1st Embodiment of this invention. It is the schematic which shows an example of the manufacturing apparatus of the negative electrode for lithium ion secondary batteries used with the manufacturing method of the negative electrode for lithium ion secondary batteries which is suitable 1st Embodiment of this invention. FIG. 3A and FIG. 3B are schematic views showing a method for producing a negative electrode for a lithium ion secondary battery which is a preferred embodiment of the present invention. It is the schematic which shows the manufacturing apparatus of the conventional negative electrode for lithium ion secondary batteries.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Negative electrode for lithium ion secondary batteries 2 Negative electrode collector 3 Cu-Sn alloy layer

Claims (5)

  After Sn plating is applied to the surface of the negative electrode current collector made of Cu foil or Cu alloy foil, a predetermined heat treatment is performed to form the Cu—Sn alloy layer by forming the Sn plating into a Cu—Sn alloy. In the method for producing a negative electrode for a lithium ion secondary battery, the surface of the negative electrode current collector is subjected to a plasma treatment before Sn plating, and the method for producing a negative electrode for a lithium ion secondary battery is characterized in that .   The method for producing a negative electrode for a lithium ion secondary battery according to claim 1, wherein the heat treatment is performed at 150 to 231 ° C. for 5 to 200 hours. The method for producing a negative electrode for a lithium ion secondary battery according to claim 1, wherein the Cu—Sn alloy layer is a Cu ₆ Sn ₅ compound.   The method for producing a negative electrode for a lithium ion secondary battery according to any one of claims 1 to 3, wherein the surface of the negative electrode current collector is previously subjected to a roughening treatment by Cu plating or etching. A negative electrode for a lithium ion secondary battery manufactured using the manufacturing method according to claim 1.

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