KR20020020007A - The fabrication method of the cathode grown by using the buffer layer for thin film battery - Google Patents

Abstract

PURPOSE: A method for preparing an anode for a thin film battery using a buffer layer is provided, to reduce the cracking due to the increase of thickness of a crystalline anode and to improve the capacity of a battery. CONSTITUTION: The method comprises the steps of forming a buffer layer(4) on a substrate(1); and forming a crystalline anode(5) on the buffer layer(4). Preferably the buffer layer and the crystalline anode are prepared by sputtering to allow the temperature of a substrate to be changed. The buffer layer is grown at a temperature of a room temperature to 500 deg.C; and by the thickness of 5 Angstrom to 1 micrometers per 1-60 min. The crystalline anode is grown at a temperature of 400-900 deg.C.

Description

The fabrication method of the cathode grown by using the buffer layer for thin film battery}

The present invention relates to a method for manufacturing a cathode for a thin film battery using a buffer layer, and more particularly, to a method for manufacturing a thin film battery capable of achieving high capacity.

The possibility of rechargeable thin film cells has long been anticipated, but only in 1983 was it first created by the Kanehori group. This group implemented a thin film battery using Li as an anode, TiS ₂ as an anode, and amorphous lithium phosphosilicate (Li _3.6 Si _0.6 P _0.4 O ₄ ) as an electrolyte, and obtained an open circuit voltage (OCV) of 2.5 V under full charge. . In addition, the Li / Li _3.6 Si _0.6 P _0.4 O ₄ / TiS ₂ thin film battery was capable of charging and discharging 2000 times at a current density of 16 mA / cm 2. At the same conference, the Levasseur group announced a Li / 1 μm lithium borosilicate / TiS ₂ thin film battery, and subsequently produced a Li / Li ₂ OB ₂ O ₃ -Li ₂ SO ₄ / titanium oxysulfide thin film battery. In this case, 50 charges and discharges were possible at a large current density of 62 mA / cm 2. In the same year, the Creus group announced a Li / amophous Li ₂ -SiS ₂ -P ₂ S ₅ / V ₂ O ₅ -TeO ₂ thin-film cell with an OCV of 3.1 V.

These thin film batteries commonly exhibited low charge and discharge characteristics due to the reaction between Li and the electrolyte. This problem could be significantly improved by using a LiI layer that could act as a buffer between these materials. By introducing this technique of protecting the electrolyte with the introduction of the LiI layer, Eveready Battery Co. manufactured Li / electrolyte / TiS ₂ thin film battery. In this case, even at a high current of 100 mA / cm 2, the charge / discharge characteristics of 10000 cycles were achieved without any change, and further, the initial potential of 98% was stably maintained at room temperature for almost two years.

However, the introduction of the LiI layer causes complexity in the battery manufacturing process and is stable only in the potential region of about 2.8 V, so it is difficult to expect the selection of the positive electrode or the development of a high energy, high rechargeable battery. By the end of 1992, the JBBates group of Oak Ridge National Laboratory developed Lithium phosphorus oxynitride (LiPON), which is stable in the potential window (5.5 V) and has excellent contact characteristics between the anodes, which can reduce charge and discharge characteristics and interface resistance. Using this, a thin film battery using various materials (Li _x Mn ₂ O ₄ , TiS ₂ , V ₂ O ₅ , LiCoO ₂ ) as a cathode material was implemented. Cathode materials are largely divided into crystalline (LiCoO ₂ , LiMn ₂ O _4, etc.) and amorphous (V ₂ O _5, etc.), and crystalline because amorphous cathode materials have a disadvantage of crystallization when using a thin film battery in a high temperature atmosphere. Use of positive electrode material is required. However, in this case, when a positive electrode having a thickness of 2 μm or more is grown by a conventional method, battery characteristics are deteriorated due to problems such as cracking due to stress concentration.

Accordingly, the present inventors have completed the present invention by growing a cathode material using a buffer layer to solve the deterioration characteristics of the thin film battery which may appear as the thickness of the cathode material becomes thick.

Accordingly, an object of the present invention is to manufacture a positive electrode structure consisting of a buffer layer and a crystalline positive electrode material using a sputtering device capable of controlling the substrate temperature for a thin film battery using a crystalline positive electrode material, thereby causing cracking due to an increase in the thickness of the existing positive electrode material. It is possible to solve the problems such as), from which it is possible to manufacture a thin film battery having a high capacity (capacity).

1 is a cross-sectional view of a thin film battery widely used in the past,

2 is a cross-sectional view of a thin film battery according to the present invention,

3 is a flowchart illustrating a manufacturing process of a thin film battery according to the present invention.

The components of the thin film battery are as follows.

1. Substrate

2. Anode current collector

3. Cathode Current Collector

4. Buffer layer

5. Crystalline Anode

6. Electrolyte

7. Cathode

In order to achieve the above object, according to the present invention, there is provided a method of manufacturing a thin film battery having a positive electrode structure composed of a buffer layer and a crystalline positive electrode material.

In the present invention, it is characterized by growing by changing the temperature of the substrate during the growth of the crystalline anode using a sputter (sputter) equipment. As an example of the crystalline cathode material, LiCoO ₂ is described. The conventional growth method is post-annealing for about 1 hour at a temperature of about 700 ° C. after growing LiCoO ₂ using a sputter at room temperature. The process of crystallization by using a process is used. However, this process method has a disadvantage that can not solve the problems such as cracks due to the stress concentration according to the thickness, as a result is a big problem in manufacturing a high capacity thin film battery.

Secondly, in the present invention, a buffer layer is used during the growth of the cathode material in order to manufacture a thin film battery having a high capacity, thereby minimizing degradation characteristics such as cracking due to an increase in thickness. The introduction of such a buffer layer is possible due to the property of changing the substrate temperature during growth of the anode material by sputtering. In addition, such a buffer layer may also have a side effect as a nucleation layer upon growth of crystalline anode material over the buffer layer.

Hereinafter, the present invention will be described in more detail with reference to Examples and Test Examples. However, these are provided only to explain the present invention in detail, and the present invention is not limited thereto.

(Example)

Hereinafter, the present invention will be described in more detail with reference to Examples.

Except for the growth method of the positive electrode material in manufacturing the thin film battery, all parts follow the material and the growth method which are widely used.

The substrate may use various materials such as Si and glass, and Pt, V, Co, Ta, Ti, etc. are used as current collectors of the anode and cathode.

The method of growing the anode material uses a sputtering device, and at this time, a buffer layer can be formed by simultaneously controlling the substrate temperature. In other words, using a sputter target of the anode material, first, a buffer layer was formed to a thickness of about 5 μm-1 μm for 1 minute-1 hour in a low temperature region of room temperature-500 ° C., and the temperature was successively high at 400-900 ° C. After raising to the area, the crystalline cathode material is grown over time. At this time, their thickness is adjusted according to variables such as time and partial pressure. Afterwards, the electrolyte and the cathode use conventional materials and growth methods.

The results are shown in FIG. 2, and the procedure is shown in FIG. 3.

1 is a cross-sectional view showing a structure of a conventional thin film battery, and no buffer layer is shown for a crystalline anode. This is because the conventional method of growing the crystalline anode material adopts a process of making an amorphous anode using a sputter at room temperature and then crystallizing it by post-annealing at about 700 ° C. for about 1 hour.

2 is a cross-sectional view of a thin film battery manufactured according to the present invention, showing that a buffer layer exists for a crystalline anode. This buffer layer is made by sputtering the sputter target of the anode material to a thickness of about 5 Å-1 탆 for 1 minute-1 hour at room temperature -500 ℃ substrate temperature using a sputtering equipment that can change the substrate temperature, Because of the low temperature process, the buffer layer has polycrystalline properties of amorphous or very small grains. Due to the structure of the buffer layer it is possible to solve the stress concentration that may appear during the deposition of the crystalline positive electrode material in the 400-900 ℃ high temperature region of the subsequent process, as a result it can minimize the battery degradation characteristics such as cracks. In addition, since it is composed of very small particles, it can also act as a nucleation layer (nucleation layer) when depositing the crystalline anode material, which can be expected to form a high quality anode thin film.

3 shows a process sequence for the thin film battery of FIG. 2. The current collectors 2 and 3 of the positive electrode and the negative electrode are deposited on the substrate 1 using a sputter or an evaporator, and the temperature of the substrate is changed thereon. By using a sputtering equipment capable of forming a buffer layer (4) for 1 minute-1 hour in the low temperature section of room temperature -500 ℃ to the target material material, and then to increase the temperature to a high temperature region of 400-900 ℃ After that, the crystalline cathode material 5 is grown using the anode material target. At this time, the thickness of the positive electrode material is controlled by using variables such as time and partial pressure. Finally, the electrolyte 6 and the cathode 7 parts are completed according to the existing materials and manufacturing methods to complete the present invention.

According to the positive electrode manufacturing method for a thin film battery using the buffer layer of the present invention, it is possible to minimize battery degradation characteristics such as cracks that may appear for a thick positive electrode 2 ㎛ or more compared to the conventional positive electrode manufacturing method, and as a result Manufacturing becomes possible. Through this, it can be used as a power source of an information communication device such as a terminal or a smart card.

Claims (5)

A method of manufacturing a cathode for a thin film battery using a buffer layer, wherein the buffer layer is formed on a substrate, and then a crystalline anode is formed thereon. The method of claim 1, wherein the buffer layer and the crystalline anode are formed using a sputtering apparatus capable of changing a temperature of a substrate. The method of claim 1, wherein the buffer layer is grown in a low temperature region of room temperature-500 ° C. The method of claim 1, wherein the crystalline anode is grown in a high temperature region of 400-900 ℃. 4. The method of claim 1 or 3, wherein the buffer layer is grown to a thickness of 5 Å to 1 탆 for 1 to 60 minutes.