JP2006040674A - Lithium ion battery anode material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithium ion battery anode material aiming at improvement of a cycle property and processibility of the battery. <P>SOLUTION: The lithium ion battery 1 has a structure of sealing an anode plate 2 and a cathode plate 3 wound through a separator 4 in an anode can 5. The anode plate 2 uses oxygen-free copper or tough-pitch copper as a base material and the copper material is formed by making the base material contain 1 to 5 wt.% of Ni, 0.2 to 1.2 wt.% of Si, 0.1 to 2.0 wt.% of Zn, and 0.03 to 0.2 wt.% of P. A copper foil is formed by applying a rolling process to the copper material, and the copper foil is used as an anode core material. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

    The present invention relates to a negative electrode material for a lithium ion battery having a copper foil as a core material, and more particularly to a negative electrode material for a lithium ion battery that has improved battery cycle characteristics and workability.

  With the widespread use of portable devices such as mobile phones and notebook personal computers, there is an increasing demand for small and high-capacity secondary batteries. Among them, lithium ion (hereinafter, also referred to as “Li ion”) secondary batteries are being used in many fields because of their light weight and high energy density.

  FIG. 1 shows a configuration of a cylindrical Li ion battery. The Li ion battery 1 has a can shape with a negative electrode plate 2, a positive electrode plate 3 disposed opposite to the negative electrode plate 2, a separator 4 disposed between the negative electrode plate 2 and the positive electrode plate 3. The bottom is the negative electrode terminal, and the negative electrode plate 5, the positive electrode plate 3 and the separator 4 are housed in a state where the negative electrode plate 2, the positive electrode plate 3, and the separator 4 are overwrapped. , A disc-shaped spacer 7 disposed on the upper portion of the positive electrode plate 3, and a safety valve disposed on the upper surface of the spacer 7 for releasing the gas pressure when the internal pressure increases ( A pressure release valve 8, a metal positive electrode lid (positive electrode terminal) 9 that is disposed on the upper surface of the safety valve 8 and is electrically connected to the positive electrode plate 3, and is disposed between the positive electrode plate 3 and the positive electrode lid 9. PTC (Positive Temperature Coefficien) that increases the electrical resistance when the temperature rises t) The device 10 includes a gasket 11 that insulates the upper edge of the negative electrode can 5 from the safety valve 8 and the positive electrode lid 9.

  The negative electrode plate 2 includes a copper foil as a core material and an active material such as a carbon-based material, and the active material is fixed to the copper foil surface by a binder. Moreover, the positive electrode plate 3 includes a copper foil as a core material, an active material such as lithium cobaltate, lithium nickelate, and lithium manganate, and a conductive agent, and these are fixed to the copper foil surface by a binder. Is done. In addition, in the negative electrode plate 2, since the active material itself has conductivity, a conductive agent is generally not required.

  The separator 4 holds an electrolytic solution obtained by mixing an organic solvent and a lithium salt and prevents a short circuit between the negative electrode plate 2 and the positive electrode plate 3. For example, a microporous film of polyethylene is used.

  FIG. 2 shows the configuration of the electrode part of the stacked Li-ion battery. The electrode section in FIG. 2 is configured by stacking a negative electrode plate 2 and a positive electrode plate 3 with a separator 4 therebetween to form a cell 12 and stacking a plurality of the cells 12 in the thickness direction.

  Each of the Li-ion batteries having the above-described configuration forms a secondary battery, and at the time of charging, lithium is released as ions from the positive electrode plate 3. In the negative electrode plate 2, lithium ions in the electrolytic solution are converted into lithium as the negative electrode plate 2. The battery is charged by being inserted into. On the other hand, at the time of discharging, lithium is released as ions from the negative electrode plate 2 into the electrolytic solution and inserted into the positive electrode plate 3, thereby discharging and functions as a battery.

  The copper foil used for the negative electrode plate 2 can be roughly divided into two depending on the production method. One is a rolled copper foil produced by rolling a material produced by casting, and the other is an electrolytic copper foil produced by electrolytic deposition of copper from a solution mainly composed of copper sulfate. .

  The rolled copper foil has a feature that excellent mechanical strength can be obtained by repeated rolling. The long copper foil thus obtained is obtained by applying an active material or the like to the surface and subjecting it to a heat treatment for drying to obtain a negative electrode material, and further cutting into a predetermined shape to obtain a negative electrode plate 2 is obtained.

  In recent years, the capacity of the negative electrode plate 2 has been increased, and the development of Si-based and Sn-based active materials has progressed from conventional carbon-based materials. These active materials are characterized by a large charge capacity compared to conventional carbon-based active materials, but have a problem of large expansion / contraction during charge / discharge. For this reason, when the copper foil used in the conventional carbon system is used, the copper foil is deformed due to the expansion of the active material to generate wrinkles, and the active material is removed, the copper foil is broken, and the recycling characteristics (repetition of charge / discharge) Frequency).

Therefore, a negative electrode material in which copper foil is alloyed to increase the strength has been proposed. For example, Cu-Ni-Si alloy foil, Cu-Fe alloy foil, Cu-Ag alloy foil, etc. are subjected to tin (Sn) plating. In addition, heat treatment is performed to form an intermetallic compound such as Sn—Ni, Sn—Fe, or Sn—Ag, thereby improving the charge / discharge cycle life (see, for example, Patent Documents 1, 2, and 3). .)
JP 2003-257417 A ([0007] to [0011]) JP 2003-257418 A ([0007] to [0011]) Japanese Patent Laying-Open No. 2004-6153 ([0008] to [0012])

  However, according to the conventional negative electrode material for lithium ion batteries, the tensile strength is at a high level, but the verification of cycle characteristics is up to 100 cycles, which is not a practical number of cycles, and is verified about 500 times. Is desired. In mass production, workability is important, but this point has not been studied.

  Accordingly, an object of the present invention is to provide a negative electrode material for a lithium ion battery that is improved in cycle characteristics and workability of the battery.

  In order to achieve the above object, the present invention provides a copper base material and Ni: 1 to 5 wt%, Si: 0.2 to 1.0 wt%, Zn: 0 contained in the copper base material Provided is a negative electrode material for a lithium ion battery, characterized by being a rolled copper foil containing 1 to 2.0 wt% and P: 0.03 to 0.2 wt%.

  According to the negative electrode material for a lithium ion battery of the present invention, tensile strength can be improved and cycle characteristics can be improved by using a copper base material containing four types of elements. Furthermore, since the ingot is not cracked during hot rolling, workability can be improved.

[Embodiment]
Hereinafter, embodiments of the present invention will be described. The embodiment of the present invention uses oxygen-free copper or tough pitch copper as a base material, Ni: 1 to 5 wt%, Si: 0.2 to 1.0 wt%, Zn: 0.1 to 2.0 wt%, P: A copper material is prepared by adding 0.03 to 0.2 wt% of each element to the base material, and the copper material is rolled to produce a copper foil having a desired thickness. After the material is provided to form a negative electrode material, the negative electrode plate 2 is cut into a predetermined shape.

[Effect of the embodiment]
According to this embodiment, the copper foil that is the core material of the negative electrode material contains inclusions made of Ni, Si, Zn, and P, and the ratio of Ni and Si is set to a predetermined value to thereby reduce the copper foil. By increasing the strength, the deformation of the copper foil due to expansion / contraction during charging / discharging is prevented, so that the cycle characteristics can be improved. Furthermore, since the ingot is not cracked or pinholes during hot rolling, workability can be improved.

  Next, examples of the present invention will be described. First, oxygen-free copper having an oxygen content of 10 ppm is used as a base material, and Ni: 2.5 wt%, Si: 0.5 wt%, Zn: 1.7 wt%, and P: 0.03 wt% are used as the base material. The contained ingot was melt cast. The ingot was hot rolled and processed to a thickness of 12 mm, and then cold rolling and annealing were repeated to produce a fabric material having a thickness of 200 μm. Furthermore, after annealing this material | dough material, it rolled to thickness 15micrometer, and formed the roughening process by electrodeposition on the surface so that it might become RZ: 3.0micrometer in a copper sulfate bath. When the tensile strength of the rolled copper foil thus obtained was measured and the workability was evaluated, the results shown in Table 1 were obtained.

  Next, Sn plating with a thickness of 10 μm is applied to the surface of the rolled copper foil to obtain a negative electrode material, and further cut into a predetermined shape to obtain a negative electrode plate 2 for a Li ion battery. It was created. The results shown in Table 2 are the results of the charge / discharge test (cycle characteristics).

  Further, a comparative material for the negative electrode plate 2 was prepared. The tough pitch copper used in the carbon-based Li-ion battery is Comparative Example 1, and the tensile strength, workability, and cycle characteristics are shown in Tables 1 and 2. Moreover, what is general with other copper alloy materials is shown as Comparative Examples 2-5. Since Comparative Examples 3 to 5 could not measure cycle characteristics, they were excluded from Table 2.

  Referring to Table 2, in the example, there was no deformation or breakage of the copper foil as the negative electrode core material, and the cycle characteristics were a good result of 500 times.

  Next, referring to Table 1, in the examples, sufficient tensile strength and good workability are obtained. On the other hand, although Comparative Example 1 has good workability, the tensile strength is low, and the copper foil is deformed during charge and discharge, and the active material (Sn) falls off. The cycle characteristics were 1/10 of the example. Since the comparative example 2 has higher tensile strength than the comparative example 1, the cycle characteristics are improved as compared with the comparative example 1, but it is still 2/5 of the example. In Comparative Examples 3 to 5, ingot cracking (hot cracking) and pinholes occurred during hot rolling, and rolling was impossible. For this reason, the tensile strength could not be measured, and the cycle characteristics and workability could not be evaluated.

  As is apparent from Table 1, according to the embodiment of the present invention, Ni: 2.5 wt%, Si: 0.5 wt%, Zn: 1.7 wt%, P: 0.03 wt%, and the remainder is Cu. The best results have been obtained. At this time, the ratio of the weight percent of Ni and Si is 2.5 / 0.5 = 5. Therefore, satisfactory tensile strength and workability can be obtained if the ratio of the weight percent of Ni and Si is in the range of 4.5 to 5.5.

  As described above, the rolled copper foil by cold rolling has a good result with a thickness of 15 μm. Therefore, the rolled copper foil can be expected to have the characteristics shown in Table 2 if the thickness is 30 μm or less.

[Other embodiments]
In the above embodiment, the Li ion battery has been described. However, the present invention can be applied not only to Li ion secondary batteries and Li ion primary batteries but also to Li polymer batteries using a thermoplastic polymer as a separator. Is possible.

  Moreover, although the roughening treatment of the dough material after cold rolling is electrodeposition, it is not limited to electrodeposition, and a mechanical roughening method such as shot blasting can also be used.

It is sectional drawing which shows the structure of a cylindrical Li ion battery. It is a perspective view which shows the structure of the electrode part of a stack type Li ion battery.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lithium (Li) ion battery 2 Negative electrode plate 3 Positive electrode plate 4 Separator 5 Negative electrode can 6 Tab 7 Spacer 8 Safety valve 9 Positive electrode lid 10 PTC element 11 Gasket 12 Cell

Claims (5)

A copper base material,
Ni: 1 to 5 wt%, Si: 0.2 to 1.0 wt%, Zn: 0.1 to 2.0 wt%, P: 0.03 to 0.2 wt% contained in the copper base material A negative electrode material for a lithium ion battery, characterized in that a rolled copper foil containing the inclusion is used as a core material.   2. The negative electrode material for a lithium ion battery according to claim 1, wherein a ratio by weight of Ni and Si is 4.5 to 5.5. 3.   2. The negative electrode material for a lithium ion battery according to claim 1, wherein the copper base material is oxygen-free copper or tough pitch copper.   The negative electrode material for a lithium ion battery according to claim 1, wherein the rolled copper foil has a thickness of 30 μm or less.   2. The negative electrode material for a lithium ion battery according to claim 1, wherein a surface of the rolled copper foil is roughened.

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