JP2002373647A - Electrode for lithium secondary battery and the lithium secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode for lithium secondary battery of high discharge capacity and superior charging and discharging cycle characteristics, and to provide a lithium secondary battery using the electrode. SOLUTION: In this electrode for lithium secondary battery, comprising a thin film formed of an active material on a current collector, an alloy thin film (Sn-Co or the like) formed of a metal alloyed with lithium (Sn or the like), a metal which is not alloyed with lithium (Co or the like) is provided on the current collector, such as copper foil or the like, and the metal alloyed with lithium and the metal not alloyed with lithium are preferably in the relation of not forming an intermetallic compound.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel electrode for a lithium secondary battery and a lithium secondary battery using the same.

[0002]

2. Description of the Related Art In recent years, a lithium secondary battery, which has been actively researched and developed, has a charge / discharge voltage,
Battery characteristics such as charge-discharge cycle life characteristics and storage characteristics are greatly affected. For this reason, the battery characteristics have been improved by improving the electrode active material.

[0003] When lithium metal is used as the negative electrode active material, a battery having a high energy density per weight and per volume can be formed. However, there is a problem that lithium is deposited in a dendrite shape during charging and causes an internal short circuit. Was.

On the other hand, lithium secondary batteries using aluminum, silicon, tin, or the like, which electrochemically alloys with lithium during charging, as an electrode have been reported (Sol).
id State Ionics, 113-115, p57 (1998)).

[0005]

However, when these metals which are alloyed with lithium (Li) are used as the negative electrode material, large volume expansion and contraction occur with the occlusion and release of lithium, and the electrode active material is finely divided. And it is desorbed from the current collector, so that there is a problem that sufficient cycle characteristics cannot be obtained.

An object of the present invention is to solve these conventional problems and to provide a lithium secondary battery electrode having a high discharge capacity and excellent cycle characteristics, and a lithium secondary battery using the same. .

[0007]

An electrode for a lithium secondary battery according to the present invention is characterized in that an alloy thin film made of a metal alloying with lithium and a metal not alloying with lithium is provided on a current collector. And

In the present invention, the metal that can be alloyed with lithium is a metal that forms an alloy with lithium, such as a solid solution or an intermetallic compound. Specifically, Sn, Ge, A
1, In, Mg, Si and the like.

In the present invention, the metal which is not alloyed with lithium is a metal which does not form an alloy such as a solid solution or an intermetallic compound with lithium, and specifically, does not have an alloy state in a binary phase diagram with lithium. Metal. Examples of the metal that is not alloyed with lithium include Cu, F
e, Ni, Co, Mo, W, Ta, Mn and the like.

In the present invention, the metal that does not alloy with lithium is preferably a metal that forms an intermetallic compound with the metal that alloys with lithium. Here, the intermetallic compound refers to a compound having a specific crystal structure in which metals are combined at a specific ratio. In the present invention, when the metal that forms an alloy with lithium is Sn, the metal that does not form an alloy with lithium is preferably a metal that forms an intermetallic compound with Sn. Such metals include, for example, T
At least one selected from i, Mn, Fe, Ni, Co, Cu, Zr and Mo is exemplified. These metals may be contained alone or in combination. Among these, at least one selected from Fe, Co and Ni is particularly preferable, and it is particularly preferable that at least Co is contained. In the present invention, the alloy thin film made of these metals does not necessarily need to form an intermetallic compound of these metals in the thin film. Therefore, the alloy thin film does not need to be crystalline, and may be, for example, an amorphous or nonstoichiometric compound.

In the present invention, a thin film of an alloy composed of a metal alloying with lithium and a metal not alloying with lithium is provided on the current collector. The method for forming the alloy thin film is not particularly limited, but an electrochemical method such as electrolytic plating or electroless plating is preferably used. Further, the alloy thin film may be formed by a physical thin film forming method such as a CVD method, a sputtering method, a vacuum evaporation method, and a thermal spraying method.

The current collector used in the present invention is not particularly limited as long as it can be used for an electrode for a lithium secondary battery. For example, copper, nickel, titanium, iron, stainless steel, A metal foil made of molybdenum, cobalt, chromium, tungsten, tantalum, silver, or the like can be used.

In the present invention, it is preferable that unevenness is formed on the surface of the current collector. Current collector surface roughness Ra
Is not particularly limited, but the surface roughness R
Those having a of more than 2 μm are generally difficult to obtain as a copper foil having a practical thickness as a battery. Therefore, the upper limit of the preferable range of the surface roughness Ra is 2 μm or less, more preferably 1 μm or less. The lower limit of the surface roughness Ra is preferably 0.01 μm or more. Therefore, the preferable range of the surface roughness Ra is 0.01 to 2 μm.
And more preferably 0.01 to 1 μm.

The surface roughness Ra is measured according to Japanese Industrial Standard (JIS).
B 0601-1994) and can be measured, for example, by a surface roughness meter. When a copper foil having a large surface roughness Ra is used as the current collector, it is preferable to use an electrolytic copper foil.

In the present invention, the alloy thin film is preferably separated into islands by cuts formed in the thickness direction. Since the alloy thin film is separated into islands in a state of being in close contact with the current collector, the charge / discharge cycle characteristics can be significantly improved.

Since the alloy thin film contains a metal alloying with lithium, lithium can be alloyed and occluded during a charge / discharge reaction. For example, when the electrode of the present invention is used as a negative electrode, lithium is occluded in the alloy thin film during charging, and lithium is released from the alloy thin film during discharging. The volume of the alloy thin film expands and contracts due to such occlusion and release of lithium. Since the alloy thin film is separated into islands, a space is provided around it, so even if the alloy thin film expands and contracts during the charge / discharge reaction, the volume change is absorbed by the surrounding space. can do. Therefore, it is possible to prevent the alloy thin film from being pulverized and peeling off from the current collector without causing distortion inside the alloy thin film.

When an alloy thin film is formed on a current collector by a plating method or a physical thin film forming method, an alloy thin film is formed as a continuous thin film. In such a case, the cut in the thickness direction is usually formed by a charge / discharge reaction after the first time. That is, when the alloy thin film expands and contracts in the charge / discharge reaction, the above-described cut in the thickness direction is formed, and the alloy thin film is separated into islands. Such separation due to a cut in the thickness direction is easily formed particularly when a current collector having irregularities on the surface is used. When an alloy thin film is formed on a current collector having unevenness on the surface, an uneven shape is formed on the surface of the alloy thin film along the unevenness of the current collector surface. When such an alloy thin film expands and contracts, a cut is formed in the thickness direction by a line connecting the concave and convex valleys on the surface of the alloy thin film and the concave and convex valleys on the current collector surface. It is considered that the alloy thin film is separated into islands along.

In the present invention, the amount of metal that does not alloy with lithium in the alloy thin film is 50 in terms of molar ratio (atomic ratio).
% Is preferable. If more than this,
Since the amount of metal alloyed with lithium is relatively reduced, the charge / discharge capacity is undesirably reduced.
The amount of the metal that does not alloy with lithium is preferably 0.1% or more as a molar ratio (atomic ratio) in the alloy thin film. By including a metal that does not alloy with lithium, the expansion and contraction of the volume during the charge / discharge reaction of the alloy thin film can be limited, and as a result, the charge / discharge cycle characteristics can be improved. Therefore, from the viewpoint of improving the cycle characteristics, the metal that does not alloy with lithium is 0.1%.
Preferably, it is contained at 1% or more. Therefore, the preferable range of the content of the metal that does not alloy with lithium in the alloy thin film is 0.1 to 50 as a molar ratio (weight ratio).
%. A more preferable content range is 1 to 40% as a molar ratio (atomic ratio).

In the present invention, a mixed layer of a current collector component and an alloy component may be formed at the interface between the current collector and the alloy thin film. By forming such a mixed layer, the adhesion of the alloy thin film to the current collector can be increased, and further improvement in cycle characteristics can be expected. Such a mixed layer can be formed by forming a thin alloy film on the current collector and then performing a heat treatment or the like. The temperature of the heat treatment is preferably lower than the melting point of the alloy thin film and the melting point of the current collector.

The lithium secondary battery of the present invention is characterized by comprising a negative electrode comprising the above-mentioned electrode for a lithium secondary battery of the present invention, a positive electrode, and a non-aqueous electrolyte. Solvent of the electrolyte used in the lithium secondary battery of the present invention is not particularly limited, and ethylene carbonate, propylene carbonate, butylene carbonate, cyclic carbonate such as vinylene carbonate, and dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate and the like And a mixed solvent with a linear carbonate. Further, a mixed solvent of the cyclic carbonate and an ether solvent such as 1,2-dimethoxyethane and 1,2-diethoxyethane is also exemplified. The solutes of the electrolyte include LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN
(CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (C
F ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), LiC (CF ₃ SO ₂ ) ₃ , Li
C (C ₂ F ₅ SO ₂ ) _{3 and the} like and mixtures thereof are exemplified. Further, examples of the electrolyte include a gel polymer electrolyte in which a polymer electrolyte such as polyethylene oxide and polyacrylonitrile is impregnated with an electrolyte, and an inorganic solid electrolyte such as LiI and Li ₃ N. The electrolyte of the lithium secondary battery of the present invention is not limited, as long as the Li compound as a solute that develops ionic conductivity and the solvent that dissolves and retains the Li compound are not decomposed at the time of charging, discharging, or storing the battery. Can be used.

As the positive electrode active material of the lithium secondary battery of the present invention, LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , L
iMnO ₂ , LiCo _0.5 Ni _0.5 O ₂ , LiNi _0.7 Co
Lithium-containing transition metal oxides such as _0.2 Mn _0.1 O ₂ ,
A metal oxide containing no lithium such as MnO ₂ is exemplified. In addition, any other substance capable of electrochemically inserting and removing lithium can be used without limitation.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in more detail with reference to examples. However, the present invention is not limited to the following examples, and may be appropriately modified within the scope of the invention. It can be implemented by

(Experiment 1) [Preparation of Electrode] Electrolytic copper foil having a thickness of 18 μm (surface roughness Ra)
= 0.188 μm) and a thickness of 2
A thin film made of a Sn-Co alloy having a thickness of μm was formed. Plating baths include tin chloride, cobalt chloride, sodium chloride,
A plating bath in which hydrochloric acid, ethylene glycol, and thiourea were mixed was used.

After forming the Sn—Co alloy thin film, 2 cm
It was cut into a size of × 2 cm to obtain an electrode a1. As a comparison, an alloy powder of Sn and Co (molar ratio: 8: 2) produced by an atomizing method and a fluororesin (PVdF) were mixed at 95:
A slurry mixed at a weight ratio of 5 was prepared, and the slurry was applied on an electrolytic copper foil and dried, and then cut into a size of 2 cm × 2 cm to obtain an electrode b1.

[Preparation of Electrolyte Solution] L was added to a mixed solvent of ethylene carbonate and diethyl carbonate at a volume ratio of 1: 1.
An electrolyte was prepared by dissolving iPF ₆ at 1 mol / liter.

[Preparation of Beaker Cell] Using the electrodes a1 and b1 as working electrodes, a beaker cell as shown in FIG. 3 was prepared. As shown in FIG. 3, the beaker cell is configured by immersing the counter electrode 3, the working electrode 4, and the reference electrode 5 in the electrolytic solution contained in the container 1. As the electrolytic solution 2, the above-mentioned electrolytic solution was used, and the counter electrode 3 and the reference electrode 5 were used.
Used lithium metal.

[Measurement of Cycle Characteristics] Each of the beaker cells produced as described above was placed at 25 ° C. for 0.2 m.
A, a constant current charge is performed to 0 V (vs. Li ^/ Li ⁺ ), and then a constant current discharge is performed at 0.2 mA to 2 V (vs. Li ^/ Li ⁺ ). Was performed, and the charge capacity and the discharge capacity per unit active material weight in each cycle were measured, and the initial efficiency and the capacity retention rate defined by the following equations were obtained. Table 1 shows the results. Here, the reduction of the working electrode is defined as charging, and the oxidation of the working electrode is defined as discharging.

Initial efficiency (%) = (discharge capacity at 1st cycle / charge capacity at 1st cycle) × 100 Capacity retention rate (%) = (discharge capacity at 10th cycle / discharge capacity at 1st cycle) × 100

[0029]

[Table 1]

As is clear from the results shown in Table 1, the electrode a1 according to the present invention has a higher charge / discharge capacity than the comparative electrode b1 and shows good cycle characteristics.

(Experiment 2) Using the electrodes a1 and b1 obtained in Experiment 1 as a negative electrode, a lithium secondary battery was fabricated and its charge / discharge cycle characteristics were evaluated.

[Preparation of positive electrode] LiC having an average particle size of 10 μm
85% by weight of oO ₂ powder and carbon powder 10 as a conductive agent
% By weight and polyvinylidene fluoride powder 5 as a binder
% By weight, and N-methylpyrrolidone was added to the resulting mixture and kneaded to prepare a slurry. This slurry was applied to one surface of a 20-μm-thick aluminum foil by a doctor blade method and dried, and then cut into a size of 2 cm × 2 cm to produce a positive electrode.

[Preparation of Battery] The positive electrode obtained as described above and the electrode a1 or b1 were bonded together via a polyethylene microporous membrane, and inserted into an outer package made of an aluminum laminate material. 500 μl of the same electrolytic solution as that prepared in Experiment 1 was injected into this to prepare a lithium secondary battery.

FIG. 4 is a plan view showing the manufactured lithium secondary battery. As shown in FIG. 4, a positive electrode 11 and a negative electrode 13 are combined and inserted into an exterior body 14 via a separator 12 made of a polyethylene microporous membrane. After being inserted into the outer package 14, an electrolytic solution is injected and sealed with the sealing portion 14a of the outer package 14, whereby a lithium secondary battery is manufactured.

FIG. 5 is a cross-sectional view showing a combination of electrodes inside the battery. As shown in FIG.
The positive electrode 11 and the negative electrode 13 are combined so as to face each other with the separator 12 interposed therebetween. In the positive electrode 11, a positive electrode active material layer 11 a is provided on a positive electrode current collector 11 b made of aluminum, and the positive electrode active material layer 11 a is in contact with the separator 12. In the negative electrode 13, a negative electrode active material layer 13 a is provided on a negative electrode current collector 13 b made of copper, and the negative electrode active material layer 13 a is in contact with the separator 12. In the present embodiment, the negative electrode active material layer 13a is a layer formed from a Sn—Co alloy thin film.

As shown in FIG. 4, a positive electrode tab 11c made of aluminum for taking out from the outside is attached to the positive electrode current collector 11b. Further, the negative electrode current collector 13
A negative electrode tab 13c made of nickel for external extraction is also attached to b.

In the manufactured lithium secondary battery, a battery using the electrode a1 as a negative electrode was referred to as a battery A1, and a battery using the electrode b1 was referred to as a battery B1. The design capacity of each battery is 6m
Ah.

[Charge / Discharge Test] A charge / discharge test was performed on the batteries A1 and B1 produced as described above. Charging was performed with a constant current of 1.2 mA until the charging capacity reached 6 mAh, and discharging was performed with a constant current of 1.2 mA up to 2.0 V, which was one cycle. However, the first cycle (first time)
Was charged until the charging capacity reached 7.2 mAh. In the same manner as in Experiment 1, the initial efficiency and the capacity retention were determined. Table 2 shows the results. The measurement was performed at 25 ° C.

[0039]

[Table 2]

As is clear from the results shown in Table 2, the battery A1 according to the present invention shows good charge / discharge cycle characteristics. FIG. 1 is a scanning electron microscope photograph when the surface of the electrode a1 taken out of the battery A1 at the tenth cycle in the charge / discharge test is observed. The magnification is 1000 times. FIG. 2 is a scanning electron micrograph when the electrode a1 is embedded in a resin, sliced, and a cross section is observed. The magnification is 5000 times. As is clear from FIGS. 1 and 2, in the electrode a1 after the charge / discharge reaction, it can be seen that the alloy thin film is separated into islands by the cut formed in the thickness direction of the alloy thin film. As is clear from FIG. 2, the cut is formed along the valley of the unevenness on the surface of the current collector. Also, as is clear from FIG.
It can be seen that these cuts are connected in a network along the valleys of the irregularities on the current collector surface in the direction of the film surface of the alloy thin film.

As is apparent from FIG. 2, the alloy thin film is formed along the irregularities on the current collector surface, and a line connecting the concave and convex valleys on the surface of the alloy thin film and the irregularities on the current collector surface. A cut is formed along the line. It is considered that such a cut was formed by the expansion and contraction of the alloy thin film due to the charge / discharge reaction.

As shown in FIGS. 1 and 2, since a space exists around the island-shaped alloy thin film, such a space can absorb a change in volume at the time of charge / discharge reaction of the alloy thin film. It seems that good cycle characteristics can be exhibited.

In the above embodiment, the Sn--Co alloy thin film is formed on the current collector substrate by electrolytic plating, but may be formed by electroless plating. Moreover,
It may be formed by a thin film forming method such as a sputtering method, a vacuum evaporation method, and a thermal spraying method.

(Experiment 3) In the same manner as in Experiment 1, the thickness 18
2 μm thick Sn—Ni alloy, Sn—Fe alloy, Sn—Pb alloy, and Sn—Zn on an electrolytic copper foil of μm (surface roughness Ra = 0.188 μm) by electrolytic plating.
A thin film made of an alloy was formed.

The Sn—Ni alloy thin film is made of Sn mixed with potassium pyrophosphate, tin chloride, nickel chloride and glycine.
-Formed using a Ni plating bath. The Sn—Fe alloy thin film was formed using a Sn—Fe plating bath in which tin chloride, iron sulfate, sodium citrate, and L-ascorbic acid were mixed. Note that two types of plating baths having different compositions were used for the Sn—Fe plating bath.

The Sn—Pb alloy thin film was formed using an Sn—Pb plating bath in which tin borofluoride, lead borofluoride, borofluoric acid, boric acid, and peptone were mixed. Sn-Z
The n-alloy thin film was formed using a Sn—Zn plating bath in which an organic acid tin, an organic acid zinc, and a complexing agent were mixed.

The electrode formed with the Sn—Ni alloy thin film is referred to as electrode c1 of the present invention, the electrodes formed with the Sn—Fe alloy thin film are referred to as electrodes c2 and c3 of the present invention, and the electrode formed with the Sn—Pb alloy thin film is referred to as comparative electrode e1. The electrode on which the Sn—Zn alloy thin film was formed was used as a comparative electrode e2. Note that Ni and F
e is a metal that does not alloy with lithium, and Sn, P
b and Zn are metals that alloy with lithium. Therefore, the Sn—Ni alloy thin film and the Sn—Fe alloy thin film are the alloy thin films according to the present invention, and the Sn—Pb alloy thin film and S
The n-Zn alloy thin film is an alloy thin film outside the scope of the present invention.

The composition ratio of the alloy in the alloy thin films formed on the electrodes c1 to c3 of the present invention and the comparative electrodes e1 and e2 was analyzed by ICP emission spectroscopy. Table 3 shows the composition ratio of the alloy thin film. In Table 3, in Experiment 1
3 also shows the composition ratio of the alloy thin film in the electrode a1 of the present invention prepared in the above.

[0049]

[Table 3]

The electrodes c1 to c3 of the present invention and the comparative electrode e1
Using e and e2 as working electrodes, a beaker cell was prepared in the same manner as in Experiment 1, and the cycle characteristics were evaluated. Table 4 shows the evaluation results.

[0051]

[Table 4]

As is clear from the results shown in Table 4, the electrodes c1 to c3 of the present invention show better cycle characteristics than the comparative electrodes e1 and e2.

(Experiment 4) A thin film made of a 2 μm thick Sn—Co alloy was formed on an electrolytic copper foil in the same manner as in Experiment 1 using two types of electrolytic copper foils (18 μm in thickness) having different surface roughnesses Ra. Was formed to produce an electrode.

An electrode using an electrolytic copper foil having a surface roughness Ra of 0.188 μm is referred to as electrode d1 of the present invention, and an electrode using an electrolytic copper foil having a surface roughness Ra of 1.19 μm is referred to as an electrode d2 of the present invention.
And In addition, a thin film made of a Sn—Co alloy having a thickness of 2 μm was similarly formed on a rolled copper foil having a surface roughness Ra of 0.04 μm to obtain an electrode d3 of the present invention. The electrode d1 of the present invention is the same as the electrode a1 shown in Table 1.

Using the electrodes d1, d2, and d3 of the present invention, a beaker cell was prepared in the same manner as in Experiment 1, and the charge / discharge cycle characteristics were evaluated. The evaluation results are shown in Table 5.

[0056]

[Table 5]

As is clear from the results shown in Table 5, good cycle characteristics can be obtained when the surface roughness Ra of the current collector exceeds 1 μm, but the surface roughness Ra of the current collector is 1 μm or less. It turns out to be preferable. In addition, the electrode d1 of the present invention has better cycle characteristics than the electrode d3 of the present invention. Therefore, the surface roughness Ra of the current collector is set to 0.1.
It turns out that the range of 1-1 micrometer is especially preferable.

(Experiment 5) In the same manner as in Experiment 1, the thickness 18
A 2 μm thick Sn—Ni—C layer was formed on a 2 μm electrolytic copper foil (surface roughness Ra = 0.188 μm) by electrolytic plating.
An o-alloy thin film was formed.

The Sn—Ni—Co alloy thin film was formed using a Sn—Ni—Co plating bath in which potassium pyrophosphate, tin chloride, nickel chloride, and cobalt chloride were mixed. Using the obtained electrode f1 of the present invention, a beaker cell was prepared in the same manner as in Experiment 1, and the cycle characteristics were evaluated. Table 6 shows the evaluation results. Table 7 shows the chemical composition of the plating film formed on the electrode.

[0060]

[Table 6]

[0061]

[Table 7]

As is clear from the results shown in Table 6, Sn
The electrode f1 on which the -Ni-Co alloy thin film is formed has a high charge / discharge capacity and shows better cycle characteristics than the electrode c1 using the Sn-Ni alloy thin film.

[0063]

According to the present invention, a lithium secondary battery having a high discharge capacity and excellent cycle characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is a scanning electron micrograph showing the surface of an electrode a1 of an example according to the present invention.

FIG. 2 is a scanning electron micrograph showing a cross section of an electrode a1 of an example according to the present invention.

FIG. 3 is a schematic cross-sectional view showing a beaker cell manufactured in an example.

FIG. 4 is a plan view showing a lithium secondary battery manufactured in an example.

5 is a cross-sectional view showing a combination structure of electrodes in the lithium secondary battery shown in FIG.

[Description of Signs] 1 ... Container 2 ... Electrolyte 3 ... Counter electrode 4 ... Working electrode 5 ... Reference electrode 11 ... Positive electrode 11a ... Positive electrode active material layer 11b ... Positive electrode current collector 11c ... Positive electrode tab 12 ... Separator 13 ... Negative electrode 13a ... Negative electrode active material layer 13b Negative electrode current collector 13c Negative electrode tab 14 External member 14a Sealing portion of external member

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Daizo Chito 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Inventor Ryuji Oshita 2 Keihanhondori, Moriguchi-shi, Osaka 5-5-5 Sanyo Electric Co., Ltd. (72) Inventor Masahisa Fujimoto 2-5-5 Sanyo Electric Co., Ltd., Sanyo Electric Co., Ltd. (72) Inventor Shin Fujiya Keihanmoto, Moriguchi, Osaka 2-5-5, Sanyo Electric Co., Ltd. (72) Inventor Maruo Jinno 2-5-5, Keihanhondori, Moriguchi-shi, Osaka F-term in Sanyo Electric Co., Ltd. 5H017 AA03 AS02 CC01 DD01 EE01 HH03 5H029 AJ03 AJ05 AK02 AK03 AL11 AM00 AM03 AM04 AM05 AM07 AM12 AM16 CJ24 DJ07 DJ12 DJ14 EJ01 HJ03 5H050 AA07 AA08 BA17 CA02 CA08 CA09 CB11 DA07 FA12 FA15 FA18 GA24 HA03

Claims (18)

[Claims] 1. An electrode for a lithium secondary battery, wherein an alloy thin film made of a metal alloying with lithium and a metal not alloying with lithium is provided on a current collector. 2. The electrode for a lithium secondary battery according to claim 1, wherein the metal that does not alloy with lithium is a metal that forms an intermetallic compound with a metal that alloys with lithium. 3. The electrode for a lithium secondary battery according to claim 1, wherein the alloy thin film is formed by plating. 4. The electrode for a lithium secondary battery according to claim 1, wherein the alloy thin film is separated into islands by cuts formed in a thickness direction. 5. The electrode for a lithium secondary battery according to claim 4, wherein the cut is formed by charge / discharge after the first time. 6. The method according to claim 4, wherein irregularities are formed on the surface of the current collector, and the alloy thin film is separated into islands along valleys of the irregularities. Electrodes for lithium secondary batteries. 7. The current collector having a surface roughness Ra of 0.01 to 0.01.
The electrode for a lithium secondary battery according to claim 1, wherein the thickness is 2 μm. 8. The current collector having a surface roughness Ra of 0.01 to 0.01.
The electrode for a lithium secondary battery according to claim 1, wherein the thickness is 1 μm. 9. The current collector has a surface roughness Ra of 0.1-1.
7. The method according to claim 1, wherein the thickness is μm.
Item 8. The electrode for a lithium secondary battery according to item 1. 10. The electrode for a lithium secondary battery according to claim 1, wherein the current collector is made of copper. 11. The electrode for a lithium secondary battery according to claim 1, wherein the current collector is an electrolytic copper foil. 12. The metal which is alloyed with lithium is Sn, and the metal which is not alloyed with lithium is a metal which forms an intermetallic compound with Sn.
The electrode for a lithium secondary battery according to any one of the above. 13. The lithium according to claim 12, wherein the metal that forms an alloy with lithium is Sn, and the metal that does not form an alloy with lithium is at least one selected from Fe, Co, and Ni. Electrodes for secondary batteries. 14. A metal alloying with lithium is Sn, and at least Co is used as a metal not alloying with lithium.
The electrode for a lithium secondary battery according to any one of claims 1 to 12, further comprising: 15. The lithium according to claim 14, wherein the metal that alloys with lithium is Sn, the metal that does not alloy with lithium is Co, and the alloy thin film is a Sn—Co alloy thin film. Electrodes for secondary batteries. 16. The metal alloying with lithium is Sn, the metal not alloying with lithium is Ni and Co, and the alloy thin film is a Sn—Ni—Co alloy thin film. 4. The electrode for a lithium secondary battery according to item 1. 17. An interface between the current collector and the alloy thin film,
The electrode for a lithium secondary battery according to any one of claims 1 to 16, wherein a mixed layer of a current collector component and an alloy component is formed. 18. A lithium secondary battery comprising a negative electrode comprising the electrode according to claim 1, a positive electrode, and a non-aqueous electrolyte.