KR20020038917A - Anode thin film for lithium secondary battery - Google Patents

Abstract

PURPOSE: Provided is an anode thin film for lithium secondary battery equipped with current collection body and the anode active material located at its top part. The above anode thin film greatly enhances the cycle property by controlling the swelling/contracting of the silicon volume during the process of charging/discharging. When the anode thin film is used, the life of the lithium secondary battery is extended by the improvement of the chemical and mechanical stability of the interface between the electrode and the electrolyte. CONSTITUTION: The above anode thin film comprises: the anode active material which is a thin multilayer film composed of alternately piled Si layer with the thickness of 50-250 angstrom and Ag layer of 10-70 angstrom; and a buffer film with the thickness of 50-250 angstrom between the above current collection body and the cathode active material, consisting of more than one materials selected from V, Ni, Mo and Cu.

Description

Anode thin film for Lithium secondary battery

The present invention relates to a negative electrode thin film for a lithium secondary battery. More specifically, lithium 2 having improved charge and discharge cycle characteristics by using silicon (Si) and silver (Ag) as a negative electrode active material layer forming material formed on a current collector. It relates to a negative electrode thin film of a secondary battery.

Recent developments in the microelectronics industry, miniaturization of electronic devices, high performance, and miniaturized sensor devices have increased the need for ultra-small and ultra-thin batteries as a power source for driving them.

1 schematically shows the structure of a thin film battery according to the prior art.

Referring to this, the thin film battery basically has a structure in which a cathode 12, an electrolyte 14, and an anode 13 are sequentially stacked in the form of a thin film on the current collector 11. As the overall thickness is about 10 μm, it has the following advantages.

In other words, by depositing a thin film and placing an anode near the cathode, the current density is high, the battery efficiency characteristics are excellent, and the thin film is formed so that the moving distance between the ions decreases, making the movement of ions easier and faster. Can be greatly reduced. In addition, such a thin film battery is very promising as a main power source for driving ultra-small electronic devices, micro electro mechanical system (MEMS) devices and micro-sensors because it is easy to manufacture in any shape and size to meet a special purpose.

Since the thin film battery is manufactured according to the same method as that of a semiconductor manufacturing process, it can be mounted with an electronic circuit on a semiconductor chip to implement a complementary metal oxide semiconductor (CMOS) memory chip which is used as a back-up power supply. Can be. In addition, it is possible to maximize the space utilization efficiency by minimizing the unused space of the electronic device, and can be implemented as a battery having a variety of voltages and capacities through a series and parallel connection through a proper design and etching process, the use range is very wide.

To date, research on thin film cells has been concentrated on the production and evaluation of a positive electrode thin film mainly composed of V ₂ O ₅ , LiCoO ₂ , LiMn ₂ O ₄ , and the like, and satisfactory results have been reported. As the negative electrode thin film of such a thin film battery, a lithium metal thin film formed by depositing lithium metal is mainstream.

However, since lithium metal has a low melting point of about 180 ° C., the lithium metal may be melted due to the heat generated during the soldering process accompanying the packaging process to damage the device. In addition, lithium metal has many problems in handling due to its high reactivity in the air, and requires additional installation of a separate device for isolation from moisture and oxygen. Holding it.

In addition to the lithium metal thin film described above, a negative electrode thin film composed of silicon tin oxynitride (SITON), tin oxide (SnO ₂ ), and nitride series has been attempted as a negative electrode thin film, but an irreversible reaction occurring in an initial charge / discharge cycle is controlled. I can't do it.

Meanwhile, researches on lithium alloys have been conducted to overcome the low charge and discharge efficiency of lithium, and tin (Sn), silicon (Si), or aluminum (Al) is attracting attention as a next-generation anode active material as a metal capable of alloying with lithium. . By the way, although these negative electrode active materials have excellent capacity characteristics in the low voltage range with respect to lithium, the volume change of the active material generated by the insertion and desorption of lithium during charge and discharge process generates stress at the inside and the interface of the thin film so that the structure of the negative electrode thin film Deterioration of the cycle characteristics, and in the case of a thin film battery using a solid electrolyte, in particular, the adhesive force at the interface between the electrode and the current collector is significantly lowered, thereby lowering the battery performance. Therefore, there is no capacity reduction due to irreversible reaction during the insertion or desorption of lithium in the first charge / discharge cycle, and it is a priority to develop a material having excellent cycle characteristics.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a negative electrode thin film for a lithium secondary battery having improved charge and discharge cycle characteristics by solving the above problems.

1 is a view showing a schematic structure of a conventional thin film battery,

2 is a view schematically showing the structure of a cathode employing a multilayer thin film prepared according to Example 1 of the present invention,

3 is a view comparing the cycle characteristics of the lithium secondary battery prepared according to Example 1 and Comparative Example 1 of the present invention,

4 is a view comparing cycle characteristics according to the thickness of a silicon (Si) layer of a cathode employing a multilayer cathode thin film having a structure of MSA-1, MSA-2, MSA-4 of Example 1 of the present invention,

5A is a view showing charge capacity, discharge capacity and irreversible capacity in the first cycle according to the total thickness of the silicon (Si) layer of the cathode employing a multilayer thin film prepared according to Example 1 of the present invention,

5B is a view showing charge capacity, discharge capacity and irreversible capacity in the first cycle according to the total thickness of the silver (Ag) layer of the cathode employing a multilayer thin film prepared according to Example 1 of the present invention,

6 is a view comparing cycle characteristics according to the thickness of the silver (Ag) layer of a cathode employing a multilayer anode thin film of the MSA-1 and MSA- 6 structure of Example 1 of the present invention,

7 is a graph showing the cycle characteristics of the negative electrode using a multilayer negative electrode thin film of the MSA-4 and MSA-5 structure prepared according to Example 1 of the present invention,

FIG. 8 is a graph illustrating cycle characteristics of a cathode employing a silicon-silver single layer cathode thin film prepared according to Example 2 of the present invention.

<Brief description of the main parts of the drawing>

11, 21 .... the whole house 12 ... cathode

13 .... Anode14 .... Electrolyte

15 ... protective layer

In the present invention to achieve the above technical problem,

In the negative electrode thin film for a lithium secondary battery provided with an electrical power collector and the negative electrode active material layer formed in the upper part,

The negative electrode active material layer is a multilayer thin film in which a silicon (Si) layer and a silver (Ag) layer are stacked, to provide a negative electrode thin film for a lithium secondary battery.

The present invention also provides a negative electrode thin film for a lithium secondary battery including a current collector and a negative electrode active material layer formed thereon,

The negative electrode active material layer is made of a negative electrode thin film for a lithium secondary battery, characterized in that it consists of a single layer containing silicon and silver.

The multi-layered thin film is particularly Si / Ag / Si film, Si / Ag / Si / Ag film, Si / Ag / Si / Ag / Si / Ag film, Si / Ag / Si / Ag / Si / Ag / Si / Ag film Or Ag / Si / Ag / Si / Ag / Si / Ag film.

In addition, it is preferable that the uppermost layer of the multilayer thin film is made of silver (Ag) of the negative electrode thin film of the present invention because the cycle characteristics of the lithium secondary battery employing such a negative electrode thin film are more excellent when this condition is satisfied.

In the cathode thin film of the present invention, the silicon (Si) layer and the silver (Ag) layer are preferably formed alternately, and more preferably, the silver (Ag) layer is formed between the silicon (Si) layers. .

Although silicon exhibits a large capacity in the low voltage range with respect to lithium (Li), and has many advantages as a negative electrode active material, silicon cannot be used to control active material degradation due to a large volume change generated during charging and discharging. It was. In the present invention, the negative electrode has a disadvantage, that is, to reduce the stress caused by the volume expansion of the silicon while using a lithium (Ag) acting as a medium that can move the electrons to form a negative electrode active material layer There is a characteristic. Since silver does not react with silicon, it is possible to secure the capacity and reversibility of the lithium-silicon reaction and to secure the stability of the active material structure under heating conditions required in the packaging process of the thin film battery in the future. In the lithium secondary battery employing such a negative electrode active material layer, the charge and discharge cycle characteristics are the thickness and arrangement order of each layer of silicon (Si) and silver (Ag) used as the negative electrode active material, the thickness of the overall negative electrode active material layer, Various values can be obtained by controlling the microstructure, crystallinity, size, and distribution of the respective phases by the heat treatment conditions when forming the thin film and the mixing weight ratio of silver and silicon when forming a single layer containing silver and silicon as the negative electrode active material layer.

Hereinafter, a cathode thin film according to an exemplary embodiment of the present invention will be described in more detail with reference to a-e of FIG. 2.

As shown in a-e of FIG. 2, the negative electrode thin film of the present invention is constituted by providing a current collector and a multilayer thin film in which a silicon (Si) layer and a silver (Ag) layer are stacked as a negative electrode active material layer thereon. In the negative electrode thin film of the present invention, the negative electrode current collector is not particularly limited, but usually a copper thin film, wherein the thickness of the current collector is usually 100 ~ 300 nm.

The negative electrode active material layer of FIG. 2a has a structure in which Si layers / Ag layers / Si layers / Ag layers / Si layers / Ag layers / Si / Ag layers are sequentially stacked. The active material layer of FIG. 2b has a structure in which Si layers / Ag layers / Si layers / Ag layers / Si layers / Ag layers are sequentially stacked. The negative electrode active material layer of FIG. 2c has a structure in which Si layers / Ag layers / Si layers / Ag layers are sequentially stacked. The negative electrode active material layer of FIG. 2d has a structure in which Si layers / Ag layers / Si layers are sequentially stacked. The negative electrode active material layer of e of FIG. 2 has a structure in which Ag layers / Si layers / Ag layers / Si layers / Ag layers / Si layers / Ag layers are sequentially stacked.

As shown in ae of FIG. 2, in the negative electrode active material layer of the present invention, a silicon (Si) layer and a silver (Ag) layer are alternately stacked. Particularly, when a silver layer is formed between the silicon layers, silicon (Si) is formed. It is effective because the effect of inhibiting the volume expansion of) is greater.

Since the thickness of the silicon (Si) layer and the number of stacked layers are proportional to the amount of the negative electrode active material, the thickness of the silicon (Si) layer may vary depending on the requirements of the device and the capacity of the cathode, but is preferably in the range of 50 to 250 kV. If the thickness of the silicon layer is less than 50 kHz, the number of layers of the silicon / silver multilayer thin film increases for the design of the required capacity. When the number of silver (Ag) layers increases more than a predetermined range, the overpotential of the cathode thin film is increased. There is a problem of increasing, and when the thickness of the silicon layer is larger than 250 kHz, there is a problem that the volume expansion of the silicon is not sufficiently suppressed.

In addition, silver (Ag) reacts with lithium in a low voltage section of 0.08V or less to form a stable silver-lithium (Ag-Li) alloy. In the charging process, however, the Li-Ag alloy formed on the contrary is slowly decomposed into Li and Ag, so that the reacted lithium does not escape and the reversibility decreases, thus acting as an irreversible capacity. Therefore, it is preferable to deposit silver to a minimum thickness so as to perform such a role, and to form a range of 10 ~ 70Å. If the thickness of the silver layer is less than 10Å, the effect of suppressing the volume change of the silicon layer is negligible. If the thickness of the silver layer is greater than 70 GPa, there is a problem in that the reaction rate at which the Li-Ag alloy decomposes into Li and Ag is lowered.

The silicon / silver multilayer thin film laminated on the current collector of the present invention may obtain a lithium secondary battery having various performances according to the stacking order and the stacking thickness. In the case where the uppermost layer of the multilayer thin film is a silicon layer as shown in d of FIG. 2, the battery capacity is particularly excellent, and in the case where the uppermost layer is a silver layer as shown in FIGS. This is because when the uppermost layer of the multilayer thin film is a silver layer, it acts to suppress cracking and loss of the silicon active material due to volume expansion and contraction of silicon at the interface with the electrolyte.

In addition, in the negative electrode thin film of the present invention, instead of forming a multilayer thin film in which a silicon layer and a silver layer are stacked as shown in ae of FIG. 2, silicon (Si) and silver (Ag) as shown in f of FIG. 2. It is also possible to form a single film comprising a. At this time, between the current collector and the negative electrode active material layer, it is also possible to further form a buffer film of at least one selected from the group consisting of vanadium (V), nickel (Ni), molybdenum (Mo), copper (Cu). .

In the negative electrode thin film of the present invention, the method of forming a multilayer thin film in which a silicon layer and a silver layer are laminated or a silicon and silver containing single layer is not particularly limited. Specific manufacturing methods include sputtering, electron beam deposition, ion beam assisted deposition and the like. At this time, the process conditions of each method are not particularly limited, but each of these methods will be described in detail as follows.

When deposited by the sputtering method, each component has a very fine and uniform distribution, it is possible to obtain a thin film of amorphous or nanocrystalline structure according to the degree of cooling of the substrate. In addition, by using mosaic sputtering using a mosaic-type target, or simultaneous sputtering using two or more targets, or sputtering using an alloy target, a multi-layered thin film may be manufactured according to a composition required for a simultaneous deposition method.

In the case of sputtering and depositing separate sputtering targets simultaneously, thin films of various compositions may be obtained by adjusting high frequency power applied to each target. In the case of simultaneous sputtering, different deposition conditions (deposition pressure, gas flow rate, and gas ratio) are the same, so only the high frequency power applied to each target becomes a variable to control the composition of the thin film. Typically, the deposition power of the base material (Si) remains the same and changes the deposition power of the added material. For example, in the case of silicon, the deposition power is in the range of 100 to 300W, and in the case of the metal M, in the range of 0 to 100W. In the case of the mosaic target method, the sputtering process conditions are all the same, and the number of chips is a variable of composition change.

Deposition using ion beam assisted deposition, multi-component amorphous and crystalline thin films can be formed by appropriately adjusting ion beam conditions with the effect of increasing the mobility and reactivity of atoms while colliding with the atoms deposited on the substrate. It can manufacture. The composition of the thin film can be changed by adjusting the electron beam current of the electron beam applied to each evaporation source, and the crystallinity and microstructure of the deposited thin film can be controlled by changing the flux and acceleration voltage of Ar ions.

In the electron beam deposition method, electron beams are simultaneously focused and evaporated on different deposition sources and simultaneously deposited on a substrate. At the same time, by accelerating the argon ions to the substrate it is possible to increase the mobility of the deposition atoms or to change the surface state of the thin film. The composition of the thin film can be changed by adjusting the electron flux (electron beam current) of the electron beam applied to each evaporation source, and the crystallinity and microstructure of the deposited thin film can be controlled by changing the acceleration voltage.

In the present invention, in the formation of a single layer containing silicon and silver, in particular, a method of depositing silicon (Si) and silver (Ag) by the co-sputtering method is used. As described above, when the single layer is formed by the simultaneous sputtering method, the characteristics of the finally obtained negative electrode active material layer vary slightly depending on the distribution pattern, particle size, and mixing ratio of silver distributed in the silicon. And by controlling the uniform distribution (uniform) it can be obtained the same effect as the multilayer thin film of the silicon / silver as shown in ae of FIG. In this case, the single film containing silicon (Si) and silver (Ag) is preferably composed of a mixed molar ratio of silicon (Si) and silver (Ag) of 7: 3 to 3: 7. If the amount of silver in the silicon is more than the above range, a large amount of silver is present around the silicon, which is a reactive active material with lithium, and the effect is that silicon is shielded by the surrounding silver, preventing lithium from accessing all available silicon atoms. As a result, the electrode capacity is much lower than the actual design. In addition, when the content of silver is less than the above range, there is a problem that the effect of suppressing the volume change of the silicon layer is insignificant. In addition, the thickness of the single layer may be varied according to the requirements of the device and the capacity of the cathode, and the thickness may be increased in an appropriate range if the silver may be uniformly distributed in the form of fine particles of silver between the silicon in the above composition range. Is possible.

On the other hand, the negative electrode thin film of the present invention, it is preferable to form a buffer film between the current collector and the negative electrode active material layer, as shown in a to f of FIG. The buffer film is formed using at least one metal selected from the group consisting of vanadium (V), nickel (Ni), molybdenum (Mo), and copper (Cu), and stress relaxation and interface between the negative electrode active material layer and the current collector. It plays a role to secure stability in. At this time, the thickness of the buffer film is preferably 50 to 250 kPa. If the thickness of the buffer film is less than 50 GPa, the buffering agent may not sufficiently play a buffering role such as stress relaxation between the current collector and the negative electrode active material layer as described above. There is no significant effect, but it is not preferable because it brings only the volume increase of the entire cathode thin film.

Hereinafter, the present invention will be described in detail with reference to the following examples, but the present invention is not limited only to the following examples.

Example 1

A cathode thin film having six structures as shown in Table 1 was deposited by sequentially depositing each component of the thin film using a 2 inch diameter silicon (Si), silver (Ag), and vanadium (V) target on a copper substrate. Prepared.

At the time of deposition, the initial vacuum degree was adjusted to 2 × 10 ^-6 torr or less, and then the vanadium (V) thin film was deposited to 200 Å thickness at a high frequency (rf) power of 50 W under 5 mTorr of argon gas and 10 sccm of flow rate The silver (Ag) thin film and the silicon (Si) thin film were alternately deposited on the top. At this time, the silicon thin film was deposited with a thickness of 70 ~ 200kW under the rf power of 200W, and the silver thin film was deposited with a thickness of 25 ~ 50kW between the silicon thin film under the condition of DC (270V) and 30kW.

Sample name Negative active material layer laminated structure Silicon layer thickness Silver layer thickness MSA-1 Cu / V (200Å) / Si / Ag / Si / Ag / Si / Ag / Si / Ag 70 25 MSA-2 Cu / V (200Å) / Si / Ag / Si / Ag / Si / Ag 100 25 MSA-3 Cu / V (200Å) / Ag / Si / Ag / Si / Ag / Si / Ag 100 25 MSA-4 Cu / V (200Å) / Si / Ag / Si / Ag 200 25 MSA-5 Cu / V (200Å) / Si / Ag / Si 200 25 MSA-6 Cu / V (200Å) / Si / Ag / Si / Ag / Si / Ag / Si / Ag 70 50

1M LiPF ₆ dissolved in a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) using lithium metal as a counter electrode and a reference electrode to measure the electrochemical characteristics of the anode thin film prepared as described above. Was used to prepare a lithium secondary battery.

Comparative Example 1

Using only the same silicon content as the total amount of silicon used in MSA-2 on top of the copper current collector, only a pure silicon thin film was deposited to a thickness of 300 Å to complete a negative electrode thin film. The negative thin film was used in the same manner as in Example 1 A lithium secondary battery was produced.

The cycle characteristics of the lithium secondary battery including the negative electrode thin film (sample name: MSA-2) of Example 1 and the negative electrode thin film of Comparative Example 1 were investigated, and the results are shown in FIG. 3. Here, the cycle characteristics are evaluated according to the method of charging and discharging 50 times or more in a range of 0.08 to 1.5V for lithium at a current density of 50 mA / cm 2.

Referring to FIG. 3, it can be seen that the negative electrode active material layer of Example 1 has much improved cycle characteristics than the silicon single layer of Comparative Example 1. In particular, the negative electrode active material layer of Example 1 maintained more than 95% of the initial capacity even after 50 cycles. As described above, when the silicon / silver multilayer thin film is used as the negative electrode active material layer, the deterioration of the active material due to the volume expansion and contraction of silicon is greatly reduced compared to the case of using the negative electrode active material layer made of pure silicon thin film, thereby greatly improving cycle characteristics.

In addition, the cycle characteristics of the lithium secondary battery using the multilayer anode thin films of the MSA-1, MSA-2, and MSA-4 structures of Example 1 were investigated, and the results are shown in FIG. 4. Here, the cycle characteristics were evaluated according to the method of charging and discharging 100 times or more by a constant current method in a range of 0.08 to 1.5V for lithium at a current density of 50 mA / cm 2. 4, the thinner the silicon layer, the better the charge / discharge cycle characteristics. Capacity reduction was observed after about 50 cycles in the MSA-4 structured anode thin film with a silicon layer thickness of 200 μs but repeated 100 times in the MSA-1 and MSA-2 structures with 70 μm and 100 μm thickness respectively. Little reduction in capacity occurred during charging and discharging.

Meanwhile, referring to FIGS. 3 and 4, irreversible capacity in the first cycle was observed.

In order to understand the cause of such irreversible capacity, the charge capacity, discharge capacity and irreversible capacity in the first cycle in the lithium secondary battery employing the multilayer thin film negative electrode of Example 1 are shown in FIGS. 5A and B. At this time, these characteristics were evaluated under the conditions of charging and discharging with respect to lithium at a current density of 50 mA / cm 2 in a range of 0.08 to 1.5V.

5A-B, the charge and discharge capacity in the first cycle was proportional to the amount of the silicon active material, but the irreversible capacity showed a constant value regardless of the amount of silicon and silver used as the active material. From these results, the irreversible capacity in the first cycle is estimated to be a side reaction at the interface with the electrolyte rather than the lithium inserted in the negative electrode active material during the discharging process during the discharging process, and irreversible due to the structural damage of the active material itself. It does not seem to be a dose.

In order to examine the cycle characteristics according to the thickness of the silver layer of Example 1, the cycle characteristics of the lithium secondary battery employing the anode thin films of the MSA-1 and MSA-6 structures were investigated, and the results are shown in FIG. 6. same. Both the MSA-1 and MSA-6 structures showed excellent cycle characteristics, but the thickness of the silver layer increased to 50 ms, which was somewhat slower than the structure with 25 cycles of capacity reduction. Approximately 95% of the dose was maintained.

Meanwhile, in order to compare the case where the uppermost layer of the anode active material layer is the silver layer and the silicon layer, the cycle characteristics of the lithium secondary battery using the multilayer thin films of the MSA-4 and MSA-5 structures of Examples were compared and measured. The result is as shown in FIG.

Referring to FIG. 7, when silicon is present in the uppermost layer of the negative electrode active material layer (MSA-5), the battery capacity is greater, and when silver is present in the uppermost layer of the negative electrode active material layer (MSA-4), The cycle characteristics were better than those exposed to this electrolyte (MSA-5).

This is because when the uppermost layer is a silver layer, cracking and loss of the active material due to volume expansion and contraction of silicon at the interface with the electrolyte are suppressed. From these results, when the silver layer is formed on the top of the negative electrode active material layer to fabricate a lithium secondary battery employing a solid electrolyte, it is expected to greatly improve the chemical and mechanical stability between the electrode and the electrolyte interface.

Example 2

Except for depositing 900-mm thick silicon-silver (Si _0.6 Ag _0.4 ) single layer having the laminated structure as shown in f of FIG. 2 by sputtering the silicon (Si), silver (Ag) and vanadium (V) targets with the cathode thin film And it carried out similarly to Example 1. At this time, in order to control the content of silicon and silver in a single layer, the rf power applied to the silicon target was fixed at 200W, and the direct current (dc) voltage applied to the silver target was adjusted.

Example 3

A negative electrode thin film was manufactured according to the same method as Example 1 except for using a nickel (Ni) target instead of a vanadium (V) target.

Example 4

The same procedure as in Example 1 was conducted except that the molybdenum (Mo) target was used instead of the vanadium (V) target.

Example 5

The same procedure as in Example 1 was conducted except that a copper (Cu) target was used instead of the vanadium (V) target.

The cycle characteristics of the lithium secondary battery employing the negative electrode thin film of Example 2-5 were investigated. Here, the cycle characteristics were evaluated according to a method of charging and discharging 50 times or more by a constant current method in a section of 0.12 to 1.5V for lithium at a current density of 50 mA / cm 2.

As a result of the evaluation, it was found that the cycle characteristics of the lithium secondary battery prepared in Example 2-5 were excellent. In particular, FIG. 8 is for the case of Example 2, with reference to this, a capacity of about 90% was maintained after 50 cycles at an initial charge capacity of about 32 mAh.

The negative electrode thin film of the present invention can greatly improve the cycle characteristics by suppressing the volume expansion and contraction of the silicon generated during the charge and discharge process. Therefore, by employing this thin film negative electrode, it is possible to manufacture a lithium secondary battery with a significant improvement in chemical and mechanical stability between the electrode and the electrolyte interface and improved life characteristics.

Although the present invention has been described with reference to the above embodiments, it is merely illustrative, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. .

Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims (10)

In the negative electrode thin film for a lithium secondary battery having a current collector and a negative electrode active material layer formed thereon, The negative electrode active material layer, A negative electrode thin film for a lithium secondary battery, characterized in that a multilayer thin film in which a silicon (Si) layer and a silver (Ag) layer are laminated. The buffer film of claim 1, wherein a buffer film of at least one member selected from the group consisting of vanadium (V), nickel (Ni), molybdenum (Mo), and copper (Cu) is formed between the current collector and the negative electrode active material layer. A negative electrode thin film for a lithium secondary battery, characterized in that. The negative electrode thin film for a lithium secondary battery according to claim 2, wherein the buffer film has a thickness of 50 to 250 kPa. The method of claim 1, wherein the silicon layer has a thickness of 50 to 250 kPa, The thickness of the silver layer is 10 to 70Å, the negative electrode thin film for lithium secondary batteries. The negative electrode thin film for a lithium secondary battery according to claim 1, wherein the silicon (Si) layer and the silver (Ag) layer are alternately formed. The negative electrode thin film for lithium secondary battery according to claim 5, wherein the silver (Ag) layer is formed between the silicon (Si) layers. The negative electrode thin film according to claim 1, wherein the uppermost layer of the multilayer thin film is made of silver (Ag). In the negative electrode thin film for a lithium secondary battery provided with an electrical power collector and the negative electrode active material layer formed in the upper part, The negative electrode active material layer, A negative electrode thin film for a lithium secondary battery, characterized in that consisting of a single layer containing silicon and silver. The negative electrode thin film of claim 8, wherein the single layer including silicon and silver has a mixing molar ratio of silicon (Si) and silver (Ag) of 7: 3 to 3: 7. 10. The method of claim 8, wherein a buffer film of at least one member selected from the group consisting of vanadium (V), nickel (Ni), molybdenum (Mo), and copper (Cu) is formed between the current collector and the negative electrode active material layer. A negative electrode thin film for a lithium secondary battery, characterized in that.