KR20090103979A - Method for producing electrode for lithium battery and electrode for lithium battery - Google Patents

Abstract

In forming a negative electrode active material film by vapor deposition using an evaporation raw material containing Si as a main component, an object of the present invention is to provide a lithium battery electrode with improved film formation speed, excellent productivity, and maintaining a high level of charge and discharge capacity. The method for producing an electrode for lithium batteries of the present invention comprises the steps of preparing an evaporation raw material containing Si and Fe in a molar ratio of Fe / (Si + Fe) of 0.005 or more and 0.15 or less, and dissolving and evaporating the evaporation material. And depositing the film directly on the current collector or with the underlying layer interposed therebetween. In the lithium battery electrode of the present invention, a current collector and SiFe _y O _x laminated on the current collector directly or with an underlying layer interposed therebetween (where O <x <2 and O.0001 ≦ y / (1 + y ) O.03).

Description

Lithium battery electrode and manufacturing method of lithium battery electrode {LITHIUM CELL ELECTRODE, AND METHOD FOR MANUFACTURING THE LITHIUM CELL ELECTRODE}

The present invention relates to a lithium battery electrode and a method for producing a lithium battery electrode, and more particularly to a method for forming a negative electrode active material film, and a lithium battery electrode that can be produced using the above method.

In recent years, miniaturization and multifunctionalization of portable devices have been progressed, and accordingly, high capacity of batteries has been demanded.

As a high capacity negative electrode in a lithium battery, Si-O negative electrode has many quantities which occlude lithium, and is promising and many are examined. As a method of forming Si-O in an electrical power collector, there exists a method of coating, drying, and rolling Si-O particle | grains as a paste by mixing with a binder and a solvent, a vapor deposition method, etc.

Among these methods, the vapor deposition method is a dry process that does not include a binder and is advantageous for high energy density, and is also excellent in productivity because a high film formation speed is obtained. Patent Document 1 discloses a method for forming a Si-O film by vacuum deposition, sputtering, and ion plating.

In patent document 2, in the negative electrode for secondary batteries in which the negative electrode active material layer was provided on the collector, the negative electrode active material layer contains Si and Fe, and the atomic ratio of both is 19: 1-1: 9, ie, in Si. It is described that the molar number of Fe with respect to 5.3% or more. In addition, it is described that this negative electrode active material layer is formed by binary simultaneous deposition.

Further, as an oxide of a polyelement-based material containing Si, Patent Document 3 mixes Fe and Si of Fe: Si = 98: 2 to 65:35 (atomic ratio) in order to obtain a Fe-Si-O-based magnetic film. A method of forming a film by vapor deposition using a material as an evaporation raw material is disclosed.

[Patent Document 1] Japanese Unexamined Patent Publication No. 2004-349237

[Patent Document 2] Japanese Unexamined Patent Publication No. 2007-26805

[Patent Document 3] Japanese Unexamined Patent Application Publication No. 10-92683

Problems to be Solved by the Invention

Patent Document 1 discloses using a mixed sintered body of a Si powder and a SiO ₂ powder or a SiO sintered body as an evaporation raw material for obtaining a Si-O film. According to Patent Document 1, from the viewpoint of the film formation rate, it is described that the Si-O powder sintered body is preferable, but when using the Si-O powder sintered body as an evaporation raw material, there is a problem that it is expensive to synthesize the Si-O powder. have.

In addition, Patent Document 1 also discloses that a Si agglomerate is used as an evaporation raw material and film formation is performed by introducing oxygen gas. According to this, the film | membrane is formed in oxidative atmosphere using the Si lump cut out from the Si ingot manufactured by the casting method as a material. As for the battery performance, one equivalent to that of the mixed sintered body can be obtained, and an oxidative atmosphere can be obtained by introducing oxygen gas. However, since it is necessary to dissipate Si atoms from the surface of the material, and splash is more likely to occur than the mixed sintered body, the film formation rate is only described as small, and the deposition using Si as a main component and oxygen gas is performed. No description is given of the means for improving the film formation speed in the method.

In the said patent document 2, in order to improve the output characteristic of a battery, setting the number-of-moles of Fe with respect to Si in a negative electrode active material layer to 5.3% or more is disclosed, When it becomes smaller than this ratio, it will charge and discharge of a negative electrode active material. It is described that the effect of suppressing the volume change which follows or the improvement of electroconductivity becomes small. There is no description regarding the number of moles of Fe in the negative electrode active material layer being less than 5.3%, and there is no mention of the relationship between the Fe content and the film formation rate. In addition, only two-way simultaneous deposition is described, and one-way deposition using evaporation raw material containing Si as a main component is not described.

Moreover, although the said patent document 3 made the material which mixed Fe and Si into an evaporation raw material, unlike the lithium battery electrode of this invention which has Si as a main component, the method of obtaining the oxide film which has Fe as a main component is disclosed. It's just that.

This invention solves the said subject and aims at improving productivity by improving a film formation speed in forming a negative electrode active material film by carrying out vapor deposition using the evaporation raw material which has Si as a main component.

Moreover, an object of this invention is to provide the lithium battery electrode which is excellent in productivity and also hold | maintains high level charge / discharge capacity | capacitance because the film-forming rate of a negative electrode active material film is improving.

Means to solve the problem

MEANS TO SOLVE THE PROBLEM In order to solve the said subject, the manufacturing method of the electrode for lithium batteries of this invention is a process of preparing the evaporation raw material containing Si and Fe in the molar ratio of Fe / (Si + Fe) 0.0005 or more and 0.15 or less; And evaporating and dissolving the evaporation raw material, and depositing the same on a current collector directly or with an underlying layer interposed therebetween.

According to this structure, in order to form a negative electrode active material film by performing vapor deposition using the evaporation raw material which has Si as a main component, productivity can be improved by improving the film formation speed.

In addition, the present invention provides a current collector and SiFe _y O _x (where 0 <x <2 and 0.0001 ≦ y / (1 + y) ≦ 0.03) directly or on a ground layer interposed therebetween. The present invention also relates to a lithium battery electrode comprising a negative electrode active material film.

By this structure, since the film formation rate of a negative electrode active material film is improving, the lithium battery electrode which is excellent in productivity and also hold | maintains high level charge / discharge capacity can be provided.

The present invention also relates to a lithium battery having a negative electrode made of a lithium battery electrode, a positive electrode provided to face the negative electrode, and a separator provided between the negative electrode and the positive electrode. A process for preparing an evaporation raw material containing a molar ratio of Fe / (Si + Fe) in a range of 0.0005 or more and 0.15 or less, dissolving and evaporating the evaporation raw material, and depositing it directly on a current collector or with an underlying layer therebetween. The present invention also relates to a method for producing a lithium battery, including a step of preparing a negative electrode, a step of preparing a separator, a step of preparing a positive electrode, and a step of installing the separator between the negative electrode and the positive electrode.

This structure can provide the lithium battery which has the negative electrode which is excellent in productivity, and also hold | maintains the high level charge / discharge capacity.

Effects of the Invention

According to the manufacturing method of the electrode for lithium batteries of this invention, film formation of a negative electrode active material film is carried out, without changing the process conditions (e.g., voltage and current of an electron beam when using the electron beam evaporation method) in the vapor deposition using the evaporation raw material which has Si as a main component. Can improve speed. Therefore, productivity can be improved.

Moreover, according to the electrode for lithium batteries of this invention, since the film formation rate of a negative electrode active material film is improving, it is excellent in productivity and can hold | maintain a high level charge / discharge capacity.

Moreover, according to the lithium battery of this invention and its manufacturing method, it can provide the lithium battery which hold | maintained the high level charge / discharge capacity, having a negative electrode excellent in productivity.

1 is a schematic diagram of a vacuum deposition apparatus in an embodiment of the present invention;

2 is a cross-sectional schematic diagram of an R2016 coin battery in an embodiment of the present invention.

Explanation of the sign

1: current collector 2: evaporation raw material

3: crucible 4: copper hearth

11: unwinding roll 12: can roll

13: winding roll 14: mask

15 chamber 16: oxygen nozzle

17 Mass Flow Controller 18 Oxygen Bombe

19: vacuum piping 20: oil diffusion pump

21: flow pump 31: electrode (cathode)

32: separator 33: lithium metal foil (anode)

34: metal disc 35: leaf spring

36: case 37: sealing plate

38: gasket

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described, referring drawings.

(Embodiment)

In this embodiment, the case where the electron beam vapor deposition method is used as a vapor deposition method is demonstrated.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the outline | summary of the manufacturing apparatus used for manufacture of the lithium battery electrode of this invention. In FIG. 1, the chamber 15 is evacuated, and the evaporation raw material 2 is evaporated to form a negative electrode active material film on the current collector 1.

The current collector 1 is released from the unwinding roll 11, moves along the main surface of the can roll 12, and wound around the unwinding roll 13. When the current collector 1 moves along the can roll 12, an active material film is formed on the current collector 1 through the opening of the mask 14. The evaporation raw material 2 is put into a material container, and is heated and evaporated by an electron beam (not shown). The material container is configured by, for example, arranging the crucible 3 in a water-cooled copper hearth 4. There is an oxygen nozzle 16 in the chamber 15, and the oxygen gas derived from the oxygen cylinder 18 is controlled by the massflow controller 17 in a predetermined amount and introduced into the chamber 15. Thereby, a film forming process is performed in oxygen atmosphere. The chamber 15 is evacuated using the oil diffusion pump 20 and the oil rotation pump 21 via the vacuum exhaust pipe 19. In this way, a SiFe _y O _x film is formed as a negative electrode active material film on the current collector 1.

Metal foil can be used as the electrical power collector 1, and copper, aluminum, stainless steel, nickel, titanium, etc. can be used as a metal. As plate | board thickness, it is about 1-50 micrometers. Although an underlayer may be provided on the surface of the electrical power collector 1, chromium oxide etc. can be used as an underlayer, for example.

As evaporation raw material 2 of this invention, the thing containing Si and Fe and whose molar ratio of Fe / (Si + Fe) is 0.0005 or more and 0.15 or less can be used. Compared to the case where only the evaporation raw material is Si, when the main component contains Si and a small amount of Fe, the present inventors have found that the film formation rate is improved. If the molar ratio is less than 0.0005 or exceeds 0.15, the effect of improving the film formation speed is not obtained. Within this range, when the compounding amount of Fe increases, the charge / discharge capacity of the lithium battery tends to decrease, so that the amount of Fe blended is preferably smaller in order to maintain a high level of charge / discharge capacity. From this point of view, the upper limit of the molar ratio is preferably 0.06 or less, more preferably 0.03 or less, and even more preferably 0.026 or less. The lower limit of the molar ratio can be further improved, and the electrical resistance of the obtained negative electrode active material film can be reduced, preferably 0.005 or more, more preferably 0.01 or more. The lower the electrical resistance expressed by the surface resistivity or the like of the obtained negative electrode active material film, the lower the chargeability of the electrode is, and the adhesion of particles to the electrode is suppressed in the process of assembling the battery. In addition, it is possible to reduce the impedance of the battery by reducing the resistance of the negative electrode active material film, whereby the discharge characteristics at the time of discharge at a large current or at a low temperature environment can be improved.

In the present invention, one-way deposition using the evaporation raw material is performed. Here, the single deposition means deposition using one evaporation raw material containing both Si and Fe, and is different from the binary deposition carried out by putting an evaporation raw material containing Si and an evaporation raw material containing Fe in a separate crucible. Are distinguished. Since it is easy to uniformize the composition of the obtained SiFe _y O _x film, the one-way deposition is more preferable than the two-way deposition because the performance of the obtained negative electrode active material film is stabilized and the film forming apparatus can be made simpler.

The evaporation raw material used in the present invention is based on Si as a main component, and is different from the main component of a compound in which Si and O are bonded, such as SiO or SiO ₂ . The evaporation raw material used in the present invention may be a compound powder or a compound agglomerate such as an alloy containing Si as a main component containing a predetermined ratio of Fe, or a powder or agglomeration of Si and a powder or agglomeration of Fe. The evaporation raw material is melted near the melting point of Si by heating with an electron beam, and a small amount of Fe is homogenized in the Si melt, so the state of the evaporation raw material before dissolution may be somewhat uneven.

When the continuous supply is carried out using the evaporation raw material according to the present invention during film formation, film formation is possible for a long time and productivity is preferable.

The crucible containing the evaporation raw material is preferably made of carbon. Carbon crucibles are less likely to react with the Si melt and are resistant to thermal shock, so they are less likely to break during deposition or at the end of deposition, and can be used repeatedly. The crucible material is not limited to carbon, and other materials having low reactivity with the Si melt and resisting thermal shock may be used.

In addition, although the mechanism of improving the film formation speed in the present invention is unknown, the ionization energy is 7.87 eV in Fe, 8.15 eV in Si, and the beam tightening of the electron beam is compared with the case of Si only due to the difference in ionization energy. It is thought that this improves, and the local hot water of the evaporation raw material increases, and the deposition amount improves. From such a mechanism, the improvement of the deposition rate in the present invention is an effect achieved only in the case of one-way deposition, and is considered not to be achieved in the case of two-way deposition.

Performed in the production method of the present invention under an oxygen atmosphere to obtain a negative electrode active material film is made of SiFe _y O _x. Here, x is in a range that satisfies the expression: 0 <x <2 and y is in a range that satisfies 0 ≦ y / (1 + y) ≦ about 0.1. As a film thickness of the negative electrode active material film obtained, about 0.1-50 micrometers is suitable, for example.

Since the charge / discharge capacity of a lithium battery tends to decrease as the ratio of Fe increases in the obtained SiFe _y O _x film, the molar ratio of y / (1 + y), that is, Fe / (Si + Fe) is smaller. This is preferred. When the SiFe _y O _x film is used as a negative electrode active material film to produce a lithium battery for charge and discharge, when the y / (1 + y) is 0.0001 or more and 0.03 or less, a charge and discharge capacity almost equivalent to that of a SiO _x film containing no Fe is obtained. Can be achieved. When y / (1 + y) exceeds 0.03, since the charge / discharge capacity is remarkably lowered, it is not preferable. Since the film-forming speed can be improved further and the electrical resistance of the obtained film | membrane can be reduced, it is preferable that the minimum of the value of y / (1 + y) is 0.001 or more, and it is more preferable that it is 0.004 or more. Further, since the charge / discharge capacity equivalent to or higher than that of the SiO _x film containing no Fe (that is, the value of y / (1 + y) is 0) can be achieved, the value of y / (1 + y) The upper limit of is preferably 0.015 or less, and more preferably 0.011 or less.

In the SiFe _y O _x film, x satisfies the formula: 0 <x <2, but the range of 0.1 ≦ x ≦ 1.0 is preferable. If the ratio of oxygen is small, there is a tendency for the cycle characteristics to deteriorate, and if the ratio of oxygen is large, the charge and discharge capacity tends to decrease, so the value of x is preferably in this range.

The lithium battery electrode is remarkably superior in terms of productivity while achieving the same charge / discharge capacity as compared with the conventional product using the SiO _x film containing no Fe by the above structure. The electrode for lithium batteries of the present invention is used as a negative electrode in a lithium battery.

Moreover, the negative electrode for lithium secondary batteries of this invention is applicable to a cylindrical battery, a square battery, etc. which have a coin type battery, a spiral type electrode group. For example, the positive electrode active material layer, lithium cobalt oxide (LiCoO _2), lithium nickel oxide (LiNiO _2), but can use the lithium-containing transition metal oxides such as lithium manganese oxide (LiMn ₂ O _4), the invention is not limited to this. In addition, the positive electrode active material layer may be composed of only a positive electrode active material, or may be composed of a mixture containing a positive electrode active material, a binder, and a conductive agent.

The present invention will be described in more detail with reference to the following Examples, but the present invention is not limited to these Examples.

(Example 1)

A single crystal Si ingot made of high purity chemical was broken into a size of about 1 cm and made into agglomerate, and 190 g of Si and 10.2 g of Fe were mixed using iron powder having a purity of 99.99% or more of high purity chemical. ) Into a carbon crucible (3). The molar ratio of Fe / (Si + Fe) in the evaporation raw material was about 0.026. Moreover, as molar composition expressed by a percentage, it is about 2.6 mol%.

Using the vacuum vapor deposition apparatus shown in FIG. 1 mentioned above, film-forming was performed using the roughening electrolytic copper foil (35 micrometers in thickness) made from Furukawa Circuit Foil Co., Ltd. as a collector 1. . The current collector 1 moves along the main surface of the can roll 12 from the unwinding roll 11 at a speed of 1.0 cm / minute and is wound around the winding roll 13. When the current collector 1 moves along the main surface of the can roll 12, a negative electrode active material film is formed when the opening length in the current collector longitudinal direction passes through the opening of the mask 14 having a length of 15 cm. Therefore, the film formation time is 15 minutes. On the lower side facing the can roll 12, a carbon crucible 3 containing the evaporation raw material 2 was placed in a water-cooled copper heart 4 and heated with an electron beam having an acceleration voltage of -10 kV and an emission current of 650 mA. The oxygen nozzle 16 is arrange | positioned in the chamber 15, the oxygen gas of the flow volume 40SCCM controlled by the mass flow controller 17 from the oxygen gas cylinder 18 is introduce | transduced, and the oil diffusion pump 20 and the oil The vacuum was exhausted to 0.01 Pa by the rotary pump 21. Under the above conditions, a long electrode was produced by continuously forming a negative electrode active material film on the current collector 1 by vacuum deposition.

When the obtained film was observed by SEM in cross section, the thickness was 26 µm, and the film formation speed was 29 nm / sec.

The amount of Si and the amount of Fe of the obtained film were analyzed by ICP emission spectrometry, and the amount of O was analyzed by JIS Z2613 infrared absorption method. As a result, the amount of Si was 2.9 mg / cm 2, the amount of Fe was 0.062 mg / cm 2, and the amount of O was 0.88 mg / cm 2. Therefore, the composition of the film in the form of SiFe _y O _x is SiFe _0.011 O _0.53 , and the molar ratio of Fe / (Si + Fe), that is, y / (1 + y), of the film was about 0.011. It was 3.9E + 8 ohms / square when the obtained said sample measured the surface resistivity using the URS probe by the high resistivity hysteristor by Mitsubishi Chemical.

The sample obtained by drilling a circular hole having a diameter of 12.5 mm was used as an electrode 31 as a cathode. The separator 32 of a polyethylene microporous membrane having a thickness of 20 µm made by Asahi Kasei was 300 µm thick. Using the lithium metal foil 33 as an anode, a coin battery (20 mm in diameter and 1.6 mm in thickness) of R2016 was produced. The outline of the cross section of a coin battery is shown in FIG. Metal disc 34 for collecting current from electrode 31, plate spring 35 for pressurizing electrode, case 36 for sealing and acting as a positive terminal from outside, sealing plate 37 and gasket Using (38), a solution prepared by mixing ethylene carbonate and diethyl carbonate in a volume ratio of 1: 1, and dissolving 1 mol / L of lithium hexafluorophosphate in this solution was used. Impregnation of the electrolyte solution was performed by immersing the separator 32 and the electrode 31 in the electrolyte solution for 10 seconds.

Charge and discharge were performed using the produced coin battery. As a result, the initial charge capacity was 2900 mAh / g, the initial discharge capacity was 2300 mAh / g, and the irreversible retention capacity was 600 mAh / g.

(Example 2)

A negative electrode active material film was formed on the current collector 1 in almost the same manner as in Example 1 except that 180 g of Si and 19.5 g of Fe were mixed to form an evaporation raw material (2). That is, the molar ratio of Fe / (Si + Fe) of the evaporation raw material 2 was about 0.053. On the other hand, it is about 5.3 mol% as molar composition expressed by a percentage.

The thickness of the obtained film was 28 micrometers, and the film formation speed was 31 nm / sec from this. When the composition of the obtained film was analyzed by the same method as in Example 1, SiFe was _0.024 O _0.63 and the molar ratio of Fe / (Si + Fe) in the film was about 0.023. As in Example 1, the surface resistivity was measured and found to be 1.7E + 6Ω / □.

When the coin battery was produced and charged and discharged in the same manner as in Example 1, the initial charge capacity was 2790 mAh / g, the initial discharge capacity was 2070 mAh / g, and the irreversible retention capacity was 720 mAh / g.

(Example 3)

Almost as in Example 1, except that metal Si (part # 441) manufactured by Osaka Asahi Co., Ltd. containing a small amount of Fe was broken to a size of about 1 cm, into a lump shape, and used as a 200 g-based evaporation raw material (2). To form a negative electrode active material film on the current collector 1. As a result of analyzing the metal Si which is the evaporation raw material 2 by ICP emission spectroscopy, the amount of Fe was 0.39 mass%. That is, the molar ratio of Fe / (Si + Fe) of the evaporation raw material 2 was about 0.0020. The molar composition expressed in percentage is about 0.2 mol%.

The thickness of the obtained film was 23 micrometers, and the film formation speed was 25 nm / sec from this. When the composition of the obtained film was analyzed by fluorescence X-ray analysis, the molar ratio of Fe / (Si + Fe) in the film was about 0.00022. In addition, there is no substantial difference between the molar ratio calculated by fluorescence X-ray analysis and the molar ratio calculated by ICP emission spectroscopy.

As in Example 1, the surface resistivity was measured and found to be 1.0E + 9Ω / □.

When the coin battery was produced and charged and discharged in the same manner as in Example 1, the initial charge capacity was 2980 mAh / g, the initial discharge capacity was 2200 mAh / g, and the irreversible retention capacity was 780 mAh / g.

(Example 4)

A negative electrode active material film was formed on the current collector 1 in almost the same manner as in Example 1 except that 199.8 g of Si and 0.2 g of Fe were mixed to form an evaporation raw material (2). That is, the molar ratio of Fe / (Si + Fe) of the evaporation raw material 2 was about 0.00050.

The thickness of the obtained film was 23 micrometers, and the film-forming rate was 26 nm / sec from this. When the composition of the obtained film | membrane was analyzed by the method similar to Example 1, Fe was less than 0.002 mass% which is a lower limit of detection, and the molar ratio of Fe / (Si + Fe) was less than 0.00001. Therefore, the film composition was SiO _0.853 . As in Example 1, the surface resistivity was measured, and found to be 6.7E + 8Ω / □.

When the coin battery was produced and charged and discharged in the same manner as in Example 1, the initial charge capacity was 2900 mAh / g, the first discharge capacity was 2200 mAh / g, and the irreversible retention capacity was 700 mAh / g.

(Example 5)

A negative electrode active material film was formed on the current collector 1 in almost the same manner as in Example 1 except that 196.06 g of Si and 3.94 g of Fe were mixed to form an evaporation raw material (2). That is, the molar ratio of Fe / (Si + Fe) of the evaporation raw material 2 was about 0.010.

The thickness of the obtained film was 23 micrometers, and the film-forming rate was 26 nm / sec from this. When the composition of the obtained film was analyzed by the same method as in Example 1, SiFe was _0.0041 O _0.809 and the molar ratio of Fe / (Si + Fe) in the film was about 0.0041. The surface resistivity was measured in the same manner as in Example 1, and found to be 3.4E + 8Ω / □.

When the coin battery was produced and charged and discharged in the same manner as in Example 1, the initial charge capacity was 2930 mAh / g, the initial discharge capacity was 2150 mAh / g, and the irreversible retention capacity was 780 mAh / g.

(Example 6)

A negative electrode active material film was formed on the current collector 1 in almost the same manner as in Example 1 except that 163.8 g of Si and 36.2 g of Fe were mixed to form an evaporation raw material (2). That is, the molar ratio of Fe / (Si + Fe) of the evaporation raw material 2 was about 0.10.

The thickness of the obtained film was 23 micrometers, and the film-forming rate was 26 nm / sec from this. When the composition of the obtained film was analyzed in the same manner as in Example 1, SiFe was _0.054 O _0.805 and the molar ratio of Fe / (Si + Fe) in the film was about 0.051. The surface resistivity was measured in the same manner as in Example 1, and found to be less than 1.0E + 5Ω / □.

When the coin battery was produced and charged and discharged in the same manner as in Example 1, the initial charge capacity was 2680 mAh / g, the initial discharge capacity was 2080 mAh / g, and the irreversible retention capacity was 600 mAh / g.

(Comparative Example 1)

A negative electrode active material film was formed on the current collector 1 in the same manner as in Example 1 except that only 200 g of Si was used as the evaporation raw material 2. As a result of analyzing the evaporation raw material 2 by the fluorescent X-ray spectroscopy, the amount of Fe was less than 0.001 mass% which is a lower limit of detection, and the molar ratio of Fe / (Si + Fe) of the evaporation raw material 2 was less than 0.000005.

The thickness of the obtained film was 22 micrometers, and the film-forming speed | rate was 24 nm / sec from this. When the composition of the obtained film was analyzed by fluorescence X-ray analysis, Fe was less than 0.001 mass%, the detection limit value, and the molar ratio of Fe / (Si + Fe) in the film was less than 0.000005. As in Example 1, the surface resistivity was measured and found to be 1.0E + 9Ω / □.

When the coin battery was produced and charged and discharged in the same manner as in Example 1, the initial charge capacity was 2900 mAh / g, the initial discharge capacity was 2300 mAh / g, and the irreversible retention capacity was 600 mAh / g.

(Comparative Example 2)

A negative electrode active material film was formed on the current collector 1 in almost the same manner as in Example 1 except that 133.4 g of Si and 66.6 g of Fe were mixed to form an evaporation raw material (2). That is, the molar ratio of Fe / (Si + Fe) of the evaporation raw material 2 was about 0.20.

The thickness of the obtained film was 16 micrometers, and the film-forming speed | rate was 18 nm / sec from this. By analyzing the resultant film composition as that of Example 1, the same method, SiFe _0.827 O _0.19 and, a molar ratio of the negative electrode active material film, Fe / (Si + Fe) was about 0.16. The surface resistivity was measured in the same manner as in Example 1, and found to be less than 1.0E + 5Ω / □.

When the coin battery was produced and charged and discharged in the same manner as in Example 1, the initial charge capacity was 2080 mAh / g, the initial discharge capacity was 1520 mAh / g, and the irreversible retention capacity was 560 mAh / g.

The molar ratio of Fe / (Si + Fe) of the evaporation raw material 2 used in the Example and the comparative example, the film-forming rate, and the molar ratio of Fe / (Si + Fe) of the obtained negative electrode active material film (that is, y / (1 + y) value). ) And the surface resistivity are shown in Table 1, and the first charge capacity, the first discharge capacity, and the irreversible retention capacity are shown in Table 2. In Tables 1 and 2, the molar ratios of Fe / (Si + Fe) of the evaporation raw materials are listed in order from the examples.

As can be seen from Table 1, iron is not contained by adding a trace amount of iron to the evaporation raw material so that the molar ratio of Fe / (Si + Fe) is within a range from 0.0005 to 0.15 (Examples 1 to 6). It can be seen that the film formation rate is improved and the surface resistivity is equal to or lower than that of Comparative Example 1 using a non-evaporated raw material or Comparative Example 2 in which more iron was added in the molar ratio than 0.15.

As can be seen from Table 2, when the value of y / (1 + y) in the obtained SiFe _y O _x film is 0.0001 or more and 0.03 or less (Examples 1 to 3 and 5), the initial charge capacity and The initial discharge capacity achieves substantially the same level as compared with the case where the y value is 0 (below the detection lower limit value). In other words, if the y value is in the above range, the high-level charge / discharge capacity can be retained while achieving the above-mentioned improvement in the film formation speed.

In all the examples, the molar ratio of Fe / (Si + Fe) in the negative electrode active material film is lower than the molar ratio of Fe / (Si + Fe) in the evaporation raw material. This tendency is more remarkable in the example where the molar ratio of Fe / (Si + Fe) is low.

The lithium battery electrode according to the present invention is useful in a lithium secondary battery requiring a high capacity. The shape is not particularly limited and can be applied to various types of lithium batteries, such as the coin type and the cylindrical shape used in the examples.

Claims (8)

Preparing a evaporation raw material containing Si and Fe in a molar ratio of Fe / (Si + Fe) in a range of 0.0005 or more and 0.15 or less, Dissolving and evaporating the evaporation raw material and depositing it directly or on an underlying layer on the current collector Method for producing a lithium battery electrode comprising a. The method of claim 1, The molar ratio of Fe / (Si + Fe) in the evaporation raw material is 0.0005 or more and 0.06 or less. The method of claim 2, The molar ratio of Fe / (Si + Fe) in the said evaporation raw material is 0.01 to 0.06 or less, The manufacturing method of the electrode for lithium batteries. The method of claim 1, The manufacturing method of the electrode for lithium batteries which performs the said vapor deposition process in oxygen atmosphere. With the whole house, A negative electrode active material film composed of SiFe _y O _x (0 <x <2 and 0.0001 ≦ y / (1 + y) ≦ 0.03), which is directly stacked on the current collector with an underlying layer interposed therebetween. Lithium battery electrode comprising a. The method of claim 5, wherein The lithium battery electrode whose value of y / (1 + y) is 0.001 or more and 0.03 or less. The negative electrode which consists of an electrode for lithium batteries of Claim 5 or 6, An anode provided to face the cathode; A separator provided between the cathode and the anode Lithium battery having a. A step of preparing an evaporation raw material containing Si and Fe in a molar ratio of Fe / (Si + Fe) within a range from 0.0005 to 0.15, Dissolving and evaporating the evaporation raw material, and manufacturing a cathode by depositing the evaporation material directly on a current collector or with an underlying layer interposed therebetween; The process of preparing a separator, Preparing the anode, Installing the separator between the cathode and the anode Method for producing a lithium battery comprising a.

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